A method for preparing a modified lithium-rich manganese-based single crystal material

Abstract

The present invention discloses a method for preparing a modified lithium-rich manganese-based single crystal material. The present invention uses alumina heterogeneous nucleation as the core to prepare a lithium-rich manganese-based precursor by a co-precipitation method, then reacts with a concentrated alkali solution, dries the powder, and crushes the powder to prepare a lithium-rich manganese-based single crystal precursor; titanium tetrachloride vapor and hydrogen sulfide gas are mixed and heated to react, and titanium disulfide crystals are collected on the cooling wall, and then a soluble salt is added to the titanium disulfide dispersion, stirred, and the lamellar structure of titanium disulfide is restricted to the structure of the salt by heating, the solvent is volatilized, water is added to dissolve the salt, and titanium disulfide with a lamellar structure is obtained by filtration; finally, the lithium-rich manganese-based single crystal precursor, lithium salt, and lamellar titanium disulfide are mixed and sintered to obtain the material. The modified lithium-rich manganese-based single crystal material prepared by this method has a structurally stable single crystal morphology, excellent electronic conductivity and ionic conductivity, so the material has excellent rate, capacity and cycle stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of positive electrode materials, and in particular relates to a method for preparing a modified lithium-rich manganese-based single crystal material. Background Art

[0002] Lithium-ion batteries are widely used in various fields due to their lightweight, high energy density, lack of memory effect, long cycle life, and environmental friendliness. With the development of the times, there is an increasing demand for higher-capacity and safer lithium-ion batteries. Lithium-rich manganese-based cathode materials are considered the most promising next-generation lithium-ion battery cathode materials due to their ultra-high discharge capacity (>250 mAh / g), low cost, non-toxicity, and high thermal stability.

[0003] The biggest problems with lithium-rich manganese-based cathode materials at present are: 1. Low initial efficiency (about 75%); 2. Significant voltage and capacity decay during the cycle; 3. Poor cycle and rate performance. Among them, the initial efficiency can be increased to 85% or even 90% through surface coating modification or special surface activation processes. The rapid voltage and capacity decay during the cycle is mainly due to the electrochemical side reactions between the material and the electrolyte caused by high voltage, and the fragmentation, pulverization and detachment of the agglomerate particles during the cycle, which exposes the fresh internal surface and continues to react with the electrolyte, resulting in the formation of other phases, causing the degradation of electrical performance. This is mainly because the current mainstream lithium-rich manganese-based laminated cathode materials have a morphology of micron-sized secondary spherical particles formed by the agglomeration of primary particles of several hundred nanometers. The material with this secondary spherical particle morphology has low mechanical strength and poor firmness. Under high compaction conditions, these secondary spherical particles are easily squeezed and crushed, resulting in the exposure of particles inside the material, increased side reactions and metal ion dissolution, and a decrease in electrochemical performance. Furthermore, the primary particles are too small and contain numerous structural defects, making them prone to structural collapse under high-voltage charge and discharge. Furthermore, the secondary spheres are unable to encapsulate these extremely fine particles, making it difficult to suppress interfacial side reactions during high-voltage charge and discharge, leading to structural damage. Furthermore, the secondary spheres are prone to causing safety issues such as flatulence. The material's low ion diffusion capacity also results in relatively poor rate performance. Summary of the Invention

[0004] In view of the defects of the prior art, the object of the present invention is to provide a lamellar structured titanium disulfide coated modified lithium-rich manganese-based single crystal material and a preparation method thereof.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A lamellar structured titanium disulfide coated modified lithium-rich manganese-based single crystal material, wherein the chemical formula of the lithium-rich manganese-based single crystal material is xLi2MnO3·(1-x)LiNi aCo b Mn c O2, where 0<x<1, 0<a<1, 0<b<1, 0<c<0.1, a+b+c=1.

[0007] The method for preparing the titanium disulfide-coated modified lithium-rich manganese-based single crystal material of the above-mentioned lamellar structure comprises the following steps:

[0008] S1. Obtaining lithium-rich manganese-based single crystal precursor:

[0009] A nickel source, a cobalt source, and a manganese source are weighed in a stoichiometric ratio and dissolved in deionized water to obtain a mixed metal salt solution; nano-alumina particles and a surfactant are added to the mixed salt solution and stirred to disperse; after the nano-alumina particles are stably dispersed, a precipitant and a complexing agent are added to the solution to obtain a lithium-rich manganese-based precursor having the nano-alumina particles as a heterogeneous core through co-precipitation; the lithium-rich manganese-based precursor is then immersed in a strong alkaline solution, and after the reaction is complete, the precursor is filtered, washed, dried, and crushed by ball milling to obtain a lithium-rich manganese-based single crystal precursor;

[0010] S2. Obtaining lamellar titanium disulfide:

[0011] Titanium tetrachloride is vaporized and mixed with hydrogen disulfide gas and heated, and the product is introduced into an organic solvent through a hot air flow to prepare a titanium disulfide organic dispersion; a water-soluble salt is uniformly dispersed in the titanium disulfide organic dispersion, the temperature is raised to 120-200°C, and the temperature is maintained for 0.5-6 hours, the solvent is evaporated, and deionized water is added. After thorough stirring, the mixture is filtered and dried to obtain a lamellar titanium disulfide;

[0012] S3. The lithium-rich manganese-based single crystal precursor, lamellar titanium disulfide, and lithium salt are mixed, and sintered to obtain a lamellar titanium disulfide-coated modified lithium-rich manganese-based single crystal material.

[0013] In the above method, the order of S1 and S2 is not important.

[0014] In the above method S1, the nickel source is at least one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride; the cobalt source is at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, and cobalt chloride; and the manganese source is at least one of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride.

[0015] In the above method S1, the concentration of the mixed metal salt solution is 0.5 to 2.0 mol / L, specifically 1.5 mol / L. According to an embodiment of the present invention, the molar ratio of nickel ions in the nickel salt, cobalt ions in the cobalt salt, and manganese ions in the manganese salt is 1.5:1.5:6 or 2:1:5.5 or 1.8:2.1:4.1.

[0016] In the above method S1, the particle size of the nano-alumina particles is 20-80 nm; the amount of the nano-alumina particles added is 1 / 100-1 / 10 of the volume of the mixed metal salt solution, specifically 2 / 25, 1 / 20 or 1 / 50.

[0017] In the above method S1, the surfactant is at least one of benzenesulfonyl hydrazide, sodium lauryl sulfate, and fatty alcohol polyoxyethylene ether sodium sulfate; the added amount of the surfactant is 3 / 1000 to 1 / 100 of the volume of the mixed metal salt solution, specifically 1 / 125, 1 / 200 or 1 / 250.

[0018] In the above method S1, the precipitant is at least one of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, and ammonium bicarbonate, and the precipitant is added in the form of an aqueous solution of the precipitant, and the concentration of the aqueous solution of the precipitant is 0.8~2.3 mol / L, specifically 1.5 mol / L, 1.0 mol / L, or 12.2 mol / L; the complexing agent is at least one of citric acid, oxalic acid, and tartaric acid, and the complexing agent is added in the form of an aqueous solution of the complexing agent, and the concentration of the complexing agent is 1.2~2.8 mol / L, specifically 2.6 mol / L, 2.0 mol / L, or 1.5 mol / L.

[0019] In method S1, the strong base solution is at least one of an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, or an alcoholic sodium hydroxide solution (NaOH / C2H5OH). The concentration of the strong base solution is 0.5 to 5.0 mol / L, specifically 2.0 mol / L, 3.0 mol / L, or 4.0 mol / L.

[0020] In the above method S2, the titanium tetrachloride is gasified and mixed with hydrogen disulfide gas in a volume ratio of 1:2; and the heating temperature is 480-540°C.

[0021] In the above method S2, the organic solvent is at least one of ethylene glycol phenyl ether, benzyl alcohol, isophorone, methyl benzoate, sulfolane, diphenyl ether, and glycerol.

[0022] In the above method S2, the molar concentration of the titanium disulfide organic dispersion is 0.05-0.35 mol / L, specifically 0.1 mol / L, 0.2 mol / L or 0.3 mol / L.

[0023] In the above method S2, the water-soluble salt is at least one of cubic sodium chloride, potassium chloride, calcium chloride, alum, cesium chloride, ammonium chloride and hexagonal zinc chloride, aluminum chloride and magnesium chloride.

[0024] In the above method S2, the molar ratio of the water-soluble salt to the titanium disulfide in the titanium disulfide organic dispersion is (0.15-0.35):1, specifically 0.15:1, 0.2:1 or 0.3:1.

[0025] In the above method S2, the heating program of heating is to increase the temperature to the target temperature at a heating rate of 0.5-2.0°C / min.

[0026] In the above method S3, the molar ratio of the lithium-rich manganese-based single crystal precursor, the lamellar titanium disulfide and the lithium source is 1:(0.002~0.01):(1.1~1.3), specifically 1:0.008:1.15, 1:0.004:1.20 or 1:0.006:1.25; wherein the lithium source includes at least one of the following: lithium hydroxide and lithium carbonate.

[0027] In the above method S3, the sintering process parameters include: heating to 300-600°C at 1-3°C / min and keeping warm for 6-8 hours, then heating to 850-950°C at 3-6°C / min and keeping warm for 24-36 hours.

[0028] The present invention also protects a lithium ion battery.

[0029] The lithium-ion battery comprises a positive electrode and a negative electrode, and the material of the positive electrode comprises the lithium-rich manganese-based single crystal material coated with titanium disulfide and modified in the above-mentioned lamellar structure.

[0030] The technical effects and advantages of the present invention are as follows:

[0031] 1. This invention uses a co-precipitation method to prepare a lithium-rich manganese-based precursor using alumina as a heterogeneous nucleation core. Because alumina is an amphoteric oxide, it dissolves after a strong alkaline immersion reaction, forming a void in the center of the lithium-rich manganese-based precursor. This method results in a relatively fragile structure. Ball milling can then separate micron-sized secondary particles (primary particle agglomerates) into nanometer-sized primary particles, achieving single crystallization of the precursor.

[0032] 2. The present invention prepares lamellar titanium disulfide using a soluble salt with a consistent crystal geometry as a template, such as cubic sodium chloride, potassium chloride, and calcium chloride, and hexagonal zinc chloride, aluminum chloride, and magnesium chloride. First, the soluble salt is insoluble in a high-melting-point organic solvent, allowing it to serve as a template to constrain the growth of the titanium disulfide lamellar structure. The soluble salt dissolves in water, yielding the lamellar titanium disulfide. This preparation method is simple, operates under mild conditions, and produces titanium disulfide with a well-defined lamellar structure and high purity.

[0033] Therefore, the lithium-rich manganese-based material prepared by the present invention has a structurally stable single crystal morphology, and the titanium disulfide with a lamellar structure has excellent electron transport performance and can provide abundant transmission channels for lithium ions. Its coating on the surface of the lithium-rich manganese-based single crystal material can, on the one hand, improve the electronic conductivity and ionic conductivity of the material and improve the rate performance of the material; on the other hand, the coating layer can also enhance the mechanical strength of the material and can isolate the direct contact between the electrolyte and the matrix material to the greatest extent, thereby reducing the probability of side reactions and improving the stability and cycle life of the material.

[0034] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the lithium-rich manganese-based single crystal precursor prepared in Example 1;

[0036] Figure 2 Schematic diagram of the lamellar structure of titanium disulfide prepared in Example 1. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for understanding and reading by those familiar with this technology, and are not used to limit the conditions for implementation of the present invention. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose that can be achieved by the present invention. At the same time, terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0039] The present invention discloses a method for preparing a titanium disulfide-coated, modified lithium-rich manganese-based single crystal material with a lamellar structure, the method comprising:

[0040] 1. Obtain lithium-rich manganese-based single crystal precursor;

[0041] Specifically include:

[0042] 1.1 Weigh a nickel source, a cobalt source, and a manganese source in a stoichiometric ratio (0 < a < 1, 0 < b < 1, 0 < c < 0.1, a + b + c = 1) and dissolve them in deionized water to obtain a mixed metal salt solution; wherein the nickel source is at least one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride; the cobalt source is at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, and cobalt chloride; and the manganese source is at least one of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride; and the concentration of the mixed metal salt solution is 0.5 to 2.0 mol / L;

[0043] 1.2 Add nano-alumina particles and surfactant to the mixed salt solution and stir to disperse;

[0044] The nano-alumina particles are 20-80 nm in size, and the amount of the nano-alumina particles added is 1 / 100-1 / 10 of the volume of the mixed metal salt solution. The surfactant is at least one of benzenesulfonyl hydrazide, sodium lauryl sulfate, and sodium fatty alcohol polyoxyethylene ether sulfate, and the amount of the surfactant added is 3 / 1000-1 / 100 of the volume of the mixed metal salt solution.

[0045] 1.3 After the nano-alumina particles are dispersed and stabilized, a precipitant and a complexing agent are added to the solution to obtain a lithium-rich manganese-based precursor with nano-alumina particles as a heterogeneous core through co-precipitation;

[0046] The precipitant is an aqueous solution of at least one of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, and ammonium bicarbonate; the concentration of the precipitant is 0.8 to 2.3 mol / L; the complexing agent is at least one of citric acid, oxalic acid, and tartaric acid; the concentration of the complexing agent is 1.2 to 2.8 mol / L;

[0047] 1.4 The lithium-rich manganese-based precursor prepared above is immersed in a strong alkaline solution. After the reaction is complete, it is filtered, washed, dried, and crushed by ball milling to obtain a lithium-rich manganese-based single crystal precursor.

[0048] The strong alkaline solution is at least one of an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, or an alcoholic sodium hydroxide solution (NaOH / C2H5OH). The concentration of the strong alkaline solution is 0.5 to 5.0 mol / L.

[0049] 2. Obtaining titanium disulfide with a lamellar structure:

[0050] 2.1 Titanium tetrachloride is vaporized and mixed with hydrogen disulfide gas in a volume ratio of 1:2 and heated, and the product is introduced into an organic solvent by a hot air flow to prepare a titanium disulfide organic dispersion;

[0051] The heating temperature is 480-540° C. The organic solvent is at least one of ethylene glycol phenyl ether, benzyl alcohol, isophorone, methyl benzoate, sulfolane, diphenyl ether, and glycerol.

[0052] Wherein, the molar concentration of the titanium disulfide organic dispersion is 0.05-0.35 mol / L;

[0053] 2.2 Disperse the water-soluble salt evenly in the titanium disulfide organic dispersion, heat it to 120~200℃, and keep it warm for 0.5~6h.

[0054] The water-soluble salt is at least one of cubic sodium chloride, potassium chloride, calcium chloride, alum, cesium chloride, ammonium chloride and hexagonal zinc chloride, aluminum chloride and magnesium chloride.

[0055] Wherein, the molar ratio of the water-soluble salt to titanium disulfide is (0.15~0.35):1.

[0056] The temperature rise program is to increase the temperature to the target temperature at a rate of 0.5-2.0°C / min.

[0057] 2.3 Evaporate the solvent, add deionized water, stir thoroughly, filter, and dry to obtain titanium disulfide with a lamellar structure.

[0058] 3. The lithium-rich manganese-based single crystal precursor, lamellar titanium disulfide, and lithium salt are mixed, and sintered to obtain a lamellar titanium disulfide-coated modified lithium-rich manganese-based single crystal material.

[0059] The molar ratio of the lithium-rich manganese-based single crystal precursor, the lamellar titanium disulfide and the lithium source is 1:(0.002-0.01):(1.1-1.3); and the lithium source is at least one of lithium hydroxide and lithium carbonate.

[0060] The sintering process parameters include: heating to 300-600°C at 1-3°C / min and keeping warm for 6-8 hours, then heating to 850-950°C at 3-6°C / min and keeping warm for 24-36 hours.

[0061] The present invention also provides a lithium-rich manganese-based single crystal material, wherein the chemical formula of the lithium-rich manganese-based positive electrode material is xLi2MnO3·(1-x)LiNi a Co b Mn c O2, where 0<x<1, 0<a<1, 0<b<1, 0<c<0.1, a+b+c=1.

[0062] In order to better understand the present invention, examples and comparative examples are provided below.

[0063] Example 1

[0064] A method for preparing a lamellar titanium disulfide-coated, modified lithium-rich manganese-based single crystal material comprises the following steps: S1. Nickel chloride, cobalt chloride, and manganese chloride are weighed in a molar ratio of 1.5:1.5:6 and dissolved in deionized water to prepare a 1.5 mol / L mixed metal salt solution. Nanoalumina particles (45 nm in diameter) at a volume of 1 / 20th the volume of the mixed salt solution and benzenesulfonyl hydrazide at a volume of 1 / 200th the volume of the mixed metal salt solution are added to the mixed salt solution. After the nanoalumina particles are dispersed and stabilized, sodium carbonate at a concentration of 1.5 mol / L and tartaric acid at a concentration of 2.0 mol / L are added to obtain a lithium-rich manganese-based precursor with the nanoalumina particles as a heterogeneous core by coprecipitation. The obtained lithium-rich manganese-based precursor is immersed in a 4.0 mol / L sodium hydroxide solution. After the reaction is complete, the precursor is filtered, washed, dried, and then ball-milled to obtain a lithium-rich manganese-based single crystal precursor.

[0065] S2. Titanium tetrachloride is vaporized and mixed with hydrogen disulfide gas in a 1:2 volume ratio. The mixture is heated at 500°C. The resulting mixture is then introduced into isophorone via a hot stream to prepare a 0.2 mol / L titanium disulfide organic dispersion. Aluminum chloride is weighed at a molar ratio of 0.2 to titanium disulfide and evenly dispersed in the titanium disulfide organic dispersion. The temperature is then raised to 160°C at a rate of 0.8°C / min and maintained for 4 hours. The solvent is evaporated, and deionized water is added. The mixture is thoroughly stirred, filtered, and dried to obtain a lamellar titanium disulfide.

[0066] S3. Weigh a lithium-rich manganese-based single crystal precursor, lamellar titanium disulfide, and lithium hydroxide in a molar ratio of 1:0.008:1.15, mix them evenly, heat them to 450°C at a rate of 1°C / min, and keep them warm for 6 hours. Then, heat them to 900°C at a rate of 3.5°C / min and keep them warm for 28 hours for sintering to obtain a lithium-rich manganese-based single crystal material coated with lamellar titanium disulfide.

[0067] Comparative Example 1

[0068] A method for preparing a titanium disulfide-coated modified lithium-rich manganese-based positive electrode material, the specific steps are as follows:

[0069] S1. Nickel chloride, cobalt chloride, and manganese chloride were weighed in a molar ratio of 1.5:1.5:6 and dissolved in deionized water to prepare a 1.5 mol / L mixed metal salt solution. 1.5 mol / L sodium carbonate and 2.0 mol / L tartaric acid were added to obtain a lithium-rich manganese-based precursor by coprecipitation.

[0070] S2. Weigh a lithium-rich manganese-based precursor, titanium disulfide, and lithium hydroxide in a molar ratio of 1:0.008:1.15, mix them evenly, heat them to 400°C at 1°C / min, keep them warm for 6 hours, then heat them to 900°C at 3.5°C / min, and keep them warm for 28 hours for sintering to obtain a titanium disulfide-coated modified lithium-rich manganese-based positive electrode material.

[0071] Example 2

[0072] A method for preparing a lamellar structured titanium disulfide-coated modified lithium-rich manganese-based single crystal material, comprising the following specific steps:

[0073] S1. Nickel chloride, cobalt chloride, and manganese chloride were weighed at a molar ratio of 1.5:1.5:6 and dissolved in deionized water to prepare a 0.8 mol / L mixed metal salt solution. Nanoalumina particles (50 nm in diameter) at a volume of 1 / 50 of the mixed salt solution and sodium lauryl sulfate at a volume of 1 / 250 of the mixed metal salt solution were added to the mixed salt solution. After the nanoalumina particles were dispersed and stabilized, sodium carbonate at a concentration of 1.0 mol / L and tartaric acid at a concentration of 1.5 mol / L were added to coprecipitate a lithium-rich manganese-based precursor with the nanoalumina particles as the heterogeneous core. The obtained lithium-rich manganese-based precursor was immersed in a 2.0 mol / L sodium hydroxide solution. After the reaction was complete, the precursor was filtered, washed, dried, and crushed by ball milling to obtain a lithium-rich manganese-based single crystal precursor.

[0074] S2. Titanium tetrachloride was vaporized and mixed with hydrogen disulfide gas in a 1:2 volume ratio, then heated at 520°C. The product was then introduced into diphenyl ether via a hot stream to prepare a 0.10 mol / L titanium disulfide organic dispersion. Alum was weighed at a molar ratio of 0.15 to titanium disulfide and evenly dispersed in the titanium disulfide organic dispersion. The temperature was then raised to 140°C at a rate of 1.5°C / min and maintained for 2 hours. The solvent was evaporated, and deionized water was added. The mixture was thoroughly stirred, filtered, and dried to obtain a lamellar titanium disulfide.

[0075] S3. Weigh a lithium-rich manganese-based single crystal precursor, lamellar titanium disulfide, and lithium hydroxide in a molar ratio of 1:0.004:1.20, mix them evenly, heat them to 350°C at a rate of 1.5°C / min, and keep them warm for 6.5 hours. Then, heat them to 875°C at a rate of 5°C / min and keep them warm for 24 hours for sintering to obtain a lithium-rich manganese-based single crystal material coated with lamellar titanium disulfide.

[0076] Example 3

[0077] A method for preparing a lamellar structured titanium disulfide-coated modified lithium-rich manganese-based single crystal material, comprising the following specific steps:

[0078] S1. Nickel chloride, cobalt chloride, and manganese chloride were weighed at a molar ratio of 1.5:1.5:6 and dissolved in deionized water to prepare a 1.8 mol / L mixed metal salt solution. Nanoalumina particles (30 nm in diameter) at a volume of 2 / 25 of the mixed salt solution and sodium lauryl sulfate at a volume of 1 / 125 of the mixed metal salt solution were added to the mixed salt solution. After the nanoalumina particles were dispersed and stabilized, sodium carbonate at a concentration of 2.2 mol / L and tartaric acid at a concentration of 2.6 mol / L were added to coprecipitate a lithium-rich manganese-based precursor with the nanoalumina particles as the heterogeneous core. The prepared lithium-rich manganese-based precursor was immersed in a 4.5 mol / L sodium hydroxide solution. After the reaction was complete, the precursor was filtered, washed, dried, and crushed by ball milling to obtain a lithium-rich manganese-based single crystal precursor.

[0079] S2. Titanium tetrachloride is vaporized and mixed with hydrogen disulfide gas in a 1:2 volume ratio, then heated to 490°C. The resulting mixture is then introduced into diphenyl ether via a hot stream to prepare a 0.30 mol / L titanium disulfide organic dispersion. Alum is weighed at a molar ratio of 0.3 to titanium disulfide and evenly dispersed in the titanium disulfide organic dispersion. The temperature is then raised to 190°C at a rate of 2°C / min and maintained for 6 hours. The solvent is evaporated, and deionized water is added. The mixture is thoroughly stirred, filtered, and dried to obtain a lamellar titanium disulfide.

[0080] S3. Weigh a lithium-rich manganese-based single crystal precursor, lamellar titanium disulfide, and lithium hydroxide in a molar ratio of 1:0.006:1.25, mix them evenly, heat them to 500°C at a rate of 2.5°C / min, and keep them warm for 8 hours. Then, heat them to 950°C at a rate of 6°C / min and keep them warm for 32 hours for sintering to obtain a lithium-rich manganese-based single crystal material coated with lamellar titanium disulfide.

[0081] The results of the embodiments and comparative examples were tested

[0082] Material electrochemical performance test:

[0083] The lithium-rich manganese-based materials in Examples 1, 2, 3, and Comparative Example 1 were each fabricated into 3Ah wound soft-pack batteries. The specific method was as follows: the lithium-rich manganese-based material, PVDF, and carbon nanotube slurry were mixed in a mass ratio of 98.2:1.2:0.6 to form a slurry. The positive electrode sheet was prepared by coating, roll-pressing, baking, cutting, and tab welding. The negative electrode sheet was prepared by mixing graphite, SP, CMC, and SBR in a mass ratio of 96:1.4:0.8:1.8 to form a slurry. The negative electrode sheet was prepared by coating, roll-pressing, baking, cutting, and tab welding. The positive and negative electrodes were then wound, cased, top and side sealed, liquid injected, sealed, formed, aged, sealed, and then capacity divided to obtain the 3Ah wound soft-pack batteries. The batteries were then tested at a voltage of 2.0-4.8V for a 0.1C first discharge and first efficiency, and a 25°C cycle test. The test results are shown in Table 1.

[0084] Table 1 3Ah soft pack battery 0.1C charge and discharge, rate discharge test results

[0085]

[0086] It can be seen from the test results in Table 1 that compared with the lithium-rich manganese materials in the embodiments and the comparative examples, the first release, first effect and cycle performance of the embodiments are significantly better than those of the comparative examples. This is because the lithium-rich manganese-based polycrystalline material prepared in the comparative example has low structural mechanical strength and poor firmness. Under high compaction conditions, these secondary spherical particles are easily squeezed and crushed, resulting in the exposure of particles inside the material, increased side reactions and aggravated metal ion dissolution, and decreased electrochemical performance. At the same time, the primary particle size is too small and has many structural defects, which makes it easy for structural collapse to occur under high-voltage charge and discharge, and it is difficult for the secondary particles to encapsulate these overly fine particles. Therefore, it is difficult to suppress the interfacial side reactions during high-voltage charge and discharge, causing material structure damage. Moreover, although the same coating modification was performed on the material in the comparative example, the modification effect was poor and did not achieve the ideal effect of improving performance. The lithium-rich manganese-based material prepared in the embodiment is a single crystal material, which can well solve the problems of low mechanical strength, low compaction and poor cycle stability, and the coating method in the present invention can achieve the purpose of modification, effectively improving the specific capacity, first effect and cycle life of the material.

[0087] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a modified lithium-rich manganese-based single crystal material, characterized in that: The chemical formula of the lithium-rich manganese-based single crystal material is xLi2MnO3·(1-x)LiNi a Co b Mn c O2, where 0<x<1, 0<a<1, 0<b<1, 0<c<0.1, a+b+c=1; The steps include: S1. Obtaining lithium-rich manganese-based single crystal precursor: A nickel source, a cobalt source, and a manganese source are weighed in a stoichiometric ratio and dissolved in deionized water to obtain a mixed metal salt solution; nano-alumina particles and a surfactant are added to the mixed salt solution and stirred to disperse; after the nano-alumina particles are stably dispersed, a precipitant and a complexing agent are added to the solution to obtain a lithium-rich manganese-based precursor having the nano-alumina particles as a heterogeneous core through co-precipitation; the lithium-rich manganese-based precursor is then immersed in a strong alkaline solution, and after the reaction is complete, the precursor is filtered, washed, dried, and crushed by ball milling to obtain a lithium-rich manganese-based single crystal precursor; S2. Obtaining lamellar titanium disulfide: Titanium tetrachloride is vaporized and mixed with hydrogen disulfide gas and heated, and the product is introduced into an organic solvent through a hot air flow to prepare a titanium disulfide organic dispersion; a water-soluble salt is uniformly dispersed in the titanium disulfide organic dispersion, the temperature is raised to 120-200°C, and the temperature is maintained for 0.5-6 hours, the solvent is evaporated, and deionized water is added. After thorough stirring, the mixture is filtered and dried to obtain a lamellar titanium disulfide; S3. The lithium-rich manganese-based single crystal precursor, a lamellar structure of titanium disulfide, and a lithium salt are mixed and sintered to obtain a lamellar structure of titanium disulfide-coated modified lithium-rich manganese-based single crystal material; The order of the above steps S1 and S2 is not critical.

2. The preparation method according to claim 1, wherein: In S1, the nickel source is at least one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride; And / or, the cobalt source is at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, and cobalt chloride; And / or, the manganese source is at least one of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride; And / or, the concentration of the mixed metal salt solution is 0.5-2.0 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that: In S1, the particle size of the nano-alumina particles is 20-80 nm; the amount of the nano-alumina particles added is 1 / 100-1 / 10 of the volume of the mixed metal salt solution; And / or, the surfactant is at least one of benzenesulfonyl hydrazide, sodium lauryl sulfate, and sodium fatty alcohol polyoxyethylene ether sulfate; the amount of the surfactant added is 3 / 1000 to 1 / 100 of the volume of the mixed metal salt solution; And / or, the precipitant is at least one of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, and ammonium bicarbonate, and the precipitant is added in the form of an aqueous solution of the precipitant, and the concentration of the aqueous solution of the precipitant is 0.8 to 2.3 mol / L; And / or, the complexing agent is at least one of citric acid, oxalic acid, and tartaric acid, the complexing agent is added in the form of a complexing agent aqueous solution, and the concentration of the complexing agent is 1.2-2.8 mol / L.

4. The preparation method according to any one of claims 1 to 3, characterized in that: In S1, the strong alkali solution is at least one of an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, and an alcoholic sodium hydroxide solution; and the concentration of the strong alkali solution is 0.5-5.0 mol / L.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In S2, the titanium tetrachloride is gasified and mixed with hydrogen disulfide gas in a volume ratio of 1:2; the heating temperature is 480-540°C; And / or, the organic solvent is at least one of ethylene glycol phenyl ether, benzyl alcohol, isophorone, methyl benzoate, sulfolane, diphenyl ether, and glycerol; And / or, the molar concentration of the titanium disulfide organic dispersion is 0.05-0.35 mol / L.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In S2, the water-soluble salt is at least one of cubic sodium chloride, potassium chloride, calcium chloride, alum, cesium chloride, ammonium chloride and hexagonal zinc chloride, aluminum chloride and magnesium chloride; and / or, the molar ratio of the water-soluble salt to the titanium disulfide in the titanium disulfide organic dispersion is (0.15-0.35):1; And / or, the heating program of the heating is to increase the temperature to the target temperature at a heating rate of 0.5-2.0°C / min.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In S3, the molar ratio of the lithium-rich manganese-based single crystal precursor, the lamellar titanium disulfide and the lithium source is 1:(0.002~0.01):(1.1~1.3); wherein the lithium source includes at least one of the following: lithium hydroxide and lithium carbonate.

8. The preparation method according to any one of claims 1 to 7, characterized in that: In S3, the sintering process parameters include: heating to 300-600°C at 1-3°C / min and keeping warm for 6-8 hours, then heating to 850-950°C at 3-6°C / min and keeping warm for 24-36 hours.

9. The modified lithium-rich manganese-based single crystal material prepared according to the method according to any one of claims 1 to 8.

10. A lithium-ion battery comprising a positive electrode, characterized in that: The material of the positive electrode includes the modified lithium-rich manganese-based single crystal material according to claim 9.

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