Modified lithium-rich manganese-based positive electrode active material, preparation, application and lithium ion battery thereof

Abstract

This invention belongs to the field of lithium-ion battery cathode materials, specifically relating to a modified lithium-rich manganese-based cathode active material, its preparation, application, and lithium-ion batteries. The modified lithium-rich manganese-based cathode active material comprises a lithium-rich manganese-based material and a modifier, wherein the modifier is at least one of a compound of formula 1 ( ) and its oxides or salts. This invention discovers that the modifier of formula 1 can adapt to the physicochemical characteristics of the lithium-rich manganese-based material, fundamentally suppressing interfacial side reactions of the lithium-rich manganese-based material, and significantly improving its cycle stability and voltage retention. The resulting material exhibits excellent electrochemical performance, structural stability, high average operating voltage, and good cycle stability, especially at high temperatures (below 200℃), and rate performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode materials, specifically relating to modified lithium-rich manganese-based cathode active materials. Background Technology

[0002] Lithium-rich manganese-based cathode materials (such as Li) 1.5 Mn 0.667 Ni 0.333 O2 (O2) has become one of the core candidate materials for next-generation high-energy-density lithium-ion batteries due to its advantages such as ultra-high specific capacity (>250mAh / g), low cost, and environmental friendliness. However, this material suffers from serious structural stability problems during cycling: lattice oxygen is easily released during charging and discharging, generating superoxide anion radicals (O2). - ), triggering the oxidative decomposition of the electrolyte; transition metal ions (especially Mn) 3+ It is prone to disproportionation and dissolution, leading to an irreversible transformation of the layered structure into the spinel / rock salt phase. This results in rapid voltage decay and short cycle life, severely hindering its commercial application.

[0003] In existing technologies, modification methods for lithium-rich manganese-based materials mainly include surface coating and elemental doping. Surface coating is the most direct and effective method, and commonly used coating materials are inorganic compounds such as carbon materials, alumina, and titanium dioxide, or simple organic salts. For example, publication number CN119674043A discloses a LiAlO2-coated lithium-rich manganese-based material, its preparation method, and its application. Chinese patent document publication number CN120767313A discloses a cathode material, a cathode electrode containing the material, and an electrochemical device. The cathode material includes a lithium-rich manganese-based cathode material and a coating layer present on the lithium-rich manganese-based cathode material; the coating layer is a MOF structure layer containing C, N, and O elements, formed by mixing the lithium-rich manganese-based cathode material with organic ligands and using a low-pressure vapor deposition method to coordinate the organic ligands with metal ions on the surface of the lithium-rich manganese-based cathode material.

[0004] Although existing technologies disclose some lithium-rich manganese-based modification schemes, the existing methods mainly reduce the contact between the electrode and the electrolyte through physical barriers, which cannot eliminate the reactive oxygen free radicals generated during the cycle, nor can they fundamentally inhibit the dissolution of transition metal ions. Although some organic coating materials have certain antioxidant properties, they have problems such as single function, weak bonding with the positive electrode interface, and easy decomposition and gas generation at high temperatures, and cannot simultaneously achieve structural stability and electrochemical performance improvement.

[0005] Therefore, developing a technology that combines the triple functions of "reactive oxygen radical scavenging, transition metal ion chelation, and interface stabilization" to address the cyclic failure problem of lithium-rich manganese-based materials through synergistic effects has become a key technological requirement in this field. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a modified lithium-rich manganese-based cathode active material, aiming to provide a novel lithium-rich manganese-based material that adapts to the characteristics of lithium-rich manganese-based materials, can fundamentally solve its interfacial side reactions, and improve its long-cycle performance.

[0007] The second objective of this invention is to provide a method for preparing and applying the modified lithium-rich manganese-based positive electrode active material.

[0008] A third objective of this invention is to provide a lithium-ion battery comprising the modified lithium-rich manganese-based cathode active material.

[0009] A modified lithium-rich manganese-based positive electrode active material comprises a lithium-rich manganese-based material and a modifier, wherein the modifier is at least one of a compound of formula 1 and its oxides or salts;

[0010] Formula 1

[0011] R1 and R2 are H, C1-C6 alkyl, phenyl, or C1-C6 hydroxyalkyl; R3 is H, C1-C6 alkyl, or C1-C6 alkoxy.

[0012] This invention reveals that the modifier of Formula 1 can adapt to the physicochemical characteristics of lithium-rich manganese-based cathode materials, fundamentally suppressing interfacial side reactions in these materials and significantly improving their cycle stability and voltage retention. The resulting material exhibits excellent electrochemical performance, structural stability, and a high average operating voltage, demonstrating good cycle stability, especially at high temperatures (below 200℃), and rate performance.

[0013] In this invention, the chemical formula of the lithium-rich manganese-based material can be: xLi₂MnO₃·(1-x)LiMO₂, where M is at least one of Ni, Co, and Mn; <x<1。

[0014] Alternatively, x can be 0.1~0.9; more specifically, 0.2~0.8; and even more specifically, 0.3~0.6; for example, the lithium-rich manganese-based material can be Li 1.5 Mn 0.667 Ni 0.333 O2 (that is, 0.5Li2MnO3·0.5LiNi) 0.5 Mn 0.5 O2).

[0015] In this invention, the modifier includes at least one of Formula 1A, Formula 1B, Formula 1C, and Formula 1D;

[0016] ;

[0017] R4 is a C1-C6 alkyl group.

[0018] Preferably, the modifier comprises Formula 1A. Studies have shown that using the preferred Formula 1A as a modifier helps optimize the physicochemical structure of lithium-rich manganese-based materials, further enhancing the high-voltage characteristics and high-temperature cycling stability of these materials.

[0019] Preferably, the modifier comprises two or more combinations of modifiers from Formula 1A, Formula 1B, Formula 1C, and Formula 1D. In this invention, the preferred composite modifier can achieve a synergistic effect through the complementarity of its molecular structure and function: it can more comprehensively anchor the transition metal active sites on the surface of lithium-rich manganese-based materials, more efficiently scavenge reactive oxygen free radicals generated during cycling, and simultaneously construct a denser and more stable composite interface layer. Compared to coating with a single modifier, it can further significantly improve the cycling stability, voltage retention rate, and electrochemical performance of lithium-rich manganese-based materials under high-temperature / high-rate conditions.

[0020] Preferably, the modifier comprises Formula 1A and Formula 1C in a mass ratio of 1:0.5~2; more preferably 1:0.5~1.5; or comprises Formula 1A and Formula 1B in a mass ratio of 1:0.5~2; more preferably 1:0.5~1.5. Studies have shown that with this preferred composite modifier, the compactness of the composite coating layer can be ensured without affecting the rapid diffusion of Li⁺, based on the synergistic effect of intermolecular hydrogen bonds and π-π stacking.

[0021] In this invention, the modifier is coated on the surface of the lithium-rich manganese-based material; wherein the thickness of the coating layer is 1~10 nm.

[0022] In this invention, the modifier in the modified lithium-rich manganese-based cathode active material is 0.5% to 3% of the mass of the lithium-rich manganese-based material (lithium-rich manganese-based cathode material); it can be further 0.6% to 2%; and even further 1% to 1.5%.

[0023] The present invention also provides a method for preparing the modified lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based material is mixed and modified with a modifier.

[0024] The preparation method of the present invention involves mixing the lithium-rich manganese-based material and the modifier in a liquid phase, then removing the solvent, and then heat-treating at a low temperature of 150~200℃ to obtain the modified lithium-rich manganese-based positive electrode active material.

[0025] In this invention, the solvent used for liquid-phase mixing includes at least one of water and C1-C4 alcohols;

[0026] Preferably, the solvent removal method is evaporation;

[0027] Preferably, the atmosphere during the low-temperature heat treatment process is a protective atmosphere; for example, at least one of nitrogen or a rare gas.

[0028] Preferably, the low-temperature heat treatment time is 1 to 10 hours; more preferably, it can be 3 to 6 hours.

[0029] Preferably, the modifier is a composite modifier. Research in this invention shows that the composite modifier can further enhance the modification effect of lithium-rich manganese-based compounds, and can further enhance their high-voltage and high-temperature stability.

[0030] More preferably, the mixed modification includes a two-stage modification process, the steps of which are: first, mixing the lithium-rich manganese-based material and the first modifier in liquid phase, then desolventizing, and then performing a first-stage low-temperature heat treatment at 150~200℃ to obtain a modified material; then mixing the modified material and the second modifier in liquid phase, then desolventizing, and then performing a second-stage low-temperature heat treatment at 150~200℃ to obtain the final product; the first modifier and the second modifier are different modifiers in Formula 1. More specifically, the first modifier is Formula 1A, and the second modifier includes at least one of Formula 1B, Formula 1C, and Formula 1D. The weight ratio of the first modifier to the second modifier can be 1:0.5~2.

[0031] This invention has found that the two-stage modification process described above helps to further improve the physicochemical structure of lithium-rich manganese-based materials and further enhance their stability under high voltage and high temperature.

[0032] An optional preparation method of the present invention is as follows:

[0033] (I) Raw material mixing: The lithium-rich manganese-based material bulk powder and the modifier of Formula 1 are mixed at a mass ratio of 100:0.5~3 and uniformly dispersed by liquid phase mixing. Ethanol or deionized water is used as solvent during liquid phase mixing. The two are stirred at 25~70℃ for 1~4 hours, and then the solvent is evaporated to obtain mixed powder.

[0034] (II) Low-temperature heat treatment: After grinding the mixed powder obtained in step (I) for 5 to 10 minutes, place it in a tube furnace and heat it to 150 to 200°C at a rate of 1 to 3°C / min under an inert atmosphere (N2 or Ar). Hold it at that temperature for 3 to 6 hours and then cool it naturally to room temperature to obtain the lithium-rich manganese-based cathode material coated and modified by the modifier of Formula 1.

[0035] The present invention also provides an application of a modified lithium-rich manganese-based cathode active material, which is used as a cathode active material in the preparation of lithium-ion batteries.

[0036] The present invention also provides a lithium-ion battery, wherein the positive electrode contains the modified lithium-rich manganese-based positive electrode active material described in the present invention.

[0037] The lithium-ion battery of the present invention comprises the modified lithium-rich manganese-based positive electrode active material of the present invention in its positive electrode, and the remaining parts and battery structure can adopt conventional technical solutions in the field.

[0038] Beneficial effects

[0039] 1. Strong functional synergy: For the first time, the modifier of Formula 1 is applied to the modification of lithium-rich manganese-based materials. Through the triple action of "free radical scavenging + metal chelation + interface stabilization", it solves the problem of material cycle failure from the root. After 200 cycles, the capacity retention rate is ≥88% and the voltage decay rate is reduced by more than 40%.

[0040] In the preferred composite modifier scheme, based on the functional complementarity and enhancement between composite modifier molecules, transition metal ions can be anchored more comprehensively and reactive oxygen free radicals can be scavenged more efficiently, a denser composite interface layer can be constructed, the capacity retention rate after 200 cycles is ≥90%, the capacity retention rate after 300 cycles at 50℃ is ≥93%, and the voltage decay rate is reduced by more than 15% compared with single coating.

[0041] 2. Mild process: The heat treatment temperature is only 150~200℃, which is far lower than the structural stability temperature (<400℃) of lithium-rich manganese-based materials, thus avoiding damage to the material's structure. In addition, it also avoids the high-temperature carbonization of the modifier and does not require complex equipment, making it suitable for large-scale production. The invention uses a low-temperature heat treatment of 150~200℃, which effectively reduces energy consumption compared to existing high-temperature coating strategies and has cost advantages.

[0042] 3. Good compatibility: The coating layer is tightly bonded to the interface of the lithium-rich manganese-based cathode material, which does not affect the Li⁺ diffusion rate. The rate performance (1C / 5C) of the modified material is maintained at ≥90%. The composite interface layer formed by the synergistic coating constructs a continuous Li⁺ transport channel through intermolecular hydrogen bonds and π-π stacking. The rate performance (1C / 5C) of the modified material is maintained at ≥92%, and the discharge specific capacity at 5C rate is improved by more than 10% compared with the single coating.

[0043] 4. High safety: Formula 1 modifier has good thermal stability and does not decompose and produce gas within the battery operating temperature range. Moreover, the reaction products are free of harmful impurities, which significantly improves the thermal safety performance of the battery. The hydrogen bond and π-π stacking effect between the two modifier molecules further improve the thermal stability and structural density of the composite coating layer. Even at a high temperature of 50℃, there is still no obvious decomposition and gas production, and the battery thermal runaway initiation temperature is increased by more than 10℃.

[0044] 5. Raw materials are readily available and the ratio is controllable: The modifier is inexpensive, and the ratio of the two modifiers can be flexibly adjusted according to the specific composition of the lithium-rich manganese-based cathode material (such as the content of Li2MnO3 and the proportion of transition metals) and the application scenario (power battery / energy storage battery). It has strong adaptability and can achieve customized modification. Attached Figure Description

[0045] Figure 1 The XRD patterns of the modified material in step 2 of Example 1 and the material in Comparative Example 1 (i.e., the lithium-rich manganese-based cathode material prepared in step 1 of Example 1) are shown.

[0046] Figure 2 This is a comparison chart of the cycle performance of the material modified in step 2 of Example 1 and the material in Comparative Example 1;

[0047] Figure 3 The magnification comparison spectrum is shown between the modified material in step 2 of Example 1 and the material in Comparative Example 1.

[0048] Figure 4 This is a comparison graph of the high-temperature cycling performance of the material modified in step 2 of Example 1 and the material in Comparative Example 1. Detailed Implementation

[0049] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following specific examples. Unless otherwise specified, the methods used in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials can be obtained commercially.

[0050] In this invention, the precursor can be a precursor containing Mn and Ni, optionally containing Co hydroxides, carbonates, etc., suitable for lithium-rich manganese-based cathodes.

[0051] In this invention, the lithium-rich manganese-based cathode material before modification can be any lithium-rich manganese-based cathode material, and can be prepared based on existing methods or purchased from existing commercial products.

[0052] Example 1

[0053] Step 1: Li 1.5 Mn 0.667 Ni 0.333 O2 synthesis

[0054] The lithium-rich material precursor (TM, manganese oxide, and nickel oxide) was mixed with lithium carbonate in a stoichiometric ratio of TM:Li = 1:1.5. After homogenization, the mixture was heat-treated at 500°C for 5 hours, followed by heat treatment at 900°C for 12 hours, and then allowed to cool naturally to obtain the lithium-rich manganese-based cathode material Li. 1.5 Mn 0.667 Ni 0.333 O2.

[0055] Step 2: Add 1g of lithium-rich manganese-based cathode material Li 1.5 Mn 0.667 Ni 0.333O2 and 0.01 g of modifier (Formula 1A) were mixed in deionized water, and the deionized water was evaporated to dryness at 70 °C. The resulting solid powder was ground and then heated to 180 °C at a rate of 2 °C / min in an inert atmosphere (Ar), and held at that temperature for 5 h to obtain the modified material. The XRD pattern of the material is shown in [reference needed]. Figure 1 .

[0056] The active material (in this case, the modified lithium-rich manganese-based cathode material obtained in step 2), acetylene black, and PVDF were mixed uniformly at a mass ratio of 8:1:1 to form a slurry. This slurry was then uniformly coated onto aluminum foil and cut into cathode sheets with a diameter of 12 mm and a thickness of 100 μm. A 1.5 μm lithium metal sheet was used as the anode, Celgard 2500 was used as the separator, and a 1 M LiPF6 EC / DMC (volume ratio 1:1) solution was used as the electrolyte. The cells were assembled into a CR2016 type button cell in an argon-filled glove box. This is the battery of Example 1.

[0057] Comparative Example 1

[0058] Compared to Example 1, the only difference is that step 2 was omitted, and the Li prepared in step 1 was used directly. 1.5 Mn 0.667 Ni 0.333 O2 was used as the active material. Assembly and testing were performed according to the method in Example 1.

[0059] Electrochemical performance testing:

[0060] Test 1: Loop

[0061] The above-mentioned batteries were subjected to charge-discharge cycle tests using the Landian CT2001A battery testing system. The voltage range was 2~4.8V, the test temperature was 30℃, and the test rate was 1C.

[0062] Figure 2 The graph compares the cycling performance of the modified lithium-rich manganese-based cathode material and the material of Comparative Example 1 at a current density of 1C. The initial capacity at 1C is 234 mAh / g, and the capacity retention rate after 200 cycles is 88.36%, higher than that of Comparative Example 1 (64.34%). The average voltage of the battery in Example 1 is approximately 3.75V, with a voltage retention rate of 86%, while the average voltage of the battery in Comparative Example 1 is approximately 3.60V, with a voltage retention rate of 65%.

[0063] Test 2: Multiplier

[0064] The above-mentioned batteries were tested for rate performance using the Landian CT2001A battery testing system, with a voltage range of 2~4.65V and a test temperature of 30℃.

[0065] Figure 3The graph shows a comparison of the rate performance of the modified lithium-rich manganese-based cathode material with that of Comparative Example 1. With increasing current density, the discharge specific capacity of Comparative Example 1 decreases significantly, reaching approximately 145 mAh / g at 2C and only about 125 mAh / g at 5C. In contrast, the coating modification achieves a significant improvement. Example 1 exhibits a discharge specific capacity of approximately 220 mAh / g at 2C and approximately 180 mAh / g at 5C, demonstrating excellent high-rate charge-discharge performance. Furthermore, when the charge-discharge cycle returns to a current density of 0.1C, the discharge specific capacity remains essentially the same as the initial discharge specific capacity. This indicates that the material's structure is not damaged after high-rate discharge, and the coating layer plays a role in stabilizing the structure to a certain extent, demonstrating its good structural stability.

[0066] Test 3: High-temperature cycling

[0067] The batteries were subjected to charge-discharge cycle tests using the Landian CT2001A battery testing system. The voltage range was 2~4.8V, the test temperature was 50℃, and the test rate was 1C.

[0068] Figure 4 The graph shows a comparison of the cycling performance of the modified lithium-rich manganese-based cathode material of Example 1 and the lithium-rich manganese-based cathode material of Comparative Example 1 at a current density of 1C. The initial capacity of the modified material at 1C is 244 mAh / g, and the capacity retention rate after 300 cycles is 91.44%, which is higher than that of the comparative example (75.73%). It can be seen that the coating strategy of the modifier of Formula 1 in this invention can significantly improve the high-temperature long-cycle performance of the lithium-rich manganese-based cathode material.

[0069] Example 2

[0070] Compared with Example 1, the only difference is that in step 2, the modifier is changed to Formula 1C (R4 is methyl). All other preparation parameters, battery assembly methods, and electrochemical performance testing conditions are the same as in Example 1. The test results are shown in Table 1.

[0071] Example 3

[0072] Compared with Example 1, the only difference is that in step 2, the modifier is changed to Formula 1B. All other preparation parameters, battery assembly methods, and electrochemical performance testing conditions are the same as in Example 1. The test results are shown in Table 1.

[0073] Example 4

[0074] Compared with Example 1, the only difference is that in step 2, the modifier is changed to Formula 1D. All other preparation parameters, battery assembly methods, and electrochemical performance testing conditions are the same as in Example 1. The test results are shown in Table 1.

[0075] Example 5

[0076] Compared to Example 1, the only difference is that in step 2, the modifier is 1.5% of the mass of the lithium-rich manganese-based cathode material, the heat treatment temperature is 160°C, and the time is 6 hours. All other preparation parameters, battery assembly methods, and electrochemical performance testing conditions are the same as in Example 1. The test results are shown in Table 1.

[0077] Example 6

[0078] Compared with Example 1, the only difference is that the modifier in step 2 is Formula 1A and Formula 1C in a mass ratio of 3:2. The total amount of modifier, as well as the remaining preparation parameters, battery assembly method, and electrochemical performance testing conditions, are the same as in Example 1. The test results are shown in Table 1.

[0079] Example 7

[0080] Compared with Example 1, the only difference is that the modifier in step 2 is Formula 1A and Formula 1B in a mass ratio of 1:1. The total amount of modifier, as well as the remaining preparation parameters, battery assembly method, and electrochemical performance testing conditions, are the same as in Example 1. The test results are shown in Table 1.

[0081] Example 8

[0082] Compared to Example 7, the only difference is that step 2 is a two-step coating process, which includes:

[0083] Step 2.1: First Modification

[0084] The lithium-rich manganese-based cathode material (prepared in step 1) and the first modifier (Formula 1A) were coated in the first stage, wherein the evaporation and heat treatment temperatures were the same as in Example 1, and the heat treatment time was 2 hours; the first modified material was obtained.

[0085] Step 2.2: Second Modification

[0086] The first modified material and the second modified agent (Formula 1B) are coated in a second stage, wherein the evaporation and heat treatment temperatures are the same as in Example 1, and the heat treatment time is 3 hours; thus, the final modified material is obtained.

[0087] The mass ratio of the first modifier to the second modifier is 1:1, and the total amount used is the same as the total modifier in Example 7. The other preparation parameters, battery assembly method and electrochemical performance test conditions are the same as in Example 7.

[0088] Comparative Example 2

[0089] Compared to Example 1, the only difference is that in step 2, the modifier is replaced with comparative formula a ( The remaining preparation parameters, battery assembly methods, and electrochemical performance testing conditions are the same as in Example 1.

[0090] Comparative Example 3

[0091] Compared to Example 1, the only difference is that in step 2, the modifier is replaced with comparative formula b ( The remaining preparation parameters, battery assembly methods, and electrochemical performance testing conditions are the same as in Example 1.

[0092] Comparative Example 4

[0093] Compared to Example 1, the only difference is that in step 2, the modifier is replaced with comparative formula c ( The remaining preparation parameters, battery assembly methods, and electrochemical performance testing conditions are the same as in Example 1.

[0094]

[0095] In summary, the modifier of Formula 1 can adapt to the physicochemical characteristics of lithium-rich manganese-based cathode materials, and can fundamentally suppress interfacial side reactions in lithium-rich manganese-based cathode materials, significantly improving their cycle stability and voltage retention. The modified material exhibits excellent electrochemical performance, structural stability, and high average operating voltage, while also possessing good cycle stability and high-temperature tolerance (operating temperature less than 200℃), with particularly outstanding high-temperature cycle stability.

[0096] Furthermore, as can be seen from Examples 1 to 4, better electrochemical performance can be obtained by using Formula 1A as a modifier.

[0097] As can be seen from Examples 1 and 6 to 8, the modified agent of the combination can further enhance the synergistic effect of modification, which helps to further improve the voltage stability and high-temperature cycling performance of lithium-rich manganese-based cathode materials. In particular, the two-stage modification process fully utilizes the synergistic modification effect and significantly optimizes the high voltage retention, high-temperature stability and long-cycle performance of the material.

Claims

1. A modified lithium-rich manganese-based cathode active material, comprising a lithium-rich manganese-based material and a modifier, characterized in that, The modifier is at least one of the compounds of formula 1 and their oxides and salts; Formula 1; R1 and R2 are H, C1-C6 alkyl, phenyl, or C1-C6 hydroxyalkyl; R3 is H, C1-C6 alkyl, or C1-C6 alkoxy.

2. The modified lithium-rich manganese-based cathode active material as described in claim 1, characterized in that, The chemical formula of the lithium-rich manganese-based material is: xLi₂MnO₃·(1-x)LiMO₂, where M is at least one of Ni, Co, and Mn; <x<1; Preferably, the lithium-rich manganese-based material is Li 1.5 Mn 0.667 Ni 0.333 O2.

3. The modified lithium-rich manganese-based cathode active material as described in claim 1, characterized in that, The modifier includes at least one of Formula 1A, Formula 1B, Formula 1C, and Formula 1D; ； R4 is a C1~C6 alkyl group; Preferably, the modifier comprises Formula 1A and Formula 1C in a mass ratio of 1:0.5~2; or comprises Formula 1A and Formula 1B in a mass ratio of 1:0.5~2.

4. The modified lithium-rich manganese-based cathode active material as described in claim 1, characterized in that, The modifier is coated on the surface of the lithium-rich manganese-based material; wherein the thickness of the coating layer is 1~10nm.

5. The modified lithium-rich manganese-based cathode active material according to any one of claims 1 to 4, characterized in that, In the modified lithium-rich manganese-based cathode active material, the modifier is 0.5% to 3% of the mass of the lithium-rich manganese-based material.

6. A method for preparing the modified lithium-rich manganese-based positive electrode active material according to any one of claims 1 to 5, characterized in that, The lithium-rich manganese-based cathode material was obtained by mixing and modifying it with a modifier.

7. The preparation method of the modified lithium-rich manganese-based positive electrode active material as described in claim 6, characterized in that, The lithium-rich manganese-based material and the modifier are mixed in the liquid phase, then the solvent is removed, and then the mixture is subjected to low-temperature heat treatment at 150~200℃ to obtain the modified lithium-rich manganese-based positive electrode active material.

8. The method for preparing the modified lithium-rich manganese-based positive electrode active material as described in claim 7, characterized in that, The solvent used for liquid-phase mixing includes at least one of deionized water and C1-C4 alcohols; Preferably, the solvent removal method is evaporation; Preferably, the atmosphere during the low-temperature heat treatment process is a protective atmosphere; Preferably, the low-temperature heat treatment time is 1~10h; more preferably, it can be 3~6h. Preferably, the mixed modification includes a two-stage modification process, the steps of which are: firstly mixing the lithium-rich manganese-based material and the first modifier in liquid phase, then desolventizing, and then performing a first-stage low-temperature heat treatment at a temperature of 150~200℃ to obtain a modified material. The modified material and the second modifier are then mixed in liquid phase, followed by desolventizing, and then subjected to a second stage of low-temperature heat treatment at 150~200℃ to obtain the product; the first modifier and the second modifier are different modifiers in Formula 1.

9. An application of a modified lithium-rich manganese-based cathode active material, characterized in that, It is used as a positive electrode active material for preparing lithium-ion batteries; the modified lithium-rich manganese-based positive electrode active material is the modified lithium-rich manganese-based positive electrode active material according to any one of claims 1 to 5 and / or the modified lithium-rich manganese-based positive electrode active material prepared by the preparation method according to any one of claims 6 to 8.

10. A lithium-ion battery, characterized in that, Its positive electrode contains the modified lithium-rich manganese-based positive electrode active material according to any one of claims 1 to 5 and / or the modified lithium-rich manganese-based positive electrode active material prepared by the preparation method according to any one of claims 6 to 8.

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