A silicon oxide-based composite negative electrode material and its preparation method and application

Abstract

The present invention belongs to the technical field of negative electrode materials for lithium-ion batteries, and in particular to a silicon oxide-based composite negative electrode material and its preparation method and application. The present invention first forms a large number of micropores or irregular micro-pits on the surface of SiO particles and / or between SiO particles, and then coats Zn / Fe-MOF on its surface. During the high-temperature pyrolysis process, a large amount of Zn evaporates, and Fe atoms are evenly distributed on the porous carbon skeleton formed by MOF carbonization. Then, carbon nanotubes are prepared using Fe as a catalyst, and finally acid etching is performed to remove Fe and a small amount of Zn. This not only enhances the bonding force between SiO particles and the porous carbon framework, but also generates carbon nanotubes in situ on the porous carbon surface, making it a firmly bonded whole. The porous carbon framework can effectively suppress the volume change of SiO during charging and discharging, and increase the stability of the negative electrode SEI film.

Description

Technical Field

[0001] The present invention belongs to the technical field of negative electrode materials for lithium ion batteries, and in particular relates to a silicon oxide-based composite negative electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have become a hot topic of research worldwide due to their many advantages, including high specific capacity, long service life, high safety, and portability. They are widely used in various electronic devices, electric vehicles, and portable energy storage devices. As a new negative electrode material for lithium-ion secondary batteries, silicon oxide has a higher specific capacity (2000mAh / g) than graphite. However, during the charge and discharge process, its service life is seriously affected by poor conductivity, large volume expansion, and easy pulverization and shedding. In particular, during the initial charge and discharge process of silicon oxide materials, lithium ions react with silicon oxide to form Li2O and Li2SiO4, consuming a large amount of active lithium and resulting in a low coulombic efficiency (<70%) in the first cycle of the battery.

[0003] In order to solve the series of problems caused by the poor conductivity and volume expansion of silicon monoxide, those skilled in the art have modified it through various methods, including nano-sizing, surface coating with carbon, and compounding with graphite. These methods can improve the cycle performance and first-cycle coulombic efficiency to a certain extent, but will cause a decrease in specific capacity. Therefore, how to more effectively alleviate volume expansion, ensure the cycle stability of the battery, and obtain silicon monoxide negative electrode materials with high first-cycle coulombic efficiency, good cycle performance and high specific capacity remains a technical hotspot that needs to be solved in the current lithium-ion battery field. Summary of the Invention

[0004] In order to improve the deficiencies of the prior art, the present invention provides a silicon oxide-based composite negative electrode material, a preparation method, and an application thereof. The use of the silicon oxide-based composite negative electrode material can effectively improve the first-cycle coulombic efficiency of lithium-ion batteries, alleviate problems such as silicon oxide volume expansion, and the lithium-ion battery assembled therefrom has better cycle performance and specific capacity.

[0005] Specifically, the present invention provides the following technical solutions:

[0006] A method for preparing a silicon oxide-based composite negative electrode material, the method comprising the following steps:

[0007] (1) SiO, zinc salt, iron salt, organic ligand and organic solvent are mixed to carry out self-assembly reaction to obtain material 1;

[0008] (2) placing the material 1 of step (1) into a chemical vapor deposition furnace, heating it under the protection of an inert gas, introducing an organic carbon source after heating it to the reaction temperature, and reacting to obtain material 2;

[0009] (3) treating the material 2 from step (2) with acid to obtain material 3;

[0010] (4) placing the material 3 of step (3) into a chemical vapor deposition furnace, heating it under the protection of an inert gas, introducing Ti source and N source gas after heating it to the reaction temperature, and reacting to obtain a silicon oxide-based composite negative electrode material.

[0011] According to an embodiment of the present invention, in step (1), the average particle size D of the SiO 50 It is 2 μm to 8 μm, preferably 3 μm to 6 μm, for example, 3 μm, 4 μm, 5 μm or 6 μm.

[0012] According to an embodiment of the present invention, in step (1), micropores or irregular micro-pits exist on the surface of the SiO particles and / or between the SiO particles.

[0013] According to an embodiment of the present invention, in step (1), the SiO is prepared by the following method:

[0014] First heat to 850-1000℃ under inert atmosphere, then use energy of 100-600eV and beam density of 0.4-0.8mA / cm 2 The ion beam is used for bombardment, the distance from the ion beam to the surface of the SiO particles is controlled to be 1 to 10 mm, the bombardment angle is 30 to 150 degrees, the SiO particles are stirred and turned while bombarding, and the bombardment time is 30 to 60 minutes.

[0015] According to an embodiment of the present invention, a large number of micropores or irregular micro-pits are formed on the surface of SiO particles and / or between SiO particles, and then Zn / Fe-MOF is coated on the surface and subjected to a high-temperature composite treatment under inert atmosphere. This not only strengthens the bonding between the SiO particles and the porous carbon formed by Zn / Fe-MOF, but also enables the in-situ generation of carbon nanotubes on the porous carbon surface, forming a firmly bonded whole.

[0016] According to an embodiment of the present invention, in step (1), the zinc salt is selected from at least one of zinc sulfate, zinc acetate, zinc nitrate or zinc chloride; the iron salt is selected from at least one of ferrous sulfate, ferrous acetate, ferrous nitrate or ferrous chloride; the organic ligand is selected from at least one of naphthalene tetracarboxylic anhydride, dimethylimidazole, 2,5-dihydroxyterephthalic acid, trimesic acid or terephthalic acid; and the organic solvent is selected from at least one of methanol, ethanol, formaldehyde, acetaldehyde, DMF or water.

[0017] According to an embodiment of the present invention, in step (1), the mass ratio of the zinc salt to the organic ligand is 1:(2-4), for example, 1:2, 1:3, or 1:4. The mass ratio of the zinc salt to the iron salt is (6-10):1, for example, 6:1, 7:1, 8:1, 9:1, or 10:1. The volume ratio of the sum of the mass of the zinc salt and the organic ligand to the organic solvent is (0.01-0.1) g:1 mL, for example, 0.01 g:1 mL, 0.02 g:1 mL, 0.03 g:1 mL, 0.04 g:1 mL, 0.05 g:1 mL, 0.06 g:1 mL, 0.08 g:1 mL, 0.09 g:1 mL, or 0.1 g:1 mL. The mass ratio of the zinc salt to SiO is 1:(7-10), for example, 1:7, 1:8, 1:9, or 1:10.

[0018] According to an embodiment of the present invention, in step (1), the self-assembly reaction is carried out under stirring at room temperature for 6 to 24 hours.

[0019] According to an embodiment of the present invention, in step (1), after the self-assembly reaction is completed, post-processing steps such as centrifugal washing and vacuum drying are further included. Preferably, the vacuum drying temperature is 60-100°C.

[0020] According to an embodiment of the present invention, in step (1), zinc salt, iron salt, and organic ligand undergo a self-assembly reaction to generate a metal organic framework material Zn / Fe-MOF, which is coated on the SiO surface.

[0021] According to an embodiment of the present invention, in step (1), the material 1 has a core-shell structure with SiO as the core and Zn / Fe-MOF as the shell, and the shell thickness is 30nm to 100nm.

[0022] According to an embodiment of the present invention, in step (2), the reaction temperature is 500°C to 800°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, and the reaction time is 1h to 10h, for example, 1h, 2h, 3h, 5h, 7h, 8h, 10h.

[0023] According to an embodiment of the present invention, in step (2), the organic carbon source may be one or more of acetylene, ethylene, methane, ethane, propane and n-butane.

[0024] According to an embodiment of the present invention, in step (2), the inert gas is nitrogen and / or argon.

[0025] According to an embodiment of the present invention, in step (2), the heating rate is 2 to 10°C / min, such as 2 to 5°C / min, such as 2°C / min, 3°C / min, 4°C / min, or 5°C / min.

[0026] According to an embodiment of the present invention, in step (2), the volume ratio of the organic carbon source to the inert gas is 1:(5-10), for example, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10.

[0027] According to an embodiment of the present invention, in step (2), 3 to 8 mL / min of organic carbon source needs to be introduced per gram of material 1.

[0028] According to an embodiment of the present invention, in step (3), the acid is one or a combination of at least two of hydrochloric acid, acetic acid, carbonic acid or phosphoric acid; the concentration of the acid and the treatment time are not limited and can be adjusted according to actual conditions, and can completely remove the elemental metal zinc and iron generated by the reduction of the metal organic framework material Zn / Fe-MOF after the heat treatment in step (2).

[0029] According to an embodiment of the present invention, in step (3), after the acid treatment is completed, steps such as water washing, centrifugation, filtration and drying are performed.

[0030] According to an embodiment of the present invention, in step (3), the material 3 has a core-shell structure with SiO as the core, porous carbon as the middle layer and carbon nanotubes as the outermost layer, wherein the thickness of the porous carbon layer is 25 to 90 nm, and the thickness of the carbon nanotube layer is 3 to 10 nm.

[0031] According to an embodiment of the present invention, in step (3), the porous carbon and carbon nanotubes are obtained by heat treatment of the metal organic framework material Zn / Fe-MOF and further reaction with an organic carbon source. Specifically, a large amount of Zn is volatilized from the Zn / Fe-MOF coated on the SiO surface during high-temperature pyrolysis, and Fe atoms are evenly distributed on the porous carbon skeleton formed by carbonization of MOF. Then, with Fe as a catalyst, carbon nanotubes are generated on the porous carbon under the joint action of the organic carbon source, and finally, Fe and a small amount of Zn are removed by acid etching.

[0032] According to an embodiment of the present invention, in step (4), the reaction temperature is 700-850°C, for example, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C or 850°C, and the reaction time is 30 min to 60 min, for example, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0033] According to an embodiment of the present invention, in step (4), the Ti source is TiCl4, and the N source gas is nitrogen and / or ammonia.

[0034] According to an embodiment of the present invention, in step (4), the inert gas is nitrogen and / or argon.

[0035] According to an embodiment of the present invention, in step (4), the heating rate is 2 to 10°C / min, such as 2 to 5°C / min, such as 2°C / min, 3°C / min, 4°C / min, or 5°C / min.

[0036] According to an embodiment of the present invention, in step (4), the Ti source is carried by hydrogen into the chemical vapor deposition furnace, and the flow rate of the Ti source carried by hydrogen is 3 to 10 g / mL (such as 3 g / mL, 4 g / mL, 5 g / mL, 6 g / mL, 7 g / mL, 8 g / mL, 9 g / mL or 10 g / mL), that is, the mass of the Ti source carried by 1 mL of hydrogen is 3 g to 10 g.

[0037] According to an embodiment of the present invention, in step (4), the volume ratio of inert gas: N source gas: hydrogen is 1: (1-1.5): (0.4-0.8).

[0038] According to an embodiment of the present invention, in step (4), 10 to 25 mL / min of N source gas needs to be introduced per gram of material 3.

[0039] According to an embodiment of the present invention, in step (4), TiN is obtained after the Ti source and N source gases react, and is coated on the outer surface of the material 3.

[0040] According to an embodiment of the present invention, in step (4), the silicon oxide-based composite negative electrode material has a three-layer coating structure with SiO as a core, porous carbon as an intermediate layer, carbon nanotubes as a secondary outer layer, and TiN as an outermost layer. The thickness of the porous carbon layer is 25 nm to 90 nm (e.g., 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm), the thickness of the carbon nanotube layer is 3 nm to 10 nm (e.g., 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm), and the thickness of the TiN layer is 10 nm to 30 nm (e.g., 10 nm, 15 nm, 20 nm, 25 nm, 30 nm).

[0041] According to the embodiment of the present invention, the coating structure of the present invention is more uniform and more stable. The structure is more stable when buffering the volume expansion of SiO, which can slow down the rate of damage of the silicon negative electrode after multiple charges and significantly improve the cycle performance of the battery.

[0042] The present invention also provides a silicon oxide-based composite negative electrode material prepared by the above method.

[0043] The present invention also provides a silicon oxide-based composite negative electrode material, which includes SiO as a core, a porous carbon layer coated on the surface of the SiO, a carbon nanotube layer coated on the surface of the porous carbon layer, and a TiN layer coated on the surface of the carbon nanotube layer.

[0044] According to an embodiment of the present invention, the thickness of the porous carbon layer is 25 nm to 90 nm, the thickness of the carbon nanotube layer is 3 nm to 10 nm, and the thickness of the TiN layer is 10 nm to 30 nm.

[0045] According to an embodiment of the present invention, a battery assembled with the silicon oxide-based composite negative electrode material has a first-week discharge capacity of ≥1400 mAh / g at 0.1C, a first-week coulombic efficiency of ≥78%, and a 100-week cycle capacity retention rate of ≥90%.

[0046] The present invention also provides a lithium ion battery, which comprises the above-mentioned silicon monoxide-based composite negative electrode material.

[0047] Beneficial effects of the present invention:

[0048] (1) The present invention first forms a large number of micropores or irregular micro-pits on the surface of SiO particles and / or between SiO particles, and then coats the surface with Zn / Fe-MOF. During the high-temperature pyrolysis process, a large amount of Zn evaporates, and Fe atoms are evenly distributed on the porous carbon skeleton formed by MOF carbonization. Carbon nanotubes are then prepared using Fe as a catalyst, and finally, acid etching is performed to remove Fe and a small amount of Zn. This not only enhances the bonding force between the SiO particles and the porous carbon framework, but also enables the in-situ generation of carbon nanotubes on the porous carbon surface, forming a firmly bonded whole. The porous carbon framework can effectively suppress the volume change of SiO during charge and discharge, thereby increasing the stability of the negative electrode SEI film.

[0049] (2) The porous carbon, carbon nanotubes and TiN are coated on the SiO surface in turn through two coating processes, forming a three-layer coating structure with SiO as the core, porous carbon as the middle layer, carbon nanotubes as the second outer layer and TiN as the outermost layer. Each coating layer makes the particles more uniform and the structure more stable. The flexibility of carbon nanotubes and the high hardness of titanium nitride relieve the mechanical stress in the alloying process when subjected to the external force generated by the volume expansion of silicon dioxide due to lithium insertion and extraction, and can maintain the structural integrity of the composite material, and maintain good electrical contact of the active particles and the stability of the surface film during repeated cycles.

[0050] (3) The porous structure of porous carbon and the conductivity of carbon nanotubes also shorten the path of lithium ions embedded in SiO, significantly increasing the ion exchange rate of the composite negative electrode material and improving the fast charging performance of lithium-ion batteries. DETAILED DESCRIPTION

[0051] The preparation method of the present invention will be described in further detail below with reference to specific examples. It should be understood that the following examples are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection intended by the present invention.

[0052] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the reagents, materials, etc. used in the following examples are all commercially available unless otherwise specified.

[0053] Example 1

[0054] (1) 100gSiO(D 50 6μm) was first heated to 900℃ under argon protection, and then the energy was 300eV and the beam current density was 0.4mA / cm 2 The SiO particles were bombarded with an ion beam at a distance of 4 mm from the ion beam to the SiO and a bombardment angle of 30°. The SiO particles were stirred and turned during the bombardment. The bombardment time was 40 min, and modified SiO was obtained after cooling.

[0055] (2) Modified SiO9g, Zn(NO3)20.9g, Fe(NO3)20.1g, dimethylimidazole 3g and 50mL methanol were mixed, stirred at room temperature for self-assembly reaction for 12 hours, centrifuged and washed, and dried in vacuum at 100°C to obtain material 1;

[0056] (3) 10 g of material 1 from step (2) was placed in a chemical vapor deposition furnace, and nitrogen was introduced at a flow rate of 600 mL / min. When the temperature reached 800°C, acetylene was introduced at a flow rate of 60 mL / min for 1 hour for chemical vapor deposition. After the reaction was completed, the acetylene flow was turned off, and the mixture was cooled to room temperature to obtain material 2; material 2 was soaked in a 1 mol / L nitric acid solution for 6 hours, and then washed, dehydrated, and dried in sequence to obtain material 3;

[0057] (4) 10 g of material 3 from step (3) was placed in a chemical vapor deposition furnace, and argon was introduced at a flow rate of 200 mL / min. When the temperature reached 800°C, hydrogen carrying TiCl4 was introduced at a flow rate of 100 mL / min (the flow rate of the Ti source carried by hydrogen was 10 g / mL), and nitrogen was introduced at a flow rate of 220 mL / min. After reacting for 40 minutes, the hydrogen flow rate was turned off, and then the mixture was cooled to room temperature to obtain a silicon oxide-based composite negative electrode material, wherein the silicon oxide-based composite negative electrode material includes SiO as a core, a porous carbon layer coated on the surface of the SiO, a carbon nanotube layer coated on the surface of the porous carbon layer, and a TiN layer coated on the surface of the carbon nanotube layer; wherein the thickness of the porous carbon layer is 60 nm, the thickness of the carbon nanotube layer is 8 nm, and the thickness of the TiN layer is 25 nm.

[0058] Example 2

[0059] (1) 100gSiO(D 50 4μm) was heated to 850℃ under argon protection, and then the energy was 300eV and the beam current density was 0.6mA / cm 2 The SiO particles were bombarded with an ion beam at a distance of 8 mm from the ion beam to the SiO and a bombardment angle of 80°. The SiO particles were stirred and turned at the same time. The bombardment time was 30 min, and modified SiO was obtained after cooling.

[0060] (2) Modified SiO9g, Zn(NO3)21g, Fe(NO3)20.1g, dimethylimidazole 3.6g and 80mL DMF were mixed, stirred at room temperature for 8 hours for self-assembly reaction, centrifuged and washed, and dried at 80°C in vacuum to obtain material 1;

[0061] (3) 10 g of material 1 from step (2) was placed in a chemical vapor deposition furnace, nitrogen was introduced at a flow rate of 280 mL / min, and after heating to 850°C, methane was introduced at a flow rate of 40 mL / min for 4 hours for chemical vapor deposition. After the reaction was completed, the methane flow was turned off, and the material was cooled to room temperature to obtain material 2; the material 2 was soaked in a 1 mol / L hydrochloric acid solution for 4 hours, and then washed, dehydrated and dried in sequence to obtain material 3;

[0062] (4) 10 g of material 3 of step (3) was placed in a chemical vapor deposition furnace, and argon was introduced at a flow rate of 200 mL / min. When the temperature reached 750°C, hydrogen carrying TiCl4 was introduced at a flow rate of 150 mL / min (the flow rate of the Ti source carried by hydrogen was 7.5 g / mL), and ammonia was introduced at a flow rate of 250 mL / min. After reacting for 30 minutes, the ammonia flow was turned off, and then cooled to room temperature to obtain a silicon oxide-based composite negative electrode material, wherein the silicon oxide-based composite negative electrode material includes SiO as a core, a porous carbon layer coated on the surface of SiO, a carbon nanotube layer coated on the surface of the porous carbon layer, and a TiN layer coated on the surface of the carbon nanotube layer; wherein the thickness of the porous carbon layer is 80 nm, the thickness of the carbon nanotube layer is 5 nm, and the thickness of the TiN layer is 20 nm.

[0063] Example 3

[0064] (1) 100gSiO(D 50 4μm) was heated to 850℃ under argon protection, and then the energy was 300eV and the beam current density was 0.6mA / cm 2 The SiO particles were bombarded with an ion beam at a distance of 8 mm from the ion beam to the SiO and a bombardment angle of 80°. The SiO particles were stirred and turned at the same time. The bombardment time was 30 min, and modified SiO was obtained after cooling.

[0065] (2) Modified SiO9 g, ZnCl2 0.8 g, FeSO4 0.1 g, dimethylimidazole 2.4 g and 60 mL of formaldehyde were mixed, stirred at room temperature for 14 hours for self-assembly reaction, centrifuged and washed, and dried at 90 ° C in vacuum to obtain material 1;

[0066] (3) 10 g of material 1 from step (2) was placed in a chemical vapor deposition furnace, nitrogen was introduced at a flow rate of 350 mL / min, and after heating to 800°C, ethane was introduced at a flow rate of 50 mL / min for 2.5 hours for chemical vapor deposition. After the reaction was completed, the ethane flow was turned off, and then cooled to room temperature to obtain material 2; material 2 was soaked in 1 mol / L sulfuric acid solution for 2 hours, and then washed, dehydrated and dried in sequence to obtain material 3;

[0067] (4) 10 g of material 3 of step (3) was placed in a chemical vapor deposition furnace, and argon was introduced at a flow rate of 200 mL / min. When the temperature reached 800°C, hydrogen carrying TiCl4 was introduced at a flow rate of 150 mL / min (the flow rate of the Ti source carried by hydrogen was 13 g / mL), and ammonia was introduced at a flow rate of 250 mL / min. After reacting for 30 minutes, the nitrogen flow was turned off, and then cooled to room temperature to obtain a silicon oxide-based composite negative electrode material, wherein the silicon oxide-based composite negative electrode material includes SiO as a core, a porous carbon layer coated on the surface of SiO, a carbon nanotube layer coated on the surface of the porous carbon layer, and a TiN layer coated on the surface of the carbon nanotube layer; wherein the thickness of the porous carbon layer is 50 nm, the thickness of the carbon nanotube layer is 6 nm, and the thickness of the TiN layer is 24 nm.

[0068] Comparative Example 1

[0069] (1) 100gSiO(D 50 6μm) was first heated to 900℃ under argon protection, and then the energy was 300eV and the beam current density was 0.4mA / cm 2 The SiO particles were bombarded with an ion beam at a distance of 4 mm from the ion beam to the SiO and a bombardment angle of 30°. The SiO particles were stirred and turned during the bombardment. The bombardment time was 40 min, and modified SiO was obtained after cooling.

[0070] (2) Modified SiO9g, Zn(NO3)20.9g, Fe(NO3)20.1g, dimethylimidazole 3g and 50mL methanol were mixed, stirred at room temperature for self-assembly reaction for 12 hours, centrifuged and washed, and dried in vacuum at 100°C to obtain material 1;

[0071] (3) 10 g of material 1 of step (2) is placed in a chemical vapor deposition furnace, and nitrogen is introduced at a flow rate of 600 mL / min. When the temperature reaches 800° C., acetylene is introduced at a flow rate of 60 mL / min for 1 hour for chemical vapor deposition. After the reaction is completed, the acetylene flow is turned off, and then cooled to room temperature to obtain material 2; after soaking material 2 in 1 mol / L nitric acid solution for 6 hours, the material is washed, dehydrated and dried in sequence to obtain a silicon oxide-based composite negative electrode material, wherein the silicon oxide-based composite negative electrode material includes SiO as a core, a porous carbon layer coated on the surface of the SiO, and a carbon nanotube layer coated on the surface of the porous carbon layer; wherein the thickness of the porous carbon layer is 60 nm, and the thickness of the carbon nanotube layer is 8 nm.

[0072] Comparative Example 2

[0073] (1) 100gSiO(D 506μm) was first heated to 900℃ under argon protection, and then the energy was 300eV and the beam current density was 0.4mA / cm 2 The SiO particles were bombarded with an ion beam at a distance of 4 mm from the ion beam to the SiO and a bombardment angle of 30°. The SiO particles were stirred and turned during the bombardment. The bombardment time was 40 min, and modified SiO was obtained after cooling.

[0074] (2) 10 g of material 1 from step (1) was placed in a chemical vapor deposition furnace, nitrogen was introduced at a flow rate of 600 mL / min, and when the temperature reached 800°C, acetylene was introduced at a flow rate of 60 mL / min for 1 hour for chemical vapor deposition. After the reaction was completed, the acetylene flow was turned off, and then cooled to room temperature to obtain material 1;

[0075] (3) Material 1 of step (2) is placed in a chemical vapor deposition furnace, and argon is introduced at a flow rate of 200 mL / min. When the temperature reaches 800°C, hydrogen carrying TiCl4 is introduced at a flow rate of 100 mL / min (the flow rate of the Ti source carried by the hydrogen is 10 g / mL), and nitrogen is introduced at a flow rate of 220 mL / min. After reacting for 40 minutes, the hydrogen flow rate is turned off, and then cooled to room temperature to obtain a silicon oxide-based composite negative electrode material, wherein the silicon oxide-based composite negative electrode material includes SiO as a core, a carbon layer coated on the surface of the SiO, and a TiN layer coated on the surface of the carbon layer; wherein the thickness of the carbon layer is 60 nm, and the thickness of the TiN layer is 25 nm.

[0076] Comparative Example 3

[0077] (1) 100gSiO(D 50 6μm) was first heated to 900℃ under argon protection, and then the energy was 300eV and the beam current density was 0.4mA / cm 2 The SiO particles were bombarded with an ion beam at a distance of 4 mm from the ion beam to the SiO and a bombardment angle of 30°. The SiO particles were stirred and turned during the bombardment. The bombardment time was 40 min, and modified SiO was obtained after cooling.

[0078] (2) Modified SiO9g, Zn(NO3)20.9g, Fe(NO3)20.1g, dimethylimidazole 3g and 50mL methanol were mixed, stirred at room temperature for self-assembly reaction for 12 hours, centrifuged and washed, and dried in vacuum at 100°C to obtain material 1;

[0079] (3) 10 g of material 1 from step (2) was placed in a high-temperature furnace, heated to 800° C., kept warm for 1 h, and then cooled to room temperature to obtain material 2; material 2 was soaked in 1 mol / L nitric acid solution for 6 h, and then washed, dehydrated, and dried in sequence to obtain material 3;

[0080] (4) 10 g of material 3 from step (3) was placed in a chemical vapor deposition furnace, and argon was introduced at a flow rate of 200 mL / min. When the temperature reached 800°C, hydrogen carrying TiCl4 was introduced at a flow rate of 100 mL / min (the flow rate of the Ti source carried by hydrogen was 10 g / mL), and nitrogen was introduced at a flow rate of 220 mL / min. After reacting for 40 minutes, the hydrogen flow rate was turned off, and then the mixture was cooled to room temperature to obtain a silicon oxide-based composite negative electrode material, wherein the silicon oxide-based composite negative electrode material includes SiO as a core, a porous carbon layer coated on the surface of the SiO, and a TiN layer coated on the surface of the porous carbon layer; wherein the thickness of the porous carbon layer is 60 nm, and the thickness of the TiN layer is 25 nm.

[0081] Performance testing:

[0082] Electrochemical performance test:

[0083] Semi-charge test method: The composite negative electrode materials prepared in Examples 1-3 were mixed uniformly in a mass ratio of conductive carbon black (SP): carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) (95:1:1.5:2.5), coated on copper foil, and dried in a 120°C vacuum drying oven for 12 hours. Simulated battery assembly was performed in an argon-protected Braun glove box. The electrolyte consisted of 1M LiPF6 + EC:DEC:DMC (1:1:1 by volume). A lithium metal sheet served as the counter electrode. Simulated battery testing was performed in a 5V, 10mA Xinwei battery test cabinet with charge and discharge voltages ranging from 0.01 to 1.5V and a charge and discharge rate of 0.1C. The first-cycle discharge capacity and first-cycle charge and discharge efficiency obtained are listed in Table 1.

[0084] Full battery test method: A full battery was assembled using the composite negative electrode material prepared in Examples 1 to 3 as the negative electrode, lithium cobalt oxide as the positive electrode, and 1M-LiPF6+EC:DEC:DMC (volume ratio 1:1:1) solution as the electrolyte. The battery was charged and discharged at room temperature at rates of 0.1C and 1C, with a voltage range of 3.0 to 4.2V. The cycle performance obtained from the test is listed in Table 1.

[0085] Table 1. Electrochemical performance test results

[0086]

[0087] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing a silicon oxide-based composite negative electrode material, characterized in that: The method comprises the following steps: (1) Modified SiO, zinc salt, iron salt, organic ligand and organic solvent are mixed and self-assembled to obtain material 1; the material 1 has a core-shell structure with modified SiO as a core and Zn / Fe-MOF as a shell; (2) placing the material 1 of step (1) into a chemical vapor deposition furnace, heating it under the protection of an inert gas, introducing an organic carbon source after heating it to the reaction temperature, and reacting to obtain material 2; (3) treating the material 2 of step (2) with acid to obtain a material 3; the material 3 has a core-shell structure with modified SiO as a core, porous carbon as an intermediate layer and carbon nanotubes as an outermost layer; (4) placing the material 3 of step (3) into a chemical vapor deposition furnace, heating it under the protection of an inert gas, introducing Ti source and N source gas after the temperature reaches the reaction temperature, and reacting to obtain a silicon oxide-based composite negative electrode material; In step (1), the mass ratio of the zinc salt to the organic ligand is 1:(2-4); the mass ratio of the zinc salt to the iron salt is (6-10):1; the volume ratio of the sum of the mass of the zinc salt and the organic ligand to the organic solvent is (0.01-0.1) g:1 mL; the mass ratio of the zinc salt to the modified SiO is 1:(7-10); In step (1), the modified SiO is prepared by the following method: SiO is first heated to 850~1000℃ under inert atmosphere, and then the energy is 100~600eV and the beam density is 0.4~0.8mA / cm 2 The ion beam is bombarded, the distance between the ion beam and the surface of the SiO particles is controlled to be 1-10 mm, the bombardment angle is 30-150°, and the SiO particles are stirred and turned during the bombardment. The bombardment time is 30-60 min. In step (2), the reaction temperature is 700°C to 800°C; In step (4), the reaction temperature is 700-850°C; The silicon oxide-based composite negative electrode material includes modified SiO as a core, a porous carbon layer coated on the surface of the modified SiO, a carbon nanotube layer coated on the surface of the porous carbon layer, and a TiN layer coated on the surface of the carbon nanotube layer.

2. The preparation method according to claim 1, characterized in that In step (1), micropores or irregular micro-pits exist on the surface of the modified SiO particles and / or between the modified SiO particles.

3. The preparation method according to claim 1, characterized in that In step (1), the thickness of the Zn / Fe-MOF shell of the material 1 is 30 nm to 100 nm.

4. The preparation method according to claim 1, characterized in that In step (2), the reaction time is 1 h to 10 h; and / or, in step (2), the organic carbon source is one or more of acetylene, ethylene, methane, ethane, propane and n-butane; And / or, in step (2), the volume ratio of the organic carbon source to the inert gas is 1:(5-10); And / or, in step (2), 3-8 mL / min of organic carbon source needs to be introduced per gram of material 1.

5. The preparation method according to claim 1, characterized in that In step (3), the acid is one or a combination of at least two of hydrochloric acid, acetic acid, carbonic acid or phosphoric acid; And / or, in step (3), the thickness of the porous carbon layer is 25-90 nm, and the thickness of the carbon nanotube layer is 3-10 nm.

6. The preparation method according to claim 1, characterized in that In step (4), the reaction time is 30 min to 60 min; And / or, in step (4), the Ti source is TiCl4, and the N source gas is nitrogen and / or ammonia; And / or, in step (4), the Ti source is carried by hydrogen into the chemical vapor deposition furnace, and the flow rate of the Ti source carried by hydrogen is 3-10 g / L; And / or, in step (4), 10-25 mL / min of N source gas needs to be introduced per gram of material 3; And / or, in step (4), the volume ratio of inert gas: N source gas: hydrogen is 1:(1-1.5):(0.4-0.8).

7. A silicon oxide-based composite negative electrode material prepared by the method according to any one of claims 1 to 6, wherein the silicon oxide-based composite negative electrode material comprises a modified SiO as a core, a porous carbon layer coated on the surface of the modified SiO, a carbon nanotube layer coated on the surface of the porous carbon layer, and a TiN layer coated on the surface of the carbon nanotube layer.

8. The silicon oxide-based composite negative electrode material according to claim 7, characterized in that: The thickness of the porous carbon layer is 25nm-90nm, the thickness of the carbon nanotube layer is 3nm-10nm, and the thickness of the TiN layer is 10nm-30nm.

9. A lithium-ion battery comprising the silicon oxide-based composite negative electrode material according to claim 7 or 8.

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