Silicon-carbon negative electrode material with core-shell structure, preparation method and application thereof

Abstract

The present application relates to a silicon-carbon negative electrode material with a core-shell structure and a preparation method and application thereof, wherein the silicon-carbon negative electrode material comprises an inner core and a coating layer coated on the surface of the inner core, the material of the inner core is a silicon-carbon material, and the material of the coating layer comprises a modified polymer material, the modified polymer material is obtained by reaction of a hydrophilic polymer and a small molecule additive, wherein the solubility parameter of the coating layer is 10.2 J 1 / 2 ·cm ‑3 / 2 ‑45J 1 / 2 ·cm ‑3 / 2 The structural formula of the small molecule additive is X-R1, X is selected from a hydrophilic reactive group, and R1 is selected from a hydrophobic chain. The silicon-carbon negative electrode material not only has good dispersibility in homogenization, but also can effectively reduce gas production, and can improve the mechanical stability of the electrode during preparation and use, thereby improving the cycle stability and service life of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of negative electrode materials, in particular to a silicon-carbon negative electrode material with a core-shell structure and a preparation method and application thereof. BACKGROUND

[0002] Compared with traditional graphite negative electrode materials, silicon-based negative electrode materials have become a hot research field due to their theoretical capacity. However, the commercial application of silicon-based negative electrode materials is hindered by their significant volume expansion and poor intrinsic conductivity during the charging and discharging process, which is not conducive to the cycle stability and long-term reliability of the battery.

[0003] In order to improve the performance of silicon negative electrode materials, a water-based binder is usually used as a coating material to modify the silicon negative electrode material. However, the use of hydrophilic polymers can cause the nano-silicon-based material to react with water during homogenization, produce gas, and result in the loss of effective active material. This not only poses a safety hazard during electrode manufacturing, but also easily causes defects in the electrode sheet, thereby reducing the overall performance of the battery. SUMMARY

[0004] Therefore, it is necessary to provide a silicon-carbon negative electrode material with a core-shell structure and a preparation method and application thereof to solve the above problems. The silicon-carbon negative electrode material not only has good dispersibility during homogenization, but also effectively reduces gas production. In addition, the mechanical stability of the electrode can be improved during the preparation and use of the electrode, thereby improving the cycle stability and service life of the battery.

[0005] A silicon-carbon negative electrode material includes an inner core and a coating layer coated on the surface of the inner core. The material of the inner core is a silicon-carbon material, and the material of the coating layer includes a modified polymer material obtained by reacting a hydrophilic polymer and a small molecule additive. The solubility parameter of the coating layer is 10.2 J 1 / 2 ·cm -3 / 2 -45 J 1 / 2 ·cm -3 / 2 The structural formula of the small molecule additive is X-R1, X is selected from a hydrophilic reactive group, and R1 is selected from a hydrophobic chain.

[0006] In one embodiment, the solubility parameter of the hydrophilic polymer is 20 J 1 / 2 ·cm -3 / 2 -50 J 1 / 2 ·cm -3 / 2 The solubility parameter of the small molecule additive is 10 J 1 / 2 ·cm -3 / 2 -30 J 1 / 2 ·cm -3 / 2 .

[0007] In one embodiment, the mass ratio of the hydrophilic polymer and the small molecule additive is (100-0.1):1.

[0008] In one embodiment, the mass fraction of the hydrophilic polymer in the modified polymer material is greater than or equal to the mass fraction of the small molecule additive.

[0009] In one embodiment, the hydrophilic polymer is selected from at least one of the compounds having the structures shown in formula (1) to formula (6),

[0010]

[0011] In formula (1), A1 is selected from N or P, when B1 is selected from any one of F - , Cl - , Br - , I - , OH - , SO4 2- , HSO4 -1 , SO3 2- , CO3 2- , HCO3 - , HCOO - , NO3 - , NO2 - , N3 - , BF4 - , PF6 - , FSI - , TFSI - , SbF6 - , TfS - , (C6F5)4B - , PO4 3- , HPO4 2- , H2PO4 - , ClO4 - , ClO3 - , FeCl4 - , AlCl4 - , ZnCl2 - , CuCl2 - , R8 and Y4 are both absent; when B1 is selected from any one of COO - , SO3 - , HPO4 - , PO4 2- , O - , S - , R8 and Y4 are both present; at least two of R3, R4, R5, R6, R7 and R8 can form a bond or a ring; in formula (2), A2 is selected from N or P, C1 is selected from COO- SO3 - HPO4 - PO4 2- O - S - R9, R 10 R 11 R 12 R 13 and R 14 may be bonded or cycled between at least two of R - , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 and R 21 ; in formula (4), A4 is selected from N or P, D2 is selected from PO4 - , R 22 , R 23 , R 24 , R 25 and R 26 may be bonded or cycled between at least two of R - , R - , R - , R 2- , R - , R - may be bonded or cycled between at least two of R 27 , R 28 , R 29 , R 30 and R 31 ; in formula (6), R 32 and R 33 may be bonded or cycled;

[0012] In formulae (1)-(6), R3, R4, R5, R6, R7, R8, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , R24 R 25 R 26 R 27 R 28 R 29 R 30 R 31 R 32 R 33 R and R are independently selected from any one of hydrogen atom, alkyl group having carbon number of 1-30, cycloalkyl group having carbon number of 3-30, alkenyl group having carbon number of 3-30, alkynyl group having carbon number of 3-30, aromatic group having carbon number of 6-30, heterocyclic group having carbon number of 3-30, heteroaromatic group having carbon number of 5-30, or, selected from any one of alkyl group having carbon number of 1-30, cycloalkyl group having carbon number of 3-30, alkenyl group having carbon number of 3-30, alkynyl group having carbon number of 3-30, aromatic group having carbon number of 6-30, heterocyclic group having carbon number of 3-30, heteroaromatic group having carbon number of 5-30 having at least one heteroatom or substituent, wherein the heteroatom is selected from at least one of O, S, N, Si, P, and the substituent is selected from any one of halogen atom, branched or straight chain hydrocarbon group having carbon number of 1-20, branched or straight chain alkoxy group having carbon number of 1-20, branched or straight chain cycloalkyl group having carbon number of 3-20, aromatic group having carbon number of 6-30, heteroaromatic group having carbon number of 5-30;

[0013] Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8, Y9, Y 10 Y 11 Y 12 Y 13 Y 14 Y 15 Y and Y 16 are independently selected from at least one of -COOH, -SO3H, -SO2H, -COCl, -COBr, -COI, -CONH2, -NH2, -NHNH2, -NCO, -NCS, -CHO, -OH, -SH, -SeH, =O, =S, =Se;

[0014] n1, n2, n3, n4, n5, n6 are independently selected from 14-14000.

[0015] In one embodiment, the hydrophilic polymer is selected from at least one of the compounds as shown in the structures of formula (7)-formula (14), wherein in formula (7)-formula (14), n is selected from 14-14000;

[0016]

[0017] In one of the embodiments, the hydrophilic polymer has a relative molecular mass of 1000-1000000.

[0018] In one of the embodiments, X is at least one selected from -COOH, -SO3H, -SO2H, -COCl, -COBr, -COI, -CONH2, -NH2, -NHNH2, -NCO, -NCS, -CHO, -OH, -SH, -SeH, =O, =S, =Se.

[0019] In one of the embodiments, R1 is at least one selected from alkyl group having 1-30 carbon atoms, cycloalkyl group having 3-30 carbon atoms, alkenyl group having 3-30 carbon atoms, alkynyl group having 3-30 carbon atoms, aromatic group having 6-30 carbon atoms, heterocyclic group having 3-30 carbon atoms, heteroaromatic group having 5-30 carbon atoms, or at least one selected from alkyl group having 1-30 carbon atoms, cycloalkyl group having 3-30 carbon atoms, alkenyl group having 3-30 carbon atoms, alkynyl group having 3-30 carbon atoms, aromatic group having 6-30 carbon atoms, heterocyclic group having 3-30 carbon atoms, heteroaromatic group having 5-30 carbon atoms having at least one heteroatom or substituent, wherein the heteroatom is at least one selected from O, S, N, Si, P, and the substituent is at least one selected from halogen atom, branched or straight chain hydrocarbon group having 1-20 carbon atoms, branched or straight chain alkoxy group having 1-20 carbon atoms, branched or straight chain cycloalkyl group having 3-20 carbon atoms, aromatic group having 6-30 carbon atoms, heteroaromatic group having 5-30 carbon atoms.

[0020] In one of the embodiments, the small molecule additive has a relative molecular mass of 30-1000.

[0021] In one of the embodiments, X is at least one selected from -COOH, -CHO, -OH, -SH, and R1 is at least one selected from alkyl group having 8-18 carbon atoms, cycloalkyl group having 8-18 carbon atoms.

[0022] In one of the embodiments, the small molecule additive is at least one selected from octanoic acid, n-decanal, n-hexylamine, n-heptanal, stearic acid, stearyl alcohol, polytetrahydrofuran.

[0023] In one of the embodiments, the mass ratio of the silicon-carbon material to the material of the coating layer is 100:(0.005-100).

[0024] In one of the embodiments, the silicon-carbon material has a median particle size of 1-20 μm.

[0025] In one of the embodiments, the coating layer has a thickness of 1-1000 nm.

[0026] In one of the embodiments, the material of the coating layer further comprises a conductive agent.

[0027] A preparation method of the silicon-carbon negative electrode material, comprising: dispersing the silicon-carbon material, the hydrophilic polymer and the small molecule additive in a solvent to prepare a mixture, and then drying the mixture to obtain the silicon-carbon negative electrode material.

[0028] In one of the embodiments, the mass ratio between the silicon-carbon material, the hydrophilic polymer and the small molecule additive is (60-100):(0.01-20):(0.01-20).

[0029] In one of the embodiments, the conductive agent is added in the step of dispersing the silicon-carbon material, the hydrophilic polymer and the small molecule additive in a solvent to prepare a mixture, and the mass ratio between the conductive agent and the silicon-carbon material is (0.001-0.25):1.

[0030] In one of the embodiments, the drying process comprises spray drying and vacuum drying, wherein the spray drying temperature is 100-300 DEG C, the spray drying time is 0.5-10 h, the vacuum drying temperature is 50-250 DEG C, and the vacuum drying time is 1-10 h.

[0031] A negative electrode sheet prepared by using the silicon-carbon negative electrode material.

[0032] A battery prepared by using the negative electrode sheet.

[0033] The silicon-carbon negative electrode material uses a small molecule additive with a specific structure to modify the hydrophilic polymer in situ, regulates the hydrophilic and hydrophobic properties of the hydrophilic polymer to form a coating layer with a specific proportion of hydrophilic groups and hydrophobic groups, and the solubility parameter of the coating layer is 10.2 J 1 / 2 ·cm -3 / 2 -45J 1 / 2 ·cm -3 / 2 The coating layer, on the one hand, can maintain the good dispersibility of the silicon-carbon negative electrode material during homogenization, and at the same time, as a protective layer of the silicon-carbon material, avoids the reaction of the silicon-carbon material with water, thereby effectively reducing the gas production of the silicon-carbon negative electrode material, reducing the loss of effective active material, and further improving the cycle performance and service life of the battery; on the other hand, in the process of preparing the electrode and using, it can reduce the gas production caused by the contact between the silicon-carbon negative electrode material and the electrolyte, improve the interface stability of the electrode and the electrolyte, so as to more effectively resist the corrosion of the electrolyte, reduce the volume expansion in the charging and discharging process, enhance the mechanical stability of the electrode, and improve the cycle stability and service life of the battery.

[0034] In addition, the hydrophilic groups carried by the hydrophilic polymer itself are prone to interact with the silicon material in the silicon-carbon material, and the hydrophobic chains of the small molecule auxiliary agent have a high interaction force with the carbon material in the silicon-carbon material, under the synergistic effect, the interaction force between the silicon-carbon material and the coating layer as a whole can be enhanced, which further effectively relieves the problem of volume expansion of the silicon-carbon negative electrode material, and improves the cycle stability and service life of the battery.

[0035] Therefore, the silicon-carbon negative electrode material has good dispersibility in the homogenization process, can effectively reduce the gas production, and can improve the mechanical stability of the electrode during the preparation of the electrode and the use, thereby improving the cycle stability and service life of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0037] Figure 1 The electron microscope image of the silicon-carbon negative electrode material prepared in Example 1 of the present application;

[0038] Figure 2 The dispersion effect diagram of the silicon-carbon negative electrode material prepared in the blank control example and Example 1 of the present application in water, wherein A is the dispersion effect diagram of the silicon-carbon negative electrode material of the blank control example in water, and B is the dispersion effect diagram of the silicon-carbon negative electrode material of Example 1 in water. DETAILED DESCRIPTION

[0039] In order to facilitate the understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present application can be realized in many different forms, and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the disclosure of the present application more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing specific embodiments or examples only and is not intended to be limiting. The use herein of the terms "and / or" and "at least one of" means any one of the referenced items constituting an element, combinaton of elements, propositon, or event or any combination of elements, propositions, or events with or without reference to other items stated herein or otherwise wanted.

[0041] The silicon-carbon negative electrode material provided by the application comprises a core and a coating layer coated on the surface of the core, the material of the core is silicon-carbon material, and the material of the coating layer comprises modified polymer material, the modified polymer material is obtained by reaction of hydrophilic polymer and small molecule auxiliary agent, wherein the solubility parameter of the coating layer is 10.2 J 1 / 2 ·cm -3 / 2 -45J 1 / 2 ·cm -3 / 2 The structural formula of the small molecule auxiliary agent is X-R1, X is selected from a hydrophilic reactive group, and R1 is selected from a hydrophobic chain.

[0042] The silicon-carbon negative electrode material provided by the application comprises a core and a coating layer coated on the surface of the core, the material of the core is silicon-carbon material, and the material of the coating layer comprises modified polymer material, the modified polymer material is obtained by reaction of hydrophilic polymer and small molecule auxiliary agent, wherein the solubility parameter of the coating layer is 10.2 J 1 / 2 ·cm -3 / 2 -45J 1 / 2 ·cm -3 / 2 The coating layer, on the one hand, can maintain good dispersibility of the silicon-carbon negative electrode material in the homogenization process, and simultaneously, as a protective layer of the silicon-carbon material, effectively avoids reaction of the silicon-carbon material with water, thereby effectively reducing gas production of the silicon-carbon negative electrode material, reducing loss of effective active material, and further improving cycle performance and service life of the battery; on the other hand, in the process of preparing the electrode and use, can reduce gas production caused by contact of the silicon-carbon negative electrode material with electrolyte, improve interface stability of the electrode and the electrolyte, thereby being able to more effectively resist erosion of the electrolyte, reduce volume expansion in the charging and discharging process, reduce rupture and peeling of the electrode material, enhance mechanical stability of the electrode, and improve cycle stability and service life of the battery.

[0043] In addition, the hydrophilic groups carried by the hydrophilic polymer itself are prone to interact with the silicon material in the silicon-carbon material, but the force of action with the carbon material is weak, while the hydrophobic chain of the introduced small molecule additive has a higher interaction force with the carbon material in the silicon-carbon material, so under the synergistic effect, the interaction force between the silicon-carbon material and the coating layer as a whole can be enhanced, further effectively relieving the problem of volume expansion of the silicon-carbon negative electrode material, and then improving the cycle stability and service life of the battery.

[0044] Therefore, the silicon-carbon negative electrode material has good dispersibility in the homogenization process, can effectively reduce the gas production, and can improve the mechanical stability of the electrode during the preparation of the electrode and the use, thereby improving the cycle stability and service life of the battery.

[0045] Optionally, the solubility parameter of the hydrophilic polymer is 20J 1 / 2 ·cm -3 / 2 -50J 1 / 2 ·cm -3 / 2 , specifically, the solubility parameter of the hydrophilic polymer can be 20J 1 / 2 ·cm -3 / 2 , 25J 1 / 2 ·cm -3 / 2 , 30J 1 / 2 ·cm -3 / 2 , 35J 1 / 2 ·cm -3 / 2 , 45J 1 / 2 ·cm -3 / 2 , 50J 1 / 2 ·cm -3 / 2 .

[0046] Optionally, the solubility parameter of the small molecule additive is 10J 1 / 2 ·cm -3 / 2 -30J 1 / 2 ·cm -3 / 2 , specifically, the solubility parameter of the small molecule additive can be 10J 1 / 2 ·cm -3 / 2 , 15J 1 / 2 ·cm -3 / 2 , 20J 1 / 2 ·cm -3 / 2 , 30J 1 / 2 ·cm -3 / 2 .

[0047] Optionally, the mass ratio of the hydrophilic polymer and the small molecule additive is (100-0.1):1, preferably (100-1):1, in particular, the mass ratio of the hydrophilic polymer and the small molecule additive can be 100:1, 90:1, 80:1, 70:1, 50:1, 60:1, 40:1, 30:1, 20:1, 10:1, 1:1. In this way, by adjusting the mass ratio between the hydrophilic polymer and the small molecule additive, the proportion of hydrophilic groups and hydrophobic groups on the coating layer can be adjusted, which is beneficial to inhibit the gas production of the silicon-carbon negative electrode material during the homogenization process.

[0048] Optionally, in the modified polymer material, the mass fraction of the hydrophilic polymer is greater than or equal to the mass fraction of the small molecule additive. In this way, the dispersion effect of the silicon-carbon negative electrode material during the homogenization process can be better ensured, and the gas production of the silicon-carbon negative electrode material is inhibited.

[0049] Optionally, the hydrophilic polymer is at least one selected from cationic polymers with reactive groups, anionic polymers with reactive groups, zwitterionic polymers with reactive groups, and non-ionic polymers with reactive groups. In this way, by the reaction between the reactive groups in the structure of the hydrophilic polymer and the hydrophilic reactive groups in the structure of the small molecule additive, the reaction between the hydrophilic polymer and the small molecule additive is realized, and the modified polymer material is obtained.

[0050] Further, the hydrophilic polymer is at least one selected from compounds with structures represented by formula (1)-(6),

[0051]

[0052] In formula (1), A1 is selected from N or P, B1 is selected from F - , Cl - , Br - , I - , OH - , SO4 2- , HSO4 -1 , SO3 2- , CO3 2- , HCO3 - , HCOO - , NO3 - , NO2 - , N3 - , BF4 - , PF6 - , FSI - , TFSI - , SbF6 - , TfS- , (C6F5)4B - , PO4 3- , HPO4 2- , H2PO4 - , ClO4 - , ClO3 - , FeCl4 - , AlCl4 - , ZnCl2 - , CuCl2 - , SO3 - , HPO4 - , PO4 - , O 2- , S - , R8and Y4are both absent when B1is selected from the group consisting of COO - , SO3 - , HPO4 - , PO4 - , O 2- , S - , R8and Y4are both present when B1is selected from the group consisting of COO - , SO3 10 , HPO4 11 , PO4 12 , O 13 , S 14 , at least two of R3, R4, R5, R6, R7, and R8may form a bond or a ring;

[0053] , A3is selected from the group consisting of N or P, D1is selected from the group consisting of PO4 - , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , and R 21 may form a bond or a ring;

[0054] , A4is selected from the group consisting of N or P, D2is selected from the group consisting of PO4 - , R 22 , R 23 , R 24 , R 25 , and R 26 may form a bond or a ring;

[0055] , A5is selected from the group consisting of N or P, C2is selected from the group consisting of COO - , SO3 - , HPO4- , PO4 2- , O - , S - , R 27 , R 28 , R 29 , R 30 , and R 31 , at least two of which can be bonded or annulated;

[0056] In formula (6), R 32 , and R 33 , can be bonded or annulated;

[0057] In formulae (1) to (6), R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 , R 31 , R 32 , and R 33 ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​each independently selected from a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, an alkenyl group having 3 to 30 carbon atoms, an alkynyl group having 3 to 30 carbon atoms, an aromatic group having 6 to 30 carbon atoms, a heterocyclic group having 3 to 30 carbon atoms, a heteroaromatic group having 5 to 30 carbon atoms, or, an alkyl group having 1 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, an alkenyl group having 3 to 30 carbon atoms, an alkynyl group having 3 to 30 carbon atoms, an aromatic group having 6 to 30 carbon atoms, a heterocyclic group having 3 to 30 carbon atoms, a heteroaromatic group having 5 to 30 carbon atoms, having at least one heteroatom selected from O, S, N, Si, P, or having a substituent selected from a halogen atom, a branched or straight chain hydrocarbon group having 1 to 20 carbon atoms, a branched or straight chain alkoxy group having 1 to 20 carbon atoms, a branched or straight chain cycloalkyl group having 3 to 20 carbon atoms, an aromatic group having 6 to 30 carbon atoms, a heteroaromatic group having 5 to 30 carbon atoms;

[0058] Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8, Y9, Y 10 , Y 11 , Y 12 , Y 13 , Y 14 , Y 15 , and Y 16 are each independently selected from at least one of -COOH, -SO3H, -SO2H, -COCl, -COBr, -COI, -CONH2, -NH2, -NHNH2, -NCO, -NCS, -CHO, -OH, -SH, -SeH, =O, =S, =Se;

[0059] n1, n2, n3, n4, n5, n6 are each independently selected from 14 to 14000.

[0060] Further, the hydrophilic polymer is selected from at least one of compounds having structures shown in formula (7) to formula (14), wherein, in formula (7) to formula (14), n is each selected from 14 to 14000;

[0061]

[0062]

[0063] Optionally, the relative molecular mass of the hydrophilic polymer is 1000-1000000, preferably 5000-100000, in particular, the relative molecular mass of the hydrophilic polymer can be 5000, 10000, 12000, 14900, 16800, 20000, 24000, 36600, 40000, 60000, 70000, 80000, 90000, 100000.

[0064] It should be noted that when the hydrophilic polymer is selected from two or more polymers, any two or more polymers can be copolymerized to form one or more of a random copolymer, an alternating copolymer, a block copolymer, a graft copolymer.

[0065] Optionally, X is selected from at least one of -COOH, -SO3H, -SO2H, -COCl, -COBr, -COI, -CONH2, -NH2, -NHNH2, -NCO, -NCS, -CHO, -OH, -SH, -SeH, =O, =S, =Se, preferably at least one of -COOH, -CHO, -OH, -SH. In this way, the small molecule additive can better react with the hydrophilic polymer to obtain a modified polymer material.

[0066] Optionally, R1 is selected from any one of an alkyl group with a carbon atom number of 1-30, a cycloalkyl group with a carbon atom number of 3-30, an alkenyl group with a carbon atom number of 3-30, an alkynyl group with a carbon atom number of 3-30, an aromatic group with a carbon atom number of 6-30, a heterocyclic group with a carbon atom number of 3-30, a heteroaromatic group with a carbon atom number of 5-30, preferably an alkyl group with a carbon atom number of 8-18, a cycloalkyl group with a carbon atom number of 8-18.

[0067] Optionally, the hydrophobic chain is selected from any one of an alkyl group with a carbon atom number of 1-30, a cycloalkyl group with a carbon atom number of 3-30, an alkenyl group with a carbon atom number of 3-30, an alkynyl group with a carbon atom number of 3-30, an aromatic group with a carbon atom number of 6-30, a heterocyclic group with a carbon atom number of 3-30, a heteroaromatic group with a carbon atom number of 5-30, containing at least one heteroatom or having a substituent, wherein the heteroatom is selected from at least one of O, S, N, Si, P, and the substituent is selected from any one of a halogen atom, a branched or linear hydrocarbon group with a carbon atom number of 1-20, a branched or linear alkoxy group with a carbon atom number of 1-20, a branched or linear cycloalkyl group with a carbon atom number of 3-20, an aromatic group with a carbon atom number of 6-30, a heteroaromatic group with a carbon atom number of 5-30.

[0068] In this way, the hydrophobicity of the small molecule additive can be better regulated, the interaction force between the small molecule additive and the carbon in the silicon-carbon material can be further improved, and the bonding strength between the coating layer and the silicon-carbon material can be better improved, thereby improving the structural stability of the silicon-carbon negative electrode material.

[0069] Optionally, the relative molecular mass of the small molecule additive is 30-1000, preferably 100-450, and specifically, the relative molecular mass of the small molecule additive can be 100, 120, 150, 200, 250, 300, 350, 400, or 450.

[0070] Optionally, the small molecule additive is selected from at least one of octanoic acid, n-decanal, n-hexylamine, n-heptanal, stearic acid, stearyl alcohol, and polytetrahydrofuran.

[0071] Optionally, the mass ratio of the silicon-carbon material to the material of the coating layer is 100:(0.005-100), preferably 100:(0.05-2), and specifically, the mass ratio of the silicon-carbon material to the material of the coating layer can be 100:0.05, 100:0.1, 100:0.5, 100:1, 100:1.2, 100:1.3, 100:1.4, 100:1.45, 100:1.5, 100:1.6, 100:1.8, 100:1.9, or 100:2.

[0072] Optionally, the thickness of the coating layer is 1-1000 nm, preferably 1-100 nm, and more preferably 1-20 nm, and specifically, the thickness of the coating layer can be 1 nm, 2 nm, 3 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, or 20 nm. In this way, the problem of gas generation of the silicon-carbon negative electrode material can be reduced while excellent electrical conductivity is achieved.

[0073] Optionally, the median particle size of the silicon-carbon material is 1-20 μm, preferably 1-10 μm, and specifically, the median particle size of the silicon-carbon material can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0074] Optionally, the material of the coating layer further comprises a conductive agent. In this way, a conductive network can be better constructed, and the electrical conductivity of the silicon-carbon negative electrode material can be improved.

[0075] In one embodiment, the mass ratio of the conductive agent to the modified polymer material is (0.001-1):1. Specifically, the mass ratio of the conductive agent to the modified polymer material can be 0.001:1, 0.01:1, 0.2:1, 0.3:1, 0.5:1, 0.7:1, 0.9:1, or 1:1.

[0076] In one embodiment, the conductive agent includes, but is not limited to, at least one of graphene, acetylene black, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, flake graphite, polyaniline, polypyrrole, polyacetylene, polythiophene, and poly(3,4-ethylenedioxythiophene / polystyrene sulfonate) (PEDOT:PSS).

[0077] It should be noted that, in this invention, the silicon-carbon material used as the core material refers to a class of compound materials composed of silicon and carbon elements. This silicon-carbon material can be prepared by chemical vapor deposition, sol-gel method, high-temperature pyrolysis method, mechanical ball milling method, hydrothermal synthesis method, and electrospinning method, or it can be commercially available.

[0078] Specifically, the silicon-carbon material can be selected from silicon-carbon materials formed in the following ways, such as silicon-carbon formed by porous carbon deposition on silicon, silicon-carbon formed by porous silicon deposition on carbon, silicon-carbon composite material formed by direct combination of silicon and carbon, silicon-carbon formed by carbonization of polymer-coated silicon, and silicon-carbon formed by physical ball milling of silicon powder and carbon or graphite.

[0079] Meanwhile, the present invention also provides a method for preparing silicon-carbon anode material, comprising: dispersing silicon-carbon material, hydrophilic polymer and small molecule additives in a solvent to prepare a mixture, and then drying the mixture to obtain silicon-carbon anode material.

[0080] Optionally, the mass ratio of the silicon-carbon material, the hydrophilic polymer, and the small molecule additive is (60-100):(0.01-20):(0.01-20), preferably (80-95):(0.1-10):(0.1-10). Specifically, the mass ratio of the silicon-carbon material, the hydrophilic polymer, and the small molecule additive can be 80:0.1:0.1, 82:0.2:0.2, 85:1:1, 88:3:3, 90:7:7, or 95:10:10. This configuration allows the hydrophilic polymer and the small molecule additive to better form a coating layer with a specific ratio of hydrophilic and hydrophobic groups on the surface of the silicon-carbon material through in-situ reaction, thereby helping to reduce gas generation in the silicon-carbon anode material.

[0081] Optionally, the step of preparing the mixture by dispersing the silicon-carbon material, the hydrophilic polymer and the small molecule additive in the solvent further comprises adding a conductive agent, wherein the mass ratio of the conductive agent to the silicon-carbon material is (0.001-0.25):1, and specifically, the mass ratio of the conductive agent to the silicon-carbon material can be 0.001:1, 0.01:1, 0.1:1, 0.15:1, 0.2:1 or 0.25:1.

[0082] Further, the conductive agent is at least one of graphene, acetylene black, carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, flake graphite, polyaniline, polypyrrole, polyacetylene, polythiophene, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). In this way, the conductive agent can be better dispersed in the coating layer, thereby further constructing a better conductive network and improving the uniformity of the conductivity of the coating layer.

[0083] Optionally, the drying process comprises spray drying and vacuum drying, wherein the spray drying temperature is 100-300℃, and specifically, the spray drying temperature can be 100℃, 110℃, 120℃, 150℃, 160℃, 220℃, 250℃, 280℃ or 300℃; the spray drying time is 0.5-10h, and specifically, the spray drying time can be 0.5h, 1h, 1.5h, 2h, 4h, 5h, 7h, 8h, 9h or 10h; the vacuum drying temperature is 50-250℃, and specifically, the vacuum drying temperature can be 50℃, 60℃, 70℃, 100℃, 120℃, 150℃, 170℃, 200℃ or 250℃; and the vacuum drying time is 1-10h, and specifically, the vacuum drying time can be 1h, 2h, 4h, 5h, 7h, 8h, 9h or 10h.

[0084] Specifically, the mixture is first subjected to spray drying to obtain a crude product, and then the crude product is subjected to vacuum drying to obtain the silicon-carbon negative electrode material.

[0085] In an embodiment, before the drying process, the mixture is further subjected to mechanical stirring at room temperature for 15-60min, and specifically, the mechanical stirring time can be 15min, 20min, 25min, 40min, 55min or 60min.

[0086] In an embodiment, the solvent is selected from an organic solvent or a mixed solvent comprising an organic solvent and water, and preferably, the solvent is a mixed solvent comprising an organic solvent and water, wherein the volume ratio of the organic solvent to the water in the mixed solvent is 1:0.01-0.01:1, and specifically, the volume ratio can be 1:0.01 or 0.01:1.

[0087] The organic solvent is selected from at least one of methanol, ethanol, formic acid, acetic acid, methyl ethyl ketone, acetone, pyridine, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoramide, ethylene glycol, N-methyl pyrrolidone and glycerol, and the mixed solvent is preferably a mixed solvent of acetone and water or a mixed solvent of ethanol and water.

[0088] The preparation method of the silicon-carbon negative electrode material provided by the application introduces a small-molecule additive to modify the hydrophilic polymer in situ, controls the hydrophilic and hydrophobic properties of the hydrophilic polymer, and makes the solubility parameter of the obtained coating layer 10.2 J 1 / 2 ·cm -3 / 2 -45J 1 / 2 ·cm -3 / 2 , and the hydrophilic groups and the hydrophobic groups have a specific ratio, so that the prepared silicon-carbon negative electrode material has good dispersibility in the homogenization process, can effectively reduce the gas production, can improve the mechanical stability of the electrode in the preparation of the electrode and the use process, thereby improving the cycle stability and service life of the battery, and the method is simple and suitable for industrial production.

[0089] In addition, the application also provides a negative electrode sheet prepared by using the silicon-carbon negative electrode material.

[0090] In addition, the application also provides a negative electrode sheet prepared by using the silicon-carbon negative electrode material.

[0091] In an embodiment, the battery can be a lithium battery.

[0092] In the following, the core-shell structure silicon-carbon negative electrode material, the preparation method and the application thereof will be further described through the following specific examples.

[0093] The polymers a, b, c, d, e, f, g and h involved in the examples 1-8 and the comparative examples 1-3 in the application respectively correspond to the compounds with the structures shown in the following formula (7)-(14):

[0094]

[0095] Meanwhile, the solubility parameter (SP) of the coating layer in the silicon-carbon anode material involved in Examples 1-8 and Comparative Examples 1-3 of this invention can be obtained by the following calculation formula: SP=φ1δ1+φ2δ2, where φ1 and φ2 represent the mass fractions of the hydrophilic polymer and the small molecule additive, respectively, and δ1 and δ2 represent the solubility parameters corresponding to the hydrophilic polymer and the small molecule additive, respectively.

[0096] Example 1

[0097] 50g of silicon carbide material (average particle size 6.5μm) and 1g of polymer a (solubility parameter 28.1J) were mixed. 1 / 2 ·cm -3 / 2 A mixture of 0.3 g of octanoic acid (with a relative molecular mass of 20000 and n = 10⁶) and 0.5 g of graphene was dispersed in 500 mL of a mixed solvent of water and ethanol (volume ratio of water to ethanol: 80:20) to obtain a mixture. The mixture was mechanically stirred at room temperature for 30 min, then spray-dried at 150 °C for 2 h to obtain a crude product. Finally, the crude product was dried under vacuum at 130 °C for 3 h to obtain a silicon-carbon anode material. The solubility parameter of the coating layer in this silicon-carbon anode material was calculated to be 23.2 J. 1 / 2 ·cm -3 / 2 .

[0098] The silicon-carbon anode material prepared in Example 1 was characterized using transmission electron microscopy, as shown in the electron micrographs. Figure 1 As shown, from Figure 1 As can be seen, the modified polymer material is uniformly dispersed on the surface of the silicon-carbon material.

[0099] Example 2

[0100] Example 2 differs from Example 1 only in that polymer b (solubility parameter 32.3 J) is used. 1 / 2 ·cm -3 / 2 Polymer a was replaced by a polymer (with a relative molecular mass of 15000 and n of 56), octanoic acid was replaced by decanal, and graphene was replaced by acetylene black, with all other conditions remaining the same, to obtain a silicon-carbon anode material. The solubility parameter of the coating layer in this silicon-carbon anode material was calculated to be 25.3 J. 1 / 2 ·cm -3 / 2 .

[0101] Example 3

[0102] Example 3 differs from Example 1 only in that 1.5g of polymer c (solution parameter 26.3J) was used. 1 / 2 ·cm -3 / 2, the relative molecular mass is 24100, n is 131), 0.1 g of n-hexylamine is used to replace octanoic acid, 0.6 g of multi-walled carbon nanotubes is used to replace graphene, and the remaining conditions are the same, to obtain a silicon-carbon negative electrode material, and the solubility parameter of the coating layer in the silicon-carbon negative electrode material is calculated to be 21.6 J 1 / 2 ·cm -3 / 2 .

[0103] Example 4

[0104] Example 4 is compared with Example 1, and the difference is that polymer d (the solubility parameter is 24.3 J 1 / 2 ·cm -3 / 2 , the relative molecular mass is 24100, n is 131) is used to replace polymer a, 0.1 g of n-hexylamine is used to replace octanoic acid, 0.6 g of multi-walled carbon nanotubes is used to replace graphene, and the remaining conditions are the same, to obtain a silicon-carbon negative electrode material, and the solubility parameter of the coating layer in the silicon-carbon negative electrode material is calculated to be 21.6 J 1 / 2 ·cm -3 / 2 .

[0105] Example 5

[0106] 50 g of silicon-carbon material (the average particle size is 7 μm), 2 g of polymer e (the solubility parameter is 25.4 J 1 / 2 ·cm -3 / 2 , the relative molecular mass is 10000, n is 48), 0.5 g of stearyl alcohol, and 0.3 g of 3,4-ethylenedioxythiophene / polystyrene sulfonate are dispersed in 500 mL of a mixed solvent mixed by water and acetone (the volume ratio of water to acetone is 55:45) to obtain a mixture; the mixture is mechanically stirred at room temperature for 20 min, and then spray dried at 120°C for 2 h to obtain a crude product, and finally the crude product is dried at 150°C under vacuum for 3 h to obtain a silicon-carbon negative electrode material, and the solubility parameter of the coating layer in the silicon-carbon negative electrode material is calculated to be 22.7 J 1 / 2 ·cm -3 / 2 .

[0107] Example 6

[0108] 60 g of silicon-carbon material (the average particle size is 7.5 μm), 1.5 g of polymer f (the solubility parameter is 27.8 J 1 / 2 ·cm -3 / 2, the relative molecular mass of the polymer h is 16800, n is 382), 0.7 g of stearic acid, and 0.6 g of carbon black are dispersed in 500 mL of a mixed solvent of water and ethanol (the volume ratio of water to ethanol is 10:90) to obtain a mixture; the mixture is mechanically stirred at room temperature for 35 min, and then spray dried at 120°C for 3 h to obtain a crude product, and finally the crude product is dried at 150°C under vacuum for 3 h to obtain a silicon-carbon negative electrode material, and the solubility parameter of the coating layer in the silicon-carbon negative electrode material is calculated to be 22.1 J 1 / 2 ·cm -3 / 2 .

[0109] Example 7

[0110] 50 g of a silicon-carbon material (the average particle size is 8 μm), 1 g of a polymer g (the solubility parameter is 28.7 J 1 / 2 ·cm -3 / 2 , the relative molecular mass of the polymer g is 12100, n is 53), 0.2 g of n-heptanal, and 0.3 g of polypyrrole are dispersed in 500 mL of a mixed solvent of water and acetone (the volume ratio of water to acetone is 20:80) to obtain a mixture; the mixture is mechanically stirred at room temperature for 20 min, and then spray dried at 120°C to obtain a crude product, and finally the crude product is dried at 150°C under vacuum for 3 h to obtain a silicon-carbon negative electrode material, and the solubility parameter of the coating layer in the silicon-carbon negative electrode material is calculated to be 25.9 J 1 / 2 ·cm -3 / 2 .

[0111] Example 8

[0112] 60 g of a silicon-carbon material (the average particle size is 7.8 μm), 1.5 g of a polymer h (the solubility parameter is 29.1 J 1 / 2 ·cm -3 / 2 , the relative molecular mass of the polymer h is 16800, n is 382), 0.7 g of stearic acid, and 0.6 g of carbon black are dispersed in 500 mL of a mixed solvent of water and ethanol (the volume ratio of water to ethanol is 10:90) to obtain a mixture; the mixture is mechanically stirred at room temperature for 35 min, and then spray dried at 120°C for 3 h to obtain a crude product, and finally the crude product is dried at 150°C under vacuum for 3 h to obtain a silicon-carbon negative electrode material, and the solubility parameter of the coating layer in the silicon-carbon negative electrode material is calculated to be 22.1 J 1 / 2 ·cm -3 / 2 .

[0113] Comparative Example 1

[0114] Comparative Example 1 is the same as Example 1 except that the step of preparing the mixture does not include the addition of octanoic acid. The calculated solubility parameter of the coating layer in the silicon-carbon negative electrode material is 28.1 J 1 / 2 · cm -3 / 2 .

[0115] Comparative Example 2

[0116] Comparative Example 2 is the same as Example 1 except that the step of preparing the mixture uses acetic acid instead of octanoic acid. The calculated solubility parameter of the coating layer in the silicon-carbon negative electrode material is 27.9 J 1 / 2 · cm -3 / 2 .

[0117] Comparative Example 3

[0118] Comparative Example 3 is the same as Example 1 except that the step of preparing the mixture uses octane instead of octanoic acid. The calculated solubility parameter of the coating layer in the silicon-carbon negative electrode material is 28.2 J 1 / 2 · cm -3 / 2 .

[0119] Example 1 is used as a blank control. The silicon-carbon negative electrode materials prepared in Examples 1-8 and Comparative Examples 1-3, as well as the blank control, are subjected to gas production testing and soft pack battery testing.

[0120] The gas production testing method is as follows: 5 g of the material to be tested and 50 g of water are added to a sealed bottle, and the mixture is fully dissolved by centrifugal stirring. The mixture is then placed in a 25°C constant temperature room, and the amount of gas (H2) produced in 24 hours on the first day, the third day, the fifth day, and the seventh day is tested. The results are shown in Table 1.

[0121] Table 1

[0122]

[0123] As can be seen from Table 1, the blank control silicon-carbon material without a polymer coating has a gas production of about 2.34-2.78 CC / kg / day. Comparative Example 1 is a silicon-carbon material coated with a hydrophilic polymer. Compared with the blank control, the hydrophilic polymer coating modification results in a sharp increase in the amount of gas produced (3.65-4.99 CC / kg / day) due to the corresponding solubility parameter value of 28.1 J 1 / 2 · cm -3 / 2 . Example 1 is a silicon-carbon material coated with a modified polymer material formed by the in-situ reaction of a hydrophilic polymer and a small molecule additive. The remaining hydrophobic segment of the small molecule additive structure effectively reduces the overall hydrophilicity of the polymer after the in-situ reaction of the hydrophilic reaction group in the structure (the corresponding solubility parameter value decreases to 23.2 J1 / 2 · cm -3 / 2 ), thus alleviating the high gas production due to the introduction of hydrophilic polymers, which is further verified by Examples 2-8.

[0124] The soft package test method is as follows: the material to be tested is doped with 80% artificial graphite as a negative electrode; NCM811 ternary material is used as a positive electrode material, LiPF6 is used as a lithium salt, a mixed solvent of EC and DEC in a volume ratio of 1:1 is used as an electrolyte solvent, and Celgard 2400 film is used as a separator to prepare a soft package lithium ion battery, and a cycle test (200 cycle capacity retention rate) is performed. The test conditions are: voltage range 2.5V-4.2V, charge and discharge 1C / 1C. The cycle test results are shown in Table 2.

[0125] Table 2

[0126] 200 % capacity retention Blank control example 89.3 Example 1 94.3 Example 2 93.7 Example 3 93.9 Example 4 95.8 Example 5 95.2 Example 6 96.3 Example 7 98.2 Example 8 94.3 Comparative example 1 92.5 Comparative example 2 93.3 Comparative example 3 93.0

[0127] As can be seen from Table 2, the blank control example, Comparative Example 1 is a hydrophilic polymer coated silicon-carbon material, and the 200 cycle capacity retention rates thereof are 89.3% and 92.5%, respectively. Example 1 is in-situ modified based on Comparative Example 1, which effectively improves the cycle stability of the battery (200 cycle capacity retention rate is 94.3%). At the same time, it can also be seen from Examples 2-8 that the hydrophilic-hydrophobic performance of the hydrophilic polymer can be effectively improved by in-situ modification of the small molecule additive, which can effectively improve the cycle stability of the silicon-carbon negative electrode material.

[0128] In addition, from the data of Example 1 and Comparative Examples 2-3 in Table 2, it can be seen that the structure of the small molecule additive in the present application will affect the hydrophilic-hydrophobic performance of the coating layer and the cycle stability of the battery.

[0129] The dispersion test method is as follows: the silicon-carbon negative electrode material obtained from the blank control example and Example 1 is respectively weighed 5g and put into 80mL water for stirring and dispersion, and the dispersion results are shown in Figure 2 From Figure 2 it can be clearly seen that, since the carbon layer on the surface of the blank control example is a hydrophobic structure, the dispersion in water is poor, and the corresponding gas production value is also low, but this characteristic greatly affects the subsequent processing technology and battery performance; while Example 1, after being coated by the hydrophilic polymer and the small molecule additive, the prepared silicon-carbon negative electrode material is dispersed uniformly and stably in water.

[0130] It can be seen that the hydrophilic polymer with a specific solubility parameter value is in-situ modified by introducing a small molecule additive with a specific structure, the hydrophilic polymer is regulated to have hydrophilic and hydrophobic properties, a coating layer with a specific proportion of hydrophilic groups and hydrophobic groups is formed, and the solubility parameter value of the coating layer is controlled, so that the prepared silicon-carbon negative electrode material not only has good dispersibility in the homogenization process, but also can effectively reduce the gas production, and in the process of preparing the electrode and using, the mechanical stability of the electrode can be improved, thereby improving the cycle stability and service life of the battery.

[0131] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present disclosure.

[0132] The above-described embodiments only express several implementation manners of the present application, the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A silicon-carbon negative electrode material, characterized in that, The silicon-carbon negative electrode material comprises a core and a coating layer coated on the surface of the core, the material of the core is a silicon-carbon material, the material of the coating layer comprises a modified polymer material, the modified polymer material is obtained by in-situ reaction of a hydrophilic polymer and a small molecule auxiliary agent, wherein the solubility parameter of the coating layer is 10.2 J 1 / 2 ·cm -3 / 2 -45 J 1 / 2 ·cm -3 / 2 , and the structural formula of the small molecule auxiliary agent is X-R1, X is selected from a hydrophilic reactive group, and R1 is selected from a hydrophobic chain. X is at least one selected from -COOH, -SO3H, -SO2H, -COCl, -COBr, -COI, -CONH2, -NH2, -NHNH2, -NCO, -NCS, -CHO, -OH, -SH, -SeH, =O, =S, =Se, R1 is any one selected from alkyl with carbon number of 8-18, cycloalkyl with carbon number of 3-30, alkenyl with carbon number of 3-30, alkynyl with carbon number of 3-30, aromatic group with carbon number of 6-30, heterocyclic group with carbon number of 3-30, heteroaromatic group with carbon number of 5-30, or any one selected from alkyl with carbon number of 1-30 containing at least one heteroatom or having a substituent, cycloalkyl with carbon number of 3-30, alkenyl with carbon number of 3-30, alkynyl with carbon number of 3-30, aromatic group with carbon number of 6-30, heterocyclic group with carbon number of 3-30, heteroaromatic group with carbon number of 5-30, wherein the heteroatom is at least one selected from O, S, N, Si, P, and the substituent is any one selected from halogen atom, branched or straight chain hydrocarbon group with carbon number of 1-20, branched or straight chain alkoxy group with carbon number of 1-20, branched or straight chain cycloalkyl group with carbon number of 3-20, aromatic group with carbon number of 6-30, heteroaromatic group with carbon number of 5-30.

2. The silicon-carbon negative electrode material of claim 1, wherein, said hydrophilic polymer has a solubility parameter of 20 J 1 / 2 · cm -3 / 2 - 50 J 1 / 2 · cm -3 / 2 said small molecule coagent has a solubility parameter of 10 J 1 / 2 · cm -3 / 2 - 30 J 1 / 2 · cm -3 / 2 .

3. The silicon-carbon negative electrode material of claim 1, wherein, The mass fraction of the hydrophilic polymer in the modified polymer material is greater than or equal to the mass fraction of the small molecule additive.

4. The silicon-carbon negative electrode material of claim 1, wherein, The hydrophilic polymer is at least one selected from compounds with structures shown in formula (1)-formula (6), 、 、 、 、 、 ； In equation (1), A1 is selected from N or P, and B1 is selected from F. - Cl - ,Br - I - OH - SO4 2- HSO4 -1 SO3 2- CO3 2- HCO3 - HCOO - NO3 - NO2 - N3 - BF4 - PF6 - FSI - TFSI - SbF6 - ,TfS - (C6F5)4B - PO4 3- HPO4 2- H2PO4 - ClO4 - ClO3 - FeCl4 - AlCl4 - ZnCl2 - CuCl2 - When B1 is selected from COO, neither R8 nor Y4 exists; - SO3 - HPO4 - PO4 2- O - S - In any of the following cases, both R8 and Y4 are present; at least two of R3, R4, R5, R6, R7, and R8 can form bonds or rings; in equation (2), A2 is selected from N or P, and C1 is selected from COO. - SO3 - HPO4 - PO4 2- O - S - Any of the following, R9, R 10 R 11 R 12 R 13 and R 14 At least two of them can form bonds or rings; in equation (3), A3 is selected from N or P, and D1 is selected from PO4. - R 15 R 16 R 17 , R 18 , R 19 , R 20 , and R 21 may be bonded or in a ring between at least two of R - , R 22 , R 23 , R 24 , R 25 , and R 26 may be bonded or in a ring between at least two of R - , SO3 - , HPO4 - , PO4 2- , O - , S - , R 27 , R 28 , R 29 , R 30 , and R 31 may be bonded or in a ring between at least two of R 32 and R 33 may be bonded or in a ring. In formula (1) - formula (6), R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 , R 28 , R 29 , R 30 , R 31 , R 32 and R 33 are each independently selected from any one of a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, an alkenyl group having 3 to 30 carbon atoms, an alkynyl group having 3 to 30 carbon atoms, an aromatic group having 6 to 30 carbon atoms, a heterocyclic group having 3 to 30 carbon atoms, a heteroaromatic group having 5 to 30 carbon atoms, or, selected from any one of an alkyl group having 1 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, an alkenyl group having 3 to 30 carbon atoms, an alkynyl group having 3 to 30 carbon atoms, an aromatic group having 6 to 30 carbon atoms, a heterocyclic group having 3 to 30 carbon atoms, a heteroaromatic group having 5 to 30 carbon atoms having at least one heteroatom or a substituent, wherein the heteroatom is selected from at least one of O, S, N, Si, P, and the substituent is selected from any one of a halogen atom, a branched or straight chain hydrocarbon group having 1 to 20 carbon atoms, a branched or straight chain alkoxy group having 1 to 20 carbon atoms, a branched or straight chain cycloalkyl group having 3 to 20 carbon atoms, an aromatic group having 6 to 30 carbon atoms, a heteroaromatic group having 5 to 30 carbon atoms; Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8, Y9, Y 10 , Y 11 , Y 12 , Y 13 , Y 14 , Y 15 , and Y 16 are each independently selected from at least one of -COOH, -SO3H, -SO2H, -COCl, -COBr, -COI, -CONH2, -NH2, -NHNH2, -NCO, -NCS, -CHO, -OH, -SH, -SeH, =0, =S, =Se; n1, n2, n3, n4, n5, n6 are independently selected from 14-14000.

5. The silicon-carbon negative electrode material of claim 4, wherein, The hydrophilic polymer is at least one selected from compounds with structures shown in formula (7)-formula (14), wherein n in formula (7)-formula (14) is selected from 14-14000; 、 、 、 、 、 、 、 。 6. The silicon-carbon negative electrode material of claim 4, wherein, The relative molecular mass of the hydrophilic polymer is 1000-1000000.

7. The silicon-carbon negative electrode material of claim 1, wherein, The relative molecular mass of the small molecule additive is 30-1000. X is at least one selected from -COOH, -CHO, -OH, -SH, and R1 is any one selected from alkyl with carbon number of 8-18, cycloalkyl with carbon number of 8-18.

8. The silicon-carbon negative electrode material of claim 1, wherein, The small molecule additive is at least one selected from octanoic acid, n-decanal, n-hexylamine, n-heptanal, stearic acid, stearyl alcohol, and polytetrahydrofuran.

9. The silicon-carbon negative electrode material of claim 1, wherein, The mass ratio of the silicon-carbon material to the material of the coating layer is 100:(0.005-100). The median particle size of the silicon-carbon material is 1-20 microns. The thickness of the coating layer is 1-1000 nanometers.

10. The silicon-carbon negative electrode material of claim 1, wherein, The material of the coating layer further comprises a conductive agent.

11. A method of producing a silicon-carbon negative electrode material as claimed in any one of claims 1 to 10, characterized in that, The method comprises: The silicon-carbon material, the hydrophilic polymer, and the small molecule additive are dispersed in a solvent to prepare a mixture, and then the mixture is dried to obtain the silicon-carbon negative electrode material.

12. The method of claim 11, wherein the silicon-carbon negative electrode material is prepared by a process comprising: The mass ratio between the silicon-carbon material, the hydrophilic polymer and the small molecule additive is (60-100):(0.01-20):(0.01-20); And / or, in the step of preparing the mixture by dispersing the silicon-carbon material, the hydrophilic polymer and the small molecule additive in a solvent, an electrically conductive agent is also added, and the mass ratio between the electrically conductive agent and the silicon-carbon material is (0.001-0.25):

1.

13. The method of claim 11, wherein the silicon-carbon negative electrode material is prepared by a process comprising: mixing a silicon source and a carbon source to form a mixture; and heating the mixture to form the silicon-carbon negative electrode material. The drying treatment includes spray drying and vacuum drying, wherein the spray drying temperature is 100-300°C, the spray drying time is 0.5-10h, the vacuum drying temperature is 50-250°C, and the vacuum drying time is 1-10h. 14.A negative electrode sheet prepared by using the silicon-carbon negative electrode material according to any one of claims 1-10. 15.A battery prepared by using the negative electrode sheet according to claim 14.

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