Molybdenum disulfide modified lithium-rich manganese-based positive electrode material rich in sulfur vacancies and preparation method thereof

Abstract

The invention discloses a sulfur vacancy-rich molybdenum disulfide modified lithium-rich manganese-based positive electrode material and a preparation method thereof, and relates to the technical field of lithium ion battery positive electrode materials, the preparation method comprises the following steps: (1) preparing a lithium-rich manganese-based positive electrode material; (2) reacting the transition metal sulfide with hydrogen peroxide to obtain a defect-rich two-dimensional material; and (3) mixing the defect-rich two-dimensional material with the lithium-rich manganese-based positive electrode material, and sintering at a certain temperature to obtain the sulfur vacancy-rich molybdenum disulfide modified lithium-rich manganese-based positive electrode material. According to the invention, the surface of the lithium-rich manganese-based positive electrode material is coated with the molybdenum disulfide nanosheet rich in sulfur vacancies, so that an interface protection layer with both a physical barrier and chemical activity is constructed. According to the design, interface side reaction and lattice oxygen evolution can be effectively inhibited, and charge distribution and ion transmission are optimized by utilizing sulfur vacancies. Through the synergistic effect of surface coating and defect engineering, the first-week coulombic efficiency, the rate capability and the cycling stability of the material are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery cathode materials, and particularly relates to a sulfur vacancy-rich molybdenum disulfide modified lithium-rich manganese-based cathode material and a preparation method thereof. BACKGROUND

[0002] Developing high-energy-density lithium ion batteries is of great significance for promoting the development of sustainable energy and solving the problems of global warming and energy crisis. At present, the upper limit of the energy density of the cathode material has become a technical breakthrough point for the comprehensive application of green energy. Lithium-rich layered oxides are considered to be one of the potential cathode materials for the next generation of high-energy lithium batteries, which not only have economic advantages brought by abundant manganese ore, but also have high theoretical energy density brought by anion redox activation. However, the low initial coulombic efficiency, poor cycle performance and rate performance of the lithium-rich manganese-based cathode material seriously hinder its commercialization. These shortcomings are mainly caused by the low electrical conductivity of the Li2MnO3 phase in the material, the slow lithium ion diffusion caused by the formation of the cathode electrolyte interface layer due to the side reaction, and the crystal structure phase change of itself.

[0003] To address the above challenges, researchers have tried various modification strategies, and the core goal of these strategies is usually to simultaneously improve the electronic / ion conductivity of the material, inhibit the irreversible release of lattice oxygen, and stabilize the material-electrolyte interface through surface coating, bulk doping or structure design, so as to fundamentally improve its initial coulombic efficiency, rate performance and cycle life. For example, patent CN120072912A discloses a “lithium-rich manganese-based cathode material coated with molybdenum disulfide and lithium lanthanum niobium oxide and a preparation method thereof”, which realizes the double uniform coating of molybdenum disulfide and lithium lanthanum niobium oxide on the surface of the lithium-rich manganese-based cathode material by combining freeze-drying and calcination technology. This double coating layer aims to serve as a stable protective layer to prevent the cathode material from being eroded, and to optimize the electrochemical performance by utilizing the physical and electrochemical compatibility between molybdenum and niobium, two adjacent elements in the same period, and to avoid the “deoxidation” phenomenon. However, this scheme has its limitations: first, the coating components are complex, involving two different coating materials (MoS2 and LLNO), and the process flow is relatively complicated; secondly, and more importantly, the molybdenum disulfide used is of intrinsic structure, and the electronic structure is not precisely controlled through defect engineering, so the improvement of the intrinsic conductivity of the material is limited, and the catalytic activity of the coating layer is not fully utilized to stabilize the anion redox reaction.

[0004] Defect engineering, as an efficient material modification strategy, can effectively regulate the charge distribution of materials, improve conductivity, and construct more electrochemically active sites by introducing defects, thus significantly enhancing the electrochemical energy storage performance and showing broad application prospects in the field of energy conversion and storage. Two-dimensional materials, such as graphitic carbon nitride, MXene, graphene, transition metal dichalcogenides (TMDs), etc., have unique advantages in energy materials due to their high modulus, large specific surface area, and adjustable interfacial properties. It is worth noting that there is a natural synergistic effect between defect engineering and two-dimensional materials: on the one hand, the structural characteristics of two-dimensional materials provide an ideal carrier for the construction and distribution of defects; on the other hand, the introduction of defects can further optimize the electronic structure of two-dimensional materials, enhance ion transport kinetics, and fully release their potential in electrochemical energy storage and conversion.

[0005] Therefore, to overcome the deficiencies of the existing technology, the present invention uses a more simple process to develop a modified lithium-rich manganese-based cathode material with sulfur vacancies in two-dimensional molybdenum disulfide by intrinsically modifying molybdenum disulfide, a two-dimensional material, in order to more effectively solve the inherent problems of lithium-rich manganese-based cathode materials. Summary of the Invention

[0006] The purpose of the present invention is to provide a lithium-rich manganese-based cathode material modified with molybdenum disulfide rich in sulfur vacancies and a preparation method thereof. By designing a mixture of molybdenum disulfide rich in sulfur vacancies and a lithium-rich manganese-based cathode material, the basal plane of the molybdenum disulfide nanosheets with a defective crystal structure is covered with catalytic sites, having a large number of surface active sites and excellent conductivity. When coated on the surface of the lithium-rich material, it greatly prevents the side reaction between the lithium-rich material and the electrolyte and restricts the escape of oxygen. This modification strategy mainly synergistically uses two methods, namely coating and defect engineering, to significantly improve the first-cycle Coulombic efficiency, cycle stability, and rate performance of the material. The goal of the present invention is to develop a new cathode material with excellent performance, simple process, and controllable cost to meet the application requirements of the next-generation high-energy-density lithium-ion batteries.

[0007] To achieve the above object of the present invention, the following technical solutions are specifically adopted: In the first aspect, the present invention provides a lithium-rich manganese-based cathode material modified with molybdenum disulfide rich in sulfur vacancies, which consists of a lithium-rich manganese-based cathode material core and a layer of molybdenum disulfide rich in sulfur vacancies coated on its surface.

[0008] The lithium-rich manganese-based cathode material has a layered-layered composite structure, and its general formula is xLi2MnO3·(1 - x)LiMO2, where x is a molar coefficient and 0 < x < 1; M is a transition metal element selected from one or more of Ni, Co, and Mn.

[0009] The coating material is molybdenum disulfide rich in sulfur vacancies, and its chemical formula is VS -MoS2. This material is a two-dimensional nanosheet layer structure, and new charge distribution and a large number of high active sites are formed on the basal plane due to the presence of sulfur vacancies.

[0010] In a second aspect, the present application provides a preparation method of a lithium-rich manganese-based positive electrode material modified by sulfur vacancy-rich molybdenum disulfide, comprising the following steps: (1) preparing a lithium-rich manganese-based positive electrode material; (2) reacting molybdenum disulfide with hydrogen peroxide to obtain sulfur vacancy-rich molybdenum disulfide; (3) mixing the sulfur vacancy-rich molybdenum disulfide with the lithium-rich manganese-based positive electrode material, and sintering to obtain a lithium-rich manganese-based positive electrode material modified by sulfur vacancy-rich molybdenum disulfide.

[0011] By effectively introducing bulk defects in the molybdenum disulfide through a chemical exfoliation method, sulfur vacancy-rich molybdenum disulfide is obtained, and new charge distribution is formed to adjust the electronic structure and surface activity thereof.

[0012] In the step (1), the specific preparation steps of the lithium-rich manganese-based positive electrode material include: mixing a transition metal hydroxide precursor with a lithium source, pre-sintering at 400-700°C in air for 4-7h, and then high-temperature calcining at 700-900°C for 13-16 hours to obtain the lithium-rich manganese-based positive electrode material.

[0013] In the step (2), the specific preparation steps of the sulfur vacancy-rich molybdenum disulfide include: (2.1) dissolving thiourea and a molybdenum source in deionized water, transferring the solution to a polytetrafluoroethylene-lined stainless steel autoclave after the solid is completely dissolved, hydrothermal treatment at a certain temperature, taking out the solid after cooling to room temperature, washing with deionized water and alcohol three times respectively, centrifuging and vacuum drying overnight to obtain MoS2; (2.2) taking a certain amount of MoS2, N-methyl pyrrolidone (NMP) and H2O2 in a round-bottom flask, and stirring in a water bath at a certain temperature with a magnetic stirrer; (2.3) filtering the solution after water bath stirring, and collecting the organic filter membrane; (2.4) placing the filter membrane in a beaker, adding an appropriate amount of alcohol for ultrasonic treatment, then collecting the solution after ultrasonic treatment into a quartz culture dish, and finally drying it in a freeze dryer; (2.5) after the alcohol is completely volatilized, the material on the culture dish is scraped off and collected, and then placed in a vacuum drying oven for drying to obtain sulfur vacancy-rich molybdenum disulfide.

[0014] Optionally, in the step (2.1), the molybdenum source is selected from one or more of sodium molybdate or ammonium paramolybdate; The molar ratio of the molybdenum source to the thiourea is 1:2-1:4, the hydrothermal temperature is 150-200 DEG C, the hydrothermal time is 8-15h, the centrifugal rotation speed is 8000-12000r / min, and the drying temperature is 60-90 DEG C.

[0015] Optionally, in the step (2.1), the thiourea, the molybdenum source and the phosphorus source are dissolved in deionized water, the phosphorus source can be sodium hypophosphite monohydrate, and the doping amount of phosphorus in the molybdenum disulfide is 0.3-0.9%.

[0016] Optionally, in the step (2.2), the volume / mass ratio of H2O2 to MoS2 is 1:2.5-1:4 L / g, the volume / mass ratio of N-methyl pyrrolidone to MoS2 is 1:1-1:2 L / g, the water bath temperature is 30-50 DEG C, and the stirring time is 8-12h.

[0017] In the step (2.5), the temperature of vacuum drying is 60-90 DEG C, and the drying time is 20-30h.

[0018] In the step (3), the mass percentage of the molybdenum disulfide rich in sulfur vacancies in the lithium-rich manganese-based positive electrode material is 0.5-5%, preferably 0.5-2%.

[0019] In the step (3), the sintering temperature is 400-700 DEG C, the sintering atmosphere is air, the heating rate is 3 DEG C / min, and the sintering time is 4-7h.

[0020] In a third aspect, the application provides a lithium ion battery, which comprises a positive electrode, a negative electrode and an electrolyte, and the positive electrode comprises the lithium-rich manganese-based positive electrode material.

[0021] Advantages: 1. The two-dimensional material molybdenum disulfide (MoS2) selected in the application is a common transition metal chalcogenide (TMDs), which has great application value in the field of high-performance devices due to its unique physical and electrical characteristics, such as adjustable band gap, high electron mobility, etc., and becomes a favorable candidate material for replacing noble metals to promote catalytic reactions.

[0022] 2. The non-metallic doped MoS2 selected in the application has great potential in improving structural stability. Since the phosphorus (P) atom has low electronegativity and additional valence electrons, when it replaces the S atom, it can enhance the electron supply to the adjacent Mo site, fine-tune the Mo-S bond strength, and promote the transformation of MoS2 from semiconductor 2H phase to metallic 1T phase, thereby improving the electrical conductivity and charge transfer dynamics.

[0023] 3、The application introduces bulk defects in MoS2 by a chemical stripping method to break the original charge balance and form a new charge distribution to adjust the electronic structure and surface activity of MoS2, so as to optimize its conductivity.

[0024] 4、The application mixes the sulfur vacancy-rich molybdenum disulfide and the lithium-rich manganese-based positive electrode material to obtain the sulfur vacancy-rich molybdenum disulfide modified lithium-rich manganese-based positive electrode material, which has excellent conductivity, and the defect molybdenum disulfide is coated on the surface of the lithium-rich material, thereby enhancing the lithium ion transmission rate and improving the rate performance and cycle stability of the lithium ion battery.

[0025] 5、The application assembles the modified lithium-rich manganese-based positive electrode material into a battery, and after modification, the coating on the surface of the lithium-rich material greatly prevents the side reaction of the electrolyte and limits the escape of oxygen.

[0026] 6、The application has the advantages of simple process, short process cycle and low cost, and can be widely used in lithium ion batteries.

[0027] The application has been described in detail in the foregoing, but the above-mentioned embodiments are only illustrative in nature and are not intended to limit the application. In addition, the present application is not limited by any theory described in the foregoing prior art or the application content or the examples described below. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The preparation method flow chart of the lithium-rich manganese-based positive electrode material is an embodiment of the application; Figure 2 The EPR spectrum of the sulfur vacancy-rich molybdenum disulfide prepared in Example 1 is shown in the figure. Figure 3 The first cycle charge-discharge curve of the lithium ion battery prepared in Example 1 is shown in the figure. DETAILED DESCRIPTION

[0029] The application will be further described below in conjunction with examples, and it should be noted that the following examples are provided only for illustrative purposes and do not constitute a limitation on the scope of protection required by the application.

[0030] Unless otherwise specified, the raw materials, reagents, methods and the like used in the examples are conventional raw materials, reagents and methods in the art.

[0031] An embodiment of the application provides a preparation method of a sulfur vacancy-rich molybdenum disulfide modified lithium-rich manganese-based positive electrode material, as shown in the figure, which can specifically include the following steps: Figure 1 Step S100, preparation of a lithium-rich manganese-based positive electrode material. Mix the transition metal hydroxide precursor with a lithium source, first pre-burn in air, and then calcine at high temperature to obtain the lithium-rich manganese-based positive electrode material.​

[0032] Step S200: Preparation of molybdenum disulfide rich in sulfur vacancies. First, thiourea and a molybdenum source are dissolved in deionized water. After the solid is completely dissolved, the solution is transferred to a stainless steel autoclave lined with polytetrafluoroethylene and hydrothermally heated at a certain temperature. After cooling to room temperature, the solid is removed, washed three times each with deionized water and alcohol, centrifuged, and vacuum dried overnight to obtain MoS2. Next, a certain amount of MoS2, NMP, and H2O2 are placed in a round-bottom flask and stirred in a water bath at a certain temperature using a magnetic stirrer. The solution after water bath stirring is filtered, and the organic filter membrane is collected. Then, the material on the filter membrane is collected in a quartz petri dish with alcohol and placed in the freezer at -20°C for 24 hours. After that, it is quickly transferred to a freeze dryer. Finally, after the alcohol has completely evaporated, the solution is removed, and the material on the petri dish is scraped off and collected. It is then placed in a vacuum drying oven and dried to obtain molybdenum disulfide rich in sulfur vacancies.

[0033] Step S300: Molybdenum disulfide rich in sulfur vacancies is mixed with lithium-rich manganese-based cathode material in a specific mass percentage and sintered at a certain temperature to obtain lithium-rich manganese-based cathode material modified with molybdenum disulfide rich in sulfur vacancies.

[0034] Example 1: (1) Weigh 1.025 mol of lithium-rich manganese-based precursor Mn 4 / 6 Ni 1 / 6 Co 1 / 6 (OH)2 and 0.64 mol Li2CO3 were mixed. The raw materials were placed in a crucible and then in a muffle furnace. Under an air atmosphere, the mixture was first pre-sintered at 450℃ for 6 h, and then sintered at 920℃ for 16 h at a heating rate of 5℃ / min. After cooling to room temperature, the lithium-rich manganese-based cathode material 0.5Li2MnO3·0.5Li(Ni)2 was obtained. 1 / 3 Co 1 / 3 Mn 1 / 3 )O2.

[0035] (2) Dissolve 18 mmol thiourea and 6 mmol ammonium molybdate in deionized water. After the solid is completely dissolved, transfer the solution to a stainless steel autoclave lined with polytetrafluoroethylene and hydrothermally heat it at 180°C for 12 hours. After cooling to room temperature, take out the solid and wash it three times each with deionized water and alcohol. Centrifuge it at 10,000 rpm for five minutes. After the solid has no odor, vacuum dry it at 80°C overnight to obtain MoS2.

[0036] (3) First, take 200 mg MoS2, 150 mL NMP and 50 mL H2O2 into a round-bottom flask and stir with a magnetic stirrer in a water bath at 40 °C for 12 h. Next, filter the solution after water bath stirring and collect the organic filter membrane. Then, repeat the above operation ten times, collect the material on the filter membrane with alcohol into a quartz petri dish, and then place it in the freezer compartment of a -20 °C freezer for 24 h. After freezing, quickly place it in a freeze dryer. Finally, until the alcohol has completely evaporated, take it out, scrape off the material on the petri dish and collect it, and place it in a vacuum drying oven at 60 °C for 24 h. Perform electron paramagnetic resonance (EPR) testing on the dried material, such as... Figure 2 As shown, V S -MoS2 exhibits a significant signal intensity at the g=2.005 position, which can be attributed to the unpairing of Mo-S electrons at the coordinated unsaturated sulfur defect site. (This is in contrast to V...) S Compared to -MoS2, MoS2 has a very weak signal intensity, and the peak intensity is positively correlated with the defect concentration, which proves that molybdenum disulfide rich in sulfur vacancies was successfully prepared.

[0037] (4) Weigh 200g of lithium-rich manganese-based cathode material and mix it with 2g of molybdenum disulfide rich in sulfur vacancies (accounting for 1wt% of the lithium-rich material), and sinter at 550℃ for 6h to obtain lithium-rich manganese-based cathode material modified with molybdenum disulfide rich in sulfur vacancies.

[0038] Example 2: The preparation method of the modified lithium-rich cathode material in this embodiment is basically the same as that in Example 1. The difference is that the amounts of NMP and H2O2 in step (2) are 120 mL and 80 mL, respectively, while the other conditions remain the same.

[0039] Example 3: The preparation method of the modified lithium-rich cathode material in this embodiment is basically the same as that in Example 1. The difference is that the amounts of NMP and H2O2 in step (2) are 130 mL and 70 mL, respectively, while the other conditions remain the same.

[0040] Example 4: The preparation method of the modified lithium-rich cathode material in this embodiment is basically the same as that in Example 1. The difference is that the amounts of NMP and H2O2 in step (2) are 140 mL and 60 mL, respectively, while the other conditions remain the same.

[0041] Example 5: The preparation method of the modified lithium-rich cathode material in this embodiment is basically the same as that in Example 1. The difference is that in step (3), the mass of molybdenum disulfide rich in sulfur vacancies accounts for 0.5% of the lithium-rich cathode material, and the other conditions remain the same.

[0042] Example 6: The preparation method of the modified lithium-rich cathode material in this embodiment is basically the same as that in Example 1. The difference is that in step (3), the mass of molybdenum disulfide rich in sulfur vacancies accounts for 2% of the lithium-rich cathode material, and the other conditions remain the same.

[0043] Example 7: The preparation method of the modified lithium-rich cathode material in this embodiment is basically the same as that in Example 1. The difference is that in step (3), the mass of molybdenum disulfide rich in sulfur vacancies accounts for 2.5% of the lithium-rich cathode material, and the other conditions remain the same.

[0044] Example 8: The preparation method of the modified lithium-rich cathode material in this embodiment is basically the same as that in Example 1. The difference is that in step (2), 6 mmol of ammonium molybdate, 18 mmol of thiourea and 0.2 mmol of sodium hypophosphite monohydrate are dissolved in deionized water, and the other conditions are kept the same, so that MoS2 with a mass ratio of 0.3% P can be obtained.

[0045] Example 9: The preparation method of the modified lithium-rich cathode material in this embodiment is basically the same as that in Example 1. The difference is that in step (2), 6 mmol of ammonium molybdate, 18 mmol of thiourea and 0.3 mmol of sodium hypophosphite monohydrate are dissolved in deionized water, and the other conditions are kept the same, so that MoS2 with a mass ratio of 0.6% P can be obtained.

[0046] Example 10: The preparation method of the modified lithium-rich cathode material in this embodiment is basically the same as that in Example 1. The difference is that in step (2), 6 mmol of ammonium molybdate, 18 mmol of thiourea and 0.35 mmol of sodium hypophosphite monohydrate are dissolved in deionized water, and the other conditions are kept the same, so that MoS2 with a mass ratio of 0.9% P can be obtained.

[0047] Comparative Example 1: The lithium-rich cathode material was prepared by mixing according to the same steps as in Example 1 (1), without any other treatment of the material.

[0048] Comparative Example 2: The lithium-rich cathode material was prepared by mixing according to the same steps as in step (1) of Example 1; Molybdenum disulfide at a mass percentage of 1% was mixed with lithium-rich manganese-based cathode material and sintered at 550℃ for 6 hours to obtain molybdenum disulfide modified lithium-rich manganese-based cathode material.

[0049] This comparative example did not involve any modification treatment of molybdenum disulfide.

[0050] Battery manufacturing: The cathode materials prepared in the above examples and comparative examples were assembled into a liquid half-cell. The assembly method was as follows: the prepared lithium-rich cathode material or modified lithium-rich cathode material, conductive agent Super-P, and binder PVDF were added to NMP solvent in a ratio of 8:1:1 and mixed evenly to obtain a slurry. The obtained slurry was then coated, dried, stamped, and rolled to obtain a cathode sheet. The stainless steel shell of the coin cell, the cathode sheet, the PP separator, and the lithium sheet were stacked in sequence, a certain amount of electrolyte was added, and then the cells were sealed and allowed to stand to form a half-cell.

[0051] The assembled battery was placed in a LAND2001CT battery test chamber at 25℃ for charge and discharge testing. First, it was activated for three cycles at a voltage of 2.0-4.6V, and then a 0.1-2C rate test was performed at a voltage of 2.5-4.45V. The results of the first week of charge and discharge testing are shown in Table 1.

[0052] Table 1

[0053] As shown in Table 1, the present invention modifies lithium-rich manganese-based cathode materials by performing defect engineering on molybdenum disulfide and using it for coating, which can effectively and significantly improve the first-cycle coulombic efficiency.

[0054] Specifically, both parallel technical paths were successful: in the sulfur vacancy introduction path, Example 3 achieved a peak first-cycle coulombic efficiency of 89.11% under optimized conditions; in the phosphorus doping path, Example 9 (0.6% P doping) also achieved an excellent level of 88.43%. Both were significantly higher than the unmodified Comparative Example 1 (81.93%) and Comparative Example 2 (83.02%) which only used intrinsic molybdenum disulfide coating. This collectively confirms that defect manipulation of the coating layer to optimize its electronic structure is key to improving performance. Further parameter influence analysis shows that achieving optimal performance depends on precise control of key process parameters. In the sulfur vacancy path, there are clear optimal windows for both H2O2 dosage (Examples 1-4) and coating amount (Examples 1, 5-7), and the parameter combination represented by Example 3 can most effectively construct active defects. In the phosphorus doping path, there is also an optimal value for the doping amount (Example 9), and too high or too low (Examples 8, 10) will lead to a drop in efficiency.

[0055] The assembled batteries were placed in a LAND2001CT battery test chamber at 60℃ for charge and discharge testing. A 1C rate test was conducted under a voltage range of 2.5-4.45V. The battery cycle test results are shown in Table 2.

[0056] Table 2

[0057] Table 2 shows the cycling performance test results, further verifying the improvement effect of the modification strategy of this invention on the long-term cycling stability of the material. After 200 cycles at 1C rate, Example 3 still showed the best capacity retention rate, reaching 86.7%, with an initial discharge specific capacity of 240 mAh / g and a capacity of 208.1 mAh / g after 200 cycles, demonstrating excellent structural and interface stability. The capacity retention rates of all modified examples (Examples 1-8) were significantly higher than those of the comparative examples. Among them, Example 1, with a 1% coating amount, also showed good cycling performance (86.0%), while excessively high coating amounts (such as Example 7, 2.5%) led to a decrease in cycling performance, indicating that excessive coating may hinder lithium-ion transport kinetics. It is worth noting that the examples (8-10) based on the phosphorus doping path also showed better cycling stability than the comparative examples. Among them, Example 9 (0.6% P doping) achieved a capacity retention rate of 84.9% and had the highest initial discharge capacity (243 mAh / g), which provides another effective dimension for the regulation of material performance. Data demonstrates that the strategy of obtaining a sulfur-vacancy-rich molybdenum disulfide coating layer through precise control, as well as P-doping modification, can effectively suppress interfacial side reactions and structural degradation during cycling, thereby significantly improving the long-term cycle life of lithium-rich manganese-based cathode materials.

[0058] In summary, this invention has successfully achieved synergistic optimization of the surface structure and interfacial chemistry of lithium-rich manganese-based materials by precisely controlling the sulfur vacancy concentration and coating amount, or by introducing P doping, providing an effective way to solve problems such as low initial efficiency and poor cycle stability.

[0059] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A lithium-rich manganese-based cathode material modified with sulfur-vacancy molybdenum disulfide, characterized in that, It consists of a core of a lithium-rich manganese-based cathode material and a molybdenum disulfide layer rich in sulfur vacancies coated on its surface.

2. The lithium-rich manganese-based cathode material modified with sulfur-vacancy molybdenum disulfide according to claim 1, characterized in that, The lithium-rich manganese-based cathode material has a layered-layered composite structure with the general formula xLi2MnO3·(1-x)LiMO2, where x is a molar coefficient and 0 < x < 1; M is a transition metal element selected from one or more of Ni, Co, and Mn.

3. A method for preparing a lithium-rich manganese-based cathode material modified with sulfur-vacancy molybdenum disulfide as described in claim 1 or 2, characterized in that, It includes the following steps: (1) Prepare a lithium-rich manganese-based cathode material; (2) React molybdenum disulfide with hydrogen peroxide to obtain molybdenum disulfide rich in sulfur vacancies; (3) Mix the molybdenum disulfide rich in sulfur vacancies with the lithium-rich manganese-based cathode material, and after sintering, obtain a lithium-rich manganese-based cathode material modified with molybdenum disulfide rich in sulfur vacancies.

4. The preparation method according to claim 3, characterized in that, In the step (1), the specific preparation steps of the lithium-rich manganese-based cathode material include: mixing a transition metal hydroxide precursor with a lithium source, pre-calcining in air at 400 - 700 °C for 4 - 7 h, and then high-temperature calcining at 700 - 900 °C for 13 - 16 hours to obtain the lithium-rich manganese-based cathode material.

5. The preparation method according to claim 3, characterized in that, In the step (2), the specific preparation steps of the molybdenum disulfide rich in sulfur vacancies include: (2.1) Dissolve thiourea and a molybdenum source in deionized water. After the solid is completely dissolved, transfer the solution to a stainless-steel autoclave with a polytetrafluoroethylene inner lining, hydrothermalize at a certain temperature, take out the solid after cooling to room temperature, wash it three times with deionized water and alcohol respectively, centrifuge, and vacuum dry overnight to obtain MoS2; (2.2) Take a certain amount of MoS2, N-methylpyrrolidone (NMP), and H2O2 in a round-bottom flask, and perform water bath stirring with a magnetic stirrer at a certain temperature; (2.3) Filter the solution after water bath stirring and collect the organic filter membrane; (2.4) Put the filter membrane into a beaker, add an appropriate amount of alcohol for ultrasonic treatment, then collect the ultrasonic-treated solution into a quartz petri dish, and finally dry it in a freeze dryer; (2.5) Take it out after the alcohol has completely volatilized, scrape and collect the material on the petri dish, place it in a vacuum drying oven, and after drying, obtain the molybdenum disulfide rich in sulfur vacancies.

6. The preparation method according to claim 5, characterized in that, In the step (2.1), the molybdenum source is selected from one or several of sodium molybdate or ammonium paramolybdate; The molar ratio of the molybdenum source to thiourea is 1:2 - 1:4, the hydrothermal temperature is 150 - 200 °C, the hydrothermal time is 8 - 15 h, the centrifugation speed is 8000 - 12000 revolutions per minute, and the drying temperature is 60 - 90 °C.

7. The preparation method according to claim 5, characterized in that, In the step (2.1), dissolve thiourea, the molybdenum source, and a phosphorus source in deionized water, and the doping amount of phosphorus element in molybdenum disulfide is 0.3 - 0.9%.

8. The preparation method according to claim 3, characterized in that, In the step (2.2), the volume-mass ratio of H2O2 to MoS2 is 1:2.5 - 1:4 L / g, and the volume-mass ratio of N-methylpyrrolidone to MoS2 is 1:1 - 1:2 L / g; the water bath temperature is 30 - 50 °C, and the stirring time is 8 - 12 h.

9. The preparation method according to claim 3, characterized in that, In the step (3), the mass percentage of the molybdenum disulfide rich in sulfur vacancies in the lithium-rich manganese-based cathode material is 0.5 - 5%, preferably 0.5 - 2%; In step (3), the sintering temperature is 400-700℃, the sintering atmosphere is air, and the sintering time is 4-7h.

10. A lithium-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode comprises the lithium-rich manganese-based positive electrode material modified with sulfur vacancy molybdenum disulfide as described in claim 1 or 2, or the lithium-rich manganese-based positive electrode material modified with sulfur vacancy molybdenum disulfide as described in any one of claims 3-9.

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