CN117059895A - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery - Google Patents

Nonaqueous electrolyte and nonaqueous electrolyte secondary battery Download PDF

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Publication number
CN117059895A
CN117059895A CN202311073285.7A CN202311073285A CN117059895A CN 117059895 A CN117059895 A CN 117059895A CN 202311073285 A CN202311073285 A CN 202311073285A CN 117059895 A CN117059895 A CN 117059895A
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lithium
nonaqueous electrolyte
additive
group
nonaqueous
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Inventor
王霹霹
毛冲
王晓强
黄秋洁
欧霜辉
井光辉
戴晓兵
冯攀
韩晖
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Huainan Saiwei Electronic Materials Co ltd
Hefei Saiwei Electronic Materials Co ltd
Zhuhai Smoothway Electronic Materials Co Ltd
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Huainan Saiwei Electronic Materials Co ltd
Hefei Saiwei Electronic Materials Co ltd
Zhuhai Smoothway Electronic Materials Co Ltd
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Publication of CN117059895A publication Critical patent/CN117059895A/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
    • 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
    • H01M10/052—Li-accumulators
    • 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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The application discloses a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery, wherein the nonaqueous electrolyte comprises lithium salt, a nonaqueous organic solvent and an additive, and the additive is a compound shown in a structural formula 1:wherein R is 1 ～R 2 Each independently selected from hydrogen, halogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 unsaturated bond, M is one of Li, na, K, rb, cs. The stable interfacial film is formed at the interface by means of the nitrogen-containing heterocycle ring-opening polymerization of the additive, and has a good lithium ion conduction channel, so that the circulation and high-temperature performance of the ternary high-voltage battery can be improved; and the fluorine borane forms a strong B-O bond with oxygen on the surface of the positive electrode to passivate the positive electrodeThe electrolyte is prevented from oxidative decomposition, which is beneficial to improving the high-voltage cycle performance of the ternary high-voltage battery; meanwhile, the structure can form a low-impedance SEI film on the negative electrode, so that the charge transfer impedance of the negative electrode is reduced, and the low-temperature performance of the ternary high-voltage lithium ion battery is further improved.

Description

Nonaqueous electrolyte and nonaqueous electrolyte secondary battery
Technical Field
The application belongs to the technical field of lithium ion batteries, and particularly relates to a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery.
Background
The electrochemical window of the traditional carbonate electrolyte is narrower and is generally lower than 4.3V, and after the voltage is increased, solvent decomposition is caused on one hand, more importantly, the solvent can generate side reaction with the positive electrode in a high-voltage state, so that transition metal in the ternary material is dissolved out, a large amount of gas is generated, the capacity of the battery is greatly reduced, and even the safety of the battery is influenced. For the ternary positive electrode, the oxidation states of Ni, co, mn are +2, +3, and +4, respectively. During charging, since lithium ions are deintercalated from the positive electrode, ni is converted from +2 to +3 or even +4, meanwhile, the positive electrode can react with electrolyte to generate a layer of solid electrolyte interface (CEI layer), and the CEI layer can play a role in protecting the positive electrode (similar to SEI film of the negative electrode), so that further reaction of the positive electrode and the electrolyte is prevented, and the stability of the positive electrode under the lithium removal condition is improved. However, the formation of the CEI film causes problems such as an increase in battery impedance, a decrease in rate, a decrease in capacity, and generation of gas. Therefore, it is particularly important to form an optimal positive CEI film by optimizing the electrolyte composition.
The positive film forming additive is an important component in the electrolyte, and the addition amount of the positive film forming additive is only about 1% by mass, but the performance of a certain aspect of the battery can be obviously improved, so that the positive film forming additive is the most economical and easy-to-realize industrialized mode. In the aspect of forming a film of a high-voltage electrolyte positive electrode, boron-containing lithium salt type additives LiBOB, liDFOB and the like are often used in a commercial high-voltage electrolyte formula, and the film forming mechanism of the additive and the positive electrode is as follows: the additive oxidizes and forms stable acyl radicals that recombine at the oxide-electrolyte interface and form difluoroborane dimers that form strong B-O bonds with oxygen at the surface of the positive electrode, thereby passivating the positive electrode and preventing oxidation of the electrolyte. However, the boron-containing salt contains oxalic acid groups, so that gas is easily generated in the formation and circulation processes, and the high-temperature storage performance is invalid.
Therefore, development of an electrolyte capable of withstanding ternary high voltages is needed to realize excellent performance of lithium ion batteries, so as to solve the problems of the prior art.
Disclosure of Invention
The application aims to provide a non-aqueous electrolyte, which adopts a special additive in the electrolyte to passivate a positive electrode and prevent the electrolyte from oxidative decomposition, thereby being beneficial to improving the high-voltage cycle performance of a ternary high-voltage battery.
Another object of the present application is to provide a nonaqueous electrolyte secondary battery, which uses the above electrolyte, and has good cycle performance, low temperature performance and high temperature performance at a high voltage of 4.4V.
In order to achieve the above object, the present application provides a nonaqueous electrolyte comprising a lithium salt, a nonaqueous organic solvent and an additive, wherein the additive is a compound represented by structural formula 1:
wherein R is 1 ～R 2 Each independently selected from hydrogen, halogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 unsaturated bond, M is at least one of Li, na, K, rb, cs, mg, ca, ba, al, fe, cu and Ni.
Compared with the prior art, in the non-aqueous electrolyte, the additive adopts the compound shown in the structural formula 1, and a stable interfacial film can be formed at an interface by means of ring-opening polymerization of the nitrogen-containing heterocycle of the additive, and the film has a good conductive lithium ion channel, so that the circulation and high-temperature performance of the ternary high-voltage battery can be improved; the structure contains a fluorine boron salt structure, and in the structure, fluorine borane and oxygen on the surface of the positive electrode form a strong B-O bond, so that the positive electrode is passivated, electrolyte is prevented from oxidative decomposition, and the high-voltage cycle performance of the ternary high-voltage battery is improved; meanwhile, the structure can form a low-impedance SEI film on the negative electrode, and the charge transfer impedance of the negative electrode is reduced, so that the low-temperature performance of the ternary high-voltage lithium ion battery is further improved.
Wherein, C1-C6 alkyl represents alkyl or silane group with 1-6 carbon atoms, alkyl can be chain alkyl, can also be cycloalkyl, hydrogen located on the ring of cycloalkyl can be substituted by alkyl, and as an example, alkyl can be but not limited to methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, cyclohexyl and the like.
Wherein the unsaturated bond of C1-C6 represents a hydrocarbon group having 1-6 carbon atoms, and may be a cyclic alkenyl group or an alkenyl group. Further, the hydrocarbyl group may be, but is not limited to, alkenyl, alkynyl, nitrile, and the like. By way of example, alkenyl groups include, but are not limited to, ethenyl, propenyl, 1-propenyl, isopropenyl, 2-butenyl, 1, 3-butadienyl, and the like. Illustratively, alkynyl groups include, but are not limited to, ethynyl, 2-propynyl, 1 dimethyl-2-propynyl, and the like.
Where M is one or more of Li, na, K, rb, cs, mg, ca, ba, al, fe, cu and Ni, by way of example, M includes, but is not limited to Li, na, K, rb, cs, and the like.
In some embodiments, the additive is selected from at least one of compounds 1 to 6:
in some embodiments, the mass of the additive is 0.1-3% of the total mass of the electrolyte, and further, the mass of the additive is 0.5-3% of the total mass of the electrolyte. By way of example, the mass of the additive may be 0.1%, 0.3%, 0.5%, 0.8%, 1.2%, 1.5%, 2%, 2.5%, 3% of the total mass of the electrolyte, but is not limited to the recited values, and other non-recited values within this range are equally applicable.
In some embodiments, the organic solvent is selected from at least one of carbonates, carboxylates, ethers, and heterocyclic compounds. For example, the nonaqueous organic solvent is selected from at least one of cyclic carbonates, chain carbonates, cyclic esters, chain esters, cyclic ethers, chain ethers, sulfone compounds, sulfoxide compounds, and ionic liquids. Further, the carbonates may be, but are not limited to, chain carbonates, cyclic carbonates. As examples, cyclic carbonates such as: ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), pentylene carbonate, vinylene Carbonate (VC) or derivatives thereof. In some embodiments, the organic solvent is at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl Methyl Carbonate (EMC), and Propylene Carbonate (PC). In some embodiments, the organic solvent is a carboxylate solvent, which includes a cyclic carboxylate and/or a chain carbonate, which may include, but is not limited to: at least one of gamma-butyrolactone, gamma-valerolactone and delta-valerolactone; as the chain carbonate, specific ones may include, but are not limited to: at least one of Methyl Acetate (MA), ethyl Acetate (EA), propyl acetate (EP), butyl acetate, propyl Propionate (PP) and butyl propionate. In some embodiments, the organic solvent is an ether solvent, including cyclic or chain ethers, which may include, but are not limited to, at least one of 1, 3-Dioxolane (DOL), 1, 4-Dioxane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH 3-THF), 2-trifluoromethyl tetrahydrofuran (2-CF 3-THF); the chain ether may specifically include, but is not limited to, at least one of dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether.
In some embodiments, the lithium salt is selected from lithium hexafluorophosphate (LiPF 6 ) Lithium perchlorate (LiClO) 4 ) Lithium tetrafluoroborate (LiBF) 4 ) Lithium methylsulfonate (LiCH) 3 SO 3 ) Lithium triflate (LiCF) 3 SO 3 ) Lithium bis (trifluoromethylsulfonyl) imide (LiN (CF) 3 SO 2 ) 2 ) Lithium dioxaborate (LiBOB), lithium difluorooxalato borate (LiDFOB), lithium difluorophosphate (LiPO) 2 F 2 ) Lithium difluorobis (oxalato) phosphate (LiDFBP), lithium difluorosulfonimide (LiLSI), lithium bistrifluoromethylsulfonimide (LiTFSI), lithium fluorosulfonate (LiSO) 2 F) Lithium diphosphate (LiPO) 2 F 2 ) And at least one of lithium lower aliphatic carboxylate. As an example, the lithium salt is lithium hexafluorophosphate or lithium tetrafluoroborate.
In some embodiments, the lithium salt comprises 6-20% by mass of the total mass of the electrolyte, preferably 7-20% by mass of the total mass of the electrolyte. By way of example, the mass of lithium salt is 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% of the total mass of the electrolyte, but is not limited to the recited values, and other non-recited values within this range are equally applicable.
In some embodiments, the electrolyte of the present application further comprises an auxiliary selected from at least one of Vinylene Carbonate (VC), vinylene carbonate (VEC), fluoroethylene carbonate (FEC), ethylene Sulfite (ES), 1,3 Propane Sultone (PS), 1, 3-propenesulfonic acid lactone (PES), 1, 4-Butane Sultone (BS), vinyl sulfate (DTD), succinic Anhydride (SA), maleic anhydride, 2-methyl maleic anhydride, 2-propynyl methyl carbonate, tetraethylene silane, triallyl isocyanurate, hexamethylene diisonitrile, phenanthroline, terephthalyl diisocyanate, 2, 4-toluene diisocyanate, N-phenyl bis (trifluoromethanesulfonyl) imide, vinyl disulfate, phenyl methanesulfonate, vinyl disulfate, propylene bisspiro sulfate, hydroquinone difluorosulfonate, triallyl phosphate, tripropynyl phosphate, 2, 4-butane sultone, isocyanatoethyl methacrylate, methylene methanesulfonate, tris (trimethylsilane) borate, tris (trimethylsilane) phosphate, and trisilane phosphate. Illustratively, the adjuvant is 1, 4-butanesulfonic acid lactone or fluoroethylene carbonate.
In some embodiments, the mass of the auxiliary agent is 0.5-10.0% of the total mass of the electrolyte, further, the mass of the auxiliary agent is 2-8% of the total mass of the electrolyte, and preferably, the mass of the auxiliary agent is 3-8% of the total mass of the electrolyte. Illustratively, the auxiliary agent comprises 0.5%, 1.5%, 2%, 2.5%, 3%, 4%, 4.5%, 5%, 5.5%, 6.0%, 8% of the total electrolyte mass, but is not limited to the recited values, and other non-recited values within the range are equally applicable.
Accordingly, the application also provides a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a separator and the non-aqueous electrolyte mentioned above. The nonaqueous electrolyte secondary battery comprises, but is not limited to, a lithium ion battery, and the nonaqueous electrolyte is used in the nonaqueous electrolyte secondary battery, so that good cycle performance, low-temperature performance and high-temperature performance can be realized when the highest charging voltage is 4.4V.
In some embodiments, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) 2 ) Lithium nickel oxide (e.g. LiNiO) 2 ) Lithium manganese oxide(e.g. LiMnO 2 、LiMn 2 O 4 ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (structure such as LiNi x Co y Mn (1-x-y) M z O 2 Wherein 0.6.ltoreq.x<0.9，x+y<1，0≤z<0.08, M is at least one of Al, mg, zr and Ti). Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO 4 (also referred to as LFP for short)), a composite of lithium iron phosphate and carbon, a composite of lithium manganese phosphate (e.g., liMnPO 4), a composite of lithium manganese phosphate and carbon, a composite of lithium manganese phosphate, lithium manganese phosphate and carbon.
In some embodiments, the negative electrode active material includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode. Wherein the carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, and the like; the silicon-based anode may include a silicon material, an oxide of silicon, a silicon-carbon composite material, a silicon alloy material, or the like; the tin-based negative electrode may include tin, tin carbon, tin oxygen, and tin metal compounds; the lithium negative electrode may include metallic lithium or a lithium alloy. The lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.
In some embodiments, the separator is disposed between the positive electrode and the negative electrode, and the separator may be a conventional separator, such as a ceramic separator, a polymer separator, a non-woven fabric, an inorganic-organic composite separator, or the like. Wherein the polymer membrane is selected from at least one of polyolefin, polyamide, polysulfone, polyphosphazene, polyethersulfone, polyetheretherketone, polyetheramide and polyacrylonitrile, including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP/PE, double-layer PP/PP, and three-layer PP/PE/PP.
Detailed Description
For a better description of the objects, technical solutions and advantageous effects of the present application, the present application will be further described with reference to specific examples. It should be noted that the following implementation of the method is a further explanation of the present application and should not be taken as limiting the present application.
Example 1
(1) Preparation of electrolyte:
mixing Ethylene Carbonate (EC), diethyl carbonate (DEC) and ethylmethyl carbonate (EMC) according to the mass ratio of EC: DEC: EMC=2:1:1 to obtain 83.5g of organic solvent, mixing, and adding 13g of lithium hexafluorophosphate (LiPF 6 ) After complete dissolution of the lithium salt, 3g of 1, 4-butanesulfonic acid lactone (BS) and 0.5g of additive compound 1 were added.
(2) Preparation of a positive plate:
the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.09 Al 0.01 O 2 Preparing positive electrode slurry from conductive agent Super P, binder polyvinylidene fluoride (PVDF) and N-methyl pyrrolidone (NMP), wherein the solid content of the positive electrode slurry is 50wt%, and the solid content is LiNi 0.8 Co 0.1 Mn 0.09 Al 0.01 O 2 Coating positive electrode slurry on the upper and lower surfaces of a current collector aluminum foil, drying at 85 ℃, cold pressing, trimming, cutting pieces, splitting, and drying for 4 hours under a vacuum condition at 85 ℃ to prepare a positive electrode plate, wherein the mass ratio of Super P to PVDF is 8:1:1.
(3) Preparing a negative plate:
uniformly mixing graphite, a conductive agent Super P, a thickener carboxymethyl cellulose (CMC) and an adhesive styrene-butadiene rubber (SBR) in deionized water to prepare negative electrode slurry, wherein the solid content of the negative electrode slurry is 30wt%, the mass ratio of the graphite, the Super P, the CMC and the adhesive styrene-butadiene rubber (SBR) in solid components is 88:7:3:2, coating the negative electrode slurry on the upper and lower surfaces of a current collector copper foil, drying at 85 ℃, cold pressing, trimming, cutting and slitting, and drying for 12 hours under vacuum condition at 120 ℃ to prepare the negative electrode plate.
(4) A16 μm polyethylene film was used as a separator.
(5) Preparation of a lithium ion battery:
and stacking the positive electrode plate, the isolating film and the negative electrode plate in sequence, enabling the isolating film to be positioned between the positive electrode plate and the negative electrode plate to play a role in isolating the positive electrode from the negative electrode plate, winding to obtain a bare cell, welding the electrode lug, placing the bare cell in an outer package, injecting the prepared electrolyte into the dried cell, packaging, standing, forming, shaping, testing the capacity and the like, and thus completing the preparation of the lithium ion battery with the capacity of 1000 mAh.
The electrolyte compositions of examples 2 to 8 and comparative example 1 are shown in table 1, and the procedure for preparing the nonaqueous electrolyte and the lithium ion battery is the same as in example 1.
Table 1 electrolyte compositions of examples and comparative examples
Lithium salt/mass (g) Organic solvent (mass g) Additive/(g) Auxiliary/(g)
Example 1 LiPF 6 (13g) EC/DEC/EMC＝2:1:1(83.5g) Compound 1 (0.5 g) BS(3.0g)
Example 2 LiPF 6 (13g) EC/DEC/EMC＝2:1:1(83.5g) Compound 2 (0.5 g) BS(3.0g)
Example 3 LiPF 6 (13g) EC/DEC/EMC＝2:1:1(83.5g) Compound 3 (0.5 g) BS 3.0g)
Example 4 LiPF 6 (13g) EC/DEC/EMC＝2:1:1(83.5g) Compound 4 (0.5 g) BS(3.0g)
Example 5 LiPF 6 (13g) EC/DEC/EMC＝2:1:1(83.5g) Compound 5 (0.5 g) BS(3.0g)
Example 6 LiPF 6 (13g) EC/DEC/EMC＝2:1:1(83.5g) Compound 6 (0.5 g) BS(3.0g)
Example 7 LiPF 6 (14g) EC/DEC/EMC＝1:1:1(80g) Compound 4 (1 g) BS(5g)
Example 8 LiPF 6 (12.5g) EC/DEC/EMC＝1:1:1(79.5g) Compound 4 (2 g) BS(6g)
Comparative example 1 LiPF 6 (13g) EC/DEC/EMC＝2:1:1(82.5g) - BS(4.5g)
The lithium ion batteries prepared in examples 1 to 8 and comparative example 1 were subjected to a normal temperature cycle test, a high temperature storage test, and a low temperature discharge test, respectively, according to the following test conditions, and the test results are shown in table 2.
Normal temperature cycle test：
The lithium ion battery is charged and discharged at the normal temperature (25 ℃) at 1.0C/1.0C (the discharge capacity of the battery is C) 0 ) The upper limit voltage was 4.4V, and then charging and discharging at 1.0C/1.0C was performed for 500 weeks under normal temperature conditions (the discharge capacity of the battery was C) 1 )；
Capacity retention= (C 1 /C 0 )*100％
High temperature cycle test：
The lithium ion battery is charged and discharged at 1.0C/1.0C once under the condition of high temperature (45 ℃) (the discharge capacity of the battery is C) 0 ) The upper limit voltage was 4.4V, and then charging and discharging at 1.0C/1.0C was performed for 300 weeks under normal temperature conditions (the battery discharge capacity was C) 1 )；
Capacity retention= (C 1 /C 0 )*100％
High temperature storage test：
The lithium ion battery is charged and discharged at 0.3C/0.3C once under the condition of normal temperature (25 ℃) (record of the discharge capacity of the battery)Is C 0 ) The upper limit voltage is 4.4V; placing the battery in a 60 ℃ oven for 15d, taking out the battery, placing the battery in a 25 ℃ environment, discharging at 0.3C, and recording the discharge capacity as C 1 The method comprises the steps of carrying out a first treatment on the surface of the The lithium ion battery was then charged and discharged once at 0.3C/0.3C (the discharge capacity of the battery was recorded as C) 2 )；
Capacity retention= (C 1 /C 0 )*100％
Capacity recovery rate= (C 2 /C 0 )*100％
Low temperature discharge test：
Lithium ion batteries were charged and discharged at 0.3C/0.3C once (the discharge capacity of the battery was recorded as C) at normal temperature (25 ℃ C.) 0 ) The upper limit voltage is 4.4V; placing the battery in an oven at-20 ℃ for 4 hours, discharging the battery at 0.3C, and recording the discharge capacity as C 1 The cut-off voltage was 3.0V,
capacity retention= (C 1 /C 0 )*100％
Table 2 results of performance tests of lithium ion batteries of examples and comparative examples
As is clear from Table 2, the electrolyte of comparative example 1 was not used with the additive of the present application, and the high-temperature storage performance, the high-temperature cycle performance and the low-temperature discharge performance were all unsatisfactory, whereas the lithium ion batteries prepared from the electrolytes of examples 1 to 8 had good high-temperature storage performance, cycle performance and low-temperature discharge performance. The electrolyte additive adopts the compound shown in the structural formula 1, and can form a stable interfacial film at the interface by means of nitrogen-containing heterocycle ring-opening polymerization, and the film has a good conductive lithium ion channel, thereby being beneficial to improving the cycle and high-temperature performance of the ternary high-voltage battery; the structure contains a fluorine boron salt structure, and in the structure, fluorine borane and oxygen on the surface of the positive electrode form a strong B-O bond, so that the positive electrode is passivated, electrolyte is prevented from oxidative decomposition, and the high-voltage cycle performance of the ternary high-voltage battery is improved; meanwhile, the structure can form a low-impedance SEI film on the negative electrode, and the charge transfer impedance of the negative electrode is reduced, so that the low-temperature performance of the ternary high-voltage lithium ion battery is further improved.
From comparison of examples 1 to 4, it was found that, in the compounds 1 and 2, the positive and negative electrodes were reinforced by double bonds to form films and the films were thicker than those of the compounds 3 and 4, and therefore, the high-temperature circularity and high-temperature storage were significantly improved, but the low-temperature discharge performance was significantly deteriorated. From the slave
As can be seen from comparison of examples 4 to 6, the combination property of the compound 5 is obviously better than that of the compound 4 and the compound 6, because CS cesium ions can form an electrostatic protection layer on the surface of the negative electrode active material relative to sodium ions and lithium ions, reduce or inhibit dendrite formation, improve the normal-temperature and high-temperature cycle performance and low-temperature discharge performance of the battery cell, and are obviously better than those of lithium ions and sodium ions.
As can be seen from comparison of examples 7 and 8 with example 1, the optimum amount of the compound 4 is about 1%, and when the content is low, the film formation is relatively slightly thin, which is unfavorable for the expression of the comprehensive properties, and when the content is high, the comprehensive properties are slightly reduced due to the excessively thick film formation resistance.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present application and not for limiting the scope of the present application, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solution of the present application without departing from the spirit and scope of the technical solution of the present application.

Claims (10)

1. The nonaqueous electrolyte comprises lithium salt, nonaqueous organic solvent and additive, and is characterized in that the additive is a compound shown in a structural formula 1:
wherein R is 1 ～R 2 Each independently selected from hydrogenHalogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 unsaturated bond, M is at least one of Li, na, K, rb, cs, mg, ca, ba, al, fe, cu and Ni.
2. The nonaqueous electrolyte according to claim 1, wherein the alkyl group is at least one selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl and cyclohexyl.
3. The nonaqueous electrolyte according to claim 1, wherein the unsaturated bond is a hydrocarbon group, and the hydrocarbon group is at least one selected from the group consisting of an alkenyl group, an alkynyl group and a nitrile group.
4. The nonaqueous electrolyte according to claim 1, wherein the additive is at least one selected from the group consisting of compounds 1 to 6:
5. the nonaqueous electrolytic solution according to claim 1, wherein the mass of the additive is 0.1% to 3% of the total mass of the electrolytic solution.
6. The nonaqueous electrolytic solution according to claim 1, wherein the nonaqueous organic solvent is at least one selected from the group consisting of a cyclic carbonate, a chain carbonate, a cyclic ester, a chain ester, a cyclic ether, a chain ether, a sulfone compound, a sulfoxide compound and an ionic liquid.
7. The nonaqueous electrolyte of claim 1, further comprising an auxiliary selected from at least one of vinylene carbonate, fluoroethylene carbonate, ethylene sulfite, 1,3 propane sultone, 1, 3-propenolactone, 1, 4-butane sultone, ethylene sulfate, succinic anhydride, maleic anhydride, 2-methyl maleic anhydride, 2-propynyl methyl carbonate, tetravinyl silane, triallyl isocyanurate, hexamethylene diisonitrile, phenanthroline, terephthal-ylene diisocyanate, 2, 4-toluene diisocyanate, N-phenyl bis (trifluoromethane sulfonyl) imide, vinyl disulfate, phenyl methanesulfonate, vinyl disulfate, dispiro-propylene sulfate, hydroquinone difluorosulfonate, triallyl phosphate, tripropyl phosphate, 2, 4-butane sultone, isocyanatoethyl methacrylate, methane disulfonic acid methylene ester, tri (trimethylsilane) borate, tri (trimethylsilane) phosphate, tri (vinyl disilane) phosphate.
8. The nonaqueous electrolyte of claim 1, wherein the lithium salt is at least one selected from the group consisting of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium methylsulfonate, lithium trifluoromethylsulfonate, lithium bistrifluoromethylsulfonimide, lithium dioxaborate, lithium difluorooxalato borate, lithium difluorophosphate, lithium difluorobisoxalato phosphate, lithium difluorosulfimide and lithium bistrifluoromethylsulfonimide, lithium fluorosulfonate, lithium diphosphate and lithium lower aliphatic carboxylate.
9. A nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode and a separator, characterized by further comprising the nonaqueous electrolyte according to any one of claims 1 to 8.
10. The nonaqueous electrolyte secondary battery according to claim 9, wherein the positive electrode active material includes at least one of a lithium-containing phosphate of an olivine structure, a lithium transition metal oxide, and respective modified compounds thereof.
CN202311073285.7A 2023-08-24 2023-08-24 Nonaqueous electrolyte and nonaqueous electrolyte secondary battery Pending CN117059895A (en)

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