CN114156526A

CN114156526A - A high-voltage electrolyte for lithium batteries

Info

Publication number: CN114156526A
Application number: CN202111457856.8A
Authority: CN
Inventors: 范修林; 吕岭; 陆迪; 陈立新
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2021-12-02
Filing date: 2021-12-02
Publication date: 2022-03-08

Abstract

The invention discloses a high-voltage electrolyte for lithium batteries, which belongs to the technical field of lithium battery electrolytes. The high-voltage electrolyte for lithium batteries includes lithium salts, organic solvents and silicon amine compounds as additives. Among them, the silicon amine compound can effectively improve the oxidation stability of the electrolyte, and can also form a stable and dense solid electrolyte interface on the surface of the positive electrode during the cycle, thereby reducing the side reaction of the electrolyte and improving the battery. Cyclic stability. In the present invention, the lithium salt, organic solvent and silicon amine compound in the high-voltage electrolyte for lithium batteries are specifically combined, and the concentration and proportion are further optimized, so that the high-voltage electrolyte of the present invention can be added with the high-voltage positive electrode. Good compatibility, while achieving better cycle stability and high coulombic efficiency of lithium-ion batteries.

Description

High-voltage electrolyte for lithium battery

Technical Field

The invention belongs to the technical field of lithium battery electrolyte, and particularly relates to a high-voltage electrolyte for a lithium battery.

Background

Sustainable development is very important to the development of modern society, and after the 21 st century, along with the increase of energy demand, high cost and insufficient allowance of fossil fuel, the problem of increasingly serious ecological environment damage and energy shortage is solved by utilizing green energy, so that the method becomes one of the main challenges of the modern society, and a proper and efficient large-scale energy storage system is needed to fully utilize the energy. Lithium ion batteries have the advantages of high energy density and power density, high rate performance, high safety, long cycle life and the like, are widely applied to portable electronic equipment, such as smart phones, digital cameras, notebook computers and the like, and gradually approach the fields of electric automobiles and hybrid electric automobiles. Although the technical development of the lithium ion battery is rapid, the market of the electric automobile is gradually expanded at present, and the energy density of the lithium ion battery is required to be improved. The energy density of lithium ion batteries depends to a large extent on the electrode material, and for more challenging positive and negative electrode material systems, new electrolyte systems need to be matched. Conventional commercial electrolytes consist of lithium hexafluorophosphate and carbonate solvents, and carbonate-based electrolytes are easily oxidatively decomposed on the surface of a high-voltage positive electrode when the battery is charged to 4.3V or more. Therefore, a need exists for new high voltage lithium ion battery electrolyte systems.

At present, a lot of researches are carried out on high-voltage electrolyte additives applied to high-voltage lithium cobaltate, nickel cobalt lithium manganate (ternary) and other cathode materials, but all the researches have obvious defects. The document "A dithio-based new electrolyte additive for improving electrolyte properties, Ionics,2020,26:6023-_0.8Co_0.1Mn_0.1O₂The Li button battery shows only 75.59 percent of capacity retention rate after 200 cycles under the condition of 0.3C within the voltage range of 3.0-4.3V. The document "thiophenylene derivatives as novel functional additives for high-voltage LiCoO₂The operation in lithium ion batteries, Electrochimica Acta, 2015,151:429-The capacity was only 84.8% of the initial discharge capacity. Although these additives can form a protective layer on the positive electrode to prevent side reactions between part of the electrolyte and the electrode, long-term cycle stability cannot meet the current requirements.

In addition, although there are some patents on electrolytes of the class of silicon amines, the composition of the electrolyte and the effect of the silicon amine compound are quite different from the present invention. For example, in the patent application publication No. CN104681867A, "a flame-retardant lithium ion battery electrolyte solvent and electrolyte and application", the disclosed Hexamethyldisilazane (HMDSA) is completely different from the additive structure of the present invention. In addition, hexamethyldisilazane mainly plays a role of a stabilizer in the electrolyte, other additives are additionally added into the prepared electrolyte, a lithium iron phosphate anode (the charge cut-off voltage is 3.7-4V) is adopted in the embodiment, and the maximum capacity retention rate after 50 circles is 90.1%.

Disclosure of Invention

Aiming at a series of problems of low coulombic efficiency, fast capacity attenuation and the like caused by poor high-voltage resistance of the current commercial electrolyte to the lithium ion battery, the invention aims to provide the electrolyte for the high-voltage lithium battery, the high-voltage electrolyte system has good compatibility with a high-voltage anode, and the cycle life and the coulombic efficiency of the lithium ion battery under the high-voltage condition are greatly improved.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides an application of a silicon amine compound, wherein the silicon amine compound is used as an additive of a lithium battery electrolyte, and the general formula of the silicon amine compound is shown as a structural formula I:

wherein R is₁、R₂、R₃、R₄And R₅Selected from the group consisting of H atoms, alkyl groups, alkenyl groups, ester groups, acetyl groups, haloalkyl groups, haloacetyl groups, benzene rings, and halobenzene rings.

In particular, the followingR is₁、R₂、R₃、R₄And R₅Is selected from-CH₃、-CH₂CH₂CH₃、-CH＝CH₂、-CH(CH₃)₂、-CH＝CHCH₃、-CH₂COOCH₃、-COCH₃、-CX₃、-C(X)₂CH₂CH₃、-COCX₃、-C6H₅and-C₆X₅And X is F, Cl, Br or I.

More specifically, said R₁、R₂、R₃、R₄And R₅Is selected from-CH₃、-CH₂COOCH₃、-COCH₃、-C(X)₂CH₂CH₃、-COCX₃、-C₆H₅and-C₆X₅And X is F, Cl, Br or I.

Preferably, the silamine compound is N, N-dimethyltrimethylsilylamine, N-bis (trimethylsilyl) glycine methyl ester, acetamidosilane, 1-dichloro-1-ethyl-N, N-dimethylsilylamine, N-methyl-N- (trimethylsilyl) trifluoroacetamide, N-phenylsilane amine, or pentafluorophenyldisilyldiethylamine.

The invention also provides an additive for the lithium battery electrolyte, which comprises a silicon amine compound, wherein the general formula of the silicon amine compound is shown as the structural formula I;

Specifically, the R is₁、R₂、R₃、R₄And R₅Is selected from-CH₃、-CH₂CH₂CH₃、-CH＝CH₂、-CH(CH₃)₂、-CH＝CHCH₃、-CH₂COOCH₃、-COCH₃、-CX₃、-C(X)₂CH₂CH₃、-COCX₃、-C6H₅and-C₆X₅And X is F, Cl, Br or I.

Furniture setOf the body, said R₁、R₂、R₃、R₄And R₅Is selected from-CH₃、-CH₂COOCH₃、-COCH₃、-C(X)₂CH₂CH₃、-COCX₃、-C₆H₅and-C₆X₅And X is F, Cl, Br or I.

The invention provides a high-voltage electrolyte for a lithium battery, which comprises an organic solvent, a lithium salt and an additive, wherein the additive is the additive.

The organic solvent comprises carbonic esters such as Propylene Carbonate (PC), diethyl carbonate (DEC), Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), Methyl Propyl Carbonate (MPC), gamma-butyrolactone (GBL), Methyl Propionate (MP), Fluorinated Ethylene Carbonate (FEC), propylene carbonate Trifluoride (TFPC), ethyl Difluoroacetate (DFAE), Ethyl Trifluoroacetate (ETFA) and the like, and the combination of two or more of fluoro carbonic esters.

Preferably, the organic solvent comprises a combination of two or more of EC, DEC, DMC, EMC, MP, GBL, FEC.

Preferably, the organic solvent is EC and DEC in a volume ratio of 1: 1.

Preferably, the organic solvent is EC and DMC in a volume ratio of 3: 7.

Preferably, the organic solvent is EC and MPC in a volume ratio of 1: 1.

Preferably, the organic solvent is EC and EMC in a volume ratio of 2: 8.

Preferably, the organic solvent is EC, DEC and EMC in a volume ratio of 1: 1.

Preferably, the organic solvent is EC, DMC and DEC, and the volume ratio is 6: 2: 2.

preferably, the organic solvent is EC, MPC and FEC in a volume ratio of 1: 1.

Preferably, the organic solvent is EC, EMC and DFAE in a volume ratio of 6: 2.

The lithium salt includes lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Bis (oxalato) borate (LiBOB), lithium difluoro (oxalato) borate (LiDFOB), lithium perchlorate (LiClO)₄) Lithium bis (difluorosulfonimide) (LiFSI), lithium bis (trifluoromethylsulfonimide) (LiTFSI) and lithium difluorophosphate (LiPO)₂F₂) And at least one of an inorganic anionic lithium salt and an organic anionic lithium salt.

Preferably, the lithium salt is lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Bis (oxalato) borate (LiBOB), lithium difluoro (oxalato) borate (LiDFOB), lithium perchlorate (LiClO)₄) Lithium bis (difluorosulfonimide) (LiFSI), lithium bis (trifluoromethylsulfonimide) (LiTFSI) and lithium difluorophosphate (LiPO)₂F₂) At least one of (1).

Preferably, the lithium salt is LiDFOB and LiBF₄The molar ratio is 1: 1.

Preferably, the lithium salt is LiFSI and LiBOB in a molar ratio of 1: 1.

Preferably, the lithium salt is LiTFSI and LiBOB in a molar ratio of 2: 1.

Preferably, the concentration of the lithium salt is 0.1 to 3 mol/L.

Preferably, the silicon amine compound accounts for 0.1-10% of the total mass of the electrolyte.

LiNi can be caused to be in a high-voltage state by the high-voltage electrolyte added with the additive_0.8Co_0.1Mn_0.1O₂After the MCMB button battery is cycled for 200 circles within the voltage range of 2.8-4.4V, the capacity retention rate is still 90%, and the average coulombic efficiency is as high as 99.9%; assembled LiCoO₂The Li button battery has a capacity retention ratio of 87% after circulating for 200 circles within a voltage range of 3.0-4.6V, and the average coulombic efficiency is up to 99.9%, which is superior to the performance of the current high-voltage electrolyte.

The silicon amine additives in the invention all contain silicon nitrogen chemical bonds, and the additives can be decomposed to form a protective and compact solid electrolyte interface in the charge-discharge cycle process of the battery, so that the side reaction of the electrolyte can be effectively avoided, and the anode material is protected, therefore, the electrolyte added with the silicon amine additives in the invention can meet the requirement of high voltage.

The invention provides a lithium battery, which comprises a positive active material and a negative active material which can be used for inserting and extracting lithium ions, and also comprises the electrolyte for the high-voltage lithium battery.

Preferably, the positive electrode active material is LiNi_0.8Co_0.1Mn_0.1O₂Or LiCoO₂(ii) a The negative active material is mesocarbon microbeads (MCMB) or a metallic lithium sheet.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention provides an application of a silicon amine compound, wherein the silicon amine compound is used as a high-voltage additive of a lithium battery electrolyte and can effectively improve the oxidation stability of the electrolyte. In addition, the additive can form a stable and compact solid electrolyte interface on the surface of the positive electrode in the circulating process, so that the side reaction of the electrolyte is reduced, and the circulating stability of the battery is improved.

(2) According to the invention, the organic solvent, the lithium salt and the silicon amine additive in the electrolyte of the high-voltage lithium battery are specifically combined, and the proportion and the concentration are further optimized, so that the electrolyte of the high-voltage lithium battery has excellent compatibility with a positive electrode and a negative electrode, and meanwhile, the lithium ion battery has better cycle stability and high coulombic efficiency.

(3) The high-voltage electrolyte for the lithium battery belongs to an electrolyte system with good film-forming property, wide electrochemical window and excellent rate capability, and has wide application prospect in the lithium battery.

Drawings

FIG. 1 is a structural diagram of N, N-dimethyl trimethyl silicane.

FIG. 2 is a structural diagram of N, N-bis (trimethylsilyl) glycine methyl ester.

FIG. 3 is a structural diagram of acetamidosilane.

FIG. 4 is a structural formula diagram of 1, 1-dichloro-1-ethyl-N, N-dimethyl-methylamine.

FIG. 5 is a structural diagram of N-methyl-N- (trimethylsilyl) trifluoroacetamide.

FIG. 6 is a structural diagram of N-phenylsilane amine.

FIG. 7 is a structural diagram of pentafluorodimethylsilyldiethylamine.

FIG. 8 is LiNi as an electrolyte prepared in example 1_0.8Co_0.1Mn_0.1O₂Cycle life plots in MCMB cells.

FIG. 9 shows LiCoO as an electrolyte prepared in example 2₂Cycle life graph in Li batteries.

FIG. 10 shows LiNi in the electrolyte prepared in example 3_0.8Co_0.1Mn_0.1O₂Charge and discharge curves in MCMB cells.

FIG. 11 shows LiCoO as an electrolyte prepared in example 4₂Charge and discharge curves in Li batteries.

FIG. 12 shows LiNi in the electrolyte prepared in example 5_0.8Co_0.1Mn_0.1O₂Cycle life graph in Li batteries.

FIG. 13 shows LiCoO as an electrolyte prepared in example 6₂Cycle life graph in Li batteries.

FIG. 14 shows LiNi in the electrolyte prepared in example 7_0.8Co_0.1Mn_0.1O₂Charge and discharge curves in MCMB cells.

FIG. 15 shows LiNi as a commercial electrolyte prepared in comparative example 1_0.8Co_0.1Mn_0.1O₂Cycle life plots in MCMB cells.

FIG. 16 shows LiCoO as a commercial electrolyte prepared in comparative example 2₂Cycle life graph in Li batteries.

FIG. 17 shows LiNi as a modified commercial ester-based electrolyte prepared in comparative example 3_0.8Co_0.1Mn_0.1O₂Charge and discharge curves in MCMB cells.

Detailed Description

Example 1

A high-voltage electrolyte for a lithium battery is prepared by the following steps:

a certain amount of LiPF₆Slowly dissolving in EC and DEC at volume ratio of 1: 1, and slowly adding high voltage additive N, N-dimethyl trimethyl silicane (CAS number: 2083-91-2, structure formula shown in figure 1) to make LiPF₆The concentration of the N, N-dimethyl trimethyl silicane is 0.1mol/L, so that the high-voltage additive N, N-dimethyl trimethyl silicane accounts for 0.1 percent of the total mass of the electrolyte, and the high-voltage electrolyte for the lithium battery is obtained after uniform mixing and complete clarification.

FIG. 8 shows LiNi in the electrolyte prepared in example 1_0.8Co_0.1Mn_0.1O₂Cycle life plots in MCMB cells. As can be seen from FIG. 8, after the electrolyte is cycled for 200 cycles under the charge-cut-off voltage of 4.4V, the capacity retention rate is as high as 90%, and the average coulombic efficiency is as high as 99.9% or more. And the capacity retention rate of the commercial ester-based electrolyte is lower than 80% after the commercial ester-based electrolyte is circulated for 67 circles under the condition, and the average coulombic efficiency is lower than 99%.

Example 2

slowly dissolving a certain amount of LiFSI in EC and DMC with the volume ratio of 3: 7, then slowly adding a high-voltage additive N, N-bis (trimethylsilyl) glycine methyl ester (CAS number: 25688-73-7, the structural formula is shown in figure 2), enabling the concentration of LiFSI to be 1mol/L, enabling the high-voltage additive N, N-bis (trimethylsilyl) glycine methyl ester to account for 1% of the total mass of the electrolyte, and stirring until the electrolyte is completely clear, thus obtaining the high-voltage electrolyte for the lithium battery.

FIG. 9 shows LiCoO as an electrolyte prepared in example 2₂Cycle life graph in Li batteries. As can be seen from fig. 9, even if the charge cut-off voltage is as high as 4.6V, the capacity retention rate of 87% can be still obtained after 200 cycles, and the average coulombic efficiency is as high as 99.9% or more. Compared with the traditional ester-based electrolyte, the circulating capacity retention rate and the coulombic efficiency are obviously improved.

Example 3

slowly dissolving a certain amount of LiDFOB in EC and MPC with the volume ratio of 1: 1, then slowly adding high-voltage additive acetamido silane (CAS number: 5661-22-3, structural formula shown in figure 3) to make the concentration of LiDFOB be 2mol/L and make the high-voltage additive acetamido silane account for 2% of the total mass of the electrolyte, and stirring until the electrolyte is completely clear, thus obtaining the high-voltage electrolyte for the lithium battery.

FIG. 10 shows LiNi in the electrolyte prepared in example 3_0.8Co_0.1Mn_0.1O₂Charge and discharge curves in MCMB cells. As can be seen from FIG. 10, LiNi_0.8Co_0.1Mn_0.1O₂The positive electrode material can be reversibly charged and discharged in the high-voltage electrolyte with high efficiency. Even under the charge cut-off voltage of 4.4V, the discharge specific capacity is not obviously attenuated along with the increase of the cycle number, and the polarization is obviously smaller than that of the commercial electrolyte, thereby indicating that the electrolyte is applied to LiNi_0.8Co_0.1Mn_0.1O₂High compatibility of the anode material and excellent film forming performance.

Example 4

slowly dissolving a certain amount of LiTFSI in EC and EMC with the volume ratio of 2: 8, then slowly adding a high-voltage additive 1, 1-dichloro-1-ethyl-N, N-dimethyl-silicon amine (CAS number: 67859-79-4, structural formula shown in figure 4) to make the concentration of LiTFSI be 3mol/L, and make the high-voltage additive 1, 1-dichloro-1-ethyl-N, N-dimethyl-silicon amine account for 5% of the total mass of the electrolyte, and uniformly mixing until the mixture is completely clear, thus obtaining the high-voltage electrolyte for the lithium battery.

FIG. 11 shows LiCoO as an electrolyte prepared in example 4₂Charge and discharge curves in Li batteries. As can be seen from FIG. 11, LiCoO₂The positive electrode material has an obvious charge-discharge platform in the high-voltage electrolyte and is highly reversible. Under the charge cut-off voltage of 4.6V, the discharge specific capacity has small attenuation amplitude along with the circulation, which shows the excellent high-voltage resistance of the electrolyte.

Example 5

a certain amount of LiPF₆Slowly dissolving in EC, DEC and EMC at a volume ratio of 1: 1, and slowly adding high voltage additive N-methyl-N- (trimethylsilyl) trifluoroacetamide (CAS number: 245889-78-4, structure formula shown in figure 5) to make LiPF₆The concentration of the high-voltage additive is 0.5mol/L, so that the high-voltage additive N-methyl-N- (trimethylsilyl) trifluoroacetamide accounts for 10 percent of the total mass of the electrolyte, and the high-voltage additive N-methyl-N- (trimethylsilyl) trifluoroacetamide is uniformly mixed until the high-voltage additive is completely clear, and the high-voltage electrolyte for the lithium battery is obtained.

FIG. 12 shows LiNi in the electrolyte prepared in example 5_0.8Co_0.1Mn_0.1O₂Cycle life graph in Li batteries. As can be seen from FIG. 12, the above electrolyte can still have a capacity retention rate of 91% after being cycled for 200 cycles under a charge-off voltage of 4.4V, and the average coulombic efficiency is as high as 99.9% or more. And the capacity retention rate of the commercial electrolyte after 200 cycles is far lower than that of the high-voltage electrolyte.

Example 6

mixing a mixture of 1: 1 LiDFOB and LiBF₄Slowly dissolving in EC, DMC and DEC at volume ratio of 6: 2, and slowly adding high voltage additive N-phenylsilane amine (CAS number: 5578-85-8, structure formula shown in FIG. 6) to make LiDFOB and LiBF₄The concentration of the N-phenylsilane amine is 2.5mol/L, so that the high-voltage additive N-phenylsilane amine accounts for 8 percent of the total mass of the electrolyte, and the high-voltage additive N-phenylsilane amine is uniformly mixed until the mixture is completely clear, and the high-voltage electrolyte for the lithium battery is obtained.

FIG. 13 shows LiCoO as an electrolyte prepared in example 6₂Charge and discharge curves in Li batteries. As can be seen from FIG. 13, the electrolyte still has a capacity retention rate of 84% after being cycled for 200 cycles under a charge-cut-off voltage of 4.6V, and the average coulombic efficiency is as high as 99.9% or more. Compared with the traditional commercial ester-based electrolyte, the circulating capacity retention rate and the coulombic efficiency are greatly improved.

Example 7

mixing a mixture of 1: 1, slowly dissolving LiFSI and LiBOB in EC, MPC and FEC with the volume ratio of 1: 1, then slowly adding a high-voltage additive pentafluoro-phenyl dimethyl-silicon-based diethylamine (CAS number: 55485-74-0, the structural formula is shown in figure 7) to ensure that the concentration of the LiFSI and the LiBOB is 1.5mol/L and the high-voltage additive pentafluoro-phenyl-dimethyl-silicon-based diethylamine accounts for 0.5 percent of the total mass of the electrolyte, and uniformly mixing until the mixture is completely clear, thus obtaining the high-voltage electrolyte for the lithium battery.

FIG. 14 shows LiNi in the electrolyte prepared in example 7_0.8Co_0.1Mn_0.1O₂Charge and discharge curves in MCMB cells. As can be seen from FIG. 14, LiNi_0.8Co_0.1Mn_0.1O₂The positive electrode material has an obvious charge-discharge platform in the high-voltage electrolyte and is highly reversible. Under the charge cut-off voltage of 4.4V, the discharge specific capacity is almost not attenuated along with the increase of the cycle number, and the fact that the electrolyte is applied to LiNi is shown_0.8Co_0.1Mn_0.1O₂High compatibility of the positive electrode material.

Comparative example 1

A certain amount of LiPF₆Slowly dissolved in EC and DEC at a volume ratio of 3: 7 to make lithium salt LiPF₆The concentration of (2) is 1.5 mol/L. Stirring until the electrolyte is completely clarified, and obtaining the commercial ester-based electrolyte of the lithium ion battery.

FIG. 15 shows LiNi as an electrolyte prepared in comparative example 1_0.8Co_0.1Mn_0.1O₂Cycle life plots in MCMB cells. As can be seen from FIG. 15, the above electrolyte has a specific discharge capacity of only 103.6mAh g after 200 cycles of circulation^-1The capacity retention rate is only 58.6%, the average coulombic efficiency is 99.5%, and the coulombic efficiency and the cycle performance are greatly reduced compared with the high-voltage electrolyte.

Comparative example 2

A certain amount of LiPF₆Slowly dissolving in EC, DEC and DMC at volume ratio of 1: 1 to obtain lithium saltLiPF₆The concentration of (2) is 1 mol/L. Stirring until the electrolyte is completely clarified, and obtaining the commercial ester-based electrolyte of the lithium ion battery.

FIG. 16 shows LiCoO as an electrolyte for comparative example 2₂Cycle life graph in Li batteries. As can be seen from fig. 16, at a charge cut-off voltage as high as 4.6V, the cycle capacity decayed rapidly, and the capacity retention rate after 200 cycles was 55.7%. In addition, the coulombic efficiency is low, the average coulombic efficiency is 99.0%, and the application requirement of high voltage cannot be met.

Comparative example 3

A certain amount of LiPF₆Slowly dissolving in EC and DEC at volume ratio of 3: 7, slowly adding Vinylene Carbonate (VC) as additive to make lithium salt LiPF₆The concentration of the additive VC is 1.2mol/L, so that the additive VC accounts for 2 percent of the total mass of the electrolyte. Stirring until the electrolyte is completely clarified, and obtaining the commercial ester-based electrolyte modified by the lithium ion battery.

FIG. 17 shows LiNi in the electrolyte prepared in comparative example 3_0.8Co_0.1Mn_0.1O₂Charge and discharge curves in MCMB cells. As can be seen from FIG. 17, LiNi_0.8Co_0.1Mn_0.1O₂The positive electrode material in the modified commercial ester-based electrolyte has an unobvious charge-discharge platform along with the increase of the cycle number, the polarization is increased rapidly, and the reversible capacity is attenuated rapidly.

LiCoO in examples and comparative examples₂/Li、LiNi_0.8Co_0.1Mn_0.1O₂/Li and LiNi_0.8Co_0.1Mn_0.1O₂Manufacturing and testing an MCMB button battery:

(1) positive pole piece: subjecting LiCoO to condensation₂Or LiNi_0.8Co_0.1Mn_0.1O₂Adding polyvinylidene fluoride (PVDF) serving as a binder and conductive carbon black into N-methylpyrrolidone (NMP) according to the ratio of 9:0.5:0.5, uniformly mixing to obtain slurry, uniformly coating the slurry on an aluminum foil current collector, drying at 100 ℃, and punching by using a punching machine, wherein the positive pole piece is a circular piece with the diameter of 12.0 mm;

(2) and Li negative electrode: adopting a metal lithium sheet with the thickness of 400 microns and the diameter of 16.0 millimeters;

graphite negative pole piece: adding the intermediate phase carbon microsphere powder, binder lithiation polyacrylic acid (LiPAA) and conductive carbon black into deionized water according to the ratio of 8: 1, uniformly mixing to obtain slurry, uniformly coating the slurry on a copper foil current collector, drying at 100 ℃, and punching by using a punching machine, wherein a negative pole piece is a wafer with the diameter of 14.0 mm;

(3) electrolyte solution: electrolytes prepared in examples 1 to 7 and comparative examples 1 to 3;

(4) a diaphragm: cutting a Polyethylene (PE) single-layer diaphragm wafer with the diameter of 19.0 mm by using a punching machine;

(5) assembling the battery: in a glove box (O)₂<0.1ppm，H₂O<0.1ppm), assembling the button lithium ion battery according to the sequence of the positive electrode shell, the positive electrode plate, the Polyethylene (PE) single-layer diaphragm wafer, the negative electrode wafer, the stainless steel sheet, the spring piece and the negative electrode shell, adding the electrolyte prepared in the examples 1-7 and the comparative examples 1-3, and finally packaging to obtain a test battery;

(6) and (3) testing the battery: the electrolytes in examples 1 to 7 and comparative examples 1 to 3 correspond to batteries 1 to 10, LiNi_0.8Co_0.1Mn_0.1O₂/Li(2.8-4.4V)、LiNi_0.8Co_0.1Mn_0.1O₂/MCMB (2.8-4.4V) and LiCoO₂Li (3-4.6V) button half cell is activated for 2 circles at 0.1C multiplying power at room temperature (25 ℃) and then long-circulating at 0.5C multiplying power; the test results are shown in FIGS. 8-17.

Claims

1. the application of a kind of silicon amine compound, it is characterized in that, described silicon amine compound is used as the additive of lithium battery electrolyte, and its general formula is as shown in structural formula I:

wherein R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are selected from H atom, alkyl group, alkenyl group, ester group, acetyl group, haloalkyl group, haloacetyl group, benzene ring and halobenzene ring.

2. The application of the silicon amine compound according to claim 1, wherein the R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are selected from -CH ₃ , -CH ₂ CH ₂ CH ₃ , -CH=CH ₂ , -CH(CH ₃ ) ₂ , -CH=CHCH ₃ , -CH ₂ COOCH ₃ , -COCH ₃ , -CX ₃ , -C(X) ₂ CH ₂ CH ₃ , -COCX ₃ , - _C6H5 and _-C6X5 , X= _F , _Cl , Br or I.

3. The application of the silicon amine compound according to claim 2, wherein the R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are selected from -CH ₃ , -CH ₂ COOCH ₃ , -COCH ₃ , _-C ( _X ₎ _2CH2CH3 , _-COCX3 , _-C6H5 and _-C6X5 , X=F, _Cl , Br or I.

4. the application of the silicon amine compound as claimed in claim 3, is characterized in that, described silicon amine compound is N,N-dimethyl trimethylsilylamine, N,N-bis(trimethylsilane) yl)glycine methyl ester, acetamidosilane, 1,1-dichloro-1-ethyl-N,N-dimethylsilamine, N-methyl-N-(trimethylsilyl)trifluoroacetamide , N-phenylsilylamine or pentafluorophenylsilyldiethylamine.

5. an additive for lithium battery electrolyte, is characterized in that, comprises silicon amine compound, and its general formula is as shown in structural formula I:

6. The additive for lithium battery electrolyte according to claim 5, wherein the R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are selected from -CH ₃ , -CH ₂ CH ₂ CH ₃ , -CH=CH ₂ , -CH(CH ₃ ) ₂ , -CH=CHCH ₃ , -CH ₂ COOCH ₃ , -COCH ₃ , -CX ₃ , -C(X) ₂ CH ₂ CH ₃ , -COCX ₃ , _-C6H5 and _-C6X5 , X=F, _Cl , Br or I.

7. The additive for lithium battery electrolyte according to claim 6, wherein said R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are selected from -CH ₃ , -CH ₂ COOCH ₃ , _-COCH3 , _-C ( _X ₎ _2CH2CH3 , _-COCX3 , _-C6H5 and _-C6X5 , X=F, _Cl , Br or I.

8. The additive for lithium battery electrolyte according to claim 7, wherein the silicon amine compound is N,N-dimethyltrimethylsilamine, N,N-bis(trimethylsilylamine) Silyl)glycine methyl ester, acetamidosilane, 1,1-dichloro-1-ethyl-N,N-dimethylsilamine, N-methyl-N-(trimethylsilyl)trifluoro Acetamide, N-phenylsilylamine or pentafluorophenylsilyldiethylamine.

9. A high-voltage electrolyte for a lithium battery, characterized in that it comprises an organic solvent, a lithium salt and an additive, and the additive is the additive of any one of claims 5-8, wherein the lithium salt concentration is 0.1 -3mol/L, the additive accounts for 0.1%-10% of the total mass of the electrolyte.

10. The high-voltage electrolyte for lithium batteries according to claim 9, wherein the organic solvent comprises propylene carbonate, diethyl carbonate, ethylene carbonate, ethyl methyl carbonate, carbonic acid Dimethyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl propionate, fluorinated ethylene carbonate, propylene trifluorocarbonate, ethyl difluoroacetate, ethyl trifluoroacetate and other carbonates and fluorocarbons Two or more combinations of carbonates; the lithium salts include lithium hexafluorophosphate, lithium tetrafluoroborate, bis-oxalate boric acid, lithium difluorooxalate borate, lithium perchlorate, lithium bis-difluorosulfonimide and bis- At least one of inorganic anion lithium salts such as lithium trifluoromethanesulfonimide and lithium difluorophosphate, and organic anion lithium salts.