High-entropy cobalt-free lithium-rich manganese-based positive electrode material, preparation method and application thereof

Abstract

The application discloses a high-entropy cobalt-free lithium-rich manganese-based positive electrode material and a preparation method and application thereof, and relates to the technical field of battery materials. 1+ x Mn a Ni b M c O 2+δ The compounds of Mn, Ni and M are weighed according to the molar ratio of each element in the material composition Li The mixed aqueous solution is reacted with a precipitating agent and a complexing agent to obtain a precursor material; the precursor material is mixed with a compound of Li and a two-dimensional MXene nanomaterial by ball milling to obtain a mixed material; and the mixed material is subjected to joule heat treatment; the application greatly improves the stability and electrochemical performance of the material under the condition of abandoning the use of cobalt elements, reduces the production cost and cycle, and solves the technical problem that traditional lithium-rich materials need to rely on cobalt elements to stabilize the structure.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a high-entropy cobalt-free lithium-rich manganese-based cathode material, its preparation method, and its application. Background Technology

[0002] As a core technology for new energy storage, lithium-ion batteries rely heavily on cathode materials, whose performance directly determines the battery's energy density, cycle life, and cost. Lithium-rich manganese-based cathode materials (LRMO) are considered key candidate materials for next-generation high-energy-density batteries due to their high theoretical capacity (>250 mAh / g) and low-cost potential. However, existing lithium-rich manganese-based cathode materials still have many shortcomings.

[0003] (1) Structural instability: Lithium-rich materials are prone to irreversible transformation from layered structure to spinel / rock salt phase during cycling, leading to voltage decay (>0.5 V / 100 cycles) and rapid capacity decay (>30%); cation mixing (such as Li + / Ni 2+ This exacerbates lattice distortion, leading to grain cracks and electrolyte side reactions.

[0004] (2) Insufficient kinetic performance: Li + The diffusion rate in lithium-rich materials is low (~10). -12 cm² / s), resulting in poor rate performance (>5C capacity decay of 50%); oxygen anion redox reaction (O 2- / O - The kinetics are slow, leading to irreversible oxygen evolution and interfacial side reactions.

[0005] (3) Cobalt dependence and high cost: Traditional lithium-rich materials rely on cobalt to stabilize their structure, but cobalt resources are scarce and their prices fluctuate wildly. In addition, the mining and purification process of cobalt causes environmental pollution problems, which does not meet the needs of sustainable development.

[0006] (4) Limitations of synthesis process: Traditional high-temperature solid-state methods (>800℃) are prone to causing Mn 3+ Disproportionation reaction (2Mn) 3+ →Mn 2+ +Mn 4+ This process creates oxygen vacancies and secondary phases, disrupting the structural integrity of the material. Furthermore, this method struggles to achieve a high-entropy structure with uniform distribution of multiple elements, making it difficult to guarantee the stability and consistency of the material's properties.

[0007] Patent document CN119118213B discloses a lithium-rich manganese-based cathode material, its preparation method, and a lithium-ion battery. This technology achieves the regulation of cobalt and lithium ion migration under different electrochemical states by constructing a nanoscale dynamic interface between cobalt and lithium within the material, thus avoiding passivation after doping to some extent. Simultaneously, the introduction of phosphorus and sulfide groups stabilizes the material's crystal structure, improves electron and ion transport efficiency, and enhances the material's conductivity. However, the high cobalt content (up to 10%) in this scheme leads to a significant increase in material cost of approximately 30%, and the limited availability of cobalt resources severely restricts the industrial-scale application of this technology.

[0008] Patent document CN117985774A discloses a cobalt-free lithium-rich manganese-based cathode material and its preparation method, which uses a sol-gel-sintering strategy to prepare TaS2-coated Li 1+x Ni y Mn z O2-based cobalt-free lithium-rich manganese cathode material exhibits advantages in specific capacity, rate performance, and cycle life, mitigating to some extent the shortcomings of poor structural stability and rate performance found in cobalt-free lithium-rich manganese materials. However, this technology still suffers from insufficient kinetic performance. The oxygen anion reaction is highly irreversible, and simply coating the Mn-Ni system with TaS2 cannot completely solve the structural stability problem during cycling; the layered structure is still prone to collapse after cycling. Furthermore, the high-temperature calcination process easily leads to component segregation, affecting the uniform distribution of multiple elements and limiting further improvements in material performance. Summary of the Invention

[0009] This invention aims to address the technical problems of existing lithium-rich manganese-based cathode materials, such as structural instability, insufficient kinetics, high cost due to reliance on cobalt, and difficulty in ensuring the stability and consistency of materials prepared by traditional processes. The goal is to provide a high-entropy cobalt-free lithium-rich manganese-based cathode material, its preparation method, and its applications. By eliminating the use of cobalt, the stability and electrochemical performance of the material are greatly improved, and the production cost and cycle are reduced. This solves the technical problem that traditional lithium-rich materials rely on cobalt to stabilize their structure.

[0010] The present invention is achieved through the following technical solution.

[0011] The first objective of this invention is to provide a method for preparing a high-entropy, cobalt-free, lithium-rich manganese-based cathode material, comprising the following steps:

[0012] S1, according to the composition of high-entropy cobalt-free lithium-rich manganese-based cathode material Li 1+x Mn a Ni b M c O 2+δThe molar ratios of each element are weighed, and compounds of Mn, Ni, and M are dissolved in water to prepare a mixed solution; wherein M is at least three of Mg, Al, Sn, Ti, Zr, Nb, Mo, W, Y, Fe, and V, and x+a+b+c=1;

[0013] S2. React the mixed solution with a precipitant and a complexing agent to obtain the precursor material;

[0014] S3. The precursor material is ball-milled and mixed with the Li compound and the two-dimensional MXene nanomaterial to obtain a mixed material;

[0015] S4. The mixed material is subjected to Joule heat treatment to obtain a high-entropy cobalt-free lithium-rich manganese-based cathode material.

[0016] This invention proposes a novel method for preparing cobalt-free, lithium-rich manganese-based cathode materials, wherein the cathode material is composed of Li... 1+x Mn a Ni b M c O 2+δ By employing a high-entropy multi-principal-component design, the transformation of layered structures to spinel / rock salt phases at the atomic scale is suppressed by utilizing the configurational entropy effect, which can significantly improve the structural stability of the material. The high-entropy design introduces a variety of inert ions M to stabilize the oxygen framework structure and improve the material performance.

[0017] This invention also introduces two-dimensional MXene nanomaterials, which effectively improve the conductivity and stability of the material, thereby preparing a high-entropy cobalt-free lithium-rich manganese-based cathode material with excellent comprehensive performance and low cost.

[0018] This invention employs ultrafast Joule thermal synthesis technology to achieve the disordered reconstruction structure of cations in high-entropy cobalt-free lithium-rich manganese-based cathode materials, avoiding the Mn content issues encountered during traditional high-temperature calcination (>800℃). 3+ Addressing disproportionation and grain coarsening issues, ensuring the integrity and consistency of the material structure, can significantly improve the structural stability and electrochemical performance of the material.

[0019] Furthermore, the compounds of Mn, Ni, M, and Li are selected from one or more of the following: carbonates, oxalates, acetates, sulfates, nitrates, halides, oxides, and hydroxides of Mn, Ni, M, and Li, respectively. Specifically, the compounds of Mn are selected from one or more of the following: carbonates, oxalates, acetates, sulfates, nitrates, halides, oxides, and hydroxides of Mn; the compounds of Ni are selected from one or more of the following: carbonates, oxalates, acetates, sulfates, nitrates, halides, oxides, and hydroxides of M; and the compounds of Li are selected from one or more of the following: carbonates, oxalates, acetates, sulfates, nitrates, halides, oxides, and hydroxides of lithium.

[0020] Furthermore, the composition of the high-entropy cobalt-free lithium-rich manganese-based cathode material is Li 1+x Mn a Ni b M c O 2+δ Where 0.4≤a≤0.6, 0.1≤b≤0.3, 0≤x≤0.3, x, a, b, c are all molar ratios, x is the excess coefficient of Li, and δ is the non-stoichiometric coefficient of oxygen.

[0021] Furthermore, the precipitant is a hydroxide precipitant or a carbonate precipitant, and the complexing agent is an ammonia solution. The hydroxide precipitant is selected from any one or a combination of two of NaOH and KOH, and the carbonate precipitant is selected from any one or a combination of two of Na₂CO₃ and K₂CO₃.

[0022] Furthermore, when using a hydroxide precipitant, the pH of the system is maintained between 10 and 12 in step S2; when using a carbonate precipitant, the pH of the system is maintained between 7 and 9 in step S2.

[0023] Therefore, step S2 specifically includes:

[0024] S21. Preparation of precipitant and complexing agent: Prepare the precipitant to a concentration of 0.5–4 mol / L and the complexing agent to a concentration of 1 mol / L;

[0025] S22. Precipitation Reaction: The 0.5–4.0 mol / L mixed solution obtained in step S1, along with the precipitant and complexing agent, is simultaneously added to a reaction vessel containing deionized water. The dropping rate is strictly controlled at 1–3 mL / min, and the stirring rate is set to 350–1200 r / min. The temperature inside the reaction vessel is maintained at 50–70℃. Throughout the reaction, for carbonate precipitants, the pH value of the system is maintained between 7 and 9; for hydroxide precipitants, the pH value is maintained between 10 and 12 to ensure that the precipitation reaction proceeds fully and uniformly.

[0026] S23. Post-treatment: After the addition is complete, react for 12-24 hours, then filter, wash, and dry the precipitate at 105-130℃ to obtain the precursor material.

[0027] Furthermore, the amount of the two-dimensional MXene nanomaterial added accounts for 0.1-3 wt% of the total amount of the precursor material and the Li compound.

[0028] Therefore, step S3 specifically includes:

[0029] According to the composition of high-entropy cobalt-free lithium-rich manganese-based cathode materials, Li 1+x Mn a Ni b M c O 2+δ The Li compound was weighed according to the stoichiometric ratio of Li and mixed thoroughly in a ball mill with the precursor material obtained in step S2 and 0.1-3 wt% of two-dimensional MXene nanomaterials. The ball milling speed was 200-500 rpm and the ball milling time was 2-10 h to ensure that the components were uniformly dispersed.

[0030] Furthermore, the Joule heat treatment includes:

[0031] First heat treatment: Apply a current of 8-12A and keep it on for 5-15 seconds;

[0032] Second heat treatment: Apply a current of 10-15A and keep it on for 10-30 seconds.

[0033] Furthermore, the Joule heat treatment is carried out in an argon protective atmosphere.

[0034] Therefore, Joule heat treatment includes the following steps:

[0035] First heat treatment: Weigh 1-2g of the S3 mixture and place it in a 30-80cm container. 2On a carbon cloth (preferably 20×50cm), the first heat treatment is carried out in an argon protective atmosphere by applying a current of 8-12A for 5-15s to achieve rapid heating and initial reaction of the material using the Joule heating effect, resulting in powder after the first heat treatment; this process is completed in a very short time, effectively avoiding uneven element diffusion and grain coarsening problems.

[0036] Second heat treatment: After grinding the powder from the first heat treatment, it is placed again on carbon cloth and subjected to a second heat treatment in an argon atmosphere. The current is adjusted to 10-15A and the energizing time is 10-30s to further promote the crystal phase transformation and structural optimization of the material, ultimately obtaining a high-entropy cobalt-free lithium-rich manganese-based cathode material.

[0037] The second objective of this invention is to provide a high-entropy, cobalt-free, lithium-rich manganese-based cathode material, prepared by the aforementioned method.

[0038] The third objective of this invention is to provide an application of a high-entropy, cobalt-free, lithium-rich manganese-based cathode material in lithium-ion batteries.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects.

[0040] 1. This invention employs a high-entropy multi-principal-component design, utilizing the configurational entropy effect to suppress the transformation of layered structures to spinel / rock salt phases at the atomic scale. Furthermore, the high-entropy design introduces various inert ions to stabilize the oxygen framework structure, improving material stability and increasing battery energy density. Simultaneously, doping with two-dimensional nanomaterials MXene effectively enhances the electronic conductivity of the material system and reduces interfacial impedance, enabling the material to maintain high discharge capacity even under high-rate conditions such as 2C and 3C. Additionally, ultrafast Joule heating technology is used to precisely control the current and extremely short reaction time, achieving atomic-level uniform mixing of the material and fundamentally avoiding the Mn... 3+ Addressing issues such as disproportionation and grain coarsening ensures the integrity and consistency of the material structure, thereby guaranteeing the material's stability.

[0041] 2. This invention employs an ultra-fast Joule heating method to synthesize high-entropy cobalt-free lithium-rich manganese-based cathode materials in an extremely short time, significantly shortening the production cycle, reducing energy consumption, and completely eliminating the use of cobalt, thus eliminating dependence on scarce cobalt resources and significantly reducing material costs. At the same time, it conforms to the concepts of green manufacturing and sustainable development, providing a brand-new technical path for the large-scale industrial production of lithium-ion battery cathode materials.

[0042] 3. The material of the present invention has an initial discharge capacity of over 280 mAh / g at a 0.1C rate and a capacity retention of over 86% after 600 cycles, which significantly improves the structural stability and electrochemical performance of the material, far exceeding that of traditional cobalt-free materials, and solves the technical problem that traditional lithium-rich materials need to rely on cobalt to stabilize the structure. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0044] Figure 1 Li prepared in Example 4 1.0 [Li 0.15 Mn 0.42 Ni 0.13 Fe 0.05 Nb 0.05 Al 0.05 Ti 0.05 Nb 0.05 Mo 0.05 Scanning electron microscope image of O2;

[0045] Figure 2 Li prepared in Example 4 1.0 [Li 0.15 Mn 0.42 Ni 0.13 Fe 0.05 Nb 0.05 Al 0.05 Ti 0.05 Nb 0.05 Mo 0.05 [Chart showing the charge and discharge performance of O2] Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0047] The following detailed description, with appropriate reference to the accompanying drawings, outlines embodiments of a high-entropy cobalt-free lithium-rich manganese-based cathode material, its preparation method, and its applications. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art.

[0048] The "scope" disclosed in this invention is defined in the form of a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific scope. The scope defined in this way can include or exclude end values, and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a scope.

[0049] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0050] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0051] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other substances not listed may also be included, or that only the listed substances may be included.

[0052] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0053] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0054] It should be noted that the MXene nanosheets in the embodiments are monolayer or few-layer Ti3C2T xThe powder, branded as Xianfeng Nano, has a flake size of 3-10 μm and a thickness of 1-20 nm. Unless otherwise specified, all experimental methods used in the examples are conventional methods. All materials, reagents, methods, and instruments used, unless otherwise specified, are conventional materials, reagents, methods, and instruments in the art and can be obtained commercially by those skilled in the art.

[0055] Example 1

[0056] Li 1.0 [Li 0.15 Mn 0.45 Ni 0.1 Fe 0.1 Mg 0.1 Al 0.1 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material, the preparation method is as follows:

[0057] (1) Weigh 10 mol of metal elements from the precursor raw materials, wherein the ratio of each metal element Mn:Ni:Fe:Mg:Al by molar mass is 5.294:1.176:1.176:1.176:1.176. Mix the aqueous solutions of manganese sulfate, nickel sulfate, ferric sulfate, magnesium sulfate and aluminum sulfate to prepare a 2M mixed solution.

[0058] (2) Weigh 10 mol of sodium hydroxide to prepare a 4 M precipitant; weigh 10 mol of ammonia to prepare a 1 M complexing agent; add the mixed solution, precipitant and complexing agent simultaneously to a 5 L reactor containing 1 L of deionized water at a rate of 2 mL / min. The temperature inside the reactor is kept constant at 50 °C and the stirring rate is 400 rpm. During the entire reaction, the pH value inside the reactor is kept at 10. After the addition is complete, react for 12 h, then filter, wash, and vacuum dry at 120 °C for 24 h to obtain the precursor material.

[0059] (3) Weigh 20 g of the precursor material prepared in step (2), weigh 0.55 g of MXene nanosheets, and weigh Li 1.0 [Li 0.15 Mn 0.45 Ni 0.1 Fe 0.1 Mg 0.1 Al 0.1 Lithium hydroxide (7.65 g) with an O2 stoichiometric ratio of 1.05 was thoroughly mixed in a ball mill for 4 hours.

[0060] (4) Weigh 1 g of the mixture prepared in step (3) and place it on carbon cloth for the first heat treatment in an argon atmosphere. The current is 10 A and the duration of the heat treatment is 10 s to obtain powder after the first heat treatment. Then, grind the prepared powder and perform a second heat treatment (argon atmosphere) with a current of 12 A and a duration of 20 s to obtain Li. 1.0 [Li 0.15 Mn 0.45 Ni 0.1 Fe 0.1 Mg 0.1 Al 0.1 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material.

[0061] Example 2

[0062] Li 1.0 [Li 0.15 Mn 0.4 Ni 0.13 Fe 0.08 Mg 0.08 Al 0.08 Ti 0.08 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material, the preparation method is as follows:

[0063] (1) Weigh 10 mol of metal elements from the precursor raw materials, wherein the ratio of each metal element Mn:Ni:Fe:Mg:Al by molar mass is 4.706:1.529:0.941:0.941:0.941:0.941. Mix the aqueous solutions of manganese sulfate, nickel sulfate, ferric sulfate, magnesium sulfate and aluminum sulfate to prepare a 2M mixed solution;

[0064] (2) Weigh 10 mol of sodium hydroxide to prepare a 4 M precipitant; weigh 10 mol of ammonia to prepare a 1 M complexing agent; add the mixed solution, precipitant and complexing agent simultaneously to a 5 L reactor containing 1 L of deionized water at a rate of 2 mL / min. The temperature inside the reactor is kept constant at 50 °C and the stirring rate is 400 rpm. During the entire reaction, the pH value inside the reactor is kept at 10. After the addition is complete, react for 12 h, then filter, wash, and vacuum dry at 120 °C for 24 h to obtain the precursor material.

[0065] (3) Weigh 20 g of the precursor material prepared in step (2), weigh 0.55 g of MXene nanosheets, and weigh Li 1.0 [Li 0.15 Mn 0.4 Ni 0.13 Fe 0.08 Mg 0.08 Al 0.08 Ti 0.08Lithium hydroxide (7.66 g) with an O2 stoichiometric ratio of 1.05 was thoroughly mixed in a ball mill for 4 hours.

[0066] (4) Weigh 1 g of the mixture prepared in step (3) and place it on carbon cloth for the first heat treatment in an argon atmosphere. The current is 10 A and the duration of the heat treatment is 10 s to obtain powder after the first heat treatment. Then, grind the prepared powder and perform a second heat treatment (argon atmosphere) with a current of 12 A and a duration of 20 s to obtain Li. 1.0 [Li 0.15 Mn 0.4 Ni 0.13 Fe 0.08 Mg 0.08 Al 0.08 Ti 0.08 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material.

[0067] Example 3

[0068] Li 1.0 [Li 0.15 Mn 0.42 Ni 0.13 Fe 0.06 Mg 0.06 Al 0.06 Ti 0.06 Nb 0.06 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material, the preparation method is as follows:

[0069] (1) Weigh 10 mol of metal elements from the precursor raw materials, wherein the ratio of each metal element Mn:Ni:Fe:Mg:Al:Ti:Nb by molar mass is 4.941:1.529:0.706:0.706:0.706:0.706:0.706. Mix the aqueous solutions of manganese nitrate, nickel nitrate, iron nitrate, magnesium nitrate, aluminum nitrate, titanium oxalate and niobium oxalate to prepare a 2M mixed solution.

[0070] (2) Weigh 10 mol of sodium hydroxide to prepare a 4 M precipitant; weigh 10 mol of ammonia to prepare a 1 M complexing agent; add the mixed solution, precipitant and complexing agent simultaneously to a 5 L reactor containing 1 L of deionized water at a rate of 2 mL / min. The temperature inside the reactor is kept constant at 50 °C and the stirring rate is 400 rpm. During the entire reaction, the pH value inside the reactor is kept at 10. After the addition is complete, react for 12 h, then filter, wash, and vacuum dry at 120 °C for 24 h to obtain the precursor material.

[0071] (3) Weigh 20 g of the precursor material prepared in step (2), weigh 0.54 g of MXene nanosheets, and weigh Li 1.0 [Li0.15 Mn 0.42 Ni 0.13 Fe 0.06 Mg 0.06 Al 0.06 Ti 0.06 Nb 0.06 Lithium hydroxide (7.23 g) with an O2 stoichiometric ratio of 1.05 was thoroughly mixed in a ball mill for 4 hours.

[0072] (4) Weigh 1 g of the mixture prepared in step (3) and place it on carbon cloth for the first heat treatment in an argon atmosphere. The current is 10 A and the duration of the heat treatment is 10 s to obtain powder after the first heat treatment. Then, grind the prepared powder and perform a second heat treatment (argon atmosphere) with a current of 12 A and a duration of 20 s to obtain Li. 1.0 [Li 0.15 Mn 0.42 Ni 0.13 Fe 0.06 Mg 0.06 Al 0.06 Ti 0.06 Nb 0.06 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material.

[0073] Example 4

[0074] Li 1.0 [Li 0.15 Mn 0.42 Ni 0.13 Fe 0.05 Nb 0.05 Al 0.05 Ti 0.05 Nb 0.05 Mo 0.05 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material, the preparation method is as follows:

[0075] (1) Weigh 10 mol of metal elements from the precursor raw materials, wherein the ratio of each metal element Mn:Ni:Fe:Mg:Al:Ti:Nb:Mo by molar mass is 4.941:1.529:0.588:0.588:0.588:0.588:0.588:0.588 by molar mass. Mix the aqueous solutions of manganese nitrate, nickel nitrate, iron nitrate, magnesium nitrate, aluminum nitrate, titanium oxalate, niobium oxalate and molybdenum nitrate to prepare a 2M mixed solution.

[0076] (2) Weigh 10 mol of sodium hydroxide to prepare a 4 M precipitant; weigh 10 mol of ammonia to prepare a 1 M complexing agent; add the mixed solution, precipitant and complexing agent simultaneously to a 5 L reactor containing 1 L of deionized water at a rate of 2 mL / min. The temperature inside the reactor is kept constant at 50 °C and the stirring rate is 400 rpm. During the entire reaction, the pH value inside the reactor is kept at 10. After the addition is complete, react for 12 h, then filter, wash, and vacuum dry at 120 °C for 24 h to obtain the precursor material.

[0077] (3) Weigh 20 g of the precursor material prepared in step (2), weigh 0.54 g of MXene nanosheets, and weigh Li 1.0 [Li 0.15 Mn 0.42 Ni 0.13 Fe 0.05 Nb 0.05 Al 0.05 Ti 0.05 Nb 0.05 Mo 0.05 Lithium hydroxide (7.04 g) with an O2 stoichiometric ratio of 1.05 was thoroughly mixed in a ball mill for 4 hours.

[0078] (4) Weigh 1 g of the mixture prepared in step (3) and place it on carbon cloth for the first heat treatment in an argon atmosphere. The current is 10 A and the duration of the heat treatment is 10 s to obtain powder after the first heat treatment. Then, grind the prepared powder and perform a second heat treatment (argon atmosphere) with a current of 12 A and a duration of 20 s to obtain Li. 1.0 [Li 0.15 Mn 0.42 Ni 0.13 Fe 0.05 Nb 0.05 Al 0.05 Ti 0.05 Nb 0.05 Mo 0.05 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material, the scanning electron microscope image of this material is as follows. Figure 1 As shown, the charge / discharge performance test is as follows: Figure 2 As shown.

[0079] Example 5

[0080] Li 1.0 [Li 0.2 Mn 0.425 Ni 0.2 Fe 0.025 Mg 0.025 Al 0.025 Ti 0.025 Nb 0.025 Mo0.025 Sn 0.025 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material, the preparation method is as follows:

[0081] (1) Weigh 10 mol of metal elements from the precursor raw materials, wherein the ratio of each metal element Mn:Ni:Fe:Mg:Al:Ti:Nb:Mo:Sn = 5.313:2.5:0.313:0.313:0.313:0.313:0.313:0.313 by molar ratio. Prepare a 2M mixed solution by combining the aqueous solutions of manganese nitrate, nickel nitrate, iron nitrate, magnesium nitrate, aluminum nitrate, titanium oxalate, niobium oxalate, molybdenum nitrate and tin sulfate.

[0082] (2) Weigh 10 mol of sodium hydroxide to prepare a 4 M precipitant; weigh 10 mol of ammonia to prepare a 1 M complexing agent; add the mixed solution, precipitant and complexing agent simultaneously to a 5 L reactor containing 1 L of deionized water at a rate of 2 mL / min. The temperature inside the reactor is kept constant at 50 °C and the stirring rate is 400 rpm. During the entire reaction, the pH value inside the reactor is kept at 10. After the addition is complete, react for 12 h, then filter, wash, and vacuum dry at 120 °C for 24 h to obtain the precursor material.

[0083] (3) Weigh 20 g of the precursor material prepared in step (2), weigh 0.55 g of MXene nanosheets, and weigh L Li 1.0 [Li 0.2 Mn 0.425 Ni 0.2 Fe 0.025 Mg 0.025 Al 0.025 Ti 0.025 Nb 0.025 Mo 0.025 Sn 0.025 Lithium hydroxide (7.47 g) with an O2 stoichiometric ratio of 1.05 was thoroughly mixed in a ball mill for 4 hours.

[0084] (4) Weigh 1 g of the mixture prepared in step (3) and place it on carbon cloth for the first heat treatment in an argon atmosphere. The current is 10 A and the duration of the heat treatment is 10 s to obtain powder after the first heat treatment. Then, grind the prepared powder and perform a second heat treatment (argon atmosphere) with a current of 12 A and a duration of 20 s to obtain Li. 1.0 [Li 0.2 Mn 0.425 Ni 0.2 Fe 0.025 Mg 0.025 Al 0.025 Ti 0.025 Nb0.025 Mo 0.025 Sn 0.025 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material.

[0085] Comparative Example 1

[0086] Li 1.0 [Li 0.15 Mn 0.5 Ni 0.35 O2 cobalt-free lithium-rich manganese-based cathode material, which does not contain the element M, is prepared as follows:

[0087] (1) Weigh 10 mol of metal elements from the precursor raw materials, wherein the ratio of each metal element Mn:Ni is 5.882:4.118 by molar mass. Mix the aqueous solutions of manganese sulfate and nickel sulfate to prepare a 2M mixed solution. Weigh 10 mol of sodium hydroxide to prepare a 4M precipitant.

[0088] (2) Weigh 10 mol of ammonia water to prepare a 1 M complexing agent; add the mixed solution, precipitant and complexing agent to a 5 L reactor containing 1 L of deionized water at a rate of 2 mL / min. The temperature inside the reactor is kept constant at 50 °C and the stirring rate is 400 rpm. During the entire reaction, the pH value inside the reactor is kept at 10. After the addition is complete, react for 12 h, then filter, wash, and vacuum dry at 120 °C for 24 h to obtain the precursor material.

[0089] (3) Weigh 20 g of the precursor material prepared in step (2), weigh 0.5 g of MXene nanosheets, and weigh Li 1.0 [Li 0.15 Mn 0.5 Ni 0.35 4.97 g of lithium hydroxide (1.05 times the stoichiometry of O2) was thoroughly mixed in a ball mill for 4 hours.

[0090] (4) Weigh 1 g of the mixture prepared in step (2) and place it on carbon cloth for the first heat treatment in an argon atmosphere. The current is 10 A and the duration of the current is 10 s to obtain powder after the first heat treatment. Then, grind the prepared powder and perform a second heat treatment (argon atmosphere) with a current of 12 A and a duration of the current is 20 s to obtain Li. 1.0 [Li 0.15 Mn 0.5 Ni 0.35 O2 cobalt-free lithium-rich manganese-based cathode material.

[0091] Comparative Example 2

[0092] Li 1.0 [Li 0.15 Mn0.45 Ni 0.1 Fe 0.1 Mg 0.1 Al 0.1 O2 cobalt-free lithium-rich manganese-based cathode material, prepared by high-temperature calcination instead of ultra-fast Joule heat treatment, is as follows:

[0093] (1) Weigh 10 mol of metal elements from the precursor raw materials, wherein the ratio of each metal element Mn:Ni:Fe:Mg:Al by molar mass is 5.294:1.176:1.176:1.176:1.176. Mix the aqueous solutions of manganese sulfate, nickel sulfate, ferric sulfate, magnesium sulfate and aluminum sulfate to prepare a 2M mixed solution.

[0094] (2) Weigh 10 mol of sodium hydroxide to prepare a 4 M precipitant; weigh 10 mol of ammonia to prepare a 1 M complexing agent; add the mixed solution, precipitant and complexing agent simultaneously to a 5 L reactor containing 1 L of deionized water at a rate of 2 mL / min. The temperature inside the reactor is kept constant at 50 °C and the stirring rate is 400 rpm. During the entire reaction, the pH value inside the reactor is kept at 10. After the addition is complete, react for 12 h, then filter, wash, and vacuum dry at 120 °C for 24 h to obtain the precursor material.

[0095] (3) Weigh 20 g of the precursor material prepared in step (2), weigh 0.5 g of MXene nanosheets, and weigh Li 1.0 [Li 0.15 Mn 0.45 Ni 0.1 Fe 0.1 Mg 0.1 Al 0.1 4.97 g of lithium hydroxide (1.05 times the stoichiometry of O2) was thoroughly mixed in a ball mill for 4 hours.

[0096] (4) The mixture prepared in step (3) is sintered in a muffle furnace (sintered at 550°C for 5 h, then calcined at 850°C for 12 h), and then naturally cooled to room temperature to obtain Li. 1.0 [Li 0.15 Mn 0.45 Ni 0.1 Fe 0.1 Mg 0.1 Al 0.1 O2 cobalt-free lithium-rich manganese-based cathode material.

[0097] Comparative Example 3

[0098] Li 1.0 [Li 0.15 Mn 0.45 Ni 0.1Fe 0.1 Mg 0.1 Al 0.1 O2 cobalt-free lithium-rich manganese-based cathode material, without the addition of two-dimensional MXene nanomaterials, is prepared as follows:

[0099] (1) Weigh 10 mol of metal elements from the precursor raw materials, wherein the ratio of each metal element Mn:Ni:Fe:Mg:Al by molar mass is 5.294:1.176:1.176:1.176:1.176. Mix the aqueous solutions of manganese sulfate, nickel sulfate, ferric sulfate, magnesium sulfate and aluminum sulfate to prepare a 2M mixed solution.

[0100] (2) Weigh 10 mol of sodium hydroxide to prepare a 4 M precipitant; weigh 10 mol of ammonia to prepare a 1 M complexing agent; add the mixed solution, precipitant and complexing agent simultaneously to a 5 L reactor containing 1 L of deionized water at a rate of 2 mL / min. The temperature inside the reactor is kept constant at 50 °C and the stirring rate is 400 rpm. During the entire reaction, the pH value inside the reactor is kept at 10. After the addition is complete, react for 12 h, then filter, wash, and vacuum dry at 120 °C for 24 h to obtain the precursor material.

[0101] (3) Weigh 20 g of the precursor material prepared in step (2), and weigh Li 1.0 [Li 0.15 Mn 0.45 Ni 0.1 Fe 0.1 Mg 0. 1Al 0.1 Lithium hydroxide (7.65 g) with an O2 stoichiometric ratio of 1.05 was thoroughly mixed in a ball mill for 4 hours.

[0102] (4) Weigh 1 g of the mixture prepared in step (3) and place it on carbon cloth for the first heat treatment in an argon atmosphere. The current is 10 A and the duration of the heat treatment is 10 s to obtain powder after the first heat treatment. Then, grind the prepared powder and perform a second heat treatment (argon atmosphere) with a current of 12 A and a duration of 20 s to obtain Li. 1.0 [Li 0.15 Mn 0.45 Ni 0.1 Fe 0.1 Mg 0.1 Al 0.1 O2 high-entropy cobalt-free lithium-rich manganese-based cathode material.

[0103] Comparative Example 4

[0104] Li 1.0 [Li 0.15 Mn 0.45Ni 0.1 Fe 0.1 Mg 0.1 Al 0.1 O2 cobalt-free lithium-rich manganese-based cathode material, without the addition of two-dimensional MXene nanomaterials, and using high-temperature calcination instead of ultra-fast Joule heat treatment, is prepared as follows:

[0105] (1) Weigh 10 mol of metal elements from the precursor raw materials, wherein the ratio of each metal element Mn:Ni:Fe:Mg:Al by molar mass is 5.294:1.176:1.176:1.176:1.176. Mix the aqueous solutions of manganese sulfate, nickel sulfate, ferric sulfate, magnesium sulfate and aluminum sulfate to prepare a 2M mixed solution.

[0106] (2) Weigh 10 mol of sodium hydroxide to prepare a 4 M precipitant; weigh 10 mol of ammonia to prepare a 1 M complexing agent; add the mixed solution, precipitant and complexing agent simultaneously to a 5 L reactor containing 1 L of deionized water at a rate of 2 mL / min. The temperature inside the reactor is kept constant at 50 °C and the stirring rate is 400 rpm. During the entire reaction, the pH value inside the reactor is kept at 10. After the addition is complete, react for 12 h, then filter, wash, and vacuum dry at 120 °C for 24 h to obtain the precursor material.

[0107] (3) Weigh 20 g of the precursor material prepared in step (2), and weigh Li 1.0 [Li 0.15 Mn 0.45 Ni 0.1 Fe 0.1 Mg 0. 1Al 0.1 4.97 g of lithium hydroxide (1.05 times the stoichiometry of O2) was thoroughly mixed in a ball mill for 4 hours.

[0108] (4) The mixture prepared in step (3) is sintered in a muffle furnace (sintered at 550℃ for 5 h and then calcined at 850℃ for 12 h), and then naturally cooled to room temperature to obtain Li. 1.0 [Li 0.15 Mn 0.45 Ni 0.1 Fe 0.1 Mg 0.1 Al 0.1 O2 cobalt-free lithium-rich manganese-based cathode material.

[0109] Electrochemical performance tests were performed on the cathode material samples prepared in Examples 1-5 and Comparative Examples 1-4.

[0110] Test method: The high-entropy cobalt-free lithium-rich manganese-based cathode materials prepared in Examples 1-5 and Comparative Examples 1-4 were mixed with conductive carbon black and PVDF at a mass ratio of 90:5:5. An appropriate amount of 1-methyl-2-pyrrolidone was added and the mixture was ball-milled for 1 hour to form a slurry. The slurry was then uniformly coated onto an aluminum sheet, dried, and pressed to form a cathode sheet. A coin cell was assembled using a lithium metal sheet as the anode. Charge-discharge cycle tests were conducted under 1C conditions. The test results are shown in Table 1.

[0111] Table 1. Test results of the examples and comparative examples.

[0112] .

[0113] Depend on Figure 1-2 As can be seen from the test results in Table 1, the coin cells prepared using the high-entropy cobalt-free lithium-rich manganese-based cathode materials obtained in Examples 1-5 exhibit excellent performance. In particular, Example 4, where the high-entropy cobalt-free lithium-rich manganese-based material is formed by the aggregation of micron-sized primary particles into secondary particles, has a first-cycle discharge specific capacity as high as 286.5 mAh / g, an initial coulombic capacity as high as 87.1%, a 2C discharge capacity as high as 210.2 mAh / g, and retains 89.2% of its capacity after 600 cycles, significantly improving the structural stability of the material.

[0114] Comparative Example 1 did not employ a high-entropy multi-principal-element design and did not introduce the inert ion M. Compared to Example 1, the battery performance was significantly reduced, with a capacity retention rate of only 74.7% after 600 cycles, a decrease of 14.4% compared to Example 1.

[0115] Compared to Example 1, Comparative Example 2 did not employ Joule heat treatment but instead underwent ordinary high-temperature calcination, resulting in a significant decrease in battery performance, which was 3.5% lower than that of Example 1.

[0116] Compared to Example 1, Comparative Example 3 did not include two-dimensional MXene nanomaterials. As can be seen from the data, the battery performance decreased significantly, by 8.2% compared to Example 1.

[0117] Compared to Example 1, Comparative Example 4 did not include two-dimensional MXene nanomaterials and used high-temperature calcination instead of ultra-fast Joule heat treatment. As can be seen from the data, the battery performance decreased significantly, with a capacity retention rate of only 73.0% after 600 cycles, which is 16.4% lower than that of Example 1.

[0118] Furthermore, the data from Comparative Examples 2-4 show that two-dimensional MXene nanomaterials and ultrafast Joule heat treatment have a synergistic effect, and the synergy between the two can significantly improve the structural stability of the material.

[0119] Finally, it should be noted that the above specific embodiments are only used to describe the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation of the present invention and is not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions or improvements can be made to some or all of the technical features. These modifications, equivalent substitutions, and improvements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a high-entropy cobalt-free lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: S1, according to the composition of high-entropy cobalt-free lithium-rich manganese-based cathode material Li 1+x Mn a Ni b M c O 2+δ The molar ratios of each element are weighed and dissolved in water to prepare a mixed solution; wherein M is at least three of Mg, Al, Sn, Ti, Zr, Nb, Mo, W, Y, Fe, and V, and x+a+b+c=1, where x, a, b, and c are all molar ratios, x is the excess coefficient of Li, and δ is the non-stoichiometric coefficient of oxygen. S2. React the mixed solution with a precipitant and a complexing agent to obtain the precursor material; S3. The precursor material, Li compound, and two-dimensional MXene nanomaterial are ball-milled and mixed to obtain a mixed material; the amount of the two-dimensional MXene nanomaterial added accounts for 0.1-3 wt% of the total amount of the precursor material and Li compound. S4. The mixed material is subjected to Joule heat treatment to obtain a high-entropy cobalt-free lithium-rich manganese-based cathode material; the Joule heat treatment includes: applying a current of 8-12A for 5-15s for the first heat treatment; applying a current of 10-15A for 10-30s for the second heat treatment; and the Joule heat treatment is carried out in an argon protective atmosphere.

2. The method for preparing a high-entropy cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, The compounds of Mn, Ni, M, and Li are selected from one or more of the oxalates, acetates, sulfates, nitrates, and halides of Mn, Ni, M, and Li, respectively.

3. The method for preparing a high-entropy cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, 0.4≤a≤0.6, 0.1≤b≤0.3, 0≤x≤0.

3.

4. The method for preparing a high-entropy cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, The precipitant is a hydroxide precipitant or a carbonate precipitant, and the complexing agent is an ammonia solution.

5. The method for preparing a high-entropy cobalt-free lithium-rich manganese-based cathode material according to claim 4, characterized in that, When using a hydroxide precipitant, the pH of the system is maintained between 10 and 12 in step S2; when using a carbonate precipitant, the pH of the system is maintained between 7 and 9 in step S2.

6. A high-entropy, cobalt-free, lithium-rich manganese-based cathode material, characterized in that, Prepared by the method described in any one of claims 1-5.

7. The application of the high-entropy cobalt-free lithium-rich manganese-based cathode material as described in claim 6 in lithium-ion batteries.

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