CN113471533A - Electrolyte of silicon-carbon negative electrode lithium ion battery and lithium ion battery - Google Patents

Electrolyte of silicon-carbon negative electrode lithium ion battery and lithium ion battery Download PDF

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CN113471533A
CN113471533A CN202110572717.3A CN202110572717A CN113471533A CN 113471533 A CN113471533 A CN 113471533A CN 202110572717 A CN202110572717 A CN 202110572717A CN 113471533 A CN113471533 A CN 113471533A
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electrolyte
ion battery
lithium ion
silicon
lithium
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赵坤
沈剑
俞金萍
梁大宇
王涂亮
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Hefei Gotion High Tech Power Energy Co Ltd
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Hefei Guoxuan High Tech Power Energy Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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Abstract

The invention discloses an electrolyte of a silicon-carbon cathode lithium ion battery, which comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is N, N, N-trifluoromethyl cyano ester sulfonic acid ammonium salt. The invention also discloses a silicon-carbon cathode lithium ion battery which comprises the electrolyte. According to the invention, the N, N, N-trifluoromethyl cyano ester sulfonic acid ammonium salt is added into the electrolyte, so that the high-temperature storage gas generation of the silicon-carbon cathode lithium ion battery can be inhibited, the internal resistance is reduced, and the high-temperature storage capacity retention rate and the high-temperature cycle performance are improved.

Description

Electrolyte of silicon-carbon negative electrode lithium ion battery and lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to electrolyte of a silicon-carbon negative electrode lithium ion battery and the lithium ion battery.
Background
The lithium ion battery has the advantages of high working voltage, high specific energy density, long cycle life, low self-discharge rate, no memory effect, small environmental pollution and the like, and is widely applied to various electronic consumer goods and power battery markets. In order to satisfy the requirements of high driving range, normal use in high and low temperature environments, rapid charging, and long service life of electric vehicles, lithium ion secondary batteries are required to have higher energy density, more excellent high temperature performance, and long cycle performance.
At present, one of the effective methods for increasing the energy density of lithium ion batteries is to use a silicon-carbon negative electrode material to replace the traditional graphite negative electrode. However, the continuous consumption of electrolyte is caused by particle breakage caused by volume expansion and contraction of the silicon material in the circulation process of the silicon-carbon negative electrode material, the potential safety hazard is also caused when the internal resistance of the battery is increased to deteriorate the performance of the battery, and the situation is more serious under the high-temperature condition.
Disclosure of Invention
Based on the technical problems in the background art, the invention provides an electrolyte of a silicon-carbon negative electrode lithium ion battery and the lithium ion battery.
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is N, N, N-trifluoromethyl cyano ester sulfonic acid ammonium salt.
Preferably, the structural formula of the high temperature resistant additive is shown as formula (1):
Figure BDA0003083148340000021
in the formula (1), R1、R2Is not particularly limited; preferably, in the formula (1), R1、R2Each independently selected from C containing substituent or not containing substituent1-C3Alkyl, substituted or unsubstituted C1-C3Alkenyl, substituted or unsubstituted C1-C3Any one of alkynyl, aryl containing substituent or not, sulfonyl containing substituent or not by selecting R1、R2The film forming component of the quaternary ammonium salt compound can be optimized, an inorganic film and an organic film can be formed simultaneously, the stability of an interfacial film is improved, and the film forming impedance is ensured not to be increased obviously(ii) a Preferably, the substituent is F or a fluorine-containing substituent, so that the oxidation resistance of the electrolyte can be improved, and the cycle performance of the battery can be improved.
In the formula (1), the reaction mixture is,
Figure BDA0003083148340000022
denotes an anion, preferably,
Figure BDA0003083148340000023
is selected from Br-、PF6 -、BF4 -、FSI-、TFSI-Any one of them.
Preferably, the high temperature resistant additive has a structural formula:
Figure BDA0003083148340000024
Figure BDA0003083148340000025
or
Figure BDA0003083148340000026
Preferably, the mass of the high-temperature resistant additive accounts for 0.05-10% of the total mass of the electrolyte; preferably, the mass of the high-temperature resistant additive accounts for 0.1-5% of the total mass of the electrolyte; when the content of the high-temperature resistant additive is too low, the formed cathode interface film is not enough to prevent the electrolyte from further reacting, and the performance of the lithium ion battery is not obviously improved. When the content is too high, the resistance at the negative electrode interface increases, which in turn deteriorates the performance of the lithium ion battery.
The contents of the lithium salt electrolyte, the film-forming additive and the nonaqueous organic solvent are not particularly limited; preferably, the mass of the lithium salt electrolyte accounts for 10-15% of the total mass of the electrolyte, and the mass of the film forming additive accounts for 1-5% of the total mass of the electrolyte.
Preferably, the film forming additive is one or more selected from the group consisting of ethylene sulfate, fluoroethylene carbonate, ethylene carbonate, 1, 3-propane sultone, and propenyl-1, 3-sultone.
Preferably, the lithium salt electrolyte is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bisoxalato borate, lithium difluorooxalato borate, lithium bistrifluoromethanesulfonylimide, lithium difluorosulfonimide, lithium difluorophosphate and lithium difluorooxalato phosphate.
Preferably, the non-aqueous organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate and propyl butyrate.
A silicon-carbon cathode lithium ion battery comprises the electrolyte.
Preferably, the silicon-carbon negative electrode lithium ion battery further comprises a positive plate, a negative plate, a diaphragm and a shell.
Preferably, the positive plate comprises a positive current collector and a positive membrane arranged on the positive current collector; the positive electrode diaphragm comprises a positive electrode active material, a conductive agent and a binder; the positive electrode active material is selected from lithium cobaltate (LiCoO)2) Spinel type lithium manganate (LiMn)2O4) Olivine-type lithium iron phosphate (LiFePO)4) Ternary material LiaNixAyB(1-x-y)O2One or more of the above; the ternary material LiaNixAyB(1-x-y)O2Wherein A, B is independently selected from one of Co, Al and Mn, A and B are different, a is more than or equal to 0.95 and less than or equal to 1.2, 0<x<1，0<y<1, and x + y<1. The types of the conductive agent and the binder are not particularly limited, and may be selected according to actual requirements.
The kind of the separator is not particularly limited and may be selected according to actual needs, and preferably, the separator is selected from the group consisting of a polyethylene film, a polypropylene film, a polyvinylidene fluoride film, and a multi-layer coated composite film thereof.
The invention has the following beneficial effects:
according to the invention, the additive N, N, N-trifluoromethyl cyano ester sulfonic acid ammonium salt is added into the electrolyte, so that hydrofluoric acid generated by reaction of lithium salt and trace water in the electrolyte can be eliminated, and the battery gas generation caused by reaction of organic solvent components of the electrolyte with lithium salt and the like under the catalysis of hydrofluoric acid can be inhibited; meanwhile, an SEI film is preferentially generated on the surface of the silicon cathode in the first cycle process of the battery, and the organic lithium compound and the inorganic lithium compound generated by the reaction have good thermal stability and electric conductivity, so that the increase of the thickness of the SEI film caused by the continuous reaction of the electrolyte can be inhibited, the internal resistance of the battery is reduced, the gas generation of the battery is further improved, and the high-temperature storage and cycle performance of the battery are improved.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to specific examples.
Example 1
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 1, and the structural formula of the compound 1 is as follows:
Figure BDA0003083148340000041
the mass of the compound 1 accounts for 0.05 percent of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The preparation method of the silicon-carbon cathode lithium ion battery comprises the following steps:
(1) preparation of positive plate
LiNi serving as a positive electrode active material0.8Co0.1Mn0.1O2Conductive agent Super-P and adhesive PVDF (polyvinylidene fluoride) according to mass ratio LiNi0.8Co0.1Mn0.1O2Mixing Super-P and PVDF (97.5: 1: 1.5), adding solvent N-methyl pyrrolidone, and stirring under the action of a vacuum stirrer until the system is uniform and transparent to obtain anode slurry; uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil with the thickness of 10 mu m; drying the aluminum foil at room temperature, transferring the aluminum foil to a 110 ℃ oven for drying for 2h, and then performing cold pressing and slitting to obtain a positive plate;
(2) preparation of negative plate
Mixing a silicon-carbon composite material serving as a negative electrode active material, sodium carboxymethyl cellulose (CMC) serving as a thickening agent, Styrene Butadiene Rubber (SBR) serving as a binder and a Super-P serving as a conductive agent according to a mass ratio of CMC to SBR to Super-P to 94.5:2:2.5:1, adding deionized water, and obtaining negative electrode slurry under the action of a vacuum mixer; uniformly coating the negative electrode slurry on a negative electrode current collector copper foil with the thickness of 6 mu m; the copper foil is dried at room temperature, transferred to a drying oven at 110 ℃ for drying for 2h, and then subjected to cold pressing and slitting to obtain a negative plate;
(3) preparation of the electrolyte
In an argon atmosphere glove box with the water content of less than 0.1ppm, fully dried electrolyte lithium salt is dissolved in a non-aqueous organic solvent, then a film forming additive and a high temperature resistant additive are added, and the electrolyte is obtained after uniform mixing;
(4) preparation of the separator
Selecting polypropylene of (12+1+1) um to coat the ceramic diaphragm;
(5) preparation of the separator
Stacking the positive plate, the diaphragm and the negative plate in sequence to enable the diaphragm to be positioned between the positive plate and the negative plate to play a role in isolation, and then winding to obtain a bare cell; placing the bare cell in an outer packaging shell, injecting the prepared electrolyte into the dried bare cell, and performing vacuum packaging, standing, formation, shaping and other processes to obtain the silicon-carbon negative electrode lithium ion battery.
Example 2
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high-temperature resistant additive, wherein the high-temperature resistant additive is a compound 1, and the mass of the compound 1 accounts for 2.5% of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 3
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high-temperature resistant additive, wherein the high-temperature resistant additive is a compound 1, and the mass of the compound 1 accounts for 10% of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 4
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 2, and the structural formula of the compound 2 is as follows:
Figure BDA0003083148340000071
the mass of the compound 2 accounts for 2.5 percent of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 5
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 3, and the structural formula of the compound 3 is as follows:
Figure BDA0003083148340000072
the mass of the compound 3 accounts for 2.5 percent of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 6
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 4, and the structural formula of the compound 4 is as follows:
Figure BDA0003083148340000081
the mass of the compound 4 accounts for 2.5 percent of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 7
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 5, and the structural formula of the compound 5 is as follows:
Figure BDA0003083148340000082
the mass of the compound 5 accounts for 2.5 percent of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 8
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 6, and the structural formula of the compound 6 is as follows:
Figure BDA0003083148340000091
the mass of the compound 6 accounts for 2.5 percent of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 9
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 7, and the structural formula of the compound 7 is as follows:
Figure BDA0003083148340000101
the mass of the compound 7 accounts for 2.5 percent of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 10
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 8, and the structural formula of the compound 8 is as follows:
Figure BDA0003083148340000102
the mass of the compound 8 accounts for 2.5 percent of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 11
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 9, and the structural formula of the compound 9 is as follows:
Figure BDA0003083148340000111
the mass of the compound 9 accounts for 2.5 percent of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Example 12
The electrolyte of the silicon-carbon cathode lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is a compound 10, and the structural formula of the compound 10 is as follows:
Figure BDA0003083148340000112
the mass of the compound 10 accounts for 2.5% of the total mass of the electrolyte;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate, and the mass of the vinyl sulfate accounts for 2.5 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Comparative example 1
The electrolyte of the lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent and a film forming additive;
wherein the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate (DTD), and the mass of the vinyl sulfate accounts for 0.05 percent of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Comparative example 2
The electrolyte of the lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent and a film forming additive;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is vinyl sulfate (DTD), and the mass of the vinyl sulfate accounts for 2.5% of the total mass of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Comparative example 3
The electrolyte of the lithium ion battery comprises electrolyte lithium salt, a non-aqueous organic solvent and a film forming additive;
the electrolyte lithium salt is LiPF6，LiPF6The mass of (a) accounts for 12.5% of the total mass of the electrolyte;
the film forming additive is Vinylene Carbonate (VC), and the weight of the vinylene carbonate accounts for 2.5% of the total weight of the electrolyte;
the nonaqueous organic solvent is obtained by mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to the mass ratio of EC to EMC to DEC to 3 to 5 to 2.
The procedure for preparing a silicon-carbon negative electrode lithium ion battery was the same as in example 1.
Test examples lithium ion battery electrochemical performance test
(1) High temperature storage capacity retention test for lithium ion batteries
Charging the lithium ion battery at room temperature with a constant current of 1C until the voltage is 4.2V, then charging at a constant voltage of 4.2V until the current is less than 0.05C, and then discharging at a constant current of 1C until the voltage is 2.75V; charging with a constant current of 1C until the voltage is 4.2V, then charging with a constant voltage of 4.2V until the current is less than 0.05C, and testing the discharge capacity of the lithium ion battery at the moment and recording as D0; and then storing the lithium ion battery at 60 ℃ for 30 days, discharging at a constant current of 1C until the voltage is 2.75V after the storage is finished, and testing the discharge capacity of the lithium ion battery at the moment and recording the discharge capacity as D1. Each group was tested for 10 lithium ion batteries and the average was taken.
The capacity retention (%) of the lithium ion battery after 30 days of storage at 60 ℃ was (D1/D0) × 100%.
(2) High-temperature storage gas production test of lithium ion battery
Charging the lithium ion battery at a constant current of 1C to a voltage of 4.2V at room temperature, then charging at a constant voltage of 4.2V to a current of less than 0.05C, testing the initial volume of the lithium ion battery at the moment by adopting a drainage method, marking as V0, then placing the lithium ion battery into a constant temperature box at 60 ℃ for storage for 30 days, taking out the lithium ion battery after the storage is finished, testing the volume of the lithium ion battery at the moment by adopting a drainage method, and marking as V1. 10 lithium ion secondary batteries were tested per group and the average value was taken.
The lithium ion battery has a volume expansion ratio (%) of (V1-V0)/V0 × 100% after 30 days of storage at 60 ℃.
(3) Cycle performance testing of lithium ion batteries
Charging the lithium ion battery at room temperature by using a constant current of 1C until the voltage is 4.2V, then charging at a constant voltage of 4.2V until the current is less than 0.05C, then discharging at a constant current of 1C until the voltage is 2.75V, testing the discharge capacity of the lithium ion battery at the moment as an initial capacity and marking as C0, and the initial internal resistance as R0; the cell is placed in a constant temperature box at 60 ℃ and charged with 1C constant current until the voltage is 4.2V, then charged with 4.2V constant voltage until the current is less than 0.05C, and then discharged with 1C constant current until the voltage is 2.75V, the cycle is cycled for 500 weeks, the discharge capacity at 500 weeks is tested and recorded as C1, and the internal resistance is recorded as R1. Each group was tested for 10 lithium ion batteries and the average was taken.
Capacity retention (%) of the lithium ion battery at 500 cycles was (C1/C0) × 100%.
The lithium ion battery has 500-cycle internal resistance increase rate (%) (R1-R0)/R0 multiplied by 100%.
Electrochemical performance tests were performed on the lithium ion batteries prepared in examples 1 to 12 and comparative examples 1 to 3 in the above-described manner, and the results are shown in table 1:
TABLE 1 results of electrochemical Performance test of examples 1 to 12 and comparative examples 1 to 3
Figure BDA0003083148340000141
The test results in table 1 show that the addition of the additive N, N, N-trifluoromethyl cyano ester sulfonic acid ammonium salt in the electrolyte can inhibit high-temperature storage gas generation of the lithium ion battery, reduce internal resistance, and improve high-temperature storage capacity retention rate and high-temperature cycle performance.
In examples 1 to 4, it can be seen that too low an amount of ammonium salt of N, N-trifluoromethylcyanoestersulfonate has less influence on the high-temperature storage and cycle performance of the battery, while too high an amount increases the internal resistance of the battery, which is also disadvantageous in improving the high-temperature storage and cycle stability of the battery.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims (10)

1. The electrolyte of the silicon-carbon cathode lithium ion battery is characterized by comprising electrolyte lithium salt, a non-aqueous organic solvent, a film forming additive and a high temperature resistant additive, wherein the high temperature resistant additive is N, N, N-trifluoromethyl cyano ester sulfonic acid ammonium salt.
2. The electrolyte of the silicon-carbon negative electrode lithium ion battery as claimed in claim 1, wherein the structural formula of the high temperature resistant additive is as shown in formula (1):
Figure FDA0003083148330000011
3. the electrolyte of a silicon-carbon negative electrode lithium ion battery according to claim 2, wherein in the formula (1), R is1、R2Each independently selected from C containing substituent or not containing substituent1-C3Alkyl, substituted or unsubstituted C1-C3Alkenyl, substituted or unsubstituted C1-C3Any one of alkynyl, aryl with or without substituent, sulfonyl with or without substituent; preferably, the substituent is F or a fluorine-containing substituent;
in the formula (1), the reaction mixture is,
Figure FDA0003083148330000012
represents an anion selected from Br-、PF6 -、BF4 -、FSI-、TFSI-Any one of them.
4. The electrolyte of a silicon-carbon negative electrode lithium ion battery as claimed in any one of claims 1 to 3, wherein the structural formula of the high temperature resistant additive is:
Figure FDA0003083148330000013
Figure FDA0003083148330000021
Figure FDA0003083148330000022
or
Figure FDA0003083148330000023
5. The electrolyte of a silicon-carbon negative electrode lithium ion battery according to any one of claims 1 to 4, wherein the mass of the high-temperature resistant additive accounts for 0.05 to 10 percent of the total mass of the electrolyte.
6. The electrolyte of a silicon-carbon negative electrode lithium ion battery according to any one of claims 1 to 5, wherein the mass of the lithium salt electrolyte accounts for 10 to 15% of the total mass of the electrolyte, and the mass of the film-forming additive accounts for 1 to 5% of the total mass of the electrolyte.
7. The electrolyte of a silicon-carbon negative electrode lithium ion battery according to any one of claims 1 to 6, wherein the film forming additive is one or more selected from the group consisting of ethylene sulfate, fluoroethylene carbonate, ethylene carbonate, 1, 3-propane sultone, and propenyl-1, 3-sultone.
8. The electrolyte of a silicon-carbon negative electrode lithium ion battery according to any one of claims 1 to 7, wherein the lithium salt electrolyte is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium biethanedioate borate, lithium difluorooxalate borate, lithium bistrifluoromethanesulfonylimide, lithium difluorosulfonimide, lithium difluorophosphate and lithium difluorooxalate phosphate.
9. The electrolyte of a silicon-carbon negative electrode lithium ion battery according to any one of claims 1 to 8, wherein the non-aqueous organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate and propyl butyrate.
10. A silicon-carbon negative electrode lithium ion battery comprising the electrolyte of any one of claims 1 to 9.
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