A double-layer coated lithium-rich manganese-based positive electrode material and its preparation method and application

Abstract

The present invention provides a double-layer coated lithium-rich manganese-based positive electrode material and its preparation method and application, which belongs to the technical field of lithium-ion positive electrode materials. The double-layer coated lithium-rich manganese-based positive electrode material of the present invention comprises a lithium-rich manganese-based material as a base material, Cu9S5 as an inner layer coating material, and cerium aluminum oxide as an outer layer coating material. 2‑ The preparation method of doping, Cu9S5 inner layer coating and cerium aluminum oxide outer layer coating enables the lithium-rich manganese-based positive electrode material of the present invention to increase a large number of oxygen vacancies, thereby promoting the lithium-rich manganese-based material to have excellent electrochemical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery positive electrode materials, in particular to a double-layer-coated lithium-rich manganese-based positive electrode material and a preparation method and application thereof. Background Art

[0002] With the diversification and popularization of electronic devices, the demand for lithium-ion batteries continues to increase. The cathode material of lithium-ion batteries is the core key material of lithium-ion batteries. The cathode material is a key factor in determining the energy density, service life and cost of lithium-ion batteries.

[0003] Among the existing commercial lithium-ion battery positive electrode materials, LiCoO2, LiMnO4, LiFePO4 and other materials are mainly used as positive electrode materials. However, the actual specific capacity of the above positive electrode materials is less than 200mAh / g, which cannot meet the performance requirements of lithium-ion batteries at this stage.

[0004] Studies have reported that by combining Li2MnO3 (LiMnO phase) with layered transition metal oxide LiMO2 (LiMO phase) to prepare a lithium-rich solid solution material, a higher specific capacity can be obtained, and this material is called a lithium-rich manganese-based material. Studies have shown that lithium-rich manganese-based materials often have a high specific capacity close to 200mAh / g or more, making them a good choice for achieving a high specific energy of 400Wh / kg for lithium-ion batteries, and they have great development prospects. However, as positive electrode materials for lithium-ion batteries, lithium-rich manganese-based materials have electrochemical performance problems such as low first coulombic efficiency, which has also seriously restricted the application process of lithium-rich manganese-based materials.

[0005] Prior art CN 112510200 A discloses a method for preparing a double-conductive-layer-coated lithium-rich manganese-based material. The method involves coating the surface of the lithium-rich manganese-based cathode material with a mixture of lithium carbonate and polyaniline to improve the electrochemical performance of the material. However, the initial coulombic efficiency of this double-conductive-layer-coated lithium-rich manganese-based material is only 80.9%, which is still relatively low.

[0006] Therefore, it is necessary to provide a lithium-rich manganese-based positive electrode material with high specific capacity, rate performance and first coulombic efficiency. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects of poor electrochemical performance in the prior art and provide a lithium-rich manganese-based positive electrode material with a double-layer coating on the surface, with cerium aluminum oxide as the inner coating material and copper sulfate as the outer coating material. The lithium-rich manganese-based positive electrode material obtained by double-layer coating has excellent specific capacity, rate performance and first coulombic efficiency.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned double-layer-coated lithium-rich manganese-based positive electrode material.

[0009] Another object of the present invention is to provide an application of the above-mentioned double-layer-coated lithium-rich manganese-based positive electrode material.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A lithium-rich manganese-based positive electrode material with a double-layer coating on the surface, comprising a base material, an inner coating material and an outer coating material, wherein the inner coating material is between the base material and the outer coating material;

[0012] The matrix material is a lithium-rich manganese-based material, the inner layer coating material is Cu9S5, and the outer layer coating material is cerium aluminum oxide.

[0013] The surface of the lithium-rich manganese-based positive electrode material of the present invention is coated with a double layer of material, wherein the inner layer coating material is Cu9S5 and the outer layer coating material is cerium aluminum oxide (CeAlO δ ), providing a large number of oxygen vacancies for the lithium-rich manganese-based cathode material. The increase in oxygen vacancies reduces oxygen generation, promotes reversible oxygen redox reactions during charge and discharge, and inhibits the material's crystal structure degradation over long periods of time. Furthermore, the increase in oxygen vacancies means more lithium insertion and extraction sites are available during subsequent charge and discharge cycles, resulting in a higher initial discharge capacity.

[0014] The present invention uses double-layer coating to enable the lithium-rich manganese-based material to exhibit excellent rate performance and cycle stability, and has high reversible capacity and low voltage decay.

[0015] Preferably, the inner coating material accounts for 0.5 wt.% to 1.5 wt.% of the base material, and more preferably, the inner coating material accounts for 1 wt.% of the base material.

[0016] Preferably, the outer coating material accounts for 2 wt.% to 4 wt.% of the base material, and more preferably, the outer coating material accounts for 3 wt.% of the base material.

[0017] Different coating materials, when applied in appropriate amounts, can enhance the electrochemical performance of lithium-rich manganese-based cathode materials. In the present invention, the coating ratio of the inner coating material is preferably 0.5wt.% to 1.5wt.%, and the coating ratio of the outer coating material is preferably 2wt.% to 4wt.%. Excessive or insufficient coating material may negatively impact the electrochemical performance of the lithium-rich manganese-based cathode material.

[0018] In the present invention, the lithium-rich manganese-based material contains a LiMnO phase and a LiMO phase, wherein M is at least one of Mn, Ni, and Co.

[0019] Preferably, the chemical formula of the lithium-rich manganese-based material is Li1.2 Mn 0.54 Ni 0.13 Co 0.13 O2.

[0020] The present invention also provides a method for preparing the above-mentioned double-layer coated lithium-rich manganese-based positive electrode material, comprising the following steps:

[0021] S1. The lithium-rich manganese-based material is dispersed in deionized water, stirred, dried, and calcined to obtain a pretreated lithium-rich manganese-based material;

[0022] S2. The alcohol-soluble copper salt is dissolved in an ethanol solvent, and the pretreated lithium-rich manganese-based material is added and mixed to obtain a solution A; thioacetamide is dissolved in an ethanol solvent to obtain a solution B;

[0023] The solution B is added dropwise to the solution A, and the obtained mixed solution is subjected to heat treatment. After cooling, the mixed solution is washed and dried. The dried material is placed in a heater, heated to 400-600° C. at a rate of 1-3° C. / min, and kept warm for 1.5-2.5 hours to obtain an inner-layer coated lithium-rich manganese-based material;

[0024] S3. The inner-layer coated lithium-rich manganese-based material is dispersed in deionized water containing a water-soluble cerium salt and a water-soluble aluminum salt, and then ammonia water is added. The obtained mixed solution is dried, and the dried material is placed in a heater, heated to 400-600°C at a rate of 1-3°C / min, and kept warm for 1.5-2.5h to obtain a lithium-rich manganese-based positive electrode material with a double-layer surface coating.

[0025] In step S1, deionized water is used to pre-treat the lithium-rich manganese-based material. Deionized water is used as a pre-activator, and combined with a secondary calcination modification process, the H protons in H2O react with the Li in the lithium-rich manganese-based material. + Perform ion exchange to extract Li from the lithium layer + At the same time, oxygen vacancies are formed, which weakens the shielding between oxygen layers. The modification process may cause proton exchange at the surface interface of lithium-rich manganese-based materials, leading to the generation of oxygen vacancies.

[0026] Preferably, in step S1, the stirring is performed at 50-55° C. for 1-1.5 h.

[0027] More preferably, in step S1, the stirring is performed at 50° C. for 1 hour.

[0028] As the stirring time of deionized water increases, the residual alkali on the surface of the lithium-rich manganese-based material will gradually decrease and tend to be stable.

[0029] Preferably, in step S1, the calcination treatment is performed at 250-350°C for 1.5-2.5 hours. More preferably, in step S1, the calcination treatment is performed at 300°C for 2 hours.

[0030] Preferably, in step S1, the weight ratio of the lithium-rich manganese-based material to deionized water is 1:(6-10).

[0031] More preferably, in step S1, the weight ratio of the lithium-rich manganese-based material to deionized water is 1:8.

[0032] In step S2, the inner layer Cu9S5 of the lithium-rich manganese-based material is coated. 2- The doping of S forms a low-energy Li-S bond, which causes the electron cloud arrangement of the transition metal elements to change, thereby affecting the electron cloud arrangement in the material structure. 2- As the doping amount of S increases, more oxygen vacancies are generated in the structure. 2- It has extremely strong reducing properties and can deprive the lattice oxygen in lithium-rich manganese-based materials to form SO4 2- structure.

[0033] Cu9S5 has higher electronic conductivity and combined with S 2- Doping can form low-energy Li-S bonds, which can improve the rate performance of lithium-rich manganese-based processes. 2- Under the combined effect of doping, the valence of transition metal elements is reduced to introduce more oxygen vacancies into the material structure, thereby reducing the O 2- activity.

[0034] Preferably, in step S2, the alcohol-soluble copper salt is CuCl2·2H2O.

[0035] Preferably, in step S2, the weight ratio of the alcohol-soluble copper salt, thioacetamide and the pretreated lithium-rich manganese-based material is (1.5-3):(0.5-1.5):100.

[0036] More preferably, in step S2, the weight ratio of the alcohol-soluble copper salt, thioacetamide and the pretreated lithium-rich manganese-based material is 2:1:100.

[0037] Preferably, in step S2, the heat treatment is carried out at 150°C for 6 hours.

[0038] Preferably, in step S2, the heater is a muffle furnace.

[0039] Preferably, in step S2, the material is placed in a heater, heated to 500°C at a rate of 2°C / min, and then kept warm for 2 hours.

[0040] In step S3, CeO with oxygen storage function in the outer layer coating material cerium aluminum oxide 2- The components provide abundant oxygen vacancies. The large presence of oxygen vacancies on the surface of the material can reduce the surface oxygen partial pressure of the lithium-rich manganese-based positive electrode material. The built-in electric field at the oxygen vacancy center promotes the deintercalation of lithium ions and stabilizes the reversible redox reaction of oxygen.

[0041] Modified by deionized water, S 2- The preparation method of doping, Cu9S5 inner layer coating and cerium aluminum oxide outer layer coating enables the lithium-rich manganese-based positive electrode material of the present invention to increase a large number of oxygen vacancies, thereby promoting the lithium-rich manganese-based material to have excellent electrochemical properties.

[0042] Preferably, in step S3, the water-soluble cerium salt is Ce(NO3)3·6H2O.

[0043] Preferably, in step S3, the water-soluble aluminum salt is Al(NO3)3·9H2O.

[0044] Preferably, in step S3, the molar mass ratio of the water-soluble cerium salt, the water-soluble aluminum salt and the inner-layer coated lithium-rich manganese-based material is (0.45 mol to 0.6 mol): (0.45 mol to 0.6 mol): 10 g.

[0045] Preferably, in step S3, the drying treatment is evaporative drying at 60°C.

[0046] Preferably, in step S3, the material is placed in a heater, heated to 500°C at a rate of 2°C / min, and then kept warm for 2 hours.

[0047] The present invention also protects the application of the above-mentioned double-layer-coated lithium-rich manganese-based positive electrode material as a positive electrode material for lithium-ion batteries.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention develops a double-layer coated lithium-rich manganese-based positive electrode material, which includes a lithium-rich manganese-based material as a base material, Cu9S5 as an inner coating material, and cerium aluminum oxide as an outer coating material.

[0050] Modified by deionized water, S 2- The preparation method of doping, Cu9S5 inner layer coating and cerium aluminum oxide outer layer coating enables the lithium-rich manganese-based positive electrode material of the present invention to increase a large number of oxygen vacancies, thereby promoting the lithium-rich manganese-based material to have excellent electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a TEM image of the double-layered lithium-rich manganese-based positive electrode material prepared in Example 1. DETAILED DESCRIPTION

[0052] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments and drawings, but the embodiments do not limit the present invention in any form.

[0053] The lithium-rich manganese-based material used in the embodiments and comparative examples of the present invention is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 is prepared by the following method:

[0054] First, Mn was synthesized by carbonate co-precipitation method. 0.66 Ni 0.17 Co 0.17 CO3 carbonate precursor; then prepare a mixed solution of MnSO4·H2O, NiSO4·6H2O, and Co SO4·7H2O according to n(Mn)∶n(Ni)∶n(Co)=4∶1∶1, with a total concentration of 2.0mol / L; weigh and prepare 2.0mol / LNa2CO34 solution as a precipitant, 2.0mol / L(NH4)2SO4 solution as a complexing agent, and 0.6mol / L ammonia solution as a reaction base liquid; use a peristaltic pump to control the reaction conditions, and slowly add the metal salt solution, complexing agent solution, and precipitant solution into the reactor under continuous stirring, control the pH value of the reaction system to 7.49~7.53, and react for 12h under continuous stirring; after vacuum drying, obtain a powdery precursor Mn 0.66 Ni 0.17 Co 0.17 CO3; Li is obtained by high temperature solid phase method using known technical means 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 lithium-rich manganese-based materials.

[0055] In the present invention, the method for electrochemical performance testing is as follows:

[0056] The positive electrode material, conductive carbon black and polyvinylidene fluoride were prepared into a slurry in a mass ratio of 8:1:1, and the slurry was evenly coated on a 16-μm-thick aluminum foil with a special scraper to a coating thickness of 120 μm; the slurry was vacuum-dried at 120°C for more than 24 h; CR2025 button cells were assembled in an argon-protected glove box. The electrolyte used was 1 mol / LLiPF6 / EC+DMC (volume ratio 1:1, produced in Suzhou), the separator was 2325 polypropylene film, and the negative electrode was a metallic lithium sheet; its first discharge specific capacity at 2.0-4.6 V, the coulombic efficiency of the first cycle, the capacity retention rate after 100 cycles at a 1 c rate, and the electrochemical performance at different rates were tested.

[0057] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. Unless otherwise specified, the reagents and materials used in the present invention are commercially available.

[0058] Example 1

[0059] This embodiment provides a lithium-rich manganese-based positive electrode material with a double-layer surface coating, and the preparation method is as follows:

[0060] S1.Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 lithium-rich manganese-based material and deionized water are added to a container at a mass ratio of 1:8, and stirred at a constant temperature of 50°C for 1 hour; the water washing time is set to 1 hour, and after stirring, the material is dried and heat-treated at 300°C in an atmosphere furnace for 2 hours; the calcined material is sieved and sealed to obtain a pretreated lithium-rich manganese-based material;

[0061] S2. 1 g of CuCl2·2H2O was dissolved in ethanol, 50 g of the pretreated lithium-rich manganese-based material of step (1) was dispersed in 2 L of ethanol and stirred to obtain solution A; 0.5 g of thioacetamide was dissolved in 250 ml of ethanol to obtain solution B, solution B was added dropwise to solution A and stirred, and then the mixed solution of solution A and solution B was placed in a reactor and heated at 150 ° C for 6 h;

[0062] After natural cooling, the product in the reactor was taken out and washed with deionized water. After washing, the product was dried in a vacuum oven. The dried product was placed in a muffle furnace and heated from room temperature to 500°C at a rate of 2°C / min and kept warm for 2 hours to obtain a 1wt.% Cu9S5-coated lithium-rich manganese-based material, i.e., an inner-layer coated lithium-rich manganese-based material.

[0063] S3. The 1wt.% Cu9S5-coated lithium-rich manganese-based material 10g was dispersed into 3L of deionized water;

[0064] Ce(NO3)3·6H2O and Al(NO3)3·9H2O were weighed in a molar ratio of 1:1, and Ce(NO3)3·6H2O and Al(NO3)3·9H2O were dissolved in deionized water, and the molar concentrations of Ce(NO3)3·6H2O and Al(NO3)3·9H2O were both 0.18 mol / L; then an appropriate amount of ammonia water was added and stirred to obtain a mixed solution; the mixed solution was evaporated at 60°C, and the evaporated material was placed in a muffle furnace, and the temperature was raised from room temperature to 500°C at a rate of 2°C / min, and kept warm for 2h to obtain a lithium-rich manganese-based material coated with a 3wt.% cerium aluminum oxide outer layer, that is, a lithium-rich manganese-based positive electrode material with a double-layer coating on the surface was obtained.

[0065] The double-layered lithium-rich manganese-based cathode material of Example 1 was characterized by TEM analysis. Figure 1 As shown, it can be seen that the material has an inner coating and an outer coating structure; the double-layer coating structure covers the surface coating of the outer layer, which will not destroy the main structure of the lithium-rich manganese-based positive electrode material; the cerium aluminum oxide coating layer is in the form of small particle agglomerates embedded in the particle surface of the inner coating material of the lithium-rich manganese-based material.

[0066] Li in this embodiment 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, pretreated lithium-rich manganese-based materials, inner-layer coated lithium-rich manganese-based materials, and surface double-layer coated lithium-rich manganese-based positive electrode materials were used as positive electrode materials for lithium-ion batteries, and their electrochemical performance tests were carried out respectively. The results are shown in Table 1.

[0067] Table 1 Electrochemical performance test results of Example 1

[0068]

[0069]

[0070] The rate performance test results of the double-layer-coated lithium-rich manganese-based positive electrode material of Example 1 as a positive electrode material for lithium-ion batteries are shown in Table 2.

[0071] Table 2 Rate performance test results of Example 1

[0072]

[0073] Example 2

[0074] This embodiment provides a lithium-rich manganese-based positive electrode material with a double-layer surface coating. The preparation method differs from that of Example 1 in that:

[0075] In step S2, the amount of CuCl2·2H2O added is adjusted to 1.5 g; the amount of thioacetamide added is adjusted to 0.5 g; and the amount of pretreated lithium-rich manganese-based material added is adjusted to 100 g;

[0076] Step S2 prepares a lithium-rich manganese-based material coated with 0.5 wt.% Cu9S5.

[0077] The double-layered lithium-rich manganese-based positive electrode material of Example 2 was used as the positive electrode material of a lithium-ion battery, and the electrochemical performance test was carried out. The results are shown in Table 3.

[0078] Table 3 Electrochemical performance test results of Example 2

[0079] Lithium-rich manganese-based cathode material with double-layer surface coating First discharge specific capacity (mAh / g) 260.2 Coulombic efficiency of the first cycle (%) 87.92 Capacity retention after 100 cycles at 1c rate (%) 92.5

[0080] The rate performance test results of the double-layer-coated lithium-rich manganese-based positive electrode material of Example 2 as a positive electrode material for lithium-ion batteries are shown in Table 4.

[0081] Table 4 Rate performance test results of Example 2

[0082]

[0083] Example 3

[0084] This embodiment provides a lithium-rich manganese-based positive electrode material with a double-layer surface coating. The preparation method differs from that of Example 1 in that:

[0085] In step S2, the amount of CuCl2·2H2O added was adjusted to 3 g; the amount of thioacetamide added was adjusted to 1.5 g; and the amount of pretreatment added was adjusted to 100 g;

[0086] Step S2 prepares a lithium-rich manganese-based material coated with 1.5 wt.% Cu9S5.

[0087] The double-layered lithium-rich manganese-based positive electrode material of Example 3 was used as the positive electrode material of a lithium-ion battery, and the electrochemical performance test was carried out. The results are shown in Table 5.

[0088] Table 5 Electrochemical performance test results of Example 3

[0089] Lithium-rich manganese-based cathode material with double-layer surface coating First discharge specific capacity (mAh / g) 260.1 Coulombic efficiency of the first cycle (%) 87.82 Capacity retention after 100 cycles at 1c rate (%) 92.4

[0090] The rate performance test results of the double-layer-coated lithium-rich manganese-based positive electrode material of Example 3 as a positive electrode material for lithium-ion batteries are shown in Table 6.

[0091] Table 6 Rate performance test results of Example 3

[0092]

[0093] Example 4

[0094] This embodiment provides a lithium-rich manganese-based positive electrode material with a double-layer surface coating. The preparation method differs from that of Example 1 in that:

[0095] In step S3, the molar concentrations of Ce(NO3)3·6H2O and Al(NO3)3·9H2O are adjusted to 0.15 mol / L;

[0096] In step S3, a lithium-rich manganese-based material coated with a 2 wt.% cerium aluminum oxide outer layer is prepared.

[0097] The double-layered lithium-rich manganese-based positive electrode material of Example 4 was used as the positive electrode material of a lithium-ion battery, and the electrochemical performance test was carried out. The results are shown in Table 7.

[0098] Table 7 Electrochemical performance test results of Example 4

[0099] Lithium-rich manganese-based cathode material with double-layer surface coating First discharge specific capacity (mAh / g) 259.8 Coulombic efficiency of the first cycle (%) 87.15 Capacity retention after 100 cycles at 1c rate (%) 92.0

[0100] The rate performance test results of the double-layer-coated lithium-rich manganese-based positive electrode material of Example 4 as a positive electrode material for lithium-ion batteries are shown in Table 8.

[0101] Table 8 Rate performance test results of Example 4

[0102]

[0103] Example 5

[0104] This embodiment provides a lithium-rich manganese-based positive electrode material with a double-layer surface coating. The preparation method differs from that of Example 1 in that:

[0105] In step S3, the molar concentrations of Ce(NO3)3·6H2O and Al(NO3)3·9H2O are adjusted to 0.2 mol / L;

[0106] In step S3, a lithium-rich manganese-based material coated with a 4 wt.% cerium aluminum oxide outer layer is prepared.

[0107] The double-layered lithium-rich manganese-based positive electrode material of Example 5 was used as the positive electrode material of a lithium-ion battery, and the electrochemical performance test was carried out. The results are shown in Table 9.

[0108] Table 9 Electrochemical performance test results of Example 5

[0109] Lithium-rich manganese-based cathode material with double-layer surface coating First discharge specific capacity (mAh / g) 260.4 Coulombic efficiency of the first cycle (%) 88.09 Capacity retention after 100 cycles at 1c rate (%) 92.3

[0110] The rate performance test results of the double-layer-coated lithium-rich manganese-based positive electrode material of Example 5 as a positive electrode material for lithium-ion batteries are shown in Table 10.

[0111] Table 10 Rate performance test results of Example 5

[0112]

[0113] Example 6

[0114] This embodiment provides a lithium-rich manganese-based positive electrode material with a double-layer surface coating. The preparation method differs from that of Example 1 in that:

[0115] In step S1, Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 The mass ratio of O2 lithium-rich manganese-based material and deionized water is 1:6.

[0116] The pretreated lithium-rich manganese-based material and the double-layer-coated lithium-rich manganese-based positive electrode material of Example 6 were used as positive electrode materials for lithium-ion batteries, and their electrochemical performance tests were performed. The results are shown in Table 11.

[0117] Table 11 Electrochemical performance test results of Example 6

[0118]

[0119] The rate performance test results of the double-layer-coated lithium-rich manganese-based positive electrode material of Example 6 as a positive electrode material for lithium-ion batteries are shown in Table 12.

[0120] Table 12 Rate performance test results of Example 6

[0121]

[0122] Example 7

[0123] This embodiment provides a lithium-rich manganese-based positive electrode material with a double-layer surface coating. The preparation method differs from that of Example 1 in that:

[0124] In step S1, Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 The mass ratio of O2 lithium-rich manganese-based material to deionized water is 1:10.

[0125] The pretreated lithium-rich manganese-based material and the double-layer-coated lithium-rich manganese-based positive electrode material of Example 7 were used as positive electrode materials for lithium-ion batteries, and their electrochemical performance tests were performed. The results are shown in Table 13.

[0126] Table 13 Electrochemical performance test results of Example 7

[0127]

[0128] The rate performance test results of the double-layer-coated lithium-rich manganese-based positive electrode material of Example 7 as a positive electrode material for lithium-ion batteries are shown in Table 14.

[0129] Table 14 Rate performance test results of Example 7

[0130]

[0131]

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A double-layered lithium-rich manganese-based positive electrode material, characterized in that: It comprises a base material, an inner layer covering material and an outer layer covering material, wherein the inner layer covering material is between the base material and the outer layer covering material; The matrix material is a lithium-rich manganese-based material, the inner coating material is Cu9S5, and the outer coating material is cerium aluminum oxide; the cerium aluminum oxide is in the form of small particle agglomerates embedded on the particle surface of the inner coating material; The inner coating material accounts for 0.5 wt.% to 1.5 wt.% of the base material; the outer coating material accounts for 2 wt.% to 4 wt.% of the base material.

2. The method for preparing the double-layer-coated lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The steps include: S1. The lithium-rich manganese-based material is dispersed in deionized water, stirred, dried, and calcined to obtain a pretreated lithium-rich manganese-based material; S2. The alcohol-soluble copper salt is dissolved in an ethanol solvent, and the pretreated lithium-rich manganese-based material is added and mixed to obtain a solution A; thioacetamide is dissolved in an ethanol solvent to obtain a solution B; The solution B is added dropwise to the solution A, and the obtained mixed solution is subjected to heat treatment. After cooling, the mixed solution is washed and dried. The dried material is placed in a heater, heated to 400-600° C. at a rate of 1-3° C. / min, and kept warm for 1.5-2.5 hours to obtain an inner-layer coated lithium-rich manganese-based material; S3. The inner-layer coated lithium-rich manganese-based material is dispersed in deionized water containing a water-soluble cerium salt and a water-soluble aluminum salt, and then ammonia water is added. The obtained mixed solution is dried, and the dried material is placed in a heater, heated to 400-600°C at a rate of 1-3°C / min, and kept warm for 1.5-2.5h to obtain a lithium-rich manganese-based positive electrode material with a double-layer surface coating.

3. The preparation method according to claim 2, characterized in that: In step S2, the alcohol-soluble copper salt is CuCl2·2H2O.

4. The preparation method according to claim 2, characterized in that In step S3, the water-soluble cerium salt is Ce(NO3)3·6H2O; the water-soluble aluminum salt is Al(NO3)3·9H2O.

5. The preparation method according to claim 2, characterized in that: In step S1, the weight ratio of the lithium-rich manganese-based material to deionized water is 1:(6-10).

6. The preparation method according to claim 2, characterized in that: In step S2, the weight ratio of the alcohol-soluble copper salt, thioacetamide and the pretreated lithium-rich manganese-based material is (1.5-3): (0.5-1.5):

100.

7. The preparation method according to claim 2, characterized in that: In step S3, the molar mass ratio of the water-soluble cerium salt, the water-soluble aluminum salt and the inner-layer coated lithium-rich manganese-based material is (0.45 mol to 0.6 mol): (0.45 mol to 0.6 mol): 10 g.

8. Use of the double-layer-coated lithium-rich manganese-based positive electrode material according to claim 1 as a positive electrode material for lithium-ion batteries.

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