A lithium-rich manganese-based cathode material and its preparation method

Abstract

This invention provides a method for preparing a lithium-rich manganese-based cathode material, comprising the following steps: D1: Lithium nitrate, manganese nitrate, nickel nitrate, and cobalt nitrate are dissolved in deionized water at a molar ratio of 1.2:0.54:0.13:0.13 to prepare a metal salt solution. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 is co-precipitated with a precipitant and a complexing agent in a solvent to generate a lithium-rich manganese-based core; D2: The lithium-rich manganese-based core is mixed with an interfacial bridging agent in an organic solvent and stirred for 2-4 hours. After drying, an interfacial bridging agent layer is formed on the lithium-rich manganese-based core; D3: The material obtained after step S2 is mixed successively with three metal salt solutions of different concentrations, and different NCM shells are coated on the outside of the interfacial bridging agent layer; D4: After high-temperature sintering, a lithium-rich manganese-based cathode material is obtained. In this invention, the LMRO core, Li2ZrO3 bridging agent, and gradient NCM shell work synergistically to greatly enhance the inhibition of lattice oxygen migration, improve structural stability, and thus significantly improve the first-time efficiency and suppress the cumulative gas release.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a lithium-rich manganese-based cathode material and its preparation method. Background Technology

[0002] Cathode materials are the most critical component of lithium-ion batteries. They are the source of Li+ in lithium-ion batteries, directly determining their energy density and significantly influencing power density, cycle life, and safety performance. Lithium-rich manganese-based cathode materials (xLi2MnO3·(1-x)LiMO, M=Ni, Co, Mn, hereinafter referred to as LRMO) possess high specific capacity (>250 mAh / g) and high operating voltage, and are considered a primary material for next-generation power batteries. However, when LRMO materials are first charged to above 4.5V, the Li2MnO3 component is activated, leading to irreversible precipitation of lattice oxygen. The formation of numerous oxygen vacancies causes transition metal ions to migrate, resulting in crystal structure rearrangement and instability. This instability leads to a chain reaction of problems, including poor cycle life and low initial efficiency. Therefore, in the preparation and use of lithium-rich manganese-based cathode materials, there is an urgent need for an LRMO modification method that can effectively suppress lattice oxygen precipitation, is simple to process, and is easily industrialized, in order to improve the various properties of LRMO materials and expand their application range. Summary of the Invention

[0003] To address the shortcomings of existing lithium-rich manganese-based cathode materials, this invention provides a method for preparing lithium-rich manganese-based cathode materials, comprising the following steps: D1: Lithium nitrate, manganese nitrate, nickel nitrate, and cobalt nitrate were dissolved in deionized water in a molar ratio of 1.2:0.54:0.13:0.13 to prepare a metal salt solution. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, and co-precipitates with precipitant and complexing agent in solvent to generate lithium-rich manganese-based core; D2: The lithium-rich manganese-based core and the interface bridging agent are mixed in an organic solvent and stirred for 2-4 hours. After drying, an interface bridging agent layer is formed on the lithium-rich manganese-based core. D3: The material obtained after the reaction in step S2 is mixed with three metal salt solutions of different concentrations in sequence, and the pH value during the reaction process is controlled to be 11-12. Different NCM shells are coated on the outside of the interface bridging agent layer, and then the precursor is obtained by aging, filtration, washing and drying. D4: The precursor obtained in step S3 is mixed with LiOH·H2O and sintered at high temperature in an oxygen atmosphere to obtain a lithium-rich manganese-based cathode material.

[0004] Furthermore, the interfacial bridging agent in step D2 is zirconium oxychloride or triethyl phosphate.

[0005] Furthermore, the three metal salt solutions of different concentrations in step D3 are nickel-cobalt-manganese nitrate solutions, namely a high-nickel solution with a nickel, cobalt, and manganese molar ratio of 0.88:0.09:0.03; a medium-nickel solution with a nickel, cobalt, and manganese molar ratio of 0.70:0.15:0.15; and a low-nickel solution with a nickel, cobalt, and manganese molar ratio of 0.50:0.20:0.30.

[0006] Furthermore, in step D3, the order in which the three metal salt solutions of different concentrations are added is as follows: first, the high-nickel solution is pumped in, then the medium-nickel solution is added, and finally the low-nickel solution is added.

[0007] Furthermore, the high-temperature sintering reaction conditions in step D4 are as follows: pre-fire at 500°C for 4 hours by heating at 5°C / min, and then sintering at 800°C for 16 hours.

[0008] On the other hand, the present invention also provides a lithium-rich manganese-based cathode material prepared by the above method: a lithium-rich manganese-based cathode material.

[0009] Furthermore, the bridging agent layer is made of lithium zirconate.

[0010] Furthermore, the material comprises, from the inside out, an inner shell layer, a bridging agent layer, and a gradient NCM layer. Furthermore, the thickness of the interface bridging agent layer is 7-8 nm, and the thickness of the gradient NCM layer is 40-50 nm.

[0011] The lithium-rich manganese-based cathode material prepared by the method of this invention comprises an LRMOR core, a bridging agent layer, and a gradient NCM shell. The LMRO core, Li2ZrO3 bridging agent, and gradient NCM shell work synergistically to greatly enhance the inhibition of lattice oxygen migration, improve structural stability, thereby significantly improving the first-stage efficiency, suppressing the release of accumulated gas, and enhancing the overall performance of the battery. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the lithium-rich manganese-based material prepared by the present invention; Figure 2 This is a comparison chart of the battery performance of lithium-rich manganese-based materials prepared in various embodiments of the present invention. Detailed Implementation Example 1

[0013] This embodiment provides a method for preparing lithium-rich manganese-based materials, including the following steps: S1: preparing a metal salt solution, specifically: dissolving lithium nitrate, manganese nitrate, nickel nitrate, and cobalt nitrate in deionized water at a molar ratio of 1.2:0.54:0.13:0.13 to prepare a metal salt solution Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2; S2: Prepare the precipitant solution by mixing 2.0 mol / L NaOH solution and 0.2 mol / L NH4OH solution in a molar ratio of 1:0.1 to prepare a complexing agent.

[0014] S3: Synthesis of lithium-rich manganese-based cathode material precursor, specifically: N2 is continuously bubbled into a stirred tank for protection, and a base solution of deionized water and 5 mL of ammonia (0.05 mol / L concentration) is added. Then, a metal salt solution of Li... 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, complexing agent S1: Prepare a metal salt solution by dissolving lithium nitrate, manganese nitrate, nickel nitrate, and cobalt nitrate in deionized water at a molar ratio of 1.2:0.54:0.13:0.13. Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2; S2: Prepare the precipitant solution by mixing 2.0 mol / L NaOH solution and 0.2 mol / L NH4OH solution in a molar ratio of 1:0.1 to prepare a complexing agent.

[0015] S3: Synthesis of lithium-rich manganese-based cathode material precursor, specifically: N2 is continuously bubbled into a stirred tank for protection, and a base solution of deionized water and 5 mL of ammonia (0.05 mol / L concentration) is added. Then, a metal salt solution of Li... 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 and complexing agent solution were added in parallel via a peristaltic pump. The reaction pH was strictly controlled at 10.8-11.2, the reaction temperature at 50°C, and the stirring rate at 500 rpm. After the reaction was completed, the mixture was aged, filtered, washed, and dried to obtain spherical LMRO(OH)2 precursor.

[0016] S4: High-temperature lithiation of lithium-rich manganese-based precursor, specifically: the precursor LMRO(OH)2 is thoroughly mixed with LiOH.H2O, pre-calcined at 500°C for 5 hours in an oxygen atmosphere, then heated to 900°C for 12 hours and cooled in the furnace to obtain LMRO inner shell powder material.

[0017] S5: Li2ZrO3 interfacial bridging agent layer modification, specifically: 10g of LMRO inner shell powder material was dispersed in 200ml of anhydrous ethanol to obtain a suspension; 0.65g of zirconium oxychloride was weighed and dissolved in 50ml of ethanol, and added dropwise to the above suspension. The mixture was stirred and refluxed at 60°C for 2 hours to allow zirconium to be uniformly adsorbed onto the LMRO surface. The mixture was dried at 80°C for 6 hours. The dried powder was mixed with 0.25g of LiOH·H2O and calcined in air at 500°C for 3 hours to form a Li2ZrO3 bridging agent coating layer on the outer layer of the LMRO inner shell material.

[0018] S6: Gradient NCM shell coating, specifically: 10g of the Li2ZrO3-modified LMRO material was redispersed in a four-necked flask containing 300 mL of deionized water. 0.5 mL of concentrated ammonia was added as a dispersant and complexing agent for subsequent reactions. The flask was placed in a constant temperature water bath, maintaining the temperature at 55±1°C, and mechanical stirring was started at 400 rpm to form a uniform and stable suspension as the reaction base liquid. To achieve a continuous gradient in the shell composition, solutions of three different transition metals were prepared in advance, with the sum of the molar concentrations of nickel, cobalt, and manganese ions in the three solutions being 1.0 mol / L. The three solutions of different transition metals were high-nickel solution A, medium-nickel solution B, and low-nickel solution C. In this high-nickel solution A, nickel nitrate (Ni(NO3)2·6H2O), cobalt nitrate (Co(NO3)2·6H2O), and manganese nitrate (Mn(NO3)2·4H2O) were weighed and mixed in a molar ratio of 0.88:0.09:0.03, and dissolved together in deionized water to prepare a mixed solution with a total metal ion concentration of 1.0 mol / L. The Ni content in the solution... 2+ The concentration was 0.88 mol / L, Co 2+ The concentration is 0.09 mol / L, and the Mn²⁺ concentration is 0.03 mol / L. For nickel solution B: nickel nitrate (Ni(NO₃)₂·6H₂O), cobalt nitrate (Co(NO₃)₂·6H₂O), and manganese nitrate (Mn(NO₃)₂·4H₂O) are weighed out in a molar ratio of 0.70:0.15:0.15 and mixed, then dissolved together in deionized water; the Ni concentration in the solution is... 2+ The concentration is 0.70 mol / L, Co 2+ The concentration is 0.15 mol / L, Mn 2+The concentration is 0.15 mol / L. The low-nickel solution C is prepared in a molar ratio of 0.50:0.20:0.30: nickel nitrate (Ni(NO3)2·6H2O), cobalt nitrate (Co(NO3)2·6H2O), and manganese nitrate (Mn(NO3)2·4H2O) are weighed, mixed, and dissolved together in deionized water; the Ni content in the solution is... 2+ The concentration is 0.50 mol / L, Co 2+ The concentration is 0.20 mol / L, Mn 2+ The concentration was 0.30 mol / L. Then, a multi-channel peristaltic pump was used to precisely pump the prepared high-nickel solution A, medium-nickel solution B, low-nickel solution C, along with the precipitant and ammonia solution, into the reactor containing the reaction substrate. The entire pumping process was automated by a programmable controller, which controlled the continuous and linear changes in the flow rate of each pipeline to achieve a precise gradient distribution of the NCM shell composition from the inside out. The specific process was carried out in three stages: The first stage forms a high-nickel transition layer, lasting 30 minutes. Initially, only high-nickel solution A and the precipitant are pumped in. Within 0 to 30 minutes, the pumping flow rate of high-nickel solution A is linearly reduced from 2.0 mL / min to 0.5 mL / min under controlled conditions. Simultaneously, the pumping flow rate of medium-nickel solution B increases linearly from zero to 1.5 mL / min. The flow rate of the precipitant (NaOH) is monitored in real-time by a pH meter and dynamically adjusted via program feedback to precisely stabilize the pH of the reaction system within the range of 11.2 ± 0.1. Ammonia (NH4OH) is maintained at a constant low flow rate (0.2 mL / min) as a complexing buffer. During this stage, an inner layer structure with a high but continuously decreasing nickel content is deposited on the LRMO core surface.

[0019] The second stage forms a medium-nickel transition layer, lasting 30 minutes; between the 30th and 60th minutes, the program switches over. The flow rate of high-nickel solution A drops to zero and remains at zero by the 30th minute; the flow rate of medium-nickel solution B decreases linearly from its initial 1.5 mL / min to 0.5 mL / min; simultaneously, the pumped flow rate of low-nickel solution C increases linearly from zero to 1.0 mL / min. The control strategy for the precipitant and ammonia is the same as in the first stage. The shell deposited in this stage continues to transition from a medium nickel content towards a manganese-rich state.

[0020] The third stage forms a stable manganese-rich outer shell, lasting 60 minutes. During the final 60 minutes of the reaction (from minute 60 to minute 120), the program maintains a constant flow rate of 1.0 mL / min for solution C, while the flow rates of high-nickel solution A and medium-nickel solution B are both zero. In this stable deposition stage, the control methods for the precipitant and ammonia remain unchanged, ultimately forming a stable, manganese-rich outer shell on the outermost layer of the particles, thus completing the construction of the entire concentration gradient NCM shell.

[0021] After coating, the product was aged for 6 hours, then filtered, washed repeatedly with deionized water and ethanol until the filtrate was neutral, and finally dried in a vacuum oven at 100°C for 12 hours to obtain a precursor powder with a "core-bridging agent-gradient shell" structure.

[0022] S7: High-temperature crystallization: The precursor powder with the above "core-bridging agent-gradient shell" structure is thoroughly mixed with LiOH.H2O, and pre-calcined at 500°C for 4 hours in an oxygen atmosphere at a rate of 5°C / min, and then sintered at 800°C for 16 hours to obtain the final product.

[0023] Example 2 This embodiment is the same as steps S1-S5 in Embodiment 1. The difference is that step S6 in this embodiment is different from that in Embodiment 1. Instead of using a gradient salt solution, a 1.0 mol / L single metal salt solution is used. Specifically, the metal salt solution is obtained by weighing nickel nitrate (Ni(NO3)2·6H2O), cobalt nitrate (Co(NO3)2·6H2O), and manganese nitrate (Mn(NO3)2·4H2O) in a molar ratio of 0.6:0.2:0.2 and mixing them in deionized water. Specifically, 10g of LMRO material modified with Li2ZrO3 is redispersed in a four-necked flask containing 300 mL of deionized water, and 0.5 mL of concentrated ammonia is added as a dispersant and complexing agent for subsequent reactions. The flask was placed in a constant-temperature water bath, maintaining the temperature at 55±1°C, and mechanical stirring was started at 400 rpm to form a homogeneous and stable suspension as the reaction base liquid. Then, a metal salt solution was pumped into the flask at a stable rate of 2.0 mL / min for 30 min. Simultaneously, the flow rate of the precipitant (NaOH) was monitored in real time by a pH meter and dynamically adjusted via a program to precisely stabilize the pH of the reaction system within the range of 11.2±0.1. Ammonia (NH4OH) was maintained at a constant low flow rate (0.2 mL / min) as a complexing buffer. During this stage, an inner layer structure with a high but continuously decreasing nickel content was deposited on the surface of the LRMO core.

[0024] Example 3

[0025] This embodiment is the same as steps S1-S4 and S6-S8 in Embodiment 1, except that step S5 differs from that in Embodiment 1. Specifically, 10g of LMRO powder is dispersed in 200ml of anhydrous ethanol to obtain a suspension; 0.3g of triethyl phosphate is weighed and dissolved in 50ml of ethanol, and added dropwise to the above suspension. The mixture is stirred and refluxed at 60°C for 2 hours to allow P to be uniformly adsorbed on the LMRO surface. The mixture is then dried at 80°C for 6 hours. The dried powder is lightly mixed with an appropriate amount of LiOH·H2O and calcined in air at 500°C for 3 hours to form a Li3PO4 coating layer on the outside of the LMRO material.

[0026] Example 4 The difference between this embodiment and Embodiment 1 is that step S6 is different from that in Embodiment 1, while the remaining steps are the same as in Embodiment 1. Specifically, in step S6, the total deposition amount of the gradient NCM shell coating is different from that in Embodiment 1, while the remaining steps are the same as in Embodiment 1. Specifically, in step S6, the total reaction time (120 minutes), the duration of each stage, the solution composition, and the pH control strategy are kept exactly the same as in Embodiment 1, but the pumping flow rates of high-nickel solution A, medium-nickel solution B, and low-nickel solution C are all adjusted to 83.3% of those in Embodiment 1.

[0027] Example 5 The difference between this embodiment and Embodiment 1 lies in step S6. Specifically, the total deposition amount of the gradient NCM shell in step S6 is different from that in Embodiment 1; the remaining steps are the same as in Embodiment 1. Specifically, in step S6, the total reaction time, duration of each stage, solution composition, and pH control strategy are kept exactly the same as in Embodiment 1, but the pumping flow rate of all metal salt solutions is adjusted to 7 / 6 of that in Embodiment 1. Example 6

[0028] The difference between this embodiment and Embodiment 1 lies in step S5. In this embodiment, S5 is different from Embodiment 1 in that the coating amount of the Li2ZrO3 bridging agent layer is different. Specifically, the amount of zirconium oxychloride (ZrOCl2·8H2O) is increased to about 0.9 g (the remaining steps and lithium source ratio are the same as in Embodiment 1), ultimately forming a Li2ZrO3 bridging agent layer with a mass fraction of about 7%.

[0029] Comparative Example 1:

[0030] The LRMO powder obtained in the first step was mixed with NCM powder synthesized independently via conventional co-precipitation, whose total composition was comparable to that of the shell layer in Example 1, and then subjected to simple physical-mechanical mixing. No chemical coating was performed in this comparative example. First, using the same co-precipitation process as in step S3 of Example 1, independent NCM powder with an average shell layer composition comparable to that of Example 1 was prepared. Specifically, a mixed salt solution with a total metal ion concentration of 1.0 mol / L was prepared at a Ni:Co:Mn molar ratio of approximately 0.69:0.15:0.16, and co-precipitated at pH 11.2 and a temperature of 55°C. After aging, washing, and drying, the NCM precursor was obtained. This precursor was sintered with an appropriate amount of lithium source at high temperature in an oxygen atmosphere to obtain NCM cathode material powder. Finally, the LRMO inner shell powder obtained in the first step and the NCM powder were mixed with each other at a core-shell mass ratio comparable to that in Example 1 (approximately 65:30) using a simple physical-mechanical mixing method (e.g., ball milling) for 30 minutes.

[0031] Comparative Example 2

[0032] The difference between this embodiment and embodiment 1 is that step S5 is not performed in the preparation method of this embodiment, while the remaining steps are the same as in embodiment 1. Comparative Example 3

[0033] The difference between this comparative example and Example 1 is that, in step S6, when constructing the NCM shell, the pumping procedure of the metal salt solution is reversed compared to Example 1 (i.e., forming an "anti-gradient" shell), while the remaining steps (including bridging agent modification) are exactly the same as in Example 1. Specifically: In step S6, the total reaction time (120 minutes), solution composition (high nickel A, medium nickel B, low nickel C), total metal ion concentration (1.0 mol / L), and pH control strategy (11.2 ± 0.1) are kept the same as in Example 1, but the pumping order and flow rate change relationship of the three solutions are completely reversed, and the process is carried out in the following three stages; In the first stage (0-30 minutes), a manganese-rich inner layer is formed. Initially, only low-nickel solution C and the precipitant are pumped in. The program controls the linear decrease in the pumping flow rate of low-nickel solution C from 2.0 mL / min to 0.5 mL / min. Simultaneously, the pumping flow rate of medium-nickel solution B increases linearly from zero to 1.5 mL / min.

[0034] In the second stage, spanning 30-60 minutes, a medium-nickel transition layer is formed. By the 30th minute, the flow rate of the low-nickel solution C has decreased to zero and remained at that point. The flow rate of the medium-nickel solution B decreases linearly from its initial 1.5 mL / min to 0.5 mL / min. Simultaneously, the pumped flow rate of the high-nickel solution A increases linearly from zero to 1.0 mL / min.

[0035] In the third stage, from 60 to 120 minutes, a stable nickel-rich outer shell is formed. During the last 60 minutes of the reaction, the program maintains a constant flow rate of 1.0 mL per minute for the high-nickel solution A, while the flow rates of the low-nickel solution C and the medium-nickel solution B are both zero.

[0036] The aging, filtration, washing, drying and subsequent high-temperature crystallization steps after coating are exactly the same as in Example 1.

[0037] Material structural performance testing The lithium-rich manganese-based cathode material prepared in Example 1 was subjected to scanning electron microscopy. To better illustrate its structure and properties, the following methods were used: Figure 1 The schematic diagram shows the structure. The mass percentages of the components in the lithium-rich manganese-based cathode material prepared by the method of this invention are as follows: LMRO core approximately 65%, NCM gradient shell approximately 30%, and Li2ZrO3 interfacial bridging agent approximately 5%. The LMRO particle diameter is 10 micrometers, the thickness of the Li2ZrO3 interfacial bridging agent layer is approximately 7-8 nanometers, and the total thickness of the gradient NCM shell is approximately 50 nanometers. Battery performance test

[0038] The final product was used as the positive electrode active material, mixed with conductive agent and binder in a certain proportion to form a slurry, coated on aluminum foil, dried, rolled, and sliced. Then, it was assembled with lithium foil negative electrode and electrolyte in an argon glove box to form a CR2032 coin cell. The initial efficiency and cumulative gas release of the corresponding cells were tested, and the corresponding test results are as follows: Figure 2 As shown.

[0039] In the preparation of lithium-rich manganese-based cathode materials, the simple mixing method of Comparative Example 1 was used to coat the outer shell of the lithium-rich manganese-based cathode with an NCM shell. This coating layer exhibited a uniform structure from the inside out. However, due to the weak interfacial bonding between the core and the shell (only physical contact), lithium-ion migration resistance was high. During battery cycling, the interface easily separated, failing to significantly suppress gas release and impairing the first-efficiency performance, resulting in high gas production and low first-efficiency. In contrast, the preparation method in Comparative Example 2, without a bridging layer between the inner shell and the gradient transition shell, allowed the gradient shell structure itself to alleviate some lattice mismatch and side reactions. Compared to the scheme in Comparative Example 1, this method improved the first-efficiency performance. Furthermore, the connection between the inner shell and the gradient transition shell provided a stable lithium-ion migration channel and effectively suppressed interfacial side reactions and oxygen loss. Simultaneously, the gradient shell mitigated structural stress. The LMRO core, Li2ZrO3 bridging agent, and gradient NCM shell work synergistically to significantly enhance the inhibition of lattice oxygen migration, improve structural stability, and thus significantly improve the first-time efficiency, suppress the cumulative gas release, and improve the overall performance of the battery. The lack of strong chemical bonds between the core and shell leads to continuous lattice oxygen precipitation, reducing lattice stability and resulting in low first-time efficiency and excessive gas production. However, using the preparation method in Example 1 of this invention, the lithium-rich manganese-based cathode material has a core-shell structure, with a bridging agent layer connecting the core and shell. The lithium zirconate bridging agent layer acts as a "molecular bridge," tightly binding the core and gradient shell through strong chemical bonds.

Claims

1. A method for preparing a lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: D1: Lithium nitrate, manganese nitrate, nickel nitrate, and cobalt nitrate were dissolved in deionized water in a molar ratio of 1.2:0.54:0.13:0.13 to prepare a metal salt solution. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, and co-precipitates with precipitant and complexing agent in solvent to generate lithium-rich manganese-based core; D2: The lithium-rich manganese-based core and the interface bridging agent are mixed in an organic solvent and stirred for 2-4 hours. After drying, an interface bridging agent layer is formed on the lithium-rich manganese-based core. D3: The material obtained after the reaction in step S2 is mixed with three metal salt solutions of different concentrations in sequence, and the pH value during the reaction process is controlled to be 11-12. Different NCM shells are coated on the outside of the interface bridging agent layer, and then the precursor is obtained by aging, filtration, washing and drying. D4: The precursor obtained in step S3 is mixed with LiOH·H2O and sintered at high temperature in an oxygen atmosphere to obtain a lithium-rich manganese-based cathode material.

2. The method for preparing the lithium-rich manganese-based cathode material as described in claim 1, characterized in that, The interfacial bridging agent in step D2 is zirconium oxychloride or triethyl phosphate.

3. The method for preparing the lithium-rich manganese-based cathode material as described in claim 1, characterized in that, The three metal salt solutions of different concentrations in step D3 are nickel-cobalt-manganese nitrate solutions, namely a high-nickel solution with a nickel, cobalt, and manganese molar ratio of 0.88:0.09:0.03; a medium-nickel solution with a nickel, cobalt, and manganese molar ratio of 0.70:0.15:0.15; and a low-nickel solution with a nickel, cobalt, and manganese molar ratio of 0.50:0.20:0.

30.

4. The method for preparing the lithium-rich manganese-based cathode material as described in claim 3, characterized in that, In step D3, the order in which the three metal salt solutions of different concentrations are added is as follows: first, the high-nickel solution is pumped in, then the medium-nickel solution is added, and finally the low-nickel solution is added.

5. The method for preparing the lithium-rich manganese-based cathode material as described in claim 1, characterized in that, The high-temperature sintering reaction conditions in step D4 are as follows: preheating to 500°C at 5°C / min for 4 hours, followed by sintering at 800°C for 16 hours.

6. A lithium-rich manganese-based cathode material, characterized in that, Prepared using the preparation method described in any one of claims 1-5.

7. The lithium-rich manganese-based cathode material as described in claim 6, characterized in that, The bridging agent layer is made of lithium zirconate.

8. The lithium-rich manganese-based cathode material as described in claim 7, characterized in that, It includes, from the inside out, an inner shell layer, a bridging agent layer, and a gradient NCM layer.

9. The lithium-rich manganese-based cathode material as described in claim 8, characterized in that, The thickness of the interface bridging agent layer is 7-8 nm, and the thickness of the gradient NCM layer is 40-50 nm.

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