Preparation method of a tridymanganese tetraoxide and nitrogen-doped honeycomb carbon composite negative electrode material

Abstract

The application belongs to the technical field of lithium ion batteries, and provides a preparation method of a trimanganese tetraoxide and nitrogen-doped honeycomb carbon composite negative electrode material; polyacrylamide, urea and sodium chloride are dissolved in deionized water, and manganese acetate tetrahydrate is added under stirring; the obtained solution is cooled in a refrigerator and freeze-dried, and the dried precursor is calcined in an argon atmosphere; the obtained product is washed with deionized water and suction-filtered, and the washed sample is dried in an oven to obtain the trimanganese tetraoxide and nitrogen-doped honeycomb carbon composite negative electrode material. The trimanganese tetraoxide and nitrogen-doped honeycomb carbon composite material prepared by the preparation method has excellent cycle stability and rate performance as a lithium ion battery negative electrode material, the synthesis method is simple and controllable, the cost is low, and the material is expected to become a scaled conversion-type negative electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a trimanganese tetraoxide and nitrogen-doped honeycomb carbon composite negative electrode material. BACKGROUND

[0002] The existing graphite negative electrode of lithium ion batteries cannot meet the high power and high energy density requirements of electric vehicles and smart grid energy storage devices, so it is crucial to develop new advanced lithium ion battery negative electrode materials. Manganese-based oxides are one of the best choices to replace lithium ion battery graphite electrodes due to their high discharge capacity, suitable charge-discharge voltage platform, non-toxicity and natural abundance; manganese-based oxides mainly include MnO, Mn3O4, Mn2O3 and MnO2, and it is worth noting that the theoretical capacity of Mn3O4-based negative electrode material is higher than that of MnO, and the electrochemical reversibility is higher than that of Mn2O3 and MnO2, however, the large volume change and poor electrical conductivity during the cycle process will lead to poor cycle stability and rate capability of Mn3O4-based negative electrode material.

[0003] In order to solve these defects, scientists have proposed two effective solutions; reducing the particle size of the active material is an effective solution, which can reduce the lithium ion diffusion distance and alleviate the volume change during the cycle process. So far, a variety of nanostructured Mn3O4 negative electrode materials have been reported to improve cycle stability and rate capability. Combining Mn3O4 with carbon matrix to form a composite material is another effective strategy to achieve excellent electrochemical performance, which can further significantly alleviate the volume change during the charge-discharge process and speed up the transfer speed of electrons and lithium ions. Among various carbon matrices, nitrogen-doped honeycomb carbon is considered to be one of the best choices to combine with Mn3O4 due to its low cost and high electrochemical reaction kinetics. Obviously, combining the above two schemes, that is, preparing Mn3O4 nanoparticle / nitrogen-doped honeycomb carbon composite material can achieve excellent cycle stability and rate capability. However, the previously reported Mn3O4 nanoparticle / carbon composite materials have always been prepared by complex and uncontrollable synthesis methods, which limits its development and large-scale application, the preparation methods of the prior art are complex, not easy to control and high in cost, which is not conducive to large-scale production, and the products obtained by the prior art have poor cycle stability and rate performance.

[0004] Therefore, in view of the above status, it is urgent to develop a preparation method of a trimanganese tetraoxide and nitrogen-doped honeycomb carbon composite negative electrode material to overcome the deficiencies in current actual applications. SUMMARY

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a composite anode material of manganese tetroxide and nitrogen-doped honeycomb carbon, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a composite anode material of manganese tetroxide and nitrogen-doped honeycomb carbon includes the following steps:

[0008] S1: Dissolve polyacrylamide, urea and sodium chloride in deionized water, add manganese acetate tetrahydrate under stirring, and stir in a water bath until the solution volume is 30 mL.

[0009] S2: The solution obtained in step S1 is cooled in a refrigerator and then freeze-dried. The dried precursor is then calcined in an argon atmosphere.

[0010] S3: The product obtained in step S2 is washed and filtered with deionized water. The washed sample is dried in an oven to obtain a manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0011] As a further technical solution of the present invention, in step S1, the polyacrylamide is 1.0-1.4g, the urea is 0.1-0.3g, the sodium chloride is 1.0-3.0g, the deionized water is 40-80mL, the manganese acetate tetrahydrate is 0.4-0.8g, and the water bath temperature is 70-90℃.

[0012] As a further technical solution of the present invention, in step S2, the freeze-drying time is 24-72h, the calcination temperature is 500-800℃, and the calcination time is 0.5-4h.

[0013] As a further technical solution of the present invention, in step S3, the drying temperature of the oven is 40-100℃ and the drying time is 4-72h.

[0014] As a further technical solution of the present invention, in step S1, the mass ratio of manganese acetate tetrahydrate to polyacrylamide is 1:(1.25-3.5).

[0015] As a further technical solution of the present invention, the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material is a Mn3O4 and nitrogen-doped honeycomb carbon composite anode material.

[0016] A method for preparing lithium batteries using a manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material involves mixing the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material with 20% carbon black, then mixing it with an N-methylpyrrolidone solution containing 10% polyvinylidene fluoride. After stirring evenly, the mixture is coated onto copper foil and dried in an oven at 100°C for 4-24 hours. Electrode sheets are then cut out using a 12mm diameter slicer. In an argon-filled glove box, a coin cell is assembled using a lithium metal sheet as the counter electrode, a polypropylene porous membrane as the separator, and a 1mol / L lithium hexafluorophosphate mixed solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate as the electrolyte.

[0017] As a further technical solution of the present invention, the mass ratio of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material to polyvinylidene fluoride is 7:1, and the mass ratio of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material to carbon black is 7:2.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] This invention prepares a manganese tetroxide-nitrogen-doped honeycomb carbon composite anode material through a simple water bath stirring, freeze-drying, and calcination process. The entire operation is easy to control, low in cost, and suitable for industrial production. Compared with other manganese tetroxide composite materials, the manganese tetroxide-nitrogen-doped honeycomb carbon composite anode material prepared by this invention exhibits stronger interaction between the manganese tetroxide and nitrogen doped honeycomb carbon, smaller manganese tetroxide particle size, and better cycle stability. Furthermore, the manganese tetroxide-nitrogen-doped honeycomb carbon composite anode material prepared by this invention, when applied to the field of lithium-ion batteries, demonstrates excellent cycle stability and rate performance. This is of great significance for promoting the synthesis of manganese tetroxide and its application and development in lithium-ion batteries.

[0020] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0021] Figure 1 The flowchart illustrates the preparation method of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material provided in this embodiment of the invention.

[0022] Figure 2 XRD, Raman, nitrogen adsorption, and pore size distribution of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material provided in the embodiments of the present invention.

[0023] Figure 3 SEM, TEM, and HRTEM images of the manganese oxide and nitrogen-doped honeycomb carbon composite anode material provided in the embodiments of the present invention.

[0024] Figure 4 SEM, TEM, and HRTEM images of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material provided in the embodiments of the present invention.

[0025] Figure 5 The elemental distribution diagram of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material provided in the embodiments of the present invention is shown.

[0026] Figure 6 XPS spectrum of manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material provided in the embodiments of the present invention.

[0027] Figure 7 Electrochemical performance diagrams of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode materials and the manganese monoxide and nitrogen-doped honeycomb carbon composite anode materials provided in the embodiments of the present invention.

[0028] Figure 8 Electrochemical impedance spectroscopy and linear fitting diagrams of frequency versus impedance for manganese tetroxide and nitrogen-doped honeycomb carbon composite anode materials and manganese monoxide and nitrogen-doped honeycomb carbon composite anode materials provided in the embodiments of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0031] like Figure 1 As shown in the figure, the preparation method of a manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material provided by the present invention includes the following steps:

[0032] S1: Weigh 1.2g polyacrylamide, 2.0g sodium chloride and 0.2g urea and dissolve them in 60mL of deionized water. Add 0.6g manganese acetate tetrahydrate under stirring and stir in an 80℃ water bath until the solution volume is reduced to 30mL.

[0033] S2: The resulting mixed solution was cooled in a refrigerator and then freeze-dried for 48 hours. The dried precursor was then calcined at 600°C for 3 hours in an argon atmosphere.

[0034] S3: The calcined product was washed with deionized water and filtered. The washed sample was dried in an oven at 60°C for 10 hours to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0035] In a preferred embodiment of the present invention, the calcination temperature is 500-800℃ and the calcination time is 0.5-4h;

[0036] In a preferred embodiment of the present invention, the water bath temperature is 70-90℃;

[0037] In a preferred embodiment of the present invention, the drying temperature of the oven is 40-100℃ and the drying time is 4-72h;

[0038] In a preferred embodiment of the present invention, the freeze-drying time is 24-72 hours;

[0039] In a preferred embodiment of the present invention, the amount of polyacrylamide added is 1.0-1.4g, urea is 0.1-0.3g, sodium chloride is 1.0-3.0g, manganese acetate tetrahydrate is 0.4-0.8g, the mass ratio of polyacrylamide to manganese acetate tetrahydrate is 1:(1.25-3.5), and the amount of deionized water is 40-80mL.

[0040] In a preferred embodiment of the present invention, the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material is a Mn3O4 and nitrogen-doped honeycomb carbon composite anode material.

[0041] This invention provides a method for preparing a lithium-ion battery using a manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material. The method involves mixing the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material with 20% carbon black, then mixing it with an N-methylpyrrolidone solution containing 10% polyvinylidene fluoride. After stirring evenly, the mixture is coated onto copper foil and dried in an oven at 100°C for 4-24 hours. Electrode sheets are then cut using a 12mm diameter slicer. The electrodes are then transferred to an argon-filled glove box, using a lithium metal sheet as the counter electrode, a polypropylene porous membrane as the separator, and a 1 mol / L lithium hexafluorophosphate solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate as the electrolyte, to assemble a coin cell.

[0042] The mass ratio of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material to polyvinylidene fluoride is 7:1, and the mass ratio of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material to carbon black is 7:2.

[0043] like Figure 2 As shown, (a) is the XRD pattern, (b) is the Raman pattern, (c) is the nitrogen adsorption pattern, and (d) is the pore size distribution pattern.

[0044] like Figure 3 As shown, (a) and (b) are SEM images, (c) is a TEM image, and (d) is an HRTEM image.

[0045] like Figure 4As shown, (a), (b) and (c) are SEM images, (d) and (e) are TEM images, and (f) is an HRTEM image.

[0046] like Figure 6 As shown, (a) is the spectrum of the Mn 2p region, (b) is the spectrum of the C1s region, (c) is the spectrum of the N1s region, and (d) is the spectrum of the O1s region.

[0047] like Figure 8 As shown, (a) is the electrochemical impedance spectroscopy; (b) is the linear fitting graph of frequency versus impedance.

[0048] The application principle of the present invention will be further described below with reference to specific embodiments.

[0049] Example 1

[0050] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0051] like Figure 7 As shown, (a) is the CV curve; (b) is the voltage curve; (c) is the cycle performance and coulombic efficiency of the assembled lithium-ion battery at a current density of 100 mA / g in the voltage range of 3-0.01V; (d) is the rate performance at different current densities; and (e) is the cycle performance and coulombic efficiency at a current density of 1.0 A / g after 5 cycles of activation at a current density of 0.2 A / g.

[0052] The manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material prepared in this embodiment were assembled into a battery and subjected to charge-discharge tests. As can be seen from (c), its initial discharge capacity is 1356 mAh / g, its initial reversible capacity is 888 mAh / g, its first-cycle coulombic efficiency is 65%, and its cycle stability is good. As can be seen from (d), it still has a capacity of 472 mAh / g at a current density of 2000 mA / g, and its rate performance is very good. As can be seen from (e), it still exhibits good cycle performance at high current densities.

[0053] Example 2

[0054] Weigh 1.2g of polyacrylamide and 2.0g of sodium chloride and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcinate the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese oxide and nitrogen-doped honeycomb carbon composite anode material.

[0055] Results: The manganese suboxide and nitrogen-doped honeycomb carbon composite anode material prepared in this embodiment were assembled into a battery and subjected to charge-discharge tests. At a current density of 100 mA / g, the initial discharge capacity was 1251 mAh / g, and the discharge capacity was maintained at 775 mAh / g after 100 cycles. At a current density of 2000 mA / g, only 265 mAh / g of capacity was released.

[0056] Example 3

[0057] Weigh 1.0 g of polyacrylamide, 2.0 g of sodium chloride and 0.2 g of urea and dissolve them in 60 mL of deionized water. Add 0.6 g of manganese acetate tetrahydrate under stirring. Stir in an 80 °C water bath until the solution volume is reduced to 30 mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48 h. Calcinate the dried precursor at 600 °C for 3 h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60 °C oven for 10 h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0058] Example 4

[0059] Weigh 1.4g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0060] Example 5

[0061] Weigh 1.2g of polyacrylamide, 1.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0062] Example 6

[0063] Weigh 1.2g of polyacrylamide, 3.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0064] Example 7

[0065] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.1g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0066] Example 8

[0067] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.3g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0068] Example 9

[0069] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 40mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0070] Example 10

[0071] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 80mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in an oven at 60℃ for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0072] Example 11

[0073] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.4g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0074] Example 12

[0075] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.8g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0076] Example 13

[0077] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in a water bath at 70℃ until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in an oven at 60℃ for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0078] Example 14

[0079] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in a 90℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0080] Example 15

[0081] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 24h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0082] Example 16

[0083] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 72h. Calcine the dried precursor at 600℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0084] Example 17

[0085] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 700℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 60℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0086] Example 18

[0087] Weigh 1.2g of polyacrylamide, 2.0g of sodium chloride and 0.2g of urea and dissolve them in 60mL of deionized water. Add 0.6g of manganese acetate tetrahydrate under stirring. Stir in an 80℃ water bath until the solution volume is reduced to 30mL. Cool the resulting mixed solution in a refrigerator and freeze-dry for 48h. Calcine the dried precursor at 700℃ for 3h in an argon atmosphere. Wash the calcined product with deionized water and filter. Dry the washed sample in a 70℃ oven for 10h to obtain the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite anode material of manganese tetroxide and nitrogen-doped honeycomb carbon, characterized in that, Includes the following steps: S1: Dissolve polyacrylamide, urea, and sodium chloride in deionized water. Add manganese acetate tetrahydrate under stirring. Stir in a water bath until the solution volume is 30 mL. The dosages are: polyacrylamide 1.0-1.4 g, urea 0.1-0.3 g, sodium chloride 1.0-3.0 g, deionized water 40-80 mL, manganese acetate tetrahydrate 0.4-0.8 g, and water bath temperature 70-90℃. The mass ratio of manganese acetate tetrahydrate to polyacrylamide is 1:(1.25-3.5). S2: The solution obtained in step S1 is cooled in a refrigerator and then freeze-dried. The dried precursor is then calcined in an argon atmosphere for 24-72 hours, at a temperature of 500-800℃, and for 0.5-4 hours. S3: The product obtained in step S2 is washed and filtered with deionized water. The washed sample is dried in an oven to obtain a manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material. The drying temperature of the oven is 40-100℃ and the drying time is 4-72h.

2. A method for preparing a lithium battery, characterized in that, The manganese tetroxide and nitrogen-doped honeycomb carbon composite negative electrode material prepared by the preparation method described in claim 1 is mixed with 20% carbon black, and then mixed with an N-methylpyrrolidone solution containing 10% polyvinylidene fluoride. After stirring evenly, the mixture is coated onto copper foil and dried in an oven at 100°C for 4-24 hours. Then, electrode sheets are cut out using a 12mm diameter slicer. In an argon-filled glove box, a coin cell is assembled using a lithium metal sheet as the counter electrode, a polypropylene porous membrane as the separator, and a 1mol / L lithium hexafluorophosphate mixed solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate as the electrolyte.

3. The method for preparing a lithium battery according to claim 2, characterized in that, The mass ratio of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material to polyvinylidene fluoride is 7:1, and the mass ratio of the manganese tetroxide and nitrogen-doped honeycomb carbon composite anode material to carbon black is 7:2.

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