Modified graphite and its preparation method, secondary batteries, battery modules, battery packs, and electrical devices.

Abstract

This application provides a modified graphite and its preparation method, as well as a secondary battery, battery module, battery pack, and electrical device including the modified graphite. Specifically, the modified graphite of this application comprises a graphite portion and a binder portion covalently bonded to the graphite portion, the binder portion having a structure of formula (IV'). The modified graphite of this application solves the problem of binder floating during the preparation of the negative electrode sheet of a secondary battery.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a modified graphite and its preparation method, as well as to secondary batteries, battery modules, battery packs and electrical devices. Background Technology

[0002] In recent years, rechargeable batteries have been widely used in many fields. Currently, styrene-butadiene rubber (SBR) is often used as the negative electrode binder in rechargeable batteries. However, uneven binder distribution is prone to occur in the negative electrode sheets prepared by this method, leading to deterioration of battery performance. In existing technologies, the above problems are often improved by adjusting the coating and drying processes, but neither can completely eliminate the aforementioned issues.

[0003] Therefore, it is necessary to address the problem of battery performance degradation caused by uneven distribution of binder on the negative electrode of secondary batteries. Summary of the Invention

[0004] The technical problem that the invention aims to solve

[0005] This application is made in view of the above-mentioned issues and aims to improve the uneven distribution of binder, especially to reduce the floating of negative electrode binder (especially SBR binder) without reducing production efficiency, thereby improving battery performance.

[0006] Technical solutions for solving the problem

[0007] To achieve the above objectives, this application provides modified graphite and its preparation method.

[0008] A first aspect of this application provides a modified graphite, wherein the modified graphite comprises a graphite portion and a binder portion covalently linked to the graphite portion, the binder portion having a structure of formula (IV'):

[0009]

[0010] in,

[0011] R 1 -R 6 Each is independently selected from hydrogen, halogen, cyano, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 2-6 alkenyl, unsubstituted or substituted C 6-20 aryl, wherein the substituents in the alkyl, alkoxy, alkenyl and aryl groups are selected from C 1-3 At least one of alkyl, hydroxyl, amino, amide, cyano, carboxyl, and halogen groups; optionally R 1 -R6 Each is independently selected from hydrogen, halogen, and unsubstituted C. 1-6 Alkyl, unsubstituted or substituted C 6-20 Aryl; wherein the substituent in the aryl group is selected from C 1-3 At least one of alkyl groups and halogens;

[0012] R 7 -R 9 Each is independently selected from hydrogen, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 1-6 Alkylamino, unsubstituted or substituted C 2-6 Alkenyl and unsubstituted or substituted C 6-20 The aryl group, wherein the substituents in the alkyl, alkoxy, alkylamino, alkenyl, and aryl groups are selected from at least one of hydroxyl, carboxyl, amino, amide, and halogen groups; optionally, R 7 -R 9 Each is independently selected from hydrogen, amino, or unsubstituted C. 1-6 Alkyl, unsubstituted C 1-6 At least one of alkylamino groups; more preferably, R 7 -R 8 Each is independently selected from at least one of hydrogen, methyl, ethyl, dimethylamino, and 2-(N,N-diethylamino)ethyl, and R 9 Selected from at least one of hydrogen, methyl, and ethyl;

[0013] R 10 C represents a straight chain or a branched chain. 1-12 Alkyl groups, optionally straight-chain or branched C4 groups 1-6 Alkyl, and more preferably methyl,

[0014] R 11 It indicates a halogen or a cyano group, optionally a cyano group.

[0015] Z is selected from straight-chain or branched C1-C5 alkylthio groups, optionally including methylthio, ethylthio, propylthio, butylthio, and pentthio.

[0016] L represents C, which is either a straight chain or a branched chain. 1-12 Alkylene, optionally straight-chain or branched C 1-6 The alkylene group, more preferably methylene,

[0017] R 13a This indicates #-COO-*, #-CH2O-*, or #-NH-*, where # indicates the position connected to L, and * indicates the position connected to the graphite portion;

[0018] The ratio of m / n is 1-100, optionally 1-50, and more preferably 1-13.

[0019] In this application, the modified graphite includes a graphite portion and a binder portion covalently linked to the graphite portion. By attaching binder fragments containing special functional groups to the surface of the graphite particles, the dispersibility of the graphite particles in the slurry can be improved, which is beneficial to improving the problem of binder floating in the subsequent preparation of the negative electrode sheet, thereby effectively improving the conductivity and adhesion of the film layer in the negative electrode sheet.

[0020] In any implementation, m is an integer between 500 and 15000, and n is an integer between 500 and 15000.

[0021] In any embodiment, the number average molecular weight (Mn) of the binder portion of formula (IV') is 30,000-3,000,000, optionally 50,000-2,000,000, and more preferably 300,000-1,000,000.

[0022] In any embodiment, the structural unit in the adhesive portion Copolymerization can be carried out in random, block and / or alternating manners, with block copolymerization being an option.

[0023] In any embodiment, the binder portion of the modified graphite is selected from the following structures:

[0024]

[0025] The asterisk (*) indicates the location where the binder portion is covalently connected to the graphite portion.

[0026] In any embodiment, the mass ratio of the graphite portion to the binder portion is 85:12-96.5:0.5, optionally 90:7-96:1. By controlling the mass ratio of the graphite portion to the binder portion within the above range, the active material content of the electrode containing modified graphite can be moderate to provide appropriate battery energy density, and good adhesion can be provided.

[0027] A second aspect of this application provides a method for preparing modified graphite, comprising the following steps:

[0028] The binder compound was reacted with graphite in a solvent in the presence of a catalyst.

[0029] The binder compound has the structure of formula (IV):

[0030]

[0031] in,

[0032] R 1 -R 6 Each is independently selected from hydrogen, halogen, cyano, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 2-6 alkenyl, unsubstituted or substituted C 6-20 aryl, wherein the substituents in the alkyl, alkoxy, alkenyl and aryl groups are selected from C 1-3 At least one of alkyl, hydroxyl, amino, amide, cyano, carboxyl, and halogen groups; optionally R 1 -R 6 Each is independently selected from hydrogen, halogen, and unsubstituted C. 1-6 Alkyl, unsubstituted or substituted C 6-20 Aryl; wherein the substituent in the aryl group is selected from C 1-3 At least one of alkyl groups and halogens;

[0033] R 7 -R 9 Each is independently selected from hydrogen, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 1-6 Alkylamino, unsubstituted or substituted C 2-6 Alkenyl and unsubstituted or substituted C 6-20 The aryl group, wherein the substituents in the alkyl, alkoxy, alkylamino, alkenyl, and aryl groups are selected from at least one of hydroxyl, carboxyl, amino, amide, and halogen groups; optionally, R 7 -R 9 Each is independently selected from hydrogen, amino, or unsubstituted C. 1-6 Alkyl, unsubstituted C 1-6 At least one of alkylamino groups; more preferably, R 7 -R 8 Each is independently selected from at least one of hydrogen, methyl, ethyl, dimethylamino, and 2-(N,N-diethylamino)ethyl, and R 9 Selected from at least one of hydrogen, methyl, and ethyl;

[0034] R 10 C represents a straight chain or a branched chain. 1-12 Alkyl groups, optionally straight-chain or branched C4 groups 1-6 Alkyl, and more preferably methyl,

[0035] R 11It indicates a halogen or a cyano group, optionally a cyano group.

[0036] Z is selected from straight-chain or branched C1-C5 alkylthio groups, optionally including methylthio, ethylthio, propylthio, butylthio, and pentthio.

[0037] L represents C, which is either a straight chain or a branched chain. 1-12 Alkylene, optionally straight-chain or branched C 1-6 The alkylene group, more preferably methylene,

[0038] R 13 Indicates carboxyl, hydroxymethyl, or amino groups;

[0039] The ratio of m / n is 1-100, optionally 1-50, and more preferably 1-13.

[0040] In this application, graphite particles are chemically reacted with a binder compound containing special functional groups in a solvent in the presence of a catalyst. This achieves surface modification of the graphite, resulting in the binder portion being stably bonded to the surface of the graphite particles.

[0041] In any embodiment, in the adhesive compound, m is an integer from 500 to 15000, and n is an integer from 500 to 15000.

[0042] In any embodiment, the number average molecular weight of the adhesive compound is 30,000-3,000,000, optionally 50,000-2,000,000, and more preferably 300,000-1,000,000.

[0043] In any embodiment, the structural unit of the adhesive compound Copolymerization can be carried out in random, block and / or alternating manners, with block copolymerization being an option.

[0044] In any embodiment, the adhesive compound is selected from at least one of the following:

[0045]

[0046]

[0047] In any embodiment, the pH of the reaction is 4-7; optionally, it is 4.5-6. Controlling the reaction pH within the above range allows for an appropriate reaction rate and enables the reaction to proceed smoothly.

[0048] In any embodiment, the mass ratio of the graphite to the binder compound is 85:12-96.5:0.5, and optionally 90:7-96:1.

[0049] In any embodiment, the reaction is carried out at 20°C-40°C, optionally at 25°C-30°C.

[0050] A third aspect of this application provides a negative electrode sheet, wherein the negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, the negative electrode material layer comprising modified graphite of the first aspect of this application or modified graphite prepared according to the method of preparing modified graphite of the second aspect.

[0051] A fourth aspect of this application provides a secondary battery, the secondary battery comprising the negative electrode sheet described in the third aspect above.

[0052] The fifth aspect of this application provides a battery module that includes the secondary battery described in the fourth aspect above.

[0053] A sixth aspect of this application provides a battery pack that includes at least one of the secondary battery of the fourth aspect or the battery module of the fifth aspect.

[0054] A seventh aspect of this application provides an electrical device comprising at least one selected from the fourth aspect, the fifth aspect, or the sixth aspect.

[0055] Invention Effects

[0056] Compared with the prior art, the modified graphite of this application has achieved at least the following beneficial effects: it fundamentally solves the problem of binder (such as SBR) migrating and floating to the surface of the negative electrode sheet during the drying process, so that the binder in the electrode sheet is evenly distributed, which improves the adhesion of the negative electrode sheet film and improves the storage and cycle performance of the battery. Attached Figure Description

[0057] Figure 1 The image shows the infrared spectrum of the binder compound prepared in Example 1.

[0058] Figure 2 The infrared spectrum of the modified graphite prepared in Example 1.

[0059] Figure 3 The infrared spectrum of the modified graphite prepared in Example 2.

[0060] Figure 4 The infrared spectrum of the modified graphite prepared in Example 3.

[0061] Figure 5 The images show X-ray microscopic analysis of the negative electrode plates in Example 1 and the comparative example.

[0062] Figure 6 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0063] Figure 7 This is an exploded view of a secondary battery according to one embodiment of this application.

[0064] Figure 8 This is a schematic diagram of a battery module according to one embodiment of this application.

[0065] Figure 9 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0066] Figure 10 This is an exploded view of a battery pack according to one embodiment of this application.

[0067] Figure 11 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0068] Explanation of reference numerals in the attached figures:

[0069] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly Detailed Implementation

[0070] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the binder compound preparation method and the prepared binder compound, modified graphite and its preparation method, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a thorough understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0071] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0072] Currently, styrene-butadiene rubber (SBR) is commonly used as the negative electrode binder in secondary batteries. However, during the coating and drying process of the negative electrode material layer, the SBR binder is prone to migration to the electrode surface as the solvent evaporates (i.e., binder floats). This results in uneven binder distribution in the negative electrode sheet—the binder concentration near the current collector is relatively low. This leads to insufficient adhesion between the active material (graphite) layer and the current collector in the negative electrode sheet, and may even cause the active material layer to peel off from the current collector, thus preventing the formation of a good electronic pathway, resulting in deteriorated battery performance and a significant decrease in battery capacity.

[0073] In existing technologies, the problem of binder flotation is usually improved by adjusting the coating and drying processes of the electrode material—such as reducing the drying speed, extending the drying distance, or using multi-stage drying. However, the inventors have found that these measures can only slightly improve the problem, but cannot significantly improve or even prevent binder flotation; at the same time, these measures will greatly reduce production efficiency and increase equipment investment, making them unsuitable for mass production.

[0074] In view of the above problems, this application provides a modified graphite, which is chemically bonded to the graphite surface by a binder compound containing special functional groups. Thus, in the preparation process of negative electrode slurry, there is no need to add free negative electrode binder, which improves the dispersibility of graphite in the slurry and solves the problem of binder floating in secondary battery negative electrode from the source. This improves the film adhesion of negative electrode sheet and effectively improves the storage and cycle performance of battery.

[0075] Modified graphite

[0076] A first aspect of this application provides a modified graphite, wherein the modified graphite comprises a graphite portion and a binder portion covalently linked to the graphite portion, the binder portion having a structure of formula (IV'):

[0077]

[0078] in,

[0079] R 1 -R 6 Each is independently selected from hydrogen, halogen, cyano, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 2-6 alkenyl, unsubstituted or substituted C 6-20 aryl, wherein the substituents in the alkyl, alkoxy, alkenyl and aryl groups are selected from C 1-3 At least one of alkyl, hydroxyl, amino, amide, cyano, carboxyl, and halogen groups; optionally R1 -R 6 Each is independently selected from hydrogen, halogen, and unsubstituted C. 1-6 Alkyl, unsubstituted or substituted C 6-20 Aryl; wherein the substituent in the aryl group is selected from C 1-3 At least one of alkyl groups and halogens;

[0080] R 7 -R 9 Each is independently selected from hydrogen, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 1-6 Alkylamino, unsubstituted or substituted C 2-6 Alkenyl and unsubstituted or substituted C 6-20 The aryl group, wherein the substituents in the alkyl, alkoxy, alkylamino, alkenyl, and aryl groups are selected from at least one of hydroxyl, carboxyl, amino, amide, and halogen groups; optionally, R 7 -R 9 Each is independently selected from hydrogen, amino, or unsubstituted C. 1-6 Alkyl, unsubstituted C 1-6 At least one of alkylamino groups; more preferably, R 7 -R 8 Each is independently selected from at least one of hydrogen, methyl, ethyl, dimethylamino, and 2-(N,N-diethylamino)ethyl, and R 9 Selected from at least one of hydrogen, methyl, and ethyl;

[0081] R 10 C represents a straight chain or a branched chain. 1-12 Alkyl groups, optionally straight-chain or branched C4 groups 1-6 Alkyl, and more preferably methyl,

[0082] R 11 It indicates a halogen or a cyano group, optionally a cyano group.

[0083] Z is selected from straight-chain or branched C1-C5 alkylthio groups, optionally including methylthio, ethylthio, propylthio, butylthio, and pentthio.

[0084] L represents C, which is either a straight chain or a branched chain. 1-12 Alkylene, optionally straight-chain or branched C 1-6 The alkylene group, more preferably methylene,

[0085] R 13aThis indicates #-COO-*, #-CH2O-*, or #-NH-*, where # indicates the position connected to L, and * indicates the position connected to the graphite portion;

[0086] The ratio of m / n is 1-100, optionally 1-50, and more preferably 1-13.

[0087] In this application, the terms “covalent connection” or “covalent bonding” or “connected by covalent bonds” and similar expressions are used interchangeably to mean that atoms, molecules or parts of molecules are connected together by covalent bonds.

[0088] In this application, the modified graphite comprises a graphite portion and a binder portion covalently bonded to the graphite portion, wherein the binder portion contains special functional groups. Because the modified graphite of this application has a binder portion bonded to its surface, there is no need to add free binder during the preparation of the electrode (especially the negative electrode), thus preventing the binder (especially SBR binder) from floating to the surface during the electrode coating and drying process, which could lead to battery performance degradation.

[0089] In some implementations, m is an integer between 500 and 15000, and n is an integer between 500 and 15000.

[0090] In some embodiments, the number average molecular weight of the adhesive portion of formula (IV') is 30,000-3,000,000, optionally 50,000-2,000,000, and more preferably 300,000-1,000,000.

[0091] In some embodiments, the structural units in the adhesive portion Copolymerization can be carried out in random, block and / or alternating manners, with block copolymerization being an option.

[0092] In some embodiments, the binder portion of the modified graphite is selected from the following structures:

[0093]

[0094] The asterisk (*) indicates the location where the binder portion is covalently connected to the graphite portion.

[0095] By selecting the above-mentioned preferred binder components, the modified graphite of this application can further improve battery performance.

[0096] In some embodiments, the mass ratio of the graphite portion to the binder portion in the modified graphite of this application is 85:12-96.5:0.5, optionally 90:7-96:1. By controlling the mass ratio of the graphite portion to the binder portion in the modified graphite within the above range, the active material content of the electrode containing the modified graphite can be moderate to provide an appropriate battery energy density, and good adhesion can be provided.

[0097] In some embodiments, the graphite portion is derived from at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and modified graphite materials thereof.

[0098] Preparation method of modified graphite

[0099] A second aspect of this application provides a method for preparing modified graphite, comprising the steps of: reacting a binder compound with graphite in a solvent in the presence of a catalyst.

[0100] The binder compound has the structure of formula (IV):

[0101]

[0102] in,

[0103] R 1 -R 6 Each is independently selected from hydrogen, halogen, cyano, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 2-6 alkenyl, unsubstituted or substituted C 6-20 aryl, wherein the substituents in the alkyl, alkoxy, alkenyl and aryl groups are selected from C 1-3 At least one of alkyl, hydroxyl, amino, amide, cyano, carboxyl, and halogen groups; optionally R 1 -R 6 Each is independently selected from hydrogen, halogen, and unsubstituted C. 1-6 Alkyl, unsubstituted or substituted C 6-20 Aryl; wherein the substituent in the aryl group is selected from C 1-3 At least one of alkyl groups and halogens;

[0104] R 7 -R 9 Each is independently selected from hydrogen, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 1-6Alkylamino, unsubstituted or substituted C 2-6 Alkenyl and unsubstituted or substituted C 6-20 The aryl group, wherein the substituents in the alkyl, alkoxy, alkylamino, alkenyl, and aryl groups are selected from at least one of hydroxyl, carboxyl, amino, amide, and halogen groups; optionally, R 7 -R 9 Each is independently selected from hydrogen, amino, or unsubstituted C. 1-6 Alkyl, unsubstituted C 1-6 At least one of alkylamino groups; more preferably, R 7 -R 8 Each is independently selected from at least one of hydrogen, methyl, ethyl, dimethylamino, and 2-(N,N-diethylamino)ethyl, and R 9 Selected from at least one of hydrogen, methyl, and ethyl;

[0105] R 10 C represents a straight chain or a branched chain. 1-12 Alkyl groups, optionally straight-chain or branched C4 groups 1-6 Alkyl, and more preferably methyl,

[0106] R 11 It indicates a halogen or a cyano group, optionally a cyano group.

[0107] Z is selected from straight-chain or branched C1-C5 alkylthio groups, optionally including methylthio, ethylthio, propylthio, butylthio, and pentthio.

[0108] L represents C, which is either a straight chain or a branched chain. 1-12 Alkylene, optionally straight-chain or branched C 1-6 The alkylene group, more preferably methylene,

[0109] R 13 Indicates carboxyl, hydroxymethyl, or amino groups;

[0110] The ratio of m / n is 1-100, optionally 1-50, and more preferably 1-13.

[0111] In any embodiment, in the adhesive compound, m is an integer from 500 to 15000, and n is an integer from 500 to 15000.

[0112] In this application, graphite particles are chemically reacted with a binder compound containing special functional groups in a solvent in the presence of a catalyst. This achieves surface modification of the graphite, resulting in the binder portion being stably bonded to the surface of the graphite particles.

[0113] In some embodiments, the number average molecular weight of the adhesive compound is 30,000-3,000,000, optionally 50,000-2,000,000, and more preferably 300,000-1,000,000.

[0114] In some embodiments, the structural units of the adhesive compound Copolymerization can be carried out in random, block and / or alternating manners, with block copolymerization being an option.

[0115] In some embodiments, the adhesive compound is selected from at least one of the following:

[0116]

[0117] In some embodiments, the pH of the above reaction is 4-7; optionally, it is 4.5-6. The inventors have found that controlling the reaction pH within the above range allows for an appropriate reaction rate and enables the reaction to proceed smoothly.

[0118] In some embodiments, the mass ratio of graphite to binder compound in the graphite modification method is 85:12 to 96.5:0.5, and optionally 90:7 to 96:1.

[0119] In some embodiments, the catalyst is pyridine. In some embodiments, the solvent is at least one selected from dichloromethane, tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide. In some embodiments, the reaction is carried out at 20°C-40°C, optionally at 25°C-30°C.

[0120] In some embodiments, in the preparation method of the second aspect of this application, the reaction between graphite and binder compound is carried out for 2-4 hours, optionally for 2 hours.

[0121] In some embodiments, the preparation method of the second aspect of this application can use any graphite with a surface having reactive groups to carboxyl, hydroxyl or amino groups.

[0122] In some embodiments, the graphite includes, but is not limited to, at least one of artificial graphite, natural graphite, soft carbon, hard carbon, and modified graphite materials thereof.

[0123] Methods for preparing binder compounds

[0124] This application also proposes a method for preparing an adhesive compound, which includes the following steps:

[0125] (i) Reacting the compound of formula (I), the compound of formula (II), and the chain transfer agent of formula (III) in a solvent in the presence of an initiator;

[0126] The compound of formula (I) is:

[0127]

[0128] Among them, R 1 -R 6 Each is independently selected from hydrogen, halogen, cyano, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 2-6 alkenyl, unsubstituted or substituted C 6-20 aryl, wherein the substituents in the alkyl, alkoxy, alkenyl and aryl groups are selected from C 1-3 At least one of alkyl, hydroxyl, amino, amide, cyano, carboxyl, and halogen groups;

[0129] The compound of formula (II) is:

[0130]

[0131] Among them, R 7 -R 9 Each is independently selected from hydrogen, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 1-6 Alkylamino, unsubstituted or substituted C 2-6 Alkenyl and unsubstituted or substituted C 6-20 The aryl group, wherein the substituents in the alkyl, alkoxy, alkylamino, alkenyl and aryl groups are selected from at least one of hydroxyl, carboxyl, amino, amide, and halogen groups;

[0132] The chain transfer agent in formula (III) is:

[0133]

[0134] in,

[0135] Z is selected from straight-chain or branched C1-C5 alkylthio groups, optionally including methylthio, ethylthio, propylthio, butylthio, and pentthio.

[0136] R 10 C represents a straight chain or a branched chain. 1-12 Alkyl groups, optionally straight-chain or branched C4 groups 1-6 Alkyl groups, optionally methyl,

[0137] R 11 It indicates a halogen or a cyano group, optionally a cyano group.

[0138] L represents C, which is either a straight chain or a branched chain. 1-12 Alkylene, optionally straight-chain or branched C 1-6 The alkylene group, more preferably methylene,

[0139] R 12 Selected from carboxyl groups.

[0140] The applicant has discovered that the binder compound prepared by the above preparation method has reactive groups at its ends, which can bind to the graphite surface to modify the graphite, thereby improving the problem of the binder floating during the coating and drying process of the negative electrode sheet, improving the uniformity of the binder distribution in the negative electrode material layer, improving the electrode sheet adhesion, and improving battery performance.

[0141] In some embodiments, the solvent in step (i) can be any organic solvent capable of being used in such reactions. In some embodiments, the solvent in step (i) is selected from tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide, and optionally tetrahydrofuran.

[0142] In some embodiments, the initiator in step (i) can be any initiator capable of being used for such reactions. In some embodiments, the initiator in step (i) is selected from azobisisobutyronitrile (AIBN), benzoyl peroxide, and more preferably AIBN.

[0143] In some embodiments, step (i) is carried out under anaerobic conditions. In some embodiments, optionally, it is carried out in an inert gas atmosphere. In some embodiments, optionally, it is carried out in a nitrogen atmosphere. Adding the initiator and carrying out the reaction under anaerobic conditions can prevent the oxidation of free radicals generated during the reaction, thereby inhibiting the production of byproducts.

[0144] In some embodiments, step (i) is performed at 60-80°C, optionally 65-75°C, and more preferably 70°C. Controlling the temperature within this range allows for control of the polymerization rate while ensuring the polymer has an appropriate molecular weight.

[0145] In some embodiments, the reaction time of step (i) is conventionally determined by those skilled in the art. In some embodiments, the reaction in step (i) is carried out for 8-12 hours, optionally for 12 hours.

[0146] In some embodiments, in step (i), the ratio between the total mass of the compounds of formula (I) and formula (II) and the mass of the chain transfer agent of formula (III) is from 10:1 to 5000:1, optionally from 10:1 to 100:1, and more preferably from 15:1 to 80:1. The inventors have found that by adjusting the ratio between the total mass of the various monomeric compounds and the mass of the chain transfer agent, the molecular weight of the binder compound can be controlled within an ideal range to ensure good adhesion, good solubility, and ease of processing of the binder compound.

[0147] In some embodiments, in step (i), the molar ratio of the compound of formula (II) to the compound of formula (I) is 3:1 to 0.005:1, optionally 1.5:1 to 0.005:1, and more preferably 1:1 to 0.01:1. By controlling the molar ratio between the monomer compounds within the above range, the synthesized binder compound can be made less rigid, softer, less prone to breakage of the electrode after winding, and has good adhesion, making it less likely for active material to fall off.

[0148] The preparation method described in this application is reversible addition-fracture transfer (RAFT) polymerization. The product molecule obtained by this method includes a main chain formed by monomer molecules and groups at both ends of the main chain brought by an initiator-chain transfer agent. In this application, the binder compound obtained by the reaction has reactive groups, such as carboxyl groups, at the ends of the main chain to facilitate subsequent modification of graphite.

[0149] In some embodiments, the preparation method of this application uses a chain transfer agent of formula (III). Optionally, the chain transfer agent is 4-cyano-4-(propylthiocarbonyl)thiopentanoic acid (CPP) of formula (III-1):

[0150]

[0151] The inventors discovered that this chain transfer agent provides highly controllable polymerization reaction, and combined with control of synthesis conditions, it can effectively control the molecular weight range of the binder compound obtained from polymerization.

[0152] In some implementations, in formula (I), R 1 -R 6 Each is independently selected from hydrogen, halogen, and unsubstituted C. 1-6 Alkyl, unsubstituted or substituted C 6-20 Aryl; wherein the substituent in the aryl group is selected from C 1-3 At least one of alkyl groups and halogens.

[0153] In some embodiments, the compound of formula (I) may optionally be selected from butadiene, isoprene, dimethylbutadiene, hexachlorobutadiene, chloroprene, ethylbutadiene, hexadiene, butadienebenzene, chloroprenebenzene, tetraphenylbutadiene, methylphenylbutadiene, and difluorophenylbutadiene.

[0154] By selecting the above-mentioned compound of formula (I) with a flexible CH skeleton, flexibility can be provided to the resulting binder compound after polymerization, so that the binder compound can maintain good bonding performance during graphite expansion.

[0155] In some implementations, in formula (II), R 7 -R 9 Each is independently selected from hydrogen, amino, or unsubstituted C. 1-6 Alkyl, unsubstituted C 1-6 Alkylamino; optionally, R 7 -R 8 Each is independently selected from hydrogen, methyl, ethyl, dimethylamino, and 2-(N,N-diethylamino)ethyl, and R 9 Selected from hydrogen, methyl, and ethyl.

[0156] In some embodiments, the compound of formula (II) is selected from styrene, β-methylstyrene, β-(dimethylamino)styrene, α-methylstyrene, α-ethylstyrene, β-ethylstyrene and 2-(diethylamino)ethylstyrene.

[0157] By selecting the above-mentioned compound of formula (II) with a benzene ring structure, the π-π interaction between the benzene ring structure and graphite endows the binder compound with good bonding function between it and graphite.

[0158] In some embodiments, the preparation method of the first aspect of this application further includes the following steps:

[0159] (ii) React the reaction product obtained in step (i) with a reducing agent in a solvent, and R 12 Converted to hydroxyl groups;

[0160] or

[0161] (iii) React the reaction product obtained in step (i) with an amination agent in a solvent, and R 12 Converted to amide group; and

[0162] (iv) The reaction product obtained in step (iii) is reacted with an oxidizing agent in a solvent under alkaline conditions to convert the amide group into an amino group.

[0163] Through the above steps, the product of step (i) can be further used to obtain binder compounds with hydroxyl or amino groups at the ends. The inventors have discovered that binder compounds with these reactive groups can also modify graphite, thereby improving the problem of binder flotation.

[0164] In some embodiments, the solvent in step (ii) is at least one of tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide.

[0165] In some embodiments, the reducing agent in step (ii) is LiAlH4.

[0166] In some implementations, step (ii) is performed at -5°C to 5°C, or optionally at 0°C.

[0167] In some embodiments, the solvent in step (iii) is at least one of methanol or ethanol.

[0168] In some embodiments, the amination agent in step (iii) is ammonia.

[0169] In some implementations, step (iii) is performed at a temperature of 35°C-55°C, or optionally at 45°C-50°C.

[0170] In some embodiments, the solvent in step (iv) is at least one of methanol or ethanol.

[0171] In some embodiments, the oxidant in step (iv) is sodium hypochlorite.

[0172] In some embodiments, step (iv) is carried out in the presence of sodium hydroxide. In some embodiments, step (iv) is carried out at 20°C-30°C, optionally at 25°C-30°C.

[0173] In some implementations, the reaction times for steps (ii)-(iv) are conventionally determined by those skilled in the art.

[0174] In some implementations, the reaction in step (ii) is carried out for 4-6 hours, or optionally, for 4 hours.

[0175] In some implementations, the reaction in step (iii) is carried out for 10-14 hours, or optionally, for 10 hours.

[0176] In some implementations, the reaction in step (iv) is carried out for 6-8 hours, or optionally, for 6 hours.

[0177] adhesive compounds

[0178] This application also provides a binder compound obtained by the method described above for preparing the binder compound. The binder compound of this application can covalently bond to the graphite surface, thus maintaining a uniform distribution within the graphite during conventional coating and drying processes. This fundamentally solves the problem of binder floating during the coating and drying process of the negative electrode material, which leads to battery performance degradation.

[0179] In some embodiments, the adhesive compound has the structure of formula (IV):

[0180]

[0181] in

[0182] R 1 -R 11 Z and L are as defined above in this application.

[0183] R 13 Indicates carboxyl, hydroxymethyl, or amino groups;

[0184] The ratio of m / n is 1-100, optionally 1-50, and more preferably 1-13.

[0185] In this application, the binder contains special functional groups. When the relative content of the functional groups is controlled within the above range, the polymer chain can form compound bonds with the surface of the graphite particles. At the same time, the binder has good flexibility. Therefore, when the graphite modified in this way is made into a negative electrode sheet, it also has high flexibility and is not easy to crack.

[0186] In some implementations, in equation (IV), m is an integer from 500 to 15000, and n is an integer from 500 to 15000.

[0187] In some embodiments, the number-average molecular weight of the compound of formula (IV) is 30,000-3,000,000, optionally 50,000-2,000,000, and more preferably 300,000-1,000,000.

[0188] In some implementations, structural units Copolymerization can be carried out in random, block and / or alternating manners, with block copolymerization being an option.

[0189] The inventors discovered that by controlling the number-average molecular weight of the adhesive compound of formula (IV) within the above-mentioned range, it is possible to ensure that the amount of functional groups is high, the adhesion is good, and the adhesive has good solubility and is easy to process.

[0190] In some embodiments, the adhesive compound is selected from:

[0191]

[0192] The preferred binder compounds achieve both good adhesion and satisfactory chemical bonding with graphite, further improving battery performance. The inventors discovered that these binder compounds can all be used to modify graphite, forming chemical bonds with the graphite surface's inherent groups (such as carboxyl groups) through a chemical reaction. This achieves a stable connection between the binder and graphite, preventing the floating phenomenon common in traditional binders during subsequent electrode coating. This fundamentally improves electrode adhesion performance, preventing the active material on the electrode from detaching during the cell's lifespan, thereby improving the cell's cycle performance.

[0193] Negative electrode sheet

[0194] A third aspect of this application provides a negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, the negative electrode material layer comprising modified graphite of the first aspect of this application or modified graphite prepared according to the preparation method of the second aspect of this application.

[0195] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0196] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0197] In some embodiments, the negative electrode material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0198] In some embodiments, the negative electrode material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0199] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0200] The inventors have discovered that the modified graphite of this application can be used to prepare negative electrode sheets only under conventional drying conditions, without the need for relatively inefficient drying methods such as multi-stage drying or low-temperature drying. In other words, using the modified graphite of this application can improve the binder floating problem without affecting production efficiency, resulting in electrode sheets or batteries with better performance.

[0201] Secondary batteries

[0202] A fourth aspect of this application provides a secondary battery comprising the negative electrode provided in the third aspect of this application.

[0203] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0204] In some embodiments, the secondary battery is a lithium-ion secondary battery.

[0205] [Positive electrode plate]

[0206] The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector, the positive electrode material layer including the positive electrode active material of the first aspect of this application.

[0207] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0208] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0209] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0210] In some embodiments, the positive electrode material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0211] In some embodiments, the positive electrode material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0212] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone (NMP)) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0213] [Electrolytes]

[0214] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0215] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0216] The electrolyte salt may be any electrolyte salt known in the art for use in secondary batteries. In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0217] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0218] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0219] [Isolation membrane]

[0220] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0221] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0222] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0223] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0224] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0225] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 6 As an example, a square-structured secondary battery 5.

[0226] In some implementations, refer to Figure 7The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0227] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0228] Figure 8 This is battery module 4, used as an example. (See reference...) Figure 8 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0229] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0230] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0231] Figure 9 and Figure 10 This is battery pack 1 as an example. (See reference...) Figure 9 and Figure 10 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0232] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0233] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0234] Figure 11 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0235] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0236] Example

[0237] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0238] Test method:

[0239] Infrared spectroscopy test

[0240] According to the standard GB / T6040-2002 infrared spectroscopy analysis method, the structural composition of the adhesives corresponding to all examples and comparative examples was measured using an IS10 Fourier transform infrared spectrometer from Nicolet Corporation, USA. The test wavenumber range was 400-4000 cm⁻¹. -1 .

[0241] Number-average molecular weight (Mn) test

[0242] The number-average molecular weight (Mn) of the binder compounds obtained in each example was measured using a Tosoh Corporation HLC-8320GPC gel permeation chromatography system (SuperMultipore HZ series semi-micro SEC column, polystyrene as standard).

[0243] Test procedure: Dissolve 2 mg of the polymer powder to be tested in 2 mL of GPC-specific DMF solvent, and then inject 2.5 μL for testing.

[0244] parameter:

[0245] Pump flow rate: 5 mL / min;

[0246] Filling volume: 100μL;

[0247] Temperature control range: 60℃;

[0248] Data acquisition frequency: 100Hz.

[0249] 1H NMR spectroscopy

[0250] The molecular structure of the product was determined on a Bruker AVANCEⅢ 400 NMR spectrometer at a test temperature of 25 °C. Tetramethylsilane (TMS) was used as an internal standard, and the solvents used were deuterated chloroform (CDCl3), deuterated methanol (CD3OD-d4), and deuterated dimethyl sulfoxide (DMSO-d6).

[0251] Test procedure: Dissolve 5 mg of sample in the above solvent, transfer to an NMR tube, inject 1 mL of sample, and the test can be performed.

[0252] This allows us to determine the molecular structure of the product and the values ​​of m and n.

[0253] Adhesion performance test

[0254] Take the negative electrode sheets from each embodiment and comparative example, and cut them into test samples 100mm long and 10mm wide. Take a 25mm wide stainless steel plate, apply double-sided tape (11mm wide), and attach the negative electrode material side of the test sample to the double-sided tape on the stainless steel plate. Roll the surface back and forth three times with a 2000g roller at a speed of 300mm / min. Then, bend one end of the test sample 180 degrees and manually peel the negative electrode material layer of the test sample away from the current collector along the length direction by 25mm. Fix the test sample on the INSTRON 336 testing machine, making sure the peeling surface is aligned with the force line of the testing machine (i.e., parallel to the direction of movement of the testing machine during peeling). Continue to peel the test sample continuously with the testing machine at a speed of 30mm / min to obtain the peeling force curve. Take the average value of the stable segment within a range of about 30s (that is, the segment on the peel force curve that no longer increases monotonically) as the peel force F0. Then, the adhesion force between the negative electrode membrane and the current collector in the test sample is F = F0 / width of the test sample (the unit of F is N / m).

[0255] Dispersion performance test

[0256] The dispersion properties of the binder were determined by electron probe X-ray microscopy analysis of the longitudinal section (thickness direction) of the electrode under test. According to standard GB / T32055-2015, a Shimadzu EPMA-1720 instrument was used, with a W filament X-ray emission source and a take-off angle of 52.5°. The dispersion (or floating) of the binder in the negative electrode material was then observed.

[0257] Battery cycle performance test

[0258] At 25℃, the lithium-ion battery under test was charged at a constant current rate of 1C to the charging cutoff voltage of 4.30V, then charged at a constant voltage until the current ≤0.05C, and allowed to stand for 10 minutes. It was then discharged at a constant current rate of 1C to the discharge cutoff voltage of 3.3V, and allowed to stand for 10 minutes. This constitutes one charge-discharge cycle (i.e., one cycle (cls)). The battery was subjected to 1000 charge-discharge cycle tests using this method, and the discharge capacity retention rate after 1000 charge-discharge cycles relative to the discharge capacity of the first charge-discharge cycle was recorded.

[0259] Battery high-temperature storage performance test

[0260] The newly prepared lithium-ion battery has an initial capacity, also known as the capacity before storage, C0. The testing method is as follows: the battery is placed at 25°C and charged at a constant current rate of 1C to the charging cutoff voltage of 4.35V. Then, it is charged at a constant voltage until the current is ≤0.05C, and then discharged at a constant current rate of 1C to the discharge cutoff voltage of 2.8V. The initial capacity C0 of the lithium-ion battery is then measured.

[0261] At 25℃, the lithium-ion battery under test was charged at a constant current rate of 1C to the charging cutoff voltage of 4.35V, followed by constant voltage charging until the current ≤0.05C. The battery was then transferred to a 60℃ environment for storage. After 180 days (d), the battery was returned to 25℃ and charged at a constant current rate of 1C to the charging cutoff voltage of 4.35V, followed by constant voltage charging until the current ≤0.05C. Finally, it was discharged at a constant current rate of 1C to the discharge cutoff voltage of 2.8V, and the discharge capacity C1 was measured. The retention rate of the discharge capacity after 180 days of storage was recorded as C1 / C0 × 100%.

[0262] Example 1

[0263] 1. Preparation of binder compounds with terminal carboxyl groups:

[0264] In a three-necked flask containing 200 mL of tetrahydrofuran, 10.4 g (0.100 mol) of styrene, 5.4 g (0.100 mol) of butadiene, and 0.5 g of chain transfer agent 4-cyano-4-(propylthiocarbonyl)thiopentanoic acid (CPP) were added and dissolved. A vacuum was then applied to prevent oxidation of free radicals. After vacuuming, 0.05 g of azobisisobutyronitrile initiator was added to the flask while continuously purging with N2. The mixture was heated to 70 °C and stirred for 12 h. The resulting crude product was then poured into ice-cold diethyl ether at 0 °C to settle, yielding the binder compound.

[0265] The synthesis route is shown in the figure below:

[0266]

[0267] The above-mentioned adhesive compound was subjected to infrared spectroscopy testing, and the test results are as follows: Figure 1 In the diagram, 2800-3000cm -1 It is a stretching vibration of saturated CH or CH2, 3000-3100 cm. -1 The spectral band is a characteristic peak of CH on the benzene ring, at 1493 cm⁻¹. -1 and 1601cm -1 This is a skeletal vibration of the benzene ring, 698 cm⁻¹ -1 and 757cm -1 It is an out-of-plane bending vibration of hydrogen on a monosubstituted benzene ring, 909 cm⁻¹ -1 The peak at 965 cm⁻¹ is a characteristic absorption peak for the out-of-plane bending vibration of the CH group on the C=CH double bond in 1,2-butadiene. -1 The strong absorption peak at that point is a characteristic absorption peak of the out-of-plane bending vibration of the CH double bond in 1,4-butadiene C=CH.

[0268] 2. Preparation of modified graphite:

[0269] Weigh graphite and the binder compound prepared in step 1 at a mass ratio of 95:2 and place them in a reaction vessel. Then add pyridine and dichloromethane. Stir and react for 2 hours at 25°C and pH 4.5-6, then filter to obtain a solid substance. Transfer the obtained solid substance to a beaker, add an appropriate amount of dichloromethane, stir and wash for 30 minutes, then filter and dry to obtain modified graphite.

[0270] The modified graphite was dispersed in NMP, then filtered, washed, and dried. The resulting solid was subjected to infrared spectroscopy. The test results are as follows: Figure 2 As shown. Among them, 2800-3000cm -1 It is a stretching vibration of saturated CH or CH2, 3000-3100 cm. -1 The spectral band is a characteristic peak of CH on the benzene ring, at 1493 cm⁻¹. -1 and 1601cm -1 This is a skeletal vibration of the benzene ring, 698 cm⁻¹ -1 and 757cm -1 It is an out-of-plane bending vibration of hydrogen on a monosubstituted benzene ring, 909 cm⁻¹ -1 The peak at 965 cm⁻¹ is a characteristic absorption peak for the out-of-plane bending vibration of the CH group on the C=CH double bond in 1,2-butadiene. -1 The strong absorption peak at that point is a characteristic absorption peak of the out-of-plane bending vibration of the CH double bond in 1,4-butadiene C=CH.

[0271] The binder compound in this application is a polymer that is soluble in NMP. However, the modified graphite obtained by combining the binder compound with graphite is insoluble in NMP. Therefore, after the above treatment, the characteristic peaks of the binder compound are still present in its infrared spectrum. This indicates that in the modified graphite obtained in this step, the binder compound and graphite are bonded by chemical bonds, rather than by physical mixing.

[0272] 3. Preparation of the negative electrode sheet:

[0273] The modified graphite prepared in step 2 above was dry-mixed with conductive carbon black at a weight ratio of 97:3. Deionized water was added to adjust the solid content to 45%-55% by weight. After stirring evenly, a negative electrode slurry was obtained. Then, it was prepared at 150 mg / cm³. 2 The loading amount is coated on the current collector copper foil, and then dried, cold pressed and slit to form the negative electrode sheet. The coating and drying conditions are: coating speed 50m / min, drying temperature 130℃.

[0274] 4. Preparation of the positive electrode sheet:

[0275] The ternary cathode material (lithium nickel cobalt manganese oxide), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were mixed evenly at a weight ratio of 96:2.5:1.5. Then, NMP solvent was added to adjust the solid content to 70%-80% by weight. After stirring evenly, a cathode slurry was obtained. Then, a solution of 200 mg / cm³ was added. 2 The loading amount is coated on the current collector, and after drying, cold pressing and slitting, it is made into a positive electrode sheet.

[0276] 5. Preparation of lithium-ion batteries:

[0277] The electrodes and separators obtained in steps 3 and 4 are wound into a battery cell and encapsulated in an aluminum-plastic film to form a dry battery cell. Through processes such as electrolyte injection, formation, and aging, a lithium-ion battery is obtained. The electrolyte used in the electrolyte injection step is prepared as follows: ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed evenly at a volume ratio of 3 / 7, and then LiPF6 is added to prepare a 1 mol / L solution.

[0278] Example 2

[0279] 1. Preparation of adhesive compounds with terminal hydroxyl groups:

[0280] (1) In a three-necked flask containing 200 mL of tetrahydrofuran, add 10.4 g (0.100 mol) styrene, 5.4 g (0.100 mol) butadiene and 0.5 g chain transfer agent CPP to dissolve them; evacuate the flask to prevent free radicals from being oxidized. After evacuation, under the condition of continuously purging N2 into the flask, add 0.05 g of azobisisobutyronitrile initiator and heat to 70 °C. After stirring the reaction at 70 °C for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and obtain a powdery solid.

[0281] (2) Dissolve the obtained powdered solid in 200 mL of tetrahydrofuran, add 0.5 g of LiAlH4, and stir the reaction in an ice-water bath at 0 °C for 4 h. Then, pour the reaction solution into ice-cold diethyl ether at 0 °C for precipitation again to obtain the binder product. The synthetic route for this step is as follows:

[0282]

[0283] 2. Preparation of modified graphite:

[0284] Weigh graphite and the binder compound prepared in step 1 at a mass ratio of 95:2 and place them in a reaction vessel. Then add pyridine and dichloromethane. Stir and react at 25°C and pH 4.5-6 for 2 hours, then filter to obtain a solid substance. Transfer the obtained solid substance to a beaker, add an appropriate amount of dichloromethane, stir and wash for 30 minutes, then filter and dry to obtain modified graphite.

[0285] The modified graphite was dispersed in NMP, then filtered, washed, and dried. The resulting solid was subjected to infrared spectroscopy. The test results are as follows: Figure 3 As shown. Among them, 2800-3000cm -1 It is a stretching vibration of saturated CH or CH2, 3000-3100 cm. -1 The spectral band is a characteristic peak of CH on the benzene ring, at 1493 cm⁻¹. -1 and 1601cm -1 This is a skeletal vibration of the benzene ring, 698 cm⁻¹ -1 and 757cm -1 It is an out-of-plane bending vibration of hydrogen on a monosubstituted benzene ring, 909 cm⁻¹ -1 The peak at 965 cm⁻¹ is a characteristic absorption peak for the out-of-plane bending vibration of the CH group on the C=CH double bond in 1,2-butadiene. -1 The strong absorption peak at this point is a characteristic absorption peak of the out-of-plane bending vibration of the CH double bond in 1,4-butadiene. It can be seen that after solvent treatment, the modified graphite still yields similar spectral results to the binder compound in infrared spectroscopy. This indicates that in the modified graphite, the binder portion is chemically bonded to the graphite, rather than physically mixed.

[0286] 3. Prepare the negative electrode, positive electrode and lithium-ion battery according to steps 3-5 in Example 1.

[0287] Example 3

[0288] 1. Preparation of binder compounds with terminal amino groups:

[0289] (1) In a three-necked flask containing 200 mL of tetrahydrofuran, add 10.4 g (0.100 mol) styrene, 5.4 g (0.100 mol) butadiene and 0.5 g chain transfer agent CPP to dissolve them; evacuate the flask to prevent free radicals from being oxidized. After evacuation, under the condition of continuously purging N2 into the flask, add 0.05 g of azobisisobutyronitrile initiator and heat to 70 °C. After stirring the reaction at 70 °C for 12 h, pour the obtained crude product into ice-cold diethyl ether at 0 °C to precipitate, and obtain a powder solid.

[0290] (2) Transfer the obtained powder solid to a three-necked flask, add 200 mL of methanol, and purge with ammonia gas at a reaction temperature of 45°C. After reacting for 10 h, pour the mixture into ice-cold ether at 0°C to settle, obtaining a solid. Transfer the obtained solid to a round-bottom flask, add 2 g of sodium hypochlorite, dissolve it in 200 mL of methanol, then add 50 mL of sodium hydroxide. Stir and react at 25°C for 6 h. Finally, pour the obtained product into ice-cold ether at 0°C to settle, thus obtaining the desired binder product. The reaction route for this step is as follows:

[0291]

[0292] 2. Preparation of modified graphite:

[0293] Weigh graphite and the binder compound prepared in step 1 at a mass ratio of 95:2 and place them in a reaction vessel. Then add pyridine and dichloromethane. Stir and react at 25°C and pH 4.5-6 for 2 hours, then filter to obtain a solid substance. Transfer the obtained solid substance to a beaker, add an appropriate amount of dichloromethane, stir and wash for 30 minutes, then filter and dry to obtain modified graphite.

[0294] The modified graphite was dispersed in NMP, then filtered, washed, and dried. The resulting solid was subjected to infrared spectroscopy. The test results are as follows: Figure 4 As shown. Among them, 2800-3000cm -1 It is a stretching vibration of saturated CH or CH2, 3000-3100 cm. -1 The spectral band is a characteristic peak of CH on the benzene ring, at 1493 cm⁻¹. -1 and 1601cm -1 This is a skeletal vibration of the benzene ring, 698 cm⁻¹ -1 and 757cm -1 It is an out-of-plane bending vibration of hydrogen on a monosubstituted benzene ring, 909 cm⁻¹ -1 The peak at 965 cm⁻¹ is a characteristic absorption peak for the out-of-plane bending vibration of the CH group on the C=CH double bond in 1,2-butadiene. -1 The strong absorption peak at this point is a characteristic absorption peak of the out-of-plane bending vibration of the CH double bond in 1,4-butadiene. It can be seen that after solvent treatment, the modified graphite still yields similar spectral results to the binder compound in infrared spectroscopy. This indicates that in the modified graphite, the binder portion is chemically bonded to the graphite, rather than physically mixed.

[0295] 3. Prepare the negative electrode, positive electrode and lithium-ion battery according to steps 3-5 in Example 1.

[0296] Example 4

[0297] 1. Preparation of binder compounds:

[0298] In a three-necked flask containing 200 mL of tetrahydrofuran, 3.9 g (0.033 mol) of β-methylstyrene, 6.8 g (0.100 mol) of isoprene, and 0.5 g of chain transfer agent CPP were added and dissolved. A vacuum was applied to prevent oxidation of free radicals. After vacuuming, 0.05 g of azobisisobutyronitrile initiator was added to the flask while continuously purging N2 into the flask. The mixture was heated to 70 °C and stirred for 12 h. The resulting crude product was then poured into ice-cold diethyl ether at 0 °C to settle, yielding a binder compound powder.

[0299] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0300] Example 5

[0301] 1. Preparation of binder compounds:

[0302] In a three-necked flask containing 200 mL of tetrahydrofuran, 3.5 g (0.034 mol) of styrene, 26.1 g (0.100 mol) of hexachlorobutadiene, and 0.5 g of chain transfer agent CPP were added and dissolved; a vacuum was then applied. After the vacuum was removed, 0.05 g of azobisisobutyronitrile initiator was added to the flask while N2 was continuously bubbled into it, and the mixture was then heated to 70 °C. After stirring the reaction at 70 °C for 12 h, the resulting product was poured into ice-cold diethyl ether at 0 °C to settle, yielding a binder compound powder.

[0303] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0304] Example 6

[0305] 1. Preparation of binder compounds:

[0306] In a three-necked flask containing 200 mL of tetrahydrofuran, 0.6 g (0.005 mol) of α-methylstyrene, 8.9 g (0.101 mol) of chloroprene, and 0.5 g of chain transfer agent CPP were added and dissolved, followed by evacuation. After evacuation, 0.05 g of azobisisobutyronitrile initiator was added to the flask under continuous N2 purging, and the mixture was heated to 70 °C. After stirring and reacting at 70 °C for 12 h, the resulting product was poured into ice-cold diethyl ether at 0 °C to precipitate, yielding a binder compound powder.

[0307] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0308] Example 7

[0309] 1. Preparation of binder compounds:

[0310] In a three-necked flask containing 200 mL of tetrahydrofuran, 1.3 g (0.010 mol) of α-ethylstyrene, 8.9 g (0.101 mol) of chloroprene, and 0.5 g of chain transfer agent CPP were added and dissolved, and a vacuum was applied. After the vacuum was removed, 0.05 g of azobisisobutyronitrile initiator was added to the flask under continuous N2 purging, and then the mixture was heated to 70 °C. After stirring and reacting at 70 °C for 12 h, the resulting crude product was poured into ice-cold diethyl ether at 0 °C to settle, yielding a binder powder.

[0311] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0312] Example 8

[0313] 1. Preparation of binder compounds:

[0314] In a three-necked flask containing 200 mL of tetrahydrofuran, 1.2 g (0.012 mol) of styrene, 8.2 g (0.100 mol) of ethylbutadiene, and 0.5 g of chain transfer agent CPP were added and dissolved, followed by evacuation. After evacuation, 0.05 g of azobisisobutyronitrile initiator was added to the flask under continuous N2 purging, and the mixture was heated to 70 °C. After stirring and reacting at 70 °C for 12 h, the resulting crude product was poured into ice-cold diethyl ether at 0 °C to precipitate, yielding a binder compound powder.

[0315] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0316] Example 9

[0317] 1. Preparation of binder compounds:

[0318] In a three-necked flask containing 200 mL of tetrahydrofuran, 0.2 g (0.002 mol) of styrene, 8.2 g (0.100 mol) of 1,3-hexadiene, and 0.5 g of chain transfer agent CPP were added and dissolved, followed by evacuation. After evacuation, 0.05 g of azobisisobutyronitrile initiator was added to the flask under continuous N2 purging, and the mixture was heated to 70 °C. After stirring the reaction at 70 °C for 12 h, the resulting crude product was poured into ice-cold diethyl ether at 0 °C to precipitate, yielding a binder compound powder.

[0319] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0320] Example 10

[0321] 1. Preparation of binder compounds:

[0322] In a three-necked flask containing 200 mL of tetrahydrofuran, 0.4 g (0.004 mol) of styrene, 13.1 g (0.101 mol) of phenyl-1,3-butadiene (CAS: 16939-57-4, Jiangsu Aikon Biomedical R&D Co., Ltd.), and 0.5 g of chain transfer agent CPP were added to dissolve the styrene and a vacuum was applied. After the vacuum was removed, 0.05 g of azobisisobutyronitrile initiator was added to the flask under continuous N2 purging, and the mixture was heated to 70 °C. After stirring the reaction at 70 °C for 12 h, the resulting crude product was poured into ice-cold diethyl ether at 0 °C to settle, yielding a binder compound powder.

[0323] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0324] Example 11

[0325] 1. Preparation of binder compounds:

[0326] In a three-necked flask containing 200 mL of tetrahydrofuran, 0.3 g (0.003 mol) of styrene, 16.5 g (0.100 mol) of 4-chloro-1,3-butadiene-benzene (CAS No.: 18684-87-2, Shenzhen Aituo Chemical Co., Ltd.), and 0.5 g of chain transfer agent CPP were added to dissolve the styrene and the flask was evacuated. After evacuation, 0.05 g of azobisisobutyronitrile initiator was added to the flask under continuous N2 purging, and the mixture was heated to 70 °C. After stirring the reaction at 70 °C for 12 h, the crude product was poured into ice-cold diethyl ether at 0 °C to settle, yielding a binder compound powder.

[0327] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0328] Example 12

[0329] 1. Preparation of binder compounds:

[0330] In a three-necked flask containing 200 mL of tetrahydrofuran, 0.9 g (0.007 mol) of β-ethylstyrene, 23.4 g (0.100 mol) of 1,1-bis-(4-methylphenyl)-1,3-butadiene (CAS: 93874-11-4, Shenzhen Aituo Chemical Co., Ltd.), and 0.5 g of chain transfer agent CPP were added to dissolve the compounds, and a vacuum was applied. After the vacuum was removed, 0.05 g of azobisisobutyronitrile initiator was added to the flask under continuous N2 purging, and the mixture was heated to 70 °C. After stirring the reaction at 70 °C for 12 h, the resulting crude product was poured into ice-cold diethyl ether at 0 °C to precipitate, yielding a binder compound powder.

[0331] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0332] Example 13

[0333] 1. Preparation of binder compounds:

[0334] In a three-necked flask containing 200 mL of tetrahydrofuran, 1.6 g (0.005 mol) of 2-(diethylamino)ethylstyrene (CAS: 74952-73-1, Shenzhen Aituo Chemical Co., Ltd.), 24.2 g (0.100 mol) of difluorophenylbutadiene (CAS: 3888-61-7), and 0.5 g of chain transfer agent CPP were added to dissolve the compounds, and a vacuum was applied. After the vacuum was removed, 0.05 g of azobisisobutyronitrile initiator was added to the flask under continuous N2 purging, and the mixture was heated to 70 °C. After stirring the reaction at 70 °C for 12 h, the resulting crude product was poured into ice-cold diethyl ether at 0 °C to settle, yielding a binder compound powder.

[0335] 2. Prepare modified graphite, negative electrode, positive electrode and lithium-ion battery according to steps 2-5 in Example 1.

[0336] Examples 14-17

[0337] Modified graphite was prepared using the binder compound obtained in Example 1, following step 2 in Example 1.

[0338] The mass ratio of graphite to binder compound is shown in Table 1 below.

[0339] Table 1. Mass ratio of graphite to binder compound

[0340]

[0341] Comparative Example

[0342] 1. Preparation of negative electrode sheet:

[0343] Graphite and conductive agent carbon black were dry-mixed at a mass ratio of 95:3, then deionized water was added to adjust the solid content to 45%-55% by weight. Styrene-butadiene rubber (SBR) was then added as a binder to achieve a graphite:conductive agent:binder mass ratio of 95:3:2. After thorough mixing, a negative electrode slurry was obtained. Then, a concentration of 150 mg / cm³ was applied. 2 The loading amount is coated on the current collector copper foil, and then dried, cold-pressed and slit to form the negative electrode sheet. The coating and drying conditions are: coating speed 50m / min, drying temperature 130℃.

[0344] 2. Prepare the positive electrode and lithium-ion battery according to steps 4-5 in Example 1.

[0345] Performance test results

[0346] The negative electrode sheets and lithium-ion batteries prepared in the above embodiments and comparative examples were subjected to performance tests, and the results are shown in Table 2.

[0347] Table 2 shows the molecular weight, electrode adhesion, and high-temperature storage performance and cycle performance of the binder compounds in the examples and comparative examples.

[0348]

[0349]

[0350] As can be seen from Table 2 above, compared with the comparative example, the negative electrode sheet of this application embodiment has significantly improved adhesion. After being assembled into a lithium-ion battery, the storage and cycle performance of the battery is significantly improved.

[0351] Test results on improved adhesive floating effect

[0352] X-ray microscopy analysis was performed on the negative electrode sheets prepared in Example 1 and the comparative example, and the results are as follows: Figure 5 As shown in the figure, the white dots represent the binder or the binder portion of the modified graphite in this application, as observed during the test. Comparing the two figures, it can be seen that in the negative electrode sheet prepared in the comparative example, the binder shows obvious floating, while in the negative electrode sheet prepared in Example 1, the binder distribution is significantly more uniform.

[0353] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A modified graphite, wherein, The modified graphite comprises a graphite portion and a binder portion covalently linked to the graphite portion, the binder portion having a structure of formula (IV'): (IV’) in, R 1 -R 6 Each is independently selected from hydrogen, halogen, cyano, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 2-6 alkenyl, unsubstituted or substituted C 6-20 aryl, wherein the substituents in the alkyl, alkoxy, alkenyl and aryl groups are selected from C 1-3 At least one of alkyl, hydroxyl, amino, amide, cyano, carboxyl, and halogen groups; R 7 -R 9 Each is independently selected from hydrogen, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 1-6 Alkylamino, unsubstituted or substituted C 2-6 Alkenyl and unsubstituted or substituted C 6-20 The aryl group, wherein the substituents in the alkyl, alkoxy, alkylamino, alkenyl and aryl groups are selected from at least one of hydroxyl, carboxyl, amino, amide, and halogen groups; R 10 C represents a straight chain or a branched chain. 1-12 alkyl, R 11 Indicates halogen or cyano. Z is selected from straight-chain or branched C1-C5 alkylthio groups. L represents C, which is either a straight chain or a branched chain. 1-12 alkylene, R 13a This indicates #-COO-*, #-CH2O-*, or #-NH-*, where # indicates the position connected to L, and * indicates the position connected to the graphite portion; The ratio of m / n is 1-100.

2. The modified graphite according to claim 1, wherein, R 1 -R 6 Each is independently selected from hydrogen, halogen, and unsubstituted C. 1-6 Alkyl, unsubstituted or substituted C 6-20 Aryl; wherein the substituent in the aryl group is selected from C 1-3 At least one of alkyl groups and halogens.

3. The modified graphite according to claim 1, wherein, R 7 -R 9 Each is independently selected from hydrogen, amino, or unsubstituted C. 1-6 Alkyl, unsubstituted C 1-6 At least one of alkylamino groups.

4. The modified graphite according to claim 1, wherein, R 7 -R 8 Each is independently selected from at least one of hydrogen, methyl, ethyl, dimethylamino, and 2-(N,N-diethylamino)ethyl, and R 9 It is selected from at least one of hydrogen, methyl, and ethyl.

5. The modified graphite according to claim 1, wherein, R 10 C is a straight chain or a branched chain 1-6 alkyl.

6. The modified graphite according to claim 1, wherein, R 10 It is a methyl group.

7. The modified graphite according to claim 1, wherein, R 11 It is a cyano group.

8. The modified graphite according to claim 1, wherein, Z is selected from methylthio, ethylthio, propenthio, butylthio, or pentylthio.

9. The modified graphite according to claim 1, wherein, L represents either a straight chain or a branched chain. 1-6 Alkylene.

10. The modified graphite according to claim 1, wherein, L stands for methylene.

11. The modified graphite according to claim 1, wherein, The ratio of m / n is 1-50.

12. The modified graphite according to claim 1, wherein, The ratio of m / n is 1-13.

13. The modified graphite according to claim 1, wherein, m is an integer between 500 and 15000, and n is an integer between 500 and 15000.

14. The modified graphite according to claim 1, wherein, The number average molecular weight of the binder portion of formula (IV') is 30,000-3,000,000.

15. The modified graphite according to claim 1, wherein, The number average molecular weight of the binder portion of formula (IV') is 50,000-2,000,000.

16. The modified graphite according to claim 1, wherein, The number average molecular weight of the binder portion of formula (IV') is 300,000-1,000,000.

17. The modified graphite according to claim 1, wherein, Structural units in the adhesive portion and Copolymerize in random, block and / or alternating manner.

18. The modified graphite according to claim 1, wherein, Structural units in the adhesive portion and Co-aggregates in a segmented manner.

19. The modified graphite according to claim 1, wherein, The adhesive portion is selected from the following structures: (IV’-1), (IV'-2), or (IV’-3), The asterisk (*) indicates the location where the binder portion is covalently connected to the graphite portion.

20. The modified graphite according to any one of claims 1 to 19, wherein, The mass ratio of the graphite portion to the binder portion is 85:12-96.5:0.

5.

21. The modified graphite according to any one of claims 1 to 19, wherein, The mass ratio of the graphite portion to the binder portion is 90:7-96:

1.

22. A method for preparing modified graphite, comprising the following steps: The binder compound was reacted with graphite in a solvent in the presence of the catalyst pyridine. The adhesive compound has the structure of formula (IV): (IV) in, R 1 -R 6 Each is independently selected from hydrogen, halogen, cyano, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 2-6 alkenyl, unsubstituted or substituted C 6-20 aryl, wherein the substituents in the alkyl, alkoxy, alkenyl and aryl groups are selected from C 1-3 At least one of alkyl, hydroxyl, amino, amide, cyano, carboxyl, and halogen groups; R 7 -R 9 Each is independently selected from hydrogen, hydroxyl, amino, unsubstituted or substituted C. 1-6 Alkyl, unsubstituted or substituted C 1-6 alkoxy, unsubstituted or substituted C 1-6 Alkylamino, unsubstituted or substituted C 2-6 Alkenyl and unsubstituted or substituted C 6-20 The aryl group, wherein the substituents in the alkyl, alkoxy, alkylamino, alkenyl and aryl groups are selected from at least one of hydroxyl, carboxyl, amino, amide, and halogen groups; R 10 C represents a straight chain or a branched chain. 1-12 alkyl, R 11 Indicates halogen or cyano. Z is selected from straight-chain or branched C1-C5 alkylthio groups. L represents C, which is either a straight chain or a branched chain. 1-12 alkylene, R 13 Indicates carboxyl, hydroxymethyl, or amino groups; The ratio of m / n is 1-100.

23. The preparation method according to claim 22, wherein, R 1 -R 6 Each is independently selected from hydrogen, halogen, and unsubstituted C. 1-6 Alkyl, unsubstituted or substituted C 6-20 Aryl; wherein the substituent in the aryl group is selected from C 1-3 At least one of alkyl groups and halogens.

24. The preparation method according to claim 22, wherein, R 7 -R 9 Each is independently selected from hydrogen, amino, or unsubstituted C. 1-6 Alkyl, unsubstituted C 1-6 At least one of alkylamino groups.

25. The preparation method according to claim 22, wherein, R 7 -R 8 Each is independently selected from at least one of hydrogen, methyl, ethyl, dimethylamino, and 2-(N,N-diethylamino)ethyl, and R 9 It is selected from at least one of hydrogen, methyl, and ethyl.

26. The preparation method according to claim 22, wherein, R 10 C is a straight chain or a branched chain 1-6 alkyl.

27. The preparation method according to claim 22, wherein, R 10 It is a methyl group.

28. The preparation method according to claim 22, wherein, R 11 It is a cyano group.

29. The preparation method according to claim 22, wherein, Z is selected from methylthio, ethylthio, propenthio, butylthio, or pentylthio.

30. The preparation method according to claim 22, wherein, L represents either a straight chain or a branched chain. 1-6 Alkylene.

31. The preparation method according to claim 22, wherein, L stands for methylene.

32. The preparation method according to claim 22, wherein, The ratio of m / n is 1-50.

33. The preparation method according to claim 22, wherein, The ratio of m / n is 1-13.

34. The preparation method according to claim 22, wherein, In the adhesive compound, m is an integer between 500 and 15000, and n is an integer between 500 and 15000.

35. The preparation method according to claim 22, wherein, The number average molecular weight of the binder compound is 30,000-3,000,000.

36. The preparation method according to claim 22, wherein, The number average molecular weight of the adhesive compound is 50,000-2,000,000.

37. The preparation method according to claim 22, wherein, The number average molecular weight of the binder compound is 300,000-1,000,000.

38. The preparation method according to claim 22, wherein, The structural unit of the adhesive compound and Copolymerize in random, block and / or alternating manner.

39. The preparation method according to claim 22, wherein, The structural unit of the adhesive compound and Co-aggregates in a segmented manner.

40. The preparation method according to claim 22, wherein, The adhesive compound is selected from at least one of the following: (IV-1), (IV-2), and (IV-3)。 41. The preparation method according to claim 22, wherein, The pH of the reaction is 4-7.

42. The preparation method according to claim 22, wherein, The pH of the reaction is 4.5-6.

43. The preparation method according to claim 22, wherein, The mass ratio of graphite to the binder compound is 85:12 to 96.5:0.

5.

44. The preparation method according to claim 22, wherein, The mass ratio of the graphite to the binder compound is 90:7-96:

1.

45. The preparation method according to claim 22, wherein, The reaction was carried out at 20°C-40°C.

46. ​​The preparation method according to claim 22, wherein, The reaction was carried out at 25°C-30°C.

47. A negative electrode plate, wherein, The negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, wherein the negative electrode material layer comprises modified graphite according to any one of claims 1 to 21 or modified graphite prepared by any one of claims 22 to 46.

48. A secondary battery, wherein, The secondary battery also includes the negative electrode sheet according to claim 47.

49. A battery module comprising the secondary battery according to claim 48.

50. A battery pack comprising at least one of the secondary battery of claim 48 or the battery module of claim 49.

51. An electrical device comprising at least one selected from the secondary battery of claim 48, the battery module of claim 49, or the battery pack of claim 50.

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