Neodymium-doped nickel oxide hollow metal oxide and its preparation method and application

Abstract

The present invention discloses a neodymium-doped nickel oxide hollow metal oxide and its preparation method and application. The material is a hollow nano-microsphere composed of neodymium-doped nickel oxide metal oxide nanoparticles, wherein the molar ratio of nickel to neodymium is (20-100):1. The method of the present invention synthesizes a neodymium-doped nickel oxide (Nd‑dop NiO) composite material with a nano-microsphere morphology composed of hollow metal oxide nanoparticles by improving the sol-gel method, comprising the steps of dissolution, solidification, and carbonization, so that the obtained material is a nano-microsphere composed of hollow nanoparticles, which has a large number of adsorption active sites and a large specific surface area, and can better anchor polysulfides in the positive electrode, serving as a sulfur species encapsulation skeleton and providing a conductive framework; at the same time, it has good catalytic activity, which is conducive to accelerating the conversion of polysulfides and enhancing reaction kinetics. The material of the present invention slows down the shuttle effect of polysulfides through the dual effects of adsorption and catalysis, thereby improving the utilization rate and cycle stability of sulfur.

Description

Background Art

[0001] Lithium-sulfur batteries have high energy density (2600Wh kg-1) and theoretical specific capacity (1675mAh g-1). Elemental sulfur is abundant in nature, inexpensive, and has low pollution. Therefore, lithium-sulfur batteries have been widely studied in the field of scientific research. However, lithium-sulfur batteries themselves have many problems, which directly hinder their commercial development. These problems can be divided into the following aspects: (1) the shuttle effect of polysulfides; (2) the insulation and low utilization rate of sulfur species; (3) volume expansion during discharge; (4) the growth of lithium dendrites. The energy density (180Wh kg-1) and theoretical specific capacity of existing commercial lithium batteries are both low, far from the energy density (2600Wh kg-1) and theoretical specific capacity (1675mAh g-1) of lithium-sulfur batteries. If the shuttle effect of lithium-sulfur batteries can be alleviated, the battery safety factor can be greatly improved, and the battery cycle performance and rate performance can be enhanced. This will be of great significance for the subsequent commercialization of lithium-sulfur batteries, greatly improving the development of new energy vehicles, and improving the endurance of vehicles.

[0002] Research has shown that adding electrocatalysts to the cathode of lithium-sulfur batteries can effectively mitigate the shuttling problem of polysulfides. For example, adding metal oxides, metal sulfides, metal phosphides, and carbon materials can reduce the dissolution of polysulfides in the electrolyte while promoting the deposition of lithium sulfide. However, a single catalytic effect does not achieve the desired catalytic oxidation efficiency for soluble polysulfides. Researching an electrocatalyst with both adsorption and catalytic effects could enhance the rapid conversion of polysulfides and reduce the shuttling effect of polysulfides.

[0003] Existing metal oxide-doped and modified electrocatalysts are primarily used in photocatalysis, electrocatalysis, sodium-ion batteries, and lithium-sulfur batteries. Existing production methods primarily rely on hydrothermal and sol-gel methods. These methods often produce dense, large particles that lack sufficient adsorption sites. Furthermore, the preparation process is complex and the raw material costs are high. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies in the prior art and provide a neodymium-doped nickel oxide hollow metal oxide and its preparation method and application. The hollow metal oxide has a rich pore structure and a high specific surface area, can serve as a sulfur species encapsulation skeleton, provide a conductive framework and more adsorption sites, and at the same time has good catalytic activity, which is beneficial to accelerate the conversion of polysulfides, enhance reaction kinetics, and slow down the shuttle effect of polysulfides through the dual effects of adsorption and catalysis, thereby improving sulfur utilization and cycle stability.

[0005] The neodymium-doped nickel oxide hollow metal oxide provided by the present invention is a hollow nano-microsphere composed of neodymium-doped nickel oxide metal oxide nanoparticles, wherein the molar ratio of nickel to neodymium is (20-100):1.

[0006] The preparation method of neodymium-doped nickel oxide hollow metal oxide (Nd-dop NiO) provided by the present invention comprises the following steps:

[0007] (1) Dissolution

[0008] A neodymium source, a nickel source and resorcinol are added to deionized water, wherein the amount of the neodymium source and the nickel source is measured according to a molar ratio of nickel to neodymium of (20-100):1, and the molar ratio of resorcinol to the total amount of nickel and neodymium is (20-100):1. After stirring and mixing evenly, an acid solution is added dropwise to adjust the pH value of the solution to 1, and the solution is heated to 60-90°C.

[0009] (2) Curing

[0010] Add formaldehyde solution dropwise to the solution heated to 60-90°C. The amount of formaldehyde solution used is based on the molar ratio of formaldehyde to resorcinol of (0.5-10):1. Stir until precipitation occurs and stop stirring. Keep warm until the solution is completely solidified to form a block, then keep warm at 70-90°C for 3 hours, and then dry in a drying oven.

[0011] (3) Carbonization

[0012] The dried block is placed in a muffle furnace, heated to 600-1000° C., and carbonized for 1-4 hours to obtain a neodymium-doped nickel oxide hollow metal oxide.

[0013] In the above method, the nickel source in step (1) is selected from one or more of nickel sulfate, nickel carbonate, nickel nitrate, and nickel chloride; and the neodymium source is selected from one or more of neodymium carbonate, neodymium nitrate, neodymium sulfate, and neodymium chloride.

[0014] In the above method, the acid solution in step (1) can be at least one of hydrochloric acid, acetic acid, nitric acid, sulfuric acid and carbonic acid; the hydrogen ion concentration in the acid solution is preferably 0.01 to 20 mol / L.

[0015] In the above method, the molar concentration of the formaldehyde solution in step (2) is 0.1 to 20 mol / L.

[0016] In the above method, the drying in step (2) is carried out in a drying oven at 50-70°C for 6-8 hours; and the heating rate in step (3) is 1-20°C / min.

[0017] The present invention also provides neodymium-doped nickel oxide hollow metal oxide prepared by the method.

[0018] The present invention also provides the use of the neodymium-doped nickel oxide hollow metal oxide in lithium-sulfur batteries. Furthermore, the application is as a modified material for lithium-sulfur battery cathode sheets. During the cathode sheet manufacturing process, the material acts as an electrocatalyst. Addition to the cathode sheet enhances the reaction kinetics of polysulfides and inhibits the shuttling effect of polysulfides.

[0019] The present invention also provides a positive electrode sheet modified by the neodymium-doped nickel oxide hollow metal oxide, wherein the neodymium-doped nickel oxide hollow metal oxide serves as an electrocatalyst.

[0020] The present invention also provides a method for preparing the above-mentioned neodymium-doped nickel oxide hollow metal oxide modified positive electrode sheet (Nd-dop NiO@S), comprising the following:

[0021] Neodymium-doped nickel oxide hollow metal oxide (Nd-dop NiO), carbon material, and sublimed sulfur are mixed in a mass ratio of the total mass of the neodymium-doped nickel oxide hollow metal oxide and the carbon material to the sublimed sulfur of 2:6, wherein the mass ratio of the neodymium-doped nickel oxide hollow metal oxide to the carbon material is (0.5-1.5):(0.5-1.5), and the total ratio is 2; the mixture is then wrapped in aluminum foil and placed in a reactor, and heat-melted at 140-160° C. for 6-10 hours; the heat-melted material, carbon material, and binder are then mixed in a molar ratio of (1-10):(1-10):1, a solvent is added and mixed to obtain a slurry, and the slurry is evenly coated on a positive electrode substrate material, and dried in an oven at 60-80° C. for 5-8 hours to obtain a hollow nano-microsphere modified positive electrode sheet composed of neodymium-doped nickel oxide (Nd-dop NiO) hollow metal oxide nanoparticles.

[0022] In the above-mentioned method for manufacturing a modified positive electrode sheet, the positive electrode base material may be at least one of carbon-coated aluminum foil, copper foil, and carbon cloth.

[0023] In the above-mentioned modified positive electrode sheet manufacturing method, the carbon material can be at least one of conductive carbon black, acetylene black, Ketjen carbon, activated carbon, carbon nanotubes, graphene, porous carbon and carbon nanofibers.

[0024] In the above-mentioned modified positive electrode sheet production method, the binder is preferably polyvinylidene fluoride. The binder polytetrafluoroethylene is usually commercially available in solution. When used in the present invention, the amount of the binder polytetrafluoroethylene is based on the mass of the polytetrafluoroethylene in the solution.

[0025] In the above-mentioned modified positive electrode sheet production method, the solvent is preferably one of N-methylpyrrolidone, dimethylformamide, and dimethylacetamide; the amount of the solvent is determined according to the required viscosity of the slurry, so as to form a uniform and stable slurry. Generally, the solvent is added at a solid-liquid mass ratio of (1 to 5):1.

[0026] In the above-mentioned method for manufacturing the modified positive electrode sheet, the method of uniformly applying the slurry on the positive electrode base material can be selected from one of spraying, doctor blade coating, coating roller and coating brush.

[0027] The present invention also provides a lithium-sulfur battery based on the above-mentioned neodymium-doped nickel oxide hollow metal oxide modified positive electrode sheet, wherein the lithium-sulfur battery is composed of the neodymium-doped nickel oxide hollow metal oxide modified positive electrode sheet, an ether electrolyte, a separator, a negative electrode and a battery shell.

[0028] The lithium-sulfur battery based on a neodymium-doped nickel oxide hollow metal oxide-modified positive electrode sheet is assembled by encapsulating the neodymium-doped nickel oxide hollow metal oxide-modified positive electrode sheet, an ether electrolyte, a separator, and a negative electrode in a battery case. During assembly, the modified positive electrode sheet is placed in the positive electrode case, followed by the ether electrolyte. The separator, negative electrode sheet, gasket, washer, and negative electrode case are then added in that order. Finally, the assembled battery is sealed using a battery sealing machine.

[0029] In the above-mentioned lithium-sulfur battery and its assembly method, the ether electrolyte is one of a mixed solution of lithium bis(trifluoromethanesulfonyl)imide, dioxolane ether ring, ethylene glycol dimethyl ether and lithium nitrate; the diaphragm is at least one of polypropylene, polyethylene, polyvinylidene fluoride-hexafluoropropylene copolymer and polypropylene-methyl methacrylate; and the negative electrode is a lithium sheet.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention synthesizes a neodymium-doped nickel oxide (Nd-dop NiO) composite material composed of hollow metal oxide nanoparticles in a nanospherical morphology by using an improved sol-gel method. These microspheres possess a rich porosity and numerous adsorption sites, resulting in a large specific surface area. These microspheres are able to better anchor polysulfides at the cathode, acting as an encapsulation framework for sulfur species and providing a conductive framework. Furthermore, their excellent catalytic activity accelerates polysulfide conversion and enhances reaction kinetics. The material described herein mitigates the shuttling effect of polysulfides through its dual adsorption-catalytic action, thereby improving sulfur utilization and cyclic stability.

[0032] 2. There are two commonly used methods for the traditional production of metal oxide doping: hydrothermal method and sol-gel method. The traditional hydrothermal method has a complicated production process and needs to be placed in a reactor for heating, which has a certain probability of explosion and poses a major safety hazard. The metal oxides produced by the traditional sol-gel method are mostly dense, large particles with small gaps, which are not conducive to the adsorption of polysulfides. The method of the present invention improves the production process and production materials, so that the obtained material is a nano-microsphere composed of hollow nanoparticles with a diameter of 100nm to 600nm. The microspheres have a large number of adsorption active sites and a large specific surface area, which can better adsorb polysulfides and inhibit the shuttle effect. In addition, the method has simple operation steps, low instrument requirements, and readily available raw materials, making it economical and affordable.

[0033] 3. The energy density (180Wh kg-1) and theoretical specific capacity of existing commercial lithium batteries are both low, far from the energy density (2600Wh kg-1) and theoretical specific capacity (1675mAh g-1) of lithium-sulfur batteries. The present invention greatly alleviates the shuttle effect of lithium-sulfur batteries, thereby significantly improving the battery safety factor. The use of the materials of the present invention in lithium-sulfur batteries significantly improves the electrochemical performance of the batteries, enhances the battery's cycle performance and rate performance, and paves the way for the subsequent commercialization of lithium-sulfur batteries. The commercialization of lithium-sulfur batteries can greatly promote the development of new energy vehicles, and the endurance of vehicles will be greatly improved. At the same time, they can also be applied to various aspects such as mobile phones, electronic toys, and digital products, achieving a significant improvement in energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the XRD characterization pattern of Nd-dop NiO prepared in Example 1;

[0035] Figure 2 is a SEM characterization image of Nd-dop NiO prepared in Example 1;

[0036] Figure 3 TEM characterization images of Nd-dop NiO prepared in Example 1 (Ⅰ: 111 crystal plane of Nd-dop NiO, Ⅱ: 220 crystal plane of Nd-dop NiO, Ⅲ: 200 crystal plane of Nd-dop NiO);

[0037] Figure 4 is the cyclic voltammetry curve of the symmetrical battery assembled with different materials in Example 1;

[0038] Figure 5 is the first cyclic voltammetry curve of the lithium-sulfur battery assembled with different materials in Example 1;

[0039] Figure 6is a rate performance diagram of lithium-sulfur batteries assembled with different materials at room temperature in Example 1;

[0040] Figure 7 is a cycle performance diagram of lithium-sulfur batteries assembled with different materials at room temperature in Example 1;

[0041] Figure 8 Isothermal adsorption-desorption curves of hollow metal oxides with different nickel-neodymium molar ratios;

[0042] Figure 9 The pore size distribution curves of hollow metal oxides with different nickel-neodymium molar ratios. DETAILED DESCRIPTION

[0043] The present invention is further described below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Based on the above-mentioned invention, those skilled in the art may make some non-essential improvements and adjustments to the present invention for specific implementation, which still fall within the scope of protection of the invention.

[0044] Implementation 1

[0045] Preparation of hollow metal oxide neodymium doped nickel oxide (Nd-dop NiO) composite materials:

[0046] (1) Dissolution: Dissolve 1.5 g of resorcinol, 0.2 mmol of NiNO3·6H2O and Nd(NO3)·6H2O with a Ni:Nd molar ratio of 20:1 in 12.5 ml of deionized water. After stirring and mixing, add 60 μL of 11.9 mol / L hydrochloric acid dropwise to adjust the pH of the solution to 1. Heat the solution in an oil bath to 80°C.

[0047] (2) Curing: Add 2 mL of formaldehyde solution to a solution heated to 80°C. The molar concentration of the formaldehyde solution is 1.22 mol / L. Continue stirring until precipitation occurs. Stop stirring. The precipitation will gradually form a block material. Then keep it at 80°C for 3 hours. Then keep it at 60°C in a drying oven for 6 hours to obtain a fluffy and dry block.

[0048] (3) Carbonization: The dried bulk sample was carbonized in a muffle furnace at 700°C for 3 h with a heating rate of 5°C / min. After the insulation, the sample was cooled to room temperature and the sample was taken out to obtain a neodymium-doped nickel oxide hollow metal oxide.

[0049] Figure 1This is an XRD pattern of the prepared neodymium-doped nickel oxide (Nd-dop NiO) composite material. The XRD pattern shows all diffraction peaks consistent with typical layered transition metal oxides, with no impurity peaks observed. This indicates that the prepared neodymium-doped nickel oxide (Nd-dop NiO) has an ideal structure with a space group of Fm3m. Figure 2 SEM and Figure 3 The TEM image shows that the prepared neodymium-doped nickel oxide hollow metal oxide is a hollow nano-microsphere morphology composed of metal oxide nanoparticles, and the diameter of the microsphere is 100nm to 500nm.

[0050] Preparation of neodymium-doped nickel oxide-modified hollow metal oxide cathode (Nd-dop NiO@S):

[0051] The prepared neodymium-doped nickel oxide hollow metal oxide Nd-dop NiO powder, acetylene black, and sulfur were weighed and mixed in a mass ratio of 1:1:6 and ground evenly. The resulting mixture was placed in a sealed container and heated to 155°C for 8 hours to obtain a Nd-dop NiO@S composite. The Nd-dop NiO@S composite, graphene, and polyvinylidene fluoride binder were ground and mixed evenly in a mass ratio of 6:3:1, and then an appropriate amount of N-methylpyrrolidone solvent was added and ground for 0.5 hours. Thereafter, the above-mentioned evenly dispersed slurry was evenly coated on a carbon-coated aluminum foil with a scraper, and then dried at 60°C and cooled to room temperature to obtain a Nd-dop NiO@S positive electrode.

[0052] Assembling Nd-dop NiO@S lithium-sulfur battery:

[0053] Use Nd-dop NiO@S as the positive electrode, lithium sheet as the negative electrode, and polypropylene membrane Celgard 2500 as the separator. Place the modified positive electrode sheet in the positive electrode shell, and add 20-35ul ether electrolyte. The electrolyte composition is DME / DOL (V:V = 1:1) and contains 1MLiTFSI and 2wt% LiNO3; then add the separator, negative electrode sheet, gasket, washer, and negative electrode shell in sequence. Finally, seal the assembled battery with a battery sealing machine.

[0054] Example 2: Regulating the doping ratio to improve catalytic effect

[0055] Electrochemical measurements were performed on lithium-sulfur batteries assembled with different doping ratios. Neodymium-doped nickel oxide (Nd-dop NiO) composite materials were prepared according to the method of Example 1, with molar ratios of Ni:Nd = 20:1, Ni:Nd = 30:1, Ni:Nd = 40:1, and Ni:Nd = 50:1. Lithium-sulfur batteries were assembled using these materials and their electrochemical performance was tested. Lithium-sulfur batteries assembled with positive electrodes made of NiO and Nd2O3 served as a control group.

[0056] In order to verify the catalytic performance of Nd-dop NiO, neodymium-doped nickel oxide hollow metal oxides were assembled into a symmetrical cell as follows:

[0057] The prepared Nd-dop NiO powder, acetylene black, and polyvinylidene fluoride binder were weighed and mixed in a mass ratio of 6:3:1. The mixture was manually ground in an agate mortar for 10 minutes. An appropriate amount of N-methylpyrrolidone solvent was then added and ground for another 10 minutes to obtain a viscous slurry. The resulting slurry was coated onto a carbon cloth with a doctor blade and then placed in a constant temperature drying oven at 60°C for 8 hours. The resulting electrode was punched into 12 mm diameter discs using a punch. Symmetrical cells were then assembled using the discs as electrode materials, Celgard 2500 as the separator, and the electrolyte composition was DME / DOL (V:V = 1:1) containing 1 M LiTFSI and 0.2 M Li2S6.

[0058] Only the doping ratio was changed, and neodymium-doped nickel oxide (Nd-dop NiO) composite materials were prepared according to the method of Example 1 according to the molar ratios of Ni:Nd=20:1, Ni:Nd=30:1, Ni:Nd=40:1, and Ni:Nd=50:1, respectively. Symmetrical batteries were assembled according to the same method, and the electrochemical properties of the batteries were tested.

[0059] A symmetric cell assembled with NiO and Nd2O3 served as a control. NiO and Nd2O3 powders were mixed with polyvinylidene fluoride and acetylene black ene binder in a mass ratio of 6:3:1. The mixture was manually ground in an agate mortar for 10 minutes. An appropriate amount of N-methylpyrrolidone solvent was then added and ground for 10 minutes to produce a viscous slurry. The resulting slurry was applied to a carbon cloth using a spatula and then placed in a constant temperature drying oven at 60°C for 8 hours. The resulting electrode was punched into 12 mm diameter discs using a punch. A symmetric cell was then assembled using the discs as electrode materials, Celgard 2500 as the separator, and the electrolyte composition was DME / DOL (V:V = 1:1) containing 1 M LiTFSI and 0.2 M Li2S6.

[0060] The cyclic voltammetry curves of different symmetrical batteries were tested respectively, and the results are as follows Figure 4 As shown in the figure, it can be seen that when the hollow metal oxide molar ratio Ni:Nd=30:1, the symmetrical cell assembled has a strong redox peak and the largest response current. At the same time, the response current of the hollow metal oxides with other nickel-neodymium ratios is also greater than the response current of the comparative NiO and Nd2O3 symmetrical cells. This shows that the neodymium-doped nickel oxide Nd-dop NiO prepared by the present invention has a better catalytic conversion effect on Li2S6.

[0061] Figure 5The first cyclic voltammetry curves of lithium-sulfur batteries assembled with different materials. Figure 7 It can be seen that the lithium-sulfur battery assembled when Ni:Nd=30:1 in the neodymium-doped nickel oxide hollow metal oxide has the largest redox peak and the smallest voltage polarization. The redox peaks of samples with other nickel-neodymium ratios are smaller than that of Ni:Nd=30:1, and the voltage polarization is also relatively larger. However, the redox peaks of the doped materials are larger than those of NiO and Nd2O3, and the polarization is smaller than that of NiO and Nd2O3. This proves that the neodymium-doped nickel oxide hollow metal oxide described in the present invention has a catalytic effect on the redox conversion of polysulfides.

[0062] Figure 6 The cycling performance diagram of lithium-sulfur batteries assembled with different materials at room temperature. Figure 6 It can be seen that the best rate performance is shown when Ni:Nd=30:1 in neodymium-doped nickel oxide hollow metal oxide Nd-dop NiO. Even at high rates of 4C and 6C (1C=1675mA g-1), the positive electrode with Ni:Nd=30:1 still maintains a high specific capacity of 616mAhg-1 and 546mAh g-1, respectively. At a rate of 6C, other doping ratios also show higher specific capacities, namely Ni:Nd=20:1, 230mAh g-1, Ni:Nd=40:1, 397mAh g-1, and Ni:Nd=50:1, 133mAh g-1, all of which are higher than NiO (87mAhg-1) and Nd2O3 (43mAh g-1).

[0063] Figure 7 Figure 2 shows the cycling performance of lithium-sulfur batteries assembled with different materials at room temperature. After 100 cycles, the specific capacity of the Ni:Nd = 30:1 cathode reached 819.91 mAh g-1, with a corresponding capacity retention rate of 98.29%. This is higher than the specific capacity of the Ni:Nd = 20:1 cathode (708.11 mAh g-1), the Ni:Nd = 40:1 cathode (768.36 mAh g-1), the Ni:Nd = 50:1 cathode (626 mAh g-1), and the comparative NiO (594.35 mAh g-1) and Nd2O3 (482.35 mAh g-1) cathodes.

[0064] Figure 8 Isothermal adsorption-desorption curves for hollow metal oxides with varying nickel-neodymium molar ratios. Using N₂ as the adsorption target, the curves for the neodymium-doped nickel oxide (Nd-dop NiO) and the comparative nickel oxide and neodymium oxide samples all exhibit typical Type III curves, but the adsorption efficiency of the Nd-dop NiO prepared by the present invention is significantly better than that of the comparative samples.

[0065] Figure 9The pore size distribution curves of hollow metal oxides with different nickel-neodymium molar ratios are shown in Figure 2. As can be seen from the curve, the pore size of the prepared material is mainly 2 to 10 nm, which is within the mesopore range (0 to 2 nm is micropore, 2 nm to 50 nm is mesopore, and larger than 50 nm is macropore). According to Brunaue-Emmett-Teller BET calculations, the specific surface area of ​​the prepared hollow Nd-dop NiO is higher than that of NiO and Nd2O3, which are 11.5 and 11.1 m 2 g -1 、10.418m 2 g -1 、6.55m 2 g -1 The larger specific surface area of ​​the hollow metal oxide prepared by the present invention can provide more adsorption sites, which is more conducive to the adsorption of polysulfides. The mesopores can accommodate more sulfur active substances, improve the utilization rate of sulfur, and thus alleviate the shuttle effect of polysulfides.

Claims

1. A neodymium-doped nickel oxide hollow metal oxide, characterized in that: Hollow nanospheres composed of neodymium-doped nickel oxide metal oxide nanoparticles, wherein the molar ratio of nickel to neodymium in the neodymium-doped nickel oxide metal oxide is (20-100):1; the neodymium-doped nickel oxide hollow metal oxide is prepared by the following method: (1) Dissolution Add a neodymium source, a nickel source, and resorcinol to deionized water, wherein the neodymium source and the nickel source are measured so that the molar ratio of nickel to neodymium is (20-100):1, and the molar ratio of resorcinol to the total amount of nickel and neodymium is (20-100):

1. After stirring and mixing, add an acid solution dropwise to adjust the pH value of the solution to 1, and heat to 60-90°C. (2) Curing Add formaldehyde solution dropwise to the solution heated to 60-90°C. The amount of formaldehyde solution used is based on a molar ratio of formaldehyde to resorcinol of (0.5-10):

1. Stir until precipitation occurs, then stop stirring. Keep warm until the solution is completely solidified to form a block. Then keep warm at 70-90°C for 3 hours and then dry in a drying oven. (3) Carbonization The dried block is placed in a muffle furnace, heated to 600-1000° C. and carbonized for 1-4 hours to obtain a neodymium-doped nickel oxide hollow metal oxide.

2. A method for preparing neodymium-doped nickel oxide hollow metal oxide, characterized in that: The following steps are involved: (1) Dissolution Add a neodymium source, a nickel source, and resorcinol to deionized water, wherein the neodymium source and the nickel source are measured so that the molar ratio of nickel to neodymium is (20-100):1, the nickel source is selected from one or more of nickel sulfate, nickel carbonate, nickel nitrate, and nickel chloride; the neodymium source is selected from one or more of neodymium carbonate, neodymium nitrate, neodymium sulfate, and neodymium chloride, and the molar ratio of resorcinol to the total amount of nickel and neodymium is (20-100):

1. After stirring and mixing, an acid solution is added dropwise to adjust the pH of the solution to 1, and the solution is heated to 60-90°C. (2) Curing Add formaldehyde solution dropwise to the solution heated to 60-90°C. The amount of formaldehyde solution used is based on a molar ratio of formaldehyde to resorcinol of (0.5-10):

1. Stir until precipitation occurs, then stop stirring. Keep warm until the solution is completely solidified to form a block. Then keep warm at 70-90°C for 3 hours and then dry in a drying oven. (3) Carbonization The dried block is placed in a muffle furnace, heated to 600-1000° C. and carbonized for 1-4 hours to obtain a neodymium-doped nickel oxide hollow metal oxide.

3. The method according to claim 2, characterized in that The acid solution in step (1) may be at least one of hydrochloric acid, acetic acid, nitric acid, sulfuric acid and carbonic acid; the hydrogen ion concentration in the acid solution is 0.01 to 20 mol / L; and the molar concentration of the formaldehyde solution in step (2) is 0.1 to 20 mol / L.

4. The method according to claim 2, characterized in that The drying in step (2) is carried out in a drying oven at 50-70°C for 6-8 hours; the heating rate in step (3) is 1-20°C / min.

5. Use of the neodymium-doped nickel oxide hollow metal oxide according to claim 1 in lithium-sulfur batteries.

6. The positive electrode sheet modified with the neodymium-doped nickel oxide hollow metal oxide according to claim 1, characterized in that: Neodymium-doped nickel oxide hollow metal oxide as electrocatalyst.

7. The method for manufacturing the positive electrode sheet modified with the neodymium-doped nickel oxide hollow metal oxide according to claim 6, characterized in that: Includes the following: Neodymium-doped nickel oxide hollow metal oxide, carbon material, and sublimed sulfur are mixed in a mass ratio of the total mass of the neodymium-doped nickel oxide hollow metal oxide and the carbon material to the sublimed sulfur of 2:6, wherein the mass ratio of the neodymium-doped nickel oxide hollow metal oxide to the carbon material is (0.5~1.5):(0.5~1.5), and the total ratio is 2; then the mixture is wrapped in aluminum foil and placed in a reactor, and heat-melted at 140~160°C for 6~10 hours; then the hot-melted material, carbon material, and binder are mixed uniformly in a molar ratio of (1~10):(1~10):1, a solvent is added and mixed uniformly to obtain a slurry, and then the slurry is evenly coated on a positive electrode substrate material, and dried in an oven at 60~80°C for 5~8 hours to obtain a hollow nano-microsphere modified positive electrode sheet composed of neodymium-doped nickel oxide hollow metal oxide nanoparticles.

8. The method according to claim 7, characterized in that: The positive electrode matrix material is at least one of carbon-coated aluminum foil, copper foil, and carbon cloth; the carbon material is at least one of conductive carbon black, acetylene black, Ketjen carbon, activated carbon, carbon nanotubes, graphene, porous carbon, and carbon nanofibers; and the binder is polyvinylidene fluoride.

9. A lithium-sulfur battery based on the neodymium-doped nickel oxide hollow metal oxide modified positive electrode sheet according to claim 6, wherein the lithium-sulfur battery comprises a neodymium-doped nickel oxide hollow metal oxide modified positive electrode sheet, an ether electrolyte, a separator, a negative electrode and a battery shell.

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