Method for improving the structural stability of layered lithium-rich manganese-based oxide positive electrode materials for lithium-ion batteries

Abstract

The present invention belongs to the technical field of lithium-ion battery electrode material preparation, and relates to a method for improving the structural stability of layered lithium-rich manganese-based oxide positive electrode materials for lithium-ion batteries. Specifically, it relates to a method for preparing a lanthanum ion-modified lithium-rich manganese-based oxide positive electrode material and its application in lithium-ion battery positive electrode materials. The present invention discloses a method for preparing a lanthanum-modified lithium-rich manganese-based oxide positive electrode material, comprising the following steps: adding a nickel ion salt, a cobalt ion salt, a manganese ion salt, a lithium ion salt, and a lanthanum ion salt to deionized water; adding citric acid and ethylene glycol to the resulting mixed salt solution; placing the solution in a water bath at 60-90°C for 6-24 hours; placing the solution in a vacuum drying oven for constant temperature vacuum drying; and subjecting the resulting foamed precursor to a two-step heat treatment in sections to obtain a lanthanum-modified lithium-rich manganese-based oxide positive electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of lithium-ion battery electrode materials, and specifically relates to a method for preparing a lanthanum ion-modified lithium-rich manganese-based oxide positive electrode material and its application in lithium-ion battery positive electrode materials. Background Art

[0002] The decreasing global fossil energy and the rapid growth of society's demand for energy have forced people to focus on new energy sources such as clean wind energy, hydropower, and solar energy. The development of such new energy sources, which are affected by time, environment, and geographical factors, has prompted the development of energy storage technology. Lithium-ion batteries have attracted widespread attention due to their advantages such as high energy density, low self-discharge, no memory effect, and wide operating temperature range. As an important component of lithium-ion batteries, the performance, cost, and safety of positive electrode materials directly determine the commercial application of lithium-ion batteries. Currently, the more mature positive electrode materials are lithium iron phosphate and lithium cobalt oxide, and the new LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 The research on O2 ternary cathode materials is also becoming increasingly mature. However, compared with the mature graphite anode (372mAh g -1 ) compared to existing cathode materials, the capacity is mostly less than 200mAh g -1 , which seriously limits the further improvement of the energy density of lithium-ion batteries.

[0003] Layered lithium-rich manganese-based oxides have high discharge capacity and working voltage, and their energy density can reach nearly 1000Wh kg -1 , and its low price and high safety make it considered to be a very promising cathode material for the next generation of lithium-ion batteries. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) cathode material is LiMn 1 / 3 Ni 1 / 3 Co 1 / 3 The Li2MnO3 nanodomains are composed of two types of nanodomains, namely, Li2O2 (space group is R-3m) and Li2MnO3 (space group is C2 / m), and these two nanodomains have different redox activities. During the charging process, when the charging voltage is lower than 4.4V, the Li2O3 nanodomains are mainly released. + ions, while the C2 / m nanodomains do not evolve. +After the ions are released, the Coulomb repulsion of the lattice oxygen causes its lattice parameters to expand (mainly concentrated in the lattice parameter c), while the lattice parameters of the C2 / m nanodomain remain unchanged. The two continuous nanodomains undergo lattice mismatch, resulting in the accumulation of stress and strain, which in turn exacerbates the lattice oxygen loss and layered structure phase transition under high voltage. The lattice oxygen precipitated under high voltage is very likely to undergo side reactions with the electrolyte to generate acidic substances, which corrode the interface of the positive electrode material and continuously dissolve the transition metal elements, resulting in poor interface stability of the lithium-rich manganese-based oxide material. Poor interface stability and structural stability aggravate the attenuation of the discharge specific capacity and discharge voltage of the lithium-rich manganese-based oxide positive electrode during the charge and discharge cycle, resulting in a continuous decline in energy density and poor cycle stability.

[0004] Patents with publication numbers CN114864908A, CN103441252A, and CN103928664B respectively use corrosion-resistant fluorides, oxides, phosphates, and other materials to coat layered lithium-rich manganese-based oxide positive electrode particles. Although this modification method effectively alleviates the corrosion of the electrolyte on the positive electrode material and the appropriate coating layer can increase the interface transmission rate of lithium ions / electrons, it has little effect on suppressing the structural transformation problem. Moreover, during long-term charge and discharge cycles, the rigid coating layer is difficult to completely and tightly coat the layered lithium-rich manganese-based oxide positive electrode particles with changing volume, causing the coating layer to gradually fail. Lattice doping has also been widely studied as a modification method that can effectively stabilize the structure.

[0005] Patents with publication numbers CN113540458A and CN112599765A respectively use ions larger than Li + Alkali metal ions (Na + , K + ) replaces Li + Or the patents with publication numbers CN111987297A and CN113224290A are respectively 3+ 、Ti 4+ Plasma partially replaces transition metal ions, relying on increasing the energy barrier that transition metal ions cannot migrate to improve the stability of the layered structure, and Na + , K + The large-sized ions expand the interlayer spacing of the Li layer, promoting the + However, traditional coating and doping methods are difficult to solve the problem of different redox properties of the two nanodomains, and it is difficult to suppress the mismatch between the lattice parameters of the R-3m and C2 / m nanodomains during the charging process. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for improving the structural stability of layered lithium-rich manganese-based oxide positive electrode materials for lithium-ion batteries.

[0007] In order to solve the above problems, the present invention provides a method for preparing a lanthanum-modified lithium-rich manganese-based oxide positive electrode material, comprising the following steps:

[0008] S1. Add nickel ion salt, cobalt ion salt, manganese ion salt, lithium ion salt, and lanthanum ion salt to deionized water, and stir at room temperature until completely dissolved to obtain a mixed salt solution;

[0009] Nickel ion: cobalt ion: manganese ion: lithium ion = 0.13: 0.12-0.14: 0.53-0.55: (1.15-1.25) × 1.05 molar ratio;

[0010] The sum of nickel ions, cobalt ions and manganese ions is named transition metal ions, and the molar ratio of transition metal ions: lanthanum ions is 100-x:x, where x is 0.1 to 10 (preferably 1 to 10);

[0011] The sum of nickel ions, cobalt ions, manganese ions, lithium ions, and lanthanum ions is named as total metal ions;

[0012] S2. Add citric acid and ethylene glycol to the mixed salt solution obtained in S1, and mix and stir evenly at room temperature until the citric acid is completely dissolved;

[0013] The molar ratio of total metal ions: citric acid: ethylene glycol is 1: 0.1-5: 0.1-5 (preferably 1: 1.4-1.6: 1.4-1.6);

[0014] S3. Place the solution obtained in S2 in a water bath and keep it in a water bath at 60-90°C for 6-24 hours;

[0015] S4, placing the product obtained in S3 in a vacuum drying oven for constant temperature vacuum drying to obtain a foamy precursor;

[0016] S5. Under air atmosphere, the foam precursor obtained in S4 is subjected to a two-step heat treatment in sections to obtain a lanthanum-modified lithium-rich manganese-based oxide positive electrode material.

[0017] As an improvement to the preparation method of the lanthanum-modified lithium-rich manganese-based oxide positive electrode material of the present invention:

[0018] The nickel ion salt, cobalt ion salt, manganese ion salt, lithium ion salt, and lanthanum ion salt may be any of the following: nitrate, sulfate, acetate, and chloride.

[0019] As a further improvement to the method for preparing the lanthanum-modified lithium-rich manganese-based oxide positive electrode material of the present invention, in step S5:

[0020] The first step of heat treatment is performed at a temperature of 300 to 700°C, a heating rate of 1 to 7°C / min, and continuous heat treatment at this temperature for 4.5 to 24 hours;

[0021] The second step heat treatment temperature is 700-1000° C., the heating rate is 1-7° C. / min, and the heat treatment is continued at this temperature for 6-24 hours.

[0022] As a further improvement to the method for preparing the lanthanum-modified lithium-rich manganese-based oxide positive electrode material of the present invention, in step S4:

[0023] The vacuum drying temperature is 100 to 300° C., and the vacuum drying time is 6 to 24 hours.

[0024] As a further improvement of the preparation method of the lanthanum-modified lithium-rich manganese-based oxide positive electrode material of the present invention:

[0025] In step S1:

[0026] The molar ratio of nickel ion: cobalt ion: manganese ion: lithium ion = 0.13:0.13:0.54:(1.2×1.05);

[0027] (nickel ion + cobalt ion + manganese ion): lanthanum ion = 99:1 molar ratio;

[0028] In step S2:

[0029] (nickel ion + cobalt ion + manganese ion + lithium ion + lanthanum ion): citric acid: ethylene glycol = 1:1.5:1.5 molar ratio;

[0030] In step S5:

[0031] The first step of heat treatment is at a temperature of 500±20℃, a heating rate of 5±0.1℃ / min, and the heat treatment is continued at this temperature for 5±0.1 hours;

[0032] The second step heat treatment temperature is 900±20°C, the heating rate is 5±0.1°C / min, and the heat treatment is continued at this temperature for 12±0.1 hours.

[0033] The present invention also provides a method for improving the structural stability of layered lithium-rich manganese-based oxide positive electrode materials for lithium-ion batteries: the material obtained by any of the above methods is used as a positive electrode material for lithium-ion batteries.

[0034] High energy density is a well-known feature of lithium-rich manganese-based oxide cathode materials, but the structural stability of such high energy density cathode materials is relatively poor, which directly leads to the decline of electrochemical performance. Based on the above research, the present invention introduces lanthanum ions into LiMn 1 / 3 Ni 1 / 3 Co 1 / 3 The perovskite phase LaNiO3 is constructed in the O2 nanodomain as a pinning phase, and the pinning effect of LaNiO3 is used to suppress the LiMn 1 / 3 Ni 1 / 3 Co1 / 3 The lattice parameter expansion of the O2 nanodomains during low-voltage delithiation, coupled with the electrochemical and thermodynamic stability of LaNiO3, ensures its durability and reliability as a pinning phase. The lattice mismatch between continuous nanodomains is improved, alleviating the accumulation of stress and strain, thereby inhibiting lattice oxygen loss and layered structural phase transitions at high voltages, thereby achieving structural stability. The electrochemical properties of the structurally stable cathode material, such as initial coulombic efficiency and capacity / voltage cycling stability, are significantly improved. Furthermore, this simple and controllable synthesis method can effectively promote the commercial application of layered lithium-rich manganese-based oxide cathode materials in high-energy-density lithium-ion batteries.

[0035] That is, the present invention generates a new phase by adding La to stabilize the structure, thereby improving the electrochemical performance.

[0036] This invention offers the advantages of a simple and controllable preparation process, low cost, and excellent electrochemical performance. During the preparation process (which can employ a sol-gel method), the addition of a lanthanum salt yields a lanthanum-modified lithium-rich manganese-based oxide cathode material with outstanding cycling stability, improving both initial coulombic efficiency and capacity / voltage cycling stability.

[0037] The present invention has the following beneficial effects:

[0038] 1. The process of the present invention is simple and controllable, low cost and has excellent electrochemical performance;

[0039] 2. The pinning effect of the pinning phase constructed by lanthanum ions in the cathode material structure significantly improves the stability of the layered structure of the lanthanum ion-modified lithium-rich manganese-based oxide cathode material;

[0040] 3. When used as the positive electrode of lithium-ion batteries, the initial coulombic efficiency and capacity / voltage cycling stability are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0042] Figure 1 This is the X-ray diffraction pattern of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material prepared in Example 1.

[0043] Figure 2 3 is a scanning electron microscope image of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material prepared in Example 1.

[0044] Figure 3 This is a low-magnification transmission electron microscope image of the lanthanum ion-modified lithium-rich manganese-based oxide positive electrode material prepared in Example 1.

[0045] Figure 4This is a high-magnification transmission electron microscope image of the lanthanum ion-modified lithium-rich manganese-based oxide positive electrode material prepared in Example 1.

[0046] Figure 5 This is the first cycle charge and discharge curve of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material prepared in Example 1.

[0047] Figure 6 The discharge capacity cycle stability of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material prepared in Example 1.

[0048] Figure 7 It is the average discharge voltage cycle stability of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material prepared in Example 1.

[0049] Figure 8 This is the X-ray diffraction pattern of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material prepared in Example 2.

[0050] Figure 9 This is the first cycle charge and discharge curve of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material prepared in Example 2.

[0051] Figure 10 The discharge capacity cycle stability of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material prepared in Example 2.

[0052] Figure 11 It is the average discharge voltage cycle stability of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material prepared in Example 2.

[0053] Figure 12 This is the X-ray diffraction pattern of the unmodified lithium-rich manganese-based oxide positive electrode material prepared in Example 3.

[0054] Figure 13 This is the first cycle charge and discharge curve of the unmodified lithium-rich manganese-based oxide positive electrode material prepared in Example 3.

[0055] Figure 14 The discharge capacity cycle stability of the unmodified lithium-rich manganese-based oxide positive electrode material prepared in Example 3.

[0056] Figure 15 It is the average discharge voltage cycle stability of the unmodified lithium-rich manganese-based oxide positive electrode material prepared in Example 3. DETAILED DESCRIPTION

[0057] The present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto:

[0058] Note: Since Li will volatilize during high-temperature sintering, an additional 5wt% will be added on top of the stoichiometric amount to compensate for the volatilized Li. This is a common requirement in the industry.

[0059] Example 1: A method for preparing a lanthanum ion-modified lithium-rich manganese-based oxide positive electrode material (a method for improving the structural stability of layered lithium-rich manganese-based oxide positive electrode materials for lithium-ion batteries), comprising the following steps:

[0060] 1) Add 0.009780 mol nickel nitrate hexahydrate, 0.009780 mol cobalt nitrate hexahydrate, 0.040625 mol manganese nitrate (50 wt% deionized water solution), and 0.094792 mol lithium nitrate (5 wt% excess) to 100 ml of deionized water and stir at room temperature until completely dissolved;

[0061] Therefore, the molar ratio of nickel ion: cobalt ion: manganese ion: lithium ion = 0.13: 0.13: 0.54: (1.2 × 1.05);

[0062] Then, 0.000608 mol of lanthanum nitrate hexahydrate was added and stirred at room temperature until the lanthanum nitrate hexahydrate was completely dissolved to obtain a transparent and clear mixed salt solution;

[0063] Therefore, the molar ratio of (nickel ion+cobalt ion+manganese ion):lanthanum ion=99:1.

[0064] 2) Add 0.2333775 mol of citric acid and 0.2333775 mol of ethylene glycol to the mixed salt solution obtained in step 1), and mix and stir evenly at room temperature until the citric acid is completely dissolved;

[0065] Therefore, the molar ratio of (nickel ion + cobalt ion + manganese ion + lithium ion + lanthanum ion): citric acid: ethylene glycol = 1:1.5:1.5.

[0066] 3) The solution obtained in step 2) was placed in a water bath at 80° C. for 8 hours (the solution was also evaporated to dryness during the water bath);

[0067] 4) placing the product obtained in step 3) in a vacuum drying oven and drying it at 200° C. (vacuum degree of −0.1 MPa) for 8 hours to obtain a foam precursor;

[0068] 5) In an air atmosphere, the foam precursor is first heated to 500°C at a rate of 5°C / min and kept at this temperature for 5 hours, then heated to 900°C at a rate of 5°C / min and kept at this temperature for 12 hours to obtain a lanthanum ion modified lithium-rich manganese-based oxide positive electrode material.

[0069] The X-ray diffraction pattern of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material obtained in Example 1 is as follows: Figure 1 As shown in the scanning electron microscope image Figure 2 As shown, the low-magnification and high-magnification transmission electron microscope images are shown in Figure 2. Figure 3 and Figure 4 As shown. Figures 1 to 4 , we can know that: X-ray diffraction peaks show the typical structural characteristics of lithium-rich manganese-based oxides, and low-magnification electron microscopy shows a granular morphology with uniform size. High-magnification transmission electron microscopy images show a new LaNiO3 structure that grows coherently with the layered lithium-rich manganese-based oxide positive electrode. Figure 4 From the transmission electron microscope photos, we can see that the atoms are arranged in layers.

[0070] Experiment 1: The material obtained in Example 1 was used as a positive electrode material for a lithium-ion battery. The temperature of the environmental simulation device was set to 25°C. The battery was left at 25°C for 12 hours, charged to 4.8V at a constant current density, left to stand for 5 minutes, and discharged to 2.0V at a constant current density. The results were as follows:

[0071] 20mA g -1 At the current density of 100mAg, the initial coulombic efficiency in the first cycle of activation charge and discharge can reach 91.15%. -1 At the current density, after 200 cycles, the discharge capacity retention rate is 96.36%, and the average discharge voltage retention rate is 90.56%. Figures 5 to 7 shown.

[0072] Example 2: A method for preparing a lanthanum ion-modified lithium-rich manganese-based oxide positive electrode material, comprising the following steps:

[0073] 1) The amount of lanthanum nitrate hexahydrate in step 1) of Example 1 was changed from 0.000608 mol to 0.001861 mol, so that the molar ratio of (nickel ion + cobalt ion + manganese ion): lanthanum ion = 97:3;

[0074] The rest is the same as step 1) of Example 1.

[0075] 2) Add 0.235257 mol of citric acid and 0.235257 mol of ethylene glycol to the mixed salt solution obtained in step 1), and mix and stir evenly at room temperature until the citric acid is completely dissolved;

[0076] Therefore, the molar ratio of (nickel ion + cobalt ion + manganese ion + lithium ion + lanthanum ion): citric acid: ethylene glycol = 1:1.5:1.5.

[0077] Step 3) to Step 5) are equivalent to Step 3) to Step 5) of Example 1.

[0078] The X-ray diffraction pattern of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material obtained in Example 2 is as follows: Figure 8 shown.

[0079] According to the same detection method as Example 1, the results were as follows: -1 The first cycle activation coulombic efficiency at the current density is 87.62%. -1 At the current density, after 200 cycles, the discharge capacity retention rate is 86.70%, and the average discharge voltage retention rate is 89.73%. Figures 9 to 11 shown.

[0080] Example 3: A method for preparing a lanthanum ion-modified lithium-rich manganese-based oxide positive electrode material, comprising the following steps:

[0081] 1) The use of lanthanum nitrate hexahydrate was eliminated, i.e., the amount of lanthanum ions used was 0; the rest was identical to step 1) of Example 1.

[0082] 2) Add 0.2324655 mol of citric acid and 0.2324655 mol of ethylene glycol to the mixed salt solution obtained in step 1), and mix and stir evenly at room temperature until the citric acid is completely dissolved;

[0083] Therefore, the molar ratio of (nickel ion + cobalt ion + manganese ion + lithium ion): citric acid: ethylene glycol = 1:1.5:1.5.

[0084] Step 3) to Step 5) are equivalent to Step 3) to Step 5) of Example 1.

[0085] The X-ray diffraction pattern of the lanthanum ion modified lithium-rich manganese-based oxide positive electrode material obtained in Example 3 is as follows: Figure 12 shown.

[0086] According to the same detection method as Example 1, the results were as follows: -1 The first cycle activation coulombic efficiency at the current density is 82.11%. -1 At the current density, after 200 cycles, the discharge capacity retention rate is 72.22%, and the average discharge voltage retention rate is 84.81%. Figures 13 to 15 shown.

[0087] Example 4: A method for preparing a lanthanum ion-modified lithium-rich manganese-based oxide positive electrode material, comprising the following steps:

[0088] 1) The amount of lanthanum nitrate hexahydrate in step 1) of Example 1 was changed from 0.000608 mol to 0.006687 mol, so that the molar ratio of (nickel ion + cobalt ion + manganese ion): lanthanum ion = 90:10;

[0089] The rest is the same as step 1) of Example 1.

[0090] 2) Add 0.242496 mol of citric acid and 0.242496 mol of ethylene glycol to the mixed salt solution obtained in step 1), and mix and stir evenly at room temperature until the citric acid is completely dissolved;

[0091] Therefore, the molar ratio of (nickel ion + cobalt ion + manganese ion + lithium ion + lanthanum ion): citric acid: ethylene glycol = 1:1.5:1.5.

[0092] Step 3) to Step 5) are equivalent to Step 3) to Step 5) of Example 1.

[0093] According to the same detection method as Example 1, the results were as follows: -1 The first cycle activation coulombic efficiency at the current density is 83.45%, and at 100mAg -1 At the same current density, the discharge capacity retention rate is 81.72% after 200 cycles, and the average discharge voltage retention rate is 87.53%.

[0094] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples and is subject to numerous variations. All variations that can be directly derived or conceived by a person of ordinary skill in the art from the disclosure of the present invention are considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a lanthanum-modified lithium-rich manganese-based oxide positive electrode material, characterized in that The following steps are involved: S1. Add nickel ion salt, cobalt ion salt, manganese ion salt, lithium ion salt, and lanthanum ion salt to deionized water, and stir at room temperature until completely dissolved to obtain a mixed salt solution; Nickel ion: cobalt ion: manganese ion: lithium ion = 0.13: 0.12-0.14: 0.53-0.55: (1.15-1.25) × 1.05 molar ratio; The sum of nickel ions, cobalt ions and manganese ions is named transition metal ions, and the molar ratio of transition metal ions: lanthanum ions is 100-x:x, where x is 0.1 to 10; The sum of nickel ions, cobalt ions, manganese ions, lithium ions, and lanthanum ions is named as total metal ions; S2. Add citric acid and ethylene glycol to the mixed salt solution obtained in S1, and mix and stir evenly at room temperature until the citric acid is completely dissolved; The molar ratio of total metal ions: citric acid: ethylene glycol is 1: 0.1-5: 0.1-5; S3. Place the solution obtained in S2 in a water bath and keep it in a water bath at 60-90°C for 6-24 hours; S4, placing the product obtained in S3 in a vacuum drying oven for constant temperature vacuum drying to obtain a foamy precursor; S5. Under air atmosphere, the foam precursor obtained in S4 is subjected to a two-step heat treatment in sections to obtain a lanthanum-modified lithium-rich manganese-based oxide positive electrode material.

2. The method for preparing the lanthanum-modified lithium-rich manganese-based oxide positive electrode material according to claim 1, characterized in that: The nickel ion salt, cobalt ion salt, manganese ion salt, lithium ion salt, and lanthanum ion salt may be any of the following: nitrate, sulfate, acetate, and chloride.

3. The method for preparing the lanthanum-modified lithium-rich manganese-based oxide positive electrode material according to claim 2, characterized in that In step S5: The first step of heat treatment is performed at a temperature of 300 to 700°C, a heating rate of 1 to 7°C / min, and continuous heat treatment at this temperature for 4.5 to 24 hours; The second step heat treatment temperature is 700-1000° C., the heating rate is 1-7° C. / min, and the heat treatment is continued at this temperature for 6-24 hours.

4. The method for preparing the lanthanum-modified lithium-rich manganese-based oxide positive electrode material according to claim 3, characterized in that In step S4: The vacuum drying temperature is 100 to 300° C., and the vacuum drying time is 6 to 24 hours.

5. The method for preparing the lanthanum-modified lithium-rich manganese-based oxide positive electrode material according to any one of claims 1 to 4, characterized in that: In step S1: The molar ratio of nickel ion: cobalt ion: manganese ion: lithium ion = 0.13:0.13:0.54:(1.2×1.05); (nickel ion + cobalt ion + manganese ion): lanthanum ion = 99:1 molar ratio; In step S2: (nickel ion + cobalt ion + manganese ion + lithium ion + lanthanum ion): citric acid: ethylene glycol = 1:1.5:1.5 molar ratio; In step S5: The first step of heat treatment is at a temperature of 500±20℃, a heating rate of 5±0.1℃ / min, and the heat treatment is continued at this temperature for 5±0.1 hours; The second step heat treatment temperature is 900±20°C, the heating rate is 5±0.1°C / min, and the heat treatment is continued at this temperature for 12±0.1 hours.

6. A method for improving the structural stability of a layered lithium-rich manganese-based oxide cathode material for a lithium-ion battery, characterized in that: The material obtained by the method according to any one of claims 1 to 5 is applied to the positive electrode material of lithium-ion batteries.

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