A lithium ion battery negative electrode material, a preparation method thereof and a lithium ion battery

Abstract

The present application belongs to the technical field of lithium ion batteries, and more particularly relates to a lithium ion battery negative electrode material, a preparation method thereof and a lithium ion battery. The lithium ion battery negative electrode material of the present application utilizes graphene oxide (GO) and a crosslinking agent to react on the surface of Si / C active material and obtains a self-adaptive layered material after reduction, forming a self-adaptive elastic buffer space. Compared with Si / C electrode material obtained by coating on copper foil using a traditional adhesive sodium carboxymethyl cellulose (CMC), the lithium ion battery negative electrode material of the present application can better alleviate the capacity decline of Si / C electrode caused by volume expansion, so that it has a higher specific capacity and excellent cycle stability. The lithium ion battery negative electrode material of the preferred embodiment of the present application can maintain a specific capacity of 550 mAh g ‑1 at 0.5 A g ‑1 current density after 200 cycles, so that it has important application value in high-capacity energy storage devices.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a lithium-ion battery anode material, its preparation method, and a lithium-ion battery; more specifically, relating to a reduced graphene oxide-embedded carbon-coated nano-silicon sphere lithium-ion battery anode material, its preparation method, and a lithium-ion battery. Background Technology

[0002] Lithium-ion rechargeable batteries have attracted much attention due to their advantages such as high energy density, wide operating voltage range, long service life, and environmental friendliness. Silicon anode materials, due to their high theoretical specific capacity (4200 mA g / g), are also noteworthy. -1 Silicon's abundant reserves and high cycle stability make it a promising candidate for lithium-ion batteries. However, the large volume expansion of silicon anode materials during ion insertion / extraction processes leads to poor cycle stability, limiting its development as anode materials for lithium-ion batteries. Sodium carboxymethyl cellulose (CMC), a widely used anode binder, suffers from volume expansion during lithium insertion / extraction reactions, causing active materials and conductive agents to pulverize and detach, further leading to separation of the active material and copper current collector, resulting in a decrease in battery capacity. Therefore, developing silicon anode materials with high cycle stability and no binder is of great significance for high-capacity and high-energy-density lithium-ion battery energy storage devices. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a lithium-ion battery anode material made of reduced graphene oxide-embedded carbon-coated silicon nanospheres, its preparation method, and a lithium-ion battery. This invention solves the technical problem that anode materials prepared by bonding graphene and Si / C together with binders using existing technologies are easily affected by the volume expansion during the lithium insertion / extraction reaction of the anode material, causing active materials, conductive agents, etc., to pulverize and fall off, further leading to a decrease in battery capacity.

[0004] To achieve the above objectives, the present invention provides an adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanosphere lithium-ion battery anode material, which comprises an adaptive three-dimensional layered structure formed by the cross-linking reaction and reduction of graphene oxide and cross-linking agent on the surface of carbon-coated silicon nanospheres; the structure has an elastic buffer space, which can effectively alleviate the volume expansion of the anode material during charging and discharging, and improve the stability of the anode material.

[0005] Preferably, the crosslinking agent is an isocyanate compound, and the crosslinking reaction is a crosslinking reaction between the carboxyl functional groups contained in graphene oxide and the hydroxyl functional groups of the crosslinking agent; the negative electrode material also contains a thickener, which is a polymer containing at least two hydroxyl groups.

[0006] Preferably, the mass percentage of silicon in the negative electrode material is 20-50%.

[0007] According to another aspect of the present invention, a method for preparing the lithium-ion battery anode material is provided, comprising the following steps:

[0008] (1) Graphene oxide was dispersed in an organic solvent and mixed with carbon-coated nano-silicon and a thickener and stirred continuously to obtain a precursor;

[0009] (2) The precursor described in step (1) is mixed with a crosslinking agent and a catalyst, and stirred to allow the graphene oxide to undergo a crosslinking reaction with the crosslinking agent to obtain a crosslinking reaction product;

[0010] (3) The crosslinking reaction product described in step (2) is coated onto copper foil and dried to obtain GO-Si / C composite material;

[0011] (4) The GO-Si / C composite material described in step (3) is thermally reduced to obtain the adaptive three-dimensional layered reduced graphene oxide embedded carbon-coated nano-silicon sphere lithium-ion battery anode material.

[0012] Preferably, the organic solvent in step (1) is one or more of N,N-dimethylformamide, toluene, ethyl acetate and xylene.

[0013] Preferably, in step (2), the mass percentage of carbon-coated nano-silicon in the crosslinking reaction product is 20-50%, the mass percentage of the thickener is 0.1-0.5%, and the mass ratio of graphene oxide to the thickener is (2-5):(0.1-0.5).

[0014] Preferably, the mass ratio of the graphene oxide to the crosslinking agent is 1:2 to 5.

[0015] Preferably, the drying process in step (3) involves a drying temperature of 50–120°C and a drying time of 1–5 hours.

[0016] Preferably, the thermal reduction in step (4) specifically involves: heating the GO-Si / C composite material obtained in step (3) to 100-400°C in a reducing atmosphere at a heating rate of 3-5°C / min and holding it at that temperature for 2-4 hours, and then cooling it to room temperature to obtain the adaptive three-dimensional layered reduced graphene oxide embedded carbon-coated nano-silicon sphere lithium-ion battery anode material.

[0017] According to another aspect of the present invention, a lithium-ion battery is provided, comprising a negative electrode sheet, wherein the negative electrode active material used in the negative electrode sheet contains the aforementioned adaptive three-dimensional layered reduced graphene oxide embedded carbon-coated nano-silicon sphere lithium-ion battery negative electrode material.

[0018] In summary, compared with the prior art, the above-described technical solutions conceived by this invention have the following advantages:

[0019] Beneficial effects:

[0020] (1) The present invention provides a reduced graphene oxide-embedded carbon-coated silicon nanosphere lithium-ion battery anode material. This material utilizes GO and a crosslinking agent to react and reduce the Si / C active material surface, resulting in an adaptive layered material that forms an adaptive elastic buffer space. Compared to Si / C anode materials obtained by traditional CMC bonding, this material better mitigates the capacity decrease caused by Si / C volume expansion, resulting in higher specific capacity and excellent cycle stability. In the preferred embodiment of the present invention, the lithium-ion battery anode material is used in applications with a specific capacity of 0.5 A g. -1 After 200 cycles at the current density, it can still maintain 550mAh g. -1 Its specific capacity makes it of great value in high-capacity energy storage devices.

[0021] (2) The present invention first mixes graphene oxide dispersed in a solvent with carbon-coated nano-silicon (abbreviated as Si / C in the specification of the present invention) and a thickener, then adds a crosslinking agent, then coats the crosslinking reaction product on a copper foil and dries it, and finally thermally reduces it to obtain a reduced graphene oxide-embedded carbon-coated nano-silicon sphere lithium-ion battery anode material. The preparation method is simple and easy to scale up.

[0022] (3) This invention utilizes GO and crosslinking agent to react and reduce on the surface of Si / C active material to obtain an adaptive layered material, forming an adaptive elastic buffer space. The spacing of the buffer space can be adjusted by the length of the crosslinking agent molecular chain, providing experimental ideas for the development of subsequent battery anode materials. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the preparation of adaptive three-dimensional layered reduced graphene oxide embedded carbon-coated nano-silicon spheres (rGO-Si / C) lithium-ion battery anode material according to the present invention;

[0024] Figure 2 This is a schematic diagram of the process and structure for preparing the adaptive three-dimensional layered reduced graphene oxide embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material in Example 1 of the present invention;

[0025] Figure 3 This is a SEM image of the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in Example 1 of this invention, on a 1 μm scale.

[0026] Figure 4This is a SEM image of the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in Example 1 of this invention, under a 500 nm scale.

[0027] Figure 5 This is an X-ray diffraction pattern of the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in Example 1 of this invention;

[0028] Figure 6 This is a cycle performance diagram of the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in Example 1 of this invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] This invention provides an adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanosphere lithium-ion battery anode material, which comprises an adaptive three-dimensional layered structure formed by the cross-linking reaction and reduction of graphene oxide and cross-linking agent on the surface of carbon-coated silicon nanospheres; the structure has an elastic buffer space, which can effectively alleviate the volume expansion of the anode material during charging and discharging, and improve the stability of the anode material.

[0031] In some embodiments, the crosslinking agent is an isocyanate compound. Experiments have shown that using isocyanate compounds as crosslinking agents results in better film formation compared to other crosslinking agents containing hydroxyl groups. The crosslinking reaction is a crosslinking reaction between the carboxyl functional groups contained in graphene oxide and the hydroxyl groups of the crosslinking agent. The negative electrode material also contains a thickener, which is a polymer containing at least two hydroxyl groups.

[0032] In some embodiments, the crosslinking agent is one or more of hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (TDI), and toluene diisocyanate (MDI); the thickener is one or more of polyethylene glycol, gum arabic, and sodium caseinate; and the molecular weight of the polyethylene glycol can be 2,000-500,000.

[0033] In some embodiments, the mass percentage of silicon in the negative electrode material is 20-50%.

[0034] This invention also provides a method for preparing the lithium-ion battery anode material, such as... Figure 1As shown, it includes the following steps:

[0035] (1) Graphene oxide was dispersed in a solvent and mixed with carbon-coated nano-silicon and a thickener and stirred continuously to obtain a precursor;

[0036] (2) The precursor described in step (1) is mixed with a crosslinking agent and a catalyst, and stirred to allow the graphene oxide to undergo a crosslinking reaction with the crosslinking agent to obtain a crosslinking reaction product;

[0037] (3) The crosslinking reaction product described in step (2) is coated onto copper foil and dried to obtain GO-Si / C composite material;

[0038] (4) The GO-Si / C composite material described in step (3) is thermally reduced to obtain the adaptive three-dimensional layered reduced graphene oxide embedded carbon-coated nano-silicon sphere lithium-ion battery anode material.

[0039] Step (1) can be performed using any solvent capable of dissolving graphene oxide, including but not limited to one or more of N,N-dimethylformamide, toluene, ethyl acetate and xylene.

[0040] In some embodiments, the mass percentage of the carbon-coated nano-silicon in the crosslinking reaction product of step (2) is 20-50%, the mass percentage of the thickener is 0.1-0.5%, the mass ratio of graphene oxide to the crosslinking agent is 1:2-5, and the mass ratio of graphene oxide to the thickener is (2-5):(0.1-0.5). The catalyst is used to catalyze the crosslinking reaction of graphene oxide and the crosslinking agent, and the catalyst is one or more of triethylamine, ethylenediamine, and 1,3-propylenediamine. The mass ratio of the catalyst to the crosslinking agent is 1-1.5:1.

[0041] This invention first mixes graphene oxide dispersed in a solvent with carbon-coated nano-silicon (abbreviated as Si / C in this specification) and a thickener, and then adds a crosslinking agent. The purpose of the thickener is to increase the viscosity of the precursor to ensure that the crosslinking reaction product has good film-forming properties on the copper foil. Step (3) involves coating the crosslinking reaction product onto the copper foil and drying it. The purpose of drying is, on the one hand, to remove the organic solvent, and on the other hand, to promote the complete reaction between the crosslinking agent and GO under heating conditions. At the same time, the remaining carboxyl groups after the crosslinking reaction of GO in step (2) can further react with the hydroxyl groups in the thickener, so that the formed product has good affinity with the copper foil and the current collector. In some embodiments, the drying temperature is 50-120°C and the drying time is 1-5 hours.

[0042] In some embodiments, the thermal reduction in step (4) specifically involves: calcining the GO-Si / C composite material obtained in step (3) at a heating rate of 3–5 °C / min to 100–400 °C for 2–4 h in a reducing atmosphere, and then cooling it to room temperature to obtain the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated nano-silicon sphere lithium-ion battery anode material. The reducing atmosphere can be a mixture of hydrogen and argon, or a mixture of hydrogen and nitrogen, wherein the volume percentage of hydrogen is 5–10%.

[0043] The present invention also provides a lithium-ion battery, including a battery casing, an electrode assembly, and an electrolyte (or electrolyte solution). The electrode assembly and the electrolyte solution are sealed inside the battery casing. The electrode assembly includes a positive electrode, a separator, and a negative electrode. The negative electrode active material used in the negative electrode contains the adaptive three-dimensional layered reduced graphene oxide embedded carbon-coated nano-silicon sphere lithium-ion battery negative electrode material described in this invention.

[0044] Graphene oxide (GO), a commonly used anode material in lithium-ion batteries, exhibits strong cycle stability but suffers from low specific capacity. Silicon-based materials, due to their abundant reserves and high theoretical lithium storage capacity, are considered superior candidates. However, silicon-based materials experience significant volume expansion during lithium-ion insertion / extraction, leading to material shedding and reduced battery cycle stability. This invention uses GO crosslinked into a three-dimensional layered structure to form an adaptive flexible film, effectively mitigating the volume expansion of silicon-based materials during lithium-ion battery charge / discharge and improving cycle stability. Furthermore, the inclusion of Si / C materials within the GO layers addresses the issue of low specific capacity in GO.

[0045] The carbon-coated silicon nanospheres used in this invention to prepare adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres for lithium-ion batteries are Si / C composite materials commonly used as active materials for lithium-ion battery anodes in existing technologies. The size of the carbon-coated silicon nanospheres is 20-50 nm. These carbon-coated silicon nanospheres can be obtained commercially or prepared by polymer coating-calcination method (for specific preparation methods, please refer to Colloids and Surfaces A, 2006, 272(1-2):22-26). The carbon-coated silicon nanospheres used in the following examples of this invention were purchased from Shenzhen Zhongyue Chemical Co., Ltd., model BSC450, with a specification of 20-50 nm.

[0046] This invention utilizes a crosslinking agent to coat graphene onto a silicon anode, forming an adaptive elastic buffer space. Compared to traditional binders (CMC), this effectively mitigates capacity loss caused by volume expansion, significantly improving the cycle stability of the silicon material. The crosslinking agent and graphene oxide (GO) can further react with organic polymers through the remaining hydroxyl functional groups, enhancing the solubility of GO in both nonpolar and polar aprotic solvents. This invention provides an adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanosphere (rGO-Si / C) lithium-ion battery anode material with adjustable buffer space spacing, offering experimental guidance for the development of subsequent battery anode materials.

[0047] The above technical solution will be described in detail below with reference to specific embodiments.

[0048] Example 1

[0049] This embodiment provides an adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material, the preparation method of which includes the following steps:

[0050] (1) 10 mg of graphene oxide (GO) was placed in 10 mL of N,N-dimethylformamide (DMF) solvent, and 0.1 g of Si / C (purchased from Shenzhen Zhongyue Chemical Co., Ltd., model BSC450, specification 20-50 nm carbon-coated silicon nanospheres) and 1 mg of polyethylene glycol (molecular weight 50000) were added. After stirring continuously for 3 h, the precursor was obtained.

[0051] (2) Add 50 mg of hexamethylene diisocyanate (HDI) and 39 mg of triethylamine to the obtained precursor, stir to obtain GO-Si / C mixture, coat it on copper foil and dry it at 70°C for 2 hours to obtain GO-Si / C material.

[0052] (3) The prepared GO-Si / C material was heated to 300℃ and calcined for 2h in a tube furnace under the protection of a mixture of argon and hydrogen at a heating rate of 2℃ / min. The flow rate of the mixture was 5sscm and the volume percentage of hydrogen in the mixture was 3%. The heat treatment yielded rGO-Si / C material.

[0053] The schematic diagram of the process and structure of the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in this embodiment is shown below. Figure 2 As shown. The adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in this embodiment was observed using scanning electron microscopy. Figure 3 and Figure 4The SEM images show that the material exhibits a layered structure, and analysis reveals that the silicon content in this anode material is 31.2%. The layered structure with adaptive elastic buffer space in this embodiment facilitates lithium-ion insertion / extraction, mitigating volume expansion during Si / C charging and discharging. Surface defects expose more active sites, shortening the ion-electron transport path, resulting in excellent electrochemical performance as a lithium-ion anode. X-ray diffraction (XRD) patterns are shown below. Figure 5 As shown, in addition to the obvious carbon peak, the characteristic Si peak of this lithium-ion battery anode material is also quite obvious, indicating that graphene oxide (GO) and crosslinking agent react to successfully coat silicon nanospheres and form a three-dimensional layered structure.

[0054] Electrochemical tests were performed on the lithium-ion battery anode material of this embodiment, from... Figure 6 It can be seen that rGO-Si / C exhibits good cycle stability, and the electrode demonstrates high reversibility; furthermore, this composite material exhibits good cycle stability at 0.5 A g. -1 After 200 cycles, the specific capacity can still be maintained at 550 mAh / g. Meanwhile, in the literature (Carbon 2011(49)1787-1796), a negative electrode material was prepared by coating graphene onto carbon-coated silicon nanospheres with a binder using a solution method. This material was then assembled into a lithium-ion battery, and its specific capacity at 0.2 Ag was measured. -1 After 30 cycles, the specific capacity was only 510 mAh / g, and it showed a significant decreasing trend, indicating poor cycling stability. Reference (Advanced Functional Materials, 2021, 31(33):2101487.) Zhu et al. reported a method of covering the surface of Si@C particles with graphene via chemical reduction. After further dispersion and heat treatment, a silicon / carbon nanosphere composite material was prepared. This material showed good performance at 0.2 A g. -1 At the given current density, the initial reversible specific capacity was 888.6 mAh g⁻¹, but after up to 50 cycles, the electrode specific capacity decreased to 610.7 mAh g⁻¹. -1 Moreover, the trend is clearly downward. The adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in this embodiment has significant advantages over the anode material in this literature.

[0055] Example 2

[0056] This embodiment provides an adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material, the preparation method of which includes the following steps:

[0057] (1) 10 mg of graphene oxide (GO) was placed in 10 mL of N,N-dimethylformamide (DMF) solvent, and 0.1 g of Si / C and 1 mg of polyethylene glycol (molecular weight 20000) were added. After stirring continuously for 3 h, the precursor was obtained.

[0058] (2) Add 50 mg of toluene diisocyanate (MDI) and 39 mg of triethylamine to the obtained precursor, stir to obtain GO-Si / C mixture, coat it on copper foil and dry it at 70°C for 2 hours to obtain GO-Si / C material.

[0059] (3) Step (3) in this embodiment is the same as step (3) in embodiment 1.

[0060] Testing revealed that the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in this embodiment exhibits excellent electrochemical performance. After 200 cycles at a current density of 0.5 mA / g, the discharge capacity of the material remains at 513 mAh / g. Furthermore, analysis showed that the silicon content in this anode material is 32.4%.

[0061] Example 3

[0062] This embodiment provides an adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material, the preparation method of which includes the following steps:

[0063] (1) 10 mg of graphene oxide (GO) was placed in 10 mL of toluene solvent, 0.1 g of Si / C and 1 mg of polyethylene glycol (molecular weight 5000) were added, and the mixture was stirred for 3 h to obtain the precursor.

[0064] (2) Step (2) in this embodiment is the same as step (2) in embodiment 1.

[0065] (3) The prepared GO-Si / C material was heated to 400℃ and calcined for 2h in a tube furnace under the protection of a mixture of argon and hydrogen at a heating rate of 2℃ / min. The flow rate of the mixture was 5sscm and the volume percentage of hydrogen in the mixture was 3%. The heat treatment yielded rGO-Si / C material.

[0066] Testing revealed that the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in this embodiment exhibits excellent electrochemical performance. After 200 cycles at a current density of 0.5 mA / g, the discharge capacity of the material remains at 481 mAh / g, and analysis showed that the silicon content in the anode material is 30.7%.

[0067] Example 4

[0068] This embodiment provides an adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material, the preparation method of which includes the following steps:

[0069] (1) Step (1) of this embodiment is the same as step (1) of embodiment 1.

[0070] (2) Add 50 mg of toluene diisocyanate (MDI) and 39 mg of triethylamine to the obtained precursor, stir to obtain GO-Si / C mixture, coat it on copper foil and dry it at 70°C for 2 hours to obtain GO-Si / C material.

[0071] (3) The prepared GO-Si / C material was heated to 400℃ and calcined for 2h in a tube furnace under the protection of a mixture of argon and hydrogen at a heating rate of 2℃ / min. The flow rate of the mixture was 5sscm and the volume percentage of hydrogen in the mixture was 2%. The heat treatment yielded rGO-Si / C material.

[0072] Testing revealed that the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared in this embodiment exhibits excellent electrochemical performance. After 200 cycles at a current density of 0.5 mA / g, the discharge capacity of the material remains at 524 mAh / g, and analysis showed that the silicon content in the anode material is 31.8%.

[0073] As can be seen from the above embodiments, the adaptive three-dimensional layered reduced graphene oxide-embedded carbon-coated silicon nanospheres (rGO-Si / C) lithium-ion battery anode material prepared by the present invention exhibits excellent electrochemical performance, high specific capacity, and good cycle stability.

[0074] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-adapting three-dimensional layered reduced graphene oxide-embedded carbon-coated nanosilicon sphere lithium-ion battery anode material, characterized in that, It comprises a self-adapting three-dimensional layered structure formed by cross-linking reaction of graphene oxide and cross-linking agent on the surface of carbon-coated silicon nanospheres and reduction; the structure has elastic buffer space, which can effectively relieve the volume expansion of the negative electrode material caused by charging and discharging, and improve the stability of the negative electrode material; The cross-linking agent is an isocyanate compound, and the cross-linking reaction is cross-linking reaction of carboxyl functional groups contained in graphene oxide and hydroxyl functional groups of the cross-linking agent; the negative electrode material further comprises a thickening agent, and the thickening agent is a high molecular polymer containing at least two hydroxyl groups.

2. The lithium-ion battery anode material of claim 1, wherein, The mass percentage of silicon element in the negative electrode material is 20-50%.

3. The method of producing a lithium-ion battery anode material according to claim 1 or 2, wherein The method comprises the following steps: (1) dispersing graphene oxide in an organic solvent, mixing with carbon-coated nanosilicon and a thickening agent, and continuously stirring to obtain a precursor; (2) mixing the precursor of step (1) with a cross-linking agent and a catalyst, stirring to make the graphene oxide and the cross-linking agent undergo cross-linking reaction, and obtaining a cross-linking reaction product; (3) coating the cross-linking reaction product of step (2) on a copper foil and drying to obtain a GO-Si / C composite material; (4) heat-reducing the GO-Si / C composite material of step (3) to obtain the self-adapting three-dimensional layered reduced graphene oxide embedded carbon-coated nanosilicon sphere lithium ion battery negative electrode material.

4. The production method according to claim 3, wherein The organic solvent of step (1) is one or more of N, N-dimethylformamide, toluene, ethyl acetate and xylene.

5. The production method according to claim 3, wherein The mass percentage of carbon-coated nanosilicon in the cross-linking reaction product of step (2) is 20-50%, the mass percentage of the thickening agent is 0.1-0.5%, and the mass ratio of graphene oxide to the thickening agent is (2-5):(0.1-0.5).

6. The production method according to claim 3, wherein The mass ratio of graphene oxide to the cross-linking agent is 1:2-5.

7. The production method according to claim 3, wherein The drying temperature of step (3) is 50-120℃, and the drying time is 1-5 hours.

8. The production method according to claim 3, wherein The heat reduction of step (4) is as follows: heating the GO-Si / C composite material of step (3) to 100-400℃ at a heating rate of 3-5 ℃ / min in a reducing atmosphere, keeping calcining for 2-4 h, and then cooling to room temperature to obtain the self-adapting three-dimensional layered reduced graphene oxide embedded carbon-coated nanosilicon sphere lithium ion battery negative electrode material.

9. A lithium-ion battery comprising a negative electrode sheet, characterized by, The negative electrode active material used in the negative electrode sheet contains the self-adapting three-dimensional layered reduced graphene oxide embedded carbon-coated nanosilicon sphere lithium ion battery negative electrode material of claim 1 or 2.

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