WO2024001153A1

WO2024001153A1 - Negative electrode material and preparation method therefor, and lithium ion battery

Info

Publication number: WO2024001153A1
Application number: PCT/CN2023/071107
Authority: WO
Inventors: 郭松涛; 庞春雷; 任建国; 贺雪琴
Original assignee: 贝特瑞新材料集团股份有限公司; 惠州市鼎元新能源科技有限公司
Priority date: 2022-06-28
Filing date: 2023-01-06
Publication date: 2024-01-04
Also published as: CN117352671A

Abstract

The present disclosure provides a negative electrode material and a preparation method therefor, and a lithium ion battery. The negative electrode material comprises a silicon-based active substance and a composite coating layer located on a surface of the silicon-based active substance, and the composite coating layer comprises a polyphenol compound and a flexible polymer containing a polar group. According to the negative electrode material and the preparation method therefor, and the lithium ion battery provided by the present disclosure, the volume expansion of a silicon-based negative electrode material can be effectively inhibited, the hydrophilicity of the material is improved, and the improvement of the electrochemical performance of the material is facilitated.

Description

Negative electrode material and preparation method thereof, lithium-ion battery

Cross-references to related applications

This disclosure claims priority to the Chinese patent application with application number CN202210753470. in this disclosure.

Technical field

The present disclosure relates to the technical field of negative electrode materials, specifically, to negative electrode materials and preparation methods thereof, and lithium-ion batteries.

Background technique

Silicon-based anode materials are currently the most promising anode materials for lithium-ion batteries. They overcome the shortcomings of graphite's low specific capacity and silicon element's relatively poor cycle and rate performance, and have good safety and a wide range of raw material sources. . However, silicon-based anode materials have a volume expansion rate of about 200% during cycling. How to reduce the volume expansion of silicon-based anode materials has always been a research hotspot in the industry.

Contents of the invention

In view of this, the present disclosure provides negative electrode materials, preparation methods thereof, and lithium-ion batteries, which can effectively suppress the volume expansion of silicon-based negative electrode materials, improve the hydrophilicity of the materials, and help improve the electrochemical properties of the materials.

The present disclosure provides a negative electrode material. The negative electrode material includes a silicon-based active material and a composite coating layer located on the surface of the silicon-based active material. The composite coating layer includes a polyphenol compound and a polar group-containing compound. Flexible polymer.

Optionally, the silicon-based active material includes silicon-based active particles, and the silicon-based active particles include at least one of Si, SiO _x and silicon alloy, where 0<x<2.

Optionally, the silicon-based active material includes silicon-based active particles and carbon materials.

Optionally, the carbon material includes at least one of amorphous carbon, amorphous carbon material and graphitized carbon material.

Optionally, the carbon material is located on the surface of the silicon-based active particles to form a carbon layer.

Optionally, the carbon material forms a buffer skeleton inside the silicon-based active material, and the silicon-based active particles are distributed around the buffer skeleton.

Optionally, the silicon-based active material includes silicon-based active particles and carbon material, and the mass ratio of the silicon-based active particles to the carbon material is (30-97): (3-70).

Optionally, the thickness of the carbon layer is 1 nm to 1000 nm.

Optionally, the polyphenolic compound is connected to the carbon material in the silicon-based active material through π bonds, and the polyphenolic compound is graft-connected to the flexible polymer through covalent bonds.

Optionally, the polyphenolic compounds include compounds containing multiple phenolic hydroxyl groups.

Optionally, the polyphenolic compound includes at least one of polydopamine, polypyrogallol, polychlorogenic acid, polygallic acid, polycatechin, polylevodopa and polytannic acid.

Optionally, the polyphenolic compound includes oligomers and/or polymers polymerized from polyphenol monomers.

Optionally, the polyphenol monomers include flavonoids, and the flavonoids include at least one of flavones, isoflavones, flavanones, flavanols, flavanonols, anthocyanins and chalcones. kind.

Optionally, the flexible polymer includes polyolefin and its derivatives, polyvinyl alcohol and its derivatives, polyacrylic acid and its derivatives, polyamide and its derivatives, carboxymethylcellulose and its derivatives, seaweed At least one of acids and their derivatives.

Optionally, the polar group includes at least one of amino, carboxyl, hydroxyl and ethoxy.

Optionally, the composite coating layer includes an inner region close to the silicon-based active material and an outer region far away from the silicon-based active material, wherein the content of polyphenolic compounds in the inner region is higher than that of the silicon-based active material. Content of polyphenols in the outer zone.

Optionally, the composite coating layer includes a first coating layer and a second coating layer that are sequentially stacked on the surface of the silicon-based active material, and the first coating layer is close to the silicon-based active material, The first coating layer includes a polyphenol compound, and the second coating layer includes a flexible polymer containing polar groups.

Optionally, the thickness of the composite coating layer is 1 nm to 1000 nm.

Optionally, the contact angle between the negative electrode material and water is θ, θ≤60°.

Optionally, the contact angle between the negative electrode material and the electrolyte is eta, eta ≤ 90°; wherein the electrolyte includes ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and lithium hexafluorophosphate, and the lithium hexafluorophosphate is The concentration in the electrolyte is 1 mol/L.

Optionally, the contact angle between the negative electrode material and water is θ, and the contact angle between the negative electrode material and the electrolyte is eta, and satisfies (η + θ) ≤ 120°, wherein the electrolyte includes ethylene carbonate. , methyl ethyl carbonate, dimethyl carbonate and lithium hexafluorophosphate, and the concentration of the lithium hexafluorophosphate in the electrolyte is 1 mol/L.

Optionally, in the Raman spectrum, the negative electrode material has a carbon characteristic peak G and a silicon characteristic peak A, and the peak intensity I _A of the silicon characteristic peak A is equal to the peak intensity I _{G of the carbon characteristic peak G.} The ratio I _A /I _G is 0.2 to 4.

Optionally, the composite coating layer includes an amino group. In the X-ray photoelectron spectrum, the negative electrode material has silicon characteristic peaks and nitrogen characteristic peaks. The peak area of the silicon characteristic peak is S1, and the peak area of the nitrogen characteristic peak is S1. The area is S2, 1<S1/S2<10.

Optionally, the co-coating layer includes an amino group. In the X-ray photoelectron spectrum, the negative electrode material has C-O bond characteristic peaks and N-C=O bond characteristic peaks. The peak area of the C-O bond characteristic peak is S3. The peak area of the N-C=O bond characteristic peak is S4, and S3/S4<10.

Optionally, the flexible polymer includes polyacrylamide, and the polyphenolic compound includes polydopamine.

Optionally, after adding 20 g of negative electrode material to 300 ml of water, stirring and washing, the carbon element change amount ΔC of the composite coating layer of the negative electrode material is ≤ 2%.

Optionally, the mass content of carbon element in the negative electrode material is 1% to 50%.

Optionally, the specific surface area of the negative electrode material is 0.1 m ² /g ~ 10 m ² /g.

Optionally, the tap density of the negative electrode material is 0.5g/cm ³ to 1.5g/cm ³ .

Optionally, the average particle size of the negative electrode material is 0.2 μm ~ 50.0 μm.

The present disclosure also provides a method for preparing anode material, which method includes:

The raw materials containing silicon-based active material, polyphenol monomer, and flexible polymer containing polar groups are coated in a solution to obtain a negative electrode material.

Optionally, the polyphenol monomer includes at least one of flavonoids, dopamine hydrochloride, pyrogallol, chlorogenic acid, gallic acid, ellagic acid, catechin, levodopa and tannic acid. .

Optionally, the silicon-based active material includes silicon-based active particles and carbon material, and the carbon material includes at least one of amorphous carbon, amorphous carbon material and graphitized carbon material.

Optionally, the silicon-based active material includes silicon-based active particles and carbon material, and the carbon material is located on the surface of the silicon-based active particles to form a carbon layer.

Optionally, the silicon-based active material includes silicon-based active particles and carbon material, the carbon material forms a buffer skeleton inside the silicon-based active material, and the silicon-based active particles are distributed around the buffer skeleton.

Optionally, the silicon-based active material includes silicon-based active particles and carbon material. The carbon material is located on the surface of the silicon-based active particles to form a carbon layer. The thickness of the carbon layer is 1 nm to 1000 nm.

Optionally, the solution includes a pH adjuster.

Optionally, the pH value of the solution is 7-11.

Optionally, the solution further includes a solvent.

Optionally, the solvent includes at least one of water, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran and dimethyl sulfoxide.

Optionally, the solution includes a pH adjuster, which includes tris-hydroxymethylaminomethane-hydrochloride buffer, sodium barbiturate-hydrochloride buffer, glycine-sodium hydroxide buffer, borax-hydroxide At least one of sodium buffer, sodium carbonate-sodium bicarbonate buffer, ammonia water, sodium hydroxide solution, potassium hydroxide solution and lithium hydroxide solution.

Optionally, the mass ratio of the polyphenol monomer, the flexible polymer and the silicon-based active material is (0.1-15): (0.1-15): 100.

Optionally, the coating treatment is performed under stirring conditions.

Optionally, the coating treatment is performed under stirring conditions, and the stirring includes at least one of mechanical stirring and ultrasonic stirring.

Optionally, the coating is performed under stirring conditions, and the stirring is performed under conditions of 10°C to 100°C.

Optionally, after the raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in the solution, the method further includes separating the solution. , to obtain the isolated product.

Optionally, the separation includes at least one of normal pressure filtration, reduced pressure filtration, and centrifugation.

Optionally, after the raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in the solution, the method further includes separating the solution. , and wash the separated product with water.

Optionally, after the raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in the solution, the method further includes separating the solution. , and wash the separated product with water and dry it.

Optionally, the drying temperature is 40°C to 150°C.

Optionally, the drying time is 2h to 24h.

Optionally, the method includes:

Polymerize an alkaline solution containing silicon-based active materials and polyphenol monomers to obtain an alkaline solution containing polyphenol compounds;

Continue to add the flexible polymer containing polar groups into the alkaline solution, and then stir, separate, and dry to obtain the negative electrode material.

The present disclosure also provides a lithium ion battery, including the above negative electrode material or the negative electrode material obtained by the above preparation method.

The technical solution of the present disclosure has at least the following beneficial effects:

In the negative electrode material provided by the present disclosure, the surface of the silicon-based active material is coated with a composite coating layer. The composite coating layer is not easy to break and can maintain the structural stability of the silicon-based active material. Among them, connecting the silicon-based active material and the flexible polymer through polyphenols can enhance the interaction between the flexible polymer containing polar groups and the silicon-based active material, making the outer surface of the silicon-based active material uniform and Firmly adheres to flexible polymers containing rich polar groups, effectively improving the stability of the overall structure of the anode material. Since the polar groups of the flexible polymer are hydrophilic, the above-mentioned composite coating layer can improve the hydrophilicity of the negative electrode material, and can form a strong hydrogen bond with the water-based binder during the electrode production process, which has the effect of It is beneficial to improve the stability of the electrode structure, thereby obtaining significantly enhanced electrochemical performance.

The preparation method of the negative electrode material provided by the present disclosure involves coating raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers in a solution, thereby realizing the composite of silicon-based active materials. Coating, polyphenolic compounds formed by polymerization of polyphenol monomers can connect flexible polymers and silicon-based active materials, and can enhance the connection stability between flexible polymers and silicon-based active materials. The formed composite coating layer can make silicon-based The outer surface of the active material evenly and firmly adheres to the flexible polymer containing rich polar groups, which can improve the hydrophilicity of the material. During the electrode production process, it can form hydrogen bonds with the water-based binder and improve the stability of the electrode structure. Thus, significantly enhanced electrochemical performance is obtained; the preparation method is simple and the cost is low.

Description of drawings

Figure 1 is a schematic flow chart of a preparation method of anode material provided by an embodiment of the present disclosure;

Figure 2 is a schematic diagram of the cycle performance of the negative electrode material prepared in Example 1 of the present disclosure.

Detailed ways

The following are optional implementations of the embodiments of the present disclosure. It should be noted that those of ordinary skill in the art can make several improvements and modifications without departing from the principles of the embodiments of the present disclosure. These improvements and modifications are also considered to be within the protection scope of the embodiments of the present disclosure.

The present disclosure provides a negative electrode material. The negative electrode material includes a silicon-based active material and a composite coating layer located on the surface of the silicon-based active material. The composite coating layer includes a polyphenol compound and a flexible polymer containing polar groups.

In the above solution, the surface of the silicon-based active material is coated with a composite coating layer. The composite coating layer is not easy to break and can maintain the structural stability of the silicon-based active material. Among them, connecting the silicon-based active material and the flexible polymer through polyphenols can enhance the interaction between the flexible polymer containing polar groups and the silicon-based active material, making the outer surface of the silicon-based active material uniform and Firmly adheres to flexible polymers containing rich polar groups, effectively improving the stability of the overall structure of the anode material. Since the polar groups of the flexible polymer are hydrophilic, the above-mentioned composite coating layer can improve the hydrophilicity of the negative electrode material, and can form a strong hydrogen bond with the water-based binder during the electrode production process, which has the effect of It is beneficial to improve the stability of the electrode structure, thereby obtaining significantly enhanced electrochemical performance.

In some embodiments, the polyphenolic compound is connected to the silicon-based active material through π bonds, and the polyphenolic compound is graft-connected to the polar group of the flexible polymer through covalent bonds, which can further improve the stability of the structure.

It is understandable that if the silicon-based active material directly coats the flexible polymer to form a coating layer, the connection stability between the coating layer and the silicon-based active material will be poor, and it will not be able to effectively improve the stability of the overall structure.

In some embodiments, the silicon-based active material includes silicon-based active particles, and the silicon-based active particles include at least one of Si, SiO _x and silicon alloy, where 0<x<2. _In _some _embodiments _, _SiO _{_} _{_} _{_} _{_} _{_} _{_} _{_} The alloy can be silicon-lithium alloy, silicon-magnesium alloy, silicon-nickel alloy, etc. In some cases, the silicon-based active particles include silicon elemental particles and silicon alloys.

In some embodiments, the silicon-based active particles have a median particle size of 1 nm to 10 μm. The median diameter of the silicon-based active particles can be, for example, 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 1 μm, 2 μm, 5 μm or 10 μm, etc., of course it can also be It is other values within the above range and is not limited here. Through many experiments, it was found that nanoscale silicon-based active particles have high surface energy and strong particle structure, which can inhibit the volume expansion of silicon. Optionally, the median particle size of the silicon-based active particles is 1 nm to 500 nm, optionally 1 nm to 200 nm.

In some embodiments, the silicon-based active material includes silicon-based active particles and carbon materials.

In some embodiments, the carbon material forms a buffer skeleton inside the silicon-based active material, and the silicon-based active particles are distributed around the buffer skeleton. It can be understood that the silicon-based active particles are evenly dispersed in the carbon material, which can effectively prevent the silicon-based active particles from agglomerating during the charge and discharge process.

In some embodiments, the carbon material is located on the surface of the silicon-based active particles and forms a carbon layer.

In some embodiments, the thickness of the carbon layer is 1 nm to 1000 nm, for example, it can be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 400 nm, 500 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc. , no limitation is made here. If the carbon layer is too thick and the proportion of carbon is too high, it is not conducive to obtaining an anode material with a high specific capacity; if the carbon layer is too thin, it is not conducive to increasing the conductivity of the anode material and has a weak ability to inhibit the volume expansion of the material, resulting in poor long-term cycle performance. Difference. Optionally, the thickness of the carbon layer is 50nm~800nm; optionally, the thickness of the carbon layer is 100nm~500nm.

In some embodiments, the carbon material includes at least one of amorphous carbon, amorphous carbon material, and graphitized carbon material. Understandably, the carbon material can improve the electrical conductivity of the silicon-based active material. Optionally, the carbon material includes amorphous carbon.

In some embodiments, the mass ratio of the silicon-based active particles to the carbon material is (30-97): (3-70). In some embodiments, the mass ratio of silicon-based active particles to carbon materials is 30:3, 30:10, 40:20, 50:30, 30:50, 70:10, 70:70, 80:70, 90 :70, 97:3, etc., of course, it can also be other values within the above range, which are not limited here.

In some embodiments, the thickness of the composite coating layer is 1 nm to 1000 nm; for example, it can be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 400 nm, 500 nm, 700 nm, 800 nm, 900 nm, 1000nm, etc., are not limited here. Optionally, the thickness of the composite coating layer is 5 nm to 200 nm.

In some embodiments, polyphenolic compounds include compounds containing multiple phenolic hydroxyl groups. It should be noted that the plurality here means at least 2 or more phenolic hydroxyl groups.

In some embodiments, the polyphenolic compound includes at least one of polydopamine, polypyrogallol, polychlorogenic acid, polygallic acid, polycatechin, polylevodopa, and polytannic acid.

In some embodiments, the composite coating layer includes an inner region close to the silicon-based active material and an outer region far away from the silicon-based active material, wherein the content of polyphenolic compounds in the inner region is higher than that of the polyphenolic compounds in the outer region. content. Polyphenolic compounds can tightly bond to the carbon materials in silicon-based active materials through π bond stacking. In addition, polyphenolic compounds can also graft flexible polymers through covalent bonds. Therefore, the higher content of polyphenolic compounds in the inner region of the composite coating layer helps the composite coating layer adhere evenly and firmly to the surface of the silicon-based active material, while exposing the surface of the negative electrode material to a higher content of polyphenols rich in anode materials. Flexible polymers with sexual groups can improve the hydrophilicity of the negative electrode material, allowing the negative electrode material to form hydrogen bonds with the water-based binder during the electrode production process, improving the stability of the electrode structure, thereby obtaining significantly enhanced electrochemical performance. .

In some embodiments, the composite coating layer includes a first coating layer and a second coating layer that are sequentially stacked on the surface of the silicon-based active material. The first coating layer is close to the silicon-based active material, and the first coating layer includes Polyphenolic compound, the second coating layer includes a flexible polymer containing polar groups. The polyphenol compound of the first coating layer can tightly bond to the carbon material in the silicon-based active material through π bond stacking, ensuring the uniformity and firmness of the coating. In addition, polyphenols can also graft flexible polymers through covalent bonds, so that the second coating layer of flexible polymers containing rich polar groups can be evenly and firmly wrapped on the outermost surface of the anode material, thereby significantly improving The hydrophilicity of the negative electrode material allows the negative electrode material to form hydrogen bonds with the water-based binder during the electrode production process, improving the stability of the electrode structure, thereby obtaining significantly enhanced electrochemical performance.

In some embodiments, polyphenolic compounds include oligomers and/or polymers polymerized from polyphenol monomers.

In some embodiments, the polyphenol monomer includes at least one of flavonoids, dopamine hydrochloride, pyrogallol, chlorogenic acid, gallic acid, ellagic acid, catechin, levodopa, and tannins . It can be understood that polyphenol monomers refer to compounds containing multiple phenolic hydroxyl groups. Polyphenol compounds formed by the polymerization of polyphenol monomers can be tightly bonded to the carbon materials in silicon-based active materials through π bond stacking. In addition, polyphenols can also be grafted onto flexible polymers through covalent bonds, thereby This allows the surface of the silicon-based active material to adhere evenly and firmly to the flexible polymer containing rich polar groups, effectively improving the structural stability of the composite coating layer and improving the hydrophilicity of the material.

In some embodiments, the polyphenol monomers include flavonoids including at least one of flavones, isoflavones, flavanones, flavanols, flavanonols, anthocyanins, and chalcones.

In some embodiments, flexible polymers include polyolefins and derivatives thereof, polyvinyl alcohol and derivatives thereof, polyacrylic acid and derivatives thereof, polyamides and derivatives thereof, carboxymethyl cellulose and derivatives thereof, seaweed At least one of acids and their derivatives.

In some embodiments, the flexible polymer includes a main chain and a side chain, wherein the main chain has internally rotatable single bonds such as C-C, C-N, C-O, Si-O, etc., and the side chain has a polar group. Since the composite coating layer on the surface of the negative electrode material particles is rich in polar groups, the coating layer can show good flexibility, effectively inhibit the volume expansion of the silicon-based active material, and also significantly improve the hydrophilicity of the material. , and the rich polar groups can form strong hydrogen bonds with the water-based binder, enhance the structural stability of the pole piece, and further improve the electrochemical performance of the battery.

In some embodiments, the polar group includes at least one of amino, carboxyl, hydroxyl, and ethoxy.

In some embodiments, polar groups include amino and ethoxy. The amino group plays a role in improving the hydrophilicity of the material, which is conducive to the formation of hydrogen bonds with the water-based binder and enhances the stability of the electrode structure. The ethoxy group has good ionic conductivity and electrophilicity, which is conducive to promoting the rapid penetration of electrolyte, enhancing the charge transfer efficiency of the active material interface, effectively improving the polarization phenomenon of negative electrode materials under high current, and significantly improving electrochemical performance.

In some embodiments, the contact angle between the negative electrode material and water is θ, θ≤60°, for example, it can be 60°, 55°, 50°, 45°, 40°, 35°, 30°, 25°, 20° etc., no limitation is made here. This is because the composite coating layer adhered to the surface of the silicon-based active material particles, especially the large number of polar groups contained in the flexible polymer, makes the outermost surface of the silicon-based active material have superior hydrophilicity.

In some embodiments, the contact angle between the negative electrode material and the electrolyte is eta, eta≤90°, for example, it can be 90°, 80°, 70°, 65°, 50°, 45°, 40°, 35°, 30° °, 25°, 20°, etc. are not limited here. The electrolyte solution includes ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and lithium hexafluorophosphate, and the concentration of lithium hexafluorophosphate in the electrolyte solution is 1 mol/L. The composite coating layer adhered to the surface of the silicon-based active material particles, especially the flexible polymer containing ethoxy groups, makes the outermost surface of the silicon-based active material highly electrophilic, which is conducive to promoting the rapid penetration of the electrolyte. , Enhance the charge transfer efficiency at the active material interface. Preferably, eta≤80°.

In some embodiments, the contact angle between the negative electrode material and water is θ, and the contact angle between the negative electrode material and the electrolyte is η, and satisfies (η+θ)≤120°, for example, it can be 120°, 110°, 100°, 85°, 70°, 65°, 50°, 45°, 40°, 30°, 20°, etc. are not limited here. The composite coating layer adhered to the surface of the silicon-based active material particles, especially the flexible polymer containing both amino and ethoxy groups, makes the outermost surface of the silicon-based active material have superior hydrophilicity and electrophilicity at the same time. , not only forms hydrogen bonds with the aqueous binder to enhance the stability of the electrode structure, but also improves the interfacial charge transfer efficiency of the negative electrode material and significantly improves the electrochemical performance.

In some embodiments, in the Raman spectrum, the negative electrode material has a carbon characteristic peak G and a silicon characteristic peak A, and the ratio of the peak intensity I _A of the silicon characteristic peak A to the peak intensity I _G of the carbon characteristic peak G I _A / I _G is 0.2 to 4; for example, it can be 0.2, 0.5, 0.8, 1.0, 1.5, 1.8, 2.0, 2.2, 2.4, 3, 3.5, 3.8 or 4, etc., and is not limited here.

In some embodiments, in the Raman spectrum, the variance of the I _A / _IG values of n negative electrode materials randomly collected is <3, where n≥10. Understandably, the surface of the silicon-based active material is evenly covered with a composite coating layer, which weakens the characteristic peak signals of silicon and carbon in the negative electrode material and narrows the difference between the two.

In some embodiments, the composite coating layer includes amino groups. In the X-ray photoelectron spectrum, the negative electrode material has silicon characteristic peaks and nitrogen characteristic peaks. The peak area of the silicon characteristic peak is S1 and the peak area of the nitrogen characteristic peak is S2, 1<S1/S2<10. In some embodiments, the characteristic peak of silicon is located in the range of 97eV-107eV, and the characteristic peak of nitrogen is located in the range of 395eV-405eV. Understandably, S1/S2 represents the signal ratio between the core silicon-based active material and the composite coating layer, and also reflects the thickness of the composite coating layer. The smaller the value of S1/S2 is, the thicker the composite coating layer is. In this disclosure, the negative electrode material satisfies 1<S1/S2<10, indicating that the surface of the silicon-based active material has a composite coating layer of appropriate thickness, which can improve the structural stability and material hydrophilicity on the premise of satisfying charge transport.

In some embodiments, the composite coating layer includes amino groups. In the X-ray photoelectron spectrum, the negative electrode material has C-O bond characteristic peaks and N-C=O bond characteristic peaks. The peak area of the C-O bond characteristic peaks is S3, N-C= The peak area of the O bond characteristic peak is S4, and S3/S4<10.

In the above embodiment, S3 mainly represents the XPS characteristic peaks of the polyphenolic compounds in the composite coating layer, and S4 represents the XPS characteristic peaks of the flexible polymer in the composite coating layer. Since polyphenols are covered by flexible polymers, the XPS characteristic peaks of polyphenols are weakened. When S3/S4 <10, it means that the polyphenolic compounds are uniformly and firmly coating the silicon-based active material, and the flexible polymer has fully grafted and coated the polyphenolic compounds, thus effectively improving the structural stability of the coating layer. And improve the hydrophilicity of the material.

In some embodiments, after adding 20 g of negative electrode material to 300 ml of water, stirring and washing, the carbon element change amount ΔC of the composite coating layer of the negative electrode material is ≤ 2%. It can be seen from this that the composite coating layer on the surface of the negative electrode material adheres firmly to the silicon-based active material. The smaller the change in the carbon element of the composite coating layer is, the better the connection between the composite coating layer and the silicon-based active material is.

In some embodiments, ΔC=C1-C2, C1 is the mass content of carbon element in the negative electrode material, and C2 is the mass content of carbon element in the negative electrode material after washing with water. The water washing process can be as follows: add 20g of negative electrode material to 300ml of water and stir for 30 minutes, then suction filtrate to obtain the filtered material, and finally dry the filtered material in an oven at 80°C for 12 hours to obtain the washed negative electrode material.

In some embodiments, the mass content of carbon element in the negative electrode material is 1% to 50%; for example, it can be 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt% , 30wt%, 40wt% or 50wt%, etc. Of course, it can also be other values within the above range, which is not limited here.

In some embodiments, the average particle size of the negative electrode material is 0.2 μm ~ 50.0 μm, for example, it can be 0.2 μm, 0.5 μm, 1.0 μm, 1.2 μm, 1.5 μm, 2 μm, 2.5 μm, 3.0 μm, 5 μm, 8.0 μm, 10.0μm, 15.0μm, 18.0μm, 20.0μm, 30.0μm, 40.0μm or 50.0μm, etc. are not limited here.

In some embodiments, the specific surface area of the negative electrode material is 0.1m ² /g ~ 10m ² /g; the specific surface area of the negative electrode material can be, for example, 0.1m ² /g, 0.2m ^{2 /g, 0.5m 2} ^/ g, 0.6 m ² /g, 1.0m ² /g, 1.5m ² /g, 2.0m ² /g, 2.5m ² /g, 3.0m 2 /g, ^3.6m 2 /g, 4.0m ² /g ^, 4.6m ² /g, 5m ^{2 /} g, 5.5m ² /g, 5.8m 2 / ^g, 6.0m ² /g, ^6.8m 2 /g, 7.0m 2 /g, 7.4m ² /g, 8.0m ² ^/ g, 8.5m ² /g, 9.8m ² /g or 10m ² /g, but it is not limited to the listed values, and other unlisted values within this value range are also applicable.

In some embodiments, the tap density of the negative electrode material is 0.5g/cm ³ to 1.5g/cm ³ ; for example, it can be 0.5g/cm ³ , 0.6g/cm ³ , 0.8g/cm ³ , or 1.0g/cm ³ , 1.2g/cm ³ , 1.4g/cm ³ or 1.5g/cm ³ , etc. Of course, it can also be other values within the above range, which are not limited here. It can be understood that controlling the tap density of the negative electrode material within the above range is beneficial to improving the energy density of the material.

The embodiment of the present disclosure provides a preparation method of anode material, as shown in Figure 1, the method includes:

In step S10, raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in a solution to obtain a negative electrode material.

In the above solution, raw materials containing silicon-based active materials, polyphenol monomers, and flexible polymers containing polar groups are coated in a solution to achieve composite coating of silicon-based active materials. Polyphenols The polyphenolic compounds formed by polymerization of monomers can connect flexible polymers and silicon-based active materials, and can enhance the connection stability between flexible polymers and silicon-based active materials. The composite coating layer formed can make the outer surface of silicon-based active materials Evenly and firmly adhere to flexible polymers containing rich polar groups, which can improve the hydrophilicity of the material. During the electrode production process, it can form hydrogen bonds with the water-based binder, improve the stability of the electrode structure, and obtain significantly enhanced performance. Electrochemical performance; and the preparation method is simple and low cost.

The above solution is explained below in conjunction with optional implementations:

Before step S10, the method further includes:

Prepare a mixed coating solution containing polyphenol monomer, pH regulator, flexible polymer containing polar groups and solvent.

In some embodiments, the polyphenol monomer includes at least one of flavonoids, dopamine hydrochloride, pyrogallol, chlorogenic acid, gallic acid, ellagic acid, catechin, levodopa, and tannins .

In some embodiments, the solvent includes at least one of water, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, and dimethyl sulfoxide.

In some embodiments, the polyphenol monomer includes dopamine hydrochloride. It is understandable that dopamine hydrochloride contains a large number of phenolic hydroxyl groups in the molecule, and oxidative self-polymerization will occur under weak alkali conditions to generate oligomers and/or polymers with lower molecular weights, and the oligomers and/or polymers will Cross-linking reaction produces polyphenolic compounds (polydopamine) with higher molecular weight. Polydopamine has strong adhesion, can connect silicon-based active materials and flexible polymers, and improve the connection stability between the composite coating layer and silicon-based active materials.

In some embodiments, flexible polymers include natural flexible polymers and/or synthetic flexible polymers.

In some embodiments, flexible polymers include polyolefins and derivatives thereof, polyvinyl alcohol and derivatives thereof, polyacrylic acid and derivatives thereof, polyamides and derivatives thereof, carboxymethylcellulose and derivatives thereof, or Any one or a combination of at least two of alginic acid and its derivatives.

"Natural flexible polymer and/or synthetic flexible polymer" in this disclosure means: it can be a natural flexible polymer or a synthetic flexible polymer, or it can be a natural flexible polymer and a synthetic flexible polymer. mixture.

Typical but non-limiting examples of combinations of flexible polymers are: the combination of polyolefin and polyvinyl alcohol, the combination of polyvinyl alcohol and carboxymethyl cellulose, the combination of carboxymethyl cellulose and alginic acid, the combination of polyamide and carboxymethyl Combinations of cellulose derivatives, combinations of polyolefins, polyolefin derivatives and polyacrylic acid, combinations of polyvinyl alcohol, polyamide derivatives and alginic acid, polyolefins, polyvinyl alcohol, polyacrylic acid derivatives, Combinations of polyamide and alginic acid, etc.

In some embodiments, the flexible polymer includes polyacrylamide.

In some embodiments, the flexible polymer contains polar groups, and the polar groups include at least one of ethoxy, carboxyl, hydroxyl and amino.

In some embodiments, the polyphenol monomer self-polymerizes to form oligomers and/or multimers, and the oligomers and/or multimers cross-link and polymerize with the flexible polymer to obtain a composite polymer, thereby branching directly coated onto the surface of the silicon-based active material.

In some embodiments, the pH value of the mixed coating solution is 8.0-9.0.

In some embodiments, the pH adjusting agent includes Tris-HCl buffer, sodium barbiturate-HCl buffer, glycine-sodium hydroxide buffer, borax-sodium hydroxide buffer, sodium carbonate-carbonate At least one of sodium hydrogen buffer, ammonia, sodium hydroxide solution, potassium hydroxide solution and lithium hydroxide solution.

In some embodiments, the mass ratio of polyphenol monomer, flexible polymer and silicon-based active material is (0.1~15): (0.1~15):100, for example, it can be 0.1:0.1:100, 0.5:0.5: 100, 1:1:100, 5:5:100, 5:10:100, 10:10:100, 15:5:100 or 15:15:100, etc. are not limited here.

In some embodiments, preparing the mixed coating solution is performed under stirring conditions.

In some embodiments, the stirring speed of the mixed coating liquid is 100-1000r/min; for example, it can be 100r/min, 200r/min, 300r/min, 400r/min, 500r/min, 600r/min, 700r/min , 800r/min, 900r/min or 1000r/min, etc., there is no limit here.

In some embodiments, the stirring time of the mixed coating liquid is 0.5h to 20h, for example, it can be 0.5h, 1h, 2h, 5h, 8h, 10h, 12h, 15h, 18h or 20h, etc., which is not limited here.

In some embodiments, the stirring temperature of the mixed coating liquid is 10°C to 100°C, for example, it can be 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 100°C, etc., where No restrictions.

In some embodiments, step S10 is also performed under stirring conditions.

In some embodiments, the carbon material is located on the surface of the silicon-based active particles to form a carbon layer.

In some embodiments, the carbon material includes at least one of amorphous carbon, crystalline carbon, hard carbon, soft carbon, and mesocarbon microspheres. Understandably, the carbon material can improve the electrical conductivity of the silicon-based active material. Optionally, the carbon material includes amorphous carbon.

In some embodiments, the mass ratio of the silicon-based active particles to the carbon material is (30-70): (10-70). In some embodiments, the mass ratio of silicon-based active particles to carbon materials is 30:10, 40:20, 50:30, 30:50, 70:10, 70:70, etc., and of course it can also be within the above range. Other values of are not limited here.

In some embodiments, the coating process is performed under agitation.

In some embodiments, stirring includes at least one of mechanical stirring and ultrasonic stirring.

In some embodiments, stirring is performed at 10°C to 100°C, for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C etc. are not limited here.

In some embodiments, after step S10, the method further includes: separating the solution to obtain an isolated product; wherein the separation includes at least one of normal pressure filtration, reduced pressure filtration and centrifugation;

In some embodiments, after step S10, the method further includes separating the solution and subjecting the separated product to water washing.

During the water washing process, the mass ratio of the separated product to water is (1~5):100, thereby washing to remove impurities in the separated product, such as trishydroxymethylaminomethane, hydrochloric acid, residual flexible polymers, and polyphenol monomers. wait.

In some embodiments, after step S10, the method further includes separating the solution, and washing the separated product with water and drying it.

In some embodiments, the drying temperature ranges from 40°C to 150°C, such as 40°C, 50°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C. ℃, etc., are not limited here. Optionally, the drying temperature is 80°C to 100°C. If the drying temperature is too low, the drying efficiency will be low; if the drying temperature is too high, the polymer will easily undergo pyrolysis and the polar groups on the surface of the flexible polymer will be lost.

In this solution, after the composite coating layer is formed on the surface of the silicon-based active material, it only needs to be dried at low temperature. The polar groups on the flexible polymer in the composite coating layer will not cause a large number of polar groups due to overheating heat treatment. The loss of polar groups, low-temperature drying retains the polar groups on the flexible polymer to the greatest extent. The rich polar groups can improve the hydrophilicity of the negative electrode material, and can form hydrogen with the water-based binder during the electrode production process. bonds, improving the stability of the electrode structure, thereby obtaining significantly enhanced electrochemical performance.

In some embodiments, the drying time is 2h to 24h, for example, it can be 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h, etc., which is not limited here.

In other embodiments, the preparation method includes:

Step S11, perform a polymerization reaction on an alkaline solution containing silicon-based active materials and polyphenol monomers to obtain an alkaline solution containing polyphenol compounds;

Step S12: Continue to add a flexible polymer containing polar groups into the alkaline solution, and then stir, separate, and dry to obtain a negative electrode material.

In the above solution, polyphenols can be formed on the surface of the silicon-based active material first, and then the flexible polymer can be added. By stirring, the polyphenols and the flexible polymer can be graft-connected through covalent bonds. The surface of the active material forms a composite coating layer with strong structural stability, the preparation method is simple and controllable, and the preparation cost is low. In the prepared negative electrode material, the surface of the silicon-based active material is coated with a composite coating layer. The composite coating layer is not easy to break. The composite coating layer can make the outer surface of the silicon-based active material adhere evenly and firmly with rich polar groups. The flexible polymer effectively improves the structural stability of the composite coating layer and improves the hydrophilicity of the material, which is conducive to the formation of hydrogen bonds with the water-based binder and improves the structural stability of the electrode, thereby obtaining significantly enhanced electrochemical performance.

The present disclosure also provides a lithium ion battery, including a negative electrode material or a negative electrode material obtained by a preparation method.

Example

The embodiments of the present disclosure will be further described below using multiple embodiments. Among them, the embodiments of the present disclosure are not limited to the following optional embodiments. Changes can be implemented appropriately within the scope of protection.

Example 1

The preparation method of the negative electrode material in this embodiment includes the following steps:

(1) Prepare 300 ml of 0.1 mol/L tris-hydroxymethylaminomethane-hydrochloric acid buffer (pH=8.5), add 20 g of SiO/C material with a core of SiO and a shell of carbon, and stir for 30 minutes.

(2) Add 2g of dopamine hydrochloride and stir for 10 hours while ensuring that the liquid level is exposed to the air. Then add 2g of polyacrylamide and stir for 10 hours while ensuring that the liquid level is exposed to the air.

(3) Collect the product by suction filtration, and then add 2L of water to rinse the material repeatedly to remove residual impurities to obtain the isolated product.

(4) Dry the separated product at 80°C for 12 hours, then crush and sieve to obtain the negative electrode material.

The negative electrode material prepared in this embodiment includes a silicon-based active material SiO/C and a composite coating layer. The composite coating layer includes a polyphenol compound located on the surface of the silicon-based active material and a flexible polymer containing polar groups, wherein, The polyphenolic compound is polydopamine, the flexible polymer is polyacrylamide, and the polar group is amino. In the composite coating layer, the content of polyphenolic compounds in the inner region close to the silicon-based active material is higher than the content of polyphenol compounds in the outer region far away from the silicon-based active material. Figure 2 is a schematic diagram of the cycle performance of the negative electrode material prepared in Example 1 of the present disclosure.

The thickness of the composite coating layer is 10nm, the specific surface area of the negative electrode material is 2.32m ² /g, the mass content of carbon element in the negative electrode material is 5.53%, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 26°, and the contact angle eta between the negative electrode material and the electrolyte is 67°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 2.9%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 2.7. The characteristic peak of C-O bond in the negative electrode material is 2.9%. The N-C=O bond characteristic peak area ratio S3/S4 is 1.6.

Example 2

(1) Prepare 300 ml of 0.1 mol/L tris-hydroxymethylaminomethane-hydrochloric acid buffer (pH=10.5), add 20 g of SiO/C material with a core of SiO and a shell of carbon, and stir for 30 minutes.

(3) Collect the product by suction filtration, and then add 2L of water to rinse the material repeatedly to remove residual impurities to obtain the precursor.

(4) Dry the precursor at 80°C for 12 hours, then crush and sieve to obtain the negative electrode material.

The negative electrode material prepared in this embodiment includes a silicon-based active material SiO/C and a composite coating layer. The composite coating layer includes a polyphenol compound located on the surface of the silicon-based active material and a flexible polymer containing polar groups, wherein, The polyphenolic compound is polydopamine, the flexible polymer is polyacrylamide, and the polar group is amino.

The thickness of the composite coating layer is 18nm, the mass content of carbon element in the negative electrode material is 5.62%, the specific surface area of the negative electrode material is 2.35m ² /g, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 23°, and the contact angle eta between the negative electrode material and the electrolyte is 62°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 3.7%. The area ratio S1/S2 of the Si element characteristic peak and the N element characteristic peak in the negative electrode material is 1.8. The C-O bond characteristic peak in the negative electrode material is 1.8. The N-C=O bond characteristic peak area ratio S3/S4 is 1.3.

Example 3

(2) Add 0.2g dopamine hydrochloride and stir for 10 hours while ensuring that the liquid level is exposed to the air. Then add 0.2g polyacrylamide and stir for 10 hours while ensuring that the liquid level is exposed to the air.

The thickness of the composite coating layer is 5nm, the mass content of the carbon element of the negative electrode material is 5.07%, the specific surface area of the negative electrode material is 2.11m ² /g, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 42°, and the contact angle eta between the negative electrode material and the electrolyte is 78°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 0.8%. The area ratio S1/S2 of the Si element characteristic peak and the N element characteristic peak in the negative electrode material is 6.1. The C-O bond characteristic peak in the negative electrode material is 6.1. The N-C=O bond characteristic peak area ratio S3/S4 is 5.6.

Example 4

(2) Add 2g of dopamine hydrochloride and stir for 0.5 hours while ensuring that the liquid level is exposed to the air. Then add 2g of polyacrylamide and stir for 0.5 hours while ensuring that the liquid level is exposed to the air.

The thickness of the composite coating layer is 8nm, the specific surface area of the negative electrode material is 2.21m ² /g, the mass content of carbon element in the negative electrode material is 5.26%, the tap density of the negative electrode material is 1.2g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 32°, and the contact angle eta between the negative electrode material and the electrolyte is 70°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 1.7%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 3.4. The characteristic peak of C-O bond in the negative electrode material is 3.4. The N-C=O bond characteristic peak area ratio S3/S4 is 2.5.

Example 5

(2) Add 2g of levodopa and stir for 10 hours while ensuring that the liquid level is exposed to the air. Then add 2g of polyacrylamide and stir for 10 hours while ensuring that the liquid level is exposed to the air.

The negative electrode material prepared in this embodiment includes a silicon-based active material SiO/C and a composite coating layer. The composite coating layer includes a polyphenol compound located on the surface of the silicon-based active material and a flexible polymer containing polar groups, wherein, The polyphenolic compound is poly-levodopa, the flexible polymer is polyacrylamide, and the polar group is amino.

The thickness of the composite coating layer is 6nm, the specific surface area of the negative electrode material is 2.13m ² /g, the mass content of carbon element in the negative electrode material is 4.93%, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 34°, and the contact angle eta between the negative electrode material and the electrolyte is 67°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 1.2%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 5.6. The characteristic peak of C-O bond in the negative electrode material is 5.6. The N-C=O bond characteristic peak area ratio S3/S4 is 4.2.

Example 6

(2) Add 2g of tannic acid and stir for 10 hours while ensuring that the liquid level is exposed to the air. Then add 2g of polyacrylamide and stir for 10 hours while ensuring that the liquid level is exposed to the air.

The negative electrode material prepared in this embodiment includes a silicon-based active material SiO/C and a composite coating layer. The composite coating layer includes a polyphenol compound located on the surface of the silicon-based active material and a flexible polymer containing polar groups. The flexible polymer The material is cross-linked with a polyphenol compound to form a network structure, wherein the polyphenol compound is a tannic acid polymer, the flexible polymer is polyacrylamide, and the polar group is an amino group.

The thickness of the composite coating layer is 8nm, the specific surface area of the negative electrode material is 2.11m ² /g, the mass content of carbon element in the negative electrode material is 5.24%, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 30°, and the contact angle eta between the negative electrode material and the electrolyte is 72°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 2.3%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 3.3. The characteristic peak of C-O bond in the negative electrode material is 3.3. The N-C=O bond characteristic peak area ratio S3/S4 is 2.1.

Example 7

(2) Add 2g of dopamine hydrochloride and stir for 10 hours while ensuring that the liquid level is exposed to the air. Then add 2g of chitosan and stir for 10 hours while ensuring that the liquid level is exposed to the air.

The negative electrode material prepared in this embodiment includes a silicon-based active material SiO/C and a composite coating layer. The composite coating layer includes a polyphenol compound located on the surface of the silicon-based active material and a flexible polymer containing polar groups, wherein, The polyphenolic compound is polydopamine, the flexible polymer is chitosan, and the polar groups are amino groups and hydroxyl groups.

The thickness of the composite coating layer is 6nm, the specific surface area of the negative electrode material is 2.14m ² /g, the mass content of carbon element in the negative electrode material is 4.97%, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 37°, and the contact angle eta between the negative electrode material and the electrolyte is 76°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 0.9%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 6.4. The characteristic peak of C-O bond in the negative electrode material is 6.4. The N-C=O bond characteristic peak area ratio S3/S4 is 3.1.

Example 8

(2) Add 2g of dopamine hydrochloride and stir for 10 hours while ensuring that the liquid level is exposed to the air. Then add 2g of polyethyleneimine and stir for 10 hours while ensuring that the liquid level is exposed to the air.

The negative electrode material prepared in this embodiment includes a silicon-based active material SiO/C and a composite coating layer. The composite coating layer includes a polyphenol compound located on the surface of the silicon-based active material and a flexible polymer containing polar groups, wherein, The polyphenolic compound is polydopamine, the flexible polymer is polyethylenimine, and the polar group is amino.

The thickness of the composite coating layer is 9nm, the specific surface area of the negative electrode material is 2.21m ² /g, the mass content of carbon element in the negative electrode material is 5.38%, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 24°, and the contact angle eta between the negative electrode material and the electrolyte is 65°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 1.6%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 2.5. The characteristic peak of C-O bond in the negative electrode material is equal to The N-C=O bond characteristic peak area ratio S3/S4 is 2.7.

Example 9

(1) Prepare 300 ml of 0.1 mol/L tris-hydroxymethylaminomethane-hydrochloric acid buffer (pH=8.5), add 20 g of Si/C composite material with nano-silica evenly dispersed in the carbon buffer matrix, and stir for 30 minutes.

The negative electrode material prepared in this embodiment includes a silicon-based active material Si/C and a composite coating layer. The composite coating layer includes a polyphenol compound located on the surface of the silicon-based active material and a flexible polymer containing polar groups, wherein, The polyphenolic compound is polydopamine, the flexible polymer is polyacrylamide, and the polar group is amino.

The thickness of the composite coating layer is 14nm, the specific surface area of the negative electrode material is 4.37m ² /g, the mass content of carbon element in the negative electrode material is 40.72%, the tap density of the negative electrode material is 0.6g/cm ³ , and the average particle size of the negative electrode material The diameter is 6.4 μm, the contact angle θ between the negative electrode material and water is 27°, and the contact angle eta between the negative electrode material and the electrolyte is 68°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 2.6%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 2.3. The characteristic peak of C-O bond in the negative electrode material is 2.6%. The N-C=O bond characteristic peak area ratio S3/S4 is 1.7.

Example 10

(1) Prepare 300 ml of 0.1 mol/L tris-hydroxymethylaminomethane-hydrochloric acid buffer (pH=8.5), add 2g of dopamine hydrochloride and 2g of polyacrylamide, and stir for 0.5 hours while ensuring that the liquid surface is exposed to the air;

(2) Add 20g of SiO/C material with SiO as the core and carbon layer as the outer shell, and stir for 10 hours while ensuring that the liquid surface is exposed to the air;

The thickness of the composite coating layer is 11nm, the specific surface area of the negative electrode material is 2.37m ² /g, the mass content of carbon element in the negative electrode material is 5.45%, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 29°, and the contact angle eta between the negative electrode material and the electrolyte is 71°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 2.4%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 2.9. The characteristic peak of C-O bond in the negative electrode material is 2.9. The N-C=O bond characteristic peak area ratio S3/S4 is 2.1.

Example 11

(2) Add 2g of dopamine hydrochloride, stir for 10 hours while ensuring that the liquid level is exposed to the air, collect the product by suction filtration, and add 2L of water to repeatedly rinse the material to remove residual impurities. The separated product is dried at 80°C. The precursor was obtained in 12 hours.

(3) Prepare 300 ml of 0.1 mol/L tris-hydroxymethylaminomethane-hydrochloric acid buffer (pH=8.5), add 2 g of polyacrylamide and 20 g of the precursor prepared in step (2), and ensure that the liquid surface is exposed to the air Stir for 10 hours.

(4) Collect the product by suction filtration, and add 2L of water to repeatedly rinse the material to remove residual impurities. The separated product is dried at 80°C for 12 hours, and then crushed and screened to obtain the negative electrode material.

The negative electrode material prepared in this embodiment includes a silicon-based active material SiO/C and a composite coating layer. The composite coating layer includes a first coating layer and a second coating layer sequentially laminated on the surface of the silicon-based active material. The coating layer includes a polyphenol compound, and the second coating layer includes a flexible polymer containing a polar group, wherein the polyphenol compound is polydopamine, the flexible polymer is polyacrylamide, and the polar group The group is amino.

The thickness of the composite coating layer is 21nm, the specific surface area of the negative electrode material is 2.28m ² /g, the mass content of carbon element in the negative electrode material is 5.61%, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 25°, and the contact angle eta between the negative electrode material and the electrolyte is 66°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 3.2%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 2.1. The characteristic peak of C-O bond in the negative electrode material is 2.1. The N-C=O bond characteristic peak area ratio S3/S4 is 1.4.

Example 12

(2) Add 2g of dopamine hydrochloride and stir for 10 hours while ensuring that the liquid level is exposed to the air. Add 2g of poly(acrylamide-ethylene glycol diacrylate) and stir for 10 hours while ensuring that the liquid level is exposed to the air. Hour.

The negative electrode material prepared in this embodiment includes a silicon-based active material SiO/C and a composite coating layer. The composite coating layer includes a polyphenol compound located on the surface of the silicon-based active material and a flexible polymer containing polar groups, wherein, The polyphenolic compound is polydopamine, the flexible polymer is polyacrylamide and polyethylene glycol diacrylate, and the polar groups are amino and ethoxy groups.

The thickness of the composite coating layer is 7nm, the specific surface area of the negative electrode material is 2.26m ² /g, the mass content of carbon element in the negative electrode material is 5.23%, the tap density of the negative electrode material is 1.1g/cm ³ , and the average of the negative electrode material The particle size is 5.1 μm, the contact angle θ between the negative electrode material and water is 34°, and the contact angle eta between the negative electrode material and the electrolyte is 54°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 1.7%. The area ratio S1/S2 of the Si element characteristic peak and the N element characteristic peak in the negative electrode material is 3.1. The C-O bond characteristic peak in the negative electrode material is 3.1. The N-C=O bond characteristic peak area ratio S3/S4 is 2.1.

Example 13

(2) Add 0.05g dopamine hydrochloride, stir for 10 minutes while ensuring that the liquid level is exposed to the air, add 3g polyacrylamide, and stir for 5 hours at 80°C to remove most of the solvent while ensuring that the liquid level is exposed to the air. .

The thickness of the composite coating layer is 2nm, the specific surface area of the negative electrode material is 1.34m ² /g, the mass content of carbon element in the negative electrode material is 9.64%, the tap density of the negative electrode material is 0.8g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.2 μm, the contact angle θ between the negative electrode material and water is 54°, and the contact angle eta between the negative electrode material and the electrolyte is 79°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 3.2%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 16.7. The characteristic peak of C-O bond in the negative electrode material is 16.7. The N-C=O bond characteristic peak area ratio S3/S4 is 0.9, and the area ratio S3/S4 of the C-O bond characteristic peak and the N-C=O bond characteristic peak in the negative electrode material is 1.8.

Example 14

(2) Add 2g of dopamine hydrochloride and stir for 10 hours while ensuring that the liquid level is exposed to the air. Add 0.1g of polyacrylamide and stir for 5 hours at 80°C while ensuring that the liquid level is exposed to the air to remove most of the dopamine hydrochloride. Solvent.

The thickness of the composite coating layer is 25nm, the specific surface area of the negative electrode material is 1.46m ² /g, the mass content of carbon element in the negative electrode material is 5.86%, the tap density of the negative electrode material is 1.0g/cm ³ , and the average of the negative electrode material The particle size is 5.2 μm, the contact angle θ between the negative electrode material and water is 23°, and the contact angle eta between the negative electrode material and the electrolyte is 64°.

The negative electrode material was tested by XPS. The mass content of nitrogen element in the negative electrode material is 3.5%. The area ratio S1/S2 of the characteristic peak of Si element and the characteristic peak of N element in the negative electrode material is 3.2. The characteristic peak of C-O bond in the negative electrode material is 3.5%. The N-C=O bond characteristic peak area ratio S3/S4 is 12.3.

Example 15

(2) Add 2g of dopamine hydrochloride and stir for 10 hours while ensuring that the liquid level is exposed to the air. Then add 2g of polyethylene glycol diacrylate and stir for 10 hours while ensuring that the liquid level is exposed to the air.

The negative electrode material prepared in this embodiment includes a silicon-based active material SiO/C and a composite coating layer. The composite coating layer includes a polyphenol compound located on the surface of the silicon-based active material and a flexible polymer containing polar groups, wherein, The polyphenolic compound is polydopamine, the flexible polymer is polyethylene glycol diacrylate, and the polar group is ethoxy group.

The thickness of the composite coating layer is 3nm, the specific surface area of the negative electrode material is 2.13m ² /g, the mass content of carbon element in the negative electrode material is 4.52%, the tap density of the negative electrode material is 1.1g/cm ³ , and the average particle size of the negative electrode material The diameter is 5.1 μm, the contact angle θ between the negative electrode material and water is 67°, and the contact angle eta between the negative electrode material and the electrolyte is 42°.

The negative electrode material was tested by XPS and found that the mass content of nitrogen in the negative electrode material was 1.6%, and the area ratio S1/S2 of the characteristic peaks of the Si element and the characteristic peak of the N element in the negative electrode material was 13.9.

Comparative example 1

Comparative Example 1 is a SiO/C material with a core of SiO and a shell of carbon used in Example 1, without polymer coating.

The specific surface area of the negative electrode material is 2.10m ² /g, the mass content of carbon element in the negative electrode material is 4.29%, the tap density of the negative electrode material is 1.1g/cm ³ , the average particle size of the negative electrode material is 5.1 μm, and the negative electrode material is The contact angle θ of water is 79°, and the contact angle eta between the negative electrode material and the electrolyte is 86°.

Comparative example 2

Comparative Example 2 is a Si/C composite material in which the nano-silicon used in Example 9 is evenly dispersed in a carbon buffer matrix without polymer coating.

The specific surface area of the negative electrode material is 4.81m ² /g, the mass content of carbon element in the negative electrode material is 39.12%, the tap density of the negative electrode material is 0.6g/cm ³ , the average particle size of the negative electrode material is 6.4 μm, and the negative electrode material is The contact angle θ of water is 77°, and the contact angle eta between the negative electrode material and the electrolyte is 85°.

Comparative example 3

The preparation method of the negative electrode material in this comparative example includes the following steps:

(1) Add 20g of SiO/C material with SiO as the core and carbon layer as the outer shell into 300 ml of water and stir for 30 minutes.

(2) Add 2g polyacrylamide and continue stirring for 10 hours.

(3) Collect the product by suction filtration, and add 2L of water to rinse the material.

The negative electrode material prepared in this comparative example includes a silicon-based active material SiO/C and a polyacrylamide coating layer. The specific surface area of the negative electrode material is 2.19m ² /g. The mass content of carbon element in the negative electrode material is 4.56%. The tap density is 1.1g/cm ³ , the average particle size of the negative electrode material is 5.1 μm, the contact angle θ between the negative electrode material and water is 75°, and the contact angle eta between the negative electrode material and the electrolyte is 83°.

The negative electrode material was tested by XPS and found that the mass content of nitrogen in the negative electrode material was 0.3%, and the area ratio S1/S2 of the characteristic peaks of the Si element and the characteristic peak of the N element in the negative electrode material was 34.6.

Comparative example 4

(2) Add 2g of dopamine hydrochloride and stir for 10 hours while ensuring that the liquid level is exposed to the air.

(3) Collect the product by suction filtration, and add 2L of water to rinse the material repeatedly to remove residual impurities.

(4) Dry the product at 80°C for 12 hours, then crush and sieve to obtain the negative electrode material.

The negative electrode material prepared in this comparative example includes a silicon-based active material SiO/C and a polydopamine coating layer. The specific surface area of the negative electrode material is 2.24m ² /g. The mass content of carbon element in the negative electrode material is 4.95%. The vibration of the negative electrode material The real density is 1.1g/cm ³ , the average particle size of the negative electrode material is 5.1 μm, the contact angle θ between the negative electrode material and water is 71°, and the contact angle eta between the negative electrode material and the electrolyte is 82°.

The negative electrode material was tested by XPS and found that the mass content of nitrogen in the negative electrode material was 1.8%, and the area ratio S1/S2 of the characteristic peaks of the Si element and the characteristic peak of the N element in the negative electrode material was 17.3.

Performance parameter testing

Contact angle test: Use the seat drop method to test the contact angle of powder materials to water. The negative electrode material prepared above was placed into the groove containing the powder and pressed tightly, and then tested using a contact angle measuring instrument (Shanghai Xuanyi Chuangxi Industrial Equipment Co., Ltd., model XG-CAMB3). The relevant results are shown in Table 1 Show.

XPS characterization: X-ray photoelectron spectrometer (Thermo Scientific, K-Alpha) was used to characterize the XPS information of the anode material prepared above. Among them, the excitation source is Al Kα rays, and the test results are calibrated based on C 1s = 284.8eV.

TEM characterization: Field emission transmission electron microscope (FEI Company, Tecnai G2F30) was used to characterize the thickness of the surface polymer of the anode material prepared above.

Carbon element content test: Use an infrared carbon and sulfur analyzer (Bruker Company, G4ICARUS HF) to test the carbon element content of the materials prepared in the above examples and comparative examples.

Specific surface area test: Use a specific surface area and pore size analyzer (Mac Company, ASAP2460) to test the specific surface area of the negative electrode material prepared above.

Tap density test: Use a tap density meter (Kantak Company, DAT-4-220) to test the tap density of the negative electrode material prepared above.

Average particle size test: Use a laser particle size analyzer (Malvern Company, MASTERSIZER 2000) to test the average particle size of the anode material prepared above.

Cycle performance test: Mix the negative electrode material prepared above with graphite in a ratio of 9:1, and then mix it with sodium carboxymethylcellulose, styrene-butadiene rubber, conductive graphite (KS-6) and carbon black (SP) in a ratio of 9:1. 92:2:2:2:2 is formulated into a slurry in a water solvent. Then, the slurry is evenly coated on the copper foil and dried to form a negative electrode piece. Finally, the negative electrode plates were assembled into button cells in an Ar atmosphere glove box. The separator used is a polypropylene microporous membrane, the electrolyte used is 1 mol/L lithium hexafluorophosphate (the solvent is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate), and the counter electrode used is a metal lithium sheet. The above-mentioned battery was tested for 50 cycles, with a voltage range of 0.005V to 1.5V and a current density of 50mA/g. After the cycle test, the capacity retention rate is calculated, the button battery is disassembled, and the thickness of the negative electrode piece is measured. Among them, the 50-cycle capacity retention rate = the 50th cycle discharge capacity / the first cycle discharge capacity * 100%; the negative electrode plate thickness 50-week expansion rate = (thickness after the 50th cycle - thickness of the uncharged electrode plate )/thickness of uncharged pole piece*100%. The relevant results are shown in Table 1.

Table 1 Performance parameter results table

According to the test data of the above-mentioned Examples 1 to 11, it can be seen that connecting the silicon-based active material and the flexible polymer through polyphenol compounds can enhance the interaction between the flexible polymer containing polar groups and the silicon-based active material. Improve the stability of the overall structure; coating the silicon-based active material with a flexible polymer containing polar groups can not only improve the structural stability, but also benefit the negative electrode material because the polar groups of the flexible polymer are hydrophilic. Forms strong hydrogen bonding with aqueous binders, resulting in significantly enhanced electrochemical performance.

Comparative Example 1 and Comparative Example 2 were not coated. The contact angle between the negative electrode material and water increased significantly, the hydrophilicity of the negative electrode material decreased, and there was no coating effect of the composite coating layer. The silicon-based active material was charged during the cycle. During the discharge process, the volume expands seriously and the electrochemical performance decreases.

In the negative electrode material of Comparative Example 3, the surface of the silicon-based active material is only coated with a flexible polymer. The connection between the flexible polymer and the silicon-based active material is poor, resulting in a very small amount of flexible polymer coating, incomplete coating, and failure to function. To improve the structural stability and hydrophilicity of the material, it cannot improve the electrochemical performance and volume expansion.

In the negative electrode material of Comparative Example 4, the surface of the silicon-based active material is only coated with polydopamine. Polydopamine lacks a large number of polar groups, and its hydrophilicity and flexibility are not comparable to those of flexible polymers, resulting in the hydrophilicity and flexibility of the material. The improvement in structural stability is limited and cannot significantly improve electrochemical performance and volume expansion.

Although the present disclosure is disclosed above in terms of preferred embodiments, it is not intended to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of the present disclosure. Therefore, the present disclosure is The scope of protection shall be subject to the scope defined by the claims of this disclosure.

Claims

A negative electrode material, characterized in that the negative electrode material includes a silicon-based active material and a composite coating layer located on the surface of the silicon-based active material, and the composite coating layer includes a polyphenol compound and a polar group-containing of flexible polymers.
The negative electrode material according to claim 1, characterized in that the negative electrode material includes at least one of the following features (1) to (18):

(1) The silicon-based active material includes silicon-based active particles;

(2) The silicon-based active particles include at least one of Si, SiO x and silicon alloy, where 0<x<2;

(3) The silicon-based active material includes silicon-based active particles and carbon materials;

(4) The carbon material includes at least one of amorphous carbon, amorphous carbon material and graphitized carbon material;

(5) The carbon material is located on the surface of the silicon-based active particles to form a carbon layer;

(6) The carbon material forms a buffer skeleton inside the silicon-based active material, and the silicon-based active particles are distributed around the buffer skeleton;

(7) The silicon-based active material includes silicon-based active particles and carbon materials, and the mass ratio of the silicon-based active particles to the carbon material is (30-97): (3-70);

(8) The thickness of the carbon layer is 1 nm to 1000 nm;

(9) The polyphenolic compound is connected to the carbon material in the silicon-based active material through π bonds, and the polyphenolic compound is graft-connected to the flexible polymer through covalent bonds;

(10) The polyphenolic compounds include compounds containing multiple phenolic hydroxyl groups;

(11) The polyphenolic compound includes at least one of polydopamine, polypyrogallol, polychlorogenic acid, polygallic acid, polycatechin, polylevodopa and polytannic acid;

(12) The polyphenolic compounds include oligomers and/or polymers polymerized from polyphenol monomers;

(13) The polyphenol monomer includes at least one of flavonoids, dopamine hydrochloride, pyrogallol, chlorogenic acid, gallic acid, ellagic acid, catechin, levodopa and tannic acid;

(14) The polyphenol monomer includes flavonoids, and the flavonoids include at least one of flavones, isoflavones, flavanones, flavanols, flavanonols, anthocyanins and chalcones ;

(15) The flexible polymer includes polyolefin and its derivatives, polyvinyl alcohol and its derivatives, polyacrylic acid and its derivatives, polyamide and its derivatives, carboxymethyl cellulose and its derivatives, alginic acid At least one of its derivatives;

(16) The polar group includes at least one of amino, carboxyl, hydroxyl and ethoxy;

(17) The composite coating layer includes an inner region close to the silicon-based active material and an outer region far away from the silicon-based active material, wherein the content of polyphenols in the inner region is higher than that of the outer region. The content of polyphenols in the region;

(18) The composite coating layer includes a first coating layer and a second coating layer that are sequentially laminated on the surface of the silicon-based active material. The first coating layer includes a polyphenol compound, and the third coating layer The second coating layer includes a flexible polymer containing polar groups.
The negative electrode material according to claim 1, characterized in that the negative electrode material includes at least one of the following features (1) to (13):

(1) The thickness of the composite coating layer is 1 nm to 1000 nm;

(2) The contact angle between the negative electrode material and water is θ, θ≤60°;

(3) The contact angle between the negative electrode material and the electrolyte is eta, eta ≤ 90°; wherein the electrolyte includes ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and lithium hexafluorophosphate, and the lithium hexafluorophosphate is in the The concentration in the electrolyte is 1mol/L;

(4) The contact angle between the negative electrode material and water is θ, and the contact angle between the negative electrode material and the electrolyte is eta, and satisfies (η+θ)≤120°, wherein the electrolyte includes ethylene carbonate, Ethyl methyl carbonate, dimethyl carbonate and lithium hexafluorophosphate, and the concentration of lithium hexafluorophosphate in the electrolyte is 1 mol/L;

(5) In the Raman spectrum, the negative electrode material has a carbon characteristic peak G and a silicon characteristic peak A, and the ratio of the peak intensity I A of the silicon characteristic peak A to the peak intensity I G of the carbon characteristic peak G I A /I G is 0.2~4;

(6) The composite coating layer includes amino groups. In the X-ray photoelectron spectrum, the negative electrode material has silicon characteristic peaks and nitrogen characteristic peaks. The peak area of the silicon characteristic peak is S1, and the peak area of the nitrogen characteristic peak is S1. For S2, 1＜S1/S2＜10;

(7) The composite coating layer includes amino groups. In the X-ray photoelectron spectrum, the negative electrode material has C-O bond characteristic peaks and N-C=O bond characteristic peaks. The peak area of the C-O bond characteristic peak is S3, N-C =The peak area of the characteristic peak of O bond is S4, S3/S4<10;

(8) The flexible polymer includes polyacrylamide, and the polyphenolic compound includes polydopamine;

(9) After adding 20g of negative electrode material to 300ml of water, stirring and washing, the carbon element change amount of the composite coating layer of the negative electrode material ΔC ≤ 2%;

(10) The mass content of carbon element in the negative electrode material is 1% to 50%;

(11) The specific surface area of the negative electrode material is 0.1m 2 /g ~ 10m 2 /g;

(12) The tap density of the negative electrode material is 0.5g/cm 3 to 1.5g/cm 3 ;

(13) The average particle size of the negative electrode material is 0.2 μm to 50.0 μm.
A method for preparing negative electrode materials, characterized in that the method includes:

The raw materials containing silicon-based active material, polyphenol monomer, and flexible polymer containing polar groups are coated in a solution to obtain a negative electrode material.
The preparation method according to claim 4, characterized in that the preparation method includes at least one of the following features (1) to (4):

(1) The polyphenol monomer includes at least one of flavonoids, dopamine hydrochloride, pyrogallol, chlorogenic acid, gallic acid, ellagic acid, catechin, levodopa and tannic acid;

(2) The polyphenol monomer includes flavonoids, and the flavonoids include at least one of flavones, isoflavones, flavanones, flavanols, flavanonols, anthocyanins and chalcones ;

(3) The flexible polymer includes polyolefin and its derivatives, polyvinyl alcohol and its derivatives, polyacrylic acid and its derivatives, polyamide and its derivatives, carboxymethylcellulose and its derivatives, alginic acid At least one of its derivatives;

(4) The polar group includes at least one of amino, carboxyl, hydroxyl and ethoxy.
The preparation method according to claim 4, characterized in that the preparation method includes at least one of the following features (1) to (6):

(1) The silicon-based active material includes silicon-based active particles, and the silicon-based active particles include at least one of Si, SiO x and silicon alloy, where 0<x<2;

(2) The silicon-based active material includes silicon-based active particles and carbon materials;

(3) The silicon-based active material includes silicon-based active particles and carbon materials, and the carbon materials include at least one of amorphous carbon, amorphous carbon materials and graphitized carbon materials;

(4) The silicon-based active material includes silicon-based active particles and carbon material, and the carbon material is located on the surface of the silicon-based active particles to form a carbon layer;

(5) The silicon-based active material includes silicon-based active particles and carbon material, the carbon material forms a buffer skeleton inside the silicon-based active material, and the silicon-based active particles are distributed around the buffer skeleton;

(6) The silicon-based active material includes silicon-based active particles and carbon material. The carbon material is located on the surface of the silicon-based active particles to form a carbon layer. The thickness of the carbon layer is 1 nm to 1000 nm.
The preparation method according to claim 4 or 5, characterized in that the preparation method includes at least one of the following features (1) to (6):

(1) The solution includes a pH adjuster;

(2) The pH value of the solution is 7 to 11;

(3) The solution also includes a solvent;

(4) The solvent includes at least one of water, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran and dimethyl sulfoxide;

(5) The solution includes a pH adjuster, which includes tris-hydroxymethylaminomethane-hydrochloride buffer, sodium barbiturate-hydrochloride buffer, glycine-sodium hydroxide buffer, and borax-sodium hydroxide. At least one of buffer, sodium carbonate-sodium bicarbonate buffer, ammonia, sodium hydroxide solution, potassium hydroxide solution and lithium hydroxide solution;

(6) The mass ratio of the polyphenol monomer, the flexible polymer and the silicon-based active material is (0.1~15): (0.1~15):100.
The preparation method according to claim 4, characterized in that the preparation method includes at least one of the following features (1) to (9):

(1) The coating treatment is carried out under stirring conditions;

(2) The coating treatment is performed under stirring conditions, and the stirring includes at least one of mechanical stirring and ultrasonic stirring;

(3) The coating is carried out under stirring conditions, and the stirring is carried out under the conditions of 10°C-100°C;

(4) After the raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in the solution, the method further includes separating the solution, An isolated product is obtained;

(5) After the raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in the solution, the method further includes separating the solution, An isolated product is obtained; wherein the separation includes at least one of normal pressure filtration, reduced pressure filtration and centrifugation;

(6) After the raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in the solution, the method further includes separating the solution, And the separated product is washed with water;

(7) After the raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in the solution, the method further includes separating the solution, And the separated product is washed with water and dried;

(8) After the raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in the solution, the method further includes separating the solution, The separated product is washed with water and dried, wherein the drying temperature is 40°C to 150°C;

(9) After the raw materials containing silicon-based active materials, polyphenol monomers, and polar group-containing flexible polymers are coated in the solution, the method further includes separating the solution, The separated product is washed with water and dried, wherein the drying time is 2h to 24h.
The preparation method according to claim 4, characterized in that the method includes:

Polymerize an alkaline solution containing silicon-based active materials and polyphenol monomers to obtain an alkaline solution containing polyphenol compounds;

Continue to add the flexible polymer containing polar groups into the alkaline solution, and then stir, separate, and dry to obtain the negative electrode material.
A lithium ion battery, characterized by comprising the negative electrode material according to any one of claims 1 to 3 or the negative electrode material obtained by the preparation method according to any one of claims 4 to 9.