Negative electrode binder, lithium ion battery negative electrode, and method for preparing the same

Abstract

The application provides a negative electrode binder, which comprises a copolymer of 1,1-difluoroethylene, epoxy fluoropropane and compound 1; the compound 1 has multiple complexing sites of lithium ions, so that the lithium ions can be uniformly distributed on the surface of a carbon material negative electrode. The generation of lithium dendrites is inhibited. Different from the prior art, the negative electrode binder provided by the application has the complexing ability with lithium ions, so that the crystallization kinetic characteristics during lithium ion deposition can be changed, the lithium ions can be more uniformly deposited on the surface of carbon particles of the negative electrode, and the generation of lithium dendrites is inhibited. The application further provides a preparation method of the negative electrode binder. Furthermore, the application further provides a lithium battery negative electrode comprising the negative electrode binder and a preparation method of the lithium battery negative electrode. Meanwhile, the application further provides the application of the lithium battery negative electrode.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium ion batteries, and particularly relates to a lithium ion battery negative electrode binder as well as a preparation method and application thereof. BACKGROUND

[0002] With the development of the electric vehicle industry, the lithium ion battery technology has also made great progress. The lithium ion power battery is a kind of high-performance battery that has developed rapidly in recent years, which usually uses graphite and other materials as the negative electrode, and lithium iron phosphate, lithium cobaltate, lithium titanate, etc. as the positive electrode. This kind of battery has the characteristics of high energy density, high voltage, wide working temperature range, long storage life, etc., and is widely used not only in the field of electric vehicles, but also in the fields of energy storage systems, consumer electronics and military.

[0003] Although the lithium ion battery technology has developed rapidly and has many advantages, the requirements of electric vehicle manufacturers for the energy density, cycle life and safety performance of lithium ion batteries are also getting higher and higher.

[0004] At present, the commercial lithium ion battery negative electrode is mainly prepared by graphite-based carbon materials. Since graphite has a low lithium intercalation potential, under some harsh charging conditions (such as low temperature, high rate, etc.), when lithium ions are deposited on the surface of the graphite negative electrode to form metallic lithium, the metallic lithium will preferentially deposit in the form of dendrites on the surface of the graphite negative electrode. The dendritic deposit of metallic lithium is extremely uneven and unstable, and this deposition process can lead to active lithium capacity loss and internal micro-short circuit of the battery. Moreover, the long lithium dendrites may also pierce the separator to cause internal short circuit and thermal runaway of the battery. Therefore, preventing the generation of lithium dendrites is a major problem affecting the cycle life and safety performance of lithium ion batteries.

[0005] The Chinese invention patent application with the publication number CN118270765A discloses a carbon material graphite negative electrode additive preparation method, graphite negative electrode and application. The invention successfully loads metal particle elements in the carbon material, which are uniformly distributed on the surface of the carbon material. The preparation method is simple and easy to realize large-scale production. The invention loads Ga and In elements in the carbon material to form an additive, and Ga and In are fused to form nanoparticles, which are uniformly distributed on the surface of the carbon material. The gallium-indium nanoparticles have good adsorption effect on lithium, provide active sites for lithium deposition, induce uniform deposition of lithium ions, inhibit lithium dendrite precipitation of graphite, are conducive to improving the capacity in the cycle process of the battery, prolonging the service life and improving the safety of the battery. The graphite negative electrode prepared by the invention is applied in soft package batteries, improves the capacity retention rate of the soft package batteries, and is conducive to improving the service life of the soft package batteries.

[0006] The Chinese patent application with the publication number CN118748253A provides a simple and effective technical solution for inhibiting lithium ion battery negative electrode lithium precipitation. The solution uses MXene material as an additive in the negative electrode material. This material can effectively inhibit the growth of negative electrode lithium dendrites under low temperature conditions or high rate charging and discharging conditions, improve the lithium precipitation state, and thus obtain obvious improvement in low temperature performance or rate performance. The technical solution of the invention is simple and effective, easy to implement and promote in existing battery production, and has significant industrial practical value; in particular, for electric vehicles (such as electric cars, electric bicycles), the battery performance at low temperature in winter can be significantly improved, and the driving range and safety can be improved. SUMMARY

[0007] Unlike the prior art, the first object of the present invention is to provide a negative electrode binder which, due to its complexing ability with lithium ions, can change the crystallization kinetics characteristics when lithium ions are deposited, allowing lithium ions to be more uniformly deposited on the surface of carbon particles in the negative electrode, thereby inhibiting the generation of lithium dendrites.

[0008] The second object of the present invention is to provide a preparation method of the negative electrode binder.

[0009] The third object of the present invention is to provide a lithium battery negative electrode comprising the negative electrode binder.

[0010] The fourth object of the present invention is to provide a preparation method of the lithium battery negative electrode.

[0011] The fifth object of the present invention is to provide an application of the lithium ion battery negative electrode.

[0012] The present invention is achieved by the following technical solutions:

[0013] A negative electrode binder comprising a copolymer of 1,1-difluoroethylene, epoxy fluoropropane and compound 1;

[0014] The structure of the compound 1 is as follows:

[0015] ;

[0016] wherein 1≤a≤3, 1≤b≤3;

[0017] In the copolymer, the weight ratio of 1,1-difluoroethylene, epoxy fluoropropane and compound 1 is 100:4-6:2-4.

[0018] The preparation method of the compound 1 comprises esterification of 3-amino-4-hydroxybenzoic acid with esterification reaction, and then esterification reaction step; or

[0019] The preparation method of the compound 1 comprises the following steps: mixing 3-amino-4-hydroxybenzoic acid with esterification reaction, and then adding esterification reaction.

[0020] The preparation method of the negative electrode binder comprises the following steps:

[0021] The negative electrode binder is prepared by mixing the epoxy fluoropropane, the compound 1 and the 1,1-difluoroethylene in a solvent, adding an initiator and performing a polymerization reaction.

[0022] The initiator comprises an azo compound;

[0023] The weight ratio of the initiator to the 1,1-difluoroethylene is 1-2:100;

[0024] The azo compound comprises azobisisobutyronitrile;

[0025] The solvent used in the polymerization reaction comprises toluene.

[0026] The temperature of the polymerization reaction is 40-60℃;

[0027] The time of the polymerization reaction is 5-8h.

[0028] A lithium ion battery negative electrode comprises a carbon negative electrode material and the negative electrode binder.

[0029] The negative electrode binder accounts for 2-3wt% of the silicon-carbon negative electrode material;

[0030] The carbon negative electrode material comprises graphite.

[0031] The preparation method of the lithium ion battery negative electrode comprises the following steps: mixing the silicon-carbon negative electrode material and the negative electrode binder in an organic solvent, loading on the surface of a substrate and drying.

[0032] The organic solvent comprises toluene;

[0033] The substrate comprises a copper foil.

[0034] The lithium ion battery negative electrode is applied to the preparation of a lithium ion battery.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] The present application provides a negative electrode binder, which can change the crystallization kinetics characteristics of lithium ion deposition due to the presence of multiple different groups having complexing ability with lithium ions. Moreover, the groups having complexing ability can form a large number of crystallization sites for lithium ions, so that lithium ions can be more uniformly deposited on the surface of carbon particles of the negative electrode, thereby inhibiting the generation of lithium dendrites. Moreover, the negative electrode binder provided by the present application can alleviate the interfacial reaction between the electrolyte and the already formed lithium metal due to its ability to competitively complex lithium ions with the electrolyte, thereby inhibiting the growth of lithium dendrites on the surface of the lithium metal, and thus improving the cycle stability and safety performance of the carbon negative electrode.

[0037] The preparation method of the negative electrode binder provided by the present application is simple and controllable, which can improve the safety of the lithium ion battery negative electrode, thereby reducing the use cost.

[0038] The negative electrode binder provided by the present application helps to induce uniform deposition of lithium extracted from the graphite negative electrode, thereby inhibiting the extraction of lithium dendrites from the graphite, and thus the safety and life of the negative electrode of the lithium ion battery prepared by using the negative electrode binder provided by the present application are improved.

[0039] The lithium ion battery provided by the present application has high safety and long life due to the difficulty of lithium ion dendrite formation in the negative electrode of the lithium ion battery during the charging and discharging reaction. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The SEM image of the lithium deposition of the graphite negative electrode prepared in Example 11 under the condition of 2C is shown, and it can be seen from the figure that no obvious lithium dendrites are observed in the negative electrode material;

[0041] Figure 2 The SEM image of the lithium deposition of the graphite negative electrode prepared in Example 11 under the condition of 2C is shown, and it can be seen from the figure that no obvious lithium dendrites are observed in the negative electrode material;

[0042] Figure 3 The SEM image of the lithium deposition of the graphite negative electrode prepared in Example 11 under the condition of 2C is shown, and it can be seen from the figure that no obvious lithium dendrites are observed in the negative electrode material;

[0043] Figure 4 The SEM image of the lithium deposition of the graphite negative electrode prepared in Example 11 under the condition of 2C is shown, and it can be seen from the figure that no obvious lithium dendrites are observed in the negative electrode material;

[0044] Figure 5 The nuclear magnetic spectrum of the compound 1 prepared in Example 1 is shown;

[0045] Figure 6A graph showing the long cycle performance of a soft pack battery using the graphite negative electrode prepared in Example 11 at 2C constant current charge and discharge is shown;

[0046] Figure 7 A graph showing the long cycle performance of a soft pack battery using the graphite negative electrode prepared in Comparative Example 3 at 2C constant current charge and discharge is shown;

[0047] Figure 8 A graph showing the long cycle performance of a soft pack battery using the graphite negative electrode prepared in Comparative Example 4 at 2C constant current charge and discharge is shown. DETAILED DESCRIPTION

[0048] The present application provides a negative electrode binder comprising a copolymer of 1,1-difluoroethylene, epoxy fluoropropane and compound 1;

[0049] The structure of the compound 1 is as follows:

[0050] ;

[0051] Wherein, 1≤a≤3, 1≤b≤3;

[0052] The weight ratio of 1,1-difluoroethylene, epoxy fluoropropane and compound 1 in the copolymer is 100:4-6:2-4. The reason for copolymerizing 1,1-difluoroethylene, epoxy fluoropropane and compound 1 is to introduce multiple complexing sites for lithium ions. Since the binder is uniformly coated on the surface of the carbon material particles, the more complexing sites in the binder, the greater the difference in the nature of the complexing sites, which can make the lithium ions more evenly distributed on the surface of the carbon material particles. At this time, when the lithium ions are reduced to metallic lithium, they will crystallize more uniformly due to the induction of the complexing groups, rather than forming dendrites. Moreover, the complexing sites can compete with electrolyte molecules to complex lithium ions, thereby reducing the co-intercalation of electrolyte lithium ions into graphite. The presence of multiple double bonds in compound 1 can improve the cross-linking degree of the binder, thereby improving the rigidity of the negative electrode obtained by binding graphite with the binder. The ester group, ether and halogen can form hydrogen bonds with the polar groups on the surface of the adherend, thereby enhancing the interaction force between the binder and the adherend and improving the bonding strength. The introduction of the ether group can improve the polarity and intermolecular forces of the binder, so that the binder can better infiltrate the surface of the adherend and form a more secure bond. In addition, fluorine can also improve the chemical stability and heat resistance of the binder, further enhancing the durability and reliability of the binder.

[0053] Specifically, the preparation method of the compound 1 can be obtained by successively subjecting 3-amino-4-hydroxybenzoic acid to esterification reactions with and Obviously, the order of the reactions is not sequential.

[0054] Specifically, the epoxy fluoropropane, compound 1 and 1,1-difluoroethylene are mixed in a solvent, then an initiator is added, and a polymerization reaction is carried out to obtain the negative electrode binder. The initiator includes azo compounds; it can also be peroxide. The weight ratio of the initiator to 1,1-difluoroethylene is 1-2:100; the azo compounds include azobisisobutyronitrile, azobisisoheptyl nitrile and the like. The solvent used in the polymerization reaction includes toluene; it can also be other organic solvents that can dissolve the above raw materials. The temperature of the polymerization reaction is 40-60°C; it can also be a temperature close to the above temperature. The time of the polymerization reaction is 5-8h. The reaction time can be appropriately adjusted according to the reaction state.

[0055] The application further provides a lithium ion battery negative electrode including a carbon negative electrode material and the negative electrode binder. The negative electrode binder accounts for 2-3wt% of the silicon-carbon negative electrode material; the content can also be appropriately increased or decreased. The carbon negative electrode material includes graphite. The graphite can be artificial graphite and various types of graphite.

[0056] The application further provides a preparation method of the lithium ion battery negative electrode, which specifically includes the steps of mixing the silicon-carbon negative electrode material and the negative electrode binder in an organic solvent, loading on the surface of a substrate and drying. The organic solvent includes toluene; it can also be other organic solvents. The substrate can be a copper foil.

[0057] The application further provides an application of the lithium ion battery negative electrode, which is specifically applied to the preparation of a lithium ion battery.

[0058] Example 1

[0059] Compound 1 is prepared by Steglich esterification reaction, wherein a=1 and b=1

[0060] In a 50mL round-bottom flask, 1mol 3-aminophenyl-4-hydroxybenzoic acid, 1mol , 1.5mol DCC and 0.5mol DMAP are sequentially added, then dichloromethane is added under the protection of N2, and the reaction is carried out at room temperature for about 6h (TLC detection), then the filter cake is filtered, washed with petroleum ether, ethyl acetate and acetone in sequence, and dried to obtain .

[0061] In a 50mL round-bottom flask, 1mol , 1mol , 1.5mol DCC and 0.5mol DMAP are sequentially added, then dichloromethane is added under the protection of N2, and the reaction is carried out at room temperature for about 6h (TLC detection), then the filter cake is filtered, washed with petroleum ether, ethyl acetate and acetone in sequence, and dried to obtain The above reaction sequence can be reversed.

[0062] The spectral data of the compound are as follows:

[0063] 1H NMR (300 MHz, CD3CN, δ, ppm):

[0064] 7.40-7.11 (3H in benzene), 5.82 (2H in ethylene), 5.27(2H in amine),5.13(2H in ethylene), 4.88 (2H in ethylene), 4.29 (2H in methylene), 2.58-2.35(6H in methylene).

[0065] Example 2

[0066] The Steglich esterification reaction was used to prepare compound 1, wherein a = 2 and b = 2.

[0067] In a 50 mL round-bottom flask, 1 mol of 3-amin-4-hydroxybenzoic acid, 1 mol of , 1.5 mol of DCC and 0.5 mol of DMAP were sequentially added, then dichloromethane was added under the protection of N2, and the reaction was carried out at room temperature for about 6 h (TLC detection). After filtration, the filter cake was sequentially washed with petroleum ether, ethyl acetate and acetone, and then dried to obtain .

[0068] In a 50 mL round-bottom flask, 1 mol of , 1 mol of , 1.5 mol of DCC and 0.5 mol of DMAP were sequentially added, then dichloromethane was added under the protection of N2, and the reaction was carried out at room temperature for about 6 h (TLC detection). After filtration, the filter cake was sequentially washed with petroleum ether, ethyl acetate and acetone, and then dried to obtain . The above reaction sequence can be reversed.

[0069] Example 3

[0070] The Steglich esterification reaction was used to prepare compound 1, wherein a = 3 and b = 3.

[0071] In a 50 mL round-bottom flask, 1 mol of 3-amin-4-hydroxybenzoic acid, 1 mol of , 1.5 mol of DCC and 0.5 mol of DMAP were sequentially added, then dichloromethane was added under the protection of N2, and the reaction was carried out at room temperature for about 6 h (TLC detection). After filtration, the filter cake was sequentially washed with petroleum ether, ethyl acetate and acetone, and then dried to obtain .

[0072] Add 1 mol of [unspecified substance] to a 50 mL round-bottom flask. 1 mol 1.5 mol DCC and 0.5 mol DMAP were added, followed by the addition of dichloromethane under N2 protection. The reaction was carried out at room temperature for approximately 6 hours (TLC monitoring). The mixture was then filtered, and the filter cake was washed successively with petroleum ether, ethyl acetate, and acetone, and then dried to obtain the final product. The order of the above reactions can be reversed.

[0073] Example 4

[0074] Compound 1 was prepared by Steglich esterification, where a=2 and b=3.

[0075] In a 50 mL round-bottom flask, add 1 mol of 3-amino-4-hydroxybenzoic acid and 1 mol of... 1.5 mol DCC and 0.5 mol DMAP were added, followed by dichloromethane under N2 protection. The reaction was carried out at room temperature for about 6 hours (TLC monitoring). The mixture was then filtered, and the filter cake was washed successively with petroleum ether, ethyl acetate, and acetone, and then dried to obtain... .

[0076] Add 1 mol of [agent] to a 50 mL round-bottom flask. 1 mol 1.5 mol DCC and 0.5 mol DMAP were added, followed by the addition of dichloromethane under N2 protection. The reaction was carried out at room temperature for approximately 6 hours (TLC monitoring). The mixture was then filtered, and the filter cake was washed successively with petroleum ether, ethyl acetate, and acetone, and then dried to obtain the final product. The order of the above reactions can be reversed.

[0077] Example 5

[0078] Compound 1 was prepared by Steglich esterification, where a=3 and b=1.

[0079] In a 50 mL round-bottom flask, add 1 mol of 3-amino-4-hydroxybenzoic acid and 1 mol of... 1.5 mol DCC and 0.5 mol DMAP were added, followed by dichloromethane under N2 protection. The reaction was carried out at room temperature for about 6 hours (TLC monitoring). The mixture was then filtered, and the filter cake was washed successively with petroleum ether, ethyl acetate, and acetone, and then dried to obtain... .

[0080] Add 1 mol of [agent] to a 50 mL round-bottom flask. 1 mol , 1.5 mol DCC and 0.5 mol DMAP, then dichloromethane was added under the protection of N2, and the reaction was carried out at room temperature for about 6 h (TLC detection), and then the filter cake was washed with petroleum ether, ethyl acetate and acetone in sequence and dried to obtain The above reaction sequence can be reversed.

[0081] Example 6

[0082] Preparation of a negative electrode binder

[0083] In a vertical polymerization kettle, 20 g of the compound 1 prepared in Example 1, 40 g of epoxy fluoropropane and 5 kg of toluene were added. The kettle was closed and replaced with nitrogen several times to remove air until the oxygen content in the kettle was less than 10 ppm. 1000 g of 1,1-difluoroethylene and 100 g of azobisisobutyronitrile were injected. The kettle was heated to 45°C, and the stirring speed was 800 r / min. After 6 h of reaction, the kettle was depressurized, and the liquid was collected and finally dried in a 95°C oven for 24 h to obtain the negative electrode binder.

[0084] Example 7

[0085] Preparation of a negative electrode binder

[0086] The difference from Example 6 is that 30 g of the compound prepared in Example 2, 40 g of epoxy fluoropropane and 5 kg of toluene were added.

[0087] Example 8

[0088] Preparation of a lithium ion battery negative electrode binder

[0089] The difference from Example 6 is that 30 g of the compound prepared in Example 3, 50 g of epoxy fluoropropane and 5 kg of toluene were added.

[0090] Example 9

[0091] Preparation of a lithium ion battery negative electrode binder

[0092] The difference from Example 6 is that 30 g of the compound prepared in Example 4, 60 g of epoxy fluoropropane and 5 kg of toluene were added.

[0093] Example 10

[0094] Preparation of a lithium ion battery negative electrode binder

[0095] The difference from Example 6 is that 40 g of the compound prepared in Example 5, 60 g of epoxy fluoropropane and 5 kg of toluene were added.

[0096] Comparative Example 1

[0097] Preparation of negative electrode binder (without adding epoxy fluoropropane and compound 1)

[0098] In a vertical polymerization kettle, 5 kg of toluene was added. The kettle was closed and purged with nitrogen several times to remove air until the oxygen content in the kettle was less than 10 ppm. 1000 g of 1,1-difluoroethylene was injected and 100 g of azobisisobutyronitrile was added. The kettle was heated to 45°C, the stirring of the kettle was started at a speed of 800 r / min, and after 6 h of reaction, the kettle was depressurized, the liquid was collected, and finally dried in an oven at 95°C for 24 h to obtain the negative electrode binder.

[0099] Comparative Example 2

[0100] Preparation of negative electrode binder (without adding compound 1)

[0101] In a vertical polymerization kettle, 40 g of epoxy fluoropropane and 5 kg of toluene were added. The kettle was closed and purged with nitrogen several times to remove air until the oxygen content in the kettle was less than 10 ppm. 1000 g of 1,1-difluoroethylene was injected and 100 g of azobisisobutyronitrile was added. The kettle was heated to 45°C, the stirring of the kettle was started at a speed of 800 r / min, and after 6 h of reaction, the kettle was depressurized, the liquid was collected, and finally dried in an oven at 95°C for 24 h to obtain the negative electrode binder.

[0102] Example 11

[0103] Preparation of negative electrode

[0104] A first graphite material with a D50 of 2.0 microns and a second graphite material with a D50 of 4.5 microns were mixed at a mass ratio of 100:25, placed in a high-speed ball mill, the ball-to-material ratio of the high-speed ball mill was 3:1, the rotation speed was 180 r / min, and the ball milling time was 10 h to obtain the negative electrode material.

[0105] The ball milling time was 10 h to obtain the negative electrode material.

[0106] The binder prepared in Example 6 was added to the solvent in a stirred kettle, stirred uniformly, and then the electrode material was added and stirred uniformly to obtain the negative electrode slurry, wherein the binder accounted for 2 wt% of the graphite powder.

[0107] The negative electrode slurry was coated on the surface of a copper foil with a coating thickness of 75 microns, dried, and a graphite negative electrode was obtained.

[0108] Example 12

[0109] Preparation of negative electrode

[0110] A first graphite material with a D50 of 2.0 microns and a second graphite material with a D50 of 4.5 microns were mixed in a mass ratio of 100:25, and placed in a high-speed ball mill, the ball-to-material ratio of the high-speed ball mill was 3:1, the rotation speed was 180 revolutions per minute,

[0111] The ball milling time was 10 h, and the negative electrode material was obtained.

[0112] In a stirred tank, toluene was added, the binder prepared in Example 7 was added to the solvent, stirred uniformly, then the electrode material was added, stirred uniformly, and a negative electrode slurry was obtained, wherein the ratio of the binder to the graphite powder was 3wt%.

[0113] The negative electrode slurry was coated on the surface of a copper foil, the coating thickness was 75 microns, and the graphite negative electrode was obtained after drying.

[0114] Example 13

[0115] Preparation of the negative electrode

[0116] The difference from Example 11 is that the binder used was prepared in Example 8.

[0117] Example 14

[0118] Preparation of the negative electrode

[0119] The difference from Example 11 is that the binder used was prepared in Example 9.

[0120] Example 15

[0121] Preparation of the negative electrode

[0122] The difference from Example 11 is that the binder used was prepared in Example 10.

[0123] Comparative Example 3

[0124] Preparation of the negative electrode

[0125] The difference from Example 11 is that the binder used was prepared in Comparative Example 1.

[0126] Comparative Example 4

[0127] Preparation of the negative electrode

[0128] The difference from Example 11 is that the binder used was prepared in Comparative Example 2.

[0129] Cycle capacity retention rate test of the battery

[0130] The graphite negative electrode and lithium sheet were used to form an experimental battery, and the battery was subjected to 1000 cycles of charge and discharge at a current of 2C, and the cycle capacity retention rate of the battery was measured.

[0131] The cycle capacity retention rate of the battery prepared by using the lithium ion battery negative electrode prepared in Example 11 was 88.05%. The cycle capacity retention rate of the battery prepared by using the lithium ion battery negative electrode prepared in Example 12 was 87.10%. The cycle capacity retention rate of the battery prepared by using the lithium ion battery negative electrode prepared in Example 13 was 85.66%. The cycle capacity retention rate of the battery prepared by using the lithium ion battery negative electrode prepared in Example 14 was 87.60%. The cycle capacity retention rate of the battery prepared by using the lithium ion battery negative electrode prepared in Example 15 was 86.88%. The cycle capacity retention rate of the battery prepared by using the lithium ion battery negative electrode prepared in Comparative Example 3 was 74.35%. The cycle capacity retention rate of the battery prepared by using the lithium ion battery negative electrode prepared in Comparative Example 4 was 80.33%.

[0132] Although the present application has been described in detail by the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present application.

Claims

1.A negative electrode binder, characterized in that: a copolymer comprising 1, 1-difluoroethylene, epoxy fluoro propane and compound 1; the structure of the compound 1 is as follows: wherein, 1≤a≤3, 1≤b≤3; and the weight ratio of 1, 1-difluoroethylene, epoxy fluoro propane and compound 1 in the copolymer is 100: 4-6: 2-4. 2.The negative electrode binder of claim 1, characterized in that: 3.A preparation method of the negative electrode binder of claim 1, characterized in that: comprising the following steps: mixing epoxy fluoro propane, compound 1 and 1, 1-difluoroethylene in a solvent, adding an initiator, and performing a polymerization reaction to obtain the negative electrode binder. ； 4.The preparation method of the negative electrode binder of claim 3, characterized in that: the initiator comprises an azo compound; the azo compound comprises azobisisobutyronitrile; and the solvent used in the polymerization reaction comprises toluene. 5.The preparation method of the negative electrode binder of claim 3, characterized in that: the temperature of the polymerization reaction is 40-60℃; and the time of the polymerization reaction is 5-8h. 6.A lithium ion battery negative electrode, characterized in that: comprising a carbon negative electrode material and the negative electrode binder of claim 1. The preparation method of the compound 1 comprises reacting 3-amino-4-hydroxybenzoic acid with esterification reaction, and then reacting with esterification reaction; or The preparation method of the compound 1 includes reacting 3-amino-4-hydroxybenzoic acid with esterification reaction, and then reacting with esterification reaction. 7.The lithium ion battery negative electrode of claim 6, characterized in that: the negative electrode binder accounts for 2-3wt% of the carbon negative electrode material; and the carbon negative electrode material comprises graphite. 8.A preparation method of the lithium ion battery negative electrode of claim 6, characterized in that: comprising the steps of mixing the carbon negative electrode material and the negative electrode binder in an organic solvent, loading on the surface of a substrate and drying. 9.The preparation method of the lithium ion battery negative electrode of claim 8, characterized in that: the organic solvent comprises toluene; and the substrate comprises a copper foil. 10.The application of the lithium ion battery negative electrode of claim 6, characterized in that: being applied to prepare a lithium ion battery. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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