WO2024120338A1 - Electrolyte solution comprising pyrosulfate-boron trifluoride composite lithium salt, and lithium-ion secondary battery - Google Patents

Electrolyte solution comprising pyrosulfate-boron trifluoride composite lithium salt, and lithium-ion secondary battery Download PDF

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WO2024120338A1
WO2024120338A1 PCT/CN2023/136137 CN2023136137W WO2024120338A1 WO 2024120338 A1 WO2024120338 A1 WO 2024120338A1 CN 2023136137 W CN2023136137 W CN 2023136137W WO 2024120338 A1 WO2024120338 A1 WO 2024120338A1
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additive
lithium
electrolyte
carbonate
battery
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PCT/CN2023/136137
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French (fr)
Chinese (zh)
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马国强
江依义
沈旻
马静
蒋志敏
徐宁
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浙江蓝天环保高科技股份有限公司
浙江省化工研究院有限公司
中化蓝天集团有限公司
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Priority claimed from CN202211583043.8A external-priority patent/CN118173885A/en
Application filed by 浙江蓝天环保高科技股份有限公司, 浙江省化工研究院有限公司, 中化蓝天集团有限公司 filed Critical 浙江蓝天环保高科技股份有限公司
Publication of WO2024120338A1 publication Critical patent/WO2024120338A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives

Definitions

  • the invention relates to the field of lithium ion battery electrolytes, and in particular to three electrolytes containing pyrosulfate boron trifluoride composite lithium salts and a lithium ion secondary battery.
  • lithium-ion batteries As one of the most important electrochemical energy storage devices, lithium-ion batteries have the advantages of high energy density, long cycle life, and environmental friendliness, and are widely used in the fields of power, digital, and new energy electric vehicles. As the energy density requirements for lithium batteries become higher and higher, the 4.3V operating voltage of commercial lithium-ion batteries is difficult to meet the requirements, but the increase in battery operating voltage often accelerates the oxidation and decomposition of conventional electrolytes, causing a series of side reactions such as battery performance deterioration and battery gas production, thereby causing the battery's electrochemical performance and safety performance to deteriorate.
  • sulfonate additives such as 1,3-propane sultone (PS) and 1,3-propylene sultone (PST) are recognized as good high-temperature additives for use under high voltage. They form a protective film under high voltage.
  • the protective film is insoluble in organic solvents and can allow lithium ions to freely deintercalate in the electrode without allowing solvent molecules to pass through, effectively preventing further reactions between the organic components of the electrolyte and the electrode and thus damaging the electrode.
  • the cyanide group of nitrile additives can combine with the active sites on the electrode surface.
  • LiDFOP fluorine-containing lithium oxalate salts
  • LiDFOB fluorine-containing lithium oxalate salts
  • LiDFOP fluorine-containing lithium oxalate salts
  • LiDFOB fluorine-containing lithium oxalate salts
  • LiDFOB can stabilize the NCM811 electrode interface, reduce polarization, and improve cycle performance.
  • LiDFOB containing oxalate structure is prone to produce gases such as CO2 during high-temperature and long-term storage, which can easily cause problems such as swelling of soft-pack batteries, reducing safety of use and battery life.
  • sulfate additives such as vinyl sulfate, DTD
  • fluorocarbonate additives such as fluoroethylene carbonate, FEC
  • DTD has poor thermal stability, is prone to discoloration during storage, and increases the acidity of the electrolyte.
  • FEC will produce HF during high-temperature storage, which has a negative effect on the high-voltage positive electrode and causes a sharp increase in gas production during high-temperature storage.
  • Pyrosulfate boron trifluoride composite lithium salt is a new electrolyte additive developed by Zhejiang Chemical Research Institute Co., Ltd. Its patent CN202211583064.X discloses that the additive can improve the battery's cycle performance, high-temperature storage performance, and low-temperature performance.
  • lithium salt additives despite the advantage of reducing impedance, still face the difficulty of poor high-voltage and high-temperature storage stability, especially in a high-nickel system or under ultra-high temperature conditions of 85°C, the gas production of the battery increases after high-temperature storage, which is a technical difficulty that is difficult to take into account in a high-voltage battery system while taking into account the technical requirements of low impedance.
  • the present invention proposes a high energy density battery electrolyte with balanced performance.
  • the synergistic effect between additives is further utilized to enhance the stability of the electrode-electrolyte interface and further improve the high and low temperature performance of the battery.
  • a high energy density battery electrolyte comprising a main lithium salt and a non-aqueous solvent, and the electrolyte further comprises:
  • a first additive wherein the first additive is selected from at least one of the following pyrosulfate boron trifluoride composite lithium salts, and the mass percentage content in the electrolyte is A%, and 0.1 ⁇ A ⁇ 15.0;
  • compound (I-1) accounts for at least 80% of the mass percentage of the first additive, and the rest is at least one of compounds (I-2), (I-3), (I-4), (I-5), and (I-6); preferably, compound (I-1) accounts for at least 90% of the mass percentage of the first additive;
  • the second additive b 1 is 1,3-propane sultone and/or vinyl sulfate, and the mass percentage of the second additive b 1 in the electrolyte is B%, and 0.1 ⁇ B ⁇ 5.0.
  • the contents of the first additive and the second additive b1 respectively satisfy: 0.2 ⁇ A ⁇ 3.0; 0.2 ⁇ B ⁇ 3.0.
  • the first additive of the present invention not only maintains the pyrosulfate compound itself to improve the oxidation resistance of the electrolyte, improve the normal/high temperature cycle performance and high temperature storage performance; the -SOB- group in its structure can also form a cross-linked network interface film containing S and B at the electrode interface during the battery's charge and discharge process.
  • the cross-linked network interface film contains more Li + conductive holes, has high ion conductivity, and improves the low temperature performance of the battery.
  • the single first additive is not ideal in terms of long cycle performance and gas production inhibition.
  • the second additive b1 of the present invention has both positive and negative electrode film - forming effects, and can form an interface film rich in inorganic salts such as Li2SO4 , Li2SO3 , and Li2S , which can significantly improve the high-temperature performance of the battery, especially the effect of inhibiting gas production is very good.
  • inorganic salts such as Li2SO4 , Li2SO3 , and Li2S in the interface film, the internal resistance increases and the low-temperature performance deteriorates.
  • the present invention considers that both the first additive and the second additive b1 are S-containing additives, which have a higher affinity for the film components formed in the electrode, and therefore the first additive and the second additive b1 are used together.
  • the first additive and the second additive b1 can form an organic-inorganic composite film rich in inorganic salt components such as Li2SO4 and Li2SO3 and -SOB- cross-linked network organic components.
  • the film is dense and firm, not only retains the high ion conductivity of the -SOB- cross-linked network organic components, and has excellent low-temperature performance, but also has the high-temperature storage performance of inorganic salts such as Li2SO4 and Li2SO3 (especially inhibiting gas production), and has significant high-temperature performance.
  • inorganic salts such as Li2SO4 and Li2SO3 (especially inhibiting gas production)
  • the improvement of high and low temperature performance is particularly obvious.
  • the film-forming performance of the electrolyte decreases and the high-temperature performance of the battery is not significantly improved; when the sum of the amounts of the first additive and the second additive b1 added is too large (such as A+B>4.0), the electrolyte film is thicker and the interface film ion conductivity is poor, and the low-temperature performance of the battery deteriorates.
  • the pyrosulfate boron trifluoride composite lithium salt of the present invention is obtained by the following steps:
  • lithium pyrosulfate reacts with boron trifluoride gas and/or a boron trifluoride complex to obtain a pyrosulfate boron trifluoride composite lithium salt reaction solution.
  • the reaction solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ⁇ -butyrolactone, ether, ethylene glycol dimethyl ether, acetonitrile, benzyl cyanide or propionitrile.
  • the reaction solvent is preferably a commonly used solvent in electrolyte, such as at least one of dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate.
  • the boron trifluoride reacted with lithium pyrosulfate can be either boron trifluoride gas or a boron trifluoride complex.
  • the boron trifluoride complex is selected from boron trifluoride ethyl ether complex, boron trifluoride glycol dimethyl ether complex, boron trifluoride dimethyl carbonate complex, boron trifluoride pyridine complex, boron trifluoride ethylamine complex, boron trifluoride butyl ether complex, boron trifluoride methyl ether complex, boron trifluoride acetonitrile complex, boron trifluoride piperidine complex, boron trifluoride phenol complex, boron trifluoride tetrahydrofuran complex, boron trifluoride At least one of dimethyl sulfide complex or boron trifluoride morpholine complex.
  • the boron trifluoride complex
  • the molar ratio of lithium pyrosulfate to boron trifluoride gas or boron trifluoride complex is (0.2-1.2):1, and the preferred molar ratio is (0.33-1.0):1.
  • the reaction temperature is 40-90°C, and the reaction time is 1-48 hours. Preferably, the reaction temperature is 50-70°C, and the reaction time is 3-12 hours.
  • the pyrosulfate boron trifluoride composite lithium salt reaction solution prepared above contains reaction solvent and unreacted boron trifluoride, so: atmospheric pressure distillation or reduced pressure distillation is used to remove the reaction solvent and unreacted boron trifluoride in the reaction solution to obtain the pyrosulfate boron trifluoride composite lithium salt.
  • the pyrosulfate boron trifluoride complex lithium salt obtained after distillation is a concentrated solution containing ⁇ 60% of the reaction solvent. If the reaction solvent is a common solvent in the electrolyte, the concentrated solution can be directly added to the electrolyte; if the reaction solvent is not a common solvent in the electrolyte, the electrolyte solvent is added and the reaction solvent is removed by normal pressure distillation or reduced pressure distillation before being added to the electrolyte.
  • the pyrosulfate boron trifluoride complex lithium salt obtained after distillation was confirmed by nuclear magnetic resonance.
  • the reaction temperature is low, the main product is a cyclic compound. As the reaction temperature rises, it is easier to form a chain compound.
  • the reaction temperature and reaction time are further increased at the same time, the polymer content in the composition gradually increases, and gradually forms a branched polymer.
  • the electrolyte of the present invention further comprises a third additive c1 , wherein the third additive c1 is vinylene carbonate, which is continuously consumed during the cycle process, and continuously forms an outer film rich in components such as PEO-like polymers to coat the organic-inorganic composite film formed by the first additive and the second additive b1 .
  • the outer film has excellent flexibility, does not reduce the ion conductivity of the organic-inorganic composite film, and can isolate the electrolyte to protect the organic-inorganic composite film.
  • the mass percentage of the third additive c1 in the electrolyte is C%, and 0.1 ⁇ C ⁇ 5.0, preferably 0.2 ⁇ C ⁇ 3.0.
  • the battery performance is more balanced, not only having good high and low temperature performance, but also further improving the long cycle stability.
  • the electrolyte also includes a basic additive, and the basic additive is selected from at least one of fluoroethylene carbonate, vinylethylene carbonate, tris(trimethylsilyl)phosphate, 1,3-propylene sultone, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, succinic anhydride, adiponitrile, cyclohexylbenzene, lithium difluorobis(oxalate)phosphate or lithium difluorobis(oxalate)borate, and the mass percentage of any one of the basic additives in the electrolyte is 0.1 to 5.0%.
  • the basic additive is selected from at least one of fluoroethylene carbonate, vinylethylene carbonate, tris(trimethylsilyl)phosphate, 1,3-propylene sultone, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, succinic anhydride, adiponitrile, cyclohexylbenzen
  • the basic additives are lithium bis(fluorosulfonyl)imide and lithium difluorophosphate, each accounting for 0.1% to 2.0% of the total mass of the electrolyte.
  • the basic additive is fluoroethylene carbonate, lithium bis(oxalato)difluorophosphate and tris(trimethylsilyl)borate, each accounting for 0.1% to 2.0% of the total mass of the electrolyte.
  • the main lithium salt of the present invention can be selected from lithium salts commonly used in electrolytes.
  • the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium tetrafluorooxalatophosphate, lithium trioxalatophosphate, and lithium difluorobisoxalatophosphate, and its molar concentration is 0.1 to 4.0 mol/L;
  • the non-aqueous solvent of the present invention can be selected from the commonly used solvents in the electrolyte.
  • the solvent is selected from at least one of C3-C6 carbonate or fluorocarbonate compounds, C3-C8 carboxylic acid ester or fluorocarboxylic acid ester compounds, sulfone compounds, and ether compounds.
  • the C3-C6 carbonate or fluorocarbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate;
  • the C3-C8 carboxylic acid ester or fluorocarboxylic acid ester compound is selected from at least one of ⁇ -butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, and propyl propionate;
  • the sulfone compound is selected from at least one of cyclopentane sulfoxide, dimethyl sulfoxide, dimethyl sulfone, and diethyl sulfone.
  • the ether compound is selected from
  • the present invention also provides a high energy density lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator, and any one of the high energy density battery electrolytes described above.
  • the positive electrode active material is selected from nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, lithium cobalt oxide material or lithium iron phosphate material.
  • the negative electrode active material is selected from graphite, silicon carbon, silicon dioxide, silicon, tin, metallic lithium or a composite material thereof.
  • the electrolyte of the present invention is particularly suitable for high energy density lithium ion secondary batteries with energy density of 250Wh/kg and above, and the electrochemical properties are balanced under high temperature and high voltage.
  • lithium ion secondary batteries with energy density below 250Wh/kg can also use the electrolyte of the present invention and maintain the corresponding performance.
  • an electrolyte having both high and low temperature performance under high voltage wherein the electrolyte comprises: a main lithium salt, a non-aqueous solvent and an additive.
  • the additive comprises:
  • the first additive comprises at least a pyrosulfate boron trifluoride composite lithium salt having a structure shown in the following formula (I-1):
  • the second additive b 2 is selected from the cyclic sulfonate compounds represented by the following formula (IIA) and/or (IIB):
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 are independently selected from hydrogen, C1-C3 alkyl or halogen, m and n are independently selected from 1, 2 or 3, and in each repeating unit, R 5 , R 6 , R 9 , R 10 may be selected from the same or different substituents;
  • the third additive c 2 is a lithium oxalate salt having a structure represented by the following formula (III):
  • R 11 and R 12 are independently selected from C1-C3 alkyl, C1-C3 haloalkyl or halogen
  • R 13 is selected from a direct bond, C1-C3 alkylene or halogenated C1-C3 alkylene
  • M is selected from a boron atom or a phosphorus atom
  • p is selected from 1 or 2;
  • the first additive, the second additive b2 and the third additive c2 account for a%, b% and c% of the total mass of the electrolyte respectively, and meet the following relationship: 0.2 ⁇ b+c ⁇ 4; 0.2 ⁇ b/c ⁇ 10; 0.07 ⁇ (b+c)/a ⁇ 20.
  • the addition amounts of the first additive, the second additive b2 and the third additive c2 satisfy the following relationship: 1 ⁇ b+c ⁇ 2.5; 0.5 ⁇ b/c ⁇ 7.5; 1 ⁇ (b+c)/a ⁇ 12.5.
  • the battery impedance can be significantly reduced, and the high temperature storage performance, high temperature cycle and low temperature performance can be improved.
  • the usage ratio of the three does not meet the above conditions, the lithium ion battery cannot simultaneously reduce the battery impedance and improve the high temperature storage performance, high temperature cycle performance and low temperature performance.
  • the sum of the contents of the second additive b2 and the third additive c2 is between 0.2 and 4, preferably between 1 and 2.5.
  • the sum of the contents of the two is too small (such as less than 0.2), the negative electrode film-forming effect is not significantly improved, and the high-temperature effect is not significantly improved; once the sum of the contents of the two is too large (such as greater than 4), the battery impedance will increase and the low-temperature performance will deteriorate.
  • the ratio of the content of the second additive b2 to that of the third additive c2 is between 0.2 and 10, preferably between 0.5 and 7.5.
  • the ratio of the content of the second additive b2 to that of the third additive c2 is too small (such as less than 0.2), the content of the third additive c2 is excessive, the negative electrode film-forming effect is not significantly improved, and the high-temperature performance is deteriorated;
  • the ratio of the content of the second additive b2 to that of the third additive c2 is too large (such as greater than 10)
  • the content of the second additive b2 is excessive, the negative electrode film is thicker, the battery impedance will increase, and the low-temperature performance will deteriorate.
  • the ratio of the sum of the contents of the second additive b2 and the third additive c2 to the first additive is between 0.07 and 20, preferably between 1 and 12.5. Once the ratio is too small (such as less than 0.07), the negative electrode film formation effect is not significantly improved and the high temperature performance is deteriorated; once the ratio is too large (such as greater than 20), the battery impedance will increase and the low temperature performance will be deteriorated.
  • the respective amounts of the first additive, the second additive b2 and the third additive must still meet the following requirements, that is:
  • the amount of the first additive added is too low (such as less than 0.2), the negative electrode film-forming effect is poor, the battery impedance increases, and the low-temperature performance decreases; if the amount of the first additive added is too high (such as higher than 3), the high-temperature performance of the battery decreases.
  • the amount of the second additive b2 added is too low (such as less than 0.1), the negative electrode film-forming effect is poor and the high-temperature performance of the battery is reduced; if the amount of the second additive b2 added is too high (such as higher than 2.5), the battery impedance increases and the low-temperature performance is reduced.
  • the amount of the third additive c2 added is too low (such as less than 0.1), the negative electrode film-forming effect is poor, the battery impedance increases, and the low-temperature performance decreases; if the amount of the third additive c2 added is too high (such as higher than 2.5), the high-temperature performance of the battery decreases.
  • the first additive contains at least 80 wt% of the pyrosulfate boron trifluoride complex lithium salt of the structure shown in formula (I-1).
  • the first additive contains 80-95 wt% of the pyrosulfate boron trifluoride complex lithium salt of the structure shown in formula (I-1), and the rest is at least one of compounds (I-2), (I-3), (I-4), (I-5) or (I-6).
  • R1 , R2 , R3 , R4 , R5 , R6 , R7 , R8 , R9 , R10 are independently selected from hydrogen, methyl, ethyl or halogen, m and n are independently selected from 1 or 2, and in each repeating unit, R5 , R6 , R9 , R10 are selected from the same or different substituents.
  • the second additive b2 is selected from at least one of the cyclic sulfonate compounds shown in the following structures:
  • R11 and R12 are independently selected from halogen, and R13 is selected from a direct bond, a methylene group or a fluoromethylene group; more preferably, the third additive c2 is selected from at least one of the lithium oxalate salts shown in the following structure:
  • the pyrosulfate boron trifluoride composite lithium salt, cyclic sulfonate compounds and oxalate lithium salt of the present invention are used in the electrolyte at the same time, and the three can play a synergistic role, and none of them can be missing.
  • the three can inhibit the reaction intensity of cyclic sulfonate compounds at about 2.35V to 2.40V, inhibit the reaction consumption of non-aqueous solvents such as EC at about 2.65V to 2.75V, and control the content of the three to achieve the regulation of the reaction intensity at the negative electrode, so that an organic-inorganic multi-component composite SEI film rich in inorganic salt components such as Li 2 SO 4 and Li 2 SO 3 and -SOB- cross-linked network organic components is formed at the negative electrode, which inhibits the performance degradation caused by the reaction of cyclic sulfonate compounds and/or oxalate lithium salts at the negative electrode, thereby reducing the battery impedance and improving the high-temperature storage performance, high-temperature cycle performance and low-temperature performance
  • the electrolyte of the present invention further comprises a fourth additive d2 , wherein the fourth additive d2 is vinylene carbonate, and the mass percentage content of the vinylene carbonate in the electrolyte is 0.1 to 5 wt%. The mass percentage in the electrolyte is 0.15-3.0wt%.
  • vinylene carbonate is added on the basis of the first additive, the second additive b2 and the third additive c2 .
  • Vinylene carbonate reacts continuously during the cycle to form a stable and dense polymer film on the electrode surface, thereby inhibiting the embedding of solvent molecules to destroy the electrode, thereby improving battery performance.
  • a basic additive is further added to the electrolyte of the present invention, wherein the basic additive is selected from at least one of a sulfate compound, a fluorinated carbonate compound or a fluorinated lithium salt compound, and the amount thereof accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte;
  • the sulfate compound is selected from at least one of vinyl sulfate, pentaerythritol bicyclic sulfate, 4,4'-disulfate or 4-methyl-vinyl sulfate;
  • the fluorinated carbonate compound is selected from at least one of fluoroethylene carbonate, difluoroethylene carbonate, and trifluoromethylpropylene carbonate;
  • the fluorine-containing lithium salt compound is selected from at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, lithium difluorooxalate borate, lithium trioxalate phosphate or the lithium salt represented by the following formula (IV), and the fluorine-containing lithium salt compound is different from the main lithium salt:
  • the basic additive adopts a combination of 0.2-1.0% by mass of lithium difluorophosphate, 0.2-1.0% by mass of lithium bis(fluorosulfonyl)imide and 0.2-0.8% by mass of ethylene fluorocarbonate, which can further optimize the positive and negative electrode-electrolyte interface film components and improve the low temperature discharge performance and rate charging performance of the battery.
  • the base additive is a combination of 0.2-3.0% by mass of lithium bis(fluorosulfonyl)imide and 0.1-1.0% by mass of ethylene carbonate, which can also improve the low temperature performance of the battery. Discharge performance and rate charging performance.
  • the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium tetrafluorooxalate phosphate, lithium trioxalate phosphate or lithium difluorobis(oxalate) phosphate, and its molar concentration is 0.1-4.0 mol/L; preferably, the main lithium salt is selected from lithium hexafluorophosphate and/or lithium bis(fluorosulfonyl imide), and its concentration in the electrolyte is 0.5-1.5 mol/L.
  • the non-aqueous solvent is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, ⁇ -butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, propyl propionate, cyclopentane, dimethyl sulfoxide, dimethyl sulfone, diethyl sulfone, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.
  • organic solvents are all complex multi-component systems.
  • cyclic carbonates have a high dielectric constant and can better dissolve lithium salts to provide high conductivity; linear carbonates and carboxylates can effectively adjust the viscosity and liquid range of the electrolyte.
  • linear carbonates and carboxylates can effectively adjust the viscosity and liquid range of the electrolyte.
  • the non-aqueous solvent of the present invention is selected from at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, fluoroethylene carbonate, ethyl acetate, ethyl propionate, propyl acetate, cyclopentane, dimethyl sulfone or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.
  • the present invention also provides a lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator, and any one of the above-mentioned electrolytes.
  • the active material of the positive electrode is selected from lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese iron phosphate, spinel lithium manganese oxide or lithium nickel manganese oxide
  • the active material of the negative electrode is selected from graphite and/or silicon negative electrode materials.
  • the ternary lithium nickel cobalt manganese oxide is selected from NCM523 (LiNi 0.5 Co 0.2 Mn 0.3 O 2 ), NCM622 (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ), NCM712 (LiNi 0.7 Co 0.1 Mn 0.2 O 2 ), NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) or NCM90505 (LiNi 0.9 Co 0.05 Mn 0.05 O 2 ).
  • the ternary lithium nickel cobalt manganese oxide is selected from NCM622 (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ) or NCM712 (LiNi 0.7 Co 0.1 Mn 0.2 O 2 ).
  • the operating voltage of the lithium ion secondary battery of the present invention is ⁇ 4.3V, preferably ⁇ 4.4V, such as 4.4V, 4.48V, 4.52V, etc.
  • an additive composition comprising a pyrosulfate boron trifluoride complex lithium salt and a nitrile compound and its application in electrolyte preparation and lithium-ion batteries are proposed.
  • the additive composition can further improve the high-temperature cycle stability and high-temperature storage stability of lithium-ion batteries under high voltage on the basis of maintaining the high and low temperature performance of the pyrosulfate boron trifluoride complex lithium salt, especially inhibit the gas expansion of the battery under high temperature conditions and reduce the initial impedance of the battery.
  • LiDFOB chemical name: lithium difluorooxalate borate
  • LiPO 2 F 2 chemical name: lithium difluorophosphate
  • PS chemical name: 1,3-propane sultone
  • HTCN chemical name: 1,3,6-hexanetrinitrile
  • ADN chemical name: adiponitrile
  • TCP chemical name: 1,2,3-tri(cyanoethoxy)propane
  • DFEA chemical name: 2,2-difluoroethyl acetate (CAS: 1550-44-3);
  • MMDS chemical name: methylene disulfonate
  • DTD chemical name: vinyl sulfate.
  • An electrolyte additive composition containing a novel lithium salt comprising:
  • the first additive comprises at least a novel lithium salt having a structure represented by the following formula (I-1):
  • the second additive b 3 is a nitrile compound having a structure selected from the following formula (IIC), wherein the nitrile compound is a polynitrile compound:
  • R14 , R15 , R16 are independently selected from a direct bond, oxygen, -R17- , -OR17- or -R18 - OR17- , wherein R17 , R18 are independently selected from C1-C5 alkylene, C2-C5 alkenylene, or C1-C5 alkylene or C2-C5 alkenylene substituted by C1-C3 alkyl or cyano;
  • the mass ratio of CN functional groups in the first additive and the second additive b3 is 0.03-4.0; preferably, the mass ratio of CN functional groups in the first additive and the second additive b3 is 0.08-1.0; more preferably, the mass ratio of CN functional groups in the first additive and the second additive b3 is 0.1-0.3.
  • the mass ratio of the CN functional groups in the first additive and the second additive b3 of the present invention refers to: the ratio of the mass content of the first additive in the electrolyte to the mass content of the CN functional groups in the second additive b3 in the electrolyte.
  • the mass content of the CN functional groups in the second additive b3 is calculated by the following formula:
  • n represents the number of different nitriles, 1 ⁇ n ⁇ 10
  • Mi is the relative molecular mass of different nitriles
  • ai is the number of CN functional groups of the i-th nitrile
  • 26 is the relative molecular mass of the CN functional group.
  • the second additive b3 contains only one nitrile compound, which contains 2 CN functional groups, then n is 1, the relative molecular mass of the nitrile compound is M1 , and the mass content of the CN functional group in the second additive b3 is 52/ M1 .
  • the second additive b3 contains two different nitrile compounds, the first nitrile compound contains 2 CN functional groups, and the relative molecular mass is M1 , and the second nitrile compound contains 3 CN functional groups, and the relative molecular mass is M2 , then n is 2,
  • a composition of nitrile compounds is usually composed of 2-4 second additives b3 , and different nitrile compounds have different numbers of CN functional groups. Therefore, using the mass content of CN functional groups instead of the mass content of nitrile compounds can more reasonably express the synergistic effect of the first additive and the second additive b3 .
  • the first additive can form a stable passivation film at the negative electrode interface before the second additive b3 when it is first formed, inhibit the second additive b3 (polycyano additive) from damaging the negative electrode interface, and reduce the negative electrode impedance.
  • the second additive b3 can also be promoted to rely on its strong coordination ability of the cyano (CN) functional group to combine with the active sites on the positive electrode surface (such as high-valent metal ions such as nickel/cobalt/manganese, etc.), play a role in shielding the active ions on the positive electrode surface and reducing the decomposition of the electrode to the electrolyte; and the nitrogen triple bond energy in the cyano (CN) functional group in the second additive b3 is very high, not easily oxidized, and has strong stability on the high-voltage positive electrode.
  • the active sites on the positive electrode surface such as high-valent metal ions such as nickel/cobalt/manganese, etc.
  • the flatulence of the lithium ion battery under high-temperature storage is inhibited, the negative electrode impedance is reduced, the dynamic performance of the battery is improved, and the long-cycle stability of the lithium ion battery is guaranteed.
  • the first additive contains at least 80 wt% or more of the novel lithium salt having the structure represented by formula (I-1). Preferably, the first additive contains 80.0 to 95.0 wt% of the novel lithium salt having the structure represented by formula (I-1). salt, and the rest are at least one of compounds (I-2), (I-3), (I-4), (I-5) or (I-6).
  • R1 , R2 , and R3 are independently selected from a direct bond, oxygen, -R4- , -OR4- or -R5 - OR4- , wherein R4 and R5 are independently selected from C1-C3 alkylene, C2-C3 alkenylene, or C1-C3 alkylene, C2-C3 alkenylene substituted by C1-C3 alkyl or cyano.
  • the second additive b3 is selected from at least one of the nitrile compounds shown in the following structures:
  • the present invention also provides a method for preparing an electrolyte, the method comprising: adding a main lithium salt to a non-aqueous solvent until the main lithium salt accounts for 8 to 20 wt% of the total mass of the electrolyte, and then adding any of the above-mentioned additive compositions to obtain an electrolyte, and making the first additive account for 0.01 to 5.0 wt% of the total mass of the electrolyte, and the second additive b3 accounts for 0.1 to 10 wt% of the total mass of the electrolyte; further preferably, making the first additive account for 0.01 to 2.0 wt% of the total mass of the electrolyte, and the second additive b3 accounts for 1 to 8 wt% of the total mass of the electrolyte; more preferably, making the first additive account for 0.1 to 1.0 wt% of the total mass of the electrolyte, and the second additive b3 accounts for 2 to 6 wt% of the total mass of the electrolyte.
  • the non-aqueous solvent is selected from a mixture of cyclic carbonates and linear carbonates and/or linear carboxylates.
  • the cyclic carbonate is selected from at least one of ethylene carbonate, propylene carbonate or fluoroethylene carbonate;
  • the linear carbonate is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate or methyl trifluoroethyl carbonate;
  • the linear carboxylic acid ester is selected from at least one of ethyl acetate, ethyl propionate, propyl propionate, 2,2-difluoroethyl acetate or 2,2,2-trifluoroethyl acetate, and the amount of any non-aqueous solvent accounts for 0.1 to 50 wt% of the total mass of the electrolyte;
  • the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.
  • a third additive c 3 is further added, wherein the third additive c 3 is selected from at least one of the sulfur-oxygen double bond compounds shown in the following structures, and the amount used accounts for 0.5-5.0 wt% of the total mass of the electrolyte:
  • the third additive c3 containing a sulfur-oxygen double bond can form a film on the surface of the positive and negative electrodes.
  • the formed alkyl lithium sulfate containing tetravalent or hexavalent high-valent states can improve the oxidation resistance of the positive electrode interface and has high lithium ion conductivity. It cooperates with the above-mentioned first additive to form an organic-inorganic composite SEI film.
  • the mass ratio of the CN functional groups in the first additive and the second additive b3 is lower than 1.0, the introduction of the third additive c3 can more effectively inhibit the damage of the second additive b3 to the negative electrode interface film, thereby improving the storage and cycle performance of the battery.
  • the amount of the third additive c3 is 1.0-4.0 wt % of the total mass of the electrolyte.
  • a basic additive is further added, and the basic additive is selected from at least one of fluoroethylene carbonate, vinylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium difluorobisoxalatophosphate, tris(trimethylsilyl)phosphate, and tris(trimethylsilyl)borate, and any addition amount accounts for 0.1 to 2.0 wt% of the total mass of the electrolyte.
  • a fourth additive d3 is further added, and the fourth additive d3 is selected from at least one of tetravinylsilane, 2,4,6-tri(allyloxy)-1,3,5-triazine, 1,3,5-triallyl isocyanurate, 1,3-dioxane, and 1,4-dioxane, and any addition amount accounts for 0.1-2.0wt% of the total mass of the electrolyte, which is used for positive electrode film formation, inhibiting gas production, and improving the high-temperature storage performance of the battery at 85°C.
  • the present invention also provides a lithium ion secondary battery, comprising a positive electrode sheet, a negative electrode sheet and a separator.
  • the lithium ion secondary battery is prepared by the following method:
  • the positive electrode sheet, the separator and the negative electrode sheet are wound together into a roll core, sealed with an aluminum-plastic film and then baked, and then the electrolyte prepared by any of the above-mentioned preparation methods is injected into it, and a lithium-ion secondary battery is obtained after standing, forming, volume separation and aging.
  • the active material of the positive electrode plate of the lithium secondary battery is selected from lithium cobalt oxide, lithium nickel manganese oxide, lithium-rich manganese base, lithium manganese oxide, lithium iron phosphate, lithium iron manganese phosphate or LiNi x Co y Mn z L (1-xyz) O 2 , wherein L is Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, W or Fe, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, 0.5 ⁇ x+y+z ⁇ 1, and the active material of the negative electrode plate is selected from graphite, silicon carbon or silicon oxygen material.
  • the active material of the positive electrode plate at least comprises LiCoO 2 . That is, the active material of the positive electrode plate is LiCoO 2 , or a composite material of LiCoO 2 and LiNi x Co y Mn z L (1-xyz) O 2 .
  • the electrolyte prepared by using the additive composition of the present invention is suitable for lithium ion secondary batteries with a cut-off voltage of ⁇ 4.35V, and is also suitable for lithium ion secondary batteries with a cut-off voltage of ⁇ 4.45V, and is more suitable for lithium ion secondary batteries with a cut-off voltage of ⁇ 4.48V.
  • the advantageous electrolyte formula of the present invention when it is used in a high voltage environment with a cut-off voltage of 4.48V, the high temperature cycle stability and high temperature storage stability of the battery are still maintained. Qualitative and low temperature performance.
  • the electrolyte additive of the present invention participates in the construction of the electrode/electrolyte interface during the battery formation process, so that in the electrolyte liquid of the lithium ion secondary battery, the first additive accounts for 0.01-2.0wt% of the total mass of the electrolyte liquid, and the second additive b3 accounts for 0.1-6.0wt% of the total mass of the electrolyte liquid.
  • the third additive c3 accounts for 0.1-3.0 wt% of the total mass of the electrolyte liquid
  • the fourth additive d3 accounts for 0.02-1.5 wt% of the total mass of the electrolyte liquid.
  • the present invention has the following beneficial effects:
  • the electrolyte of the present invention enhances the stability of the electrode-electrolyte interface, takes into account the high and low temperature performance of the battery, is suitable for high energy density battery systems, and maintains a balance of various electrochemical properties at high temperature and high voltage.
  • the electrolyte of the first aspect of the present invention exerts the synergistic effect of the first additive and the second additive b1 to form an organic-inorganic composite membrane rich in inorganic salt components such as Li2SO4 and Li2SO3 and -SOB- cross-linked network organic components, which can improve the high and low temperature performance of the battery; and further through the synergy of the third additive c1 , an outer membrane rich in PEO-like polymers is formed outside the organic-inorganic composite membrane.
  • the double-layer membrane has good ion conductivity and the function of isolating the electrolyte, so that the battery has excellent cycle performance, high temperature performance and gas production inhibition effect, while taking into account low temperature performance.
  • the electrolyte of the second aspect of the present invention uses a pyrosulfate boron trifluoride composite lithium salt, a cyclic sulfonate compound and an oxalate lithium salt in combination, and by regulating the three additives within a specific content ratio range to fully produce a synergistic effect, obtain a suitable film-forming potential, inhibit the reaction intensity of the cyclic sulfonate compound at about 2.35V to 2.40V, inhibit the reaction consumption of non-aqueous solvents such as EC at about 2.65V to 2.75V, and regulate the reaction intensity at the negative electrode by controlling the content of the three, forming a multi-component composite SEI film at the negative electrode, thereby reducing the battery impedance, improving the low-temperature performance, and improving the high-temperature storage performance and high-temperature cycle performance.
  • the electrolyte of the third aspect of the present invention through the CN functional groups in the first additive and the second additive b3 , in a specific ratio and specific respective contents, the two work synergistically, which not only inhibits the flatulence of the lithium-ion battery under high-temperature storage, but also reduces the negative electrode impedance, improves the dynamic performance of the battery, and ensures the long-cycle stability of the lithium-ion battery.
  • the inhibitory effect of the additive composition on high-temperature storage gas generation is significantly better than that of nitrile compounds and lithium oxalate salt additives such as LiDFOB and LiDFOP. Combination of additives.
  • FIG1 is a dQ/dV curve of Example 2.1, Comparative Example 2.5, Comparative Example 2.6 and Comparative Example 2.7 of the present invention.
  • a high energy density battery electrolyte and application thereof comprising a pyrosulfate boron trifluoride composite lithium salt, 1,3-propane sultone and/or vinyl sulfate.
  • This preparation example provides a method for preparing a pyrosulfate boron trifluoride composite lithium salt, which specifically includes the following steps:
  • the first additive, the second additive b1 and the third additive c1 are quantitatively added and mixed evenly to form an electrolyte:
  • lithium bis(fluorosulfonyl)imide LiFSI
  • LiDFP lithium difluorophosphate
  • 1# lithium salt 1,3-propane sultone
  • PS 1,3-propane sultone
  • VC vinylene carbonate
  • the lithium ion battery electrolytes of the above embodiments and comparative examples were respectively made into lithium ion power batteries with a soft package capacity of 1000 mAh.
  • the lithium ion power batteries included a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and battery auxiliary materials.
  • the positive electrode active material was LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), and the negative electrode active material was graphite.
  • the preparation process is as follows: the positive electrode sheet, the separator and the negative electrode sheet are wound together into a core, which is sealed with an aluminum-plastic film and then baked so that the moisture content of the electrode meets the requirements. After baking, the battery cell is injected with electrolyte, and the finished soft-pack battery cell is obtained through the steps of standing, forming, capacity separation and aging.
  • the above lithium-ion batteries are tested for various performances, including:
  • Capacity retention rate discharge capacity in the last week/discharge capacity in the first week*100%.
  • Volume expansion ratio (volume after storage - volume before storage) / volume before storage * 100%.
  • Low temperature discharge rate low temperature discharge capacity / normal temperature discharge capacity * 100%.
  • the battery At room temperature, the battery is charged at a constant current with a specified current to the charging cut-off voltage, and then charged at a constant voltage until the current drops to 0.1C.
  • the total charging capacity and the charging capacity in the constant current section are recorded, and the battery constant current charging ratio is calculated as follows:
  • Constant current charging ratio constant current charging capacity/total charging capacity*100%.
  • Comparing Example 1.1 and Comparative Example 1.2 and Comparative Example 1.4 in Table 3 above it can be seen that the composition with the first additive and the second additive b1 has excellent low-temperature performance and more significant high-temperature performance than the composition with the first additive alone or the second additive b1 alone.
  • the reason is that in the process of combining the two, an organic-inorganic composite film can be formed.
  • the film is dense and strong, not only retains the high ion conductivity of the -SOB- cross-linked network organic component and excellent low-temperature performance; it also has the high-temperature storage performance of inorganic salts such as Li 2 SO 4 and Li 2 SO 3 (especially suppressing gas generation) and has outstanding high temperature performance.
  • Example 1.13, Example 1.14 and Example 1.1 in Table 3, and comparing Example 1.11 and Example 1.2 it can be seen that by adding the third additive c 1 to the combination of the first additive and the second additive b 1 , the battery not only has good high and low temperature performance, but also further improves long cycle stability. The reason is that the third additive c 1 is continuously consumed during the cycle, and an outer film rich in PEO-like polymers and other components is continuously formed to cover the organic-inorganic composite film, thereby protecting the organic-inorganic composite film.
  • the second aspect of the present invention provides an electrolyte formula comprising a boron trifluoride composite lithium salt, a cyclic sulfonate compound and a lithium oxalate salt, which is particularly suitable for a high-voltage battery system using a nickel cobalt manganese oxide ternary material as a positive electrode, especially a high-voltage battery system ⁇ 4.3V.
  • the electrolyte formula of the present invention can better show its advantages under the high voltage conditions of a nickel cobalt manganese oxide ternary battery. Therefore, the embodiment of the second aspect of the present invention prepares the electrolyte and tests the corresponding performance under the premise of the basic electrolyte formula of the ternary system.
  • the types of the first additive include the following:
  • the first additive A1 is composed of 95 wt% of compound I-1 and 5 wt% of compound I-2;
  • the first additive A2 is composed of 90 wt% of compound I-1, 6 wt% of compound I-2 and 4 wt% of compound I-3;
  • the first additive A3 consists of 85 wt% of compound I-1, 7 wt% of compound I-2, 5 wt% of compound I-3 and 3 wt% of compound I-4.
  • the first additive, the second additive b2 and the third additive c2 are quantitatively added and mixed evenly to form an electrolyte:
  • Vinylene carbonate (VC), the first additive, the second additive b2 and the third additive c2 are added to the basic electrolyte 1 according to the data in Table 6 below, and mixed evenly to form an electrolyte:
  • Electrolyte Formula 4 Note: After the dosage of additives is adjusted, only the dosage of solvent in the basic electrolyte is adjusted, and the distribution ratio of each group in the solvent remains unchanged.
  • the lithium ion battery electrolytes of the above embodiments and comparative examples were respectively made into lithium ion power batteries with a soft package capacity of 1000 mAh.
  • the lithium ion power batteries comprised positive electrode sheets, negative electrode sheets, separators, electrolytes and battery auxiliary materials.
  • the positive electrode active material was lithium nickel cobalt manganese oxide NCM712 (LiNi 0.7 Co 0.1 Mn 0.2 O 2 ), and the negative electrode active material was graphite.
  • the preparation process is as follows: the positive electrode sheet, separator and negative electrode sheet are wound together into a core, sealed with an aluminum-plastic film and then baked so that the moisture content of the electrode meets the requirements. After baking, the battery cell is injected with electrolyte, and the finished soft-pack battery cell is obtained through standing, forming, aging, capacity separation and other processes.
  • the prepared lithium-ion battery is tested for various properties, including:
  • FIG1 shows the formation dQ/dV curves of Example 1 and Comparative Examples 5, 6, and 7. It can be seen from the formation dQ/dV curve of Comparative Example 6 that the first additive and the second additive b2 are used in the electrolyte at the same time, and the ternary (NCM712)/graphite full battery film forming potential is about 2.35V ⁇ 2.40V and 2.65 ⁇ 2.70V, which participate in the negative electrode film forming reaction and affect the SEI interface film composition.
  • NCM712 ternary/graphite full battery film forming potential
  • FIG. 1 also shows the first additive, the second additive b2 and the third additive in Example 2.1 of the present invention.
  • the first additive, the second additive b 2 and the third additive c 2 have a synergistic effect when used together.
  • the interaction of the three combined inhibits the reaction intensity of the second additive b 2 at about 2.35V ⁇ 2.40V, and inhibits the reaction consumption of non-aqueous solvents such as EC at about 2.65V ⁇ 2.75V.
  • the reaction amount of each additive in the negative electrode is regulated by controlling the content of the three, and the composition of the negative electrode SEI film is adjusted to form a multi-component composite SEI film.
  • the battery was charged at a constant current of 1C to the charge cut-off voltage (4.4V), and then charged at a constant voltage until the current dropped to 0.05C, and then placed in a 60°C constant temperature oven for 56 days.
  • the negative electrode film-forming effect is not significantly improved, and the high-temperature storage and high-temperature cycle performance of the battery are deteriorated; if the sum of the contents of the two is too large, the battery impedance increases and the low-temperature discharge performance is deteriorated.
  • the ratio of the contents of the second additive b 2 and the third additive c 2 is too small, the negative electrode film-forming effect is not significantly improved, and the high-temperature storage and high-temperature cycle performance of the battery are deteriorated; if the ratio of the contents of the second additive b 2 and the third additive c 2 is too large, the battery impedance increases and the low-temperature discharge performance is deteriorated. If the ratio of the sum of the contents of the second additive b2 and the third additive c2 to the first additive is too small, the negative electrode film formation effect is not significantly improved, and the high temperature storage and high temperature cycle performance of the battery are reduced; if the ratio is too large, the battery impedance increases and the low temperature discharge performance is reduced.
  • Example 2.2 By comparing Example 2.2 with Examples 2.11 to 2.21, it can be seen that compounds A1, A2, A3, compounds II-1, II-2, II-3, II-4, II-5, II-6 and compounds III-1, III-2, III-3, III-4, III-5 all have the functions of the additives they represent and can be used interchangeably.
  • Example 2.2 According to Tables 8 and 9 above, by comparing Example 2.2 with Examples 2.22-2.24, it can be seen that the first additive, the second additive b2 and the third additive c2 are further used in combination with vinylene carbonate to further reduce the initial impedance and improve the high and low temperature performance of the battery.
  • Example 2.2 examples 2.22-2.24 and Examples 2.25-2.28
  • the first additive, the second additive b2 and the third additive c2 are further used in combination with vinyl sulfate, vinylene carbonate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide and fluoroethylene carbonate to further reduce the initial impedance and improve the high and low temperature performance of the battery.
  • a third aspect of the present invention provides an electrolyte solution comprising a pyrosulfate boron trifluoride lithium complex salt and a nitrile compound.
  • the types of the first additive include the following:
  • the first additive A1 contains 95 wt% of compound I-1 and 5 wt% of compound I-2;
  • the first additive A2 contains 90 wt % of compound I-1, 6 wt % of compound I-2 and 4 wt % of compound I-3.
  • argon water content ⁇ 5ppm, oxygen content ⁇ 10ppm
  • ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) were mixed in a mass ratio of 1.5:1.5:3:1:1 to form an organic solvent, and LiPF6 was added in a mass percentage of 14% based on the total mass of the electrolyte for use as a basic electrolyte M.
  • the first additive, the second additive b3 and other additives are quantitatively added to the above-mentioned basic electrolyte M, and mixed evenly to form an electrolyte, wherein the mass ratio of the CN functional groups in the first additive and the second additive b3 is recorded as a, and the mass content of the CN functional groups in the second additive b3 is recorded as CN%.
  • the specific electrolyte formula is shown in Table 11 below:
  • DFEA 2,2-difluoroethyl acetate
  • the electrolyte formula adopted in the present invention solves the problem of poor interface stability of high-voltage positive electrode electrolyte by using the first additive and the second additive b3 together, and at the same time improves the compatibility of nitrile compounds with the negative electrode interface, and is suitable for lithium cobalt oxide/graphite, lithium cobalt oxide/silicon carbon, ternary/graphite, ternary/silicon carbon, lithium manganese iron phosphate/graphite and other systems.
  • This embodiment only selects the lithium cobalt oxide/graphite system for performance testing.
  • the lithium ion battery electrolytes of the above examples and comparative examples were respectively loaded into soft-pack lithium ion batteries with a capacity of 1000 mAh.
  • the lithium ion power battery comprises a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and battery auxiliary materials.
  • the positive electrode active material is LiCoO 2
  • the negative electrode active material is graphite.
  • the preparation process is as follows: the positive electrode sheet, the separator and the negative electrode sheet are wound together into a core, which is sealed with an aluminum-plastic film and then baked so that the moisture content of the electrode meets the requirements. After baking, the battery cell is injected with electrolyte, and the finished soft-pack battery cell is obtained through the steps of standing, forming, capacity separation and aging.
  • the above lithium-ion batteries are tested for various performances, including:
  • Capacity retention rate discharge capacity in the last week/discharge capacity in the first week*100%.
  • the battery was charged at a constant current of 1C to the charge cut-off voltage, and then charged at a constant voltage until the current dropped to 0.1C, and then stored in a constant temperature oven at 85°C for 12 hours.
  • the volume change rate and capacity recovery rate before and after high-temperature storage were recorded.
  • Low temperature capacity retention rate discharge capacity at low temperature / discharge capacity in the first week * 100%.
  • the battery capacity was adjusted to 50% SOC (state of charge) with a standard charging current, and the internal resistance (m ⁇ ) at a frequency of 1KHz was tested at the fixed ear position of the lithium battery after capacity division using a Japanese Hioki internal resistance meter, which was recorded as the initial ACR impedance (AC internal resistance).
  • Example 3.2 by comparing Example 3.2 with Comparative Examples 3.1 to 3.2, it can be seen that the combined use of the first additive and the second additive b3 , compared with the use of either alone, can inhibit the gas expansion of the battery cell after storage at ultra-high temperature of 85°C for 12 hours in a lithium cobalt oxide high voltage system and improve the capacity recovery rate of the battery, while effectively improving the -20°C low temperature discharge performance of the battery cell and the high voltage and high temperature cycle performance.
  • the mass ratio of CN functional groups in the first additive and the second additive b3 is preferably 0.1 to 0.3.
  • a third additive c3 containing a sulfur-oxygen double bond is further added, which can form a film on the surface of the positive and negative electrodes, and the formed alkyl lithium sulfate containing a high valence state such as tetravalent or hexavalent can improve the oxidation resistance of the positive electrode interface, and at the same time has high lithium ion conductivity.
  • the third additive c3 and the first additive act synergistically to form an organic-inorganic composite SEI film. Especially when the mass ratio of the CN functional groups in the first additive and the second additive b3 is lower than 1.0, the introduction of the third additive c3 can more effectively inhibit the damage of CN to the negative electrode interface and improve the storage and cycle performance of the battery.
  • the use of a fluorinated solvent (DFEA) based on the combined use of the first additive, the second additive b 3 and the third additive c 3 can further improve the low-temperature discharge performance of the battery while taking into account the cycle performance.
  • DFEA has the risk of deteriorating gas production during high-temperature storage.
  • TVS gas production inhibitor
  • the electrolyte in the formed (0% SOC) lithium cobalt oxide battery cell was obtained by centrifugation, acidified with dilute nitric acid, filtered, and the filtrate was taken.
  • the main components and contents in the electrolyte were measured by gas chromatography-mass spectrometry. The test results are as follows:
  • Example 3.1 According to the results in Table 14 above, in the absence of the third additive PS, the first additive and the second additive b3 in Example 3.1 are gradually consumed as the battery is formed and cycled. It is speculated that the first additive and the second additive b3 participate in the modification of the positive and negative electrode surfaces, respectively, to improve the cycle stability of the high-voltage battery. Compared with Example 3.1, in Example 3.19, the content of the second additive b3 is increased to 3% and the third additive PS is introduced. The consumption of the first additive during the cycle is reduced. It is speculated that the second additive b3 and the third additive c3 have a synergistic effect with the first additive, which improves the stability of the electrode interface. Compared with Example 3.1, it is more helpful to improve the cycle performance of the full battery.

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Abstract

Disclosed in the present invention are an electrolyte solution comprising a pyrosulfate-boron trifluoride composite lithium salt and a lithium-ion secondary battery. The electrolyte solution specifically comprises three types of electrolyte solution comprising a pyrosulfate-boron trifluoride composite lithium salt: (1) a high-energy-density battery electrolyte solution comprising a pyrosulfate-boron trifluoride composite lithium salt, 1,3-propane sultone and/or ethylene sulfate; (2) an electrolyte solution comprising a pyrosulfate-boron trifluoride composite lithium salt, a cyclic sulfonate compound and a lithium oxalate salt; and (3) an electrolyte solution comprising a pyrosulfate-boron trifluoride composite lithium salt and a nitrile compound. In the present invention, on the basis of a pyrosulfate-boron trifluoride composite lithium salt having both high and low temperature performance, functional additives, such as a second additive and a third additive, are combined, and the synergistic effect among the additives is used, whereby the electrode-electrolyte solution interface stability is enhanced, the impedance of a battery is further reduced in a high-temperature and high-voltage environment of a high-energy-density battery system, the gas production of a battery during high-temperature storage is inhibited, and the high-temperature performance, the low-temperature performance and the cycling performance of a battery are further improved.

Description

含焦硫酸根三氟化硼复合锂盐的电解液及锂离子二次电池Electrolyte containing pyrosulfate boron trifluoride composite lithium salt and lithium ion secondary battery 技术领域Technical Field
本发明涉及锂离子电池电解液领域，特别涉及三种含焦硫酸根三氟化硼复合锂盐的电解液及锂离子二次电池。The invention relates to the field of lithium ion battery electrolytes, and in particular to three electrolytes containing pyrosulfate boron trifluoride composite lithium salts and a lithium ion secondary battery.
背景技术Background technique
锂离子电池作为当前最重要的电化学储能器件之一，具有能量密度高、循环寿命长、环境友好等优点，在动力、数码、新能源电动汽车等领域获得广泛应用。随着锂电池能量密度要求越来越高，商用锂离子电池4.3V的工作电压难以满足要求，但电池工作电压的提升往往会加速常规电解液的氧化分解，引发电池性能恶化和电池产气等一系列的副反应，从而导致电池电化学性能和安全性能变差。As one of the most important electrochemical energy storage devices, lithium-ion batteries have the advantages of high energy density, long cycle life, and environmental friendliness, and are widely used in the fields of power, digital, and new energy electric vehicles. As the energy density requirements for lithium batteries become higher and higher, the 4.3V operating voltage of commercial lithium-ion batteries is difficult to meet the requirements, but the increase in battery operating voltage often accelerates the oxidation and decomposition of conventional electrolytes, causing a series of side reactions such as battery performance deterioration and battery gas production, thereby causing the battery's electrochemical performance and safety performance to deteriorate.
目前，诸如1,3-丙烷磺酸内酯(PS)、1,3-丙烯磺酸内酯(PST)等磺酸酯类添加剂是公认较好的高电压下使用的高温型添加剂，其在高电压下会形成保护膜，该保护膜难溶于有机溶剂，能够允许锂离子在电极自由脱嵌而不允许溶剂分子通过，有效阻止电解液有机成分与电极之间的进一步反应进而对电极造成破坏。腈类添加剂的氰基可以和电极表面的活性位点结合，其具有较强的配位能力，能够减少电极对电解液的分解作用并掩蔽正极表面活性离子，提升电解液在高电压工况下的抗氧化性。然而，磺酸酯类或腈类添加剂会增大电池阻抗，电池低温性能差，用于功率型和低温性能要求较高的电池时存在严重困难。At present, sulfonate additives such as 1,3-propane sultone (PS) and 1,3-propylene sultone (PST) are recognized as good high-temperature additives for use under high voltage. They form a protective film under high voltage. The protective film is insoluble in organic solvents and can allow lithium ions to freely deintercalate in the electrode without allowing solvent molecules to pass through, effectively preventing further reactions between the organic components of the electrolyte and the electrode and thus damaging the electrode. The cyanide group of nitrile additives can combine with the active sites on the electrode surface. It has a strong coordination ability, which can reduce the decomposition effect of the electrode on the electrolyte and mask the active ions on the positive electrode surface, thereby improving the antioxidant properties of the electrolyte under high voltage conditions. However, sulfonate or nitrile additives will increase the battery impedance, and the battery has poor low-temperature performance. There are serious difficulties in using them in power-type batteries with high low-temperature performance requirements.
又如LiDFOP、LiDFOB等含氟草酸锂盐，其具有降低阻抗效果、低温倍率性能较好，但在高电压下的高温性能往往较差。专利CN103943884A虽然公开了草酸根锂盐作为添加剂能够提高电解液的高温性能和低温性能，但并未说明其制得的锂离子电池在高电压体系下仍然能维持优异的高温性能和低温性能。Qingyu Dong等人(ACS Appl.Energy Mater.2020,3,695-704)公开了LiDFOB能够稳定NCM811电极界面、降低极化、改善循环性能，然而，含有草酸盐结构的LiDFOB在高温长周期存储中容易产生CO2等气体，易引起软包电池鼓胀等问题，降低了使用安全性和电池寿命。 Another example is fluorine-containing lithium oxalate salts such as LiDFOP and LiDFOB, which have the effect of reducing impedance and good low-temperature rate performance, but the high-temperature performance under high voltage is often poor. Although patent CN103943884A discloses that lithium oxalate salts can improve the high-temperature and low-temperature performance of electrolytes as additives, it does not explain that the lithium-ion batteries produced therefrom can still maintain excellent high-temperature and low-temperature performance under high-voltage systems. Qingyu Dong et al. (ACS Appl. Energy Mater. 2020, 3, 695-704) disclose that LiDFOB can stabilize the NCM811 electrode interface, reduce polarization, and improve cycle performance. However, LiDFOB containing oxalate structure is prone to produce gases such as CO2 during high-temperature and long-term storage, which can easily cause problems such as swelling of soft-pack batteries, reducing safety of use and battery life.
此外，电解液行业中也常采用硫酸酯类添加剂(如硫酸乙烯酯，DTD)、氟代碳酸酯类添加剂(如氟代碳酸乙烯酯，FEC)来改善高电压下电池的性能，但DTD热稳定性差，存储过程中容易变色，且增加了电解液酸度；FEC在以六氟磷酸锂为主盐的电解液中，在高温存储过程中会产生HF，对高电压正极带来负面效应，使得高温存储产气急剧增加。In addition, sulfate additives (such as vinyl sulfate, DTD) and fluorocarbonate additives (such as fluoroethylene carbonate, FEC) are often used in the electrolyte industry to improve the performance of batteries under high voltage. However, DTD has poor thermal stability, is prone to discoloration during storage, and increases the acidity of the electrolyte. In an electrolyte with lithium hexafluorophosphate as the main salt, FEC will produce HF during high-temperature storage, which has a negative effect on the high-voltage positive electrode and causes a sharp increase in gas production during high-temperature storage.
焦硫酸根三氟化硼复合锂盐是浙江省化工研究院有限公司开发的一款新型电解液添加剂，其专利CN202211583064.X公开了该添加剂能改善电池的循环性能、高温存储性能以及低温性能。然而，在高电压工作环境中，尤其是正极工作电压≥4.3V，锂盐类添加剂尽管有降低阻抗的优点，但仍面临着高电压高温存储稳定性差的难点，尤其是在高镍体系或者在85℃超高温工况下，电池高温存储后产气增加，这是高电压电池体系在兼顾低阻抗的技术需求下，难以兼顾的技术难点。Pyrosulfate boron trifluoride composite lithium salt is a new electrolyte additive developed by Zhejiang Chemical Research Institute Co., Ltd. Its patent CN202211583064.X discloses that the additive can improve the battery's cycle performance, high-temperature storage performance, and low-temperature performance. However, in a high-voltage working environment, especially when the positive electrode working voltage is ≥4.3V, lithium salt additives, despite the advantage of reducing impedance, still face the difficulty of poor high-voltage and high-temperature storage stability, especially in a high-nickel system or under ultra-high temperature conditions of 85°C, the gas production of the battery increases after high-temperature storage, which is a technical difficulty that is difficult to take into account in a high-voltage battery system while taking into account the technical requirements of low impedance.
因此，通过结合高低温性能综合型添加剂，以及各类不同功能种类的添加剂，继续深入研究从而开发出更多稳定性好，在高电压下甚至超高电压下仍然具有较低的电池阻抗，高温性能、低温性能和充放电倍率性能等各项综合性能均显著的电解液配方，是当前非常重要的一项研究课题。Therefore, it is a very important research topic at present to continue in-depth research to develop more electrolyte formulas with good stability, low battery impedance at high voltage or even ultra-high voltage, and significant comprehensive performance such as high temperature performance, low temperature performance, and charge and discharge rate performance by combining comprehensive additives with high and low temperature performance, as well as various types of additives with different functions.
发明内容Summary of the invention
为了解决上述技术问题，本发明提出一种性能均衡的高能量密度电池电解液，在兼具高低温性能的焦硫酸根三氟化硼复合锂盐的基础上，进一步利用添加剂间协同效应，强化电极-电解液界面的稳定性，进一步改善电池的高低温性能。In order to solve the above technical problems, the present invention proposes a high energy density battery electrolyte with balanced performance. On the basis of pyrosulfate boron trifluoride composite lithium salt with both high and low temperature performance, the synergistic effect between additives is further utilized to enhance the stability of the electrode-electrolyte interface and further improve the high and low temperature performance of the battery.
本发明的目的是通过以下技术方案实现的：The objective of the present invention is achieved through the following technical solutions:
本发明的第一方面，提出一种高能量密度电池电解液，包括主锂盐、非水溶剂，所述电解液还包括：In a first aspect of the present invention, a high energy density battery electrolyte is provided, comprising a main lithium salt and a non-aqueous solvent, and the electrolyte further comprises:
第一添加剂，所述第一添加剂选自下述焦硫酸根三氟化硼复合锂盐中的至少一种，在电解液中的质量百分含量为A％，且0.1≤A≤15.0；

A first additive, wherein the first additive is selected from at least one of the following pyrosulfate boron trifluoride composite lithium salts, and the mass percentage content in the electrolyte is A%, and 0.1≤A≤15.0;

且，化合物(I-1)占第一添加剂质量百分含量的至少80％以上，其余为化合物(I-2)、(I-3)、(I-4)、(I-5)、(I-6)中的至少一种；优选地，化合物(I-1)占第一添加剂质量百分含量的至少90％以上；Moreover, compound (I-1) accounts for at least 80% of the mass percentage of the first additive, and the rest is at least one of compounds (I-2), (I-3), (I-4), (I-5), and (I-6); preferably, compound (I-1) accounts for at least 90% of the mass percentage of the first additive;
第二添加剂b1，所述第二添加剂b1为1,3-丙磺酸内酯和/或硫酸乙烯酯，在电解液中的质量百分含量为B％，且0.1≤B≤5.0。The second additive b 1 is 1,3-propane sultone and/or vinyl sulfate, and the mass percentage of the second additive b 1 in the electrolyte is B%, and 0.1≤B≤5.0.
进一步地，第一添加剂和第二添加剂b1的含量分别满足：
0.2≤A≤3.0；
0.2≤B≤3.0。Furthermore, the contents of the first additive and the second additive b1 respectively satisfy:
0.2≤A≤3.0;
0.2≤B≤3.0.
进一步地，1.0≤A+B≤4.0。Further, 1.0≤A+B≤4.0.
本发明所述第一添加剂不仅保持焦硫酸化合物本身所具备的提高电解液耐氧化特性，改善常/高温循环性能和高温存储性能；其结构中的-S-O-B-基团还能在电池的充放电过程中在电极界面形成含S、B的交联网状界面膜，该交联网状的界面膜含有更多的导Li+孔洞，离子电导率高，提升电池低温性能。但单一的第一添加剂，其长循环性能和抑制产气效果不够理想。 The first additive of the present invention not only maintains the pyrosulfate compound itself to improve the oxidation resistance of the electrolyte, improve the normal/high temperature cycle performance and high temperature storage performance; the -SOB- group in its structure can also form a cross-linked network interface film containing S and B at the electrode interface during the battery's charge and discharge process. The cross-linked network interface film contains more Li + conductive holes, has high ion conductivity, and improves the low temperature performance of the battery. However, the single first additive is not ideal in terms of long cycle performance and gas production inhibition.
本发明第二添加剂b1兼具正负极成膜作用，可形成富含Li2SO4、Li2SO3、Li2S等无机盐的界面膜，能够显著提高电池高温性能，尤其是抑制产气效果非常好。然而同样由于该界面膜中Li2SO4、Li2SO3、Li2S等无机盐的存在，使得内阻增加，低温性能劣化。The second additive b1 of the present invention has both positive and negative electrode film - forming effects, and can form an interface film rich in inorganic salts such as Li2SO4 , Li2SO3 , and Li2S , which can significantly improve the high-temperature performance of the battery, especially the effect of inhibiting gas production is very good. However, due to the presence of inorganic salts such as Li2SO4 , Li2SO3 , and Li2S in the interface film, the internal resistance increases and the low-temperature performance deteriorates.
本发明考虑到第一添加剂和第二添加剂b1均为含S添加剂，其在电极形成的膜组分更具亲和性，因而将第一添加剂和第二添加剂b1联用，在两者联用过程中，惊喜的发现，第一添加剂和第二添加剂b1能够形成富含Li2SO4、Li2SO3等无机盐成分和-S-O-B-交联网状的有机成分的有机-无机复合膜，该膜致密且牢固，不仅保有-S-O-B-交联网状有机成分的高离子导通性，低温性能优异，还具备Li2SO4、Li2SO3等无机盐的高温存储性能(尤其是抑制产气)，高温性能显著。尤其当第一添加剂、第二添加剂b1的添加质量满足：1.0≤A+B≤4.0时，高低温性能改善尤为明显。当第一添加剂和第二添加剂b1添加量之和过小(如A+B＜1.0)，电解液成膜性能下降、电池高温性能提升不明显；当第一添加剂和第二添加剂b1添加量之和过大(如A+B＞4.0)，电解液成膜较厚且界面膜离子导通性差，电池低温性能劣化。The present invention considers that both the first additive and the second additive b1 are S-containing additives, which have a higher affinity for the film components formed in the electrode, and therefore the first additive and the second additive b1 are used together. In the process of using the two together, it is surprisingly found that the first additive and the second additive b1 can form an organic-inorganic composite film rich in inorganic salt components such as Li2SO4 and Li2SO3 and -SOB- cross-linked network organic components. The film is dense and firm, not only retains the high ion conductivity of the -SOB- cross-linked network organic components, and has excellent low-temperature performance, but also has the high-temperature storage performance of inorganic salts such as Li2SO4 and Li2SO3 (especially inhibiting gas production), and has significant high-temperature performance. In particular , when the addition mass of the first additive and the second additive b1 meets: 1.0≤A+B≤4.0, the improvement of high and low temperature performance is particularly obvious. When the sum of the amounts of the first additive and the second additive b1 added is too small (such as A+B＜1.0), the film-forming performance of the electrolyte decreases and the high-temperature performance of the battery is not significantly improved; when the sum of the amounts of the first additive and the second additive b1 added is too large (such as A+B＞4.0), the electrolyte film is thicker and the interface film ion conductivity is poor, and the low-temperature performance of the battery deteriorates.
本发明所述焦硫酸根三氟化硼复合锂盐通过以下步骤获得：The pyrosulfate boron trifluoride composite lithium salt of the present invention is obtained by the following steps:
在反应溶剂中，焦硫酸锂与三氟化硼气体和/或三氟化硼络合物反应获得焦硫酸根三氟化硼复合锂盐反应液。In a reaction solvent, lithium pyrosulfate reacts with boron trifluoride gas and/or a boron trifluoride complex to obtain a pyrosulfate boron trifluoride composite lithium salt reaction solution.
所述反应溶剂选自碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、乙酸甲酯、乙酸乙酯、丙酸甲酯、γ-丁内酯、***、乙二醇二甲醚、乙腈、苯乙腈或丙腈中的至少一种。考虑到焦硫酸根三氟化硼复合锂盐在电解液中的应用，所述反应溶剂优选为电解液中常用溶剂，如碳酸二甲酯、碳酸甲乙酯或碳酸二乙酯中的至少一种。The reaction solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, methyl propionate, γ-butyrolactone, ether, ethylene glycol dimethyl ether, acetonitrile, benzyl cyanide or propionitrile. Considering the application of pyrosulfate boron trifluoride composite lithium salt in electrolyte, the reaction solvent is preferably a commonly used solvent in electrolyte, such as at least one of dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate.
与焦硫酸锂反应的三氟化硼既可以是三氟化硼气体，也可以是三氟化硼络合物。任选地，所述三氟化硼络合物选自三氟化硼***络合物、三氟化硼乙二醇二甲醚络合物、三氟化硼碳酸二甲酯络合物、三氟化硼吡啶络合物、三氟化硼乙胺络合物、三氟化硼丁醚络合物、三氟化硼甲醚络合物、三氟化硼乙腈络合物、三氟化硼哌啶络合物、三氟化硼苯酚络合物、三氟化硼四氢呋喃络合物、三氟化硼 二甲基硫醚络合物或三氟化硼吗啉络合物中的至少一种。优选地，所述三氟化硼络合物为三氟化硼碳酸二甲酯络合物、三氟化硼***络合物或三氟化硼乙腈络合物中的至少一种。The boron trifluoride reacted with lithium pyrosulfate can be either boron trifluoride gas or a boron trifluoride complex. Optionally, the boron trifluoride complex is selected from boron trifluoride ethyl ether complex, boron trifluoride glycol dimethyl ether complex, boron trifluoride dimethyl carbonate complex, boron trifluoride pyridine complex, boron trifluoride ethylamine complex, boron trifluoride butyl ether complex, boron trifluoride methyl ether complex, boron trifluoride acetonitrile complex, boron trifluoride piperidine complex, boron trifluoride phenol complex, boron trifluoride tetrahydrofuran complex, boron trifluoride At least one of dimethyl sulfide complex or boron trifluoride morpholine complex. Preferably, the boron trifluoride complex is at least one of boron trifluoride dimethyl carbonate complex, boron trifluoride ethyl ether complex or boron trifluoride acetonitrile complex.
在反应过程中，焦硫酸锂与三氟化硼气体或三氟化硼络合物的摩尔配比为(0.2～1.2)：1，优选摩尔配比为(0.33～1.0)：1。During the reaction, the molar ratio of lithium pyrosulfate to boron trifluoride gas or boron trifluoride complex is (0.2-1.2):1, and the preferred molar ratio is (0.33-1.0):1.
反应温度为40～90℃，反应时间为1～48h。优选反应温度为50～70℃，反应时间为3～12h。The reaction temperature is 40-90°C, and the reaction time is 1-48 hours. Preferably, the reaction temperature is 50-70°C, and the reaction time is 3-12 hours.
上述制备获得的焦硫酸根三氟化硼复合锂盐反应液中包含反应溶剂和未反应三氟化硼，故：采用常压蒸馏或减压蒸馏除去所述反应液中的反应溶剂和未反应的三氟化硼获得焦硫酸根三氟化硼复合锂盐。The pyrosulfate boron trifluoride composite lithium salt reaction solution prepared above contains reaction solvent and unreacted boron trifluoride, so: atmospheric pressure distillation or reduced pressure distillation is used to remove the reaction solvent and unreacted boron trifluoride in the reaction solution to obtain the pyrosulfate boron trifluoride composite lithium salt.
由于溶剂化作用，蒸馏不能完全除去反应溶液，故蒸馏后获得的焦硫酸根三氟化硼复合锂盐为包含≤60％反应溶剂的浓缩液。若反应溶剂为电解液中常用溶剂，可直接将所述浓缩液添加到电解液中；若所述反应溶剂并非电解液中常用溶剂，则加入电解液溶剂并经常压蒸馏或减压蒸馏除去反应溶剂后加入到电解液中。Due to the solvation effect, distillation cannot completely remove the reaction solution, so the pyrosulfate boron trifluoride complex lithium salt obtained after distillation is a concentrated solution containing ≤60% of the reaction solvent. If the reaction solvent is a common solvent in the electrolyte, the concentrated solution can be directly added to the electrolyte; if the reaction solvent is not a common solvent in the electrolyte, the electrolyte solvent is added and the reaction solvent is removed by normal pressure distillation or reduced pressure distillation before being added to the electrolyte.
将蒸馏后获得的焦硫酸根三氟化硼复合锂盐进行核磁确认，反应温度较低时，主要产物为环状化合物，随着反应温度的上升，更容易形成链状化合物，当反应温度以及反应时间同时进一步增加，组合物中多聚物含量逐步升高，并逐渐形成带支链的多聚物。The pyrosulfate boron trifluoride complex lithium salt obtained after distillation was confirmed by nuclear magnetic resonance. When the reaction temperature is low, the main product is a cyclic compound. As the reaction temperature rises, it is easier to form a chain compound. When the reaction temperature and reaction time are further increased at the same time, the polymer content in the composition gradually increases, and gradually forms a branched polymer.
在高能量密度电池的持续工作过程中，尤其是高温、高电压下，界面膜中的有机成膜会发生溶解，导致电解液与电极表面高活性位点直接接触而发生持续的副分解反应，进而导致电池循环、存储等各方面性能的恶化。因此，本发明的电解液还包括第三添加剂c1，所述第三添加剂c1为碳酸亚乙烯酯，在循环过程中持续消耗，不断形成富含类PEO聚合物等成分的外膜包覆在第一添加剂和第二添加剂b1形成的有机-无机复合膜外，该外膜柔韧性极佳，不会降低有机-无机复合膜的离子导通性，又能够隔离电解液，起到保护有机-无机复合膜的作用。During the continuous operation of the high energy density battery, especially at high temperature and high voltage, the organic film in the interface film will dissolve, resulting in direct contact between the electrolyte and the high active sites on the electrode surface, resulting in continuous secondary decomposition reactions, which in turn leads to deterioration of battery performance in various aspects such as battery cycle and storage. Therefore, the electrolyte of the present invention further comprises a third additive c1 , wherein the third additive c1 is vinylene carbonate, which is continuously consumed during the cycle process, and continuously forms an outer film rich in components such as PEO-like polymers to coat the organic-inorganic composite film formed by the first additive and the second additive b1 . The outer film has excellent flexibility, does not reduce the ion conductivity of the organic-inorganic composite film, and can isolate the electrolyte to protect the organic-inorganic composite film.
所述第三添加剂c1在电解液中的质量百分含量为C％，且0.1≤C≤5.0，优选0.2≤C≤3.0。 The mass percentage of the third additive c1 in the electrolyte is C%, and 0.1≤C≤5.0, preferably 0.2≤C≤3.0.
进一步地，当第一添加剂、第二添加剂b1、第三添加剂c1的添加质量满足：0.25≤C/(A+B)≤4.0时，电池性能更加均衡，不仅具有良好的高低温性能，而且长循环稳定性得到进一步提升。Furthermore, when the added mass of the first additive, the second additive b 1 , and the third additive c 1 satisfies: 0.25≤C/(A+B)≤4.0, the battery performance is more balanced, not only having good high and low temperature performance, but also further improving the long cycle stability.
为了进一步提升电池各项综合性能，所述电解液还包括基础添加剂，所述基础添加剂选自氟代碳酸乙烯酯、乙烯基碳酸乙烯酯、三(三甲基硅基)磷酸酯、1,3-丙烯磺内酯、二氟磷酸锂、双氟磺酰亚胺锂、丁二酸酐、已二腈、环己基苯、双草酸二氟磷酸锂或二氟草酸硼酸锂中的至少一种，任意一种基础添加剂在电解液中的质量百分含量为0.1～5.0％。In order to further improve the comprehensive performance of the battery, the electrolyte also includes a basic additive, and the basic additive is selected from at least one of fluoroethylene carbonate, vinylethylene carbonate, tris(trimethylsilyl)phosphate, 1,3-propylene sultone, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, succinic anhydride, adiponitrile, cyclohexylbenzene, lithium difluorobis(oxalate)phosphate or lithium difluorobis(oxalate)borate, and the mass percentage of any one of the basic additives in the electrolyte is 0.1 to 5.0%.
在一种实施方式中，所述基础添加剂为双氟磺酰亚胺锂和二氟磷酸锂，均占电解液总质量0.1％～2.0％，通过与第一添加剂、第二添加剂b1、第三添加剂c1的联用，能提升锂离子电池常温、高温循环性能及高温存储性能，同时进一步改善电池的低温放电性能。In one embodiment, the basic additives are lithium bis(fluorosulfonyl)imide and lithium difluorophosphate, each accounting for 0.1% to 2.0% of the total mass of the electrolyte. By combining with the first additive, the second additive b1 , and the third additive c1 , the normal temperature and high temperature cycle performance and high temperature storage performance of the lithium ion battery can be improved, and the low temperature discharge performance of the battery can be further improved.
在另一种实施方式中，所述基础添加剂为氟代碳酸乙烯酯、双草酸二氟磷酸锂和三(三甲基硅基)硼酸酯，均占电解液总质量0.1％～2.0％，通过与第一添加剂、第二添加剂b1、第三添加剂c1的联用，能提升锂离子电池常温、高温循环性能及高温存储性能，同时进一步提升锂离子电池的倍率性能。In another embodiment, the basic additive is fluoroethylene carbonate, lithium bis(oxalato)difluorophosphate and tris(trimethylsilyl)borate, each accounting for 0.1% to 2.0% of the total mass of the electrolyte. By combining with the first additive, the second additive b1 and the third additive c1 , the normal temperature and high temperature cycle performance and high temperature storage performance of the lithium ion battery can be improved, and the rate performance of the lithium ion battery can be further improved.
本发明主锂盐选自电解液中常用锂盐即可。优选地，所述主锂盐选自六氟磷酸锂、四氟硼酸锂、六氟砷酸锂、高氯酸锂、双草酸硼酸锂、二氟草酸硼酸锂、双氟磺酰亚胺锂、双三氟甲基磺酰亚胺锂、四氟草酸磷酸锂、三草酸磷酸锂、二氟双草酸磷酸锂中的至少一种，且其摩尔浓度为0.1～4.0mol/L；The main lithium salt of the present invention can be selected from lithium salts commonly used in electrolytes. Preferably, the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium tetrafluorooxalatophosphate, lithium trioxalatophosphate, and lithium difluorobisoxalatophosphate, and its molar concentration is 0.1 to 4.0 mol/L;
本发明所述非水溶剂选自电解液中常用溶剂即可。优选地，所述溶剂选自选自C3～C6碳酸酯或氟代碳酸酯类化合物、C3～C8羧酸酯或氟代羧酸酯类化合物、砜类化合物、醚类化合物中的至少一种。进一步地，所述C3～C6碳酸酯或氟代碳酸酯类化合物选自碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯中的至少一种；所述C3～C8羧酸酯或氟代羧酸酯类化合物选自γ-丁内酯、乙酸甲酯、丙酸甲酯、丁酸甲酯、乙酸乙酯、丙酸乙酯、丁酸乙酯、乙酸丙酯、丙酸丙酯中的至少一种；所述砜类化合物选自环丁砜、二甲基亚砜、二甲基砜、二乙基砜中的至少 一种；所述醚类化合物选自三甘醇二甲醚和/或四甘醇二甲醚。The non-aqueous solvent of the present invention can be selected from the commonly used solvents in the electrolyte. Preferably, the solvent is selected from at least one of C3-C6 carbonate or fluorocarbonate compounds, C3-C8 carboxylic acid ester or fluorocarboxylic acid ester compounds, sulfone compounds, and ether compounds. Further, the C3-C6 carbonate or fluorocarbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; the C3-C8 carboxylic acid ester or fluorocarboxylic acid ester compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, and propyl propionate; the sulfone compound is selected from at least one of cyclopentane sulfoxide, dimethyl sulfoxide, dimethyl sulfone, and diethyl sulfone. One: the ether compound is selected from triethylene glycol dimethyl ether and/or tetraethylene glycol dimethyl ether.
本发明还提供一种高能量密度锂离子二次电池，包括正极、负极、隔膜，还包括上述任一所述的高能量密度电池电解液。The present invention also provides a high energy density lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator, and any one of the high energy density battery electrolytes described above.
所述正极活性材料选自镍钴锰三元材料、镍钴铝三元材料、钴酸锂材料或磷酸铁锂材料。The positive electrode active material is selected from nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, lithium cobalt oxide material or lithium iron phosphate material.
所述负极活性材料选自石墨、硅碳、氧化亚硅、硅、锡、金属锂或其复合材料材料。The negative electrode active material is selected from graphite, silicon carbon, silicon dioxide, silicon, tin, metallic lithium or a composite material thereof.
将本发明所述电解液尤其适用于能量密度250Wh/kg及以上的高能量密度锂离子二次电池，在高温高电压下，各项电化学性能均衡。当然地，低于250Wh/kg能量密度的锂离子二次电池也能使用本发明所述电解液，同样能保持相应的性能。The electrolyte of the present invention is particularly suitable for high energy density lithium ion secondary batteries with energy density of 250Wh/kg and above, and the electrochemical properties are balanced under high temperature and high voltage. Of course, lithium ion secondary batteries with energy density below 250Wh/kg can also use the electrolyte of the present invention and maintain the corresponding performance.
本发明的第二方面，提出一种高电压下兼顾高低温性能的电解液，所述电解液包括：主锂盐、非水溶剂和添加剂，具体地，所述添加剂包括：In a second aspect of the present invention, an electrolyte having both high and low temperature performance under high voltage is provided, wherein the electrolyte comprises: a main lithium salt, a non-aqueous solvent and an additive. Specifically, the additive comprises:
第一添加剂，所述第一添加剂至少包括下式(I-1)所示结构的焦硫酸根三氟化硼复合锂盐：
The first additive comprises at least a pyrosulfate boron trifluoride composite lithium salt having a structure shown in the following formula (I-1):
第二添加剂b2，所述第二添加剂b2选自下式(IIA)和/或(IIB)所示结构的环状磺酸酯类化合物：
The second additive b 2 is selected from the cyclic sulfonate compounds represented by the following formula (IIA) and/or (IIB):
式中，R1、R2、R3、R4、R5、R6、R7、R8、R9、R10独立地选自氢、C1-C3烷基或卤素，m、n独立地选自1、2或3，且每个重复单元中，R5、R6、R9、R10 可以选自相同或不同的取代基；In the formula, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 are independently selected from hydrogen, C1-C3 alkyl or halogen, m and n are independently selected from 1, 2 or 3, and in each repeating unit, R 5 , R 6 , R 9 , R 10 may be selected from the same or different substituents;
第三添加剂c2，所述第三添加剂c2为下式(III)所示结构的草酸根锂盐：
The third additive c 2 is a lithium oxalate salt having a structure represented by the following formula (III):
式(III)中，R11、R12独立地选自C1-C3烷基、C1-C3卤代烷基或卤素，R13选自直连键、C1-C3亚烷基或卤代C1-C3亚烷基，M选自硼原子或磷原子，p选自1或2；In formula (III), R 11 and R 12 are independently selected from C1-C3 alkyl, C1-C3 haloalkyl or halogen, R 13 is selected from a direct bond, C1-C3 alkylene or halogenated C1-C3 alkylene, M is selected from a boron atom or a phosphorus atom, and p is selected from 1 or 2;
所述第一添加剂、第二添加剂b2和第三添加剂c2分别占电解液总质量的a％、b％与c％，且符合下述关系式：
0.2≤b+c≤4；
0.2≤b/c≤10；
0.07≤(b+c)/a≤20。The first additive, the second additive b2 and the third additive c2 account for a%, b% and c% of the total mass of the electrolyte respectively, and meet the following relationship:
0.2≤b+c≤4;
0.2≤b/c≤10;
0.07≤(b+c)/a≤20.
优选地，所述第一添加剂、第二添加剂b2和第三添加剂c2的添加量满足下述关系式：
1≤b+c≤2.5；
0.5≤b/c≤7.5；
1≤(b+c)/a≤12.5。Preferably, the addition amounts of the first additive, the second additive b2 and the third additive c2 satisfy the following relationship:
1≤b+c≤2.5;
0.5≤b/c≤7.5;
1≤(b+c)/a≤12.5.
本发明电解液中，通过第一添加剂、第二添加剂b2和第三添加剂c2的联用，并通过调整三者的用量比例，可显著降低电池阻抗，提升高温存储性能、高温循环和低温性能。当三者比例用量不满足上述条件时，锂离子电池无法同时兼顾降低电池阻抗，提升高温存储性能、高温循环性能和低温性能。In the electrolyte of the present invention, by using the first additive, the second additive b2 and the third additive c2 together, and by adjusting the usage ratio of the three, the battery impedance can be significantly reduced, and the high temperature storage performance, high temperature cycle and low temperature performance can be improved. When the usage ratio of the three does not meet the above conditions, the lithium ion battery cannot simultaneously reduce the battery impedance and improve the high temperature storage performance, high temperature cycle performance and low temperature performance.
具体地，本发明电解液中，第二添加剂b2和第三添加剂c2的含量之和在0.2～4之间，优选1～2.5之间，一旦两者含量之和过小(如小于0.2)，负极成膜效果改善不明显，高温效果改善不明显；一旦两者含量之和过大(如大于4)，则会增加电池阻抗，劣化低温性能。 Specifically, in the electrolyte of the present invention, the sum of the contents of the second additive b2 and the third additive c2 is between 0.2 and 4, preferably between 1 and 2.5. Once the sum of the contents of the two is too small (such as less than 0.2), the negative electrode film-forming effect is not significantly improved, and the high-temperature effect is not significantly improved; once the sum of the contents of the two is too large (such as greater than 4), the battery impedance will increase and the low-temperature performance will deteriorate.
本发明电解液中，第二添加剂b2和第三添加剂c2的含量之比在0.2～10之间，优选0.5～7.5之间，一旦第二添加剂b2和第三添加剂c2的含量之比过小(如小于0.2)，第三添加剂c2含量过量，负极成膜效果改善不明显，高温性能劣化；一旦第二添加剂b2和第三添加剂c2的含量之比过大(如大于10)，第二添加剂b2含量过量，在负极成膜较厚，则会增加电池阻抗，劣化低温性能。In the electrolyte of the present invention, the ratio of the content of the second additive b2 to that of the third additive c2 is between 0.2 and 10, preferably between 0.5 and 7.5. Once the ratio of the content of the second additive b2 to that of the third additive c2 is too small (such as less than 0.2), the content of the third additive c2 is excessive, the negative electrode film-forming effect is not significantly improved, and the high-temperature performance is deteriorated; once the ratio of the content of the second additive b2 to that of the third additive c2 is too large (such as greater than 10), the content of the second additive b2 is excessive, the negative electrode film is thicker, the battery impedance will increase, and the low-temperature performance will deteriorate.
本发明电解液中，第二添加剂b2、第三添加剂c2含量之和与第一添加剂的比值在0.07～20之间，优选1～12.5之间，一旦该比值过小(如小于0.07)，负极成膜效果改善不明显，高温性能劣化；一旦该比值过大(如大于20)，则会增加电池阻抗，劣化低温性能。In the electrolyte of the present invention, the ratio of the sum of the contents of the second additive b2 and the third additive c2 to the first additive is between 0.07 and 20, preferably between 1 and 12.5. Once the ratio is too small (such as less than 0.07), the negative electrode film formation effect is not significantly improved and the high temperature performance is deteriorated; once the ratio is too large (such as greater than 20), the battery impedance will increase and the low temperature performance will be deteriorated.
在符合上述第一添加剂、第二添加剂b2和第三添加剂c2之间特定含量比例关系后，第一添加剂、第二添加剂b2和第三添加剂各自用量仍需符合下述规定，也即：After meeting the specific content ratio relationship between the first additive, the second additive b2 and the third additive c2 , the respective amounts of the first additive, the second additive b2 and the third additive must still meet the following requirements, that is:
0.2≤a≤3。如果第一添加剂的添加量过低(如低于0.2)，其负极成膜效果差，电池阻抗增加，低温性能降低；如果第一添加剂的添加量过高(如高于3)，电池高温性能降低。0.2≤a≤3. If the amount of the first additive added is too low (such as less than 0.2), the negative electrode film-forming effect is poor, the battery impedance increases, and the low-temperature performance decreases; if the amount of the first additive added is too high (such as higher than 3), the high-temperature performance of the battery decreases.
0.1≤b≤2.5。如果第二添加剂b2的添加量过低(如低于0.1)，其负极成膜效果差，电池高温性能降低；如果第二添加剂b2的添加量过高(如高于2.5)，电池阻抗增大，低温性能降低。0.1≤b≤2.5. If the amount of the second additive b2 added is too low (such as less than 0.1), the negative electrode film-forming effect is poor and the high-temperature performance of the battery is reduced; if the amount of the second additive b2 added is too high (such as higher than 2.5), the battery impedance increases and the low-temperature performance is reduced.
0.1≤c≤2.5。如果第三添加剂c2的添加量过低(如低于0.1)，其负极成膜效果差，电池阻抗增加，低温性能降低；如果第三添加剂c2的添加量过高(如高于2.5)，电池高温性能降低。0.1≤c≤2.5. If the amount of the third additive c2 added is too low (such as less than 0.1), the negative electrode film-forming effect is poor, the battery impedance increases, and the low-temperature performance decreases; if the amount of the third additive c2 added is too high (such as higher than 2.5), the high-temperature performance of the battery decreases.
本发明的第一添加剂在制备过程中，由于制备工艺的不同，除前述(I-1)所示结构的焦硫酸根三氟化硼复合锂盐外，还会包括下式(I-2)、(I-3)、(I-4)、(I-5)、(I-6)所示化合物中的至少一种：


During the preparation process of the first additive of the present invention, due to different preparation processes, in addition to the pyrosulfate boron trifluoride composite lithium salt of the structure shown in the above (I-1), at least one of the compounds shown in the following formulas (I-2), (I-3), (I-4), (I-5), and (I-6) may be included:


且第一添加剂中至少包含80wt％以上的所述式(I-1)所示结构的焦硫酸根三氟化硼复合锂盐。优选地，第一添加剂中包含80～95wt％的所述式(I-1)所示结构的焦硫酸根三氟化硼复合锂盐，其余为化合物(I-2)、(I-3)、(I-4)、(I-5)或(I-6)中的至少一种。The first additive contains at least 80 wt% of the pyrosulfate boron trifluoride complex lithium salt of the structure shown in formula (I-1). Preferably, the first additive contains 80-95 wt% of the pyrosulfate boron trifluoride complex lithium salt of the structure shown in formula (I-1), and the rest is at least one of compounds (I-2), (I-3), (I-4), (I-5) or (I-6).
本发明的第二添加剂b2中，优选地，R1、R2、R3、R4、R5、R6、R7、R8、R9、R10独立地选自氢、甲基、乙基或卤素，m、n独立地选自1或2，且每个重复单元中，R5、R6、R9、R10选自相同或不同的取代基。In the second additive b2 of the present invention, preferably, R1 , R2 , R3 , R4 , R5 , R6 , R7 , R8 , R9 , R10 are independently selected from hydrogen, methyl, ethyl or halogen, m and n are independently selected from 1 or 2, and in each repeating unit, R5 , R6 , R9 , R10 are selected from the same or different substituents.
进一步优选地，所述第二添加剂b2选自下述结构所示的环状磺酸酯类化合物中的至少一种：

Further preferably, the second additive b2 is selected from at least one of the cyclic sulfonate compounds shown in the following structures:

本发明的第三添加剂c2中，R11、R12独立地选自卤素，R13选自直连键、亚甲基或氟代亚甲基；更优选地，第三添加剂c2选自下述结构所示的草酸根锂盐中的至少一种：
In the third additive c2 of the present invention, R11 and R12 are independently selected from halogen, and R13 is selected from a direct bond, a methylene group or a fluoromethylene group; more preferably, the third additive c2 is selected from at least one of the lithium oxalate salts shown in the following structure:
本发明的焦硫酸根三氟化硼复合锂盐、环状磺酸酯类化合物和草酸根锂盐同时用于电解液中，三者能发挥协同作用，且缺一不可。虽然三者的协同作用机制尚未完全明晰，但通过实验结论推测：三者联用后能抑制环状磺酸酯类化合物在2.35V～2.40V左右的反应强度，抑制EC等非水溶剂在2.65V～2.75V左右的反应消耗，并通过三者含量的控制来实现其在负极的反应强度调控，使得在负极形成富含Li2SO4、Li2SO3等无机盐成分和-S-O-B-交联网状的有机成分的有机-无机多组分复合SEI膜，抑制了环状磺酸酯类化合物和/或草酸根锂盐在负极反应带来的性能劣化，从而降低电池阻抗，提升高温存储性能、高温循环性能和低温性能The pyrosulfate boron trifluoride composite lithium salt, cyclic sulfonate compounds and oxalate lithium salt of the present invention are used in the electrolyte at the same time, and the three can play a synergistic role, and none of them can be missing. Although the synergistic mechanism of the three has not yet been fully clarified, it is speculated through experimental conclusions that the three can inhibit the reaction intensity of cyclic sulfonate compounds at about 2.35V to 2.40V, inhibit the reaction consumption of non-aqueous solvents such as EC at about 2.65V to 2.75V, and control the content of the three to achieve the regulation of the reaction intensity at the negative electrode, so that an organic-inorganic multi-component composite SEI film rich in inorganic salt components such as Li 2 SO 4 and Li 2 SO 3 and -SOB- cross-linked network organic components is formed at the negative electrode, which inhibits the performance degradation caused by the reaction of cyclic sulfonate compounds and/or oxalate lithium salts at the negative electrode, thereby reducing the battery impedance and improving the high-temperature storage performance, high-temperature cycle performance and low-temperature performance
进一步地，本发明的电解液还包括第四添加剂d2，所述第四添加剂d2为碳酸亚乙烯酯，在电解液中的质量百分含量为0.1～5wt％；优选地，碳酸亚乙烯酯 在电解液中的质量百分含量为0.15～3.0wt％。Furthermore, the electrolyte of the present invention further comprises a fourth additive d2 , wherein the fourth additive d2 is vinylene carbonate, and the mass percentage content of the vinylene carbonate in the electrolyte is 0.1 to 5 wt%. The mass percentage in the electrolyte is 0.15-3.0wt%.
碳酸亚乙烯酯作为一种成膜添加剂，在第一添加剂、第二添加剂b2和第三添加剂c2的基础上加入碳酸亚乙烯酯，其在循环过程中持续反应，在电极表面形成稳定致密的聚合物薄膜，进而抑制溶剂分子嵌入破坏电极，从而提升电池性能。As a film-forming additive, vinylene carbonate is added on the basis of the first additive, the second additive b2 and the third additive c2 . Vinylene carbonate reacts continuously during the cycle to form a stable and dense polymer film on the electrode surface, thereby inhibiting the embedding of solvent molecules to destroy the electrode, thereby improving battery performance.
根据不同电解液的应用场景和电池电化学性能需求，在本发明所述电解液中进一步加入基础添加剂，所述基础添加剂选自硫酸酯类化合物、氟代碳酸酯类化合物或含氟锂盐类化合物中的至少一种，用量占电解液总质量的0.1～5.0wt％；According to the application scenarios of different electrolytes and the requirements of battery electrochemical performance, a basic additive is further added to the electrolyte of the present invention, wherein the basic additive is selected from at least one of a sulfate compound, a fluorinated carbonate compound or a fluorinated lithium salt compound, and the amount thereof accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte;
所述硫酸酯类化合物选自硫酸乙烯酯、季戊四醇双环硫酸酯、4,4'-联硫酸乙烯酯或4-甲基-硫酸乙烯酯中的至少一种；The sulfate compound is selected from at least one of vinyl sulfate, pentaerythritol bicyclic sulfate, 4,4'-disulfate or 4-methyl-vinyl sulfate;
所述氟代碳酸酯类化合物选自氟代碳酸乙烯酯、双氟代碳酸乙烯酯、三氟甲基碳酸丙烯酯中的至少一种；The fluorinated carbonate compound is selected from at least one of fluoroethylene carbonate, difluoroethylene carbonate, and trifluoromethylpropylene carbonate;
含氟锂盐类化合物选自二氟磷酸锂、四氟硼酸锂、双氟磺酰亚胺锂、双三氟甲基磺酰亚胺锂、四氟草酸磷酸锂、二氟双草酸磷酸锂、二氟草酸硼酸锂、三草酸磷酸锂或下式(IV)所示锂盐中至少一种，且所述含氟锂盐类化合物不同于主锂盐：
The fluorine-containing lithium salt compound is selected from at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, lithium difluorooxalate borate, lithium trioxalate phosphate or the lithium salt represented by the following formula (IV), and the fluorine-containing lithium salt compound is different from the main lithium salt:
式(IV)中，y+z＝4，且y≥0且z≥1，y、z为正整数。In formula (IV), y+z=4, y≥0 and z≥1, and y and z are positive integers.
在一种具体的实施方式中，所述基础添加剂采用质量分数为0.2～1.0％的二氟磷酸锂、质量分数为0.2～1.0％的双氟磺酰亚胺锂和0.2～0.8％的氟代碳酸乙烯酯的组合，可以进一步优化正负极-电解液界面膜组分，改善电池的低温放电性能和倍率充电性能。In a specific embodiment, the basic additive adopts a combination of 0.2-1.0% by mass of lithium difluorophosphate, 0.2-1.0% by mass of lithium bis(fluorosulfonyl)imide and 0.2-0.8% by mass of ethylene fluorocarbonate, which can further optimize the positive and negative electrode-electrolyte interface film components and improve the low temperature discharge performance and rate charging performance of the battery.
在另一种具体的实施方式中，所述基础添加剂采用质量分数为0.2～3.0％的双氟磺酰亚胺锂和0.1～1.0％的氟代碳酸乙烯酯的组合，同样能改善电池的低温 放电性能和倍率充电性能。In another specific embodiment, the base additive is a combination of 0.2-3.0% by mass of lithium bis(fluorosulfonyl)imide and 0.1-1.0% by mass of ethylene carbonate, which can also improve the low temperature performance of the battery. Discharge performance and rate charging performance.
根据本发明的电解液，所述主锂盐选自六氟磷酸锂、四氟硼酸锂、六氟砷酸锂、高氯酸锂、双草酸硼酸锂、二氟草酸硼酸锂、双氟磺酰亚胺锂、双三氟甲基磺酰亚胺锂、四氟草酸磷酸锂、三草酸磷酸锂或二氟双草酸磷酸锂中的至少一种，且其摩尔浓度为0.1～4.0mol/L；优选地，所述主锂盐选自六氟磷酸锂和/或双氟磺酰亚胺锂，在电解液中的浓度为0.5～1.5mol/L。According to the electrolyte of the present invention, the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium tetrafluorooxalate phosphate, lithium trioxalate phosphate or lithium difluorobis(oxalate) phosphate, and its molar concentration is 0.1-4.0 mol/L; preferably, the main lithium salt is selected from lithium hexafluorophosphate and/or lithium bis(fluorosulfonyl imide), and its concentration in the electrolyte is 0.5-1.5 mol/L.
所述非水溶剂选自碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、氟代碳酸乙烯酯、二氟代碳酸乙烯酯、γ-丁内酯、乙酸甲酯、丙酸甲酯、丁酸甲酯、乙酸乙酯、丙酸乙酯、丁酸乙酯、乙酸丙酯、丙酸丙酯、环丁砜、二甲基亚砜、二甲基砜、二乙基砜、三甘醇二甲醚、四甘醇二甲醚或1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚中的至少一种。The non-aqueous solvent is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluoroethylene carbonate, difluoroethylene carbonate, γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, propyl propionate, cyclopentane, dimethyl sulfoxide, dimethyl sulfone, diethyl sulfone, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.
在实际电解液配方应用过程中，有机溶剂均为复杂多组分体系，其中环状碳酸酯具有高介电常数，能更好地溶解锂盐从而提供高电导率；线性碳酸酯及羧酸酯能有效调节电解液黏度及液程，通过不同种类溶剂互配实现各项综合性能均更为合适的有机溶剂体系。In the actual application of electrolyte formulation, organic solvents are all complex multi-component systems. Among them, cyclic carbonates have a high dielectric constant and can better dissolve lithium salts to provide high conductivity; linear carbonates and carboxylates can effectively adjust the viscosity and liquid range of the electrolyte. By matching different types of solvents, an organic solvent system with more suitable comprehensive performance can be achieved.
进一步优选地，本发明所述非水溶剂选自碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、氟代碳酸乙烯酯、乙酸乙酯、丙酸乙酯、乙酸丙酯、环丁砜、二甲基砜或1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚中的至少两种。Further preferably, the non-aqueous solvent of the present invention is selected from at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, fluoroethylene carbonate, ethyl acetate, ethyl propionate, propyl acetate, cyclopentane, dimethyl sulfone or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.
本发明还提供一种锂离子二次电池，包括正极、负极、隔膜，以及上述任一所述的电解液。The present invention also provides a lithium ion secondary battery, comprising a positive electrode, a negative electrode, a separator, and any one of the above-mentioned electrolytes.
本发明的锂离子二次电池，正极的活性材料选自镍钴锰酸锂、钴酸锂、磷酸锰铁锂、尖晶石锰酸锂或镍锰酸锂，负极的活性材料选自石墨和/或硅负极材料。优选地，三元镍钴锰酸锂选自NCM523(LiNi0.5Co0.2Mn0.3O2)、NCM622(LiNi0.6Co0.2Mn0.2O2)、NCM712(LiNi0.7Co0.1Mn0.2O2)、NCM811(LiNi0.8Co0.1Mn0.1O2)或NCM90505(LiNi0.9Co0.05Mn0.05O2)。更优选地，所述三元镍钴锰酸锂选自NCM622(LiNi0.6Co0.2Mn0.2O2)或NCM712(LiNi0.7Co0.1Mn0.2O2)。 In the lithium-ion secondary battery of the present invention, the active material of the positive electrode is selected from lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese iron phosphate, spinel lithium manganese oxide or lithium nickel manganese oxide, and the active material of the negative electrode is selected from graphite and/or silicon negative electrode materials. Preferably, the ternary lithium nickel cobalt manganese oxide is selected from NCM523 (LiNi 0.5 Co 0.2 Mn 0.3 O 2 ), NCM622 (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ), NCM712 (LiNi 0.7 Co 0.1 Mn 0.2 O 2 ), NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) or NCM90505 (LiNi 0.9 Co 0.05 Mn 0.05 O 2 ). More preferably, the ternary lithium nickel cobalt manganese oxide is selected from NCM622 (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ) or NCM712 (LiNi 0.7 Co 0.1 Mn 0.2 O 2 ).
本发明的锂离子二次电池的工作电压≥4.3V，优选≥4.4V，如4.4V、4.48V、4.52V等。The operating voltage of the lithium ion secondary battery of the present invention is ≥4.3V, preferably ≥4.4V, such as 4.4V, 4.48V, 4.52V, etc.
本发明的第三方面，经研究进一步提出了一种包含焦硫酸根三氟化硼复合锂盐和腈类化合物的添加剂组合物及其在电解液配制及锂离子电池中的应用，所述添加剂组合物在保持焦硫酸根三氟化硼复合锂盐的高低温性能的基础上，能进一步提升锂离子电池在高电压下的高温循环稳定性和高温存储稳定性，尤其是抑制电池在高温工况下的产气膨胀，且降低电池初始阻抗。In the third aspect of the present invention, after further research, an additive composition comprising a pyrosulfate boron trifluoride complex lithium salt and a nitrile compound and its application in electrolyte preparation and lithium-ion batteries are proposed. The additive composition can further improve the high-temperature cycle stability and high-temperature storage stability of lithium-ion batteries under high voltage on the basis of maintaining the high and low temperature performance of the pyrosulfate boron trifluoride complex lithium salt, especially inhibit the gas expansion of the battery under high temperature conditions and reduce the initial impedance of the battery.
本发明第三方面涉及的各类化合物代号的化学名称说明如下：The chemical names of the various compound codes involved in the third aspect of the present invention are explained as follows:
1、LiDFOB，化学名称：二氟草酸硼酸锂；1. LiDFOB, chemical name: lithium difluorooxalate borate;
2、LiPO2F2，化学名称：二氟磷酸锂；2. LiPO 2 F 2 , chemical name: lithium difluorophosphate;
3、PS，化学名称：1,3-丙烷磺内酯；3. PS, chemical name: 1,3-propane sultone;
4、TVS，化学名称：四乙烯基硅烷(CAS：1112-55-6)；4. TVS, chemical name: tetravinylsilane (CAS: 1112-55-6);
5、HTCN，化学名称：1,3,6-己烷三腈；5. HTCN, chemical name: 1,3,6-hexanetrinitrile;
6、ADN，化学名称：己二腈；6. ADN, chemical name: adiponitrile;
7、SN，化学名称：丁二腈；7. SN, chemical name: succinonitrile;
8、TCP，化学名称：1,2,3-三(氰乙氧基)丙烷；8. TCP, chemical name: 1,2,3-tri(cyanoethoxy)propane;
9、DFEA，化学名称：乙酸2,2-二氟乙酯(CAS：1550-44-3)；9. DFEA, chemical name: 2,2-difluoroethyl acetate (CAS: 1550-44-3);
10、MMDS，化学名称：甲基二磺酸亚甲酯；10. MMDS, chemical name: methylene disulfonate;
11、DTD，化学名称：硫酸乙烯酯。11. DTD, chemical name: vinyl sulfate.
本发明第三方面的目的是通过以下技术方案实现的：The purpose of the third aspect of the present invention is achieved through the following technical solutions:
一种含新型锂盐的电解液添加剂组合物，所述添加剂组合物包括：An electrolyte additive composition containing a novel lithium salt, the additive composition comprising:
第一添加剂，所述第一添加剂至少包括下式(I-1)所示结构的新型锂盐：
The first additive comprises at least a novel lithium salt having a structure represented by the following formula (I-1):
第二添加剂b3，所述第二添加剂b3为选自下式(IIC)所示结构的腈类化合物，所述腈类化合物为多腈类化合物：
The second additive b 3 is a nitrile compound having a structure selected from the following formula (IIC), wherein the nitrile compound is a polynitrile compound:
式中，M1选自-CH、P或-P＝O，n选自0～5的整数；R14、R15、R16独立地选自直连键、氧、-R17-、-O-R17-或-R18-O-R17-，其中，R17、R18独立地选自C1‐C5亚烷基、C2‐C5亚烯基，或被C1‐C3烷基或氰基取代的C1‐C5亚烷基、C2‐C5亚烯基；In the formula, M1 is selected from -CH, P or -P=O, n is selected from an integer of 0 to 5; R14 , R15 , R16 are independently selected from a direct bond, oxygen, -R17- , -OR17- or -R18 - OR17- , wherein R17 , R18 are independently selected from C1-C5 alkylene, C2-C5 alkenylene, or C1-C5 alkylene or C2-C5 alkenylene substituted by C1-C3 alkyl or cyano;
所述第一添加剂和第二添加剂b3中CN官能团的质量比值为0.03～4.0；优选地，所述第一添加剂和第二添加剂b3中CN官能团的质量比值为0.08～1.0；更优选地，所述第一添加剂和第二添加剂b3中CN官能团的质量比值为0.1～0.3。The mass ratio of CN functional groups in the first additive and the second additive b3 is 0.03-4.0; preferably, the mass ratio of CN functional groups in the first additive and the second additive b3 is 0.08-1.0; more preferably, the mass ratio of CN functional groups in the first additive and the second additive b3 is 0.1-0.3.
本发明所述第一添加剂和第二添加剂b3中CN官能团的质量比值指的是：第一添加剂在电解液中的质量含量与第二添加剂b3中CN官能团在电解液中的质量含量之比。第一添加剂在电解液中的质量含量＝(第一添加剂的质量/电解液总质量)*100％；第二添加剂b3中CN官能团在电解液中的质量含量＝(第二添加剂b3的质量*CN官能团在第二添加剂b3中的质量含量/电解液总质量)*100％＝第二添加剂b3在电解液中的质量含量*CN官能团在第二添加剂b3中的质量含量。其中CN官能团在第二添加剂b3中的质量含量通过以下公式计算获得：
The mass ratio of the CN functional groups in the first additive and the second additive b3 of the present invention refers to: the ratio of the mass content of the first additive in the electrolyte to the mass content of the CN functional groups in the second additive b3 in the electrolyte. The mass content of the first additive in the electrolyte = (mass of the first additive/total mass of the electrolyte) * 100%; the mass content of the CN functional groups in the second additive b3 in the electrolyte = (mass of the second additive b3 *mass content of the CN functional groups in the second additive b3 /total mass of the electrolyte) * 100% = mass content of the second additive b3 in the electrolyte * mass content of the CN functional groups in the second additive b3 . The mass content of the CN functional groups in the second additive b3 is calculated by the following formula:
其中，i＝1,2,……，n，n代表不同腈的种类数量，1≤n≤10，Mi为不同腈的相对分子质量，ai为第i种腈CN官能团的数量，26为CN官能团的相对分子质量。例如，第二添加剂b3仅包含一种腈类化合物，在该腈类化合物中包含2个CN官能团，则n为1，该腈类化合物的相对分子质量为M1，CN官能团在第二添加剂b3中的质量含量为52/M1。又如，第二添加剂b3中包含两种不同的腈类化合物，第一种腈类化合物中包含2个CN官能团，相对分子质量为M1，第二种腈类化合物中包含3个CN官能团，相对分子质量为M2，则n为2，
Wherein, i=1,2,...,n, n represents the number of different nitriles, 1≤n≤10, Mi is the relative molecular mass of different nitriles, ai is the number of CN functional groups of the i-th nitrile, and 26 is the relative molecular mass of the CN functional group. For example, the second additive b3 contains only one nitrile compound, which contains 2 CN functional groups, then n is 1, the relative molecular mass of the nitrile compound is M1 , and the mass content of the CN functional group in the second additive b3 is 52/ M1 . For another example, the second additive b3 contains two different nitrile compounds, the first nitrile compound contains 2 CN functional groups, and the relative molecular mass is M1 , and the second nitrile compound contains 3 CN functional groups, and the relative molecular mass is M2 , then n is 2,
在商业化的高电压电解液配方中，通常由2-4种第二添加剂b3构成的腈类化合物的组合物，且不同腈类化合物CN官能团的个数不同，因此采用CN官能团的质量含量替代腈类化合物的质量含量更能够合理地表述第一添加剂和第二添加剂b3的协同效应。In commercial high-voltage electrolyte formulations, a composition of nitrile compounds is usually composed of 2-4 second additives b3 , and different nitrile compounds have different numbers of CN functional groups. Therefore, using the mass content of CN functional groups instead of the mass content of nitrile compounds can more reasonably express the synergistic effect of the first additive and the second additive b3 .
本发明的添加剂组合物中，第一添加剂在首次化成的时候，能先于第二添加剂b3在负极界面形成稳定的钝化膜，抑制第二添加剂b3(多氰基添加剂)对负极界面的破坏，降低负极阻抗。如此，还能促进第二添加剂b3依靠其氰基(CN)官能团的强配位能力，和正极表面的活性位点(比如高价态的金属离子如镍/钴/锰等)结合，起到掩蔽正极表面活性离子、减少电极对电解液分解的作用；且第二添加剂b3中的氰基(CN)官能团中氮叁键的键能很高，不容易被氧化，在高电压正极上具有较强的稳定性。通过第一添加剂和第二添加剂b3二者共同使用，既抑制了锂离子电池在高温存储下的胀气，又降低了负极阻抗，提升电池的动力学性能，保证了锂离子电池的长循环稳定性。In the additive composition of the present invention, the first additive can form a stable passivation film at the negative electrode interface before the second additive b3 when it is first formed, inhibit the second additive b3 (polycyano additive) from damaging the negative electrode interface, and reduce the negative electrode impedance. In this way, the second additive b3 can also be promoted to rely on its strong coordination ability of the cyano (CN) functional group to combine with the active sites on the positive electrode surface (such as high-valent metal ions such as nickel/cobalt/manganese, etc.), play a role in shielding the active ions on the positive electrode surface and reducing the decomposition of the electrode to the electrolyte; and the nitrogen triple bond energy in the cyano (CN) functional group in the second additive b3 is very high, not easily oxidized, and has strong stability on the high-voltage positive electrode. By using the first additive and the second additive b3 together, the flatulence of the lithium ion battery under high-temperature storage is inhibited, the negative electrode impedance is reduced, the dynamic performance of the battery is improved, and the long-cycle stability of the lithium ion battery is guaranteed.
本发明的第一添加剂在制备过程中，由于制备工艺的不同，除前述(I-1)所示结构的新型锂盐外，还会包括下式(I-2)、(I-3)、(I-4)、(I-5)、(I-6)所示化合物中的至少一种：

During the preparation process of the first additive of the present invention, due to different preparation processes, in addition to the novel lithium salt having the structure shown in the above-mentioned (I-1), at least one of the compounds shown in the following formulae (I-2), (I-3), (I-4), (I-5), and (I-6) may be included:

且第一添加剂中至少包含80wt％以上的所述式(I-1)所示结构的新型锂盐。优选地，第一添加剂中包含80.0～95.0wt％的所述式(I-1)所示结构的新型锂 盐，其余为化合物(I-2)、(I-3)、(I-4)、(I-5)或(I-6)中的至少一种。The first additive contains at least 80 wt% or more of the novel lithium salt having the structure represented by formula (I-1). Preferably, the first additive contains 80.0 to 95.0 wt% of the novel lithium salt having the structure represented by formula (I-1). salt, and the rest are at least one of compounds (I-2), (I-3), (I-4), (I-5) or (I-6).
在所述第二添加剂b3中，M1选自-CH、P或-P＝O，n选自0～3的整数；R1、R2、R3独立地选自直连键、氧、-R4-、-O-R4-或-R5-O-R4-，其中，R4、R5独立地选自C1-C3亚烷基、C2-C3亚烯基，或被C1-C3烷基或氰基取代的C1-C3亚烷基、C2-C3亚烯基。In the second additive b3 , M1 is selected from -CH, P or -P＝O, n is selected from an integer of 0 to 3; R1 , R2 , and R3 are independently selected from a direct bond, oxygen, -R4- , -OR4- or -R5 - OR4- , wherein R4 and R5 are independently selected from C1-C3 alkylene, C2-C3 alkenylene, or C1-C3 alkylene, C2-C3 alkenylene substituted by C1-C3 alkyl or cyano.
进一步地，所述第二添加剂b3选自下述结构所示的腈类化合物中的至少一种：
Furthermore, the second additive b3 is selected from at least one of the nitrile compounds shown in the following structures:
本发明还提供一种电解液的配制方法，所述配制方法包括：在非水溶剂中加入主锂盐至主锂盐占电解液总质量的8～20wt％，再加入上述任一所述的添加剂组合物获得电解液，并使得所述第一添加剂占电解液总质量的0.01～5.0wt％，第二添加剂b3占电解液总质量的0.1～10wt％；进一步优选使得第一添加剂占电解液总质量的0.01～2.0wt％，第二添加剂b3占电解液总质量的1～8wt％；更优选使得第一添加剂占电解液总质量的0.1～1.0wt％，第二添加剂b3占电解液总质量的2～6wt％。The present invention also provides a method for preparing an electrolyte, the method comprising: adding a main lithium salt to a non-aqueous solvent until the main lithium salt accounts for 8 to 20 wt% of the total mass of the electrolyte, and then adding any of the above-mentioned additive compositions to obtain an electrolyte, and making the first additive account for 0.01 to 5.0 wt% of the total mass of the electrolyte, and the second additive b3 accounts for 0.1 to 10 wt% of the total mass of the electrolyte; further preferably, making the first additive account for 0.01 to 2.0 wt% of the total mass of the electrolyte, and the second additive b3 accounts for 1 to 8 wt% of the total mass of the electrolyte; more preferably, making the first additive account for 0.1 to 1.0 wt% of the total mass of the electrolyte, and the second additive b3 accounts for 2 to 6 wt% of the total mass of the electrolyte.
所述非水溶剂选自环状碳酸酯和线性碳酸酯和/或线性羧酸酯的混合物，所 述环状碳酸酯选自碳酸乙烯酯、碳酸丙烯酯或氟代碳酸乙烯酯中的至少一种；所述线性碳酸酯选自碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯或甲基三氟乙基碳酸酯中的至少一种；所述线性羧酸酯选自乙酸乙酯、丙酸乙酯、丙酸丙酯、乙酸2,2-二氟乙酯或乙酸2,2,2-三氟乙酯中的至少一种，任一非水溶剂的用量占电解液总质量的0.1～50wt％；The non-aqueous solvent is selected from a mixture of cyclic carbonates and linear carbonates and/or linear carboxylates. The cyclic carbonate is selected from at least one of ethylene carbonate, propylene carbonate or fluoroethylene carbonate; the linear carbonate is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate or methyl trifluoroethyl carbonate; the linear carboxylic acid ester is selected from at least one of ethyl acetate, ethyl propionate, propyl propionate, 2,2-difluoroethyl acetate or 2,2,2-trifluoroethyl acetate, and the amount of any non-aqueous solvent accounts for 0.1 to 50 wt% of the total mass of the electrolyte;
所述主锂盐选自六氟磷酸锂、双氟磺酰亚胺锂或双三氟甲基磺酰亚胺锂中的至少一种。The main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.
在本发明所述电解液的配制方法中，进一步加入第三添加剂c3，所述第三添加剂c3选自下述结构所示的硫氧双键化合物中的至少一种，用量占电解液总质量的0.5～5.0wt％：
In the preparation method of the electrolyte of the present invention, a third additive c 3 is further added, wherein the third additive c 3 is selected from at least one of the sulfur-oxygen double bond compounds shown in the following structures, and the amount used accounts for 0.5-5.0 wt% of the total mass of the electrolyte:
含硫氧双键的第三添加剂c3可以在正负极表面成膜，所形成的含四价或六价等高价态的烷基硫酸锂可提高正极界面的耐氧化性能，同时具有高的锂离子传导性，与上述第一添加剂协同形成有机无机复合的SEI膜,尤其是在第一添加剂与第二添加剂b3中CN官能团的质量比值低于1.0时，第三添加剂c3的引入更能有效抑制第二添加剂b3对负极界面膜的破坏，提升电池的存储和循环性能。 The third additive c3 containing a sulfur-oxygen double bond can form a film on the surface of the positive and negative electrodes. The formed alkyl lithium sulfate containing tetravalent or hexavalent high-valent states can improve the oxidation resistance of the positive electrode interface and has high lithium ion conductivity. It cooperates with the above-mentioned first additive to form an organic-inorganic composite SEI film. Especially when the mass ratio of the CN functional groups in the first additive and the second additive b3 is lower than 1.0, the introduction of the third additive c3 can more effectively inhibit the damage of the second additive b3 to the negative electrode interface film, thereby improving the storage and cycle performance of the battery.
优选地，所述第三添加剂c3的用量占电解液总质量的1.0～4.0wt％。Preferably, the amount of the third additive c3 is 1.0-4.0 wt % of the total mass of the electrolyte.
根据不同电解液的应用场景和电池电化学性能需求，在本发明所述电解液的配制方法中，进一步加入基础添加剂，所述基础添加剂选自氟代碳酸乙烯酯、碳酸亚乙烯酯、二氟磷酸锂、四氟硼酸锂、二氟草酸硼酸锂、二氟双草酸磷酸锂、三(三甲基硅基)磷酸酯、三(三甲基硅基)硼酸酯中的至少一种，任一添加量占电解液总质量的0.1～2.0wt％。According to the application scenarios of different electrolytes and the requirements of battery electrochemical performance, in the preparation method of the electrolyte of the present invention, a basic additive is further added, and the basic additive is selected from at least one of fluoroethylene carbonate, vinylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium difluorobisoxalatophosphate, tris(trimethylsilyl)phosphate, and tris(trimethylsilyl)borate, and any addition amount accounts for 0.1 to 2.0 wt% of the total mass of the electrolyte.
随着锂离子电池截止工作电压的升高，对更高温度下(如85℃)的高温存储性能提出了更高的挑战。故，进一步地，在本发明所述电解液的配制方法中，进一步加入第四添加剂d3，所述第四添加剂d3选自四乙烯基硅烷、2,4,6-三(烯丙氧基)-1,3,5-三嗪、1,3,5-三烯丙基异氰脲酸酯、1,3-二氧六环、1,4-二氧六环中的至少一种，任一添加量占电解液总质量的0.1～2.0wt％，用于正极成膜，抑制产气，提升电池85℃下的高温存储性能。As the cut-off operating voltage of lithium-ion batteries increases, higher challenges are posed to the high-temperature storage performance at higher temperatures (such as 85°C). Therefore, further, in the preparation method of the electrolyte of the present invention, a fourth additive d3 is further added, and the fourth additive d3 is selected from at least one of tetravinylsilane, 2,4,6-tri(allyloxy)-1,3,5-triazine, 1,3,5-triallyl isocyanurate, 1,3-dioxane, and 1,4-dioxane, and any addition amount accounts for 0.1-2.0wt% of the total mass of the electrolyte, which is used for positive electrode film formation, inhibiting gas production, and improving the high-temperature storage performance of the battery at 85°C.
本发明还提出了一种锂离子二次电池，包括正极极片、负极极片和隔膜，特别地，所述锂离子二次电池通过以下方法制备获得：The present invention also provides a lithium ion secondary battery, comprising a positive electrode sheet, a negative electrode sheet and a separator. In particular, the lithium ion secondary battery is prepared by the following method:
将正极极片、隔膜和负极极片一起卷绕成卷芯，用铝塑膜密封后进行烘烤，之后向其注入上述任一所述配制方法配制获得的电解液，经静置、化成、分容、老化后获得锂离子二次电池。The positive electrode sheet, the separator and the negative electrode sheet are wound together into a roll core, sealed with an aluminum-plastic film and then baked, and then the electrolyte prepared by any of the above-mentioned preparation methods is injected into it, and a lithium-ion secondary battery is obtained after standing, forming, volume separation and aging.
所述锂二次电池正极极片的活性材料选自钴酸锂、镍锰酸锂、富锂锰基、锰酸锂、磷酸铁锂、磷酸锰铁锂或LiNixCoyMnzL(1-x-y-z)O2,其中，L为Al、Sr、Mg、Ti、Ca、Zr、Zn、Si、W或Fe，0≤x≤1，0≤y≤1，0≤z≤1,0.5≤x+y+z≤1，负极极片的活性材料选自石墨、硅碳或硅氧材料。The active material of the positive electrode plate of the lithium secondary battery is selected from lithium cobalt oxide, lithium nickel manganese oxide, lithium-rich manganese base, lithium manganese oxide, lithium iron phosphate, lithium iron manganese phosphate or LiNi x Co y Mn z L (1-xyz) O 2 , wherein L is Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, W or Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0.5≤x+y+z≤1, and the active material of the negative electrode plate is selected from graphite, silicon carbon or silicon oxygen material.
优选地，所述正极极片的活性材料至少包含LiCoO2。也即，所述正极极片的活性材料为LiCoO2，或LiCoO2和LiNixCoyMnzL(1-x-y-z)O2的复合材料。Preferably, the active material of the positive electrode plate at least comprises LiCoO 2 . That is, the active material of the positive electrode plate is LiCoO 2 , or a composite material of LiCoO 2 and LiNi x Co y Mn z L (1-xyz) O 2 .
采用本发明的添加剂组合物配制获得的电解液，其适用于截止电压≥4.35V的锂离子二次电池，也适用于截止电压≥4.45V的锂离子二次电池，更适用于截止电压≥4.48V的锂离子二次电池。在本发明优势的电解液配方中，将其用于截止电压为4.48V的高电压环境下，仍然保持电池的高温循环稳定性、高温存储稳 定性和低温性能。The electrolyte prepared by using the additive composition of the present invention is suitable for lithium ion secondary batteries with a cut-off voltage of ≥4.35V, and is also suitable for lithium ion secondary batteries with a cut-off voltage of ≥4.45V, and is more suitable for lithium ion secondary batteries with a cut-off voltage of ≥4.48V. In the advantageous electrolyte formula of the present invention, when it is used in a high voltage environment with a cut-off voltage of 4.48V, the high temperature cycle stability and high temperature storage stability of the battery are still maintained. Qualitative and low temperature performance.
本发明的电解液添加剂在电池化成过程中参与电极/电解液界面构建，使得在锂离子二次电池的电解液液体中，第一添加剂占电解液液体总质量的0.01～2.0wt％，第二添加剂b3占电解液液体总质量的0.1～6.0wt％。The electrolyte additive of the present invention participates in the construction of the electrode/electrolyte interface during the battery formation process, so that in the electrolyte liquid of the lithium ion secondary battery, the first additive accounts for 0.01-2.0wt% of the total mass of the electrolyte liquid, and the second additive b3 accounts for 0.1-6.0wt% of the total mass of the electrolyte liquid.
进一步地，第三添加剂c3占电解液液体总质量的0.1～3.0wt％，第四添加剂d3占电解液液体总质量的0.02～1.5wt％。Furthermore, the third additive c3 accounts for 0.1-3.0 wt% of the total mass of the electrolyte liquid, and the fourth additive d3 accounts for 0.02-1.5 wt% of the total mass of the electrolyte liquid.
与现有技术相比，本发明具有的有益效果为：Compared with the prior art, the present invention has the following beneficial effects:
1、本发明的电解液强化了电极-电解液界面稳定性，兼顾电池的高低温性能，适用于高能量密度电池体系，且在高温高电压下仍保持各项电化学性能均衡。1. The electrolyte of the present invention enhances the stability of the electrode-electrolyte interface, takes into account the high and low temperature performance of the battery, is suitable for high energy density battery systems, and maintains a balance of various electrochemical properties at high temperature and high voltage.
2、本发明第一方面的电解液发挥第一添加剂、第二添加剂b1的协同作用，形成富含Li2SO4、Li2SO3等无机盐成分和-S-O-B-交联网状的有机成分的有机-无机复合膜，能改善电池的高低温性能；并进一步通过第三添加剂c1的协同，在有机-无机复合膜外形成富含类PEO聚合物的外膜，该双层膜具有良好的导离子性和隔离电解液的作用，使得电池具有优异的循环性能、高温性能和抑制产气效果，且兼顾低温性能。2. The electrolyte of the first aspect of the present invention exerts the synergistic effect of the first additive and the second additive b1 to form an organic-inorganic composite membrane rich in inorganic salt components such as Li2SO4 and Li2SO3 and -SOB- cross-linked network organic components, which can improve the high and low temperature performance of the battery; and further through the synergy of the third additive c1 , an outer membrane rich in PEO-like polymers is formed outside the organic-inorganic composite membrane. The double-layer membrane has good ion conductivity and the function of isolating the electrolyte, so that the battery has excellent cycle performance, high temperature performance and gas production inhibition effect, while taking into account low temperature performance.
3、本发明第二方面的电解液通过焦硫酸根三氟化硼复合锂盐、环状磺酸酯类化合物和草酸根锂盐联用，并通过调控三种添加剂在特定含量配比范围内使其充分产生协同效应，获得合适的成膜电位，抑制环状磺酸酯类化合物在2.35V～2.40V左右的反应强度，抑制EC等非水溶剂在2.65V～2.75V左右的反应消耗，并通过三者含量的控制调控其在负极的反应强度，在负极成膜形成多组分复合SEI膜，从而在降低电池阻抗、改善低温性能的同时提升高温存储性能和高温循环性能。3. The electrolyte of the second aspect of the present invention uses a pyrosulfate boron trifluoride composite lithium salt, a cyclic sulfonate compound and an oxalate lithium salt in combination, and by regulating the three additives within a specific content ratio range to fully produce a synergistic effect, obtain a suitable film-forming potential, inhibit the reaction intensity of the cyclic sulfonate compound at about 2.35V to 2.40V, inhibit the reaction consumption of non-aqueous solvents such as EC at about 2.65V to 2.75V, and regulate the reaction intensity at the negative electrode by controlling the content of the three, forming a multi-component composite SEI film at the negative electrode, thereby reducing the battery impedance, improving the low-temperature performance, and improving the high-temperature storage performance and high-temperature cycle performance.
4、本发明第三方面的电解液通过第一添加剂与第二添加剂b3中的CN官能团在特定配比和特定各自含量的基础上，两者协同作用，既抑制了锂离子电池在高温存储下的胀气，又降低了负极阻抗，提升了电池的动力学性能，保证了锂离子电池的长循环稳定性。相比于市面常规的锂盐添加剂，该添加剂组合物对高温存储产气的抑制效果明显优于腈类化合物与LiDFOB、LiDFOP等草酸根锂盐添 加剂的组合。4. The electrolyte of the third aspect of the present invention, through the CN functional groups in the first additive and the second additive b3 , in a specific ratio and specific respective contents, the two work synergistically, which not only inhibits the flatulence of the lithium-ion battery under high-temperature storage, but also reduces the negative electrode impedance, improves the dynamic performance of the battery, and ensures the long-cycle stability of the lithium-ion battery. Compared with conventional lithium salt additives on the market, the inhibitory effect of the additive composition on high-temperature storage gas generation is significantly better than that of nitrile compounds and lithium oxalate salt additives such as LiDFOB and LiDFOP. Combination of additives.
附图说明BRIEF DESCRIPTION OF THE DRAWINGS
附图1为本发明实施例2.1、对比例2.5、对比例2.6和对比例2.7的化成dQ/dV曲线。FIG1 is a dQ/dV curve of Example 2.1, Comparative Example 2.5, Comparative Example 2.6 and Comparative Example 2.7 of the present invention.
具体实施方式Detailed ways
下面结合具体实施例来对本发明进行进一步说明，但并不将本发明局限于这些具体实施方式。本领域技术人员应该认识到，本发明涵盖了权利要求书范围内所可能包括的所有备选方案、改进方案和等效方案。The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.
本发明实施例的第一方面，提供包含焦硫酸根三氟化硼复合锂盐、1,3-丙磺酸内酯和/或硫酸乙烯酯的高能量密度电池电解液及应用。According to a first aspect of an embodiment of the present invention, a high energy density battery electrolyte and application thereof are provided, comprising a pyrosulfate boron trifluoride composite lithium salt, 1,3-propane sultone and/or vinyl sulfate.
一、添加剂制备1. Preparation of Additives
制备例1Preparation Example 1
本制备例提供焦硫酸根三氟化硼复合锂盐的制备方法，具体包括以下步骤：This preparation example provides a method for preparing a pyrosulfate boron trifluoride composite lithium salt, which specifically includes the following steps:
S1：在露点-40℃的干燥房中，向反应瓶中加入0.2mol焦硫酸锂(纯度99％)，以碳酸二甲酯为溶剂，开启搅拌将体系混合均匀；再向反应瓶中通入0.4mol的三氟化硼气体，50℃下反应5h，获得焦硫酸根三氟化硼复合锂盐反应液；S1: In a drying room with a dew point of -40°C, add 0.2 mol of lithium pyrosulfate (purity 99%) to a reaction bottle, use dimethyl carbonate as a solvent, start stirring to mix the system evenly; then pass 0.4 mol of boron trifluoride gas into the reaction bottle, react at 50°C for 5 hours, and obtain a pyrosulfate boron trifluoride composite lithium salt reaction solution;
S2：采用减压蒸馏除去粗品中的反应溶剂和残留未反应的三氟化硼，减压蒸馏温度控制为60℃，时间控制为0.5h，获得焦硫酸根三氟化硼复合锂盐，记为1#锂盐。S2: The reaction solvent and residual unreacted boron trifluoride in the crude product are removed by vacuum distillation. The vacuum distillation temperature is controlled at 60° C. and the time is controlled at 0.5 h to obtain a pyrosulfate boron trifluoride composite lithium salt, which is recorded as 1# lithium salt.
对1#锂盐测试19F-NMR和11B-NMR，得到NMR图，观察到与制备例1相同的峰，区别在于B谱δ＝-1.17ppm和δ＝-0.81ppm的积分面积比为1：9。经过分析确认1#锂盐含有90.1％的化合物(I-1)和8.9％的化合物(I-2)。The 19 F-NMR and 11 B-NMR of lithium salt No. 1 were tested, and the NMR graphs obtained showed the same peaks as those in Preparation Example 1, except that the integrated area ratio of δ=-1.17 ppm and δ=-0.81 ppm in the B spectrum was 1:9. The analysis confirmed that lithium salt No. 1 contained 90.1% of compound (I-1) and 8.9% of compound (I-2).
制备例2Preparation Example 2
本制备例的操作同制备例1，区别仅在于：S1步骤中反应时间增加至12h， 获得产物，记为2#锂盐。The operation of this preparation example is the same as that of Preparation Example 1, except that the reaction time in step S1 is increased to 12 h. The product was obtained and recorded as 2# lithium salt.
对2#锂盐测试19F-NMR和11B-NMR，得到NMR图，观察到化合物(I-1)和化合物(I-3)的峰(与制备例3中化合物(I-1)、化合物(I-3)的峰一致)；此外，在F谱δ＝-150.12ppm，δ＝-143.73ppm处观察到峰，峰面积积分比为1.5：1；核磁B谱δ＝-1.10ppm，δ＝-0.71ppm观察到峰，峰面积积分比为1：1。确定该物质为化合物(I-4)。The 19 F-NMR and 11 B-NMR of lithium salt No. 2 were tested to obtain NMR graphs, and the peaks of compound (I-1) and compound (I-3) were observed (consistent with the peaks of compound (I-1) and compound (I-3) in Preparation Example 3); in addition, peaks were observed at δ = -150.12 ppm and δ = -143.73 ppm in the F spectrum, and the peak area integration ratio was 1.5:1; peaks were observed at δ = -1.10 ppm and δ = -0.71 ppm in the NMR B spectrum, and the peak area integration ratio was 1:1. The substance was determined to be compound (I-4).
B谱δ＝-1.17ppm、δ＝-0.78ppm、δ＝-0.71ppm的积分面积比为16.11：1.75：1。经过分析确认2#锂盐含有85.4％的化合物(I-1)、9.3％的化合物(I-3)和5.3％的化合物(I-4)。The integrated area ratio of spectrum B δ = -1.17ppm, δ = -0.78ppm, δ = -0.71ppm was 16.11: 1.75: 1. Analysis confirmed that lithium salt No. 2 contained 85.4% of compound (I-1), 9.3% of compound (I-3) and 5.3% of compound (I-4).
制备例3Preparation Example 3
本制备例的操作同制备例2，区别仅在于：S1步骤中反应时间增加至20h，获得产物，记为3#锂盐。The operation of this preparation example is the same as that of Preparation Example 2, except that the reaction time in step S1 is increased to 20 h to obtain a product, which is recorded as 3# lithium salt.
对3#锂盐测试19F-NMR和11B-NMR，得到NMR图，观察到化合物(I-1)、化合物(I-3)和化合物(I-4)的峰(与制备例4中化合物(I-1)、化合物(I-3)、化合物(I-4)的峰一致)；此外，在F谱δ＝-149.36ppm，δ＝-141.12ppm处观察到峰，峰面积积分比为6.1：1；核磁B谱δ＝-1.01ppm，δ＝-0.63ppm观察到峰，峰面积积分比为2.9：1。确定该物质为化合物(I-5)。The 19 F-NMR and 11 B-NMR were tested on lithium salt #3, and the NMR graph was obtained. The peaks of compound (I-1), compound (I-3) and compound (I-4) were observed (consistent with the peaks of compound (I-1), compound (I-3) and compound (I-4) in Preparation Example 4); in addition, peaks were observed at δ = -149.36 ppm and δ = -141.12 ppm in the F spectrum, and the peak area integration ratio was 6.1:1; peaks were observed at δ = -1.01 ppm and δ = -0.63 ppm in the NMR B spectrum, and the peak area integration ratio was 2.9:1. The substance was determined to be compound (I-5).
B谱δ＝-1.17ppm、δ＝-0.78ppm、δ＝-0.71ppm、δ＝-0.63ppm的积分面积比为28.2：3.17：2.1：1。经过分析确认3#锂盐含有81.8％的化合物(I-1)、9.2％的化合物(I-3)、6.1％的化合物(I-4)和2.9％的化合物(I-5)。The integrated area ratios of spectrum B δ = -1.17ppm, δ = -0.78ppm, δ = -0.71ppm, and δ = -0.63ppm were 28.2: 3.17: 2.1: 1. The analysis confirmed that lithium salt #3 contained 81.8% of compound (I-1), 9.2% of compound (I-3), 6.1% of compound (I-4), and 2.9% of compound (I-5).
二、电解液2. Electrolyte
基础电解液的制备：在充满氩气的手套箱(水分＜5ppm，氧分＜10ppm)中，将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按质量比为EC：EMC：DEC＝3:5:2均匀混合，向混合溶液中缓慢加入六氟磷酸锂(LiPF6)至LiPF6的摩尔浓度为1.2mol/L，作为基础电解液进行使用。Preparation of basic electrolyte: In a glove box filled with argon (water content <5ppm, oxygen content <10ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are evenly mixed in a mass ratio of EC:EMC:DEC=3:5:2, and lithium hexafluorophosphate (LiPF6) is slowly added to the mixed solution until the molar concentration of LiPF6 is 1.2 mol/L, and used as a basic electrolyte.
按照下表1数据定量加入第一添加剂、第二添加剂b1和第三添加剂c1，混合均匀形成电解液：According to the data in Table 1 below, the first additive, the second additive b1 and the third additive c1 are quantitatively added and mixed evenly to form an electrolyte:
表1电解液配方表1
Table 1 Electrolyte formula Table 1
按照下表2数据定量加入双氟磺酰亚胺锂(LiFSI)、二氟磷酸锂(LiDFP)、1#锂盐、1,3-丙磺酸内酯(PS)与碳酸亚乙烯酯(VC)，混合均匀形成电解液：According to the data in Table 2 below, lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorophosphate (LiDFP), 1# lithium salt, 1,3-propane sultone (PS) and vinylene carbonate (VC) are quantitatively added and mixed evenly to form an electrolyte:
表2电解液配方表2

Table 2 Electrolyte formula Table 2

二、电化学性能测试2. Electrochemical performance test
将上述实施例和对比例的锂离子电池电解液分别制作成软包容量1000mAh锂离子动力电池，所述锂离子动力电池包括正极极片、负极极片、隔膜、电解液以及电池辅料，正极活性材料为LiNi0.6Co0.2Mn0.2O2(NCM622)，负极活性材料为石墨。The lithium ion battery electrolytes of the above embodiments and comparative examples were respectively made into lithium ion power batteries with a soft package capacity of 1000 mAh. The lithium ion power batteries included a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and battery auxiliary materials. The positive electrode active material was LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), and the negative electrode active material was graphite.
制备过程如下：将正极极片、隔膜和负极极片一起卷绕成卷芯，用铝塑膜进行密封后进行烘烤使得电极水分满足要求，烘烤后电芯进行电解液注液，经静置、化成、分容、老化工序得成品软包电芯。The preparation process is as follows: the positive electrode sheet, the separator and the negative electrode sheet are wound together into a core, which is sealed with an aluminum-plastic film and then baked so that the moisture content of the electrode meets the requirements. After baking, the battery cell is injected with electrolyte, and the finished soft-pack battery cell is obtained through the steps of standing, forming, capacity separation and aging.
对上述锂离子电池各项性能进行测试，包括：The above lithium-ion batteries are tested for various performances, including:
(1)循环性能测试(1) Cyclic performance test
在规定温度下以1C的电流恒流充电至充电截止电压，然后恒压充电至电流下降至0.1C，然后以1C的电流恒流放电至2.8V，如此循环特定周数，记录第1周的放电容量和最后1周的放电容量，按下式计算电池循环的容量保持率：At a specified temperature, charge at a constant current of 1C to the charge cut-off voltage, then charge at a constant voltage until the current drops to 0.1C, then discharge at a constant current of 1C to 2.8V. Repeat this cycle for a specific number of weeks, record the discharge capacity of the first week and the discharge capacity of the last week, and calculate the capacity retention rate of the battery cycle according to the following formula:
容量保持率＝最后1周的放电容量/第1周的放电容量*100％。Capacity retention rate = discharge capacity in the last week/discharge capacity in the first week*100%.
(2)高温存储性能测试(2) High temperature storage performance test
常温下以1C的电流恒流充电至充电截止电压，并恒压充电至电流下降至0.1C，随后在60℃恒温烘箱中静置56d。存储后的电池降温至常温时，记录初始体积及存储后的体积：At room temperature, charge at a constant current of 1C to the charge cut-off voltage, and charge at a constant voltage until the current drops to 0.1C, and then place in a 60°C constant temperature oven for 56 days. When the battery after storage cools to room temperature, record the initial volume and the volume after storage:
体积膨胀率＝(存储后体积-存储前体积)/存储前体积*100％。Volume expansion ratio = (volume after storage - volume before storage) / volume before storage * 100%.
(3)低温放电性能测试(3) Low temperature discharge performance test
常温下以1C的电流恒流充电至充电截止电压，然后恒压充电至电流下降至0.1C，然后以1C的电流恒流放电至2.8V，记录放电容量；重复上述充电过程，然后低温下以1C的电流恒流放电至2.8V，记录放电容量，按下式计算电池低 温放电性能：At room temperature, charge at a constant current of 1C to the charging cut-off voltage, then charge at a constant voltage until the current drops to 0.1C, then discharge at a constant current of 1C to 2.8V, record the discharge capacity; repeat the above charging process, then discharge at a constant current of 1C to 2.8V at low temperature, record the discharge capacity, and calculate the battery low voltage as follows: Warm discharge performance:
低温放电率＝低温放电容量/常温放电容量*100％。Low temperature discharge rate = low temperature discharge capacity / normal temperature discharge capacity * 100%.
(4)倍率充电性能测试(4) Rate charging performance test
常温下以规定电流对电池进行恒流充电至充电截止电压，然后恒压充电至电流下降至0.1C，记录充电总容量与恒流段充电容量，按下式计算电池恒流冲入比：At room temperature, the battery is charged at a constant current with a specified current to the charging cut-off voltage, and then charged at a constant voltage until the current drops to 0.1C. The total charging capacity and the charging capacity in the constant current section are recorded, and the battery constant current charging ratio is calculated as follows:
恒流冲入比＝恒流充电容量/充电总容量*100％。Constant current charging ratio = constant current charging capacity/total charging capacity*100%.
具体测试结果如下表3、表4所示：The specific test results are shown in Table 3 and Table 4 below:
表3 NCM622//AG-4.4V电化学测试结果

Table 3 NCM622//AG-4.4V electrochemical test results

表4 NCM622//AG-4.4V电化学测试结果
Table 4 NCM622//AG-4.4V electrochemical test results
比较上表3中的实施例1.1～1.6和对比例1.1可知，在基础电解液中加入第一添加剂和第二添加剂b1的组合物，可以显著提高电池的高温存储和循环稳定性，抑制电池的在高温下的体积膨胀。同时，对于电池低温性能也有改善。Comparing Examples 1.1 to 1.6 and Comparative Example 1.1 in Table 3 above, it can be seen that adding the first additive and the second additive b1 to the basic electrolyte can significantly improve the high-temperature storage and cycle stability of the battery, inhibit the volume expansion of the battery at high temperatures, and also improve the low-temperature performance of the battery.
比较上表3中的实施例1.1和对比例1.2、对比例1.4可知，加入第一添加剂和第二添加剂b1的组合物相比单独使用第一添加剂或单独使用第二添加剂b1，电池低温性能优异且高温性能更加显著。原因在于在两者联用过程中，能够形成富含有机-无机复合膜。该膜致密且牢固，不仅保有-S-O-B-交联网状有机成分的高离子导通性，低温性能优异；还具备Li2SO4、Li2SO3等无机盐的高温存储性能 (尤其是抑制产气)，高温性能显著。Comparing Example 1.1 and Comparative Example 1.2 and Comparative Example 1.4 in Table 3 above, it can be seen that the composition with the first additive and the second additive b1 has excellent low-temperature performance and more significant high-temperature performance than the composition with the first additive alone or the second additive b1 alone. The reason is that in the process of combining the two, an organic-inorganic composite film can be formed. The film is dense and strong, not only retains the high ion conductivity of the -SOB- cross-linked network organic component and excellent low-temperature performance; it also has the high-temperature storage performance of inorganic salts such as Li 2 SO 4 and Li 2 SO 3 (especially suppressing gas generation) and has outstanding high temperature performance.
比较上表3中实施例1.13、实施例1.14和实施例1.1，比较实施例1.11和实施例1.2可知，在第一添加剂和第二添加剂b1的组合物基础上继续加入第三添加剂c1，电池不仅具有良好的高低温性能，而且长循环稳定性得到进一步提升。原因在于第三添加剂c1在循环过程中持续消耗，不断形成富含类PEO聚合物等成分的外膜包覆在有机-无机复合膜外，起到保护有机-无机复合膜的作用。Comparing Example 1.13, Example 1.14 and Example 1.1 in Table 3, and comparing Example 1.11 and Example 1.2, it can be seen that by adding the third additive c 1 to the combination of the first additive and the second additive b 1 , the battery not only has good high and low temperature performance, but also further improves long cycle stability. The reason is that the third additive c 1 is continuously consumed during the cycle, and an outer film rich in PEO-like polymers and other components is continuously formed to cover the organic-inorganic composite film, thereby protecting the organic-inorganic composite film.
比较上表3中的实施例1.1～1.6和对比例1.6～1.9可知，当第一添加剂(A)的添加质量、第二添加剂b1(B)的添加质量满足：1.0wt％≤A+B≤4.0wt％。在此范围内，电池的高低温性能得到进一步兼顾。Comparing Examples 1.1 to 1.6 and Comparative Examples 1.6 to 1.9 in Table 3 above, it can be seen that when the added mass of the first additive (A) and the added mass of the second additive b 1 (B) satisfy: 1.0wt%≤A+B≤4.0wt%, within this range, the high and low temperature performance of the battery is further taken into consideration.
比较上表3中的实施例1.11～1.14和对比例1.10～1.12可知，当第一添加剂(A)、第二添加剂b1(B)、第三添加剂c1(C)的添加质量满足：0.25≤C/(A+B)≤4。当三种添加剂c1的添加质量满足上述关系范围时，电池性能更加均衡，不仅具有良好的高低温性能，而且长循环稳定性得到进一步提升。Comparing Examples 1.11 to 1.14 and Comparative Examples 1.10 to 1.12 in Table 3 above, it can be seen that when the added mass of the first additive (A), the second additive b 1 (B), and the third additive c 1 (C) satisfies: 0.25≤C/(A+B)≤4. When the added mass of the three additives c 1 satisfies the above relationship range, the battery performance is more balanced, not only having good high and low temperature performance, but also the long cycle stability is further improved.
比较上表4中的实施例1.15～1.16和实施例1.5，比较实施例1.17～1.18和实施例1.14可知，当第一添加剂、第二添加剂b1、第三添加剂c1与双氟磺酰亚胺锂及二氟磷酸锂联用，可进一步提升电池低温放电及倍率性能。Comparing Examples 1.15-1.16 and Example 1.5 in Table 4, and comparing Examples 1.17-1.18 and Example 1.14, it can be seen that when the first additive, the second additive b 1 , and the third additive c 1 are used in combination with lithium bis(fluorosulfonyl)imide and lithium difluorophosphate, the low temperature discharge and rate performance of the battery can be further improved.
本发明的第二方面提供包含三氟化硼复合锂盐、环状磺酸酯类化合物和草酸根锂盐的电解液配方，特别适用于以镍钴锰酸锂三元材料作为正极的高电压电池体系，尤其是≥4.3V的高电压电池体系。或者说，本发明的电解液配方，在镍钴锰酸锂三元电池的高电压条件下更能显现出其优势。因此，本发明第二方面的实施例在三元体系基础电解液配方的前提下进行电解液的制备及相应性能的测试。The second aspect of the present invention provides an electrolyte formula comprising a boron trifluoride composite lithium salt, a cyclic sulfonate compound and a lithium oxalate salt, which is particularly suitable for a high-voltage battery system using a nickel cobalt manganese oxide ternary material as a positive electrode, especially a high-voltage battery system ≥4.3V. In other words, the electrolyte formula of the present invention can better show its advantages under the high voltage conditions of a nickel cobalt manganese oxide ternary battery. Therefore, the embodiment of the second aspect of the present invention prepares the electrolyte and tests the corresponding performance under the premise of the basic electrolyte formula of the ternary system.
本发明第二方面实施例和对比例中，第一添加剂的种类包括如下几种：In the embodiments and comparative examples of the second aspect of the present invention, the types of the first additive include the following:
第一添加剂A1：由95wt％化合物I-1和5wt％化合物I-2组成；The first additive A1 is composed of 95 wt% of compound I-1 and 5 wt% of compound I-2;
第一添加剂A2：由90wt％化合物I-1、6wt％化合物I-2和4wt％化合物I-3组成； The first additive A2 is composed of 90 wt% of compound I-1, 6 wt% of compound I-2 and 4 wt% of compound I-3;
第一添加剂A3：由85wt％化合物I-1、7wt％化合物I-2、5wt％化合物I-3和3wt％化合物I-4组成。The first additive A3 consists of 85 wt% of compound I-1, 7 wt% of compound I-2, 5 wt% of compound I-3 and 3 wt% of compound I-4.
一、电解液的制备1. Preparation of electrolyte
基础电解液1的制备：在充满氩气的手套箱(水分＜5ppm，氧分＜10ppm)中，将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按质量比3：5：2混合形成有机溶剂，加入六氟磷酸锂，直至六氟磷酸锂的加入量基于电解液总质量的质量百分比为1mol/L，获得基础电解液1。Preparation of basic electrolyte 1: In a glove box filled with argon (water content <5 ppm, oxygen content <10 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 3:5:2 to form an organic solvent, and lithium hexafluorophosphate was added until the mass percentage of lithium hexafluorophosphate added based on the total mass of the electrolyte was 1 mol/L to obtain basic electrolyte 1.
按照下表5数据定量加入第一添加剂、第二添加剂b2和第三添加剂c2，混合均匀形成电解液：According to the data in Table 5 below, the first additive, the second additive b2 and the third additive c2 are quantitatively added and mixed evenly to form an electrolyte:
表5电解液配方3


注：添加剂用量调整后，基础电解液中仅调整溶剂用量，且溶剂中各组分配比不变。Table 5 Electrolyte formula 3


Note: After the dosage of additives is adjusted, only the dosage of solvent in the basic electrolyte is adjusted, and the distribution ratio of each group in the solvent remains unchanged.
在基础电解液1中按照下表6数据继续添加碳酸亚乙烯酯(VC)、第一添加剂、第二添加剂b2和第三添加剂c2，混合均匀形成电解液：Vinylene carbonate (VC), the first additive, the second additive b2 and the third additive c2 are added to the basic electrolyte 1 according to the data in Table 6 below, and mixed evenly to form an electrolyte:
表6电解液配方4

注：添加剂用量调整后，基础电解液中仅调整溶剂用量，且溶剂中各组分配比不变。Table 6 Electrolyte Formula 4

Note: After the dosage of additives is adjusted, only the dosage of solvent in the basic electrolyte is adjusted, and the distribution ratio of each group in the solvent remains unchanged.
在基础电解液1中添加质量百分含量为0.2％的碳酸亚乙烯酯(VC)，质量百分含量为1％的硫酸乙烯酯(DTD)，再进一步按照下表7数据定量加入第一添加剂、第二添加剂b2、第三添加剂c2以及二氟磷酸锂(LiDFP)、双氟磺酰亚胺锂(LiFSI)、和氟代碳酸乙烯酯(FEC)，混合均匀形成电解液：0.2% by weight of vinylene carbonate (VC) and 1% by weight of vinyl sulfate (DTD) were added to the basic electrolyte 1, and the first additive, the second additive b2 , the third additive c2 , lithium difluorophosphate (LiDFP), lithium bis(fluorosulfonyl)imide (LiFSI), and fluoroethylene carbonate (FEC) were further quantitatively added according to the data in Table 7 below, and the mixture was uniformly mixed to form an electrolyte:
表7电解液配方5

注：添加剂用量调整后，基础电解液中仅调整溶剂用量，且溶剂中各组分配比不变。Table 7 Electrolyte Formula 5

Note: After the dosage of additives is adjusted, only the dosage of solvent in the basic electrolyte is adjusted, and the distribution ratio of each group in the solvent remains unchanged.
二、电池制作及性能测试2. Battery production and performance testing
将上述实施例和对比例的锂离子电池电解液分别制作成软包容量1000mAh锂离子动力电池，所述锂离子动力电池包括正极极片、负极极片、隔膜、电解液以及电池辅料，正极活性材料为镍钴锰酸锂NCM712(LiNi0.7Co0.1Mn0.2O2)，负极活性材料为石墨。The lithium ion battery electrolytes of the above embodiments and comparative examples were respectively made into lithium ion power batteries with a soft package capacity of 1000 mAh. The lithium ion power batteries comprised positive electrode sheets, negative electrode sheets, separators, electrolytes and battery auxiliary materials. The positive electrode active material was lithium nickel cobalt manganese oxide NCM712 (LiNi 0.7 Co 0.1 Mn 0.2 O 2 ), and the negative electrode active material was graphite.
制备过程如下：将正极极片、隔膜和负极极片一起卷绕成卷芯，用铝塑膜进行密封后进行烘烤使得电极水分满足要求，烘烤后电芯进行电解液注液，经静置、化成、老化、分容等工序得到成品软包电芯。The preparation process is as follows: the positive electrode sheet, separator and negative electrode sheet are wound together into a core, sealed with an aluminum-plastic film and then baked so that the moisture content of the electrode meets the requirements. After baking, the battery cell is injected with electrolyte, and the finished soft-pack battery cell is obtained through standing, forming, aging, capacity separation and other processes.
对制备获得的锂离子电池进行各项性能进行测试，包括：The prepared lithium-ion battery is tested for various properties, including:
(1)dQ/dV曲线：(1) dQ/dV curve:
在电池化成阶段：在常温(25℃)下以0.05C的电流恒流充电至3.0V，每间隔10s，记录电池电压Vn与充电容量Cn，按下式计算dQn/dVn值，并以记录点电压Vn为横坐标，dQn/dVn值为纵坐标，绘制dQ/dV曲线：In the battery formation stage: charge at a constant current of 0.05C to 3.0V at room temperature (25℃), record the battery voltage Vn and charging capacity Cn every 10s, calculate the dQn / dVn value according to the following formula, and draw the dQ/dV curve with the recording point voltage Vn as the horizontal axis and the dQn / dVn value as the vertical axis:
dQn/dVn＝(Qn+1-Qn-1)/(Vn+1-Vn-1)*100％ dQn / dVn =(Qn +1 - Qn-1 )/( Vn+1 - Vn-1 )*100%
附图1给出了实施例1与对比例5、6、7的化成dQ/dV曲线，其中，从对比例6的化成dQ/dV曲线可以看出，第一添加剂和第二添加剂b2同时用于电解液中，其三元(NCM712)/石墨全电池成膜电位约为2.35V～2.40V和2.65～2.70V，参与负极成膜反应，影响SEI界面膜成分。FIG1 shows the formation dQ/dV curves of Example 1 and Comparative Examples 5, 6, and 7. It can be seen from the formation dQ/dV curve of Comparative Example 6 that the first additive and the second additive b2 are used in the electrolyte at the same time, and the ternary (NCM712)/graphite full battery film forming potential is about 2.35V~2.40V and 2.65~2.70V, which participate in the negative electrode film forming reaction and affect the SEI interface film composition.
从对比例7的化成dQ/dV曲线可以看出，第一添加剂和第三添加剂c2同时用于电解液中，其三元(NCM712)/石墨全电池成膜电位约为1.50V～1.60V和2.65V～2.75V，参与负极成膜反应，影响SEI界面膜成分。It can be seen from the formation dQ/dV curve of Comparative Example 7 that the first additive and the third additive c2 are used in the electrolyte at the same time, and their ternary (NCM712)/graphite full battery film formation potentials are approximately 1.50V~1.60V and 2.65V~2.75V, which participate in the negative electrode film formation reaction and affect the SEI interface film composition.
从对比例5的化成dQ/dV曲线可以看出，第二添加剂b2和第三添加剂c2同时用于电解液中，其三元(NCM712)/石墨全电池成膜电位约为1.50V～1.60V和2.30V～2.40V，参与负极成膜反应，影响SEI界面膜成分。It can be seen from the formation dQ/dV curve of Comparative Example 5 that the second additive b2 and the third additive c2 are used in the electrolyte at the same time, and their ternary (NCM712)/graphite full battery film formation potentials are approximately 1.50V~1.60V and 2.30V~2.40V, which participate in the negative electrode film formation reaction and affect the SEI interface film composition.
图1还给出了本发明实施例2.1中第一添加剂、第二添加剂b2和第三添加剂 c2联用时的化成dQ/dV曲线，其三元(NCM712)/石墨全电池成膜电位仅出现2个峰，也即约为1.50V～1.60V和2.30V～2.40V的成膜电位，且2.30V～2.40V位置的成膜峰强度明显降低。由此可以看出，第一添加剂、第二添加剂b2和第三添加剂c2联用时发生了相互协同作用，推测原因在于：三者联用的相互作用，抑制了第二添加剂b2在2.35V～2.40V左右的反应强度，抑制EC等非水溶剂在2.65V～2.75V左右的反应消耗，同时通过三者含量的控制来.调控各添加剂在负极的反应量，调节负极SEI膜组成，形成多组分复合SEI膜。FIG. 1 also shows the first additive, the second additive b2 and the third additive in Example 2.1 of the present invention. The dQ/dV curve of the formation when the first additive, the second additive b 2 and the third additive c 2 are used together, and the film formation potential of the ternary (NCM712)/graphite full battery has only two peaks, namely, the film formation potential of about 1.50V~1.60V and 2.30V~2.40V, and the film formation peak intensity at the position of 2.30V~2.40V is significantly reduced. It can be seen that the first additive, the second additive b 2 and the third additive c 2 have a synergistic effect when used together. The reason is speculated to be that the interaction of the three combined inhibits the reaction intensity of the second additive b 2 at about 2.35V~2.40V, and inhibits the reaction consumption of non-aqueous solvents such as EC at about 2.65V~2.75V. At the same time, the reaction amount of each additive in the negative electrode is regulated by controlling the content of the three, and the composition of the negative electrode SEI film is adjusted to form a multi-component composite SEI film.
(2)初始阻抗测试：(2) Initial impedance test:
在电池分容阶段：在常温(25℃)下以0.2C的电流恒流充电至充电截止电压，并恒压充电至电流下降至0.05C；然后以0.2C的电流恒流放电至放电截止电压，记录放电容量C1，即为电池初始容量；In the battery capacity division stage: at room temperature (25°C), charge at a constant current of 0.2C to the charge cut-off voltage, and charge at a constant voltage until the current drops to 0.05C; then discharge at a constant current of 0.2C to the discharge cut-off voltage, and record the discharge capacity C1, which is the initial capacity of the battery;
再以0.2C的电流恒流充电至充电截止电压，并恒压充电至电流下降至0.05C；然后以0.2C的电流恒流放电至容量达到0.5*C1，即为50％SOC荷电状态，静置2小时，记录电压U1；Then charge at a constant current of 0.2C to the charging cut-off voltage, and charge at a constant voltage until the current drops to 0.05C; then discharge at a constant current of 0.2C until the capacity reaches 0.5*C1, i.e. 50% SOC state of charge, stand for 2 hours, and record the voltage U1;
最后以4C的电流恒流放电30s，记录电压U2，计算电池初始阻抗：
初始阻抗＝(U1-U2)/4*1000Finally, discharge at a constant current of 4C for 30s, record the voltage U2, and calculate the initial impedance of the battery:
Initial impedance = (U1-U2)/4*1000
(3)高温存储性能测试(3) High temperature storage performance test
常温(25℃)下以1C的电流恒流充电至充电截止电压(4.4V)，并恒压充电至电流下降至0.05C，随后在60℃恒温烘箱中静置56d。存储后的电池降温至常温时，记录初始体积V1及存储后的体积V2；将电池以1C的电流恒流放电至放电截止电压，记录初始放电容量C2及存储后的放电容量C3；并按下式计算高温存储体积膨胀率及容量保持率：
高温存储体积膨胀率＝(V2/V1-1)*100％
高温存储容量保持率＝C3/C2*100％At room temperature (25°C), the battery was charged at a constant current of 1C to the charge cut-off voltage (4.4V), and then charged at a constant voltage until the current dropped to 0.05C, and then placed in a 60°C constant temperature oven for 56 days. When the battery after storage cools to room temperature, the initial volume V1 and the volume after storage V2 are recorded; the battery is discharged at a constant current of 1C to the discharge cut-off voltage, and the initial discharge capacity C2 and the discharge capacity C3 after storage are recorded; and the high temperature storage volume expansion rate and capacity retention rate are calculated as follows:
High temperature storage volume expansion rate = (V2/V1-1)*100%
High temperature storage capacity retention rate = C3/C2*100%
(4)高温循环性能测试(4) High temperature cycle performance test
在45℃下以1C的电流恒流充电至充电截止电压，然后恒压充电至电流下 降至0.05C，然后以1C的电流恒流放电至放电截止电压，如此循环特定周数，记录第1周的放电容量C4和最后1周的放电容量C5，按下式计算电池循环的容量保持率：
高温循环容量保持率＝C5/C4*100％At 45°C, charge at a constant current of 1C to the charge cut-off voltage, and then charge at a constant voltage to the current drop below Reduce to 0.05C, then discharge at a constant current of 1C to the discharge cut-off voltage, and repeat this cycle for a specific number of weeks. Record the discharge capacity C4 of the first week and the discharge capacity C5 of the last week, and calculate the capacity retention rate of the battery cycle according to the following formula:
High temperature cycle capacity retention rate = C5/C4*100%
(5)低温放电性能测试(5) Low temperature discharge performance test
常温(25℃)下以1C的电流恒流充电至充电截止电压，然后恒压充电至电流下降至0.05C，然后以1C的电流恒流放电至放电截止电压，记录放电容量C6；重复上述充电过程，然后低温下以1C的电流恒流放电至放电截止电压，记录放电容量C7，按下式计算电池低温放电性能：
低温放电率＝C7/C6*100％At room temperature (25°C), charge at a constant current of 1C to the charge cut-off voltage, then charge at a constant voltage until the current drops to 0.05C, then discharge at a constant current of 1C to the discharge cut-off voltage, and record the discharge capacity C6; repeat the above charging process, then discharge at a constant current of 1C to the discharge cut-off voltage at low temperature, record the discharge capacity C7, and calculate the low-temperature discharge performance of the battery according to the following formula:
Low temperature discharge rate = C7/C6*100%
具体测试结果如下表8、表9和表10所示：The specific test results are shown in Tables 8, 9 and 10 below:
表8 Ni7//AG-2.8～4.4V电化学测试结果

Table 8 Ni7//AG-2.8～4.4V electrochemical test results

表9 Ni7//AG-2.8～4.4V电化学测试结果
Table 9 Ni7//AG-2.8～4.4V electrochemical test results
表10 Ni7//AG-2.8～4.4V电化学测试结果
Table 10 Ni7//AG-2.8～4.4V electrochemical test results
比较对比例2.1和对比例2.2、2.3、2.4可以看出，单独使用第一添加剂可降低电池阻抗，提升低温放电性能；单独使用第二添加剂b2可提升高温存储及高温循环性能，但会增加初始阻抗且劣化低温性能；单独使用第三添加剂c2可降低阻抗，提升低温放电性能，但会劣化高温存储及高温循环性能。By comparing comparative example 2.1 with comparative examples 2.2, 2.3 and 2.4, it can be seen that the use of the first additive alone can reduce the battery impedance and improve the low-temperature discharge performance; the use of the second additive b2 alone can improve the high-temperature storage and high-temperature cycle performance, but will increase the initial impedance and deteriorate the low-temperature performance; the use of the third additive c2 alone can reduce the impedance and improve the low-temperature discharge performance, but will deteriorate the high-temperature storage and high-temperature cycle performance.
比较实施例2.1和对比例2.5、2.6、2.7可以看出，仅当第一添加剂、第二添加剂b2和第三添加剂c2三者联用时，才能同时达到降低电池初始阻抗，提升低温性能、高温存储性能和高温循环性能，任意两种添加剂的联用均不能达到该效 果。Comparing Example 2.1 with Comparative Examples 2.5, 2.6 and 2.7, it can be seen that only when the first additive, the second additive b2 and the third additive c2 are used in combination, can the initial impedance of the battery be reduced and the low-temperature performance, high-temperature storage performance and high-temperature cycle performance be improved at the same time. The combination of any two additives cannot achieve this effect. fruit.
比较实施例2.1～2.10和对比例2.8、2.9、2.10、2.11可以看出，仅当第一添加剂、第二添加剂b2和第三添加剂c2三者满足关系式0.2≤b+c≤4；0.2≤b/c≤10；0.07≤(b+c)/a≤20时，才能达到降低电池初始阻抗，提升低温放电性能、高温存储性能和高温循环性能的效果。第二添加剂b2和第三添加剂c2的含量之和过小，负极成膜效果改善不明显，电池高温存储和高温循环性能劣化；两者含量之和过大，则电池阻抗增大，低温放电性能劣化。第二添加剂b2和第三添加剂c2的含量之比过小，负极成膜效果改善不明显，电池高温存储及高温循环性能劣化；第二添加剂b2和第三添加剂c2的含量之比过大，则电池阻抗增加，低温放电性能劣化。第二添加剂b2、第三添加剂c2含量之和与第一添加剂的比值过小，负极成膜效果改善不明显，电池高温存储及高温循环性能降低；若该比值过大，则电池阻抗增大，低温放电性能降低。Comparing Examples 2.1 to 2.10 and Comparative Examples 2.8, 2.9, 2.10, and 2.11, it can be seen that only when the first additive, the second additive b 2 , and the third additive c 2 satisfy the relationship 0.2≤b+c≤4; 0.2≤b/c≤10; 0.07≤(b+c)/a≤20, can the effect of reducing the initial impedance of the battery and improving the low-temperature discharge performance, high-temperature storage performance, and high-temperature cycle performance be achieved. If the sum of the contents of the second additive b 2 and the third additive c 2 is too small, the negative electrode film-forming effect is not significantly improved, and the high-temperature storage and high-temperature cycle performance of the battery are deteriorated; if the sum of the contents of the two is too large, the battery impedance increases and the low-temperature discharge performance is deteriorated. If the ratio of the contents of the second additive b 2 and the third additive c 2 is too small, the negative electrode film-forming effect is not significantly improved, and the high-temperature storage and high-temperature cycle performance of the battery are deteriorated; if the ratio of the contents of the second additive b 2 and the third additive c 2 is too large, the battery impedance increases and the low-temperature discharge performance is deteriorated. If the ratio of the sum of the contents of the second additive b2 and the third additive c2 to the first additive is too small, the negative electrode film formation effect is not significantly improved, and the high temperature storage and high temperature cycle performance of the battery are reduced; if the ratio is too large, the battery impedance increases and the low temperature discharge performance is reduced.
比较实施例2.1、2.2、2.3和实施例2.4～2.10可以看出，通过对三种添加剂的含量a、b、c的值进行调控，尤其是当三者满足关系式1≤b+c≤2.5；0.5≤b/c≤7.5；1≤(b+c)/a≤12.5时，能够进一步综合提升电池阻抗、高温存储及高温循环性能。By comparing Examples 2.1, 2.2, 2.3 and Examples 2.4 to 2.10, it can be seen that by regulating the values of the contents a, b, and c of the three additives, especially when the three satisfy the relationship 1≤b+c≤2.5; 0.5≤b/c≤7.5; 1≤(b+c)/a≤12.5, the battery impedance, high temperature storage and high temperature cycle performance can be further comprehensively improved.
比较实施例2.2和实施例2.11～2.21可以看出，化合物A1、A2、A3，化合物II-1、II-2、II-3、II-4、II-5、II-6及化合物III-1、III-2、III-3、III-4、III-5均具有所代表的添加剂的功能，可以替换使用。By comparing Example 2.2 with Examples 2.11 to 2.21, it can be seen that compounds A1, A2, A3, compounds II-1, II-2, II-3, II-4, II-5, II-6 and compounds III-1, III-2, III-3, III-4, III-5 all have the functions of the additives they represent and can be used interchangeably.
根据上表8和9可知，比较实施例2.2和实施例2.22-2.24可以看出，第一添加剂、第二添加剂b2和第三添加剂c2进一步与碳酸亚乙烯酯联用，能够进一步降低初始阻抗，改善电池高低温性能。According to Tables 8 and 9 above, by comparing Example 2.2 with Examples 2.22-2.24, it can be seen that the first additive, the second additive b2 and the third additive c2 are further used in combination with vinylene carbonate to further reduce the initial impedance and improve the high and low temperature performance of the battery.
根据上表8-10可知，比较实施例2.2、实施例2.22-2.24和实施例2.25-2.28可以看出，第一添加剂、第二添加剂b2和第三添加剂c2进一步与硫酸乙烯酯、碳酸亚乙烯酯、二氟磷酸锂、双氟磺酰亚胺锂、氟代碳酸乙烯酯联用，可进一步降低初始阻抗，改善电池高低温性能。According to Tables 8-10 above, by comparing Example 2.2, Examples 2.22-2.24 and Examples 2.25-2.28, it can be seen that the first additive, the second additive b2 and the third additive c2 are further used in combination with vinyl sulfate, vinylene carbonate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide and fluoroethylene carbonate to further reduce the initial impedance and improve the high and low temperature performance of the battery.
本发明的第三方面提供包含焦硫酸根三氟化硼复合锂盐和腈类化合物的电解液。 A third aspect of the present invention provides an electrolyte solution comprising a pyrosulfate boron trifluoride lithium complex salt and a nitrile compound.
本发明第三方面实施例和对比例中，第一添加剂的种类包括如下几种：In the embodiments and comparative examples of the third aspect of the present invention, the types of the first additive include the following:
第一添加剂A1：含95wt％化合物I-1和5wt％化合物I-2；The first additive A1: contains 95 wt% of compound I-1 and 5 wt% of compound I-2;
第一添加剂A2：含90wt％化合物I-1、6wt％化合物I-2和4wt％化合物I-3。The first additive A2 contains 90 wt % of compound I-1, 6 wt % of compound I-2 and 4 wt % of compound I-3.
一、电解液制备1. Preparation of electrolyte
在充满氩气的手套箱(水分＜5ppm，氧分＜10ppm)中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、丙酸丙酯(PP)、碳酸二乙酯(DEC)、氟代碳酸乙烯酯(FEC)按质量比1.5:1.5:3:1:1混合形成有机溶剂，基于所述电解液总质量，加入LiPF6质量百分比为14％，作为基础电解液M进行使用。In a glove box filled with argon (water content <5ppm, oxygen content <10ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) were mixed in a mass ratio of 1.5:1.5:3:1:1 to form an organic solvent, and LiPF6 was added in a mass percentage of 14% based on the total mass of the electrolyte for use as a basic electrolyte M.
在上述基础电解液M中定量加入第一添加剂、第二添加剂b3和其他添加剂，混合均匀形成电解液，其中第一添加剂和第二添加剂b3中CN官能团的质量比值记作a，CN官能团在第二添加剂b3中的质量含量记作CN％，具体电解液配方如下表11所示：The first additive, the second additive b3 and other additives are quantitatively added to the above-mentioned basic electrolyte M, and mixed evenly to form an electrolyte, wherein the mass ratio of the CN functional groups in the first additive and the second additive b3 is recorded as a, and the mass content of the CN functional groups in the second additive b3 is recorded as CN%. The specific electrolyte formula is shown in Table 11 below:
表11高电压电解液配方表1

Table 11 High voltage electrolyte formula Table 1

在基础电解液M中定量加入乙酸2,2-二氟乙酯(DFEA)、第一添加剂、第二添加剂b3和其它添加剂，混合均匀形成电解液，具体电解液配方如下表12所示：2,2-difluoroethyl acetate (DFEA), the first additive, the second additive b3 and other additives are quantitatively added to the basic electrolyte M, and mixed evenly to form an electrolyte. The specific electrolyte formula is shown in Table 12 below:
表12高电压电解液配方表2
Table 12 High voltage electrolyte formula Table 2
二、电化学性能测试2. Electrochemical performance test
本发明所采用的电解液配方通过第一添加剂和第二添加剂b3二者共同使用，解决了高电压正极电解液界面稳定性差的问题，同时提升了腈类化合物与负极界面的兼容性问题，适用于钴酸锂/石墨，钴酸锂/硅碳，三元/石墨，三元/硅碳，磷酸锰铁锂/石墨等体系。本实施例仅是优选了钴酸锂/石墨体系进行性能测试。The electrolyte formula adopted in the present invention solves the problem of poor interface stability of high-voltage positive electrode electrolyte by using the first additive and the second additive b3 together, and at the same time improves the compatibility of nitrile compounds with the negative electrode interface, and is suitable for lithium cobalt oxide/graphite, lithium cobalt oxide/silicon carbon, ternary/graphite, ternary/silicon carbon, lithium manganese iron phosphate/graphite and other systems. This embodiment only selects the lithium cobalt oxide/graphite system for performance testing.
将上述实施例和对比例的锂离子电池电解液分别装入容量1000mAh的软包锂离子电池，所述锂离子动力电池包括正极极片、负极极片、隔膜、电解液以及电池辅料，正极活性材料为LiCoO2，负极活性材料为石墨。The lithium ion battery electrolytes of the above examples and comparative examples were respectively loaded into soft-pack lithium ion batteries with a capacity of 1000 mAh. The lithium ion power battery comprises a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and battery auxiliary materials. The positive electrode active material is LiCoO 2 , and the negative electrode active material is graphite.
制备过程如下：将正极极片、隔膜和负极极片一起卷绕成卷芯，用铝塑膜进行密封后进行烘烤使得电极水分满足要求，烘烤后电芯进行电解液注液，经静置、化成、分容、老化工序得成品软包电芯。The preparation process is as follows: the positive electrode sheet, the separator and the negative electrode sheet are wound together into a core, which is sealed with an aluminum-plastic film and then baked so that the moisture content of the electrode meets the requirements. After baking, the battery cell is injected with electrolyte, and the finished soft-pack battery cell is obtained through the steps of standing, forming, capacity separation and aging.
对上述锂离子电池各项性能进行测试，包括：The above lithium-ion batteries are tested for various performances, including:
(1)循环性能测试(1) Cyclic performance test
在规定温度下以1C的电流恒流充电至充电截止电压(4.50V，下同)，然后恒压充电至电流下降至0.1C，然后以1C的电流恒流放电至放电截止电压(3.0V，下同)，如此循环特定周数，记录第1周的放电容量和最后1周的放电容量，按下式计算电池循环的容量保持率：
容量保持率＝最后1周的放电容量/第1周的放电容量*100％。At the specified temperature, charge at a constant current of 1C to the charge cut-off voltage (4.50V, the same below), then charge at a constant voltage until the current drops to 0.1C, then discharge at a constant current of 1C to the discharge cut-off voltage (3.0V, the same below), and repeat this cycle for a specific number of weeks. Record the discharge capacity of the first week and the discharge capacity of the last week, and calculate the capacity retention rate of the battery cycle as follows:
Capacity retention rate = discharge capacity in the last week/discharge capacity in the first week*100%.
(2)85℃高温存储性能测试 (2) 85℃ high temperature storage performance test
室温下以1C的电流恒流充电至充电截止电压，并恒压充电至电流下降至0.1C，随后在85℃恒温烘箱贮存12h(小时)。记录高温存储前后的体积变化率和容量恢复率。At room temperature, the battery was charged at a constant current of 1C to the charge cut-off voltage, and then charged at a constant voltage until the current dropped to 0.1C, and then stored in a constant temperature oven at 85°C for 12 hours. The volume change rate and capacity recovery rate before and after high-temperature storage were recorded.
(3)-20℃低温放电容量(3) -20℃ low temperature discharge capacity
室温下以0.5C的电流恒流充电至充电截止电压，然后恒压充电至电流下降至0.1C，然后在-20℃下以0.5C的电流恒流放电至放电截止电压，记录低温下的放电容量。低温容量保持率＝低温下的放电容量/第1周的放电容量*100％。At room temperature, charge at a constant current of 0.5C to the charge cut-off voltage, then charge at a constant voltage until the current drops to 0.1C, then discharge at a constant current of 0.5C at -20°C to the discharge cut-off voltage, and record the discharge capacity at low temperature. Low temperature capacity retention rate = discharge capacity at low temperature / discharge capacity in the first week * 100%.
(3)初始ACR阻抗(3) Initial ACR impedance
室温下，以标准充电电流将电池容量调整至50％SOC(荷电状态)，采用日本日置内阻仪对分容后的锂电池的固定极耳位置测试1KHz频率下的内阻(mΩ)，记作初始ACR阻抗(交流内阻)。At room temperature, the battery capacity was adjusted to 50% SOC (state of charge) with a standard charging current, and the internal resistance (mΩ) at a frequency of 1KHz was tested at the fixed ear position of the lithium battery after capacity division using a Japanese Hioki internal resistance meter, which was recorded as the initial ACR impedance (AC internal resistance).
测试结果如下表13所示：The test results are shown in Table 13 below:
表13 LCO/AG-4.5V电化学测试结果(4.50V-3.0V)

Table 13 LCO/AG-4.5V electrochemical test results (4.50V-3.0V)

根据上表13数据，比较实施例3.2和对比例3.1～3.2可知，第一添加剂和第二添加剂b3联用后，相比两者单独使用，在钴酸锂高电压体系中，能够抑制电芯超高温85℃存储12h后的产气膨胀并提升电池的容量恢复率，同时有效提升电芯的-20℃低温放电性能，提升高电压高温循环性能。According to the data in Table 13 above, by comparing Example 3.2 with Comparative Examples 3.1 to 3.2, it can be seen that the combined use of the first additive and the second additive b3 , compared with the use of either alone, can inhibit the gas expansion of the battery cell after storage at ultra-high temperature of 85°C for 12 hours in a lithium cobalt oxide high voltage system and improve the capacity recovery rate of the battery, while effectively improving the -20°C low temperature discharge performance of the battery cell and the high voltage and high temperature cycle performance.
进一步比较实施例3.19～3.22和对比例3.4～3.7可知，第一添加剂和第二添 加剂b3中CN官能团的质量比值在0.03～4.0区间内，且第一添加剂在电解液中的添加量满足0.05～5.0wt％，第二添加剂b3满足0.5～10wt％，电池高电压下的高温存储和循环性能得到有效提升，同时电池具有较优的-20℃低温放电容量。同时在配制对比例7电解液时，当第二添加剂b3中SN含量达到12％时，电解液出现少量白色晶体，这是由于LiPF6与SN发生反应析出，进一步佐证第二添加剂b3含量建议不超过10.0wt％。进一步比较实施例3.26～3.29，第一添加剂和第二添加剂b3中CN官能团的质量比值优选为0.1～0.3。当不能同时满足上述条件时，无法达成上述电池高低温综合性能的提升。Further comparison of Examples 3.19 to 3.22 and Comparative Examples 3.4 to 3.7 shows that the first additive and the second additive The mass ratio of CN functional groups in additive b3 is in the range of 0.03 to 4.0, and the addition amount of the first additive in the electrolyte satisfies 0.05 to 5.0wt%, and the second additive b3 satisfies 0.5 to 10wt%, and the high temperature storage and cycle performance of the battery under high voltage are effectively improved, and the battery has a relatively good low temperature discharge capacity of -20°C. At the same time, when the electrolyte of comparative example 7 is prepared, when the SN content in the second additive b3 reaches 12%, a small amount of white crystals appear in the electrolyte, which is due to the reaction and precipitation of LiPF6 and SN, further proving that the content of the second additive b3 is recommended not to exceed 10.0wt%. Further comparing Examples 3.26 to 3.29, the mass ratio of CN functional groups in the first additive and the second additive b3 is preferably 0.1 to 0.3. When the above conditions cannot be met at the same time, the improvement of the above-mentioned high and low temperature comprehensive performance of the battery cannot be achieved.
进一步比较实施例3.8、3.19及实施例3.22、3.23，在第一添加剂和第二添加剂b3满足合适用量的基础上，进一步加入含硫氧双键的第三添加剂c3，可以在正负极表面成膜，所形成的含四价或六价等高价态的烷基硫酸锂可提高正极界面的耐氧化性能，同时具有高的锂离子传导性，第三添加剂c3与第一添加剂协同作用，形成有机无机复合的SEI膜，尤其是在第一添加剂与第二添加剂b3中CN官能团的质量比值低于1.0时，第三添加剂c3的引入更有效抑制CN对负极界面的破坏，提升电池的存储和循环性能。Further comparing Examples 3.8, 3.19 with Examples 3.22, 3.23, on the basis of the first additive and the second additive b3 satisfying the appropriate dosage, a third additive c3 containing a sulfur-oxygen double bond is further added, which can form a film on the surface of the positive and negative electrodes, and the formed alkyl lithium sulfate containing a high valence state such as tetravalent or hexavalent can improve the oxidation resistance of the positive electrode interface, and at the same time has high lithium ion conductivity. The third additive c3 and the first additive act synergistically to form an organic-inorganic composite SEI film. Especially when the mass ratio of the CN functional groups in the first additive and the second additive b3 is lower than 1.0, the introduction of the third additive c3 can more effectively inhibit the damage of CN to the negative electrode interface and improve the storage and cycle performance of the battery.
比较实施例3.19和3.30～3.34，在第一添加剂、第二添加剂b3和第三添加剂c3联用基础上，使用含氟溶剂(DFEA)，可进一步提升电池低温放电性能，并兼顾循环性能。但DFEA存在劣化高温存储产气的风险，通过进一步使用抑制产气添加剂TVS，可有效兼顾高低温性能。Comparing Examples 3.19 and 3.30-3.34, the use of a fluorinated solvent (DFEA) based on the combined use of the first additive, the second additive b 3 and the third additive c 3 can further improve the low-temperature discharge performance of the battery while taking into account the cycle performance. However, DFEA has the risk of deteriorating gas production during high-temperature storage. By further using the gas production inhibitor TVS, high and low temperature performance can be effectively taken into account.
比较实施例3.19和对比例3.8～3.9，采用第一添加剂、第二添加剂b3和第三添加剂c3联用，相比LiDFOB或LiPO2F2与第二添加剂b3、第三添加剂c3联用，更有助于抑制在高温长周期存储中的产气膨胀，降低软包电池鼓胀引发的电池安全风险。Comparing Example 3.19 with Comparative Examples 3.8 to 3.9, the combined use of the first additive, the second additive b 3 and the third additive c 3 is more helpful in suppressing gas expansion during high-temperature long-period storage and reducing the battery safety risk caused by swelling of the soft-pack battery than the combined use of LiDFOB or LiPO 2 F 2 with the second additive b 3 and the third additive c 3.
三、电池化成后电解液主份的残余量分析3. Analysis of the residual amount of the main electrolyte after battery formation
采用离心法取化成后(0％SOC)钴酸锂电芯中的电解液，经稀硝酸酸化、过滤后取滤液，经气相色谱质谱联用仪测量电解液中的主要成分及含量，测试结果如下： The electrolyte in the formed (0% SOC) lithium cobalt oxide battery cell was obtained by centrifugation, acidified with dilute nitric acid, filtered, and the filtrate was taken. The main components and contents in the electrolyte were measured by gas chromatography-mass spectrometry. The test results are as follows:
表14添加剂在电池化成前后及存储后的残留量
Table 14 Residual amount of additives before and after battery formation and storage
根据上表14结果可知，在不含第三添加剂PS的情况下，实施例3.1中第一添加剂和第二添加剂b3随着电池化成和循环逐渐消耗，推测第一添加剂和第二添加剂b3分别参与正负极表界面修饰，提升高电压电池的循环稳定性。相比于实施例3.1，实施例3.19中提升了第二添加剂b3的含量至3％及引入第三添加剂PS后，第一添加剂在循环过程中消耗量降低，推测第二添加剂b3和第三添加剂c3与第一添加剂发生协同效应，提升了电极界面的稳定性，相比于实施例3.1，更有助于提升全电池的循环性能。 According to the results in Table 14 above, in the absence of the third additive PS, the first additive and the second additive b3 in Example 3.1 are gradually consumed as the battery is formed and cycled. It is speculated that the first additive and the second additive b3 participate in the modification of the positive and negative electrode surfaces, respectively, to improve the cycle stability of the high-voltage battery. Compared with Example 3.1, in Example 3.19, the content of the second additive b3 is increased to 3% and the third additive PS is introduced. The consumption of the first additive during the cycle is reduced. It is speculated that the second additive b3 and the third additive c3 have a synergistic effect with the first additive, which improves the stability of the electrode interface. Compared with Example 3.1, it is more helpful to improve the cycle performance of the full battery.

Claims (40)

  1. 一种高能量密度电池电解液，包括主锂盐、非水溶剂，其特征在于：所述电解液包括：A high energy density battery electrolyte, comprising a main lithium salt and a non-aqueous solvent, characterized in that the electrolyte comprises:
    第一添加剂，所述第一添加剂选自下述焦硫酸根三氟化硼复合锂盐中的至少一种，在电解液中的质量百分含量为A％，且0.1≤A≤15.0；

    A first additive, wherein the first additive is selected from at least one of the following pyrosulfate boron trifluoride composite lithium salts, and the mass percentage content in the electrolyte is A%, and 0.1≤A≤15.0;

    且，化合物(I-1)占第一添加剂质量百分含量的至少80％以上；Moreover, the compound (I-1) accounts for at least 80% of the mass percentage of the first additive;
    第二添加剂b1，所述第二添加剂b1为1,3-丙磺酸内酯和/或硫酸乙烯酯，在电解液中的质量百分含量为B％，且0.1≤B≤5.0。The second additive b 1 is 1,3-propane sultone and/or vinyl sulfate, and the mass percentage of the second additive b 1 in the electrolyte is B%, and 0.1≤B≤5.0.
  2. 根据权利要求1所述的高能量密度电池电解液，其特征在于：
    0.2≤A≤3.0；
    0.2≤B≤3.0。    The high energy density battery electrolyte according to claim 1, characterized in that:
    0.2≤A≤3.0;
    0.2≤B≤3.0.
  3. 根据权利要求2所述的高能量密度电池电解液，其特征在于：1.0≤A+B≤4.0。The high energy density battery electrolyte according to claim 2 is characterized in that: 1.0≤A+B≤4.0.
  4. 根据权利要求1-3任一所述的高能量密度电池电解液，其特征在于：所述电解液还包括：第三添加剂c1，所述第三添加剂c1为碳酸亚乙烯酯，在电解液中的质量百分含量为C％，且0.1≤C≤5.0。The high energy density battery electrolyte according to any one of claims 1-3, characterized in that: the electrolyte further comprises: a third additive c1 , the third additive c1 is vinylene carbonate, the mass percentage content of the third additive c1 in the electrolyte is C%, and 0.1≤C≤5.0.
  5. 根据权利要求4所述的高能量密度电池电解液，其特征在于：0.2≤C≤3.0。The high energy density battery electrolyte according to claim 4 is characterized in that: 0.2≤C≤3.0.
  6. 根据权利要求4或5所述的高能量密度电池电解液，其特征在于：0.25≤C/(A+B)≤4.0。The high energy density battery electrolyte according to claim 4 or 5 is characterized in that: 0.25≤C/(A+B)≤4.0.
  7. 根据权利要求1-6任一所述的高能量密度电池电解液，其特征在于：所述电解液还包括基础添加剂，所述基础添加剂选自氟代碳酸乙烯酯、乙烯基碳酸乙烯酯、三(三甲基硅基)磷酸酯、二氟磷酸锂、双氟磺酰亚胺锂、丁二酸酐、已二腈、环己基苯、双草酸二氟磷酸锂或二氟草酸硼酸锂中的至少一种，任意一种基础添加剂在电解液中的质量百分含量为0.1～5.0％。The high energy density battery electrolyte according to any one of claims 1 to 6, characterized in that: the electrolyte further comprises a basic additive, the basic additive is selected from at least one of fluoroethylene carbonate, vinylethylene carbonate, tris(trimethylsilyl) phosphate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, succinic anhydride, adiponitrile, cyclohexylbenzene, lithium difluorobis(oxalate)phosphate or lithium difluorobis(oxalate)borate, and the mass percentage of any one of the basic additives in the electrolyte is 0.1 to 5.0%.
  8. 根据权利要求1所述的高能量密度电池电解液，其特征在于：所述主锂盐选自六氟磷酸锂、四氟硼酸锂、六氟砷酸锂、高氯酸锂、双草酸硼酸锂、二氟草酸硼酸锂、双氟磺酰亚胺锂、双三氟甲基磺酰亚胺锂、四氟草酸磷酸锂、三草酸磷酸锂或二氟双草酸磷酸锂中的至少一种，且其摩尔浓度为0.1～4.0mol/L；The high energy density battery electrolyte according to claim 1, characterized in that: the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium tetrafluorooxalate phosphate, lithium trioxalate phosphate or lithium difluorobis(oxalate) phosphate, and its molar concentration is 0.1 to 4.0 mol/L;
    所述非水溶剂选自C3～C6碳酸酯类化合物、C3～C8羧酸酯类化合物、砜类化合物、醚类化合物中的至少一种。The non-aqueous solvent is selected from at least one of C3-C6 carbonate compounds, C3-C8 carboxylate compounds, sulfone compounds, and ether compounds.
  9. 一种高电压下兼顾高低温性能的电解液，所述电解液包括：主锂盐、非水溶剂和添加剂，其特征在于：所述添加剂包括：An electrolyte having both high and low temperature performance under high voltage, the electrolyte comprising: a main lithium salt, a non-aqueous solvent and an additive, wherein the additive comprises:
    第一添加剂，所述第一添加剂至少包括下式(I-1)所示结构的焦硫酸根三氟化硼复合锂盐：
    The first additive comprises at least a pyrosulfate boron trifluoride composite lithium salt having a structure shown in the following formula (I-1):
    第二添加剂b2，所述第二添加剂b2选自下式(IIA)和/或(IIB)所示结构的环状磺酸酯类化合物：
    The second additive b 2 is selected from the cyclic sulfonate compounds represented by the following formula (IIA) and/or (IIB):
    式中，R1、R2、R3、R4、R5、R6、R7、R8、R9、R10独立地选自氢、C1-C3烷基或卤素，m、n独立地选自1、2或3，且每个重复单元中，R5、R6、R9、R10选自相同或不同的取代基；wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 are independently selected from hydrogen, C1-C3 alkyl or halogen, m and n are independently selected from 1, 2 or 3, and in each repeating unit, R 5 , R 6 , R 9 , R 10 are selected from the same or different substituents;
    第三添加剂c2，所述第三添加剂c2为下式(III)所示结构的草酸根锂盐：
    The third additive c 2 is a lithium oxalate salt having a structure represented by the following formula (III):
    式(III)中，R11、R12独立地选自C1-C3烷基、C1-C3卤代烷基或卤素，R13选自直连键、C1-C3亚烷基或卤代C1-C3亚烷基，M选自硼原子或磷原子，p选自1或2；In formula (III), R 11 and R 12 are independently selected from C1-C3 alkyl, C1-C3 haloalkyl or halogen, R 13 is selected from a direct bond, C1-C3 alkylene or halogenated C1-C3 alkylene, M is selected from a boron atom or a phosphorus atom, and p is selected from 1 or 2;
    所述第一添加剂、第二添加剂b2和第三添加剂c2分别占电解液总质量的a％、b％与c％，且符合下述关系式：
    0.2≤b+c≤4；
    0.2≤b/c≤10；
    0.07≤(b+c)/a≤20。    The first additive, the second additive b2 and the third additive c2 account for a%, b% and c% of the total mass of the electrolyte respectively, and meet the following relationship:
    0.2≤b+c≤4;
    0.2≤b/c≤10;
    0.07≤(b+c)/a≤20.
  10. 根据权利要求9所述的高电压下兼顾高低温性能的电解液，其特征在于：所述第一添加剂、第二添加剂b2和第三添加剂c2的添加量满足下述关系式：
    1≤b+c≤2.5；
    0.5≤b/c≤7.5；
    1≤(b+c)/a≤12.5。    The electrolyte having both high and low temperature performance under high voltage according to claim 9 is characterized in that the addition amounts of the first additive, the second additive b2 and the third additive c2 satisfy the following relationship:
    1≤b+c≤2.5;
    0.5≤b/c≤7.5;
    1≤(b+c)/a≤12.5.
  11. 根据权利要求9或10所述的高电压下兼顾高低温性能的电解液，其特征在于：所述第一添加剂、第二添加剂b2和第三添加剂c2的添加量满足下述关系式：
    0.2≤a≤3；
    0.1≤b≤2.5；
    0.1≤c≤2.5。    The electrolyte having both high and low temperature performance under high voltage according to claim 9 or 10 is characterized in that the addition amounts of the first additive, the second additive b2 and the third additive c2 satisfy the following relationship:
    0.2≤a≤3;
    0.1≤b≤2.5;
    0.1≤c≤2.5.
  12. 根据权利要求9所述的高电压下兼顾高低温性能的电解液，其特征在于：所述第一添加剂还包括下式(I-2)、(I-3)、(I-4)、(I-5)、(I-6)所示化合物中的至少一种：

    The electrolyte having both high and low temperature performance under high voltage according to claim 9 is characterized in that: the first additive further comprises at least one of the compounds represented by the following formulas (I-2), (I-3), (I-4), (I-5), and (I-6):

    且第一添加剂中至少包含80wt％以上的所述式(I-1)所示结构的焦硫酸根三氟化硼复合锂盐。The first additive contains at least 80 wt % of the pyrosulfate boron trifluoride composite lithium salt having the structure represented by formula (I-1).
  13. 根据权利要求12所述的高电压下兼顾高低温性能的电解液，其特征在于：第一添加剂中包含80～95wt％的所述式(I-1)所示结构的焦硫酸根三氟化 硼复合锂盐，其余为化合物(I-2)、(I-3)、(I-4)、(I-5)或(I-6)中的至少一种。The electrolyte having both high and low temperature performance under high voltage according to claim 12 is characterized in that: the first additive contains 80 to 95 wt% of the pyrosulfate trifluoride having the structure represented by formula (I-1) boron complex lithium salt, and the rest is at least one of compounds (I-2), (I-3), (I-4), (I-5) or (I-6).
  14. 根据权利要求9所述的高电压下兼顾高低温性能的电解液，其特征在于：所述第二添加剂b2中，R1、R2、R3、R4、R5、R6、R7、R8、R9、R10独立地选自氢、甲基、乙基或卤素，m、n独立地选自1或2，且每个重复单元中，R5、R6、R9、R10选自相同或不同的取代基。The electrolyte having both high and low temperature performance under high voltage according to claim 9, characterized in that: in the second additive b2 , R1 , R2 , R3 , R4 , R5 , R6 , R7 , R8 , R9 , R10 are independently selected from hydrogen, methyl, ethyl or halogen, m and n are independently selected from 1 or 2, and in each repeating unit, R5 , R6 , R9 , R10 are selected from the same or different substituents.
  15. 根据权利要求14所述的高电压下兼顾高低温性能的电解液，其特征在于：所述第二添加剂b2选自下述结构所示的环状磺酸酯类化合物中的至少一种：
    The electrolyte having both high and low temperature performance under high voltage according to claim 14, characterized in that: the second additive b2 is selected from at least one of the cyclic sulfonate compounds represented by the following structures:
  16. 根据权利要求9所述的高电压下兼顾高低温性能的电解液，其特征在于：所述第三添加剂c2选自下述结构所示的草酸根锂盐中的至少一种：
    The electrolyte having both high and low temperature performance under high voltage according to claim 9, characterized in that: the third additive C2 is selected from at least one of the lithium oxalate salts shown in the following structures:
  17. 根据权利要求9-16任一所述的高电压下兼顾高低温性能的电解液，其特征在于：所述添加剂还包括第四添加剂d2，所述第四添加剂d2为碳酸亚乙烯酯，在电解液中的质量百分含量为0.1～5wt％。The electrolyte with both high and low temperature performance under high voltage according to any one of claims 9 to 16, characterized in that the additive further comprises a fourth additive d2 , wherein the fourth additive d2 is vinylene carbonate, and the mass percentage content in the electrolyte is 0.1-5wt%.
  18. 根据权利要求17所述的高电压下兼顾高低温性能的电解液，其特征在于：所述添加剂还包括基础添加剂，所述基础添加剂选自硫酸酯类化合物、氟代碳酸酯类化合物或含氟锂盐类化合物中的至少一种，用量占电解液总质量的0.1～5.0wt％；The electrolyte having high and low temperature performance under high voltage according to claim 17, characterized in that: the additive further comprises a basic additive, the basic additive is selected from at least one of a sulfate ester compound, a fluorinated carbonate compound or a fluorinated lithium salt compound, and the amount thereof accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte;
    所述硫酸酯类化合物选自硫酸乙烯酯、季戊四醇双环硫酸酯、4,4'-联硫酸乙烯酯或4-甲基-硫酸乙烯酯中的至少一种；The sulfate compound is selected from at least one of vinyl sulfate, pentaerythritol bicyclic sulfate, 4,4'-disulfate or 4-methyl-vinyl sulfate;
    所述氟代碳酸酯类化合物选自氟代碳酸乙烯酯、双氟代碳酸乙烯酯、三氟甲基碳酸丙烯酯中的至少一种；The fluorinated carbonate compound is selected from at least one of fluoroethylene carbonate, difluoroethylene carbonate, and trifluoromethylpropylene carbonate;
    含氟锂盐类化合物选自二氟磷酸锂、四氟硼酸锂、双氟磺酰亚胺锂、双三氟甲基磺酰亚胺锂、四氟草酸磷酸锂、二氟双草酸磷酸锂、二氟草酸硼酸锂、三草酸磷酸锂或下式(IV)所示锂盐中至少一种，且所述含氟锂盐类化合物不同于主锂盐：
    The fluorine-containing lithium salt compound is selected from at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate) phosphate, lithium difluorooxalate borate, lithium trioxalate phosphate or the lithium salt represented by the following formula (IV), and the fluorine-containing lithium salt compound is different from the main lithium salt:
    式(IV)中，y+z＝4，且y≥0且z≥1，y、z为正整数。In formula (IV), y+z=4, y≥0 and z≥1, and y and z are positive integers.
  19. 根据权利要求9所述的高电压下兼顾高低温性能的电解液，其特征在于：所述主锂盐选自六氟磷酸锂、四氟硼酸锂、六氟砷酸锂、高氯酸锂、双草酸硼酸锂、二氟草酸硼酸锂、双氟磺酰亚胺锂、双三氟甲基磺酰亚胺锂、四氟草酸磷酸锂、三草酸磷酸锂或二氟双草酸磷酸锂中的至少一种，且其摩尔浓度为0.1～4.0mol/L；The electrolyte having both high and low temperature performance under high voltage according to claim 9 is characterized in that: the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethylsulfonyl imide, lithium tetrafluorooxalatophosphate, lithium trioxalatophosphate or lithium difluorobisoxalatophosphate, and its molar concentration is 0.1 to 4.0 mol/L;
    所述非水溶剂选自碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、氟代碳酸乙烯 酯、二氟代碳酸乙烯酯、γ-丁内酯、乙酸甲酯、丙酸甲酯、丁酸甲酯、乙酸乙酯、丙酸乙酯、丁酸乙酯、乙酸丙酯、丙酸丙酯、环丁砜、二甲基亚砜、二甲基砜、二乙基砜、三甘醇二甲醚、四甘醇二甲醚或1,1,2,2-四氟乙基-2,2,3,3-四氟丙基醚中的至少一种。The non-aqueous solvent is selected from ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, fluoroethylene carbonate At least one of esters, difluoroethylene carbonate, γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate, propyl propionate, cyclopentane, dimethyl sulfoxide, dimethyl sulfone, diethyl sulfone, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.
  20. 一种锂离子二次电池，包括正极、隔膜和负极，其特征在于：所述锂离子二次电池还充注有权利要求9-19任一所述的电解液。A lithium ion secondary battery comprises a positive electrode, a separator and a negative electrode, wherein the lithium ion secondary battery is also filled with the electrolyte according to any one of claims 9 to 19.
  21. 根据权利要求20所述的锂离子二次电池，其特征在于：所述正极的活性材料包括：镍钴锰酸锂、钴酸锂、磷酸锰铁锂、尖晶石锰酸锂或镍锰酸锂，负极的活性材料选自石墨和/或硅负极材料。The lithium-ion secondary battery according to claim 20 is characterized in that the active material of the positive electrode includes: lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium iron manganese phosphate, spinel lithium manganese oxide or lithium nickel manganese oxide, and the active material of the negative electrode is selected from graphite and/or silicon negative electrode materials.
  22. 根据权利要求21所述的锂离子二次电池，其特征在于：镍钴锰酸锂选自NCM523、NCM622、NCM712、NCM811或NCM90505。The lithium-ion secondary battery according to claim 21, characterized in that the lithium nickel cobalt manganese oxide is selected from NCM523, NCM622, NCM712, NCM811 or NCM90505.
  23. 根据权利要求22所述的锂离子二次电池，其特征在于：所述锂离子二次电池的截止电压≥4.3V。The lithium-ion secondary battery according to claim 22, characterized in that the cut-off voltage of the lithium-ion secondary battery is ≥4.3V.
  24. 一种含新型锂盐的电解液添加剂组合物，其特征在于：所述添加剂组合物包括：An electrolyte additive composition containing a novel lithium salt, characterized in that the additive composition comprises:
    第一添加剂，所述第一添加剂至少包括下式(I-1)所示结构的新型锂盐：
    The first additive comprises at least a novel lithium salt having a structure represented by the following formula (I-1):
    第二添加剂b3，所述第二添加剂b3选自下式(IIC)所示结构的腈类化合物：
    The second additive b 3 is selected from the nitrile compounds represented by the following formula (IIC):
    式中，M1选自-CH、P或-P＝O，n选自0～5的整数；R14、R15、R16独立地选自直连键、氧、-R17-、-O-R17-或-R18-O-R17-，其中，R17、R18独立地选自C1‐C5亚烷基、C2‐C5亚烯基，或被C1‐C3烷基或氰基取代的C1‐C5亚烷基、C2‐C5亚烯基；In the formula, M1 is selected from -CH, P or -P=O, n is selected from an integer of 0 to 5; R14 , R15 , R16 are independently selected from a direct bond, oxygen, -R17- , -OR17- or -R18 - OR17- , wherein R17 , R18 are independently selected from C1-C5 alkylene, C2-C5 alkenylene, or C1-C5 alkylene or C2-C5 alkenylene substituted by C1-C3 alkyl or cyano;
    所述第一添加剂和第二添加剂b3中CN官能团的质量比值为0.03～4.0。The mass ratio of the CN functional groups in the first additive and the second additive b3 is 0.03 to 4.0.
  25. 根据权利要求24所述的含新型锂盐的电解液添加剂组合物，其特征在于：所述第一添加剂和第二添加剂b3中CN官能团的质量比值为0.08～1.0。The electrolyte additive composition containing a novel lithium salt according to claim 24, characterized in that the mass ratio of the CN functional groups in the first additive and the second additive b3 is 0.08 to 1.0.
  26. 根据权利要求24或25所述的含新型锂盐的电解液添加剂组合物，其特征在于：所述第一添加剂还包括下式(I-2)、(I-3)、(I-4)、(I-5)、(I-6)所示化合物中的至少一种：

    The electrolyte additive composition containing a novel lithium salt according to claim 24 or 25, characterized in that: the first additive further comprises at least one of the compounds represented by the following formulas (I-2), (I-3), (I-4), (I-5), and (I-6):

    且第一添加剂中至少包含80.0wt％以上的所述式(I-1)所示结构的新型锂盐。The first additive contains at least 80.0 wt % or more of the novel lithium salt having the structure represented by formula (I-1).
  27. 根据权利要求26所述的含新型锂盐的电解液添加剂组合物，其特征在于：第一添加剂中包含80.0～95.0wt％的所述式(I-1)所示结构的新型锂盐，其余为化合物(I-2)、(I-3)、(I-4)、(I-5)或(I-6)中的至少一种。The electrolyte additive composition containing a novel lithium salt according to claim 26, characterized in that the first additive contains 80.0 to 95.0 wt % of the novel lithium salt having the structure represented by formula (I-1), and the rest is at least one of compounds (I-2), (I-3), (I-4), (I-5) or (I-6).
  28. 根据权利要求24或25所述的含新型锂盐的电解液添加剂组合物，其特征在于：所述第二添加剂b3中，M1选自-CH、P或-P＝O，n选自0～3的整数；R14、R15、R16独立地选自直连键、氧、-R17-、-O-R17-或-R18-O-R17-，其中，R17、R18独立地选自C1‐C3亚烷基、C2‐C3亚烯基，或被C1‐C3烷基或氰基取代的C1‐C3亚烷基、C2‐C3亚烯基。The electrolyte additive composition containing a novel lithium salt according to claim 24 or 25, characterized in that: in the second additive b3 , M1 is selected from -CH, P or -P＝O, n is selected from an integer of 0 to 3; R14 , R15 , R16 are independently selected from a direct bond, oxygen, -R17- , -OR17- or -R18 - OR17- , wherein R17 and R18 are independently selected from C1-C3 alkylene, C2-C3 alkenylene, or C1-C3 alkylene or C2-C3 alkenylene substituted by C1-C3 alkyl or cyano.
  29. 根据权利要求28所述的含新型锂盐的电解液添加剂组合物，其特征在于：所述第二添加剂b3选自下述结构所示的腈类化合物中的至少一种：

    The electrolyte additive composition containing a novel lithium salt according to claim 28, characterized in that the second additive b3 is selected from at least one of the nitrile compounds represented by the following structures:

  30. 一种电解液的配制方法，其特征在于：所述配制方法包括：在非水溶剂中加入主锂盐至主锂盐占电解液总质量的8～20wt％，再加入权利要求24-29任一所述的添加剂组合物获得电解液，并使得所述第一添加剂占电解液总质量的0.01～5.0wt％，第二添加剂b3占电解液总质量的0.5～10wt％；A method for preparing an electrolyte, characterized in that: the preparation method comprises: adding a main lithium salt to a non-aqueous solvent until the main lithium salt accounts for 8-20wt% of the total mass of the electrolyte, and then adding the additive composition described in any one of claims 24-29 to obtain an electrolyte, and making the first additive account for 0.01-5.0wt% of the total mass of the electrolyte, and the second additive b3 accounts for 0.5-10wt% of the total mass of the electrolyte;
    所述非水溶剂选自环状碳酸酯和线性碳酸酯和/或线性羧酸酯的混合物，所述环状碳酸酯选自碳酸乙烯酯、碳酸丙烯酯或氟代碳酸乙烯酯中的至少一种；所述线性碳酸酯选自碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯或甲基三氟乙基碳酸酯中的至少一种；所述线性羧酸酯选自乙酸乙酯、丙酸乙酯、丙酸丙酯、乙酸2,2-二氟乙酯或乙酸2,2,2-三氟乙酯中的至少一种，任一非水溶剂的用量占电解液总质量的0.1～50wt％；The non-aqueous solvent is selected from a mixture of cyclic carbonates and linear carbonates and/or linear carboxylates, the cyclic carbonate is selected from at least one of ethylene carbonate, propylene carbonate or fluoroethylene carbonate; the linear carbonate is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate or methyl trifluoroethyl carbonate; the linear carboxylate is selected from at least one of ethyl acetate, ethyl propionate, propyl propionate, 2,2-difluoroethyl acetate or 2,2,2-trifluoroethyl acetate, and the amount of any non-aqueous solvent is 0.1-50wt% of the total mass of the electrolyte;
    所述主锂盐选自六氟磷酸锂、双氟磺酰亚胺锂或双三氟甲基磺酰亚胺锂中的至少一种。The main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.
  31. 根据权利要求30所述的电解液的配制方法，其特征在于：所述第一添加剂占电解液总质量的0.1～2.0wt％，第二添加剂b3占电解液总质量的2.0～6.0wt％。The method for preparing an electrolyte according to claim 30 is characterized in that the first additive accounts for 0.1 to 2.0 wt% of the total mass of the electrolyte, and the second additive b3 accounts for 2.0 to 6.0 wt% of the total mass of the electrolyte.
  32. 根据权利要求30所述的电解液的配制方法，其特征在于：在所述电解液中加入第三添加剂c3，所述第三添加剂c3选自下述结构所示的硫氧双键化合物中的至少一种，用量占电解液总质量的0.5～5.0wt％：

    The method for preparing an electrolyte according to claim 30, characterized in that: a third additive C3 is added to the electrolyte, wherein the third additive C3 is selected from at least one of the sulfur-oxygen double bond compounds shown in the following structures, and the amount used accounts for 0.5-5.0wt% of the total mass of the electrolyte:

  33. 根据权利要求30-32任一所述的电解液的配制方法，其特征在于：在所述电解液中加入基础添加剂，所述基础添加剂选自氟代碳酸乙烯酯、碳酸亚乙烯酯、二氟磷酸锂、四氟硼酸锂、二氟草酸硼酸锂、二氟双草酸磷酸锂、三(三甲基硅基)磷酸酯、三(三甲基硅基)硼酸酯中的至少一种，任一添加量占电解液总质量的0.1～2.0wt％。The method for preparing an electrolyte according to any one of claims 30 to 32, characterized in that a basic additive is added to the electrolyte, wherein the basic additive is selected from at least one of fluoroethylene carbonate, vinylene carbonate, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium difluorobisoxalatophosphate, tris(trimethylsilyl)phosphate, and tris(trimethylsilyl)borate, and any addition amount accounts for 0.1 to 2.0 wt% of the total mass of the electrolyte.
  34. 根据权利要求33所述的电解液的配制方法，其特征在于：在所述电解液中加入第四添加剂d3，所述第四添加剂d3选自四乙烯基硅烷、2,4,6-三(烯丙氧基)-1,3,5-三嗪、1,3,5-三烯丙基异氰脲酸酯、1,3-二氧六环、1,4-二氧六环中的至少一种，任一添加量占电解液总质量的0.1～2.0wt％。The method for preparing an electrolyte according to claim 33 is characterized in that a fourth additive d3 is added to the electrolyte, and the fourth additive d3 is selected from at least one of tetravinylsilane, 2,4,6-tri(allyloxy)-1,3,5-triazine, 1,3,5-triallyl isocyanurate, 1,3-dioxane, and 1,4-dioxane, and any addition amount accounts for 0.1 to 2.0 wt% of the total mass of the electrolyte.
  35. 一种锂离子二次电池，包括正极极片、负极极片和隔膜，其特征在于：所述锂离子二次电池通过以下方法制备获得：将正极极片、隔膜和负极极片一起卷绕成卷芯，用铝塑膜密封后进行烘烤，之后向其注入权利要求30-34任一所述配制方法配制获得的电解液，经静置、化成、分容、老化后获得锂离子二次电池。A lithium-ion secondary battery comprises a positive electrode sheet, a negative electrode sheet and a separator, characterized in that the lithium-ion secondary battery is prepared by the following method: the positive electrode sheet, the separator and the negative electrode sheet are wound together into a winding core, sealed with an aluminum-plastic film and then baked, and then an electrolyte prepared by any preparation method described in claims 30-34 is injected therein, and the lithium-ion secondary battery is obtained after standing, forming, volume separation and aging.
  36. 根据权利要求35所述的锂离子二次电池，其特征在于：所述正极极片的活性材料选自钴酸锂、镍锰酸锂、富锂锰基、锰酸锂、磷酸铁锂、磷酸锰铁锂或LiNixCoyMnzL(1-x-y-z)O2,其中，L为Al、Sr、Mg、Ti、Ca、Zr、Zn、Si、W或Fe，0≤x≤1，0≤y≤1，0≤z≤1,0.5≤x+y+z≤1，负极极片的活性材料选自石墨、硅碳或硅氧材料。The lithium-ion secondary battery according to claim 35 is characterized in that the active material of the positive electrode plate is selected from lithium cobalt oxide, lithium nickel manganese oxide, lithium-rich manganese base, lithium manganese oxide, lithium iron phosphate, lithium iron manganese phosphate or LiNi x Co y Mn z L (1-xyz) O 2 , wherein L is Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, W or Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0.5≤x+y+z≤1, and the active material of the negative electrode plate is selected from graphite, silicon carbon or silicon oxygen material.
  37. 根据权利要求36所述的锂离子二次电池，其特征在于：所述正极极片 的活性材料包含LiCoO2。The lithium-ion secondary battery according to claim 36, characterized in that: the positive electrode sheet The active material comprises LiCoO 2 .
  38. 根据权利要求37所述的锂离子二次电池，其特征在于：所述锂离子二次电池的截止电压≥4.45V。The lithium-ion secondary battery according to claim 37 is characterized in that the cut-off voltage of the lithium-ion secondary battery is ≥4.45V.
  39. 根据权利要求38所述的锂离子二次电池，其特征在于：电解液添加剂在电池化成过程中参与电极/电解液界面构建，使得在锂离子二次电池的电解液液体中，第一添加剂占电解液液体总质量的0.01～2.0wt％，第二添加剂b3占电解液液体总质量的0.1～9.0wt％。The lithium-ion secondary battery according to claim 38 is characterized in that the electrolyte additive participates in the construction of the electrode/electrolyte interface during the battery formation process, so that in the electrolyte liquid of the lithium-ion secondary battery, the first additive accounts for 0.01 to 2.0 wt% of the total mass of the electrolyte liquid, and the second additive b3 accounts for 0.1 to 9.0 wt% of the total mass of the electrolyte liquid.
  40. 根据权利要求39所述的锂离子二次电池，其特征在于：第三添加剂c3占电解液液体总质量的0.1～4.5wt％，第四添加剂d3占电解液液体总质量的0.02～1.5wt％。 The lithium ion secondary battery according to claim 39 is characterized in that the third additive c3 accounts for 0.1 to 4.5 wt% of the total mass of the electrolyte liquid, and the fourth additive d3 accounts for 0.02 to 1.5 wt% of the total mass of the electrolyte liquid.
PCT/CN2023/136137 2022-12-09 2023-12-04 Electrolyte solution comprising pyrosulfate-boron trifluoride composite lithium salt, and lithium-ion secondary battery WO2024120338A1 (en)

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CN107799822A (en) * 2017-10-11 2018-03-13 珠海市赛纬电子材料股份有限公司 A kind of nonaqueous electrolytic solution of high-voltage lithium ion batteries
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