CN115020806A - Electrolyte and lithium ion battery containing same - Google Patents
Electrolyte and lithium ion battery containing same Download PDFInfo
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- CN115020806A CN115020806A CN202210784678.8A CN202210784678A CN115020806A CN 115020806 A CN115020806 A CN 115020806A CN 202210784678 A CN202210784678 A CN 202210784678A CN 115020806 A CN115020806 A CN 115020806A
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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
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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
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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
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- 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
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Abstract
The invention provides an electrolyte and a lithium ion battery containing the same. The electrolyte comprises an organic solvent, lithium salt and an additive, wherein the additive comprises a bis (trimethylsilyl) borane sulfonic anhydride compound shown as a formula 1. The compound additive bis (trimethylsilyl) boryl sulfonic anhydride compound in the electrolyte has the capability of passivating the positive electrode interface and forming a stable SEI protective film, so that the performances of high-temperature circulation, storage and the like of the lithium ion secondary battery are improved, and the internal resistance is considered at the same time.
Description
Technical Field
The invention relates to the field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery containing the same.
Background
In recent years, with the development of new energy technology, lithium ion power batteries for vehicles have been more demanding on the performance of lithium ion secondary batteries. In order to satisfy the long driving range and wide temperature range environment of the electric automobile, the development of a lithium ion secondary battery with higher energy density, more excellent high-temperature cycle and storage performance is required. However, high energy density lithium ion secondary batteries generally use transition metal oxides (e.g., lithium nickel cobalt manganese oxide) having a high nickel content, which are susceptible to interface degradation at high temperature and high pressure, particle breakage, oxidation of electrolyte, and rapid life decay at high temperature, and thus it is necessary to develop electrolyte additives capable of stabilizing the interface of the positive electrode at high temperature.
CN 111276741a discloses an electrolyte for a secondary battery comprising a lithium salt, a nonaqueous organic solvent and a difluorophosphite olefin compound, and a lithium secondary battery comprising the same. The electrolyte can further stabilize the cathode structure, can only improve the high-temperature stability to a certain extent, and does not play a role in stabilizing the anode interface.
CN 110838595A discloses a lithium ion battery electrolyte and application thereof, wherein a fluorine-containing nonionic surfactant is added, so that the lithium ion battery has high wettability, good high-temperature output characteristic, rate capability and cycle performance, but the improvement on the high-temperature storage performance of the battery is not obvious.
Therefore, how to prepare an electrolyte having high temperature cycle and storage properties is an important research direction in the art.
Disclosure of Invention
The invention aims to provide an electrolyte solution for solving the problem of service life degradation of a lithium ion battery in high-temperature cycle or storage in the prior art and a lithium ion battery containing the electrolyte solution.
In order to achieve the purpose, the invention adopts the following technical scheme:
one of the purposes of the invention is to provide an electrolyte, which is characterized by comprising an organic solvent, lithium salt and an additive, wherein the additive comprises a bis (trimethylsilyl) borane sulfonic anhydride compound shown as a formula 1,
In a preferred embodiment of the present invention, the bis (trimethylsilyl) borylsulfonic anhydride compound accounts for 0.01 to 3% by mass of the electrolyte solution based on 100% by mass of the electrolyte solution, and the mass fraction may be 0.01%, 0.05%, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3% or the like, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, and preferably 0.1 to 1%.
As a preferable technical scheme of the invention, the additive comprises any one or the combination of at least two of the compounds as shown in the formula 2-6,
as a preferable technical proposal of the invention, the additive also comprises a high-temperature additive,
preferably, the high temperature additive comprises any one of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, vinyl sulfate, 1, 3-propane sultone, tris (trimethylsilane) borate or tris (trimethylsilane) phosphate, or a combination of at least two thereof, wherein typical but non-limiting examples of such combinations are: a combination of vinylene carbonate and vinyl ethylene carbonate, a combination of vinyl ethylene carbonate and fluoroethylene carbonate, a combination of fluoroethylene carbonate and vinyl sulfate, a combination of vinyl sulfate and 1, 3-propanesultone, a combination of 1, 3-propanesultone and tris (trimethylsilane) borate or a combination of tris (trimethylsilane) borate and tris (trimethylsilane) phosphate.
Preferably, the high temperature additive comprises vinyl sulfate.
Preferably, the high-temperature additive accounts for 0.01 to 3% of the electrolyte solution by 100% of the electrolyte solution by mass, wherein the high-temperature additive may be 0.01%, 0.05%, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3% or the like by mass, but is not limited to the enumerated values, and other non-enumerated values within the numerical range are also applicable, preferably 0.1 to 2%.
Preferably, the lithium salt additive comprises lithium difluorophosphate and lithium bis-fluorosulfonylimide.
Preferably, the lithium difluorophosphate accounts for 0.1 to 1.5% by mass of the electrolyte solution based on 100% by mass of the electrolyte solution, wherein the mass fraction may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%, but is not limited to the enumerated values, and other values not enumerated within the numerical range are also applicable.
Preferably, the mass fraction of the lithium bis (fluorosulfonate) imide in the electrolyte solution is 0.1 to 10% based on 100% of the electrolyte solution, wherein the mass fraction may be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, but is not limited to the recited values, and other values not recited in the above range are also applicable.
In a preferred embodiment of the present invention, the organic solvent includes a cyclic carbonate and a chain acid ester.
Preferably, the cyclic carbonate includes any one of ethylene carbonate, propylene carbonate, butylene carbonate or γ -butyrolactone, or a combination of at least two thereof, wherein typical but non-limiting examples are: a combination of ethylene carbonate and propylene carbonate, a combination of propylene carbonate and butylene carbonate, a combination of butylene carbonate and γ -butyrolactone, a combination of propylene carbonate and γ -butyrolactone, or the like.
Preferably, the chain acid ester comprises any one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate or ethyl butyrate, or a combination of at least two thereof, wherein the combination is typically but not limited to: a combination of dimethyl carbonate and diethyl carbonate, a combination of ethyl methyl carbonate and propyl methyl carbonate, a combination of ethyl propyl carbonate and methyl formate, a combination of methyl formate and ethyl formate, a combination of propyl formate and methyl acetate, a combination of ethyl acetate and propyl acetate, a combination of methyl propionate and ethyl propionate, a combination of propyl propionate and methyl butyrate, or a combination of methyl butyrate and ethyl butyrate, and the like.
The organic solvent can better prevent the damage of water to the electrolyte, and is beneficial to promoting the more sufficient dissolution of all components in the electrolyte, thereby improving the cooperativity of all components and obtaining the electrolyte with excellent electrical properties.
In a preferred embodiment of the present invention, the volume ratio of the cyclic carbonate to the chain acid ester is (10 to 40): (60 to 90), wherein the mass ratio may be 10:90, 15:85, 20:80, 25:75, 30:70, 35:75, or 40:60, but is not limited to the recited values, and other values not recited within the range of the recited values are also applicable, and (15 to 40): (60-85).
Preferably, the organic solvent accounts for 65.5 to 89.6% of the electrolyte solution by 100% of the electrolyte solution by mass, wherein the organic solvent may be 65.5%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 89.6% or the like by mass, but is not limited to the recited values, and other values not recited in the above range are also applicable.
As a preferred embodiment of the present invention, the lithium salt includes any one or a combination of at least two of lithium hexafluorophosphate, lithium tetrafluorophosphate, lithium bis (oxalate) borate, lithium difluoro (oxalate) phosphate, lithium bis (trifluoromethylsulfonyl) imide or lithium perchlorate, wherein the combination is typically but not limited to: a combination of lithium hexafluorophosphate and lithium tetrafluorophosphate, a combination of lithium tetrafluorophosphate and lithium bis (oxalato) borate, a combination of lithium difluoro (oxalato) borate and lithium difluoro (oxalato) phosphate, a combination of lithium difluoro (oxalato) phosphate and lithium bis (trifluoromethylsulfonyl) imide, a combination of lithium bis (trifluoromethylsulfonyl) imide and lithium perchlorate, and the like.
Preferably, the lithium salt comprises lithium hexafluorophosphate.
The lithium hexafluorophosphate is used as the electrolyte of the electrolyte, and the conductivity, the energy storage property and the environmental protection property of the lithium ion battery can be enhanced.
In a preferred embodiment of the present invention, the lithium hexafluorophosphate is present in an amount of 10 to 20% by mass based on 100% by mass of the electrolyte solution, wherein the amount of the lithium hexafluorophosphate may be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20% by mass, but the present invention is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.
Preferably, the lithium salt accounts for 10 to 20% of the electrolyte solution by mass fraction of 100%, wherein the mass fraction may be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or the like, but is not limited to the recited values, and other values not recited in the range of the values are also applicable. The second purpose of the present invention is to provide a lithium ion battery comprising the electrolyte solution according to the first purpose.
The lithium ion battery also comprises a positive pole piece and a negative pole piece.
In a preferred embodiment of the present invention, the material of the positive electrode sheet includes a lithium transition metal oxide and/or a lithium transition metal phosphate compound.
Preferably, the transition metal oxide of lithium comprises LiCoO 2 、LiNi x Co y Mn z O 2 、LiNi x Mn y O 2 、LiMn 2 O 4 、LiMnO 2 、Li 2 MnO 4 、Li 1+a Mn 1-x M x O 2 、LiCo 1-x M x O 2 、LiMn 1-x M x O 4 Or Li 2 Mn 1-x O 4 Any one or a combination of at least two of the following, typical but non-limiting examples of which are: LiCoO 2 And LiNi x Co y Mn z O 2 Combination of (2) and LiNi x Mn y O 2 And LiMn 2 O 4 Combination of (1) and LiMnO 2 And Li 2 MnO 4 Combination of (1), Li 1+a Mn 1-x M x O 2 And LiCo 1-x M x O 2 Combination of (5) or LiMn 1-x M x O 4 And Li 2 Mn 1-x O 4 Combinations of (a), (b), and the like. Wherein, a is more than or equal to 0<0.2, 0. ltoreq. x.ltoreq.1, 0. ltoreq. y.ltoreq.1, 0. ltoreq. z.ltoreq.1, where a can have the value 0, 0.05, 0.1, 0.15 or 0.2, x can have the value 0, 0.1, 0.2, 0.03, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, y can have the value 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, z can have the value 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc., but not limited to the values listed, but also other values within the respective numerical ranges stated above apply equally.
Preferably, the lithium transition metal phosphate compound comprises LiFePO 4 、LiMnPO 4 、LiCoPO 4 Or LiFe 1- x M x PO 4 Any one or a combination of at least two of them, wherein the combinationTypical but non-limiting examples are: LiFePO 4 And LiMnPO 4 Combination of (2), LiMnPO 4 And LiCoPO 4 Combinations of (5) or LiCoPO 4 And LiFe 1-x M x PO 4 Wherein M is selected from any one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, and Ti, 0. ltoreq. x.ltoreq.1, wherein x may be 0, 0.1, 0.2, 0.03, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, but is not limited to the values listed, and other values not listed within this range of values are also applicable.
Preferably, the material of the negative electrode plate comprises any one or a combination of at least two of a carbonaceous material, an alloy material or a lithium-containing metal composite material, wherein the combination is typically but not limited to: a combination of a carbonaceous material and an alloy-based material, a combination of an alloy-based material and a lithium-containing metal composite material, a combination of a carbonaceous material and a lithium-containing metal composite material, or the like.
Preferably, the material of the negative electrode plate comprises any one of natural graphite, artificial graphite, soft carbon, hard carbon, lithium titanate, silicon-carbon alloy or silicon-oxygen alloy or a combination of at least two of the following, wherein the combination is a typical but non-limiting example: a combination of natural graphite and artificial graphite, a combination of artificial graphite and soft carbon, a combination of soft carbon and hard carbon, a combination of hard carbon and lithium titanate, a combination of lithium titanate and silicon, a combination of silicon and silicon-carbon alloy, a combination of silicon-carbon alloy and silicon-oxygen alloy, and the like.
Compared with the prior art, the invention has the following beneficial effects:
the electrolyte prepared by the invention has excellent high-temperature storage performance and cycle performance when applied to a lithium ion battery, the capacity retention rate can reach more than 95 percent at 60 ℃ for 30 days, the gas generation expansion rate can be as low as less than 12 percent, and the cycle capacity retention rate of 800 circles at 45 ℃ can reach more than 95 percent.
Drawings
FIG. 1 is a graph comparing the cycle performance at 45 ℃ of example 1 of the present invention and comparative example 1.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitation of the present invention.
Example 1
The embodiment provides a lithium ion battery electrolyte:
the lithium ion battery electrolyte comprises lithium salt, an organic solvent and an additive;
lithium salt: lithium hexafluorophosphate accounting for 13% of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100%;
organic solvent: the electrolyte is an organic solvent accounting for 81% of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100%, wherein the organic solvent comprises ethylene carbonate, methyl ethyl carbonate and diethyl carbonate in a mass ratio of 30:50: 20;
additive: based on the mass fraction of the electrolyte as 100 percent, the bis (trimethylsilyl) boron methylsulfonic anhydride compound which accounts for 0.5 percent of the mass fraction of the electrolyte, the vinyl sulfate which accounts for 0.5 percent of the mass fraction of the electrolyte, the lithium difluorophosphate which accounts for 1 percent of the mass fraction of the electrolyte and the lithium difluorosulfonimide which accounts for 4 percent of the mass fraction of the electrolyte are shown in a formula 2,
the synthesis method of the bis (trimethylsilyl) boron methylsulfonic anhydride compound shown in the formula 2 comprises the following steps:
example 2
The embodiment provides a lithium ion battery electrolyte:
the lithium ion battery electrolyte comprises lithium salt, an organic solvent and an additive;
lithium salt: lithium hexafluorophosphate accounting for 10 percent of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100 percent;
organic solvent: the electrolyte is an organic solvent accounting for 89.6% of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100%, wherein the organic solvent comprises propylene carbonate and ethyl propyl carbonate in a mass ratio of 40: 60;
additive: based on the mass fraction of the electrolyte as 100 percent, the bis (trimethylsilyl) boron methylsulfonic anhydride compound which accounts for 0.1 percent of the mass fraction of the electrolyte, the vinyl sulfate which accounts for 0.1 percent of the mass fraction of the electrolyte, the lithium difluorophosphate which accounts for 0.1 percent of the mass fraction of the electrolyte and the lithium difluorosulfonimide which accounts for 0.1 percent of the mass fraction of the electrolyte are shown in a formula 3,
the synthesis method of the bis (trimethylsilyl) boron methylsulfonic anhydride compound shown in the formula 3 comprises the following steps:
example 3
The embodiment provides a lithium ion battery electrolyte:
the lithium ion battery electrolyte comprises lithium salt, an organic solvent and an additive;
lithium salt: lithium hexafluorophosphate accounting for 20 percent of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100 percent;
organic solvent: the electrolyte is taken as 100 percent, and the organic solvent accounts for 65.5 percent of the mass fraction of the electrolyte, wherein the organic solvent comprises gamma-butyrolactone and methyl propionate in a mass ratio of 15: 85;
additive: based on the mass fraction of the electrolyte as 100 percent, the bis (trimethylsilyl) boron methylsulfonic anhydride compound which accounts for 1 percent of the mass fraction of the electrolyte, the vinyl sulfate which accounts for 2 percent of the mass fraction of the electrolyte, the lithium difluorophosphate which accounts for 1.5 percent of the mass fraction of the electrolyte and the lithium difluorosulfonimide which accounts for 10 percent of the mass fraction of the electrolyte are shown in a formula 4,
wherein, the synthesis method of the bis (trimethylsilyl) boron methylsulfonic anhydride compound shown in the formula 4 comprises the following steps:
example 4
The embodiment provides a lithium ion battery electrolyte:
the lithium ion battery electrolyte comprises lithium salt, an organic solvent and an additive;
lithium salt: lithium hexafluorophosphate accounting for 13% of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100%;
organic solvent: the electrolyte is an organic solvent accounting for 81.98% of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100%, wherein the organic solvent comprises ethylene carbonate and diethyl carbonate in a mass ratio of 10: 90;
additive: based on the mass fraction of the electrolyte as 100 percent, the bis (trimethylsilyl) boron methylsulfonic anhydride compound which accounts for 0.01 percent of the mass fraction of the electrolyte, the vinyl sulfate which accounts for 0.01 percent of the mass fraction of the electrolyte, the lithium difluorophosphate which accounts for 1 percent of the mass fraction of the electrolyte and the lithium difluorosulfonimide which accounts for 4 percent of the mass fraction of the electrolyte are shown in a formula 5,
the synthesis method of the bis (trimethylsilyl) boron methylsulfonic anhydride compound shown in the formula 5 comprises the following steps:
example 5
The embodiment provides a lithium ion battery electrolyte:
the lithium ion battery electrolyte comprises lithium salt, an organic solvent and an additive;
lithium salt: lithium hexafluorophosphate accounting for 13% of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100%;
organic solvent: the electrolyte is an organic solvent accounting for 76% of the mass fraction of the electrolyte by taking the mass fraction of the electrolyte as 100%, wherein the organic solvent comprises propylene carbonate, ethyl methyl carbonate and diethyl carbonate in a mass ratio of 30:50: 20;
additive: based on the mass fraction of the electrolyte as 100%, a bis (trimethylsilyl) boron methylsulfonic anhydride compound accounting for 3% of the mass fraction of the electrolyte, vinyl sulfate accounting for 3% of the mass fraction of the electrolyte, lithium difluorophosphate accounting for 1% of the mass fraction of the electrolyte and lithium bis (fluorosulfonyl) imide accounting for 4% of the mass fraction of the electrolyte are shown as formula 6,
the synthesis method of the bis (trimethylsilyl) boron methylsulfonic anhydride compound shown in the formula 6 comprises the following steps:
example 6
In this example, except that the bis (trimethylsilyl) boron methylsulfonic anhydride compound represented by formula 2, which accounts for 0.5% of the mass fraction of the electrolyte, was replaced by: as shown in formula 2, the conditions were the same as in example 1 except that the mass fraction of the organic solvent was changed to 76.5% in addition to the bis (trimethylsilyl) boron methylsulfonic anhydride compound occupying 5% by mass of the electrolyte.
Example 7
The present example was carried out under the same conditions as in example 1 except that vinyl sulfate, which accounts for 0.5 mass% of the electrolyte, was replaced with 1, 3-propane sultone, which accounts for 0.5 mass% of the electrolyte.
Example 8
This example was carried out under the same conditions as in example 1 except that 0.5% by mass of the electrolyte of vinyl sulfate was replaced with 0.5% by mass of the electrolyte of vinylene carbonate.
Example 9
This example was carried out under the same conditions as example 1 except that lithium difluorophosphate accounting for 1 mass% of the electrolyte and lithium bis (fluorosulfonyl) imide accounting for 4 mass% of the electrolyte were not added and the mass fraction of the organic solvent was changed to 86%.
Comparative example 1
This comparative example was conducted under the same conditions as in example 1 except that the bis (trimethylsilyl) boron methylsulfonic anhydride compound shown in formula 2 was not added.
The cycle performance at 45 ℃ in inventive example 1 and comparative example 1 is shown in fig. 1.
The electrolytes of examples 1 to 9 and comparative example 1 were assembled into a lithium ion battery, wherein the battery was prepared as follows:
(1) preparing a positive pole piece of the lithium ion battery:
preparing positive electrode active material nickel cobalt lithium manganate (LiNi) 0.6 Co 0.1 Mn 0.3 O 2 ) Dissolving a conductive agent Super-P and a bonding agent PVDF in a solvent N-methyl pyrrolidone according to a mass ratio of 96:2.0:2.0, uniformly mixing to prepare anode slurry, and uniformly coating the anode slurry on a current collector aluminum foil with a coating amount of 18mg/cm 2 And then drying at 85 ℃, performing cold pressing, trimming, cutting into pieces and slitting, drying for 4 hours at 85 ℃ under a vacuum condition, and welding tabs to prepare the positive plate of the lithium ion secondary battery meeting the requirements.
(2) Preparing a lithium ion battery negative pole piece:
preparing the negative active material of artificial graphite, a conductive agent Super-P, a thickening agent CMC and a binding agent SBR according to the massDissolving the mixture in deionized water at a weight ratio of 96.5:1.0:1.0:1.5, uniformly mixing to prepare negative electrode slurry, and uniformly coating the negative electrode slurry on a current collector copper foil with the coating weight of 8.9mg/cm 2 And then drying at 85 ℃, performing cold pressing, trimming, cutting into pieces and slitting, drying for 4 hours at 110 ℃ under a vacuum condition, and welding tabs to prepare the negative plate of the lithium ion secondary battery meeting the requirements.
(3) Preparing a lithium ion battery:
the positive electrode tab, the negative electrode tab and the separator (PE film) of the lithium ion secondary battery prepared according to the foregoing process were fabricated into a battery having a thickness of 8mm, a width of 60mm and a length of 130mm through a lamination process, and vacuum-baked at 85 ℃ for 10 hours, the electrolytes of examples 1-9 and comparative example 1 were injected, left to stand for 24 hours, and then charged to 4.35V with a constant current of 0.1C (200mA), then charged to a current drop of 0.05C (100mA) with a constant voltage of 4.35V, then discharged to 2.8V with a constant current of 0.1C (200mA), and then charged and discharged for 2 times, and finally charged to 3.8V with a constant current of 0.1C (200mA), thus completing the preparation of the lithium ion secondary battery.
The lithium ion batteries prepared in examples 1 to 9 and comparative example 1 were tested for high temperature storage performance, cycle performance, and high temperature storage gas generation performance, and the test results are shown in table 1.
The method for testing the high-temperature storage performance of the lithium ion battery comprises the following steps: at 25 ℃, the lithium ion secondary batteries prepared in examples 1 to 9 and comparative example 1 were charged to 4.35V at a constant current of 1C, further charged to a current of 0.05C at a constant voltage of 4.35V, and then discharged to 2.8V at a constant current of 1C, where the discharge capacity at this time is the discharge capacity of the lithium ion secondary battery before high-temperature storage; and then charging the lithium ion secondary battery to 4.35V by using a constant current of 1C, storing the lithium ion secondary battery at 60 ℃ for 30 days, after the storage is finished, placing the lithium ion secondary battery in an environment of 25 ℃, discharging the lithium ion secondary battery to 2.8V by using a constant current of 0.5C, then charging the lithium ion secondary battery to 4.35V by using a constant current of 1C, further charging to 1C by using a constant voltage of 4.35V, then discharging the lithium ion secondary battery to 2.8V by using a constant current of 1C, and finally, the discharge capacity of the last time is the discharge capacity of the lithium ion secondary battery after high-temperature storage. Capacity retention (%) after high-temperature storage of the lithium ion secondary battery [ discharge capacity after high-temperature storage of the lithium ion secondary battery/discharge capacity before high-temperature storage of the lithium ion secondary battery ] × 100%.
The test method of the high-temperature cycle performance of the lithium ion battery comprises the following steps: the high-temperature cycle performance of the lithium ion secondary batteries prepared in examples 1 to 9 and comparative example 1 was respectively tested by the following specific methods: at 45 ℃, the lithium ion secondary battery is charged to 4.35V by constant current of 1C, then charged to current of 0.05C by constant voltage of 4.35V, and then discharged to 2.8V by constant current of 1C, which is a charge-discharge cycle process, and the discharge capacity of the cycle is the discharge capacity of the first cycle. And (3) carrying out a cyclic charge-discharge test on the lithium ion secondary battery according to the mode, and taking the discharge capacity of the 800 th cycle.
Testing the high-temperature storage gas production performance of the lithium ion battery: at 25 ℃, the lithium ion secondary batteries prepared in examples 1 to 9 and comparative example 1 are charged to 4.35V at a constant current of 1C, further charged to a current of 0.05C at a constant voltage of 4.35V, and then discharged to 2.8V at a constant current of 1C, wherein the discharge capacity at this time is the discharge capacity of the lithium ion secondary battery before high-temperature storage; then, the lithium ion secondary battery was charged to 4.35V at a constant current of 1C, charged to a current of 0.05C at a constant voltage of 4.35V, and fully charged. The volume of the cell was measured by a drainage method and the thickness of the cell was measured by a micrometer.
And then storing the lithium ion battery at 60 ℃ for 30 days, after the storage is finished, placing the lithium ion secondary battery in an environment of 25 ℃, testing the volume of the battery by adopting a drainage method, and measuring the thickness of the battery by using a micrometer. And then discharging the lithium ion secondary battery to 2.8V by using a constant current of 0.5C, then charging the lithium ion secondary battery to 4.35V by using a constant current of 1C, further charging the lithium ion secondary battery to a constant voltage of 4.35V until the current is 1C, then discharging the lithium ion secondary battery to 2.8V by using a constant current of 1C, and finally obtaining the discharge capacity after the lithium ion secondary battery is stored at a high temperature.
The battery volume expansion rate (volume after storage/volume before storage-1)%.
TABLE 1
| Retention ratio of storage capacity/%) | Retention of circulating capacity/%) | 60 ℃/30d gassing swelling% | |
| Example 1 | 93 | 93 | 13 |
| Example 2 | 87 | 88 | 43 |
| Example 3 | 90 | 91 | 37 |
| Example 4 | 86 | 88 | 45 |
| Example 5 | 91 | 90 | 36 |
| Example 6 | 90 | 90 | 23 |
| Example 7 | 92 | 92 | 13 |
| Example 8 | 93 | 92 | 14 |
| Example 9 | 91 | 91 | 22 |
| Comparative example 1 | 84 | 86 | 55 |
As can be seen from the above table, as compared with the battery in which the bis (trimethylsilyl) borane sulfonic anhydride compound is not added, the capacity retention rate of the lithium ion secondary battery at 60 ℃ is increased, the storage gas generation is reduced, and the cycle capacity retention rate is improved with the addition of the bis (trimethylsilyl) borane sulfonic anhydride compound, as can be seen from the comparison between example 1 and comparative example 1.
As can be seen from a comparison of examples 7-8 with example 1, 3-propane sultone, or vinylene carbonate, in combination with bis (trimethylsilyl) boranyl sulfonic anhydride, also achieves superior high temperature performance slightly lower than that achieved with the addition of vinyl sulfate.
The comparison between example 9 and example 1 and the comparison between comparative example 1 shows that the additives of lithium difluorophosphate and lithium bis (fluorosulfonyl) imide are matched with the bis (trimethylsilyl) boryl sulfonic anhydride compound to obtain excellent high-temperature performance.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (10)
1. The electrolyte is characterized by comprising an organic solvent, lithium salt and an additive, wherein the additive comprises a bis (trimethylsilyl) borane sulfonic anhydride compound shown as a formula 1,
2. The electrolyte according to claim 1, wherein the bis (trimethylsilyl) boryl sulfonic anhydride compound accounts for 0.01 to 3% by mass, preferably 0.1 to 1% by mass of the electrolyte, based on 100% by mass of the electrolyte.
3. The electrolyte of claim 1 or 2, wherein the additive comprises any one of the compounds of formula 2 to formula 6 or a combination of at least two of the compounds,
4. the electrolyte of any one of claims 1-3, wherein the additives further comprise a high temperature additive and a lithium salt additive;
preferably, the high temperature additive comprises any one of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, vinyl sulfate, 1, 3-propane sultone, tris (trimethylsilane) borate or tris (trimethylsilane) phosphate or a combination of at least two thereof;
preferably, the high temperature additive comprises vinyl sulfate;
preferably, the high-temperature additive accounts for 0.01-3% of the electrolyte by mass percent, preferably 0.1-2% of the electrolyte by mass percent, based on 100% of the electrolyte by mass percent;
preferably, the lithium salt additive comprises lithium difluorophosphate and lithium bis-fluorosulfonylimide;
preferably, the mass fraction of the lithium difluorophosphate in the electrolyte is 0.1-1.5% based on 100% of the electrolyte;
preferably, the mass fraction of the lithium bis (fluorosulfonate) imide in the electrolyte is 0.1-10% based on 100% of the electrolyte.
5. The electrolyte of any one of claims 1-4, wherein the organic solvent comprises cyclic carbonates and chain acid esters;
preferably, the cyclic carbonate comprises any one of ethylene carbonate, propylene carbonate, butylene carbonate or gamma-butyrolactone or a combination of at least two of the above;
preferably, the chain acid ester includes any one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, or ethyl butyrate, or a combination of at least two thereof.
6. The electrolyte according to claim 5, wherein the volume ratio of the cyclic carbonate to the chain acid ester is (10-40): (60-90), preferably (15-40): (60-85);
preferably, the organic solvent accounts for 65.6-89.6% of the electrolyte by mass fraction of 100%.
7. The electrolyte of any one of claims 1 to 6, wherein the lithium salt comprises any one or a combination of at least two of lithium hexafluorophosphate, lithium tetrafluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) phosphate, lithium bis (trifluoromethylsulfonyl) imide, or lithium perchlorate;
preferably, the lithium salt comprises lithium hexafluorophosphate.
8. The electrolyte according to claim 7, wherein the lithium hexafluorophosphate accounts for 10 to 20% by mass of the electrolyte, based on 100% by mass of the electrolyte;
preferably, the lithium salt accounts for 10-20% of the electrolyte by mass percent, based on 100% of the electrolyte by mass percent.
9. A lithium ion battery comprising the electrolyte of any one of claims 1-8;
the lithium ion battery also comprises a positive pole piece and a negative pole piece.
10. The lithium ion battery according to claim 9, wherein the material of the positive electrode sheet comprises a transition metal oxide of lithium and/or a transition metal phosphate compound of lithium;
preferably, the transition metal oxide of lithium comprises LiCoO 2 、LiNi x Co y Mn z O 2 、LiNi x Mn y O 2 、LiMn 2 O 4 、LiMnO 2 、Li 2 MnO 4 、Li 1+a Mn 1-x M x O 2 、LiCo 1-x M x O 2 、LiMn 1-x M x O 4 Or Li 2 Mn 1-x O 4 Any one or a combination of at least two of them, wherein 0. ltoreq. a<0.2，0≤x≤1，0≤y≤1，0≤z≤1；
Preferably, the lithium transition metal phosphate compound comprises LiFePO 4 、LiMnPO 4 、LiCoPO 4 Or LiFe 1-x M x PO 4 Any one or the combination of at least two of the above, wherein M is selected from any one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V and Ti, and x is more than or equal to 0 and less than or equal to 1;
preferably, the material of the negative electrode plate comprises any one or a combination of at least two of a carbonaceous material, an alloy material or a lithium-containing metal composite material;
preferably, the material of the negative electrode plate comprises any one or a combination of at least two of natural graphite, artificial graphite, soft carbon, hard carbon, lithium titanate, silicon-carbon alloy or silicon-oxygen alloy.
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| CN116207351A (en) * | 2023-05-05 | 2023-06-02 | 宁德时代新能源科技股份有限公司 | Electrolyte, lithium secondary battery and electricity utilization device |
| CN116207351B (en) * | 2023-05-05 | 2024-01-16 | 宁德时代新能源科技股份有限公司 | Electrolyte, lithium secondary battery and electricity utilization device |
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