A modified lithium-rich manganese-based material and preparation method thereof

Abstract

The present invention discloses a modified lithium-rich manganese-based material and a preparation method thereof. The chemical formula of the lithium-rich manganese-based single crystal material in the modified lithium-rich manganese-based 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, is prepared as follows: first, a mixture of colloidal spheres is prepared by self-assembly of catechol compounds and polyether compounds, and then the colloidal spheres are dispersed in a mixed metal salt solution of nickel, cobalt, and manganese. A precipitant is added, and after dialysis and evaporation, colloidal spheres coated with a lithium-rich manganese-based precursor are obtained. The colloidal spheres are then uniformly dispersed in an organic solution with a lithium source and impregnated onto a carbon material. A microporous carbon-coated lithium-rich manganese-based material is obtained by current pulses. The lithium-rich manganese-based material prepared by this method has excellent rate, capacity, and cycle stability due to the porosity and excellent electrical conductivity of the coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of positive electrode materials, and in particular relates to a modified lithium-rich manganese-based material and a preparation method thereof. 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 present invention provides a modified lithium-rich manganese-based material and a preparation method thereof.

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

[0006] A modified lithium-rich manganese-based material, wherein the chemical formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiNi a Co b Mn cO2, where 0<x<1, 0<a<1, 0<b<1, 0<c<0.1, a+b+c=1.

[0007] The preparation method of the modified lithium-rich manganese-based material comprises the following steps:

[0008] S1. Weigh the catechol compound and the polyether compound in a certain molar ratio, place them in a mortar, add deionized water while grinding until a colloid is formed, then add a colloid stabilizer, continue grinding, and obtain a stable colloidal sphere of the mixture of the two;

[0009] S2. Metal salts of nickel, cobalt, and manganese are weighed in a stoichiometric ratio and completely dissolved in deionized water to obtain a mixed metal salt solution of nickel, cobalt, and manganese, and the product of S1 is uniformly dispersed therein, and a precipitant is added dropwise. After dialysis and evaporation, colloidal spheres coated with a lithium-rich manganese-based precursor are obtained;

[0010] S3. The product of S2 is mixed with a lithium source in a certain molar ratio and uniformly dispersed in an organic solvent, and then impregnated on a carbon material. The carbon material is subjected to current pulse heating in a nitrogen environment, and a microporous carbon-coated lithium-rich manganese-based material is prepared through ultrasonic vibration and sieving, which is the modified lithium-rich manganese-based material.

[0011] The modified lithium-rich manganese-based material prepared by the present invention has excellent electrical conductivity, which improves the rate performance of the material. On the other hand, the substrate (lithium-rich manganese-based material) and the coating layer have a high bonding strength, which ensures the coating effect and coating quality, and improves the stability and cycle life of the material. At the same time, the porosity of the microporous carbon can ensure the smooth passage of lithium ions, while increasing the material's ability to absorb and retain liquid, thereby comprehensively improving the performance of the material.

[0012] In the above method S1, the molar ratio of the catechol compound to the polyether compound is 1:(0.005-0.1), and the preferred molar ratio is 1:(0.02-0.1).

[0013] In the above method S1, the catechol compound is at least one of dopamine, catecholsulfonphthalein, 4-nitrocatechol, 4-bromocatechol, isoproterenol, levodopa, quercetin, apomorphine, ellagic acid, and di-hydroxybenzimidazolone; the polyether compound is at least one of polymethoxyethylene ether, polyether ester, polyether sulfone, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, alkylolamide polyoxyethylene ether, block polyoxyethylene-polyoxypropylene ether, and fatty acid polyoxyethylene (10) ester.

[0014] In the above method S1, the colloidal stabilizer is at least one of itaconic acid, sorbitol, sodium lignin, glycerol, Span, and Tween; the amount of the colloidal stabilizer added is 1 / 60 to 1 / 15 of the total amount of the catechol compound and the polyether compound, preferably 1 / 40 to 1 / 20.

[0015] In the above method S1, the temperature of the deionized water is controlled at 35-65°C.

[0016] In the above method S1, the grinding time can be continued for 15 to 45 minutes.

[0017] In the above method S2, the nickel salt is at least one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride; the cobalt salt is at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, and cobalt chloride; and the manganese salt is at least one of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride.

[0018] In the above method S2, the concentration of the mixed metal salt solution of nickel, cobalt and manganese is 0.8~2.4mol / L.

[0019] 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 1:1:6.

[0020] In the above method S2, the molar ratio of the product of S1 to the total metal ions in the mixed metal salt solution of nickel, cobalt and manganese is 1:(0.002~0.05), preferably 1:(0.008~0.05).

[0021] In the above method S2, the precipitant is at least one of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, and oxalic acid; 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 1.0 to 3.5 mol / L.

[0022] In the above method S3, the molar ratio of the product of S2 to the lithium source is 1:(1.15~1.5); the lithium source is at least one of lithium hydroxide and lithium carbonate.

[0023] In the above method S3, the organic solvent is at least one of dimethyl sulfoxide, ethylene glycol, methanol, aniline, acetone, pyridine, and acetonitrile.

[0024] In the above method S3, the carbon material is at least one of charcoal, coke, and activated carbon.

[0025] In the above method S3, the current pulse is performed in a nitrogen environment, and the parameters of the current pulse are a pulse current of 25-55A and a duration of 15-50s.

[0026] In the above method S3, the reaction product is peeled off from the base carbon material by ultrasonic vibration, and the carbon layer particles are simultaneously refined, and the base carbon is removed by sieving to obtain a microporous carbon-coated lithium-rich manganese-based material. The sieving can pass through an 1800 mesh sieve.

[0027] The present invention also protects a lithium ion battery.

[0028] The lithium-ion battery comprises a positive electrode and a negative electrode, and the material of the positive electrode comprises the above-mentioned modified carbon-coated lithium-rich manganese-based material.

[0029] The present invention has the following beneficial technical effects and advantages:

[0030] 1. The present invention utilizes the hydrogen bond interaction between catechol compounds and polyether compounds (ROR, "ether oxygen bond"), and when the two are mixed and ground with water as the wet grinding solvent, organic-organic self-assembly occurs to form a colloid. Due to the addition of a stabilizer during the grinding process, the prepared colloidal spheres are uniform and stable.

[0031] 2. During the coprecipitation process for preparing a lithium-rich manganese-based precursor, the present invention incorporates colloidal spheres composed of catechol compounds and polyether compounds. Since the catechol group has a strong chelating ability for various metal ions, it serves as a chelating agent for preparing the lithium-rich manganese-based precursor, allowing nickel, cobalt, and manganese ions to chelate and precipitate on the surface of the colloidal spheres. Dialysis is performed to remove the precipitant ions, and the solvent is then evaporated to obtain colloidal spheres coated with the lithium-rich manganese-based precursor.

[0032] 3. The present invention uses carbon material as a substrate, and immerses a mixed stable dispersion of colloidal spheres coated with a lithium-rich manganese-based precursor and a lithium source thereon. The Joule heating of the current pulse can raise the temperature to 800-1200°C within tens of seconds, so that the carbonization of the colloid spheres of the catechol compound and the polyether compound, the decomposition of the lithium source and the solid-phase reaction of its decomposition products with the lithium-rich manganese-based precursor can be completed in a relatively short time. The base carbon has high thermal radiation and low heat capacity. After the current pulse heating is completed, the sample can be cooled rapidly, which greatly shortens the material preparation cycle and improves the strength of the bond between the lithium-rich manganese-based material and the carbon layer. After ultrasonic vibration, the reaction product is peeled off from the base carbon, and the carbon layer particles are refined. The base carbon is sieved to remove the microporous carbon-coated lithium-rich manganese-based material.

[0033] Therefore, the preparation method of the present invention uses catechol compounds and polyether compounds as carbon sources. Due to the hydrogen bonding interaction between the two, the mixture self-assembles to form colloidal spheres. Furthermore, the present invention eliminates the traditional chelating agents used in coprecipitation methods. Due to the strong chelating effect of the catechol group on metal ions, the lithium-rich manganese-based precursor can chelate and precipitate nuclei on the surface of the colloidal spheres. Finally, the present invention uses current pulses to heat the colloidal spheres coated with the lithium-rich manganese-based precursor and the lithium source impregnated on the carbon material, completing the thermal reaction and sample cooling in a very short time.

[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 modified carbon-coated lithium-rich manganese-based material prepared in Example 1. DETAILED DESCRIPTION

[0036] 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.

[0037] 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.

[0038] The present invention discloses a modified carbon-coated lithium-rich manganese-based material and a preparation method thereof, the preparation method comprising:

[0039] S1. Weigh a catechol compound and a polyether compound in a specific molar ratio, place them in a mortar, and grind them while adding deionized water at a temperature of 35-65°C until a colloid is formed. Then, add a colloidal stabilizer and continue grinding for 15-45 minutes to obtain a stable colloidal sphere of the mixture.

[0040] Wherein, the molar ratio of the catechol compound to the polyether compound is 1:(0.005~0.1);

[0041] The catechol compound is at least one of dopamine, catecholsulfonphthalein, 4-nitrocatechol, 4-bromocatechol, isoproterenol, levodopa, quercetin, apomorphine, ellagic acid, and di-hydroxybenzimidazolone; the polyether compound is at least one of polymethoxyethylene ether, polyether ester, polyether sulfone, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, alkylolamide polyoxyethylene ether, block polyoxyethylene-polyoxypropylene ether, and fatty acid polyoxyethylene (10) ester.

[0042] The colloidal stabilizer is at least one of itaconic acid, sorbitol, sodium lignin, glycerol, Span, and Tween; and the amount of the colloidal stabilizer added is 1 / 60 to 1 / 15 of the total amount of the catechol compound and the polyether compound.

[0043] S2. Metal salts of nickel, cobalt, and manganese are weighed in a stoichiometric ratio and completely dissolved in deionized water to obtain a mixed metal salt solution of nickel, cobalt, and manganese, and the product of S1 is uniformly dispersed therein, and a precipitant is added dropwise. After dialysis and evaporation, colloidal spheres coated with a lithium-rich manganese-based precursor are obtained;

[0044] Wherein, the nickel salt 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.

[0045] The concentration of the mixed metal salt solution is 0.8~2.4mol / L.

[0046] The molar ratio of the product of S1 to the total metal ions in the mixed metal salt solution of nickel, cobalt and manganese is 1:(0.002~0.05).

[0047] Wherein, the precipitant is an aqueous solution of at least one of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, and oxalic acid; and the concentration of the precipitant is 1.0-3.5 mol / L.

[0048] S3. The product of S2 is mixed with a lithium source in a certain molar ratio and uniformly dispersed in an organic solution, and then impregnated on a carbon material. The carbon material is subjected to current pulse heating in a nitrogen environment, and a microporous carbon-coated lithium-rich manganese-based material is prepared through ultrasonic vibration and sieving.

[0049] The molar ratio of the S2 product to the lithium source is 1:(1.15-1.5). The lithium source is at least one of lithium hydroxide and lithium carbonate.

[0050] Wherein, the organic solvent is at least one of dimethyl sulfoxide, ethylene glycol, methanol, aniline, acetone, pyridine and acetonitrile.

[0051] Wherein, the carbon material is at least one of charcoal, coke and activated carbon.

[0052] The current pulse parameters are 25-55A and a pulse current duration of 15-50s.

[0053] The present invention also provides a lithium-rich manganese-based material, the chemical formula of which 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.

[0054] In order to better understand the present invention, examples and comparative examples are provided below.

[0055] Example 1

[0056] A modified carbon-coated lithium-rich manganese-based material and a preparation method thereof, the specific steps are as follows:

[0057] S1. Apomorphine and alkylphenol polyoxyethylene ether were weighed in a molar ratio of 1:0.05 and placed in a mortar. Deionized water was added while grinding, and the temperature of the deionized water was controlled at 45°C until a colloid was formed. Then, itaconic acid was added at a concentration of 1 / 40 of the total amount of apomorphine and alkylphenol polyoxyethylene ether. Grinding was continued for 25 minutes to obtain a stable colloidal sphere of the mixture of the two.

[0058] S2. Nickel nitrate, cobalt nitrate, and manganese nitrate were weighed in a molar ratio of 1:1:6 and completely dissolved in deionized water to obtain a 2.0 mol / L mixed metal salt solution of nickel, cobalt, and manganese. The product of S1 was uniformly dispersed therein (the molar ratio of the product of S1 to the sum of nickel, cobalt, and manganese ions was 1:0.02). An aqueous solution of ammonium bicarbonate with a molar concentration of 1.5 mol / L was then added dropwise. After dialysis and evaporation, colloidal spheres coated with the lithium-rich manganese-based precursor were obtained.

[0059] S3. The product of S2 was mixed with lithium hydroxide in a molar ratio of 1:1.3 and uniformly dispersed in a pyridine solvent. The mixture was then impregnated on charcoal and subjected to current pulse heating in a nitrogen environment (pulse current 35 A, duration 30 s, heating temperature 900°C). After ultrasonic vibration and sieving (1800 mesh sieve), a microporous carbon-coated lithium-rich manganese-based material was prepared.

[0060] Comparative Example 1

[0061] A method for preparing a carbon-coated lithium-rich manganese-based positive electrode material, the specific steps are as follows:

[0062] S1. Weigh nickel nitrate, cobalt nitrate, and manganese nitrate in a molar ratio of 1:1:6 and completely dissolve them in deionized water to obtain a 2.0 mol / L mixed metal salt solution of nickel, cobalt, and manganese. Add 1.5 mol / L aqueous ammonium bicarbonate and 2.0 mol / L aqueous ammonia dropwise to obtain a lithium-rich manganese-based precursor by coprecipitation.

[0063] S2. Weigh a lithium-rich manganese-based precursor, glucose, and lithium hydroxide in a molar ratio of 1:0.008:1.3, mix them evenly, and sinter them by heating to 900°C at a rate of 5°C / min and keeping them warm for 28 hours to obtain a carbon-coated modified lithium-rich manganese-based positive electrode material.

[0064] Example 2

[0065] A modified carbon-coated lithium-rich manganese-based material and a preparation method thereof, the specific steps are as follows:

[0066] S1. Apomorphine and alkylphenol polyoxyethylene ether were weighed in a molar ratio of 1:0.08 and placed in a mortar. Deionized water was added while grinding, and the temperature of the deionized water was controlled at 50°C until a colloid was formed. Then, itaconic acid was added at a concentration of 1 / 30 of the total amount of apomorphine and alkylphenol polyoxyethylene ether. Grinding was continued for 25 minutes to obtain a stable colloidal sphere of the mixture of the two.

[0067] S2. Nickel nitrate, cobalt nitrate, and manganese nitrate were weighed in a molar ratio of 1:1:6 and completely dissolved in deionized water to obtain a 1.5 mol / L mixed metal salt solution of nickel, cobalt, and manganese. The product of S1 was uniformly dispersed in the solution (the molar ratio of the product of S1 to the sum of nickel, cobalt, and manganese ions was 1:0.008). Ammonium bicarbonate with a molar concentration of 2.0 mol / L was then added dropwise. After dialysis and evaporation, colloidal spheres coated with the lithium-rich manganese-based precursor were obtained.

[0068] S3. The product of S2 was mixed with lithium hydroxide in a molar ratio of 1:1.2 and uniformly dispersed in a pyridine solvent. The mixture was then impregnated on charcoal and subjected to current pulse heating in a nitrogen environment (pulse current 30 A, duration 40 s, heating temperature 870°C). After ultrasonic vibration and sieving, a microporous carbon-coated lithium-rich manganese-based material was obtained.

[0069] Example 3

[0070] A modified carbon-coated lithium-rich manganese-based material and a preparation method thereof, the specific steps are as follows:

[0071] S1. Apomorphine and alkylphenol polyoxyethylene ether were weighed in a molar ratio of 1:0.02 and placed in a mortar. Deionized water was added while grinding, and the temperature of the deionized water was controlled at 60°C until a colloid was formed. Then, itaconic acid was added at a concentration of 1 / 20 of the total amount of apomorphine and alkylphenol polyoxyethylene ether. Grinding was continued for 25 minutes to obtain a stable colloidal sphere of the mixture of the two.

[0072] S2. Nickel nitrate, cobalt nitrate, and manganese nitrate were weighed in a molar ratio of 1:1:6 and completely dissolved in deionized water to obtain a 1.0 mol / L mixed metal salt solution of nickel, cobalt, and manganese. The product of S1 was uniformly dispersed in the solution (the molar ratio of the product of S1 to the sum of nickel, cobalt, and manganese ions was 1:0.04). Ammonium bicarbonate with a molar concentration of 2.5 mol / L was then added dropwise. After dialysis and evaporation, colloidal spheres coated with the lithium-rich manganese-based precursor were obtained.

[0073] S3. The product of S2 was mixed with lithium hydroxide in a molar ratio of 1:1.4 and uniformly dispersed in a pyridine solvent. The mixture was then impregnated on charcoal and subjected to current pulse heating in a nitrogen environment (pulse current 45 A, duration 20 s, heating temperature 930°C). After ultrasonic vibration and sieving, a microporous carbon-coated lithium-rich manganese-based material was obtained.

[0074] The results of the embodiments and comparative examples were tested

[0075] Material electrochemical performance test:

[0076] 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 97:1.2:1.8 to form a slurry. The positive electrode sheet was prepared by coating, rolling, baking, cutting, and welding the tabs. Graphite, SP, CMC, and SBR were mixed in a mass ratio of 96:1.4:0.8:1.8 to form a slurry. The negative electrode sheet was prepared by coating, rolling, baking, cutting, and welding the tabs. The positive and negative electrodes were then wound, placed in a case, top and side sealed, liquid injected, sealed, formed, aged, sealed, and then separated to obtain a 3Ah wound soft-pack battery. The battery was then tested at a voltage of 2.0-4.8V for a 0.1C first discharge and first efficiency, a 25°C cycle, and a 3C rate discharge test. The test results are shown in Table 1.

[0077]

[0078] The test results in Table 1 show that compared with the lithium-rich manganese materials in the examples and comparative examples, the first discharge, first efficiency, cycle, and rate discharge performance of the examples are significantly better than those of the comparative examples. This is because, although the lithium-rich manganese-based materials prepared in the comparative examples were modified by carbon coating, the coating effect was poor (uneven coating, excessively thick coating layer, coating layer detachment, etc.), and the desired performance improvement was not achieved. The lithium-rich manganese-based materials prepared in the examples, on the other hand, not only have a good coating effect (good uniformity and high bonding strength between the substrate and the coating), but also have a porous coating structure, which ensures smooth lithium ion pathways and strong liquid absorption and retention capabilities, effectively improving the material's specific capacity, first efficiency, cycle life, and rate performance.

[0079] 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 material, characterized in that: The chemical formula of the lithium-rich manganese-based 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 preparation method comprises the following steps: S1. Weigh the catechol compound and the polyether compound in a certain molar ratio, place them in a mortar, add deionized water while grinding until a colloid is formed, then add a colloid stabilizer, continue grinding, and obtain a stable colloidal sphere of the mixture of the two; S2. Metal salts of nickel, cobalt, and manganese were weighed in a stoichiometric ratio and completely dissolved in deionized water to obtain a mixed metal salt solution of nickel, cobalt, and manganese. The product of S1 was evenly dispersed in the mixed metal salt solution, and a precipitant was added dropwise. After dialysis and evaporation, colloidal spheres coated with a lithium-rich manganese-based precursor were obtained; S3. The product of S2 is mixed with a lithium source in a certain molar ratio and uniformly dispersed in an organic solvent, and then impregnated on a carbon material. The carbon material is subjected to current pulse heating in a nitrogen environment, and a microporous carbon-coated lithium-rich manganese-based material is prepared through ultrasonic vibration and sieving, which is the modified lithium-rich manganese-based material.

2. The preparation method according to claim 1, wherein: In S1, the molar ratio of the catechol compound to the polyether compound is 1:(0.005-0.1); And / or, in S1, the catechol compound is at least one of dopamine, catecholsulfonphthalein, 4-nitrocatechol, 4-bromocatechol, isoproterenol, levodopa, quercetin, apomorphine, and ellagic acid; the polyether compound is at least one of polymethoxyethylene ether, polyether ester, polyether sulfone, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, alkylolamide polyoxyethylene ether, block polyoxyethylene-polyoxypropylene ether, and fatty acid polyoxyethylene (10) ester.

3. The preparation method according to claim 2, wherein: In the S1, the molar ratio of the catechol compound to the polyether compound is 1:(0.02-0.1).

4. The preparation method according to any one of claims 1 to 3, characterized in that: In S1, the colloidal stabilizer is at least one of itaconic acid, sorbitol, sodium lignin, glycerol, Span, and Tween; and the amount of the colloidal stabilizer added is 1 / 60 to 1 / 15 of the total amount of the catechol compound and the polyether compound.

5. The preparation method according to claim 4, characterized in that: In the above S1, the amount of the colloidal stabilizer added is 1 / 40 to 1 / 20 of the total amount of the catechol compound and the polyether compound.

6. The preparation method according to any one of claims 1 to 3, characterized in that: In said S1, the temperature of the deionized water is controlled at 35-65°C; And / or, in S1, the grinding is continued for 15 to 45 minutes.

7. The preparation method according to any one of claims 1 to 3, characterized in that: In S2, the nickel salt is at least one of nickel nitrate, nickel sulfate, nickel acetate, and nickel chloride; the cobalt salt is at least one of cobalt nitrate, cobalt sulfate, cobalt acetate, and cobalt chloride; the manganese salt is at least one of manganese nitrate, manganese sulfate, manganese acetate, and manganese chloride; And / or, in S2, the concentration of the mixed metal salt solution of nickel, cobalt and manganese is 0.8 to 2.4 mol / L.

8. The preparation method according to any one of claims 1 to 3, characterized in that: In said S2, the molar ratio of the product of said S1 to the total metal ions in the mixed metal salt solution of nickel, cobalt and manganese is 1:(0.002-0.05); And / or, in S2, the precipitant is at least one of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, and oxalic acid; 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 1.0 to 3.5 mol / L.

9. The preparation method according to claim 8, characterized in that: In S2, the molar ratio of the product of S1 to the total metal ions in the mixed metal salt solution of nickel, cobalt and manganese is 1:(0.008-0.05).

10. The preparation method according to any one of claims 1 to 3, characterized in that: In S3, the molar ratio of the product of S2 to the lithium source is 1:(1.15-1.5); the lithium source is at least one of lithium hydroxide and lithium carbonate; And / or, in S3, the organic solvent is at least one of dimethyl sulfoxide, ethylene glycol, methanol, aniline, acetone, pyridine, and acetonitrile; And / or, in S3, the carbon material is at least one of charcoal, coke, and activated carbon.

11. The preparation method according to any one of claims 1 to 3, characterized in that: In S3, the current pulse is performed in a nitrogen environment, and the parameters of the current pulse are a pulse current of 25 to 55 A and a duration of 15 to 50 seconds.

12. The modified lithium-rich manganese-based material prepared according to the method according to any one of claims 1 to 11.

13. A lithium-ion battery comprising a positive electrode, characterized in that: The material of the positive electrode includes the modified lithium-rich manganese-based material according to claim 12.

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