Preparation method of nitrogen-phosphorus self-doped carbon-coated manganese oxide composite material derived based on waste dairy products and lithium ion negative electrode composite material

Abstract

The invention discloses a preparation method of a nitrogen-phosphorus self-doped carbon-coated manganese oxide composite material derived based on waste dairy products and a lithium ion negative electrode composite material. According to the preparation method, expired milk powder is taken as a carbon source, a nitrogen source and a phosphorus source, manganese acetate tetrahydrate is taken as a manganese source, a freeze drying and gradient annealing technology is cooperated to realize lactose carbonization confinement effect to inhibit MnO agglomeration, casein pyrolysis is carried out to realize nitrogen and phosphorus self-doping, and a composite material (MnO-N, P-C) with MnO coated with a nitrogen and phosphorus co-doped three-dimensional interconnected carbon skeleton is prepared, the particle size of the cubic MnO nano-particles is about 60nm, the carbon matrix presents a three-dimensional interconnected porous network, the whole MnO cubic nano-particles are coated by a three-dimensional interconnected carbon skeleton, and the N / P atomic ratio is 1.5: 1. The obtained nitrogen and phosphorus co-doping is more uniform, the framework of the co-doped carbon-coated manganese oxide has scalability, the volume expansion of the active material can be relieved and the self-agglomeration of the manganese oxide can be inhibited in the charging and discharging process, and meanwhile, the composite material can effectively improve the electronic conductivity and the lithium ion reaction kinetics. The composite electrode has excellent rate capability and long cycle life.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials, and particularly relates to a preparation method of a nitrogen and phosphorus self-doped carbon-coated manganese oxide composite material and a lithium ion negative electrode composite material derived from waste dairy products, and particularly relates to a technical solution for preparing a nitrogen and phosphorus self-doped carbon-coated manganese oxide nanocomposite material by a freeze-drying-gradient annealing process using expired dairy products. Background Art

[0002] With the continuous growth of global energy demand and the rapid development of markets such as electric vehicles and portable electronic devices, the demand for high-performance lithium ion batteries is increasing day by day. As a key component of lithium ion batteries, the negative electrode material is one of the keys affecting the overall performance of lithium ion batteries. At present, graphite is widely used as the negative electrode material for commercial lithium ion batteries, but its theoretical specific capacity is relatively low (372 mAh g -1 ), which is difficult to meet the growing demand for high energy density. Therefore, the development of new negative electrode materials with high specific capacity, good cycle stability and low cost has become a research hotspot.

[0003] Manganese monoxide (MnO) is considered a potential negative electrode material for lithium ion batteries due to its high theoretical specific capacity, rich reserves, low price and environmental friendliness. However, pure manganese monoxide faces problems such as poor electrical conductivity, large volume change and rapid capacity decay in practical applications, which limit its commercial application.

[0004] To overcome these problems, researchers have tried to nano-scale manganese monoxide and composite it with carbon materials to improve its structural stability and electrical conductivity. Among them, nitrogen and phosphorus doped carbon materials have become an ideal choice for composite with manganese monoxide due to their excellent electrical conductivity, high specific surface area and rich active sites. Although there have been studies on the composite of manganese monoxide and carbon materials to improve their electrochemical performance, the existing technologies mainly have the following deficiencies: 1. Unsustainable carbon source: Traditional carbon coating processes mostly use chemical raw materials such as glucose and phenolic resin, which are costly and lack environmental friendliness. 2. Low doping efficiency: Exogenous doping (such as NH4H2PO4) leads to uneven element distribution and produces harmful by-products (such as PH3). 3. Insufficient structural design: The existing core-shell structures fail to simultaneously solve the problems of improving electrical conductivity and suppressing volume expansion, and the capacity of the MnO negative electrode decays greatly after cycling. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the present invention aims to provide a nitrogen and phosphorus co-doped carbon-coated manganese oxide composite material derived from waste dairy products, a preparation method thereof, and a lithium-ion negative electrode composite material. The nitrogen and phosphorus co-doped carbon-coated manganese oxide composite material uses expired milk powder as a carbon source, a nitrogen source, and a phosphorus source to achieve uniform self-doping of nitrogen and phosphorus. Nitrogen-doped carbon not only provides abundant surface active sites, enhances the lithium-ion adsorption capacity, but also improves the electronic conductivity, which is beneficial to the rapid transfer of electrons; phosphorus doping induces topological defects in the carbon skeleton, promoting the kinetics of lithium-ion insertion / extraction; the three-dimensional interconnected network and reversible wrinkling deformation of the carbon skeleton effectively buffer the volume expansion of manganese oxide during charge and discharge, and it has excellent electrochemical performance when applied as a lithium-ion battery negative electrode material. At the same time, the present invention realizes the effective utilization of waste resources, and the preparation method is simple, easy to operate, low in cost and environmentally friendly, suitable for large-scale production.

[0006] The above object is achieved by the following technical solutions: A preparation method of a nitrogen and phosphorus co-doped carbon-coated manganese oxide composite material derived from waste dairy products includes the following steps:

[0007] (1) Mix milk powder and a manganese source in a mass ratio of 0.5:1.225 - 2.0:1.225, dissolve them in deionized water at 50 - 80 °C, and stir for 2 - 4 h to form a homogeneous precursor solution;

[0008] (2) Freeze the solution to below -20 °C to form an ice crystal template, and then freeze-dry for 24 - 48 h to obtain a porous precursor;

[0009] (3) Perform gradient annealing in an inert atmosphere:

[0010] The first stage: Keep the temperature at 300 - 400 °C for 1 - 2 h to achieve the decomposition of milk protein and the complexation of Mn 2+ complexation;

[0011] The second stage: Keep the temperature at 700 - 900 °C for 2 - 4 h, synchronously complete the carbonization of lactose and the crystallization of MnO, and finally obtain a nitrogen and phosphorus co-doped carbon-coated manganese oxide composite material.

[0012] A further technical solution is that in the step (1), the manganese source is one or more of manganese acetate tetrahydrate, manganese nitrate, and manganese chloride. Preferably, the manganese source is manganese acetate tetrahydrate.

[0013] A further technical solution is that in the step (1), the milk powder is expired milk powder.

[0014] A further technical solution is that in the step (1), the mass ratio of the expired milk powder to manganese acetate tetrahydrate is preferably 1:1.225.

[0015] A further technical solution is that in the step (1), the temperature of the deionized water is preferably 60 °C.

[0016] A further technical solution is that the freeze-vacuum drying time in the step (2) is preferably 36 h.

[0017] A further technical solution is that the annealing temperatures in the first and second stages in the step (3) are preferably 350 °C and 850 °C respectively.

[0018] A further technical solution is that the annealing times in the first and second stages in the step (3) are preferably 1.5 h and 3 h respectively.

[0019] A further technical solution is that the inert gas is nitrogen or argon, preferably argon.

[0020] The main constituent materials in the composite electrode prepared by the above method are nitrogen and phosphorus co-doped carbon and manganese monoxide. In this scheme, expired milk powder is used as the carbon source, nitrogen source, and phosphorus source, and manganese acetate tetrahydrate is used as the manganese source. Through the freeze-drying synergistic gradient annealing process, the lactose carbonization confinement effect is realized to inhibit the agglomeration of MnO, and the thermal decomposition of casein realizes the uniform self-doping of nitrogen and phosphorus. Its characteristics are that the surface of cubic MnO nanoparticles (particle size 50-80 nm) is coated with an amorphous carbon layer, the carbon matrix presents a three-dimensional interconnected porous network, and the entire MnO nanoparticle is coated by a three-dimensional interconnected carbon skeleton, and the N / P atomic ratio is 1.5:1. This composite structure can effectively alleviate the problem of MnO volume expansion during the cycling process, and at the same time provides a more effective lithium-ion transmission channel, improves the stress resistance of the material, and thus can improve the rate performance and cycling performance of lithium-ion batteries. Therefore, it has good application prospects in the fields of lithium-ion batteries and the like.

[0021] In addition, a preparation of a lithium-ion battery anode composite material is also provided. The lithium-ion battery anode composite material uses the nitrogen and phosphorus self-doped carbon-coated manganese oxide composite material prepared by the foregoing scheme as the base material. The preparation method of the lithium-ion battery anode includes:

[0022] Grind the mixed powder of the lithium-ion battery anode composite material, conductive agent, and binder evenly, wherein the mass ratio of the lithium-ion battery anode composite material, conductive agent, and binder is 8:1:1; add N-methylpyrrolidone until the liquid completely wets the evenly mixed powder, and stir for 10-15 h. Then, coat the slurry evenly on the copper foil, and then place the copper foil in a vacuum at a temperature of 80-100 °C for 12-15 h, and then obtain a negative electrode sheet with a diameter of 10 mm through a punching machine to obtain a lithium-ion battery anode.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The lithium-ion battery anode composite material prepared by the method of the present invention uses an ice template-induced lactose carbonized layer to effectively restrict the growth of MnO grains, obtaining highly dispersed cubic-phase MnO nanocrystals.

[0025] (2) The thermal decomposition of casein produces an N / P co-doped carbon matrix, constructing a three-dimensional interconnected carbon network. This structure is beneficial to the penetration of the electrolyte and improves the utilization rate of the active material.

[0026] (3) For the nitrogen and phosphorus co-doped carbon-coated manganese oxide composite anode material prepared by the present invention, the nitrogen-doped carbon not only provides abundant surface active sites, enhancing the lithium-ion adsorption ability, but also improves the electronic conductivity, facilitating the rapid transfer of electrons. Phosphorus doping induces topological defects in the carbon skeleton, promoting the lithium-ion insertion / extraction kinetics. The three-dimensional interconnected carbon skeleton and reversible wrinkling deformation effectively buffer the volume change during charge and discharge and inhibit the aggregation of manganese oxide particles. Therefore, when used as the anode material of a lithium-ion battery, it exhibits high reversible capacity, excellent rate performance, and long cycle life.

[0027] (4) The lithium-ion battery anode composite material prepared by the method of the present invention uses dairy waste as a biomass carbon source, nitrogen source, and phosphorus source to achieve in-situ uniform self-doping of nitrogen and phosphorus, avoiding uneven element distribution, high cost, and environmental pollution caused by external doping, and effectively turning waste into treasure.

[0028] (5) The present invention uses a combined method of freeze-drying and gradient annealing to prepare an anode material of nitrogen and phosphorus co-doped carbon-coated manganese monoxide. Its process is simple and easy to implement, has good repeatability, low equipment requirements, and is applicable to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0030] Figure 1 XRD pattern of the MnO@N,P-C composite material prepared in Example 1 of the present invention;

[0031] Figure 2 XPS pattern of the MnO@N,P-C composite material prepared in Example 1 of the present invention;

[0032] Figure 3 (a) SEM image of the MnO@N,P-C composite material prepared in Example 1 of the present invention;

[0033] Figure 3 (b) TEM image of the MnO@N,P-C composite material prepared in Example 1 of the present invention;

[0034] Figure 3 (c) Energy spectrum Mapping diagram corresponding to the SEM of the MnO@N,P-C composite material prepared in Example 1 of the present invention;

[0035] Figure 4 TGA diagram of the MnO@N,P-C composite material prepared in Example 1 of the present invention;

[0036] Figure 5 (a) CV curve of the MnO@N,P-C composite material electrode prepared in Example 1 of the present invention as the negative electrode of a lithium-ion battery at a scanning rate of 0.2 mV s -1 ;

[0037] Figure 5 (b) Charge-discharge curves of different cycle numbers of the MnO@N,P-C composite material electrode prepared in Example 1 of the present invention as the negative electrode of a lithium-ion battery at a current density of 0.2 Ag -1 ;

[0038] Figure 5 (c) Rate performance diagram of the MnO@N,P-C composite material electrode prepared in Example 1 of the present invention as the negative electrode of a lithium-ion battery at different current densities;

[0039] Figure 5 (d) Cycle performance diagram of the MnO@N,P-C composite material electrode prepared in Example 1 of the present invention as the negative electrode of a lithium-ion battery at a current density of 0.2 Ag -1 ;

[0040] Figure 5 (e) Cycle performance diagram of the MnO@N,P-C composite material electrode prepared in Example 1 of the present invention at a current density of 1.0 Ag -1 ; Detailed implementation mode

[0041] The present invention will be described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory, and should not have any restrictive effect on the protection scope of the present invention. In addition, those skilled in the art can make corresponding combinations of the features in the embodiments and different embodiments in this document according to the description of this document.

[0042] Example 1

[0043] Weigh 1.0 g of expired milk powder and 1.225 g of manganese acetate tetrahydrate, put them into 50 ml of deionized water at 60 °C, stir to disperse and dissolve. After stirring for 3 hours to make it evenly dispersed, quickly put it into the refrigerator for freezing and forming, then carry out freeze-drying for 36 h. Finally, put the dried porous white precursor into a tubular furnace with argon gas for gradient annealing. The first stage is to keep the temperature at 350 °C for 1.5 hours, and the second stage is to keep the temperature at 850 °C for 3 h. Finally, a composite material with manganese oxide coated by nitrogen and phosphorus co-doped three-dimensional interconnected carbon framework (i.e., MnO@N,P-C) is obtained.

[0044] Prepare the composite material with manganese oxide coated by nitrogen and phosphorus co-doped three-dimensional interconnected carbon framework into a composite electrode and use it for electrochemical performance testing.

[0045] Specific properties of the product: XRD and XPS characterizations show that the MnO@N,P-C composite material contains manganese monoxide; SEM and TEM characterizations confirm that manganese monoxide is coated by a three-dimensional interconnected carbon framework. Manganese monoxide is evenly dispersed with almost no agglomeration, and the average size of manganese monoxide is about 60 nm; Thermogravimetric analysis shows that the content of manganese monoxide in the composite material is 67%.

[0046] After electrochemical performance testing, the prepared composite electrode with manganese oxide coated by nitrogen and phosphorus co-doped three-dimensional carbon framework shows the best data when used as the anode of a lithium-ion battery.

[0047] From Figure 1 it can be seen that the peak positions of the composite electrode material with manganese oxide coated by nitrogen and phosphorus co-doped three-dimensional carbon framework correspond one by one to the standard card of manganese monoxide (JCPDS no.07-0230), indicating that the prepared material contains manganese monoxide.

[0048] From Figure 2 it can be seen that the high-resolution XPS spectrum of Mn 2p for the composite electrode material with manganese oxide coated by nitrogen and phosphorus co-doped three-dimensional carbon framework shows two peaks with binding energies of 641.5 eV and 653.4 eV corresponding to Mn 2p 3 / 2 and Mn 2p 1 / 2 , indicating that manganese in manganese oxide in this electrode is divalent positive, thus determining that this composite material contains manganese monoxide.

[0049] From Figure 3 (a) it can be seen that cubic particles of manganese monoxide are coated by a three-dimensional interconnected carbon framework, with almost no agglomeration, and the average size of the cubic particles is about 60 nm; Figure 3 (b) can more clearly show that the carbon framework coats manganese monoxide, and the average diameter size is about 60 nm, and there is no agglomeration phenomenon at the same time, which is consistent with Figure 3 (a) above; Figure 3(c) The corresponding energy spectrum Mapping diagram of SEM shows the uniform distribution of Mn, O, C, N, and P elements, indicating the uniform doping of N and P elements.

[0050] From Figure 4 it can be obtained that the content of manganese monoxide in the composite material is 67%.

[0051] From Figure 5 (a) It can be seen that there is a pair of redox peaks, corresponding to the reduction of manganese monoxide and the oxidation of manganese respectively; Figure 5 (b) is the charge-discharge curve of the nitrogen and phosphorus co-doped three-dimensional carbon framework coated manganese oxide composite material as the anode material of the lithium battery at 0.1 A / g. Through the charge-discharge curve, it can be judged that the nitrogen and phosphorus co-doped three-dimensional carbon framework coated manganese oxide composite material has excellent cycle stability; Figure 5 (c) is the rate performance diagram of the nitrogen and phosphorus co-doped three-dimensional carbon framework coated manganese oxide composite electrode as the anode of the lithium ion battery at different current densities. Through the rate performance diagram, it can be found that: at 0.1, 0.2, 0.5, 1.0, 2.0, 4.0 A g -1 the specific capacities at the current densities are 920.3, 859.9, 760.4, 660.6, 506.9, 317.8 mAh / g respectively; Figure 5 (d) is the cycle performance diagram of the nitrogen and phosphorus co-doped three-dimensional carbon framework coated manganese oxide composite electrode as the anode of the lithium ion battery at 0.2 A g -1 current density. Through this diagram, it can be found that: after 180 cycles, the nitrogen and phosphorus co-doped three-dimensional carbon framework coated manganese oxide composite electrode has a high specific capacity of 983.9 mAh / g, showing excellent cycle stability; Figure 5 (e) It can be known that the nitrogen and phosphorus co-doped three-dimensional carbon framework coated manganese oxide composite electrode was first cycled 2 times at a current density of 0.2 A g -1 to better activate the material. The discharge specific capacity after the 3rd cycle is 627.5 mAh / g, and then it was cycled 600 times at a current density of 1.0 A g -1 current density. When the cycle reaches 600 times, the discharge specific capacity is as high as 526.1 mAh / g, and the specific capacity retention rate is as high as 84% (compared with the third cycle), showing that: this electrode has excellent cycle life and high specific capacity at high current density.

[0052] Example 2

[0053] Weigh 0.5 g of expired milk powder and 1.225 g of manganese acetate tetrahydrate, put them into 50 ml of deionized water at 60 °C, stir to disperse and dissolve. After stirring for 3 hours to make it evenly dispersed, quickly put it into the refrigerator to freeze and form. Then freeze-dry it for 36 h. Finally, put the dried porous white precursor into a tubular furnace with argon gas for gradient annealing. The first stage is to keep the temperature at 350 °C for 1.5 hours, and the second stage is to keep the temperature at 850 °C for 3 h to finally form manganese monoxide and nitrogen and phosphorus co-doped carbon composite materials.

[0054] Specific properties of the product: The composite material contains manganese monoxide material characterized by XRD; the three-dimensional carbon framework coating manganese monoxide structure is determined by SEM, and its characteristics are: the size distribution of MnO is uneven and there is agglomeration; the content of manganese monoxide is 79% obtained by thermogravimetric analysis.

[0055] Example 3

[0056] Weigh 2.0 g of expired milk powder and 1.225 g of manganese acetate tetrahydrate, put them into 50 ml of deionized water at 60 °C, stir to disperse and dissolve. After stirring for 3 hours to make it evenly dispersed, quickly put it into the refrigerator to freeze and form. Then freeze-dry it for 36 h. Finally, put the dried porous white precursor into a tubular furnace with argon gas for gradient annealing. The first stage is to keep the temperature at 350 °C for 1.5 hours, and the second stage is to keep the temperature at 850 °C for 3 h to form manganese monoxide and nitrogen and phosphorus co-doped carbon composite materials.

[0057] Specific properties of the product: The composite material contains manganese monoxide material characterized by XRD; the three-dimensional carbon framework coating manganese monoxide structure is determined by SEM, and its characteristics are: the average size of MnO is 60 nm, and it is evenly dispersed with almost no agglomeration; the content of manganese monoxide in the composite material is 56% obtained by thermogravimetric analysis.

[0058] Example 4

[0059] Weigh 1.225 g of manganese acetate tetrahydrate, put it into 50 ml of deionized water at 60 °C, stir to disperse and dissolve. After stirring for 3 hours to make it evenly dispersed, quickly put it into the refrigerator to freeze and form. Then freeze-dry it for 36 h. Put the dried precursor into a tubular furnace with argon gas for gradient annealing. The first stage is to keep the temperature at 350 °C for 1.5 hours, and the second stage is to keep the temperature at 850 °C for 3 h to form pure manganese monoxide material.

[0060] Specific properties of the product: It is shown as pure manganese monoxide material characterized by XRD; the manganese monoxide is determined to be a cubic structure by SEM, and its characteristics are: the average size of MnO is about 500 nm, which is much larger than the size of MnO in the composite material and there is serious agglomeration.

[0061] Morphology and Microstructure Characterization of Manganese Oxide Coated with Nitrogen and Phosphorus Co-doped Three-dimensional Carbon Skeleton Composite Material

[0062] The structure and morphology of the manganese oxide coated with nitrogen and phosphorus co-doped three-dimensional carbon skeleton composite material were characterized by a Ragaku D-type (produced by Rigaku, Japan) X-ray Diffractometer (XRD), a transmission electron microscope (TEM) of model JEOL JEM-2100 (produced by JEOL Ltd., Japan), and an S4800 scanning electron microscope (SEM). The content of manganese monoxide in the composite material was analyzed by a NETZSCH TG 209F1 Libra thermogravimetric analyzer.

[0063] Electrode Battery Assembly and Electrochemical Performance Test of Manganese Oxide Coated with Nitrogen and Phosphorus Co-doped Three-dimensional Carbon Skeleton Composite Material

[0064] The electrode of the manganese oxide coated with nitrogen and phosphorus co-doped three-dimensional carbon skeleton composite material was cut into circular pieces with a mass of 1.0 - 1.5 mg and directly used as the working electrode, a metallic lithium sheet was used as the counter electrode, 1 mol / L LiPF6 - EC / DC (volume ratio 1:1) with an additional 5% FEC additive was used as the electrolyte, and polypropylene celgard 2325 was used as the separator to assemble a 2025-type button half-cell in a glove box under a high-purity argon atmosphere. The galvanostatic charge-discharge test (GCD) was carried out on a Neware battery test system, and the test voltage range was 0.01 - 3.00 V. The cyclic voltammetry (CV) test was carried out on a Chenhua CHI660 electrochemical workstation.

[0065] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a nitrogen and phosphorus self-doped carbon-coated manganese oxide composite material derived from waste dairy products, characterized in that, It includes the following steps: (1) Mix milk powder and manganese source in a mass ratio of 0.5:1.225 - 2.0:1.225, dissolve in deionized water at 50 - 80 °C, and stir for 2 - 4 h to form a homogeneous precursor solution; (2) Freeze the solution to below -20 °C to form an ice crystal template, and then freeze-dry for 24 - 48 h to obtain a porous precursor; (3) Perform gradient annealing in an inert atmosphere: The first stage: Keep the temperature at 300 - 400 °C for 1 - 2 h to achieve the decomposition of milk protein and the complexation of Mn 2+ complexation; The second stage: Keep it at 700 - 900 °C for 2 - 4 h to simultaneously complete the carbonization of lactose and the crystallization of MnO to obtain the final product.

2. The preparation method of a nitrogen and phosphorus self-doped carbon-coated manganese oxide composite material derived from waste dairy products according to claim 1, characterized in that, The milk powder used in step (1) is expired milk powder.

3. The preparation method of a nitrogen and phosphorus self-doped carbon-coated manganese oxide composite material derived from waste dairy products according to claim 2, wherein, The contents of calcium and zinc in the expired milk powder account for 0.5% - 1.3% and 0.006% - 0.0112% respectively.

4. The preparation method of a nitrogen and phosphorus self-doped carbon-coated manganese oxide composite material derived from waste dairy products according to claim 1, characterized in that, The manganese source used in step (1) is one or more of manganese acetate tetrahydrate, manganese nitrate, and manganese chloride.

5. The preparation method of a nitrogen and phosphorus self-doped carbon-coated manganese oxide composite material derived from waste dairy products according to claim 1, characterized in that, The inert gas in step (3) is nitrogen or argon.

6. A nitrogen and phosphorus self-doped carbon-coated manganese oxide composite material prepared by the preparation method according to any one of claims 1 to 5, characterized in that, The composite material is applied to the preparation of the anode composite material of a lithium-ion battery.

7. A negative electrode composite material for a lithium-ion battery, characterized in that, The anode composite material of the lithium-ion battery is a nitrogen and phosphorus self-doped carbon-coated manganese oxide composite material prepared by the preparation method described in any one of claims 1 - 6, The preparation method of the anode of the lithium-ion battery includes: Grind the mixed powder of the anode composite material of the lithium-ion battery, a conductive agent, and a binder evenly, wherein the mass ratio of the anode composite material of the lithium-ion battery, the conductive agent, and the binder is 8:1:1; add N-methylpyrrolidone until the liquid completely wets the evenly mixed powder, and stir for 10 - 15 h. Then coat the slurry evenly on a copper foil, place the copper foil in a vacuum at 80 - 100 °C and dry for 12 - 15 h, and then obtain a negative electrode sheet with a diameter of 10 mm through a punching machine to obtain the anode of the lithium-ion battery.

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