Lithium ion battery electrolyte, lithium ion battery, battery module, battery pack, electric device of high-voltage lithium cobalt oxide / silicon carbon system

Abstract

The present application relates to the technical field of battery, in particular to a high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte, a lithium ion battery, a battery module, a battery pack, and a power utilization device. The high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte comprises a non-aqueous organic solvent, a lithium salt, and a functional additive, wherein the functional additive comprises a lithium salt additive, a first additive, a second additive, and a third additive; the first additive is selected from unsaturated sulfonate additives; the second additive is selected from unsaturated disiloxane additives; and the third additive is selected from fluorinated carbonate additives. The components of the electrolyte synergize with each other, can form a stable and dense solid-state electrolyte interface on the positive and negative electrode surfaces, effectively inhibit the side reactions of the electrolyte on the electrode surface, inhibit the expansion of the silicon-carbon negative electrode and the dissolution of the positive transition metal, improve the stability of the interface during the cycle process, and effectively improve the cycle performance of the lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a lithium ion battery electrolyte of high-voltage lithium cobaltate / silicon-carbon system, a lithium ion battery, a battery module, a battery pack and a power utilization device. BACKGROUND

[0002] Lithium ion battery technology is changing rapidly, and its application range is gradually expanding. As an energy storage device, it is applied in portable electronic products, large-scale energy storage and electric vehicles. Research and development of lithium ion batteries with higher energy density have always been an important direction of the industry and the main demand of the current lithium ion industry. At present, in order to obtain lithium ion batteries with high energy density, the main method is to select high-capacity and high-compaction positive and negative active materials and to increase the charge cut-off voltage of the positive active material.

[0003] On the positive electrode side, increasing the charge cut-off voltage of the positive electrode material is an effective means to improve the energy density. For example, the voltage of commercial lithium cobaltate batteries is 4.2V→4.35V→4.4V→4.45V→4.48V→4.5V. However, increasing the charge cut-off voltage of the positive electrode material (≥4.5V) also has some problems: for example, the commonly used carbonate-based electrolyte is easily oxidized and decomposed at high voltage, and nitrile-based additives are widely used as an efficient positive electrode protection additive. For example, CN104505535A and CN104600359A use organic nitrile-based additives to improve high-temperature performance. However, in actual application, due to the high reduction potential of nitrile-based additives, they are easily consumed by the negative electrode during formation, thereby weakening the protection effect of nitrile-based additives on the positive electrode, and the nitrile-based additives consumed by the negative electrode during formation do not form a stable solid electrolyte interface film (SEI) to protect the negative electrode, but instead worsen the impedance of the negative electrode, thereby increasing the polarization of the lithium ion battery, and thus causing the capacity retention rate of the lithium ion battery to decay too quickly in a high-voltage environment.

[0004] On the negative electrode side, the existing lithium ion battery is mainly based on graphite, and its theoretical capacity is only 372 mAhg -1 , which is an important factor restricting the energy density of lithium ion batteries; the theoretical capacity of pure silicon-based negative electrode is as high as 4200 mAhg -1However, as a negative electrode of lithium ion battery, the battery expands and pulverizes seriously due to the volume effect, and the cycle performance is poor. Therefore, people consider to composite silicon-carbon material to form silicon-carbon negative electrode material, which can greatly improve the specific capacity of the material and to a certain extent reduce the volume effect of silicon-based materials. At present, the electrolyte of lithium ion battery with silicon-carbon negative electrode usually uses a large amount of fluoroethylene carbonate (FEC) as an additive of the electrolyte. Fluoroethylene carbonate can be reduced at a relatively low reduction potential, so that a solid electrolyte interface (SEI) film with small resistance and high density is formed on the surface of the negative electrode, thereby improving the cycle stability of the lithium ion battery at room temperature and high temperature. However, in a high temperature environment, lithium hexafluorophosphate is prone to decomposition to generate Lewis acid, which further accelerates the decomposition of fluoroethylene carbonate to generate hydrofluoric acid, forming a vicious cycle and affecting the cycle stability of the lithium ion battery.

[0005] There is an urgent need to develop a lithium ion battery electrolyte for high-voltage lithium cobaltate / silicon-carbon system, which includes specific combination of additives, can effectively form a film on the surface of the positive and negative electrodes while improving the high-temperature stability of fluoroethylene carbonate without using nitrile additives, inhibit the side reactions of the electrolyte on the electrode surface, inhibit the expansion of the silicon-carbon negative electrode and the dissolution of the transition metal of the positive electrode, improve the stability of the interface during the cycle process, and thus effectively improve the cycle performance of the lithium ion battery. SUMMARY

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present application is to provide a lithium ion battery electrolyte for high-voltage lithium cobaltate / silicon-carbon system, lithium ion battery, battery module, battery pack, and power utilization device. By adding lithium salt additive, first additive, second additive and third additive, the electrolyte components synergize with each other to form a stable and dense solid electrolyte interface on the surface of the positive and negative electrodes, effectively inhibit the side reactions of the electrolyte on the electrode surface, inhibit the expansion of the silicon-carbon negative electrode and the dissolution of the transition metal of the positive electrode, improve the stability of the interface during the cycle process, and thus effectively improve the cycle performance of the lithium ion battery.

[0007] The technical solution of the present application is as follows:

[0008] The first aspect of the present application provides a lithium ion battery electrolyte for high-voltage lithium cobaltate / silicon-carbon system, which includes non-aqueous organic solvent, lithium salt and functional additive, the functional additive includes lithium salt additive, first additive, second additive and third additive, the first additive is selected from unsaturated sulfonate additive, the second additive is selected from unsaturated disiloxane additive, and the third additive is selected from fluoro carbonate additive.

[0009] The second aspect of the present application provides a high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery, comprising a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and a high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte, wherein the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte is the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte described in the present application.

[0010] The third aspect of the present application provides a battery module comprising the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery described in the second aspect of the present application.

[0011] The fourth aspect of the present application provides a battery pack comprising the battery module described in the third aspect of the present application.

[0012] The fifth aspect of the present application provides an electric device comprising the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery described in the second aspect of the present application, wherein the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery is used as a power source for the electric device. The electric device includes mobile devices, electric vehicles, electric trains, satellites, ships, and energy storage systems.

[0013] By adopting the foregoing technical solutions, the present application has the following beneficial effects:

[0014] (1) The unsaturated sulfonate additive has a low LUMO energy level, can preferentially form a stable dense and low-impedance solid electrolyte interface rich in sulfonate compounds on the surface of the negative electrode, can effectively inhibit the side reactions of the electrolyte, is conducive to the transmission of lithium ions, and improves the cycle performance;

[0015] (2) The unsaturated disiloxane additive has the effect of removing acid and water, can effectively inhibit the hydrolysis of lithium hexafluorophosphate and the decomposition of fluoroethylene carbonate at high temperatures, and reduce the content of water and hydrofluoric acid in the electrolyte. In addition, the unsaturated disiloxane additive provided by the present application can undergo electrochemical polymerization on the surface of the positive electrode to form a stable solid-state electrolyte interface, effectively inhibit the dissolution of transition metals from the positive electrode, and improve the cycle performance;

[0016] (3) The lithium salt additive, such as lithium difluoro(oxalato)borate, has excellent high and low temperature performance and thermal stability, can preferentially reduce to form a stable and low-impedance solid-state electrolyte interface on the negative electrode, and lithium difluorophosphate can generate a dense and thin solid electrolyte interface film rich in phosphate, and the decomposition of lithium difluorophosphate generates monofluorophosphate PO3F 2- and phosphate PO4 3- , which can inhibit the hydrolysis of LiPF6, effectively capture and remove transition metals to inhibit electrode crosstalk, reduce impedance, and improve cycle performance, etc.;

[0017] (4) The fluoro-carbonate additive, such as fluoroethylene carbonate, can stably form a film on the negative electrode and inhibit the volume expansion of the silicon-carbon negative electrode.

[0018] The functional additives described in the present application are used together, and can produce unexpected synergistic effects, can form a stable and dense solid-state electrolyte interface on the surface of the positive and negative electrodes, effectively inhibit the side reactions of the electrolyte on the electrode surface, inhibit the expansion of the silicon-carbon negative electrode and the dissolution of the transition metal of the positive electrode, improve the stability of the interface during the cycle process, and effectively improve the cycle performance of the lithium ion battery. Effectively solve the problem of the degradation effect of nitrile additives on the negative electrode and the cycle performance decay caused by the high temperature decomposition of fluoroethylene carbonate.

[0019] The battery module, battery pack and power utilization device of the present application include the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery described in the present application, and thus at least have the same advantages as the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery. DETAILED DESCRIPTION

[0020] Hereinafter, embodiments of the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte, lithium ion battery, battery module, battery pack, and power utilization device provided by the present application will be described in detail.

[0021] The ranges disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges of 60~120 and 80~110 are listed for a particular parameter, it is understood that the ranges of 60~110 and 80~120 are also contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4 and 5 are listed, the following ranges are all contemplated: 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5. In the present application, unless otherwise stated, the numerical range "a~b" represents a shorthand notation for any real combination of integers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between "0~5" have been listed herein, and "0~5" is only a shorthand notation for these numerical combinations. In addition, when a parameter is stated to be ≥2 integers, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0022] The inventors of the present application provide, through a large number of exploratory researches, a high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte, functional additives are used together, unexpected synergistic effects can be produced, a stable and dense solid-state electrolyte interface can be formed on the positive and negative electrode surfaces, the side reactions of electrolyte on the electrode surface can be effectively inhibited, the silicon-carbon negative electrode expansion and the positive transition metal dissolution can be inhibited, the interface stability in the cycle process is improved, and the cycle performance of the lithium ion battery is effectively improved. The problems of the negative electrode deterioration effect of the nitrile additive and the cycle performance decay caused by the high-temperature decomposition of the fluoroethylene carbonate are effectively solved. On this basis, the present application is completed.

[0023] High-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte

[0024] The present application provides a high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte, comprising a non-aqueous organic solvent, a lithium salt and a functional additive, the functional additive comprises a lithium salt additive, a first additive, a second additive and a third additive, the first additive is selected from unsaturated sulfonate additives, the second additive is selected from unsaturated disiloxane additives, and the third additive is selected from fluoro carbonate additives.

[0025] In the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte provided by the present application, the lithium salt additive is selected from a combination of any two of lithium trifluoromethyl sulfonate, lithium fluorosulfonate, lithium tetrafluoro oxalate phosphate, lithium difluoro oxalate phosphate, lithium difluoro oxalate borate and lithium difluorophosphate. Preferably, the lithium salt additive is selected from a combination of any two of lithium fluorosulfonate, lithium tetrafluoro oxalate phosphate, lithium difluoro oxalate borate and lithium difluorophosphate. More preferably, the lithium salt additive is selected from a combination of lithium difluoro oxalate borate and lithium difluorophosphate, for example, the mass ratio of lithium difluoro oxalate borate and lithium difluorophosphate is 1:1. The lithium salt additive of the present application is selected from lithium difluoro oxalate borate, which has excellent high and low temperature performance and thermal stability, can form a stable and low impedance solid-state electrolyte interface at the negative electrode, lithium difluorophosphate can generate a dense and thin solid electrolyte interface film rich in phosphate, and can generate monofluorophosphate PO3F 2- and phosphate PO4 3- , can inhibit the hydrolysis of LiPF6, effectively capture and remove transition metals to inhibit electrode crosstalk, reduce impedance, and improve cycle performance.

[0026] In the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte provided by the application, in the first additive, the unsaturated sulfonate additive is selected from a combination of any two of 1,3-propane sulfonic lactone, 1,3-propylene sulfonic lactone, 3-fluoro-1,3-propane sulfonic lactone, propargyl triflate, allyl triflate, propargyl methane sulfonate and allyl methane sulfonate. Preferably, the unsaturated sulfonate additive is selected from a combination of any two of 1,3-propane sulfonic lactone, 3-fluoro-1,3-propane sulfonic lactone, allyl methane sulfonate and propargyl methane sulfonate. More preferably, the unsaturated sulfonate additive is selected from a combination of 1,3-propane sulfonic lactone and propargyl methane sulfonate, for example, the mass ratio of 1,3-propane sulfonic lactone to propargyl methane sulfonate is (1-2):(2-1). The unsaturated sulfonate additive of the application has a low LUMO energy level, can preferentially form a stable dense and low impedance solid electrolyte interface rich in sulfonate compounds on the negative electrode surface, can effectively inhibit the side reaction of the electrolyte, is conducive to the transmission of lithium ions and improves the cycle performance.

[0027] In the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte provided by the application, in the second additive, the unsaturated disiloxane additive is selected from any one of 1,3-bis(3-fluoro-1-propargyl)-1,1,3,3-tetramethyl disiloxane, 1,3-bis(3-methoxy-1-propargyl)-1,1,3,3-tetramethyl disiloxane, 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyl disiloxane and 1,3-bis(2-ethyl ether)-1,1,3,3-tetramethyl disiloxane. Preferably, the unsaturated disiloxane additive is selected from any one of 1,3-bis(3-fluoro-1-propargyl)-1,1,3,3-tetramethyl disiloxane and 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyl disiloxane. More preferably, the unsaturated disiloxane additive is 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyl disiloxane. The unsaturated disiloxane additive of the application has the effect of removing acid and water, can effectively inhibit the hydrolysis of lithium hexafluorophosphate and the decomposition of fluorinated ethylene carbonate at high temperature, and reduce the content of water and hydrogen fluoride in the electrolyte. Secondly, the unsaturated disiloxane additive provided by the application can form a stable solid electrolyte interface on the positive electrode surface through electrochemical polymerization, effectively inhibit the dissolution of transition metals in the positive electrode and improve the cycle performance.

[0028] The fluorocarbonate additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte provided by the present application is selected from any one of fluorinated ethylene carbonate or difluorinated ethylene carbonate. Preferably, the fluorocarbonate additive is selected from fluorinated ethylene carbonate. The fluorocarbonate additive of the present application, such as fluorinated ethylene carbonate, can stabilize the film formation at the negative electrode and inhibit the volume expansion of the silicon-carbon negative electrode.

[0029] The lithium salt additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte provided by the present application has a mass ratio of 0.5% to 2% in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte. In some embodiments, the mass ratio of the lithium salt additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte may, for example, be 0.5% to 1%, 1% to 2%, 1% to 1.5%, 1.5% to 2%, etc. Preferably, the mass ratio of the lithium salt additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is 1% to 2%. Within the above range, the lithium salt additive can form a stable and dense solid electrolyte interface, reduce impedance, and improve cycle performance. Too low a proportion of the lithium salt additive (a mass ratio of less than 1% in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte) does not significantly improve battery performance. Too high a proportion of the lithium salt additive (a mass ratio of more than 2% in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte) may increase battery impedance.

[0030] The first additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte provided by the present application has a mass ratio of 1% to 4% in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte. In some embodiments, the mass ratio of the first additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte may, for example, be 1% to 2%, 2% to 3%, 3% to 4%, 1% to 3%, 2% to 4%, etc. Preferably, the mass ratio of the first additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is 3% to 4%. Within the above range, the first additive has a low LUMO energy level, can preferentially form a stable and dense solid electrolyte interface rich in sulfonate compounds on the negative electrode surface, can effectively inhibit the side reactions of the electrolyte, is conducive to the transmission of lithium ions, and improves cycle performance. Too low a proportion of the first additive (a mass ratio of less than 3% in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte) results in poor film formation and does not significantly improve battery performance. Too high a proportion of the first additive (a mass ratio of more than 4% in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte) may increase the viscosity of the electrolyte, form a thicker film, increase the impedance of the battery cell, and deteriorate the performance of the battery cell.

[0031] In the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte provided by the present application, the mass ratio of the second additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is 0.5% to 1%. In some embodiments, the mass ratio of the second additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte may be, for example, 0.5% to 0.8%, 0.8% to 1.0%, etc. Preferably, the mass ratio of the second additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is 1%. Within the above range, the second additive has the effect of removing water and acid, can effectively inhibit the hydrolysis of lithium hexafluorophosphate and the decomposition of fluoroethylene carbonate at high temperature, and reduce the content of water and hydrofluoric acid in the electrolyte. Secondly, the second additive can occur on the positive electrode surface Electric polymerization forms a stable solid-state electrolyte interface, effectively inhibits the dissolution of transition metals in the positive electrode, and improves the cycle performance. The proportion of the second additive is too low (the mass ratio of the second additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is less than 0.5%), which has no obvious effect on the improvement of battery performance. The proportion of the second additive is too high (the mass ratio of the second additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is greater than 1%), which may cause the viscosity of the electrolyte to increase, increase the impedance of the battery cell, and deteriorate the performance of the battery cell.

[0032] In the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte provided by the present application, the mass ratio of the third additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is 3% to 8%. In some embodiments, the mass ratio of the third additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte may be, for example, 3% to 6%, 6% to 8%, 3% to 4%, 4% to 6%, 4% to 5%, 5% to 6%, or 6% to 8%, etc. Preferably, the mass ratio of the third additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is 5% to 6%. Within the above range, the third additive can form a stable film on the negative electrode and inhibit the volume expansion of the silicon-carbon negative electrode. The proportion of the third additive is too low (the mass ratio of the third additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is less than 5%), which cannot effectively inhibit the volume expansion of the silicon-carbon negative electrode. The proportion of the third additive is too high (the mass ratio of the third additive in the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte is greater than 6%), which is easy to decompose and produce hydrofluoric acid at high temperature, and deteriorate the performance of the battery cell.

[0033] In the high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte provided by the present application, the lithium salt is selected from one or more combinations of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium aluminum chloride, lithium bis(oxalato)borate, lithium chloride, lithium bromide, lithium iodide, and lithium bis(trifluoromethylsulfonate)imide.

[0034] The content of the lithium salt in the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte provided by the present application is 1 mol / L-1.5 mol / L. In some embodiments, the content of the lithium salt in the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte can also be 1 mol / L-1.1 mol / L, 1.1 mol / L-1.2 mol / L, 1.2 mol / L-1.3 mol / L, 1.3 mol / L-1.4 mol / L, or 1.4 mol / L-1.5 mol / L, etc. Within the above range, high lithium ion conductivity and stable lithium ion transmission can be ensured. Too high a proportion of the lithium salt (content in the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte is higher than 1.5 mol / L) will lead to incomplete dissociation of the lithium salt, too large viscosity of the electrolyte, hinder transmission of lithium ions, and reduce rate capability and low-temperature performance. Too low a proportion of the lithium salt (content in the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte is lower than 1 mol / L) will lead to poor electrochemical stability of the electrolyte.

[0035] The non-aqueous organic solvent in the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte provided by the present application is selected from a combination of one or more of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propyl propionate, ethyl n-butyrate, and methyl trifluoroethyl carbonate. Preferably, the non-aqueous organic solvent is selected from a combination of vinyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP).

[0036] The mass proportion of the non-aqueous organic solvent in the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte provided by the present application is 65%-84%. In some embodiments, the mass proportion of the non-aqueous organic solvent in the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte can also be 65%-75%, 75%-84%, etc. Within the above range, the lithium salt and the additive can be better dissolved. Too high a proportion of the non-aqueous organic solvent (mass proportion in the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte is higher than 84%) will lead to poor electrochemical stability of the electrolyte. Too low a proportion of the non-aqueous organic solvent (mass proportion in the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte is lower than 65%) will lead to incomplete dissociation of the lithium salt and too large viscosity of the electrolyte.

[0037]

High-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery

[0038] The second aspect of the present application provides a high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery, which further comprises a positive electrode, a negative electrode, a separator, and a high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte selected from the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte of the first aspect of the present application.

[0039] The positive electrode comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The positive electrode active material layer comprises a positive electrode active material, and can further comprise a conductive agent and a binder. The positive electrode active material used in the present experiment is selected from lithium cobalt oxide. Those skilled in the art can select a conductive agent and a binder suitable for lithium ion batteries in the art. The conductive agent can include, for example, at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder can include, for example, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0040] In some embodiments, the positive electrode can be prepared by dispersing the above-mentioned components for preparing the positive electrode, such as the positive electrode material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and then drying, cold pressing, and the like to obtain the positive electrode.

[0041] The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The negative electrode active material layer includes a negative electrode active material, and can further include a plasticizer, a conductive agent, and a binder. The negative electrode active material can be selected from silicon-carbon. A person skilled in the art can select a plasticizer, a conductive agent, and a binder suitable for a lithium ion battery in the art. The conductive agent can be, for example, selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder can be, for example, selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS), sodium carboxymethyl cellulose (CMC-Na).

[0042] In some embodiments, the negative electrode can be prepared by dispersing the components for preparing the negative electrode, such as the negative electrode material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector; and drying, cold pressing, or the like to obtain the negative electrode.

[0043] The high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery provided in the second aspect of the present application can be prepared by a method known in the art. For example, the positive electrode, the separator, and the negative electrode are stacked in order with the separator between the positive electrode and the negative electrode to play a role of separation, and then the stack is obtained to obtain a bare battery cell; the bare battery cell is placed in an outer packaging shell, and after drying, a high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte is injected, and then the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery is obtained through processes such as vacuum packaging, standing, formation, shaping, and the like.

[0044]

Battery module

[0045] The third aspect of the present application provides a battery module, which includes any one or more of the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion batteries described in the second aspect of the present application. The number of high-voltage lithium cobalt oxide / silicon-carbon system lithium ion batteries in the battery module can be adjusted according to the application and capacity of the battery module.

[0046]

Battery pack

[0047] The fourth aspect of the present application provides a battery pack comprising any one or more of the battery modules according to the third aspect of the present application. That is, the battery pack comprises any one or more of the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion batteries according to the second aspect of the present application.

[0048] The number of battery modules in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0049]

Power consuming device

[0050] The fifth aspect of the present application provides a power consuming device comprising any one or more of the high-voltage lithium cobalt oxide / silicon-carbon system lithium ion batteries according to the second aspect of the present application. The high-voltage lithium cobalt oxide / silicon-carbon system lithium ion batteries can be used as the power source of the power consuming device. Preferably, the power consuming device can be, but is not limited to, a mobile device (e.g. a mobile phone, a laptop, etc.), an electric vehicle (e.g. a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0051] The beneficial effects of the present application are further illustrated in the following examples.

[0052] In order to make the inventive objectives, technical solutions and beneficial technical effects of the present application clearer, the present application will be further described in detail in the following with reference to the examples. However, it should be understood that the examples of the present application are only for the purpose of explaining the present application, and are not intended to limit the present application, and the examples of the present application are not limited to the examples given in the specification. The specific experimental conditions or operation conditions not mentioned in the examples are made according to the conventional conditions, or made according to the conditions recommended by the material suppliers.

[0053] In addition, it should be understood that the one or more method steps mentioned in the present application do not exclude that there can be other method steps before and after the combination steps or other method steps can be inserted between the explicitly mentioned steps, unless otherwise stated; it should also be understood that the combination connection relationship between the one or more devices / apparatuses mentioned in the present application does not exclude that there can be other devices / apparatuses before and after the combination devices / apparatuses or other devices / apparatuses can be inserted between the two explicitly mentioned devices / apparatuses, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the arrangement order of each method step or to limit the range of implementation of the present application, and the change or adjustment of the relative relationship, without substantial change of the technical content, is also regarded as the scope of implementation of the present application.

[0054] In the following examples, unless specifically stated, the various raw materials of the present application can be commercially available or prepared according to the conventional methods in the art.

[0055] Example 1

[0056] Preparation of electrolyte:

[0057] The electrolyte was prepared in a glove box (moisture content <0.1 ppm, oxygen content <0.1 ppm). Vinyl carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC) and propyl propionate (PP) were mixed in a volume ratio of 10:10:30:50 as an organic solvent, and 100 mL was prepared. LiPF6 with a molar concentration of 1.1 mol / L was added to the solvent, and 6% FEC, 2% PS, 2% PMS, 1% TMSDSiO, 1% LiDFP and 1% LiODFB were added to the above electrolyte, respectively, with a mass of 6% of lithium ion battery electrolyte, and stirred until completely dissolved to obtain the lithium ion battery electrolyte of Example 1.

[0058] Example 2

[0059] Preparation of electrolyte:

[0060] Different from Example 1, 5% FEC, 2% PS, 2% PMS, 1% TMSDSiO, 1% LiDFP and 1% LiODFB were added to the above electrolyte, respectively, with a mass of 5% of lithium ion battery electrolyte, and stirred until completely dissolved to obtain the lithium ion battery electrolyte of Example 2.

[0061] Example 3

[0062] Preparation of electrolyte:

[0063] Different from Example 1, 5% FEC, 2% PS, 2% PMS, 1% TMSDSiO, 0.5% LiDFP and 0.5% LiODFB were added to the above electrolyte, respectively, with a mass of 5% of lithium ion battery electrolyte, and stirred until completely dissolved to obtain the lithium ion battery electrolyte of Example 3.

[0064] Example 4

[0065] Preparation of electrolyte:

[0066] Different from Example 1, 5% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO), 1% of lithium difluorophosphate (LiDFP) and 1% of lithium difluoro(oxalato)borate (LiODFB) by mass of lithium ion battery electrolyte were added into the above electrolyte, stirred until completely dissolved, to obtain the lithium ion battery electrolyte of Example 4.

[0067] Example 5

[0068] Preparation of electrolyte:

[0069] Different from Example 1, 5% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) by mass of lithium ion battery electrolyte were added into the above electrolyte, stirred until completely dissolved, to obtain the lithium ion battery electrolyte of Example 5.

[0070] Comparative Example 1

[0071] Preparation of electrolyte:

[0072] The electrolyte was configured in a glove box (moisture content in the configuration environment was less than 0.1 ppm, oxygen content was less than 0.1 ppm), and ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC) and propyl propionate (PP) were mixed in a volume ratio of 10:10:30:50 as an organic solvent, a total of 100 mL. LiPF6 with a molar concentration of 1.1 mol / L of lithium salt was added to the solvent, 5% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) by mass of lithium ion battery electrolyte were added into the above electrolyte, stirred until completely dissolved, to obtain the lithium ion battery electrolyte of Comparative Example 1.

[0073] Comparative Example 2

[0074] Preparation of electrolyte:

[0075] The lithium ion battery electrolyte of Comparative Example 2 was prepared by adding 5% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) in the above electrolyte respectively, and stirring until completely dissolved, except that Comparative Example 1 was not added.

[0076] Comparative Example 3

[0077] Preparation of electrolyte:

[0078] The lithium ion battery electrolyte of Comparative Example 3 was prepared by adding 5% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) in the above electrolyte respectively, and stirring until completely dissolved, except that Comparative Example 1 was not added.

[0079] Comparative Example 4

[0080] Preparation of electrolyte:

[0081] The lithium ion battery electrolyte of Comparative Example 4 was prepared by adding 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) in the above electrolyte respectively, and stirring until completely dissolved, except that Comparative Example 1 was not added.

[0082] Comparative Example 5

[0083] Preparation of electrolyte:

[0084] The lithium ion battery electrolyte of Comparative Example 5 was prepared by adding 5% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS) and 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO) in the above electrolyte respectively, and stirring until completely dissolved, except that Comparative Example 1 was not added.

[0085] Comparative Example 6

[0086] Preparation of electrolyte:

[0087] The lithium ion battery electrolyte of Comparative Example 6 was prepared by adding 5% of fluoroethylene carbonate (FEC), 1% of 1,3-bis(3-trimethylsilyl-1- propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) in the above electrolyte respectively, and stirring until completely dissolved.

[0088] Comparative Example 7

[0089] Preparation of electrolyte:

[0090] The lithium ion battery electrolyte of Comparative Example 7 was prepared by adding 10% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3- tetramethyldisiloxane (TMSDSiO), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) in the above electrolyte respectively, and stirring until completely dissolved.

[0091] Comparative Example 8

[0092] Preparation of electrolyte:

[0093] The lithium ion battery electrolyte of Comparative Example 8 was prepared by adding 2% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3- tetramethyldisiloxane (TMSDSiO), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) in the above electrolyte respectively, and stirring until completely dissolved.

[0094] Comparative Example 9

[0095] Preparation of electrolyte:

[0096] The lithium ion battery electrolyte of Comparative Example 9 was prepared by adding 5% of fluoroethylene carbonate (FEC), 3% of 1,3-propane sultone (PS), 3% of propargyl methanesulfonate (PMS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) in the above electrolyte by mass, and stirring until completely dissolved.

[0097] Comparative Example 10

[0098] Preparation of electrolyte:

[0099] The lithium ion battery electrolyte of Comparative Example 10 was prepared by adding 5% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO), 2% of lithium difluorophosphate (LiDFP) and 2% of lithium difluoro(oxalato)borate (LiODFB) in the above electrolyte by mass, and stirring until completely dissolved.

[0100] Comparative Example 11

[0101] Preparation of electrolyte:

[0102] The lithium ion battery electrolyte of Comparative Example 11 was prepared by adding 5% of fluoroethylene carbonate (FEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 2% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) in the above electrolyte by mass, and stirring until completely dissolved.

[0103] Comparative Example 12

[0104] Preparation of electrolyte:

[0105] Different from Comparative Example 1, 3% of fluoroethylene carbonate (FEC), 3% of difluoroethylene carbonate (DFEC), 1% of 1,3-propane sultone (PS), 2% of propargyl methanesulfonate (PMS), 1% of 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane (TMSDSiO), 0.5% of lithium difluorophosphate (LiDFP) and 0.5% of lithium difluoro(oxalato)borate (LiODFB) were added into the above electrolyte respectively, stirred until completely dissolved, to obtain the lithium ion battery electrolyte of Comparative Example 12.

[0106] The electrolyte formulations of each of the examples and comparative examples are shown in Table 1 below:

[0107] Table 1. Electrolyte formulations of each of the examples and comparative examples of the high-voltage lithium cobaltate / silicon-carbon system

[0108]

[0109] Preparation of 1 Ah soft-pack lithium ion battery of high-voltage lithium cobaltate / silicon-carbon system: The prepared positive electrode sheet, separator and negative electrode sheet were stacked in order, with the separator between the positive and negative electrodes to serve as a separator, and then the stack was obtained to obtain a bare battery cell; the bare battery cell was placed in an aluminum plastic film, dried to obtain a battery cell to be injected with liquid, and the electrolytes of the examples and comparative examples were injected into the battery cell to be injected with liquid, and after processes such as standing, formation and capacity distribution, the lithium ion battery of the high-voltage lithium cobaltate / silicon-carbon system was obtained.

[0110] The lithium ion battery positive electrode material used in this experiment was lithium cobaltate with a maximum charging voltage of 4.5 V, and the negative electrode was silicon-carbon. The batteries obtained from Examples 1-5 and Comparative Examples 1-12 were subjected to cycle tests, and the test results are shown in Table 2.

[0111] 25℃ cycle performance test: the batteries obtained from Examples 1-5 and Comparative Examples 1-12 were subjected to 25℃ cycle performance test, with 1C constant current and constant voltage charging to 4.5V, 0.05C cutoff current, 10min standing, 1C constant current discharging to 3V, and the above was one charge-discharge cycle. The obtained battery was subjected to cycle charging and discharging at 25℃, and the cycle was ended when the discharge capacity was lower than 80% of the initial discharge capacity.

[0112] 45℃ cycle performance test: the batteries obtained from Examples 1-5 and Comparative Examples 1-12 were subjected to 45℃ cycle performance test, with 1C constant current and constant voltage charging to 4.5V, 0.05C cutoff current, 10min standing, 1C constant current discharging to 3V, and the above was one charge-discharge cycle. The obtained battery was subjected to cycle charging and discharging at 45℃, and the cycle was ended when the discharge capacity was lower than 80% of the initial discharge capacity.

[0113] The high-voltage lithium cobaltate / silicon-carbon system lithium ion battery electrolyte applied in the present application can achieve an ideal level for the remaining performance of the battery cell such as storage performance, rate performance, etc., and therefore detailed description is not given here.

[0114] Table 2 Cycle number of each embodiment and comparative example of high-voltage lithium cobaltate / silicon-carbon system

[0115]

[0116] As can be seen from Table 1 and Table 2, the cycle number of 80% capacity retention at 25°C of the battery cell in Examples 1-5 in which lithium salt additive, first additive (unsaturated sulfonate additive), second additive (unsaturated disiloxane additive) and third additive (fluorinated carbonate additive) are added at the same time is more than 750 times, and the cycle number of 80% capacity retention at 45°C is more than 400 times. In Example 5, the cycle number of 80% capacity retention at 25°C is more than 900 times, and the cycle number of 80% capacity retention at 45°C is more than 500 times. After the lithium salt additive, first additive, second additive and third additive are combined in a specific ratio, the performance of the battery cell is unexpectedly improved.

[0117] As can be seen from Comparative Examples 1-5 and Comparative Examples 1-6, when the lithium salt additive, first additive, second additive and third additive are used together and combined in a specific ratio within a certain range, the performance of the battery cell is unexpectedly improved. However, in Comparative Examples 1-6, the absence of one type of additive or the combination of the lithium salt additive and first additive in a specific ratio will cause the cycle number of 80% capacity retention at 25°C and the cycle number of 80% capacity retention at 45°C to be significantly worse than that of Examples 1-5.

[0118] As can be seen from Comparative Example 5 and Comparative Examples 7-11, when the amount of one type of additive in the lithium salt additive, first additive, second additive and third additive exceeds the range of the additive applied in the present application, the cycle performance of the battery cell will deteriorate.

[0119] As can be seen from Comparative Example 5 and Comparative Example 12, the cycle performance of the battery cell when fluorinated ethylene carbonate and difluorinated ethylene carbonate are used together is worse than that when fluorinated ethylene carbonate is used alone.

[0120] In summary, the present application effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0121] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form or in essence. It should be noted that those skilled in the art can make some improvements and supplements without departing from the method of the present application, and these improvements and supplements should also be considered as the protection scope of the present application. For those skilled in the art, some slight changes, modifications and equivalent changes made by using the disclosed technical content without departing from the spirit and scope of the present application are equivalent embodiments of the present application; meanwhile, any equivalent changes, modifications and evolution made according to the essential technology of the present application to the above embodiments are still within the scope of the technical solutions of the present application.

Claims

1. A high-voltage lithium cobalt oxide / silicon carbon system lithium ion battery electrolyte, characterized in that, The lithium ion battery electrolyte of the high-voltage lithium cobaltate / silicon-carbon system comprises a non-aqueous organic solvent, a lithium salt, and a functional additive, wherein the functional additive comprises a lithium salt additive, a first additive, a second additive, and a third additive; the first additive is selected from a combination of 1,3-propane sulfite and propargyl methanesulfonate; the second additive is selected from any one of 1,3-bis(3-fluoro-1-propargyl)-1,1,3,3-tetramethyldisiloxane, 1,3-bis(3-methoxy-1-propargyl)-1,1,3,3-tetramethyldisiloxane, 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane, and 1,3-bis(2-ethyl ether)-1,1,3,3-tetramethyldisiloxane; the third additive is selected from any one of fluoroethylene carbonate or difluoroethylene carbonate; the lithium salt additive is selected from a combination of any two of lithium trifluoromethyl sulfonate, lithium fluorosulfonate, lithium tetrafluoro oxalate phosphate, lithium difluoro oxalate phosphate, lithium difluoro oxalate borate, and lithium difluorophosphate; the mass ratio of the lithium salt additive in the lithium ion battery electrolyte of the high-voltage lithium cobaltate / silicon-carbon system is 0.5% to 2%; the mass ratio of the first additive in the lithium ion battery electrolyte of the high-voltage lithium cobaltate / silicon-carbon system is 1% to 4%; the mass ratio of the second additive in the lithium ion battery electrolyte of the high-voltage lithium cobaltate / silicon-carbon system is 0.5% to 1%; and the mass ratio of the third additive in the lithium ion battery electrolyte of the high-voltage lithium cobaltate / silicon-carbon system is 3% to 8%.

2. The electrolyte for high voltage lithium cobalt oxide / silicon carbon system lithium ion battery as claimed in claim 1, wherein, Any one or more of the following features are also included: a11) the second additive is selected from any one of 1,3-bis(3-fluoro-1-propargyl)-1,1,3,3-tetramethyldisiloxane and 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane; a21) the third additive is selected from fluoroethylene carbonate.

3. The electrolyte for high voltage lithium cobalt oxide / silicon carbon system lithium ion battery as claimed in claim 2, wherein, In feature a11), the second additive is selected from 1,3-bis(3-trimethylsilyl-1-propargyl)-1,1,3,3-tetramethyldisiloxane.

4. The electrolyte for high voltage lithium cobalt oxide / silicon carbon system lithium ion battery as claimed in claim 1, wherein, The lithium salt additive is selected from a combination of any two of lithium fluorosulfonate, lithium tetrafluoro oxalate phosphate, lithium difluoro oxalate borate, and lithium difluorophosphate.

5. The electrolyte for high voltage lithium cobalt oxide / silicon carbon system lithium ion battery as claimed in claim 4, wherein, The lithium salt additive is selected from a combination of lithium difluoro oxalate borate and lithium difluorophosphate.

6. The electrolyte for high voltage lithium cobalt oxide / silicon carbon system lithium ion battery as claimed in claim 1, wherein, Any one or more of the following features are also included: b11) the mass ratio of the lithium salt additive in the lithium ion battery electrolyte of the high-voltage lithium cobaltate / silicon-carbon system is 1% to 2%; b21) the mass ratio of the first additive in the lithium ion battery electrolyte of the high-voltage lithium cobaltate / silicon-carbon system is 3% to 4%; b31) the mass ratio of the second additive in the lithium ion battery electrolyte of the high-voltage lithium cobaltate / silicon-carbon system is 1%; b41) the mass ratio of the third additive in the lithium ion battery electrolyte of the high-voltage lithium cobaltate / silicon-carbon system is 5% to 6%.

7. The electrolyte for high voltage lithium cobalt oxide / silicon carbon system lithium ion battery as claimed in claim 1, wherein, Any one or more of the following features are also included: c1) the lithium salt is selected from the group consisting of one or more of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorosilicate, lithium aluminum chloride, lithium bis(oxalato)borate, lithium chloride, lithium bromide, lithium iodide, lithium bis(trifluoromethylsulfonyl)imide; c2) the lithium salt is present in the electrolyte for lithium ion batteries of the high-voltage lithium cobalt oxide / silicon-carbon system in an amount of 1 mol / L to 1.5 mol / L; c3) the non-aqueous organic solvent is selected from the group consisting of one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propyl propionate, ethyl n-butyrate, and methyl trifluoroethyl carbonate; c4) the non-aqueous organic solvent is present in the electrolyte for lithium ion batteries of the high-voltage lithium cobalt oxide / silicon-carbon system in an amount of 65% to 84% by mass.

8. A high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a high-voltage lithium cobalt oxide / silicon-carbon system lithium ion battery electrolyte, characterized in that, The electrolyte for lithium ion batteries of the high-voltage lithium cobalt oxide / silicon-carbon system is the electrolyte for lithium ion batteries of the high-voltage lithium cobalt oxide / silicon-carbon system according to any one of claims 1 to 7.

9. The high-voltage lithium cobalt oxide / silicon carbon system lithium-ion battery according to claim 8, characterized in that, Any one or more of the following conditions are also included: d1) the negative electrode comprises a negative electrode active material selected from silicon-carbon; d2) the positive electrode comprises a positive electrode active material selected from lithium cobalt oxide.

10. A battery module, characterized by A lithium ion battery of the high-voltage lithium cobalt oxide / silicon-carbon system according to claim 8 or 9.

11. A battery pack, characterized by A battery module as claimed in claim 10.

12. An electrical device, characterized by A lithium ion battery of the high-voltage lithium cobalt oxide / silicon-carbon system as claimed in claim 8 or 9, which is used as a power source for the electrical device; the electrical device includes a mobile device, an electric vehicle, an electric train, a satellite, a ship, and an energy storage system.

Images