CN111564616A

CN111564616A - AgNWs @ Si @ GO lithium ion battery cathode material, preparation method thereof and lithium ion battery adopting same

Info

Publication number: CN111564616A
Application number: CN202010415558.1A
Authority: CN
Inventors: 魏剑; 秦葱敏; 庞欣; 乔师帅; 陈甜甜; 张雪萍; 姜超; 张昊
Original assignee: Xian University of Architecture and Technology
Current assignee: Xian University of Architecture and Technology
Priority date: 2020-05-16
Filing date: 2020-05-16
Publication date: 2020-08-21

Abstract

The invention relates to an AgNWs @ Si @ GO lithium ion battery cathode material, a preparation method thereof and a lithium ion battery using the same, and belongs to the field of preparation of lithium ion battery cathode materials. The AgNWs @ Si @ GO composite anode material comprises an inner core and an outer shell, wherein the inner core is AgNWs, the outer shell is a Si @ GO composite body, and the Si @ GO composite body is coated on the AgNWs inner core, so that the specific surface area is reduced, direct contact between silicon and electrolyte is prevented, an unstable SEI film is avoided, and the first charge-discharge efficiency is improved. The lithium ion battery prepared from the AgNWs @ Si @ GO composite anode material has the advantages of high specific capacity, high first-time efficiency, good cycle performance and the like.

Description

AgNWs @ Si @ GO lithium ion battery cathode material, preparation method thereof and lithium ion battery adopting same

Technical Field

The invention belongs to the technical field of lithium ion battery cathode materials, relates to a Si/C composite cathode material and preparation thereof, and particularly relates to an AgNWs @ Si @ GO lithium ion battery cathode material, preparation thereof and a lithium ion battery adopting the same.

Background

In new energy automobiles, a lithium ion battery is required to have higher energy density, and a negative electrode is an important component forming the lithium ion battery, and the current marketable negative electrode material mainly comprises a graphite material, but the improvement of the energy density of the lithium ion battery is limited by the lower gram capacity of the graphite material. The core-shell type Si/C composite negative electrode material is emphasized by researchers by the advantages of high gram capacity, good cycling stability and the like, and is applied to the fields of high-specific energy density lithium ion batteries and the like, but the core-shell type Si/C composite negative electrode material has high volume expansion rate and poor conductivity and becomes a main obstacle limiting the wide application of the core-shell type Si/C composite negative electrode material. The main measures for reducing the expansion of silicon materials at present are as follows: (1) coating a carbon layer on the surface of the silicon material to reduce the expansion rate of the silicon material; (2) preparing a Si/C composite material with a porous structure to relieve the volume expansion of silicon; (3) the material with low expansion rate and good conductivity, such as Graphene Oxide (GO), Carbon Nanotubes (CNTs) and other materials, is coated to reduce the volume expansion of silicon in the charging and discharging process. Although the above method relieves the volume expansion of silicon to some extent, the effect is not significant, and the expansion rate is still high compared with the carbon-based material with good cycle performance, so that it is difficult to widely apply the method.

The patent No. 2012104040070, the chinese invention patent, discloses a preparation method and application of a silicon-carbon composite negative electrode material for a lithium ion battery, the negative electrode material is a core-shell structure, comprising a core body, an intermediate layer and an outermost layer, the intermediate layer and the outermost layer are sequentially coated on the core body, the core body is nano-silicon, the intermediate layer is amorphous carbon, the outermost layer is a one-dimensional nano-carbon material, but the silicon-carbon composite negative electrode material has a high expansion rate, so that the electric conductivity, the cycle performance and the like of the silicon-carbon composite negative electrode material still need to be further improved.

The invention patent of China with the patent number of 2017103568886 discloses a porous silicon-carbon composite material and a preparation method and application thereof, wherein the material is obtained by firstly obtaining porous silicon from iron-silicon alloy through mechanical ball milling and acid etching, then compounding the porous silicon with an organic carbon source through a spray pelletizing process, and then carbonizing at high temperature. Although the capacity, the first coulombic efficiency and the cycle performance of the material are improved to a certain extent, the effect is not obvious, and the tap density of the material is lowered and the electronic conductivity is deviated due to pore forming, so that the improvement of the energy density of the material is influenced.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide an AgNWs @ Si @ GO lithium ion battery anode material, a preparation method thereof and a lithium ion battery adopting the anode material, wherein the material has larger specific surface area, tap density and conductivity, and therefore has higher energy density and cycle performance.

In order to achieve the purpose, the invention adopts the technical scheme that:

the AgNWs @ Si @ GO lithium ion battery anode material comprises an inner core and an outer shell, wherein the inner core is a silver nanowire (AgNWs), the outer shell is a Si @ GO complex, Si is completely coated on the silver nanowire, and a GO part is coated on a Si layer.

The mass of the silver nanowires is 20-30% of that of the negative electrode material.

The mass ratio of Si to GO in the shell is 1:1, the thickness of the shell is 80nm, and the diameter of the core is 40-100 nm.

The invention also provides a preparation method of the AgNWs @ Si @ GO lithium ion battery anode material, which comprises the following steps:

step 1), adopting PVP and AgNO₃And FeCl₃·6H₂O preparation of silver nanoparticles by polyol processThe wire and the silver nanowire have the characteristic of high conductivity, and the conductivity of the composite material can be improved.

Step 2), coating a silicon dioxide layer on the surface of the obtained silver nanowire by a TEOS hydrolysis principle to obtain AgNWs @ SiO₂A composite material.

Step 3), the obtained AgNWs @ SiO₂Reducing the silicon dioxide layer of the shell into silicon by the composite material through a magnesiothermic reduction method to obtain an AgNWs @ Si composite material; the silica layer is reduced into silicon by TEOS hydrolysis coating silica and magnesiothermic reduction, and the capacity and the cycling stability of the composite material are improved by utilizing the advantages of high specific capacity and the like of the silicon.

And 4), coating a carbon layer on the AgNWs @ Si composite material to obtain the AgNWs @ Si @ GO composite material which can be used as a lithium ion battery cathode, and by utilizing the characteristics of high conductivity, good chemical stability and the like of carbon, the volume expansion of silicon can be relieved, the generation of an unstable solid electrolyte interface film can be avoided, the structural stability of the composite material can be further improved, and the electrochemical performance of the composite material can be improved to a certain extent.

Specifically, the method comprises the following steps:

in the step 1), the silver nanowires are prepared by the following steps: 0.3g PVP in total mass is composed of 0.1g PVP-K30 and 0.2g PVP1300000, all added to 50mL of ethylene glycol solution and stirred continuously until completely dissolved, then 0.2g AgNO is added₃Continuously stirring until the mixture is completely dissolved, and then adding 5-10mL of FeCl with the concentration of 0.002-0.004 g/mL₃·6H₂Stirring the ethylene glycol solution of O for 3min to obtain a mixed solution, pouring the mixed solution into a 200mL three-necked bottle, reacting for 1.5h at 160 ℃ in an oil bath pot to obtain a silver nanowire product, washing the silver nanowire product with acetone, ethanol and deionized water in sequence, and dispersing the silver nanowire product in ethanol according to the volume ratio of 1:5 of the silver nanowire to the ethanol to obtain a silver nanowire ethanol solution for later use.

In the step 2), 300 mu L of TEOS and 10mL of absolute ethanol are prepared into ethanol solution, and the ethanol solution is gradually and gradually added into the ethanol solution of the silver nanowires obtained in the step 1) and continuously stirred for 24 hours.

In the step 3), AgNWs @ SiO is firstly added₂Drying the composite material in a vacuum oven at 80 ℃ for 6h, and then AgNWs @ SiO in mass ratio₂The composite material is prepared by mixing magnesium powder in a proportion of 1: 2-1: 4 in a mortar by using ethanol, drying the uniformly mixed solution, and then putting the dried solution in a medium temperature furnace in an H mode₂Ar/H content of 3%₂Carrying out magnesiothermic reduction under a mixed atmosphere, wherein the reduction conditions are as follows: keeping the temperature at 650 ℃ for 4h, and increasing the temperature rate at 2 ℃/min.

In the step 4), the GO and AgNWs @ Si composite material is subjected to ultrasonic dispersion for 30min and 10min respectively to obtain a GO suspension and an AgNWs @ Si composite dispersion, and then mixing treatment is carried out.

The specific method of the mixing treatment comprises the following steps: the GO suspension and AgNWs @ Si composite dispersion were mixed, sonicated for 5-10min to give a composite, then vacuum filtered to dry the surface of the composite, and the resulting composite was dried in a vacuum oven at 80 ℃, and finally etched with HF.

In the process, the diameter of the core AgNWs is about 40-100 nm, and the SiO coated₂Is about 40nm, and SiO₂In the process of reduction to Si, the thickness is increased to 60nm due to impurities of magnesium oxide and magnesium silicate, the thickness of the coated GO layer is about 20nm, and the thickness of the finally obtained shell is about 80 nm.

The invention also claims a lithium ion battery adopting the AgNWs @ Si @ GO lithium ion battery cathode material.

Compared with the prior art, the invention has the beneficial effects that:

1. the negative electrode material improves the conductivity of the composite material by utilizing the high conductivity of AgNWs, improves the specific capacity by utilizing the characteristic of nano silicon, and relieves the volume expansion of the silicon by utilizing the carbon layer so as to improve the structural stability of the composite material.

2. According to the invention, the anode material is of a core-shell structure, the Si @ GO composite body is coated outside the core of AgNWs, on one hand, the core AgNWs has high conductivity, and on the other hand, the nano-silicon of the middle layer has high specific surface area, so that the specific surface area of the core can be reduced through coating, the generation of an unstable solid electrolyte interface film is reduced, and the side reaction of the core is further reduced; on the other hand, the coating of the carbon layer can effectively avoid the direct contact of the silicon layer and the electrolyte, reduce the occurrence of side reaction and improve the first charge-discharge efficiency and the cycle stability.

3. According to the preparation method of the cathode material, the surface of AgNWs is coated with the Si @ GO shell, and in the preparation method, TEOS ethanol solution is gradually and gradually added into AgNWs ethanol solution, so that the generation of silicon dioxide balls can be reduced.

4. The cathode material prepared by the preparation method disclosed by the invention is high in conductivity, specific capacity and first charge-discharge efficiency, good in cycle stability and good in application prospect in the field of lithium ion battery cathode materials.

Drawings

FIG. 1 is a flow chart of the present invention.

FIG. 2 is a scanning electron micrograph (whole) of the AgNWs @ Si @ GO composite material prepared in example 2 of the present invention.

FIG. 3 is a scanning electron micrograph (single) of the AgNWs @ Si @ GO composite material prepared in example 2 of the present invention.

FIG. 4 is a transmission electron micrograph of the AgNWs @ Si @ GO composite material prepared in example 2 of the present invention.

FIG. 5 shows AgNWs @ Si @ GO composite material and AgNWs @ SiO prepared in example 2 of the present invention₂And AgNWs @ Si cycles.

FIG. 6 shows AgNWs @ Si @ GO composite material and AgNWs @ SiO prepared in example 2 of the present invention₂And AgNWs @ Si magnification comparison plot.

FIG. 7 shows AgNWs @ Si @ GO composite material and AgNWs @ SiO prepared in example 2 of the present invention₂And AgNWs @ Si impedance vs.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to the drawings and examples.

Example 1

The AgNWs @ Si @ GO lithium ion battery anode material comprises an inner core and a shell coated outside the inner core, wherein the inner core is AgNWs, and the shell is a Si @ GO complex; the mass of AgNWs accounts for about 10% of the mass of the Si/C composite material; the thickness of the shell is 50nm, the diameter of the inner core is 40-100 nm, and the mass ratio of the Si @ GO complex is about 1:1.

Referring to fig. 1, the preparation method of the AgNWs @ Si @ GO lithium ion battery anode material in the embodiment includes the following steps:

1) preparation of AgNWs

Uniformly dissolving 0.3g of PVP-K30 and PVP-1300000 in total into 50mL of ethylene glycol solution, and adding 0.2g of AgNO₃And stirring uniformly to form a mixed solution. FeCl with the concentration of 0.0002g/mL₃·6H₂And (3) dropwise adding an O-glycol solution into the mixed solution, and stirring for 3-5 min. Then, the mixed solution was placed in a 200mL three-necked flask and reacted at 160 ℃ for 1.5 hours to grow AgNWs. And finally, sequentially passing the mixed solution containing AgNWs obtained by the reaction through acetone, ethanol and deionization, and carrying out centrifugal washing to obtain the AgNWs.

2)AgNWs@SiO₂Preparation of

Dispersing the AgNWs prepared in the step 1) into ethanol to form an AgNWs ethanol solution. Then, 5mL of deionized water, 5mL of ammonia water, and 0.002mL of TEOS were added to 10mL of AgNWs ethanol solution (AgNWs and ethanol were mixed at a volume ratio of 1: 5) respectively and stirred for 24 h. Washing the centrifugal product by using absolute ethyl alcohol to obtain AgNWs @ SiO₂A composite material.

3) Preparation of AgNWs @ Si

AgNWs @ SiO prepared in the step 2)₂Drying the composite material in a vacuum oven at 80 ℃ for 10H, uniformly mixing the obtained dry powder and magnesium powder according to the mass ratio of 1:1, and carrying out Ar/H₂Reacting for 4h at 650 ℃ under the protection of mixed atmosphere to obtain the AgNWs @ Si composite material.

4) Preparation of AgNWs @ Si @ GO

Mixing the AgNWs @ Si composite material prepared in the step 3) with GO according to the mass ratio of 1:1, and performing ultrasonic treatment, vacuum filtration and tubular furnace inert atmosphere high-temperature treatment to obtain the AgNWs @ Si @ GO composite material.

Example 2

The AgNWs @ Si @ GO lithium ion battery anode material comprises an inner core and a shell coated outside the inner core, wherein the inner core is an AgNWs shell and is a Si @ GO complex; the mass of AgNWs accounts for 20% of the mass of the Si/C composite material; the thickness of the shell is 60nm, the diameter of the inner core is 40-100 nm, and the mass ratio of the Si @ GO complex is 1: 2.

1) preparation of AgNWs

Uniformly dissolving 0.3g of PVP-K30 and PVP-1300000 in total into 50mL of ethylene glycol solution, and adding 0.2g of AgNO₃And stirring uniformly to form a mixed solution. FeCl with the concentration of 0.0003g/mL₃·6H₂And (3) dropwise adding an O-glycol solution into the mixed solution, and stirring for 3-5 min. Then, the mixed solution was placed in a 200mL three-necked flask and reacted at 160 ℃ for 1.5 hours to grow AgNWs. And finally, sequentially passing the mixed solution containing AgNWs obtained by the reaction through acetone, ethanol and deionization, and carrying out centrifugal washing to obtain the AgNWs.

2)AgNWs@SiO₂Preparation of

Dispersing the AgNWs prepared in the step 1) into ethanol to form an AgNWs ethanol solution. Then 5mL of deionized water, 5mL of ammonia water, and 0.003mL of TEOS were added to 20mL of the AgNWs ethanol solution, respectively, and stirred for 24 h. Washing the centrifugal product by using absolute ethyl alcohol to obtain AgNWs @ SiO₂A composite material.

3) Preparation of AgNWs @ Si

AgNWs @ SiO prepared in the step 2)₂Drying the composite material in a vacuum oven at 80 ℃ for 10H, uniformly mixing the obtained dry powder and magnesium powder according to the mass ratio of 1:1.5, and carrying out Ar/H treatment on the mixture₂And reacting for 4 hours at 625 ℃ under the protection of mixed atmosphere to obtain the AgNWs @ Si composite material.

4) Preparation of AgNWs @ Si @ GO

SEM and TEM tests are carried out on the AgNWs @ Si @ GO negative electrode material prepared in the embodiment, and the results are shown in fig. 2, fig. 3 and fig. 4.

From fig. 2, 3 it can be seen that the composite material has a better core-shell structure, with only a small fraction of incompletely exfoliated GO present.

The presence of different cladding layers for AgNWs, Si and GO is clear from fig. 4.

Obviously, the obtained material has a core-shell structure and a better appearance.

The materials obtained in the steps of the present example were subjected to cycle, rate and impedance tests, and the results are shown in fig. 5, 6 and 7, respectively.

As can be seen from FIG. 5, AgNWs @ SiO₂The initial discharge specific capacities of AgNWs @ Si and AgNWs @ Si @ GO are 217.2mAh/g, 681.8mAh/g and 1161.2mAh/g respectively. The AgNWs @ Si @ GO composite material has good cycle stability, and the capacity retention rate is 74.7% after 70 cycles.

From FIG. 6, it can be seen that AgNWs @ SiO₂The specific capacities of AgNWs @ Si and AgNWs @ Si @ GO are all reduced along with the increase of the multiplying power. But when the multiplying power returns to the initial value, the specific capacity is improved. When the multiplying power of the AgNWs @ Si @ GO composite material returns to 0.1C, the specific capacity of the AgNWs @ Si @ GO composite material returns to 803.2 mAh/g. Lower than the initial specific capacity because the composite electrode structure is partially destroyed during cycling. And the reversible specific capacity of the AgNWs @ Si @ GO composite material is better than that of AgNWs @ SiO₂And AgNWs @ Si composites.

From FIG. 7, the exchange resistance ratio AgNWs @ Si @ GO composite material AgNWs @ SiO₂And the AgNWs @ Si composite. And the linear slope of the AgNWs @ Si @ GO composite material is the largest, which indicates that the diffusion rate of ions in the material is the fastest.

Obviously, the AgNWs @ Si @ GO negative electrode material has high initial specific capacity, high initial coulombic efficiency, minimum impedance and high stability in a circulation process.

Example 3

The AgNWs @ Si @ GO lithium ion battery anode material comprises an inner core and a shell coated outside the inner core, wherein the inner core is AgNWs, and the shell is a Si @ GO complex; the mass of AgNWs accounts for 30% of the mass of the Si/C composite material; the thickness of the shell is 80nm, the diameter of the inner core is 40-100 nm, and the mass ratio of the Si @ GO complex is 1: 3.

1) preparation of AgNWs

Uniformly dissolving 0.3g of PVP-K30 and PVP-1300000 in total into 50mL of ethylene glycol solution, and adding 0.2g of AgNO₃And stirring uniformly to form a mixed solution. FeCl with the concentration of 0.0004g/mL₃·6H₂And (3) dropwise adding an O-glycol solution into the mixed solution, and stirring for 3-5 min. Then, the mixed solution was placed in a 200mL three-necked flask and reacted at 160 ℃ for 1.5 hours to grow AgNWs. And finally, sequentially passing the mixed solution containing AgNWs obtained by the reaction through acetone, ethanol and deionization, and carrying out centrifugal washing to obtain the AgNWs.

2)AgNWs@SiO₂Preparation of

Dispersing the AgNWs prepared in the step 1) into ethanol to form an AgNWs ethanol solution. Then 5mL of deionized water, 5mL of ammonia water, and 0.004mL of TEOS were added to 30mL of AgNWs ethanol solution, respectively, and stirred for 24 h. Washing the centrifugal product by using absolute ethyl alcohol to obtain AgNWs @ SiO₂A composite material.

3) Preparation of AgNWs @ Si

AgNWs @ SiO prepared in the step 2)₂Drying the composite material in a vacuum oven at 80 ℃ for 10H, uniformly mixing the obtained dry powder and magnesium powder according to the mass ratio of 1:2, and carrying out Ar/H₂Reacting for 4h at 675 ℃ under the protection of mixed atmosphere to obtain the AgNWs @ Si composite material.

4) Preparation of AgNWs @ Si @ GO

Mixing the AgNWs @ Si composite material prepared in the step 3) with GO according to the mass ratio of 1:2, and carrying out ultrasonic treatment, vacuum filtration and tubular furnace inert atmosphere high-temperature treatment to obtain the AgNWs @ Si @ GO composite material.

Respectively assembling the composite negative electrode materials obtained in the embodiments 1-3 into button cells A1, A2, A3 and corresponding negative electrode plates thereof; the preparation method comprises the following steps: and adding a binder, a conductive agent and an organic solvent into the negative electrode material, fully stirring, mixing, pulping, coating on a copper foil, drying and rolling to obtain the pole piece. The used binder is PVDF, the conductive agent is conductive carbon black, and the cathode isThe materials are respectively the cathode materials prepared in the embodiments 1-3, the solvent is DMF, and the proportion is as follows: negative electrode active material: conductive carbon black: PVDF-8: 1: 1; the electrolyte is LiPF₆Carbonate (EC) + dimethyl carbonate (DMC) + Ethyl Methyl Carbonate (EMC); the diaphragm is a microporous polypropylene diaphragm, and the anode is a lithium sheet, and is processed into the CR2025 button cell.

The lithium ion battery is charged and discharged by adopting a current density of 0.2C, the voltage range is 0.01-1.5V, the maximum lithium intercalation capacity is 1384.8mAh/g, the lithium removal capacity is 1125.3mAh/g, and the primary coulombic efficiency is 96.7%. After 60 cycles, the lithium insertion capacity is 993mAh/g, and the lithium removal capacity is 976.3 mAh/g.

In conclusion, the core-shell structure AgNWs @ Si @ GO negative electrode material has good structural stability, has high specific capacity and excellent cycling stability when used as a lithium ion battery negative electrode material, and can be used as a battery negative electrode material.

The foregoing is only an example of some embodiments of the present invention, and it will be apparent to those skilled in the art of lithium batteries that some changes and modifications may be made without departing from the technical principles of the present invention, and such changes and modifications should also be considered as within the scope of the present invention.

Claims

1. The AgNWs @ Si @ GO lithium ion battery anode material is characterized by comprising an inner core and an outer shell, wherein the inner core is a silver nanowire (AgNWs), the outer shell is a Si @ GO complex, Si is completely coated on the silver nanowire, and a GO part is coated on a Si layer.

2. The AgNWs @ Si @ GO lithium ion battery anode material as claimed in claim 1, wherein the mass of the silver nanowires is 20-30% of the mass of the anode material.

3. The AgNWs @ Si @ GO lithium ion battery anode material as claimed in claim 1, wherein the mass ratio of Si to GO in the shell is 1:1, the thickness of the shell is 80nm, and the diameter of the core is 40-100 nm.

4. The preparation method of the AgNWs @ Si @ GO lithium ion battery anode material of claim 1, which is characterized by comprising the following steps:

step 1), adopting PVP and AgNO₃And FeCl₃·6H₂O, preparing silver nanowires by a polyol method;

step 2), coating a silicon dioxide layer on the surface of the obtained silver nanowire by a TEOS hydrolysis principle to obtain AgNWs @ SiO₂A composite material;

step 3), the obtained AgNWs @ SiO₂Reducing the silicon dioxide layer of the shell into silicon by the composite material through a magnesiothermic reduction method to obtain an AgNWs @ Si composite material;

and 4) coating a carbon layer on the AgNWs @ Si composite material to obtain the AgNWs @ Si @ GO lithium ion battery cathode material.

5. The preparation method of the AgNWs @ Si @ GO lithium ion battery anode material as claimed in claim 1, wherein in the step 1), the silver nanowires are prepared by the following steps: 0.3g PVP in total mass of 0.1g PVP-K30 and 0.2g PVP-1300000, all added to 50mL of ethylene glycol solution and stirred continuously until completely dissolved, then 0.2g AgNO was added₃Continuously stirring until the mixture is completely dissolved, and then adding 5-10mL of FeCl with the concentration of 0.002-0.004 g/mL₃·6H₂Stirring the ethylene glycol solution of O for 3min to obtain a mixed solution, pouring the mixed solution into a 200mL three-necked bottle, reacting for 1.5h at 160 ℃ in an oil bath pot to obtain a silver nanowire product, washing the silver nanowire product with acetone, ethanol and deionized water in sequence, and dispersing the silver nanowire product in ethanol according to the volume ratio of 1:5 of the silver nanowire to the ethanol to obtain a silver nanowire ethanol solution for later use.

6. The preparation method of the AgNWs @ Si @ GO lithium ion battery anode material as claimed in claim 1, wherein in the step 2), 300 μ L of TEOS and 10mL of absolute ethanol are prepared into an ethanol solution, and the ethanol solution is gradually added dropwise into the silver nanowire ethanol solution obtained in the step 1) and is continuously stirred for 24 hours.

7. The preparation method of AgNWs @ Si @ GO lithium ion battery anode material according to claim 1, wherein in the step 3), AgNWs @ SiO is firstly carried out₂Drying the composite material in a vacuum oven at 80 ℃ for 6h, and then AgNWs @ SiO in mass ratio₂The composite material is prepared by mixing magnesium powder in a proportion of 1: 2-1: 4 in a mortar by using ethanol, drying the uniformly mixed mixture, and putting the dried mixture in a medium temperature furnace in an H mode₂Ar/H with volume content of 3%₂Carrying out magnesiothermic reduction under a mixed atmosphere, wherein the reduction conditions are as follows: keeping the temperature at 650 ℃ for 4h, and increasing the temperature rate at 2 ℃/min.

8. The preparation method of the AgNWs @ Si @ GO lithium ion battery anode material according to claim 1, wherein in the step 4), the GO and AgNWs @ Si composite material are ultrasonically dispersed for 30min and 10min respectively to obtain a GO suspension and an AgNWs @ Si composite material dispersion suspension, and then mixing treatment is performed.

9. The preparation method of the AgNWs @ Si @ GO lithium ion battery anode material as claimed in claim 8, wherein the specific method of the mixing treatment is as follows: mixing the GO suspension and the AgNWs @ Si composite dispersion suspension, carrying out ultrasonic treatment for 5-10min to obtain a composite suspension, then carrying out vacuum filtration to dry the surface of the composite, drying the obtained composite in a vacuum oven at 80 ℃, and finally etching by using HF.

10. A lithium ion battery employing the AgNWs @ Si @ GO lithium ion battery anode material of claim 1.