Negative active material and preparation method thereof, negative plate and battery

Abstract

The invention discloses a negative electrode active material and a preparation method thereof, a negative plate and a battery. The negative electrode active material is a porous silicon AMPSi, CNTs and WTe2-WO3 composite negative electrode active material with a three-dimensional structure formed in a carbon fiber network matrix of carbonized bacterial cellulose CBC; the surface of the porous silicon AMPSi and the CBC carbon fiber form three-dimensional connection capable of providing buffering for expansion of the porous silicon through an amorphous carbon layer; the CNTs are staggered and connected in a three-dimensional structure of the pore silicon AMPSi and the CBC carbon fiber to form a conductive path; wTe2-WO3 heterojunctions serving as active sites for ion transmission are arranged around the porous silicon AMPSi, and the WTe2-WO3 heterojunctions are uniformly embedded into a three-dimensional structure formed by the porous silicon AMPSi and the CBC carbon fibers. The battery prepared from the negative electrode active material has excellent cycle performance, and can still maintain a high capacity retention rate after a large amount of cycles.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a negative electrode active material and a preparation method thereof, a negative electrode sheet and a battery. Background Art

[0002] The rapid development of portable electronic devices and electric vehicles requires lithium-ion batteries with higher specific power / energy, longer cycle life and competitive cost.

[0003] The theoretical specific capacity of silicon (Si) is as high as 3579 mAh g -1 (Li 15 Si 4 ), and is therefore considered one of the most promising anode materials for next-generation high-energy-density lithium-ion batteries. However, during lithiation and decay, Si undergoes a large volume change (>300%), leading to mechanical particle pulverization, loss of electrical contact between particles, and continuous formation of a solid-electrolyte interface (SEI), which results in rapid capacity decay and deterioration of battery performance. Progress has been made in addressing the particle pulverization problem by reducing the particle size to a critical nanosize. Silicon nanostructures, such as nanoparticles, nanowires, nanotubes, and nanosilicon / carbon hybrids have been developed as anode materials and have demonstrated improved cycle life compared to the bulk material.

[0004] Micron silicon not only has the advantages of high tap density, smaller specific surface area and ultra-low cost, but also has the advantages of improving volume performance and limiting interface side reactions, which has always attracted much attention. However, in practical applications, the local stress of micron silicon during lithium expansion and electrode compaction is more prominent, resulting in extremely poor electrode cycle durability, which has become an obstacle in the industrialization process. And due to the complex synthesis process, the manufacture of micron-scale silicon or silicon / carbon materials is often costly, so it has not yet been scaled up. Summary of the invention

[0005] The object of the present invention is to provide a negative electrode active material and a preparation method thereof, a pole piece and a battery in view of the above problems.

[0006] The present invention is achieved through the following technical solutions:

[0007] The first aspect of the present application provides a negative electrode active material, wherein the negative electrode active material is porous silicon AMPSi, CNTs and WTe formed into a three-dimensional structure in a carbon fiber network matrix of carbonized bacterial cellulose CBC. 2 -WO 3 Composite negative electrode active material.

[0008] The surface of the porous silicon AMPSi forms a three-dimensional connection with the CBC carbon fiber through the amorphous carbon layer, which can provide a buffer for the expansion of the porous silicon.

[0009] Furthermore, the CNTs are interlaced in the three-dimensional structure of the porous silicon AMPSi and the CBC carbon fiber to form a conductive path.

[0010] Furthermore, the porous silicon AMPSi has WTe as an active site for ion transport around it. 2 -WO 3 Heterojunction, the WTe 2 -WO 3 The heterojunction is uniformly embedded in the three-dimensional structure formed by porous silicon AMPSi and CBC carbon fibers.

[0011] The second aspect of the present application provides a method for preparing a negative electrode active material, comprising the following steps:

[0012] Thermally nitriding the magnesium-silicon alloy in nitrogen;

[0013] The thermally nitrided magnesium-silicon alloy is immersed in acid to remove Mg and N therein, thereby obtaining porous silicon AMPSi;

[0014] The porous silicon AMPSi is coated with polydopamine;

[0015] The polydopamine-coated porous silicon AMPSi is carbonized to obtain AMPSi@C, and the AMPSi@C is dispersed in carbonized bacterial cellulose CBC.

[0016] The carbonized bacterial cellulose CBC and CNTs containing AMPSi@C are uniformly dispersed in a solvent to obtain a suspension;

[0017] The suspension was centrifuged, dried, and ground into powder, and WTe was added to the powder. 2 -WO 3 , obtaining a mixed powder;

[0018] The mixed powder is heat treated under a protective atmosphere to form a negative electrode active material.

[0019] In order to optimize the above technical solutions, the specific limitations adopted also include:

[0020] The porous silicon AMPSi is coated with polydopamine, specifically, the porous silicon AMPSi and 2-amino-2-hydroxymethyl-1,3-propanediol are dispersed in water, dopamine hydrochloride is added, and filtered to obtain the porous silicon AMPSi coated with polydopamine; the reaction conditions of the carbonization treatment are: 800-900°C, heating for 2-4h in a protective atmosphere and passing hydrogen.

[0021] The method comprises dispersing AMPSi@C in carbonized bacterial cellulose CBC, wherein the mass ratio of AMPSi@C to carbonized bacterial cellulose CBC is 3-4:6-8; and the method comprises uniformly dispersing carbonized bacterial cellulose CBC containing AMPSi@C and CNTs in a solvent, wherein the mass ratio of carbonized bacterial cellulose CBC containing AMPSi@C to CNTs is 2-3:1-2.

[0022] The suspension is centrifuged, dried, ground into powder, and then WTe is added to the powder. 2 -WO 3 , to obtain a mixed powder, in which the powder and WTe 2 -WO 3 The mass ratio is 8-9:1-2; the mixed powder is heat treated under a protective atmosphere to form a negative electrode active material, wherein the heat treatment conditions are to react at 1100-1300°C for 2-3h in a protective atmosphere.

[0023] The third aspect of the present application provides a negative electrode sheet, which contains the negative electrode active material provided in the first aspect of the present application or the negative electrode active material prepared by the method provided in the second aspect of the present application.

[0024] The fourth aspect of the present application provides a battery, which contains the electrode provided by the third aspect of the present application.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention discloses a negative electrode active material, which makes porous silicon AMPSi, CNTs and WTe 2 -WO 3 A three-dimensional structure is formed in the carbonized bacterial cellulose CBC carbon fiber network matrix.

[0027] The surface of porous silicon AMPSi forms a three-dimensional connection with CBC carbon fiber through an amorphous carbon layer, which can provide a buffer for the expansion of porous silicon; CNTs are staggered in the three-dimensional structure of porous silicon AMPSi and CBC carbon fiber to form a conductive path; the surrounding of porous silicon AMPSi has WTe as an active site for ion transport. 2 -WO 3 Heterojunction, WTe 2 -WO 3 The heterojunction is uniformly embedded in the three-dimensional structure formed by porous silicon AMPSi and CBC carbon fibers.

[0028] AMPSi@C has continuous nanopores, which can achieve fast diffusion of electrolyte and high Li +Availability, and can make the nano-scale silicon ligaments interconnected to prevent powdering and cracking, AMPSi@C has excellent electrochemical properties; CNTs have good conductivity, and the CNTs in the composite material are staggered on the surface of the ant nest structure to form a complete conductive path, giving the composite material more excellent conductive properties.

[0029] The present application also improves and optimizes the composite material formed by AMPSi@C and CNTs, by strengthening the three-dimensional structure of the material in the carbon fiber network matrix of carbonized bacterial cellulose CBC, and by uniformly embedding WTe in the three-dimensional structure formed by porous silicon AMPSi and CBC carbon fibers. 2 -WO 3 The heterojunction increases the active sites for ion transport. The composite material can not only strengthen the three-dimensional structure of AMPSi@C and CNTs through carbonized bacterial cellulose CBC, provide buffer and multiple conductive paths for the expansion of porous silicon, but also avoid slow or blocked ion transport when the size and complexity of the three-dimensional structure are increased after adding CBC carbon fiber. 2 -WO 3 The heterojunction strengthens the ion transport, so that through their mutual complementation, a negative electrode active material with more advantageous overall effect can be obtained.

[0030] The battery made of the negative electrode active material of the present application has excellent cycle performance and can still maintain a high capacity retention rate after a large number of cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 : Schematic diagram of the preparation process of the present invention. DETAILED DESCRIPTION

[0032] The above contents of the present invention are further described in detail below in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the above contents of the present invention belong to the scope of the present invention.

[0033] The experimental methods used in the following examples are all conventional methods unless otherwise specified, and the reagents, methods and equipment used are all conventional reagents, methods and equipment in the technical field unless otherwise specified.

[0034] For the sake of simplicity, this document only specifically discloses some numerical values ​​and optional ranges. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range. Similarly, any upper limit can be combined with any other upper limit to form an unambiguous range; the optional items in the optional range can also be combined arbitrarily.

[0035] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art.

[0036] The present application provides a negative electrode active material, which is a porous silicon AMPSi, CNTs and WTe formed into a three-dimensional structure in a carbon fiber network matrix of carbonized bacterial cellulose CBC. 2 -WO 3 Composite negative electrode active material.

[0037] The surface of porous silicon AMPSi forms a three-dimensional connection with CBC carbon fibers through an amorphous carbon layer, which can provide a buffer for the expansion of porous silicon; CNTs are staggered in the three-dimensional structure of porous silicon AMPSi and CBC carbon fibers to form a conductive path; the porous silicon AMPSi has WTe as an active site for ion transport around it. 2 -WO 3 Heterojunction, WTe 2 -WO 3 The heterojunction is uniformly embedded in the three-dimensional structure formed by porous silicon AMPSi and CBC carbon fibers.

[0038] The present application also provides a method for preparing a negative electrode active material, comprising the following steps:

[0039] Thermally nitriding the magnesium-silicon alloy in nitrogen;

[0040] The thermally nitrided magnesium-silicon alloy is immersed in acid to remove Mg and N therein, thereby obtaining porous silicon AMPSi;

[0041] The porous silicon AMPSi is coated with polydopamine;

[0042] The polydopamine-coated porous silicon AMPSi is carbonized to obtain AMPSi@C, and the AMPSi@C is dispersed in carbonized bacterial cellulose CBC.

[0043] The carbonized bacterial cellulose CBC and CNTs containing AMPSi@C are uniformly dispersed in a solvent to obtain a suspension;

[0044] The suspension was centrifuged, dried, and ground into powder, and WTe was added to the powder. 2 -WO 3 , obtaining a mixed powder;

[0045] The mixed powder is heat treated under a protective atmosphere to form a negative electrode active material.

[0046] In some embodiments, the preparation process of the magnesium-silicon alloy is as follows:

[0047] The metallurgical silicon is ground to 1-3 μm by a sand mill; the ground silicon powder is mixed with magnesium powder in a mass ratio of 2-3:5-6, and heated to 500-600° C. in a stainless steel reactor for heat treatment for 3-5 hours to form a magnesium-silicon alloy.

[0048] In some embodiments, the conditions for thermally nitriding the magnesium-silicon alloy in nitrogen are: thermally nitriding the magnesium-silicon alloy powder in nitrogen at 700-800° C.

[0049] In some embodiments, the thermally nitrided magnesium-silicon alloy is immersed in an acid to remove Mg and N therein, wherein the acid may be 1M dilute hydrochloric acid or other acids of equal effectiveness.

[0050] In some embodiments, porous silicon AMPSi is coated with polydopamine, specifically, porous silicon AMPSi and 2-amino-2-hydroxymethyl-1,3-propanediol are dispersed in water, dopamine hydrochloride is added, and filtered to obtain porous silicon AMPSi coated with polydopamine; the reaction conditions of the carbonization treatment are: 800-900°C, heating for 2-4h in a protective atmosphere and passing hydrogen.

[0051] In some embodiments, AMPSi@C is dispersed in carbonized bacterial cellulose CBC, wherein the mass ratio of AMPSi@C to carbonized bacterial cellulose CBC is 3-4:6-8; the carbonized bacterial cellulose CBC containing AMPSi@C and CNTs are evenly dispersed in a solvent, wherein the mass ratio of carbonized bacterial cellulose CBC containing AMPSi@C to CNTs is 2-3:1-2.

[0052] In some embodiments, the suspension is centrifuged, dried, ground into powder, and then WTe is added to the powder. 2 -WO 3 , to obtain a mixed powder, in which the powder and WTe 2 -WO 3 The mass ratio of is 8-9:1-2; the mixed powder is heat-treated under a protective atmosphere to form a negative electrode active material, wherein the heat treatment condition is to react at 1100-1300° C. for 2-3 hours in a protective atmosphere.

[0053] The protective atmosphere in the present application refers to an inert gas atmosphere, and the inert gas is selected from at least one of helium, argon or a rare gas.

[0054] The present application also provides a negative electrode sheet, which contains the negative electrode active material provided in the first aspect of the present application or the negative electrode active material prepared by the method provided in the second aspect of the present application.

[0055] The present application also provides a battery, which contains the electrode provided in the third aspect of the present application.

[0056] The present application also provides an electrical device using the above-mentioned battery.

[0057] In some embodiments, the batteries of the present application may be assembled into a battery module. The number of batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0058] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0059] In an electrical device containing the battery of the present application, the battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, aircraft, ships and satellites, energy storage systems, electrical appliances, etc., but is not limited thereto; as an electrical device, the battery can be selected according to its usage requirements.

[0060] The present invention is further described in detail below in conjunction with specific embodiments. The experiments in the following embodiments are not exhaustive, and the present application has conducted experiments on various combinations of parameters:

[0061] Example 1

[0062] A preparation process of a negative electrode active material, a pole piece and a battery is as follows:

[0063] (1) Grinding metallurgical silicon to 1-3 μm with a sand mill, mixing 3 g of ground silicon powder with 5.6 g of magnesium powder, heating to 550° C. in a stainless steel reactor for 4 h to form a magnesium-silicon alloy powder of 3-5 μm;

[0064] (2) thermally nitriding the magnesium-silicon alloy powder in nitrogen at 750°C;

[0065] (3) After the thermal reaction is completed, the powder obtained by thermal nitridation is immersed in 1M dilute hydrochloric acid to remove Mg and N, and then the porous silicon AMPSi is collected by filtration;

[0066] (4) 0.4 g AMPSi and 0.48 g 2-amino-2-hydroxymethyl-1,3-propanediol were dispersed in 400 mL deionized water, and then 0.6 g dopamine hydrochloride was added under stirring, and then the polydopamine-coated porous silicon AMPSi was collected by filtration;

[0067] (5) Heating at 850 °C under Ar / H co-protection conditions for 3 h, during which the polydopamine coating was carbonized to obtain AMPSi@C;

[0068] (6) dispersing AMPSi@C in carbonized bacterial cellulose (CBC), with the mass ratio of AMPSi@C to carbonized bacterial cellulose (CBC) being 1:2;

[0069] (7) uniformly dispersing the carbonized bacterial cellulose CBC containing AMPSi@C and CNTs in anhydrous ethanol by ultrasonic stirring until a uniformly dispersed suspension is obtained, wherein the mass ratio of the carbonized bacterial cellulose CBC containing AMPSi@C to the CNTs is 2:1.5;

[0070] (8) The obtained suspension was centrifuged, dried, and ground into powder, and WTe was added to the powder. 2 -WO 3 , and obtain a mixed powder; the suspension is centrifuged and dried, and the ground powder is mixed with WTe 2 -WO 3 The mass ratio is 8:1.7;

[0071] (9) placing the mixed powder into a tube furnace, reacting at 1200° C. for 3 h in an Ar atmosphere with a flow rate of 250 mL / min to obtain a negative electrode active material;

[0072] (10) Preparation of electrode sheet: The negative electrode active material prepared in step (9), the conductive agent acetylene black and the binder sodium carboxymethyl cellulose (CMC) are ground and mixed in a mass ratio of 8:1:1, and appropriate amounts of deionized water and anhydrous ethanol are added. The mixture is stirred magnetically for 12 hours to obtain a slurry for preparing the electrode. The slurry is evenly coated on a copper foil using a coating machine, and the copper foil is placed in an oven at 80°C and vacuum dried for 12 hours. A mechanical punch is used to punch holes to obtain a circular negative electrode active electrode sheet with a diameter of 12 mm. The mass is weighed for assembly. (11) Battery assembly: The battery assembly is carried out in a glove box filled with Ar gas, and the battery is assembled into a half-cell of model CR2032. A metal lithium sheet is used as the counter electrode of the battery, and a Celgard2400 polypropylene material film is used as the diaphragm. The electrolyte solvent is ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1, and the solute is lithium hexafluorophosphate (LiPF 6 ), the additive is fluoroethylene carbonate (FEC); the assembly order is negative electrode shell, negative active electrode sheet, separator, positive electrode sheet (lithium sheet), gasket, spring and positive electrode shell. After assembly, it is sealed and compacted with a battery sealing machine, and then the performance test is carried out after standing for 24 hours.

[0073] Example 2

[0074] The process and parameters of this embodiment are basically the same as those of Embodiment 1, except that the mass ratio of AMPSi@C to carbonized bacterial cellulose CBC in step (6) is 1:3.

[0075] Example 3

[0076] The process and parameters of this embodiment are basically the same as those of Embodiment 1, except that the mass ratio of AMPSi@C to carbonized bacterial cellulose CBC in step (6) is 1:1.

[0077] Example 4

[0078] The process and parameters of this embodiment are basically the same as those of Embodiment 1, except that the mass ratio of the powder obtained by drying and grinding the suspension after centrifugation in step (8) to WTe2-WO3 is 10:1.

[0079] Example 5

[0080] The process and parameters of this embodiment are basically the same as those of Embodiment 1, except that the mass ratio of the powder obtained by drying and grinding the suspension after centrifugation in step (8) to WTe2-WO3 is 7:2.

[0081] Comparative Example 1

[0082] The preparation process of Comparative Example 1 is basically the same as that of Example 1, except that: there is no step (6), and AMPSi@C and CNTs are directly dispersed uniformly in anhydrous ethanol by ultrasonic stirring, and the mass ratio of AMPSi@C to CNTs is 2:1.5.

[0083] Comparative Example 2

[0084] The preparation process of Comparative Example 2 is basically the same as that of Example 1, except that: there is no step (6), and AMPSi@C and CNTs are directly dispersed uniformly in anhydrous ethanol by ultrasonic stirring, and the mass ratio of AMPSi@C to CNTs is 2:4.5.

[0085] Comparative Example 3

[0086] The preparation process of Comparative Example 3 is basically the same as that of Example 1, except that: Step (8) does not incorporate WTe 2 -WO 3 Instead, the suspension is centrifuged, dried, and ground into powder and placed in a tubular furnace for thermal reaction.

[0087] Comparative Example 4

[0088] The preparation process of Comparative Example 4 is basically the same as that of Example 1, except that: there is no step (6), and AMPSi@C and CNTs are directly dispersed uniformly in anhydrous ethanol by ultrasonic stirring, and the mass ratio of AMPSi@C to CNTs is 2:1.5; and step (8) does not incorporate WTe 2 -WO 3 Instead, the suspension is centrifuged, dried, and ground into powder and placed in a tubular furnace for thermal reaction.

[0089] Comparative Example 5

[0090] The preparation process of Comparative Example 5 is basically the same as that of Example 1, except that: there is no step (6), and AMPSi@C and CNTs are directly dispersed uniformly in anhydrous ethanol by ultrasonic stirring, and the mass ratio of AMPSi@C to CNTs is 2:4.5; and step (8) does not incorporate WTe 2 -WO 3 Instead, the suspension is centrifuged, dried, and ground into powder and placed in a tubular furnace for thermal reaction.

[0091] Comparative Example 6

[0092] The negative electrode active material directly adopts commercial silicon carbon powder.

[0093] The above embodiments and comparative examples were subjected to cycle performance tests, and the test results are shown in Table 1:

[0094] Table 1 Cyclic performance test results of embodiments and comparative examples

[0095]

[0096] This application has been proven through experiments:

[0097] By comparing Example 1 with Comparative Examples 1-6, it can be seen that the embodiment of the present invention has significantly better performance data. The silicon-based material of the embodiment of the present invention introduces a rich porous structure, which increases the contact area between the silicon-based material and the electrolyte, allowing more lithium ions to participate in the reaction, thereby increasing the specific capacity of the battery; providing a buffer space for the expansion of the silicon material during the charge and discharge process, reducing the stress caused by volume change, reducing the risk of material structure damage and particle agglomeration, and improving the material's cycle stability and capacity retention rate; the porous structure provides more ion transmission channels, shortens the ion diffusion path, allows lithium ions to migrate more quickly in the electrode material, speeds up the charge and discharge speed of the battery, achieves high power performance, and improves the overall performance and efficiency; and the larger surface area provides more active sites, which is beneficial to the charge transfer and chemical reaction between the electrode and the electrolyte, improving the charge and discharge efficiency and electrochemical performance of the battery, thereby improving the overall performance of the battery; in addition, the voids in the porous structure can be used as channels for heat transfer, which is beneficial to the dissipation of heat, preventing the battery from overheating during the charge and discharge process and causing performance degradation or safety problems, thereby improving the safety and reliability of the battery; the overall density of the material is reduced, and in some application scenarios that have weight requirements, such as portable electronic devices, electric vehicles, etc., the weight of the equipment or vehicle can be reduced, and the energy efficiency and endurance can be improved.

[0098] By comparing Example 1 with Comparative Examples 2-5, it can be seen that the mass ratio of AMPSi@C to carbonized bacterial cellulose CBC in step (6) and the mass ratio of the powder obtained by drying and grinding the suspension after centrifugation to WTe2-WO3 in step (8) are controlled within a certain range, which can produce better results. Preferably, when AMPSi@C is dispersed in carbonized bacterial cellulose CBC, the mass ratio of AMPSi@C to carbonized bacterial cellulose CBC is 3-4:6-8; after the suspension is dried and ground into powder after centrifugation, WTe2-WO3 is added to the powder. 2 -WO 3 When the mixed powder is obtained, the powder and WTe 2 -WO 3 The mass ratio is 8-9:1-2.

[0099] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, according to the technical essence of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A negative electrode active material, characterized in that: The negative electrode active material is a porous silicon AMPSi, CNTs and WTe2-WO3 composite negative electrode active material with a three-dimensional structure formed in a carbon fiber network matrix of carbonized bacterial cellulose CBC.

2. The negative electrode active material according to claim 1, characterized in that: The surface of the porous silicon AMPSi forms a three-dimensional connection with the CBC carbon fiber through the amorphous carbon layer, which can provide a buffer for the expansion of the porous silicon.

3. The negative electrode active material according to claim 2, characterized in that: The CNTs are interlaced in the three-dimensional structure of porous silicon AMPSi and CBC carbon fiber to form a conductive path.

4. The negative electrode active material according to claim 3, characterized in that: The porous silicon AMPSi is surrounded by a WTe2-WO3 heterojunction serving as an active site for ion transmission, and the WTe2-WO3 heterojunction is uniformly embedded in a three-dimensional structure formed by the porous silicon AMPSi and the CBC carbon fiber.

5. The method for preparing the negative electrode active material according to any one of claims 1 to 4, characterized in that: The following steps are involved: Thermally nitriding the magnesium-silicon alloy in nitrogen; The thermally nitrided magnesium-silicon alloy is immersed in acid to remove Mg and N therein, thereby obtaining porous silicon AMPSi; The porous silicon AMPSi is coated with polydopamine; The polydopamine-coated porous silicon AMPSi is carbonized to obtain AMPSi@C, and the AMPSi@C is dispersed in carbonized bacterial cellulose CBC. The carbonized bacterial cellulose CBC and CNTs containing AMPSi@C are uniformly dispersed in a solvent to obtain a suspension; The suspension is centrifuged, dried, and ground into powder, and WTe2-WO3 is added to the powder to obtain a mixed powder; The mixed powder is heat treated under a protective atmosphere to form a negative electrode active material.

6. The method for preparing the negative electrode active material according to claim 5, characterized in that: The porous silicon AMPSi is coated with polydopamine, specifically, the porous silicon AMPSi and 2-amino-2-hydroxymethyl-1,3-propanediol are dispersed in water, dopamine hydrochloride is added, and filtered to obtain the porous silicon AMPSi coated with polydopamine; the reaction conditions of the carbonization treatment are: 800-900°C, heating for 2-4h in a protective atmosphere and passing hydrogen.

7. The method for preparing the negative electrode active material according to claim 5, characterized in that: The method comprises dispersing AMPSi@C in carbonized bacterial cellulose CBC, wherein the mass ratio of AMPSi@C to carbonized bacterial cellulose CBC is 3-4:6-8; and the method comprises uniformly dispersing carbonized bacterial cellulose CBC containing AMPSi@C and CNTs in a solvent, wherein the mass ratio of carbonized bacterial cellulose CBC containing AMPSi@C to CNTs is 2-3:1-2.

8. The method for preparing the negative electrode active material according to claim 5, characterized in that: The suspension is centrifuged, dried, and ground into powder, and WTe2-WO3 is added to the powder to obtain a mixed powder, wherein the mass ratio of the powder to WTe2-WO3 is 8-9:1-2; the mixed powder is heat-treated under a protective atmosphere to form a negative electrode active material, wherein the heat treatment condition is to react at 1100-1300°C for 2-3h in a protective atmosphere.

9. A negative electrode sheet, characterized in that: The electrode sheet contains the negative electrode active material according to any one of claims 1 to 4 or the negative electrode active material prepared by the method according to any one of claims 5 to 8.

10. A battery, characterized in that: The battery comprises the electrode sheet according to claim 9.

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