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CN118676373B - A lithium ion battery - Google Patents

A lithium ion battery Download PDF

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Publication number
CN118676373B
CN118676373B CN202411147243.8A CN202411147243A CN118676373B CN 118676373 B CN118676373 B CN 118676373B CN 202411147243 A CN202411147243 A CN 202411147243A CN 118676373 B CN118676373 B CN 118676373B
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lithium
electrolyte
positive electrode
low
carbonate
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CN118676373A (en
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肖阳
杨睿
李枫
于丽娟
廖兴群
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Shenzhen Highpower Technology Co Ltd
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Shenzhen Highpower Technology Co Ltd
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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • 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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
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  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)

Abstract

本申请涉及一种锂离子电池。该锂离子电池包括正极极片、负极极片、隔膜和电解液，正极极片包括正极集流体以及涂覆于正极集流体表面的正极材料层，正极材料层包括磷酸钛铝锂；电解液包括添加剂A，添加剂A的化学结构式如式I所示：；其中，R1、R2、R3各自独立地选自被氟取代或未取代的碳原子不超过4的烃基。本申请技术方案，能够在正负极界面形成稳定且低阻抗的钝化层，提高低温下的电导率，同时降低低温环境下正极和负极侧的极化作用，提升锂离子电池的低温大倍率放电和低温长循环性能。The present application relates to a lithium-ion battery. The lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer coated on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises lithium aluminum titanium phosphate; and the electrolyte comprises an additive A, wherein the chemical structure of the additive A is as shown in Formula I: ; wherein R 1 , R 2 , and R 3 are each independently selected from hydrocarbon groups with no more than 4 carbon atoms substituted or unsubstituted by fluorine. The technical solution of the present application can form a stable and low-impedance passivation layer at the interface between the positive and negative electrodes, improve the electrical conductivity at low temperatures, and reduce the polarization effect on the positive and negative electrode sides in low temperature environments, thereby improving the low-temperature high-rate discharge and low-temperature long-cycle performance of lithium-ion batteries.

Description

Lithium ion battery
Technical Field
The application relates to the technical field of lithium ion batteries, in particular to a lithium ion battery.
Background
The lithium ion battery is the preferred energy storage carrier for products such as notebook computers, mobile phones, cameras and the like and consumer electronic products such as new energy vehicles and the like because of the advantages of high energy density, long cycle life and the like.
With the continuous development of application products, the performance requirements on lithium ion batteries are higher and higher, especially when the running conditions deviate from room temperature, such as extremely low temperature conditions (less than or equal to-10 ℃), the ionic conductivity of the electrolyte is reduced, the solvation/desolvation of lithium ions in the electrolyte becomes more difficult, and meanwhile, the migration rate of lithium ions in solid phase anode and cathode materials and the interface between the electrode materials and the electrolyte (comprising SEI films and CEI films) is also greatly reduced, so that the battery cell is polarized; when discharging, the voltage of the battery core can reach the set cut-off voltage in advance, so that the actual discharge capacity is reduced, the battery performance is seriously deteriorated, and even the battery is possibly invalid and potential safety hazard is generated. Performance degradation of lithium ion batteries in low temperature environments can limit the use scenarios for application products.
Aiming at the problem of low-temperature performance deterioration of lithium ion batteries, the current improvement means mainly focuses on developing low-viscosity solvents, such as carboxylic esters are adopted to replace carbonic esters, but electrochemical windows of the carboxylic esters are narrower than those of the carbonic esters, so that the impedance of the batteries increases in the later period of circulation, and further lithium precipitation phenomenon is generated, the batteries fail, and the problem of application limitation of the lithium ion batteries in extremely low-temperature environments cannot be effectively solved.
Disclosure of Invention
In order to solve or partially solve the problems in the related art, the application provides a lithium ion battery, which can form a stable and low-impedance passivation layer at the interface of a positive electrode and a negative electrode, improve the conductivity at low temperature, reduce the polarization effect of the positive electrode and the negative electrode side in a low-temperature environment, and improve the low-temperature high-rate discharge and low-temperature long-cycle performance of the lithium ion battery.
The application provides a lithium ion battery, which comprises a positive electrode plate, a negative electrode plate, a diaphragm and electrolyte, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer coated on the surface of the positive electrode current collector, and the positive electrode material layer comprises lithium aluminum titanium phosphate;
The electrolyte comprises an additive A, wherein the chemical structural formula of the additive A is shown as formula I:
；
Wherein R 1、R2、R3 is each independently selected from hydrocarbyl groups substituted or unsubstituted with fluorine having no more than 4 carbon atoms.
In some alternative embodiments, the positive electrode sheet and the electrolyte satisfy:
；
wherein c (%) represents the mass percentage of the additive A in the electrolyte;
L (%) represents the mass percentage of lithium aluminum titanium phosphate in the positive electrode material layer;
f (g/Ah) represents the injection coefficient of the electrolyte in the lithium ion battery;
d (μm) represents the D50 particle diameter of the lithium aluminum titanium phosphate in the positive electrode material layer.
In some alternative embodiments, the electrolyte comprises the following additives a in percentage by mass: c is more than or equal to 0.3 and less than or equal to 1.2.
In some alternative embodiments, the mass percentage content L% of the lithium aluminum titanium phosphate in the positive electrode material layer satisfies: l is more than or equal to 0.5 and less than or equal to 1.0.
In some alternative embodiments, the electrolyte injection coefficient f (g/Ah) of the lithium ion battery satisfies: f is more than or equal to 1.5 and less than or equal to 1.8.
In some alternative embodiments, the D50 particle size D (μm) of the lithium aluminum titanium phosphate in the positive electrode material layer satisfies: d is more than or equal to 0.2 and less than or equal to 0.5.
In some alternative embodiments, the additive a is selected from at least one of the following compounds: n-methylphosphonic anhydride, n-ethylphosphoric anhydride, n-propylphosphoric anhydride, n-butylphosphoric anhydride, pentafluoroethyl phosphoric anhydride.
In some alternative embodiments, the electrolyte further comprises a lithium salt selected from at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluorooxalato borate, lithium bisoxalato borate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethyl imide, lithium difluorooxalato phosphate, lithium perchlorate;
the mass percentage of the lithium salt in the electrolyte is 8-15%.
In some alternative embodiments, the lithium salt comprises lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide, wherein the mass percentage of lithium bis (fluorosulfonyl) imide in the electrolyte is 2-6%.
In some alternative embodiments, the electrolyte further comprises an organic solvent selected from at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl difluoroacetate; the mass percentage of the organic solvent in the electrolyte is 73-85.2%.
In some alternative embodiments, the organic solvent at least comprises propylene carbonate and ethyl propionate, wherein the mass percentage of ethyl propionate in the electrolyte is 50% -65%.
In some alternative embodiments, the electrolyte further includes an additive B including at least one of a nitrile compound, a carbonate compound, and a sulfate compound.
In some alternative embodiments, the nitrile compound is selected from at least one of adiponitrile, succinonitrile, 1,3, 6-hexane-trimethylnitrile, trans-hexenedinitrile, fumaric dinitrile, 1, 2-bis (cyanoethoxy) ethane and 1,2, 3-tris (cyanoethoxy) propane; the mass percentage of the nitrile compound in the electrolyte is 2% -4%.
In some alternative embodiments, the carbonate compound is selected from at least one of ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, and bis-fluoroethylene carbonate; the mass percentage of the carbonic ester compound in the electrolyte is 4-6%.
In some alternative embodiments, the sulfate compound is selected from at least one of vinyl sulfate, vinyl sulfite, vinyl 4-methylsulfate, dimethyl sulfite, and diethyl sulfite; the mass percentage content of the sulfate compound in the electrolyte is 0.5% -1%.
The technical scheme provided by the application can comprise the following beneficial effects:
According to the scheme, the solid electrolyte lithium aluminum titanium phosphate LATP is added in the positive electrode material, and the three-dimensional ion migration channel is arranged in the LATP framework, so that the migration rate of lithium ions at the positive electrode interface can be improved, and the charge and discharge performance of the battery can be improved; meanwhile, LATP can also catalyze an additive A phosphoric anhydride compound to form an interface protection layer with low impedance and high stability at the interface of the positive electrode, so that the conductivity of the lithium ion battery at low temperature can be improved, and meanwhile, the polarization effect of the positive electrode side in an extremely low temperature environment is reduced, so that the lithium ion battery can realize high-rate discharge and low-temperature long-cycle performance when applied in the extremely low temperature environment.
Furthermore, the application can realize the rapid transmission of lithium ions in the solvent by combining a low-viscosity solvent system and lithium salt combination of lithium difluorosulfimide and lithium hexafluorophosphate with high conductivity and matching with the additive A, simultaneously achieve the purpose of reducing the polarization effect of the positive electrode and the negative electrode in an extremely low-temperature environment, and improve the low-temperature discharge performance and the cycle performance of the lithium ion battery in the low-temperature environment.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application as claimed.
Detailed Description
In order that the invention may be readily understood, the invention will be described in detail. Before the present invention is described in detail, it is to be understood that this invention is not limited to particular embodiments described. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any or all possible combinations of one or more of the associated listed items.
Where a range of values is provided, it is understood that each intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the application. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the application, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the application. In the description of the present application, "plurality" means two or more unless specifically defined otherwise.
Unless defined otherwise, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although any methods and materials equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described.
Lithium ions at extremely low temperature can seriously reduce migration rate of anode and cathode materials and interfaces between electrolyte and materials, so that cell polarization is caused. The cell polarization during discharge produces over-potential, which can lead to the cell voltage reaching the set cut-off voltage in advance and lead to the reduction of the actual discharge capacity. When charged, the overpotential generated by the polarization of the battery results in reduced charge capacity and irreversible lithium deposition due to the negative electrode potential being lower than the lithium reduction potential. Irreversible lithium deposition can deteriorate cell capacity and can also puncture the separator and reduce electrolyte solvents, thereby creating flammable gas leading to safety concerns. The above factors deteriorate the performance of lithium ion batteries in low temperature environments, limiting the use of consumer electronics.
In view of the above problems, the embodiment of the application provides a lithium ion battery, which can form a stable and low-impedance passivation layer at the interface of the anode and the cathode, improve the conductivity at low temperature, reduce the polarization effect of the anode and the cathode in the extremely low temperature environment, and improve the extremely low-temperature high-rate discharge and the low-temperature long-cycle performance of the lithium ion battery.
The lithium ion battery provided by the embodiment of the application comprises a positive electrode plate, a negative electrode plate, a diaphragm and electrolyte. The positive electrode plate comprises a positive electrode current collector and a positive electrode material layer coated on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises titanium aluminum lithium phosphate; the electrolyte comprises an additive A, and the chemical structural formula of the additive A is shown as formula I:
；
In formula I, R 1、R2、R3 is each independently selected from hydrocarbyl groups substituted or unsubstituted with fluorine having no more than 4 carbon atoms.
According to the embodiment of the application, the solid electrolyte lithium aluminum titanium phosphate LATP is added in the positive electrode material, and the LATP framework is internally provided with the three-dimensional ion migration channel, so that the migration rate of lithium ions at the positive electrode interface can be improved, and the charge and discharge performance of the battery can be improved; meanwhile, LATP can also catalyze the additive A phosphoric anhydride to form an interface protection layer with low impedance and high stability at the interface of the positive electrode, so that the conductivity of the lithium ion battery at low temperature can be improved, and meanwhile, the polarization effect of the positive electrode side in an extremely low temperature environment is reduced, so that the lithium ion battery can realize high-rate discharge and low-temperature long-cycle performance when applied in the extremely low temperature environment.
In some embodiments, R 1、R2、R3 in additive A may be the same or different; preferably, R 1、R2、R3 are the same groups. In some preferred embodiments, additive a may be selected from at least one of the following compounds: n-methylphosphonic anhydride (formula I-1, CAS No. 82593-65-5), n-ethylphosphoric anhydride (formula I-2, CAS No. 145007-52-9), n-propylphosphoric anhydride (formula I-3, CAS No. 68957-94-8), n-butylphosphoric anhydride (formula I-4, CAS No. 163755-62-2), pentafluoroethyl phosphoric anhydride (formula I-5, CAS No. 103304-98-9), and the like.
The electrolyte containing phosphoric anhydride in the embodiment of the application can form a compact SEI film and CEI film at the interface of the positive electrode and the negative electrode, thereby effectively reducing the decomposition of the electrolyte at the interface of the positive electrode and the negative electrode, absorbing hydrofluoric acid generated by side reaction in the electrolyte, reducing the damage of the hydrofluoric acid to the positive electrode material and the negative electrode material, and improving the cycle performance of the battery; meanwhile, the interface film formed at the electrode interface has smaller impedance, so that the increase of interface impedance in the cycling process can be effectively reduced, the application of the titanium aluminum lithium phosphate solid electrolyte in the positive electrode plate can promote the film formation of phosphoric anhydride at the positive electrode, the increase of negative electrode impedance caused by excessive participation of phosphoric anhydride in the film formation of the negative electrode is reduced, the migration rate of lithium ions in the battery can be effectively improved by combining the two components, the increase of interface impedance in the cycling process can be reduced, and the high-rate discharge performance and the long-cycle performance of the lithium ion battery in the application in an extremely low-temperature environment are improved.
In some embodiments, in a lithium ion battery, the positive electrode sheet and the electrolyte satisfy:
；
Wherein c (%) represents the mass percentage of the additive A in the electrolyte; l (%) represents the mass percentage of lithium aluminum titanium phosphate in the positive electrode material layer; f (g/Ah) represents the injection coefficient of the electrolyte in the lithium ion battery; d (μm) represents the D50 particle diameter of the lithium aluminum titanium phosphate in the positive electrode material layer.
According to the embodiment of the application, the relationship between the positive electrode plate and the electrolyte is optimized, so that the electrolyte is adapted to the composite positive electrode doped with the solid electrolyte LATP, an interface protection layer with low impedance and high stability is formed on the surface of the composite positive electrode, lithium ions can be quickly migrated between the positive electrode plate and the negative electrode plate in an extremely low-temperature environment, and the low-temperature performance of the lithium ion battery is improved.
The lithium ion battery has the following electrolyte injection coefficient f (g/Ah): f.ltoreq.1.5.ltoreq.1.8, for example, 1.5g/Ah, 1.6g/Ah, 1.7g/Ah, 1.8g/Ah or any value within the above-mentioned range. The electrolyte injection coefficient is too low, the electrolyte is difficult to uniformly infiltrate the whole battery cell, so that additives in the electrolyte are difficult to uniformly form a film on the surface of the battery cell, and the protection of the local interface of the battery cell is insufficient; the too high liquid injection coefficient can easily cause the problems of poor packaging, excessive floating liquid and the like, and the safety problem is easy to cause.
The mass percentage content c% of the additive A in the electrolyte of the lithium ion battery is as follows: 0.3.ltoreq.c.ltoreq.1.2, for example, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2% or any value within the above range. The content of phosphoric anhydride in the electrolyte is too low, the content of a low-impedance interface film formed on the surface of an electrode is limited, and the content of a CEI film of an anode interface is limited, so that the effect of reducing the impedance of the anode interface is difficult to achieve; and when the content of the phosphoric anhydride is too high, the impedance of the negative electrode can be increased, the lithium ion migration of the negative electrode is not facilitated, meanwhile, the viscosity of the electrolyte can be increased, the low-temperature charge and discharge performance of the battery is deteriorated, and the battery is not facilitated to be applied in a low-temperature environment.
In the lithium ion battery, the mass percentage content L% of the lithium aluminum titanium phosphate in the positive electrode material layer meets the following conditions: l.ltoreq.0.ltoreq.1.0, for example, may be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or any value within the above-mentioned range. The solid-state lithium aluminum phosphate electrolyte is used as an additive component of the positive electrode material layer, is used as a composite material consisting of phosphate, titanate, aluminate and lithium salt, has a stable structure and a large specific surface area, is favorable for adsorbing and catalyzing phosphoric anhydride to form a low-impedance passivation layer at the positive electrode, and further reduces polarization at the positive electrode side under low-temperature discharge. The effect of the excessively low addition of the solid-state electrolyte of the aluminum titanium lithium phosphate on the improvement of the film-forming catalytic efficiency of the phosphoric anhydride is not obvious, the excessively high addition of the solid-state electrolyte of the aluminum titanium lithium phosphate can increase the production cost, simultaneously worsen the cycle stability of the battery, reduce the content of positive active substances in the positive electrode material layer, further lead the energy density of the battery to be substandard, and be unfavorable for the low-temperature long-cycle performance of the battery.
In the lithium ion battery, the D50 particle diameter D (mum) of the lithium aluminum titanium phosphate in the positive electrode material layer meets the following conditions: d is 0.2.ltoreq.0.5, and may be, for example, 0.2. Mu.m, 0.25. Mu.m, 0.3. Mu.m, 0.35. Mu.m, 0.4. Mu.m, 0.45. Mu.m, 0.5. Mu.m, or any value within the above range. It is understood that the D50 particle size of the lithium aluminum titanium phosphate is 50% or more of the particle size of the lithium aluminum titanium phosphate. The smaller the particle size of the lithium aluminum titanium phosphate is, the larger the specific surface area is, and the higher the efficiency of catalyzing the film formation of the phosphoric anhydride additive in the positive electrode is; however, the smaller the particle size of the lithium aluminum titanium phosphate, the higher the production cost, and the more easily the lithium metal contacts the lithium to generate oxidation-reduction reaction, so that the battery is invalid and the low-temperature long-cycle performance of the battery is not facilitated.
In some embodiments, the electrolyte further comprises a lithium salt. The lithium salt may be at least one selected from lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluorooxalato borate, lithium bisoxalato borate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethyl imide, lithium difluorooxalato phosphate, and lithium perchlorate.
The content of the lithium salt in the electrolyte is 8% to 15% by mass, and may be, for example, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% by mass or any value within the above range. The use amount of lithium salt is increased, the viscosity of the electrolyte is increased when the lithium salt is applied in a low-temperature environment, and the low-temperature discharge performance of the battery is deteriorated when the lithium salt is excessively high; and too low usage amount of lithium salt can also cause low lithium ion conductivity of the electrolyte, so that the concentration polarization level of the battery core is increased, and the battery is not beneficial to being applied in a low-temperature scene.
In some preferred embodiments, the lithium salt comprises lithium hexafluorophosphate and lithium difluorosulfimide, and the lithium salt combination has good compatibility with organic solvents and additives, and can maintain high conductivity of the lithium ion battery in a low-temperature environment; and the negative electrode SEI film are matched to participate in the film formation of the negative electrode, so that the negative electrode SEI film has stability and low impedance, the dynamic performance of the negative electrode is improved, and the low-temperature long-cycle performance and the low-temperature charge-discharge performance of the battery are improved. Meanwhile, when lithium salt of lithium hexafluorophosphate and lithium difluorosulfimide are adopted in the electrolyte, the film formation of the phosphoric anhydride additive on the negative electrode can be better than that of the phosphoric anhydride additive, so that the increase of the negative electrode impedance caused by the phosphoric anhydride additive is reduced, the dynamic performance of the negative electrode is facilitated, and the low-temperature cycle and the rate capability of the battery are improved.
In the lithium salt composition, the mass percentage of lithium difluorosulfimide in the electrolyte is preferably 2% to 6%, and may be, for example, 2%, 3%, 3.7%, 4%, 4.5%, 5%, 6%, or any value within the above range. The lithium bis (fluorosulfonyl) imide has an excessively large duty ratio, has a remarkable viscosity increasing effect on the electrolyte, and enhances the corrosion on the aluminum foil of the positive current collector; if the proportion of lithium bisfluorosulfonyl imide is too low, it is completely consumed in the formation stage, and the electrolyte conductivity level cannot be increased.
Further, the mass percentage ratio of the additive A and lithium difluorosulfimide in the electrolyte is 0.12 to 0.8, for example, 0.12, 0.15, 0.18, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.8 or any value within the above range, preferably 0.15 to 0.25.
According to the embodiment of the application, the battery has good rate capability by optimizing the total mass of lithium salt and the proportion of lithium bis (fluorosulfonyl) imide in the electrolyte.
In some embodiments, the electrolyte further comprises an organic solvent. The organic solvent may be at least two selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl difluoroacetate.
The mass percentage of the organic solvent in the electrolyte is 73% -85.2%, for example, 73%, 75%, 77.5%, 80%, 82.5%, 85.2% or any value in the above range.
In some preferred embodiments, the organic solvent comprises at least a combination of both propylene carbonate and ethyl propionate. The solvent system is used as a basic solvent or a conventional solvent of the electrolyte provided by the embodiment of the application, has a lower melting point and a higher dielectric constant, and can still keep lower viscosity when being applied in a low-temperature environment, so that the battery has good discharge performance in an extremely low-temperature environment.
In the solvent system, the mass percentage of ethyl propionate in the electrolyte is 50% to 65%, and may be, for example, 50%, 55%, 58%, 60%, 65%, or any value within the above range.
According to the electrolyte provided by the embodiment of the application, through the combination of the low-viscosity solvent system and the lithium salt of the lithium difluorosulfimide and the lithium hexafluorophosphate with high conductivity, when the electrolyte is matched and combined with the additive A for use, the rapid transmission of lithium ions in the solvent can be realized, and the low-temperature discharge performance of the lithium ion battery in a low-temperature environment is improved.
In some embodiments, the electrolyte further comprises an additive B comprising at least one of a nitrile compound, a carbonate compound, a sulfate compound. The additive B is used as a conventional additive of the electrolyte, and when the additive B is combined with the additive A, the additive B is used cooperatively to help form a stable and low-impedance passivation protection layer at the interface of the anode and the cathode, so that the high-rate discharge and long-cycle performance of the battery under the low-temperature, especially extremely-low-temperature conditions are improved.
Specifically, the nitrile compound may be at least one selected from adiponitrile, succinonitrile, 1,3, 6-hexane-trimethylnitrile, trans-hexenedinitrile, fumaric dinitrile, 1, 2-di (cyanoethoxy) ethane and 1,2, 3-tri (cyanoethoxy) propane.
The nitrile compound may be 2% to 4% by weight of the total electrolyte, for example, 2%, 3%, 4% by weight, or any value within the above range. The use amount of the nitrile compound is too high, so that the impedance of the positive electrode of the battery is deteriorated, and the low-temperature discharge performance of the battery is deteriorated; the use amount of the nitrile compound is too low, so that the protective effect on the anode is not obvious, the anode metal is easy to dissolve out, and the low-temperature cycle performance of the battery applied in a low-temperature scene is not facilitated.
The carbonate compound is at least one selected from ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate and bis-fluoroethylene carbonate; preferably fluoroethylene carbonate.
Further, the carbonate compound such as fluoroethylene carbonate accounts for 4% to 6%, for example, 4%, 5%, 6%, etc. or any value within the above range of the total mass of the electrolyte. The fluoroethylene carbonate can form a stable and low-impedance SEI film on the negative electrode, and can reduce side reactions of nitrile compound additives, phosphoric anhydride additives, solvents and the like on the negative electrode, thereby further deteriorating the impedance of the negative electrode.
The sulfate compound is selected from at least one of vinyl sulfate, vinyl sulfite, 4-methyl vinyl sulfate, dimethyl sulfite and diethyl sulfite; vinyl sulfate is preferred.
Further, the sulfate compound such as vinyl sulfate accounts for 0.5% to 1%, for example, 0.5%, 0.8%, 1%, etc. or any value within the above range of the total mass of the electrolyte. The vinyl sulfate can form stable SEI films with low impedance at the positive electrode and the negative electrode, so that side reactions of solvents at the positive electrode and the negative electrode are reduced, and the interface impedance of the positive electrode and the negative electrode is reduced.
The electrolyte is one of the main materials of lithium ion batteries, and is one of the important factors affecting the performance of the lithium ion secondary batteries. Wherein, the organic solvent, lithium salt and additive are the main components of the electrolyte, which has great influence on the cycle, impedance, dynamics and other performances of the battery. According to the embodiment of the application, through optimizing the composition of the electrolyte, the composition of the organic solvent, the composition of the lithium salt, the composition of the additive and other parameters in the electrolyte are comprehensively designed, so that additives such as phosphoric anhydride, fluoroethylene carbonate, ethylene sulfate, nitrile compounds and the like are cooperatively matched, the polarization and impedance of the electrode are reduced, the side reaction of the electrolyte on the surface of the electrode is reduced, the lithium ion can maintain good transmission performance in an extremely low-temperature environment, the high-power discharge of the lithium ion battery in the extremely low-temperature environment is realized, and the lithium ion battery has good low-temperature long-cycle performance.
In some embodiments, the positive electrode current collector according to the present application is not particularly limited, and may be any material known to be suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector may be a metal material such as aluminum, stainless steel, nickel plating, titanium, tantalum, or a carbon material such as carbon cloth or carbon paper.
In some embodiments, the positive electrode material layer is formed by coating a positive electrode slurry on the surface of the positive electrode current collector. The positive electrode slurry comprises a positive electrode active material, a conductive agent and a binder besides the titanium aluminum lithium phosphate solid electrolyte.
The positive electrode active material comprises one or more than one of lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate and ternary LiNi xCoyMnzO2 material (wherein x+y+z=1, and x is larger than or equal to y).
The conductive agent includes, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
The binder includes, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymers, tetrafluoroethylene-hexafluoropropylene copolymers, and fluoroacrylate resins.
The positive electrode plate provided by the embodiment of the application is prepared by the following method:
Mixing an anode active material, a lithium aluminum titanium phosphate solid electrolyte, a conductive agent and a binder according to mass ratio to form uniform anode slurry;
and uniformly coating the positive electrode slurry on the surface of a positive electrode current collector, and then drying, rolling, compacting and other working procedures to obtain the positive electrode plate.
According to the embodiment of the application, the high-rate discharge and long circulation of the battery cell under the extremely low temperature environment are realized by optimizing the composition of the electrolyte and the composition of the anode material. For the electrolyte, the combined use of additives such as phosphoric anhydride compound, fluoroethylene carbonate, nitrile compound, ethylene sulfate and the like and the combined use of solid electrolyte of aluminum titanium lithium phosphate added in the positive electrode material can synergistically improve the problems of electrolyte ion conductivity reduction, electrode polarization severity and the like when the battery is applied in low-temperature environments, especially in very low-temperature environments, so that the battery has low-temperature long-cycle performance and high-power discharge performance when the battery is applied in low-temperature environments.
In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode material layer coated on a surface of the negative electrode current collector. The negative electrode current collector may be selected from a metal foil or a composite current collector, for example, may be selected from copper foil.
In some embodiments, the anode material layer includes an anode active material, a binder, and a conductive agent.
Wherein the negative active material includes, but is not limited to, one or more of graphite, hard carbon, silicon oxygen compounds, and silicon carbon compounds.
The conductive agent includes, but is not limited to, one or more of conductive carbon black, acetylene black, ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, superconducting carbon.
The binder includes, but is not limited to, one or more of styrene-butadiene rubber, aqueous acrylic resin, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-vinyl acetate copolymer, polyacrylic acid, carboxymethyl cellulose, polyvinyl alcohol, and polyvinyl butyral.
In some embodiments, the separator according to the present application may be arbitrarily selected from known porous structure separators having good chemical and mechanical stability. The material of the separator may be at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.
The preparation process of the battery is well known to those skilled in the art, and the present application is not particularly limited. For example, the electrochemical device may be manufactured by: the positive electrode plate and the negative electrode plate are overlapped through a diaphragm, the positive electrode plate and the negative electrode plate are placed into a shell after being wound, folded and the like according to the requirement, electrolyte is injected into the shell, and the shell is sealed, wherein the diaphragm is provided by the application. In addition, an overcurrent prevention element, a guide plate, or the like may be placed in the case as needed, thereby preventing the pressure inside the electrochemical device from rising and overcharging and discharging.
The application also provides an electric device or various energy storage systems using batteries as energy storage elements. The electric device comprises, but is not limited to, a mobile phone, a tablet, a computer, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft and the like.
In order that the application may be more readily understood, the application will be further described in detail with reference to the following examples, which are given by way of illustration only and are not limiting in scope of application. The starting materials or components used in the present application may be prepared by commercial or conventional methods unless specifically indicated.
Example 1
(1) Preparation of electrolyte
Propylene Carbonate (PC) and Ethyl Propionate (EP) were mixed in a mass ratio of 25:75 in a glove box in an argon atmosphere having a water content of <1ppm, and the following components were added to the total mass of the electrolyte as shown in table 1 to be uniformly mixed, thereby preparing an electrolyte.
Lithium salt: 13% lithium hexafluorophosphate (LiPF 6) +2% lithium bis-fluorosulfonyl imide (LiFSI)
Additive a phosphoric anhydride compound: 0.3% n-propyl phosphoric anhydride (T3P)
Additive B:2% Succinonitrile (SN) +6% fluoroethylene carbonate (FEC) +0.8% ethylene sulfate (DTD)
(2) Preparation of positive electrode plate
Fully stirring and mixing positive active materials lithium cobalt oxide (LiCoO 2), lithium aluminum titanium phosphate solid electrolyte (with the particle size D50 of 0.5 mu m), conductive agent carbon black, binder polyvinylidene fluoride PVDF and carbon nano tube CNT in a mass ratio of 97.5:0.5:0.6:1:0.4 in an N-methyl pyrrolidone solvent to form uniform positive electrode slurry;
And uniformly coating the anode slurry on an anode current collector Al foil, and then performing procedures such as drying, rolling, compacting (the compaction density is 4.28g/cm 3) and the like to obtain the anode plate.
(3) Preparation of negative electrode plate
The preparation method comprises the steps of fully stirring and mixing negative electrode active material graphite, adhesive styrene-butadiene rubber and thickener sodium carboxymethylcellulose according to a mass ratio of 98.2:1:0.8 in a proper amount of deionized water solvent to form uniform negative electrode slurry;
And uniformly coating the negative electrode slurry on a negative electrode current collector copper foil, and performing procedures such as drying, rolling, compacting (the compacted density is 1.78g/cm 3) and the like to obtain the negative electrode plate.
(4) Preparation of lithium ion batteries
PE porous polymer film is used as a separation film.
And sequentially stacking the positive pole piece, the diaphragm and the negative pole piece, enabling the diaphragm to be positioned between the positive pole piece and the negative pole piece, playing an isolating role, and winding the stacked pole piece and the isolating film to obtain the winding core. And (3) placing the bare coil core in an aluminum plastic film formed by punching, injecting the electrolyte prepared by the method into the baked and dried battery core with the injection coefficient of 1.5g/Ah, and performing the procedures of vacuum packaging, standing, formation and the like to complete the preparation of the lithium ion battery.
Examples 2 to 19 and comparative examples 1 to 4 were conducted in the same manner as in example 1 except that the kind and content of additive A in the electrolyte, the amount of LATP in the positive electrode sheet, the particle size, and the pouring coefficient of the electrolyte were specified in Table 1.
Lithium ion battery performance test:
(1) -29 ℃ rate discharge performance test:
Charging to 4.48V at room temperature with constant current and constant voltage of 0.5C, and standing for 10 min with cutoff current of 0.05C; constant current discharge to 3V at 0.2C, recording discharge capacity as C1, and standing for 10 min. 0.5C constant current and constant voltage charge to 80% C1 capacity, the off-current was 0.05C. After 3 hours of rest at-29 ℃, 10.67W for 5s, 14.35W for 1s, 20.49W for 5ms, 11.23W for 3s, 13.20W for 2s, 7.3W for 10s, 4.21W for 60s, the discharge process voltage no less than 3V is recorded as a "pass" test, otherwise as a "fail" test. The test results are recorded in table 1.
(2) -10 ℃ Cycle performance test:
discharging to 3.0V at a given current of 0.2C under ambient conditions of 25 ℃; standing for 5min; charging to an upper limit voltage with a constant current and a constant voltage of 0.5C, and cutting off the current by 0.05C; after 10min of rest, 0.2C was discharged to 3.0V, and the initial discharge capacity was recorded.
Charging the separated battery to 4.48V at a constant current and constant voltage of 0.5C at-10 ℃ and cutting off the current by 0.05C; then discharging to 3.0V according to a constant current of 0.5C, and calculating the capacity retention rate of the battery after 500 times of charging and discharging, wherein the calculation formula is as follows:
Cycle capacity retention at 500 weeks (%) = (cycle discharge capacity at 500 weeks/initial cycle discharge capacity) ×100%.
The average capacity retention rate for each group of 5 batteries is reported in table 1.
TABLE 1
Remarks: T3P represents n-propyl phosphoric anhydride, T4P represents n-butyl phosphoric anhydride, and T2FP represents pentafluoroethyl phosphoric anhydride.
Comparison of the data of comparative examples 1-3 shows that when a phosphoric anhydride compound is added to the electrolyte as additive A, but no LATP is contained in the positive electrode sheet, the effect of improving the low-temperature rate discharge performance of the battery is not achieved, and the low-temperature long-cycle performance of the battery is deteriorated as the content of the phosphoric anhydride compound in the electrolyte increases.
Comparison of the data of comparative example 1, comparative example 4 and example 1 shows that when LATP is added to the positive electrode sheet, but phosphoric anhydride compound is not added to the electrolyte as additive a, the low-temperature rate discharge performance of the battery still cannot be improved. When the phosphoric anhydride compound is adopted as the additive A in the electrolyte and the lithium aluminum titanium phosphate solid electrolyte LATP is added in the positive electrode plate, the LATP can catalyze the phosphoric anhydride compound to form a film at the positive electrode, so that the migration rate of lithium ions at low temperature is improved, the increase of interface impedance in the circulation process is reduced, and the low-temperature rate discharge performance and the low-temperature long-cycle performance of the battery are synergistically improved.
The comparison of the data in examples 1-4 shows that the content of the phosphoric anhydride compound additive A in the electrolyte is between 0.3% and 1.2%, and meets the requirements ofWhen the battery is in use, the battery has good low-temperature rate discharge performance and low-temperature long-cycle performance; further, as the content of the phosphoric anhydride compound additive in the electrolyte increases, the low-temperature cycle capacity retention rate of the battery also deteriorates, and the effect of improving the battery performance is better when the content of the phosphoric anhydride compound additive in the electrolyte is less than or equal to 1.2%.
Further in combination with examples 16 to 17, when the content of the phosphoric anhydride compound in the electrolyte is further increased and the formula value exceeds the range value, the negative electrode resistance is seriously deteriorated, thereby simultaneously deteriorating the low-temperature rate discharge performance and the low-temperature long-cycle performance of the battery.
The data of example 1 and example 5 show that the content of the LATP of the positive electrode material is between 0.5 and 1 percent and meets the requirements ofWhen the battery is in use, the battery has good low-temperature rate discharge performance and low-temperature long-cycle performance; the further increase of the LATP content in the positive electrode sheet can lead to a corresponding decrease of the content of the positive electrode active material in the positive electrode slurry, which is unfavorable for the battery to maintain a better energy density, and may not even meet the energy density requirement of the battery.
From the data of examples 1, 6-7 and 11-15, it is shown that the electrolyte injection coefficient of the electrolyte is between 1.5 and 1.8g/Ah and meets the following requirementsWhen the battery is in use, the battery has good low-temperature rate discharge performance and low-temperature long-cycle performance; when it is lower than the range value, for example, example 6, and the formula value is lower than the range value, the low-temperature rate discharge performance and the low-temperature long-cycle performance of the battery are deteriorated.
The data in examples 1 and 8 to 10 show that the particle size of the positive electrode material LATP satisfies the conditions that the D50 is 0.2 to 0.5. Mu.mWhen the battery is in use, the battery has good low-temperature rate discharge performance and low-temperature long-cycle performance; when the particle diameter is higher than the range value, for example, example 10, and the formula value is lower than the range value, the low-temperature rate discharge performance and the low-temperature long-cycle performance of the battery are deteriorated.
The data of examples 18 and 19 show that the phosphoric anhydride with the structural formula disclosed by the application is matched with LATP in the positive electrode plate, and has consistent effect of improving low-temperature rate discharge or low-temperature long-cycle performance of the battery.
Further, an electrolyte, a positive electrode sheet, a negative electrode sheet and a lithium ion battery were prepared in the same manner as in example 15 except for the kinds and contents of the solvent, lithium salt and additive B in the electrolyte, specifically as shown in table 2.
TABLE 2
Remarks: liBF 4 represents lithium tetrafluoroborate and DEC represents diethyl carbonate.
The data of examples 15 and examples 20 to 21 show that the lithium salt in the electrolyte is a combination of lithium hexafluorophosphate and lithium difluorosulfimide, and the improvement effect on the low temperature performance of the battery is better.
The data of examples 15 and 22-23 show that the electrolyte adopts a combination of propylene carbonate and ethyl propionate as the solvent, and the mass percent of the ethyl propionate is in the range of 50-65%, so that the low-temperature performance of the battery is improved better.
The data of examples 15 and 24-25 show that the nitrile compound, the carbonate compound and the sulfate compound are added to serve as basic additives on the basis of the electrolyte containing the additive A phosphoric anhydride compound, and the synergistic effect among the components is utilized to facilitate the formation of an interface film with high stability and good compactness on the positive and negative electrode plates, so that the positive and negative electrode plates are protected, and the improvement effect on the low-temperature performance of the battery is better.
It should be noted that the above-described embodiments are only for explaining the present application and do not constitute any limitation of the present application. The application has been described with reference to exemplary embodiments, but it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Modifications may be made to the application as defined in the appended claims, and the application may be modified without departing from the scope and spirit of the application. Although the application is described herein with reference to particular means, materials and embodiments, the application is not intended to be limited to the particulars disclosed herein, as the application extends to all other means and applications having the same function.

Claims (8)

1. The lithium ion battery comprises a positive electrode plate, a negative electrode plate, a diaphragm and electrolyte, and is characterized in that the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer coated on the surface of the positive electrode current collector, and the positive electrode material layer comprises lithium aluminum titanium phosphate;
The electrolyte comprises an additive A, wherein the chemical structural formula of the additive A is shown as formula I:
；
Wherein each R 1、R2、R3 is independently selected from hydrocarbyl groups having no more than 4 carbon atoms substituted or unsubstituted with fluorine;
the positive plate and the electrolyte satisfy the following conditions:
；
wherein, c (%) represents the mass percent of the additive A in the electrolyte, and c is more than or equal to 0.3 and less than or equal to 1.2;
l (%) represents the mass percent of lithium aluminum titanium phosphate in the positive electrode material layer, wherein L is more than or equal to 0.5 and less than or equal to 1.0;
f (g/Ah) represents the injection coefficient of the electrolyte in the lithium ion battery, and f is more than or equal to 1.5 and less than or equal to 1.8;
d (mum) represents the D50 particle size of the lithium aluminum titanium phosphate in the positive electrode material layer, and D is more than or equal to 0.2 and less than or equal to 0.5.
2. The lithium ion battery of claim 1, wherein the additive a is selected from at least one of the following compounds: n-methylphosphonic anhydride, n-ethylphosphoric anhydride, n-propylphosphoric anhydride, n-butylphosphoric anhydride, pentafluoroethyl phosphoric anhydride.
3. The lithium ion battery according to claim 1 or 2, wherein the electrolyte further comprises a lithium salt selected from at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium difluorooxalato borate, lithium bisoxalato borate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethyl imide, lithium difluorooxalato phosphate, lithium perchlorate;
the mass percentage of the lithium salt in the electrolyte is 8-15%.
4. A lithium ion battery according to claim 3, wherein the lithium salt comprises lithium hexafluorophosphate and lithium bis-fluorosulfonyl imide, and wherein the mass percentage of lithium bis-fluorosulfonyl imide in the electrolyte is 2-6%.
5. The lithium ion battery according to claim 1 or 2, wherein the electrolyte further comprises an organic solvent selected from at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl difluoroacetate;
the mass percentage of the organic solvent in the electrolyte is 73-85.2%.
6. The lithium ion battery according to claim 5, wherein the organic solvent at least comprises propylene carbonate and ethyl propionate, and the mass percentage of ethyl propionate in the electrolyte is 50% -65%.
7. The lithium ion battery of claim 1, wherein the electrolyte further comprises an additive B comprising at least one of a nitrile compound, a carbonate compound, and a sulfate compound.
8. The lithium ion battery of claim 7, wherein the nitrile compound is selected from at least one of adiponitrile, succinonitrile, 1,3, 6-hexane-trimethylnitrile, trans-hexenedinitrile, fumaric dinitrile, 1, 2-bis (cyanoethoxy) ethane and 1,2, 3-tris (cyanoethoxy) propane; the mass percentage of the nitrile compound in the electrolyte is 2% -4%;
And/or the carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate and bis-fluoroethylene carbonate; the mass percentage of the carbonate compound in the electrolyte is 4-6%;
And/or the sulfate compound is selected from at least one of vinyl sulfate, vinyl sulfite, vinyl 4-methyl sulfate, dimethyl sulfite and diethyl sulfite; the mass percentage content of the sulfate compound in the electrolyte is 0.5% -1%.
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