Silicon negative electrode material, method of making the same, and lithium-ion battery comprising the same

Abstract

The application provides a silicon negative electrode material, a preparation method thereof and a lithium ion battery comprising the same. The silicon negative electrode material is a core-shell structure, wherein the core layer is a nanometer silicon ball, and the shell layer is a TiO2 / C composite layer with a double-continuous phase structure. The silicon negative electrode material provided by the application solves the problems of poor conductivity and poor cycle performance of the silicon-based negative electrode material, has low requirements on the produced equipment, is environment-friendly and suitable for industrialization.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and more specifically, to a silicon anode material, its preparation method, and a lithium-ion battery comprising the same. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in electronic devices, electric vehicles, and energy storage power stations due to their advantages such as high operating voltage, low self-discharge effect, long cycle life without memory effect, and environmental friendliness. However, the anode materials of commercially available lithium-ion batteries mainly use graphite-based electrode materials, but their theoretical specific capacity is only 372 mAh / g, which cannot meet the ever-increasing energy demands.

[0003] Silicon-based anode materials boast a theoretical specific capacity as high as 4200 mAh / g, more than 10 times that of graphite-based anodes, and are abundant and widely available, making them considered the best candidate for current anode materials. However, silicon-based anode materials suffer from severe volume effects during lithium insertion / extraction processes, with volume expansion reaching over 300%. This causes structural collapse and loss of contact with the conductive substrate. Furthermore, the continuous formation and decomposition of the SEI film consumes a large number of lithium ions, ultimately leading to rapid capacity decay. Coating the surface of silicon materials with a layer of material can, to some extent, support their structure and improve the electrochemical performance of silicon-based anode materials.

[0004] In the prior art, Chinese patent CN108878815A, published on November 23, 2018, discloses a composite lithium-ion battery anode material and its preparation method. This composite anode material is prepared using a nano-non-metallic matrix, metal dopants, inorganic silicon salts, polyvinylidene fluoride, modifiers, carbonization regulators, conductive agents, binders, and dopamine. While this material can improve electrochemical performance and conductivity to some extent, some problems remain. Specifically, the method's effect on suppressing side reactions is not significant enough, and the material continuously consumes electrolyte during charge-discharge cycles, leading to poor cycle performance. Summary of the Invention

[0005] The main objective of this invention is to provide a silicon anode material, its preparation method, and a lithium-ion battery including the same, so as to solve the problem of poor cycle performance of silicon anode materials in the prior art.

[0006] To achieve the above objectives, according to one aspect of the present invention, a silicon anode material is provided, which has a core-shell structure, wherein the core layer is a nano-silicon sphere and the shell layer is a TiO2 / C composite layer with a dual continuous phase structure.

[0007] Furthermore, the weight ratio of TiO2 to C in the TiO2 / C composite layer is (4-5):(3-4).

[0008] Furthermore, the thickness of the shell is 50–200 nm.

[0009] Furthermore, the particle size of the silicon nanospheres is 100–500 nm.

[0010] According to another aspect of the present invention, a method for preparing the above-mentioned silicon anode material is also provided, comprising the following steps: S1, mixing an organic titanium source, an organic carbon source and an organic solvent to form a first mixture; S2, adding and dispersing nano-silicon spheres in the first mixture, and then adding a hydrolysis stabilizer to form a second mixture; S3, subjecting the second mixture to a hydrothermal reaction and cooling to obtain a precursor; S4, calcining the precursor under an inert atmosphere to obtain the silicon anode material.

[0011] Furthermore, the organic titanium source is one or more of tetraisopropoxide, tetrabutyl titanate, and tetraethyl titanate; preferably, the organic carbon source is one or more of polyvinylpyrrolidone, aniline, polypropylene, and polyvinyl alcohol.

[0012] Further, in step S1, the weight ratio between the organic titanium source and the organic carbon source is (3-5):1, and the organic solvent is a mixture of anhydrous ethanol and deionized water, preferably with a volume ratio of anhydrous ethanol and deionized water of (1-2):1; preferably, the mass concentration of the organic titanium source and the organic carbon source in the first mixture is 20-35%.

[0013] Further, in step S2, the weight ratio of the nano-silicon spheres to the organic carbon source is (1.5-2.5):1; preferably, the volume ratio of the hydrolysis stabilizer to the organic titanium source is (2.5-3.5):1.

[0014] Further, in step S3, the second mixture is heated to 150-180°C at a rate of 5-10°C / min and held at that temperature for 10-15 hours to carry out a hydrothermal reaction; after the reaction is complete, it is cooled to room temperature, then filtered, washed, and dried to obtain the precursor; preferably, in step S4, the precursor is heated to 700-800°C at a rate of 5-10°C / min and held at that temperature for 3-5 hours to carry out a calcination process.

[0015] According to another aspect of the present invention, a lithium-ion battery is also provided, comprising a negative electrode material, wherein the negative electrode material is the aforementioned silicon negative electrode material.

[0016] This invention provides a silicon anode material formed by coating nano-silicon spheres with a dual continuous phase TiO2 / C, which solves the problems of poor conductivity and poor cycle performance of silicon-based anode materials. At the same time, it has low requirements for the equipment used in its production, is environmentally friendly, and is suitable for industrialization. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 A schematic diagram of the structure of the silicon anode material according to the present invention is shown; and

[0019] Figure 2 The cycle performance curves of the batteries corresponding to the silicon anode materials prepared in Examples 1 to 6 of this invention are shown, where the solid arrows indicate the initial specific capacity from high to low, and the dashed arrows indicate the capacity retention rate at the end of the cycle from high to low. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] As described in the background section, although existing technologies have improved the conductivity and other properties of silicon anode materials, there are still shortcomings in terms of cycle performance.

[0022] To address the above problems, this invention provides a silicon anode material, such as... Figure 1 As shown, the silicon anode material has a core-shell structure, where the core layer A is a silicon nanosphere and the shell layer B is a TiO2 / C composite layer with a dual continuous phase structure. This core-shell structure of TiO2 / C shell encapsulating silicon nanospheres not only alleviates the volume effect of Si during lithium insertion / extraction but also improves the material's conductivity. Furthermore, the dual continuous phase TiO2 / C shell protects the material from electrolyte corrosion and prevents chemical reactions with HF in the LiPF6 electrolyte, facilitating the formation of a structurally stable SEI film and thus improving the material's cycle stability. Simultaneously, the material also exhibits good thermal stability, with the internal chemical reaction heat effectively reduced.

[0023] In summary, this invention effectively solves the problem that existing silicon anode materials cannot simultaneously achieve high conductivity and good cycle performance. The silicon anode material provided exhibits good cycle stability and high rate performance, with a capacity retention of 97.5% after 100 cycles at a current density of 2 A / g. Furthermore, it has low requirements for the production equipment, is environmentally friendly, and suitable for industrialization.

[0024] To further improve the performance of the silicon anode material, in a preferred embodiment, the weight ratio of TiO2 to C in the TiO2 / C composite layer is (4-5):(3-4). More preferably, the shell thickness is 50-200 nm. Further, the particle size of the silicon nanospheres is 100-500 nm.

[0025] According to another aspect of the present invention, a method for preparing the above-mentioned silicon anode material is also provided, wherein the preparation method includes the following steps: S1, mixing an organic titanium source, an organic carbon source and an organic solvent to form a first mixture; S2, adding and dispersing nano-silicon spheres in the first mixture, and then adding a hydrolysis stabilizer to form a second mixture; S3, subjecting the second mixture to a hydrothermal reaction and cooling to obtain a precursor; S4, calcining the precursor under an inert atmosphere to obtain the silicon anode material.

[0026] In the above method, an organic titanium source and an organic carbon source are prepared as a first mixture beforehand. Then, nano-silicon spheres and a hydrolysis stabilizer are added to form a stable second mixture before a hydrothermal reaction is carried out. During this process, the organic titanium source gradually hydrolyzes and, together with the organic carbon source, coats the surface of the nano-silicon spheres to form a precursor. The precursor is further calcined to uniformly coat the surface of the nano-silicon spheres with a TiO2 / C shell having a bicontinuous structure.

[0027] This hydrothermal method can coat the surface of silicon nanospheres with a uniform TiO2 / C shell with a bicontinuous structure, which greatly promotes the thermal stability of silicon anode materials and reduces the internal reaction heat, thus effectively improving conductivity and cycle performance. At the same time, this invention features a simple process, low production cost, ease of operation, and high efficiency.

[0028] In a preferred embodiment, the organic titanium source is one or more of titanium tetraisopropoxide, tetrabutyl titanate, and tetraethyl titanate; preferably, the organic carbon source is one or more of polyvinylpyrrolidone, aniline, polypropylene resin, and polyvinyl alcohol. Using these organic titanium and organic carbon sources results in a more stable reaction process, a more uniform coating layer in the precursor, and a more complete bicontinuous phase structure in the final TiO2 / C shell, leading to better overall material performance. Furthermore, these organic titanium and organic carbon sources are relatively inexpensive, which also helps reduce material production costs.

[0029] To further improve reaction stability and promote the formation of a shell-type bicontinuous phase structure, in a preferred embodiment, in step S1, the weight ratio of the organic titanium source to the organic carbon source is (3-5):1, and the organic solvent is a mixture of anhydrous ethanol and deionized water, preferably with a volume ratio of (1-2):1; preferably, the mass concentration of the organic titanium source and the organic carbon source in the first mixture is 20-35%. In the actual mixing process, it is preferable to thoroughly stir the organic titanium source, organic carbon source, and organic solvent in a magnetic stirrer to form a homogeneous solution. Furthermore, the system is kept under continuous stirring during the addition of the nano-silicon spheres. After adding the nano-silicon spheres, the system is first ultrasonically dispersed for a period of time before the hydrolysis stabilizer is added.

[0030] In a preferred embodiment, in step S2, the weight ratio of the silicon nanospheres to the organic carbon source is (1.5–2.5):1; preferably, the volume ratio of the hydrolytic stabilizer to the organic titanium source is (2.5–3.5):1. At this ratio, the resulting shell thickness is more suitable, and the reaction process is more stable.

[0031] To further improve reaction efficiency and structural integrity, in a preferred embodiment, in step S3, the second mixture is heated to 150-180°C at a rate of 5-10°C / min and held at that temperature for 12 hours to carry out a hydrothermal reaction. After the reaction is complete, it is cooled to room temperature, then filtered, washed, and dried to obtain the precursor. In actual operation, it is preferable to transfer the second mixture to a stainless steel reactor and place it in a constant temperature chamber.

[0032] Preferably, in step S4, the precursor is heated to 700-800°C at a rate of 5-10°C / min and held at that temperature for 3-5 hours for calcination. The inert atmosphere used during calcination can be nitrogen, argon, or other inert atmospheres. The calcination process can be carried out in a tube furnace.

[0033] According to another aspect of the present invention, a lithium-ion battery is also provided, comprising a negative electrode material, which is the silicon negative electrode material described above.

[0034] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0035] Example 1

[0036] S1. Dissolve 2 ml of tetraisopropoxide titanium (TTIP) and 0.5 g of polyvinylpyrrolidone (PVP) together in a mixed solvent of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water is 1:1, and stir thoroughly for 15 min using a magnetic stirrer.

[0037] S2. While stirring continuously, add 1g of nano-silicon material with a particle size of 100-500nm to solution A obtained in step S1, disperse it by ultrasonication for 30min, then add 6ml of acetic acid, stir at room temperature for 3h, and react fully to obtain solution B.

[0038] S3. Transfer the solution B obtained in step S2 to a stainless steel reactor and place it in a constant temperature oven. Heat the solution to 165°C at a heating rate of 5°C / min and keep it at that temperature for 12 hours. Then cool the solution to room temperature with the furnace. After washing and drying, the precursor C is obtained.

[0039] S4. Weigh the precursor C prepared in step S3 and place it in a tube furnace. Under a protective atmosphere, heat it to 750°C at a heating rate of 5°C and hold it at that temperature for 3 hours. Then, cool it to room temperature with the furnace to obtain a silicon-based anode material with a dual continuous phase structure, denoted as Si@TiO2 / C anode material. The shell thickness of this material is 100-200 nm, and the weight ratio of TiO2 / C in the shell is 5:3.

[0040] Test Method: The prepared silicon-based anode material was mixed with conductive agent SP and binder CMC+SBR (1:1) in a mass ratio of 70:15:15 to form a slurry. After thorough grinding and mixing, the slurry was uniformly coated onto copper foil and dried at 60℃ for 6 hours. The slurry was then punched into 12mm diameter electrode sheets and transferred to a glove box under a protective atmosphere. A 2032 coin cell was assembled using a lithium metal sheet as the counter electrode, a 1mol / L LiPF6 (EC:DMC = 1:1) electrolyte, and a Celgard 2400 separator. After standing for 24 hours, the cells were transferred to a Newway testing system for constant current charge-discharge testing at a specific current density. The charge-discharge cutoff voltage range was 0.01V to 1.5V. The obtained cycle performance curves are shown in [Figure number missing]. Figure 2 .

[0041] Example 2

[0042] S1. Dissolve 2 ml of tetrabutyl titanate (TBT) and 0.5 g of polyvinylpyrrolidone (PVP) together in a mixed solvent of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water is 1:1, and stir thoroughly for 15 min using a magnetic stirrer.

[0043] S2. While stirring continuously, add 1g of nano-silicon material with a particle size of 100-500nm to solution A obtained in step S1, disperse it by ultrasonication for 30min, then add 6ml of diethanolamine, stir at room temperature for 3h, and react fully to obtain solution B.

[0044] S3. Transfer the solution B obtained in step S2 to a stainless steel reactor and place it in a constant temperature oven. Heat the solution to 165°C at a heating rate of 5°C / min and keep it at that temperature for 12 hours. Then cool the solution to room temperature with the furnace. After washing and drying, the precursor C is obtained.

[0045] S4. Weigh the precursor C prepared in step S3 and place it in a tube furnace. Under a protective atmosphere, heat it to 750°C at a heating rate of 5°C and hold it at that temperature for 3 hours. Then, cool it to room temperature with the furnace to obtain a silicon-based anode material with a dual continuous phase structure, denoted as Si@TiO2 / C anode material. The shell thickness of this material is 100-200 nm, and the weight ratio of TiO2 / C in the shell is 4.5:3.

[0046] Test Method: The prepared silicon-based anode material was mixed with conductive agent SP and binder CMC+SBR (1:1) in a mass ratio of 70:15:15 to form a slurry. After thorough grinding and mixing, the slurry was uniformly coated onto copper foil and dried at 60℃ for 6 hours. The slurry was then punched into 12mm diameter electrode sheets and transferred to a glove box under a protective atmosphere. A 2032 coin cell was assembled using a lithium metal sheet as the counter electrode, a 1mol / L LiPF6 (EC:DMC = 1:1) electrolyte, and a Celgard 2400 separator. After standing for 24 hours, the cells were transferred to a Newway testing system for constant current charge-discharge testing at a specific current density. The charge-discharge cutoff voltage range was 0.01V to 1.5V. The obtained cycle performance curves are shown in [Figure number missing]. Figure 2 .

[0047] Example 3

[0048] S1. Dissolve 2 ml of tetraisopropoxide titanium (TTIP) and 0.5 g of aniline (ANI) together in a mixed solvent of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water is 1:1, and stir thoroughly for 15 min using a magnetic stirrer.

[0049] S2. While stirring continuously, add 1g of nano-silicon material with a particle size of 100-500nm to solution A obtained in step S1, disperse it by ultrasonication for 30min, then add 6ml of acetic acid, stir at room temperature for 3h, and react fully to obtain solution B.

[0050] S3. Transfer the solution B obtained in step S2 to a stainless steel reactor and place it in a constant temperature oven. Heat the solution to 165°C at a heating rate of 5°C / min and keep it at that temperature for 12 hours. Then cool the solution to room temperature with the furnace. After washing and drying, the precursor C is obtained.

[0051] S4. Weigh the precursor C prepared in step S3 and place it in a tube furnace. Under a protective atmosphere, heat it to 750°C at a heating rate of 5°C and hold it at that temperature for 3 hours. Then, cool it to room temperature with the furnace to obtain a silicon-based anode material with a dual continuous phase structure, denoted as Si@TiO2 / C anode material. The shell thickness of this material is 100-200 nm, and the weight ratio of TiO2 / C in the shell is 5:3.5.

[0052] Test Method: The prepared silicon-based anode material was mixed with conductive agent SP and binder CMC+SBR (1:1) in a mass ratio of 70:15:15 to form a slurry. After thorough grinding and mixing, the slurry was uniformly coated onto copper foil and dried at 60℃ for 6 hours. The slurry was then punched into 12mm diameter electrode sheets and transferred to a glove box under a protective atmosphere. A 2032 coin cell was assembled using a lithium metal sheet as the counter electrode, a 1mol / L LiPF6 (EC:DMC = 1:1) electrolyte, and a Celgard 2400 separator. After standing for 24 hours, the cells were transferred to a Newway testing system for constant current charge-discharge testing at a specific current density. The charge-discharge cutoff voltage range was 0.01V to 1.5V. The obtained cycle performance curves are shown in [Figure number missing]. Figure 2 .

[0053] Example 4

[0054] S1. Dissolve 2 ml of tetrabutyl titanate (TBT) and 0.5 g of aniline (ANI) in a mixed solvent of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water is 1:1, and stir thoroughly for 15 min using a magnetic stirrer.

[0055] S2. While stirring continuously, add 1g of nano-silicon material with a particle size of 100-500nm to solution A obtained in step S1, disperse it by ultrasonication for 30min, then add 6ml of acetic acid, stir at room temperature for 3h, and react fully to obtain solution B.

[0056] S3. Transfer the solution B obtained in step S2 to a stainless steel reactor and place it in a constant temperature oven. Heat the solution to 165°C at a heating rate of 5°C / min and keep it at that temperature for 12 hours. Then cool the solution to room temperature with the furnace. After washing and drying, the precursor C is obtained.

[0057] S4. Weigh the precursor C prepared in step S3 and place it in a tube furnace. Under a protective atmosphere, heat it to 750°C at a heating rate of 5°C and hold it at that temperature for 3 hours. Then, cool it to room temperature with the furnace to obtain a silicon-based anode material with a dual continuous phase structure, denoted as Si@TiO2 / C anode material. The shell thickness of this material is 100-200 nm, and the weight ratio of TiO2 / C in the shell is 4.5:3.5.

[0058] Test Method: The prepared silicon-based anode material was mixed with conductive agent SP and binder CMC+SBR (1:1) in a mass ratio of 70:15:15 to form a slurry. After thorough grinding and mixing, the slurry was uniformly coated onto copper foil and dried at 60℃ for 6 hours. The slurry was then punched into 12mm diameter electrode sheets and transferred to a glove box under a protective atmosphere. A 2032 coin cell was assembled using a lithium metal sheet as the counter electrode, a 1mol / L LiPF6 (EC:DMC = 1:1) electrolyte, and a Celgard 2400 separator. After standing for 24 hours, the cells were transferred to a Newway testing system for constant current charge-discharge testing at a specific current density. The charge-discharge cutoff voltage range was 0.01V to 1.5V. The obtained cycle performance curves are shown in [Figure number missing]. Figure 2 .

[0059] Example 5

[0060] S1. Dissolve 2 ml of tetraethyl titanate and 0.5 g of polyvinylpyrrolidone (PVP) together in a mixed solvent of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water is 1:1, and stir thoroughly for 15 min using a magnetic stirrer.

[0061] S2. While stirring continuously, add 1g of nano-silicon material with a particle size of 100-500nm to solution A obtained in step S1, disperse it by ultrasonication for 30min, then add 6ml of acetic acid, stir at room temperature for 3h, and react fully to obtain solution B.

[0062] S3. Transfer the solution B obtained in step S2 to a stainless steel reactor and place it in a constant temperature oven. Heat the solution to 165°C at a heating rate of 5°C / min and keep it at that temperature for 12 hours. Then cool the solution to room temperature with the furnace. After washing and drying, the precursor C is obtained.

[0063] S4. Weigh the precursor C prepared in step S3 and place it in a tube furnace. Under a protective atmosphere, heat it to 750°C at a heating rate of 5°C and hold it at that temperature for 3 hours. Then, cool it to room temperature with the furnace to obtain a silicon-based anode material with a dual continuous phase structure, denoted as Si@TiO2 / C anode material. The shell thickness of this material is 100-200 nm, and the weight ratio of TiO2 / C in the shell is 7:3.

[0064] Test Method: The prepared silicon-based anode material was mixed with conductive agent SP and binder CMC+SBR (1:1) in a mass ratio of 70:15:15 to form a slurry. After thorough grinding and mixing, the slurry was uniformly coated onto copper foil and dried at 60℃ for 6 hours. The slurry was then punched into 12mm diameter electrode sheets and transferred to a glove box under a protective atmosphere. A 2032 coin cell was assembled using a lithium metal sheet as the counter electrode, a 1mol / L LiPF6 (EC:DMC = 1:1) electrolyte, and a Celgard 2400 separator. After standing for 24 hours, the cells were transferred to a Newway testing system for constant current charge-discharge testing at a specific current density. The charge-discharge cutoff voltage range was 0.01V to 1.5V. The obtained cycle performance curves are shown in [Figure number missing]. Figure 2 .

[0065] Example 6

[0066] S1. Dissolve 2 ml of tetraisopropoxide titanium (TTIP) and 0.5 g of aniline (ANI) together in a mixed solvent of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water is 1:1, and stir thoroughly for 15 min using a magnetic stirrer.

[0067] S2. While stirring continuously, add 1g of nano-silicon material with a particle size of 100-500nm to solution A obtained in step S1, disperse it by ultrasonication for 30min, then add 6ml of acetic acid, stir at room temperature for 3h, and react fully to obtain solution B.

[0068] S3. Transfer the solution B obtained in step S2 to a stainless steel reactor and place it in a constant temperature oven. Heat the solution to 165°C at a heating rate of 5°C / min and keep it at that temperature for 12 hours. Then cool the solution to room temperature with the furnace. After washing and drying, the precursor C is obtained.

[0069] S4. Weigh the precursor C prepared in step S3 and place it in a tube furnace. Under a protective atmosphere, heat it to 750°C at a heating rate of 5°C and hold it at that temperature for 3 hours. Then, cool it to room temperature with the furnace to obtain a silicon-based anode material with a dual continuous phase structure, denoted as Si@TiO2 / C anode material. The shell thickness of this material is 100-200 nm, and the weight ratio of TiO2 / C in the shell is 7:4.

[0070] Test Method: The prepared silicon-based anode material was mixed with conductive agent SP and binder CMC+SBR (1:1) in a mass ratio of 70:15:15 to form a slurry. After thorough grinding and mixing, the slurry was uniformly coated onto copper foil and dried at 60℃ for 6 hours. The slurry was then punched into 12mm diameter electrode sheets and transferred to a glove box under a protective atmosphere. A 2032 coin cell was assembled using a lithium metal sheet as the counter electrode, a 1mol / L LiPF6 (EC:DMC = 1:1) electrolyte, and a Celgard 2400 separator. After standing for 24 hours, the cells were transferred to a Newway testing system for constant current charge-discharge testing at a specific current density. The charge-discharge cutoff voltage range was 0.01V to 1.5V. The obtained cycle performance curves are shown in [Figure number missing]. Figure 2 .

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., 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 method for preparing a silicon anode material, characterized in that, The preparation method includes the following steps: S1, an organic titanium source, an organic carbon source, and an organic solvent are mixed to form a first mixture; the weight ratio of the organic titanium source to the organic carbon source is (3~5):1, the organic solvent is a mixture of anhydrous ethanol and deionized water, and the volume ratio of the anhydrous ethanol to the deionized water is (1~2):1; the mass concentration of the organic titanium source and the organic carbon source in the first mixture is 20~35%; S2, add and disperse the nano-silicon spheres in the first mixture, then add a hydrolysis stabilizer to form a second mixture; the weight ratio of the nano-silicon spheres to the organic carbon source is (1.5~2.5):1; the volume ratio of the hydrolysis stabilizer to the organic titanium source is (2.5~3.5):1; S3, the second mixture is heated to 150-180°C at a rate of 5-10°C / min and kept at this temperature for 10-15 hours to carry out a hydrothermal reaction; after the reaction is complete, it is cooled to room temperature, then filtered, washed, and dried to obtain the precursor; S4, the precursor is heated to 700-800°C at a rate of 5-10°C / min under an inert atmosphere and held at that temperature for 3-5 hours to carry out a calcination process to obtain the silicon anode material. The silicon anode material has a core-shell structure, wherein the core layer is a nano-silicon sphere and the shell layer is a TiO2 / C composite layer with a dual continuous phase structure.

2. The method for preparing the silicon anode material according to claim 1, characterized in that, The weight ratio of TiO2 to C in the TiO2 / C composite layer is (4~5):(3~4).

3. The method for preparing the silicon anode material according to claim 1 or 2, characterized in that, The thickness of the shell is 50~200nm.

4. The method for preparing the silicon anode material according to claim 1 or 2, characterized in that, The particle size of the silicon nanospheres is 100~500nm.

5. The method for preparing the silicon anode material according to claim 1, characterized in that, The organic titanium source is one or more of tetraisopropoxide, tetrabutyl titanate, and tetraethyl titanate; the organic carbon source is one or more of polyvinylpyrrolidone, aniline, polypropylene ester, and polyvinyl alcohol.

6. A lithium-ion battery, comprising a negative electrode material, characterized in that, The negative electrode material is a silicon negative electrode material prepared by the preparation method according to any one of claims 1 to 5.

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