Preparation method and application of lithium-rich manganese oxide cathode material with high capacity and long cycle stability

Abstract

A method for preparing and applying a high-capacity, long-cycle-stability lithium-rich manganese oxide cathode material is disclosed. The method involves mixing lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate, and citric acid monohydrate in deionized water, stirring until homogeneous, adding oleic acid to obtain a precursor solution, and spray-drying to obtain a precursor material. The precursor material is then heat-treated in air to obtain the high-capacity, long-cycle-stability lithium-rich manganese oxide cathode material, Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2. Its advantages are: lithium-rich manganese-based cathode materials modified by oleic acid and citric acid have a simple process, generate a spinel phase with high lithium-ion conductivity, and exhibit high specific capacity and excellent cycle performance at high current densities when applied to lithium-ion battery cathodes.

Description

Technical Field

[0001] This invention relates to the field of electrode materials for new energy vehicle batteries, specifically to a method for preparing and applying a lithium-rich manganese oxide cathode material with high capacity and long cycle stability. Background Technology

[0002] With the rapid development of new energy technologies, lithium-ion batteries play a crucial role in electric vehicles. However, although the energy density of existing lithium-ion batteries has reached nearly 300Wh / kg, it still cannot meet the growing demand for power batteries in new energy vehicles. The cathode, as a vital component of lithium-ion batteries, has a significant impact on battery performance, cost-effectiveness, lifespan, and safety.

[0003] Lithium-rich manganese oxides (MNOs) offer higher theoretical specific capacity and energy density due to their unique anionic and cation redox reactions, making them a promising cathode material for next-generation lithium-ion batteries. However, in practical applications, MNOs face challenges such as low initial coulombic efficiency, poor cycle performance, and suboptimal rate performance. These challenges are primarily caused by phase transitions in MNO electrode materials, poor interactions between the MNO electrode and the electrolyte, and irreversible oxygen release during charge and discharge of MNO-based cathode materials. Therefore, improving the structural stability of MNOs has become a major research direction.

[0004] Currently, improving the structural stability of lithium-rich manganese oxides mainly involves elemental doping and surface coating modification. CN118899424A discloses "A modified lithium-rich manganese-based cathode material and its preparation method and application," which prepares a phosphorus-doped and rGO-coated lithium-rich manganese-based material comprising a core and a coating layer on the core surface. By doping with phosphorus and coating with rGO, the lithium-rich manganese-based precursor can reduce the migration of transition metal ions, improve structural stability, and also form oxygen vacancies in the material, preventing oxygen escape. Simultaneously, it increases electron transfer channels, improves conductivity, and thus increases the material's capacity. CN118684271A discloses "A modified lithium-rich manganese-based cathode material and its preparation method and application," which involves dispersing a hydroxide precursor material of the lithium-rich manganese-based cathode material in an organic solvent, adding bismuth nitrate, tellurium dioxide, and organic ligands, and carrying out a hydrothermal reaction to obtain an intermediate product; the intermediate product is then mixed with a lithium source and sintered to obtain the coated and modified lithium-rich manganese-based cathode material. Modified lithium-rich manganese-based cathode materials exhibit good structural stability and rapid lithium-ion insertion / extraction performance, resulting in higher capacity retention in batteries using these cathode materials. However, the aforementioned methods all involve introducing foreign atoms to reconstruct the surface of lithium-rich manganese. This can lead to surface segregation, resulting in an uneven reconstructed layer on the modified lithium-rich manganese oxide surface. Consequently, this leads to performance instability, cumbersome procedures, high production costs, and limitations hindering large-scale commercial applications. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing and applying a lithium-rich manganese oxide cathode material with high capacity and long cycle stability. The lithium-rich manganese-based cathode material modified by oleic acid and citric acid has a simple process, generates a spinel phase with high lithium-ion conductivity, has high specific capacity, and has excellent cycle performance at high current density.

[0006] The technical solution of this invention is:

[0007] A method for preparing a high-capacity and long-cycle-stability lithium-rich manganese oxide cathode material, characterized by: preparing a lithium-rich manganese oxide cathode material Li through a composite modification treatment with citric acid and oleic acid. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0008] Furthermore, it includes the following steps:

[0009] (1) Preparation of precursor solution

[0010] Lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate, and citric acid monohydrate were mixed and added to deionized water, stirred evenly, and then oleic acid was added to prepare the catalyst solution.

[0011] (2) Preparation of precursor materials

[0012] The precursor solution prepared in step (1) was spray-dried to obtain the precursor material;

[0013] (3) Preparation of cathode materials

[0014] The precursor material prepared in step (2) was heat-treated in air to obtain a high-capacity, long-cycle-stability lithium-rich manganese oxide cathode material, Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0015] Further, in step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, and manganese acetate tetrahydrate is 0.1872:0.0195:0.0195:0.081.

[0016] Furthermore, the total concentration of metal acetate in the precursor solution in step (1) is 0.15 mol / L.

[0017] Furthermore, in step (1), the stirring speed is 500 rpm, the time is 1 h, and the temperature is room temperature.

[0018] Furthermore, in step (1), the concentration of citric acid monohydrate in the precursor solution is 0.4 mol / L, and the volume of oleic acid added accounts for 0.5-3% of the volume of deionized water in the precursor solution.

[0019] Furthermore, in step (2), during spray drying, the inlet temperature of the spray dryer is 200-250℃, the outlet temperature is 110-115℃, and the feed rate is 1-2L / h.

[0020] Further preferred, in step (2), the spray drying inlet temperature is 230°C, the outlet temperature is 115°C, and the feed rate is 1L / h.

[0021] Furthermore, the heat treatment conditions in step (3) are as follows: in an air atmosphere, the temperature is increased to 1000℃ at a heating rate of 3℃ / min and held for 20min.

[0022] Application of the lithium-rich manganese oxide cathode material prepared by the above-mentioned preparation method in the preparation of lithium-ion battery cathodes.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) By adjusting the amount of citric acid monohydrate added and combining it with oleic acid, the lithium-rich manganese material was composite modified without the need to introduce other external elements. This effectively reduced the particle size and increased the inter-crystal spacing. At the same time, a spinel phase with high electrical and lithium conductivity was generated, which significantly improved the lithium ion mobility. This enabled the material to exhibit excellent cycling performance and rate performance at high current density on the basis of high capacity.

[0025] (2) The lithium-ion batteries prepared using this modified material exhibit high capacity and excellent cycle stability at different current densities. For example, after 500 cycles at a current density of 200 mA / g, the capacity retention rate is as high as 94.98%, and at a current density of 1000 mA / g, the capacity is also 155.31 mAh / g, with good cycle stability.

[0026] (3) The preparation method of the lithium-rich manganese-based cathode material provided has a simple synthesis process and low material cost, which is conducive to reducing production costs; the modification method is green and efficient, which is conducive to large-scale production and application.

[0027] In summary, this patent achieves a significant improvement in the electrochemical performance of lithium-rich manganese-based cathode materials through an innovative modification method combining oleic acid and citric acid, along with a simple synthesis process. Attached Figure Description

[0028] Figure 1 The XRD patterns of the lithium-rich manganese oxide cathode materials prepared in Examples 1-2 and Comparative Example 1 of this invention are shown below.

[0029] Figure 2 The images show SEM images of the lithium-rich manganese oxide cathode materials prepared in Examples 1-2 and Comparative Example 1 of this invention.

[0030] Figure 3 XPS O1s images of lithium-rich manganese oxide cathode materials prepared in Examples 1-2 and Comparative Example 1 of this invention;

[0031] Figure 4 XPS Mn3s images of lithium-rich manganese oxide cathode materials prepared in Examples 1-2 and Comparative Example 1 of this invention;

[0032] Figure 5 The first charge-discharge diagrams are shown for the lithium-rich manganese oxide cathode materials prepared in Examples 1-3 and Comparative Example 1 of this invention.

[0033] Figure 6 The first charge-discharge diagrams of the lithium-rich manganese oxide cathode materials prepared in Example 1 and Comparative Examples 3-4 of this invention are shown.

[0034] Figure 7 These are the first charge-discharge diagrams of the lithium-rich manganese oxide cathode materials prepared in Comparative Examples 1 and 2 of this invention.

[0035] Figure 8 The cycling performance of lithium-rich manganese oxide cathode materials prepared in Examples 1-2 and Comparative Example 1 of this invention at a current density of 200 mA / g;

[0036] Figure 9 The cycling performance of lithium-rich manganese oxide cathode materials prepared in Example 1 and Comparative Examples 3-4 of this invention at a current density of 200 mA / g;

[0037] Figure 10 The cycling performance of lithium-rich manganese oxide cathode materials prepared in Comparative Examples 1 and 2 of this invention at a current density of 200 mA / g was obtained.

[0038] Figure 11 The rate performance diagrams are shown for the lithium-rich manganese oxide cathode materials prepared in Examples 1-2 and Comparative Example 1 of this invention.

[0039] Figure 12 The cycling performance of lithium-rich manganese oxide cathode materials prepared in Examples 1-2 and Comparative Example 1 of this invention is shown at a current density of 1000 mA / g. Detailed Implementation

[0040] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0041] Example 1

[0042] (1) Preparation of precursor solution

[0043] Weigh 19.098 g of lithium acetate dihydrate (4% wt excess lithium acetate dihydrate to compensate for lithium loss during heat treatment), 4.852 g of nickel acetate tetrahydrate, 4.857 g of cobalt acetate tetrahydrate and 19.852 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 84.056 g of citric acid monohydrate and 5 mL of oleic acid, and mechanically stir at 500 rpm for 1 h at room temperature to obtain the precursor solution;

[0044] (2) Preparation of precursor materials

[0045] The precursor solution obtained in step (1) is sent to a spray dryer using a peristaltic pump. The inlet temperature of the spray dryer is set to 230°C, the outlet temperature is set to 115°C, and the feed rate is set to 1L / h. Spray drying is performed to obtain the precursor material.

[0046] (3) Preparation of cathode materials

[0047] The precursor material obtained in step (2) was placed in an alumina crucible, wherein the alumina crucible was 120 mm long, 120 mm wide, and 50 mm high. The alumina crucible was placed in a box furnace and heated to 1000 °C at a heating rate of 3 °C / min under an air atmosphere. The mixture was then heat-treated at 1000 °C for 20 min to obtain the lithium-rich manganese oxide cathode material Li modified with oleic acid and citric acid. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2, denoted as LRO / 0.4mol-0.5%.

[0048] Example 2

[0049] The preparation method is the same as in Example 1, except that 30 mL of oleic acid is added when preparing the precursor solution. The resulting modified cathode material is denoted as LRO / 0.4 mol-3%.

[0050] (1) Preparation of precursor solution

[0051] Weigh 19.098 g of lithium acetate dihydrate (4% wt excess lithium acetate dihydrate to compensate for lithium loss during heat treatment), 4.852 g of nickel acetate tetrahydrate, 4.857 g of cobalt acetate tetrahydrate and 19.852 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 84.056 g of citric acid monohydrate and 30 mL of oleic acid, and mechanically stir at 500 rpm for 1 h at room temperature to obtain the precursor solution;

[0052] (2) Preparation of precursor materials

[0053] The precursor solution obtained in step (1) is sent to a spray dryer using a peristaltic pump. The inlet temperature of the spray dryer is set to 230°C, the outlet temperature is set to 115°C, and the feed rate is set to 1L / h. Spray drying is performed to obtain the precursor material.

[0054] (3) Preparation of cathode materials

[0055] The precursor material obtained in step (2) was placed in an alumina crucible, wherein the alumina crucible was 120 mm long, 120 mm wide, and 50 mm high. The alumina crucible was placed in a box furnace and heated to 1000 °C at a heating rate of 3 °C / min under an air atmosphere. The mixture was then heat-treated at 1000 °C for 20 min to obtain the lithium-rich manganese oxide cathode material Li modified with oleic acid and citric acid. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0056] Example 3

[0057] The preparation method is the same as in Example 1, except that 10 mL of oleic acid is added when preparing the precursor solution. The resulting modified cathode material is denoted as LRO / 0.4 mol-1%.

[0058] (1) Preparation of precursor solution

[0059] Weigh 19.098 g of lithium acetate dihydrate (4% wt excess lithium acetate dihydrate to compensate for lithium loss during heat treatment), 4.852 g of nickel acetate tetrahydrate, 4.857 g of cobalt acetate tetrahydrate and 19.852 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 84.056 g of citric acid monohydrate and 10 mL of oleic acid, and mechanically stir at 500 rpm for 1 h at room temperature to obtain the precursor solution;

[0060] (2) Preparation of precursor materials

[0061] The precursor solution obtained in step (1) is sent to a spray dryer using a peristaltic pump. The inlet temperature of the spray dryer is set to 230°C, the outlet temperature is set to 115°C, and the feed rate is set to 1L / h. Spray drying is performed to obtain the precursor material.

[0062] (3) Preparation of cathode materials

[0063] The precursor material obtained in step (2) was placed in an alumina crucible, wherein the alumina crucible was 120 mm long, 120 mm wide, and 50 mm high. The alumina crucible was placed in a box furnace and heated to 1000 °C at a heating rate of 3 °C / min under an air atmosphere. The mixture was then heat-treated at 1000 °C for 20 min to obtain the lithium-rich manganese oxide cathode material Li modified with oleic acid and citric acid. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0064] Comparative Example 1 (without oleic acid)

[0065] (1) Preparation of precursor solution

[0066] Weigh 19.098 g of lithium acetate dihydrate, 4.852 g of nickel acetate tetrahydrate, 4.857 g of cobalt acetate tetrahydrate, and 19.852 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 84.056 g of citric acid monohydrate, and additionally add lithium acetate dihydrate at 4% of the mass fraction of lithium acetate dihydrate to compensate for lithium loss during heat treatment; mechanically stir at 500 rpm for 1 h at room temperature to obtain the precursor solution.

[0067] (2) Preparation of precursor materials

[0068] The precursor solution obtained in step (1) is sent to a spray dryer using a peristaltic pump. The inlet temperature of the spray dryer is set to 230°C, the outlet temperature is set to 115°C, and the feed rate is set to 1L / h. The precursor material is obtained by spray drying under high temperature and high pressure.

[0069] (3) Preparation of cathode materials

[0070] The precursor material obtained in step (2) was placed in an alumina crucible, wherein the alumina crucible was 120 mm long, 120 mm wide, and 50 mm high. The alumina crucible was placed in a box furnace and heated at 1000 °C for 20 min in air atmosphere at a heating rate of 3 °C / min to obtain Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 cathode material, denoted as LRO / 0.4mol.

[0071] Comparative Example 2: No oil-based acid added, but with increased citric acid monohydrate dosage.

[0072] The difference between this comparative example and Comparative Example 1 is that the amount of citric acid monohydrate added when preparing the precursor solution is 126.084 g, while the rest is the same as in Comparative Example 1. The resulting modified cathode material is denoted as LRO / 0.6 mol.

[0073] Comparative Example 3: Increase the amount of oleic acid used

[0074] The difference between this comparative example and Example 1 is that 40 ml of oleic acid was added when preparing the precursor solution. Otherwise, it was the same as Example 1. The resulting modified cathode material was denoted as LRO / 0.4mol-4%.

[0075] Comparative Example 4 increased the dosage of citric acid monohydrate

[0076] The difference between this comparative example and Comparative Example 1 is that the amount of citric acid monohydrate added when preparing the precursor solution is 126.084 g, and the amount of oleic acid added is 5 mL. The rest is the same as in Comparative Example 1. The modified cathode material obtained is denoted as LRO / 0.6mol-0.5%.

[0077] I. XRD Testing of Lithium-Rich Manganese-Based Cathode Materials of Examples 1, 2, and Comparative Example 1 of the Present Invention

[0078] XRD tests were performed on the lithium-rich manganese-based cathode materials prepared in Examples 1, 2, and 1 (Comparative Example 1). The basic structure of the lithium-rich manganese-based cathode materials is as follows: Figure 1 As shown. By Figure 1 It can be seen that the prepared lithium-rich manganese oxides correspond to the Li2MnO3 phase and the LiMO2 phase, respectively, indicating that the target product was successfully synthesized. After modification with citric acid and oleic acid, the peak position of (003) of LRO / 0.4mol-0.5% and LRO / 0.4mol-3% shifted to a lower angle, indicating that the interlayer spacing increased. At the same time, the peak at (101) of both LRO / 0.4mol-0.5% and LRO / 0.4mol-3% showed a spinel phase peak, indicating that the surface of the lithium-rich manganese cathode material was coated with a spinel phase layer after composite modification, which is beneficial to lithium ion transport and greatly improves its rate and cycle performance.

[0079] II. SEM Testing of Lithium-Rich Manganese-Based Cathode Materials in Examples 1, 2, and Comparative Example 1 of the Present Invention

[0080] SEM analysis was performed on the lithium-rich manganese-based cathode materials prepared in Examples 1, 2, and 1 (Comparative Example 1). The surface morphology and dimensions of the lithium-rich manganese-based cathode materials were measured as follows: Figure 2 As shown. By Figure 2 It can be seen that the smallest particle size of LRO / 0.4mol-0.5% is 260nm, indicating that when the citric acid concentration is 0.4mol / L, the addition of a small amount of oleic acid can reduce the particle size, which is particularly crucial for improving electrochemical performance.

[0081] III. XPS Testing of Lithium-Rich Manganese-Based Cathode Materials in Examples 1, 2, and Comparative Example 1 of the Present Invention

[0082] XPS tests were performed on the lithium-rich manganese-based cathode materials prepared in Examples 1, 2, and 1 (Comparative Example 1). The surface structures of the lithium-rich manganese-based cathode materials were tested as follows: Figure 3 , Figure 4 As shown. By Figure 3 , Figure 4 It can be seen that the oxygen vacancy content of the lithium-rich manganese-based cathode material prepared in the embodiments of the present invention has increased, with the increase in LRO / 0.4mol-0.5% being the most significant at 32.19%. The increase in oxygen vacancy helps to stabilize the lattice oxygen on the material surface. The average valence state of Mn was calculated to be LRO / 0.4mol (+3.776), LRO / 0.4mol-0.5% (+4.012), and LRO / 0.4mol-3% (+3.832). The increased valence state of Mn plays a role in stabilizing the structure. Among them, the valence state of LRO / 0.4mol-0.5% reaches +4. Combined with the spinel phase appearing in the (101) peak in XRD, it is speculated that Li4Mn5O is formed. 12 The high lithium-ion conductivity of the spinel phase improves capacity and cycle performance.

[0083] III. Electrochemical Performance Testing of Lithium-Rich Manganese-Based Cathode Materials in Examples 1, 2, and Comparative Examples 1-4 of the Present Invention

[0084] (1) Preparation of positive electrode sheet

[0085] The lithium-rich manganese-based cathode materials and Super P prepared in Examples 1, 2 and Comparative Examples 1-4 were weighed at a mass ratio of 8:1 and placed in a ball mill jar. Tungsten carbide grinding beads were added, and the mass ratio of balls to materials in the ball mill jar was 100:1. Alcohol was added as a dispersant. After ball milling for 6 hours, the mixture was dried in a drying oven to obtain mixture A.

[0086] Weigh 285 mg of mixture A and 1250 mg of 1.2% CMC solution, stir at room temperature for 2 h, sonicate for 2 h, stir again for 2 h, coat with a 0.15 μm scraper onto aluminum foil, place in a vacuum drying oven at 110 °C for 20 h, cut into electrodes with a diameter of 10 mm, and then transfer the cut electrodes to a vacuum oven at 115 °C for 10 h to dry for later use.

[0087] (2) Assemble CR2025 stainless steel button cells

[0088] Using lithium metal sheets as the negative electrode, 250 μL of LBC-3045I(G) commercial electrolyte was added. The CR2025 stainless steel button cell was assembled in a glove box filled with argon gas and with a moisture content of less than 0.01 ppm. Its charge and discharge performance was tested after standing at 45°C for 40 hours.

[0089] (3) Electrochemical performance testing of CR2025 stainless steel button cells

[0090] The battery cycle performance of Examples 1, 2 and Comparative Examples 1-4 was tested using constant current charge-discharge method. The test temperature was 25℃, the voltage window was 2.0-4.8V, and the test current densities were 0.1C, 0.2C, 0.5C, 1C, 2C, 5C and 10C, respectively, where 1C = 200mA / g.

[0091] like Figure 5-7 As shown, the lithium-ion battery prepared with the lithium-rich manganese oxide cathode material LRO / 0.4mol-0.5% in this invention exhibits a maximum initial discharge specific capacity of 303.90 mAh / g at a current density of 20 mA / g. The initial discharge specific capacities of LRO / 0.4mol-3%, LRO / 0.4mol-4%, LRO / 0.6mol-0.5%, LRO / 0.4mol, and LRO / 0.6mol are 274.13, 231.58, 269.97, 262.41, and 256.11 mAh / g, respectively, indicating that adding excessive oleic acid and increasing the concentration of citric acid will reduce the specific capacity.

[0092] like Figure 8-11 As shown, the lithium-ion battery prepared using the lithium-rich manganese oxide cathode material LRO / 0.4mol-0.5% of this invention exhibits a capacity retention of up to 94.98% after 500 cycles at a current density of 200 mA / g. The capacity retention rates of LRO / 0.4mol-4%, LRO / 0.6mol-0.5%, LRO / 0.4mol, and LRO / 0.6mol after 500 cycles at 200 mA / g are 75.02%, 71.62%, 83.79%, and 62.13%, respectively. This is mainly due to the increased interlayer spacing and the formation of the spinel phase, leading to rapid lithium-ion transport. The increased oxygen vacancy content modulates the surface electronic structure of the modified lithium-rich manganese cathode material, increasing the Mn valence state, reducing disproportionation reactions, preventing transition metal dissolution of the material structure, and improving cycle stability. The lithium-ion battery prepared using the lithium-rich manganese oxide cathode material LRO / 0.4mol-0.5% of this invention maintained excellent rate performance in rate tests at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C and 10C.

[0093] like Figure 12As shown, the increased surface oxygen vacancy defects after citric acid and oleic acid composite treatment lead to increased interlayer spacing due to electrostatic effects, and the formation of a spinel phase structure with high lithium-ion conductivity. This results in lithium-ion batteries prepared from the lithium-rich manganese oxide cathode material of this invention, using LRO / 0.4mol-0.5% and LRO / 0.4mol-3%, still providing capacities of 155.31 mAh / g and 135.75 mAh / g respectively at a current density of 1000 mA / g (the capacity of LRO / 0.4mol is 123.65 mAh / g). The lithium-ion battery assembled from the LRO / 0.4mol-0.5% sample exhibited a capacity retention of up to 77.35% after 500 cycles, demonstrating excellent rate performance.

[0094] The above are merely specific embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium-rich manganese oxide cathode material with high capacity and long cycle stability, characterized in that: Lithium-rich manganese oxide cathode material Li was prepared by composite modification with citric acid and oleic acid. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2, including the following steps: (1) Preparation of precursor solution Lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate, and citric acid monohydrate were mixed and added to deionized water, stirred evenly, and then oleic acid was added to prepare the catalyst solution. The concentration of citric acid monohydrate in the precursor solution is 0.4 mol / L, and the volume of oleic acid added accounts for 0.5-3% of the volume of deionized water in the precursor solution; (2) Preparation of precursor materials The precursor solution prepared in step (1) was spray-dried to obtain the precursor material; (3) Preparation of cathode materials The precursor material prepared in step (2) was heat-treated in air to obtain a high-capacity, long-cycle-stability lithium-rich manganese oxide cathode material, Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

2. The method for preparing the high-capacity and long-cycle-stability lithium-rich manganese oxide cathode material according to claim 1, characterized in that: The molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate in step (1) is 0.1872:0.0195:0.0195:0.

081.

3. The method for preparing the high-capacity and long-cycle-stability lithium-rich manganese oxide cathode material according to claim 1, characterized in that: The total concentration of metal acetate in the precursor solution in step (1) is 0.15 mol / L.

4. The method for preparing the high-capacity and long-cycle-stability lithium-rich manganese oxide cathode material according to claim 1, characterized in that: The stirring speed in step (1) is 500 rpm, the time is 1 hour, and the temperature is room temperature.

5. The method for preparing the high-capacity and long-cycle-stability lithium-rich manganese oxide cathode material according to claim 1, characterized in that: In step (2), the spray drying process involves an inlet temperature of 200-250℃, an outlet temperature of 110-115℃, and a feed rate of 1-2L / h.

6. The method for preparing the high-capacity and long-cycle-stability lithium-rich manganese oxide cathode material according to claim 5, characterized in that: In step (2), the spray drying process involves an inlet temperature of 230°C, an outlet temperature of 115°C, and a feed rate of 1L / h.

7. The method for preparing the high-capacity and long-cycle-stability lithium-rich manganese oxide cathode material according to claim 1, characterized in that: The heat treatment conditions in step (3) are as follows: in an air atmosphere, the temperature is increased to 1000℃ at a heating rate of 3℃ / min and held for 20min.

8. The application of a lithium-rich manganese oxide cathode material prepared by the preparation method as described in claim 1 in the preparation of a lithium-ion battery cathode.

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