A modified cobalt-free lithium-rich manganese-based positive electrode material and a preparation method thereof

Abstract

This application belongs to the field of lithium-ion battery cathode material technology. Addressing the technical problem that existing cobalt-free lithium-rich layered oxide modification strategies cannot simultaneously achieve high reversible capacity and excellent rate performance, this application provides a modified cobalt-free lithium-rich manganese-based cathode material and its preparation method. A lithium-rich manganese-based base material is synthesized by calcining an Al-doped nickel-manganese hydroxide precursor with lithium hydroxide monohydrate (LiOH·H2O). This base material is then mixed with ammonium fluoride and dispersed in the organic solvent N-methyl-2-pyrrolidone. The solid portion is then calcined to obtain a fluorinated, cobalt-free, lithium-rich manganese-based cathode material. The resulting interface structure achieves a synergistic decoupling effect between ion conduction and electronic insulation, resulting in ultra-high capacity and excellent rate performance of the cobalt-free lithium-rich manganese system.

Description

Technical Field

[0001] This application belongs to the technical field of lithium-ion battery cathode materials, specifically relating to a modified cobalt-free lithium-rich manganese-based cathode material and its preparation method. Background Technology

[0002] With the increasing demand for high energy density in lithium-ion batteries, lithium-rich layered oxides (LLOs) have become highly promising next-generation cathode materials due to their ultra-high reversible specific capacity. Based on this, cobalt-free lithium-rich layered oxides (Cf-LLOs) have been developed. The removal of cobalt reduces costs and improves environmental friendliness, and their unique structure has attracted widespread attention due to their significant anionic redox activity. However, the Ni content in Cf-LLOs... 2+ Easy migration exacerbates Li / Ni mixing and blocks Li + The diffusion channel leads to a decrease in reversible capacity and rate performance, which severely restricts the application of Cf-LLOs.

[0003] To address the aforementioned issues, existing modification strategies are mainly categorized into two types: bulk doping and surface / interface modulation. Bulk doping enhances the stability of the TM–O (Transition Metal-Oxygen) bond by introducing elements such as Al and Zr to mitigate structural transformation, while surface / interface modulation improves interfacial performance by constructing buffer layers. Fluorine-containing compounds have attracted significant attention due to their excellent stability; LiF interfacial layers and F doping can improve some of the electrochemical properties of the materials. However, existing approaches still have significant shortcomings, specifically: bulk doping struggles to suppress irreversible oxygen release and interfacial side reactions; the gas-phase fluorination process in fluorine-containing modification is complex and suffers from poor rate performance; and fluorine doping is deficient in improving rate performance and suppressing manganese dissolution. Overall, it is impossible to simultaneously achieve high reversible capacity and excellent rate performance. Summary of the Invention

[0004] This application addresses the technical problem that existing cobalt-free lithium-rich layered oxide modification strategies cannot simultaneously achieve high reversible capacity and excellent rate performance improvement, by providing a modified cobalt-free lithium-rich manganese-based cathode material and its preparation method.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] In one aspect, this application proposes a method for preparing a modified cobalt-free lithium-rich manganese-based cathode material, comprising: mixing an Al-doped nickel-manganese hydroxide precursor Ni x Mn y Al z(OH)2 and LiOH·H2O, after calcination, yield lithium-rich manganese-based basic material Li. a Ni b Mn c Al d O2, the Ni x Mn y Al z In (OH)₂, the molar ratios x, y, and z of the elements satisfy:

[0007] x: 0.2-0.5;

[0008] y: 0.5-0.8;

[0009] z: 0.01-0.08;

[0010] Li a Ni b Mn c Al d In O2, the molar ratios of the elements a, b, c, and d satisfy:

[0011] a: 1.10-1.25;

[0012] b: 0.15-0.45;

[0013] c: 0.50-0.70;

[0014] d: 0.01-0.05;

[0015] A lithium-rich manganese-based base material was mixed with NH4F to obtain an intermediate mixture;

[0016] The intermediate mixture was dispersed in N-methyl-2-pyrrolidone to obtain a dispersion mixture;

[0017] The solid fraction was obtained from the dispersion mixture and then calcined to obtain a fluorinated, cobalt-free, lithium-rich manganese-based cathode material.

[0018] Furthermore, the lithium-rich manganese-based base material Li a Ni b Mn c Al d In O2, the molar ratios of the elements a, b, c, and d satisfy:

[0019] a: 1.16;

[0020] b: 0.20;

[0021] c: 0.59;

[0022] d: 0.02.

[0023] Furthermore, the mixed Al-doped nickel-manganese hydroxide precursor Ni x Mn y Al z The methods for reacting (OH)2 with LiOH·H2O include:

[0024] For Ni x Mn y Al z (OH)2 and LiOH·H2O were ball-milled in a solvent to obtain a slurry;

[0025] The slurry is dried to obtain a dried solid powder;

[0026] The dried solid powder is ground to obtain abrasive material;

[0027] The abrasive is subjected to three-stage calcination to achieve complete phase formation, thereby obtaining a lithium-rich manganese-based base material; in the three-stage calcination, the calcination temperature of each stage increases sequentially.

[0028] Furthermore, the Ni x Mn y Al z When (OH)2 and LiOH·H2O are ball-milled in a solvent, the molar ratio of Li to M is (1.4-1.5):1; where M = Ni + Mn + Al.

[0029] Furthermore, the three-stage calcination method includes:

[0030] First stage: Slowly heat to 400-500℃ and keep warm;

[0031] Second stage: Quickly heat to 700℃ and keep warm;

[0032] Third stage: Quickly heat to 800-900℃ and keep warm.

[0033] Furthermore, the holding temperature after the first and second stages of calcination is 4-6 h, and the holding time after the third stage of calcination is 8-12 h.

[0034] Furthermore, the mass fraction of NH4F in the intermediate mixture is 1 wt%-5 wt%.

[0035] Furthermore, the method for obtaining the solid portion from the dispersion mixture includes: subjecting the dispersion mixture to high-speed centrifugal vibration, followed by drying to obtain the solid portion.

[0036] Furthermore, the calcination temperature for calcining the solid portion is 300℃-500℃.

[0037] Secondly, this application proposes a modified cobalt-free lithium-rich manganese-based cathode material, which is prepared using the above-mentioned method for preparing a modified cobalt-free lithium-rich manganese-based cathode material.

[0038] Compared with the prior art, this application has the following beneficial effects:

[0039] This application proposes a modified cobalt-free lithium-rich manganese-based cathode material and its preparation method, which uses a mixed Al-doped nickel-manganese hydroxide precursor Ni. x Mn y Al z (OH)₂ is calcined with LiOH·H₂O and then mixed with NH₄F. Different intermediate mixtures are obtained based on different mass percentages of NH₄F. This mixture is then dispersed in N-methyl-2-pyrrolidone, and the solid portion is calcined to obtain a fluorinated, cobalt-free, lithium-rich manganese-based cathode material. The preparation method of this application enables the construction of an integrated, self-passivated, fast ion-phase interface on the surface of a cobalt-free, lithium-rich layered oxide. Fluorination treatment, by regulating the redox reaction activity between anions and cations, thermodynamically stabilizes the lattice oxygen, effectively suppressing irreversible redox reactions and the resulting structural degradation. Simultaneously, two key synergistic functions are achieved at the interface layer: the LiF component, as a stable, ionicly conductive electronic insulator, effectively isolates side reactions between the cathode material and the electrolyte; while the spinel phase constructs a dedicated fast ion-phase interface at the interface. + Transport Channel. The interface structure of the prepared modified cobalt-free lithium-rich manganese-based cathode material achieves a synergistic decoupling effect between ion conduction and electronic insulation. It is precisely because of the aforementioned technical effects that the modified cobalt-free lithium-rich manganese-based cathode material prepared in this application has been verified to achieve a conductivity of 310.11 mAh g⁻¹. -1 It has a high reversible specific capacity, an initial coulomb efficiency of 87.7%, and excellent rate performance. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded 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.

[0041] Figure 1 This is a schematic diagram illustrating the principle of the preparation method of the modified cobalt-free lithium-rich manganese-based cathode material in the embodiments of this application;

[0042] Figure 2 Spectra of electronic states density for O 2p orbitals and 3d orbitals in transition metals (TM) were calculated for different materials; among them, Figure 2The 'a' in the text corresponds to LNMA (lithium-rich manganese-based basic material). Figure 2 In this context, 'b' corresponds to the NH4F-modified material, where fluorine is bonded to the transition metal. Figure 2 The 'c' in the text corresponds to the NH4F-modified material, where fluorine replaces oxygen.

[0043] Figure 3 In the image, 'a' is a transmission electron microscope image of LNMA. Figure 3 In the diagram, b represents the high-resolution pattern image within the box in a;

[0044] Figure 4 In the image, a is a transmission electron microscope image of LNMA-3, b is an image obtained using the high-resolution mode of transmission electron microscopy, cd is the Fourier transform image of the corresponding region, and e is the energy spectrum image of LNMA-3 and its elements; where LNMA-3 represents the mass percentage of NH4F.

[0045] Figure 5 This is a schematic diagram of the analysis results of energy dispersive spectroscopy point scanning performed in the high-angle annular dark-field scanning transmission electron microscope mode of LNMA-3.

[0046] Figure 6 In the diagram, a represents the XRD (X-ray Diffraction) spectra of LNMA and LNMA-x (x=1, 3, 5), b represents the XRD spectrum of LNMA-3 after refinement using the solid solution model, c represents the Raman spectra of LNMA and LNMA-x (x=1, 3, 5), dg represents the fine XPS (X-ray Photoelectron Spectroscopy) spectra of LNMA and LNMA-x (x=1, 3, 5), d corresponds to the Mn 3s level, e corresponds to the Ni 2p level, f corresponds to the O 1s level, and g corresponds to the F 1s level.

[0047] Figure 7 The initial charge-discharge curves are shown for LNM (a lithium-rich manganese-based base material without Al) and LNM-3 (3 represents the mass percentage of NH4F during modification) after fluorination modification.

[0048] Figure 8 In the diagram, a represents the initial charge-discharge curves of LNMA and LNMA-x (x=1, 3, 5), b represents the rate performance of LNMA and LNMA-x (x=1, 3, 5), c represents the performance of cycling at a rate of 0.5 C after activation with a current of 0.1 C in the first cycle, and d represents the performance of cycling at a rate of 1 C after activation with a current of 0.1 C in the first cycle. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0050] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0051] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0052] Currently, lithium-ion batteries, with their advantages of high energy density, long cycle life, and low environmental pollution, are widely used in multiple core fields such as consumer electronics, electric vehicles, and energy storage systems. The rapid development of electric vehicles and large-scale energy storage, in particular, has placed increasingly higher demands on the energy density of lithium-ion batteries, making the development of electrode materials with higher energy density one of the core directions of industry development. As a core component of lithium-ion batteries, cathode materials directly determine key performance characteristics such as energy density and cycle stability. Therefore, the development of high-performance cathode materials is a key breakthrough in promoting the technological upgrade of lithium-ion batteries. Among many cathode materials, lithium-rich layered oxides, due to their ultra-high reversible specific capacity, far exceeding traditional ternary cathode materials and lithium iron phosphate cathode materials, have become highly promising next-generation high-energy-density cathode materials, attracting widespread attention and in-depth research within the industry. Building upon this foundation, researchers have further developed cobalt-free lithium-rich layered oxides (Cf-LLOs). The biggest advantage of this material is the removal of costly and environmentally unfriendly cobalt, effectively reducing the production cost of cathode materials and improving their environmental friendliness, aligning with the green and low-carbon development trend of the new energy industry. Simultaneously, Cf-LLOs possess a unique layered crystal structure, which endows them with significant anionic redox activity. This characteristic gives them greater potential for improving battery energy density, further expanding their application prospects in high-energy-density lithium-ion batteries. Despite the significant advantages of Cf-LLOs in terms of cost, environmental friendliness, and energy density potential, their inherent structural defects severely restrict their commercial application in practical situations. Specifically, the nickel ions (Ni²⁺) contained in Cf-LLOs... + Lithium ions (Li) have strong migration capabilities, and this migration exacerbates the migration of lithium ions. + ) and nickel ions (Ni²) + The mixing of Li and Ni directly blocks the diffusion channels of lithium ions within the material. Smooth lithium ion diffusion is crucial for the charging and discharging process of lithium-ion batteries. Blocked channels lead to a decrease in the battery's reversible capacity and a significant deterioration in rate performance. This performance degradation problem prevents Cf-LLOs from meeting the high-performance requirements of consumer electronics, electric vehicles, and other fields, becoming a core bottleneck hindering their commercial application.

[0053] To address the issues of Li / Ni mixing, hindered lithium-ion diffusion, and the resulting decline in reversible capacity and rate performance in Cf-LLOs, the industry has conducted extensive modification research. Currently, the modification strategies mainly fall into two categories: bulk doping and surface / interface modulation. Bulk doping involves introducing heterogeneous elements such as aluminum and zirconium into the bulk crystal phase of Cf-LLOs. These elements can form more stable transition metal-oxygen bonds with transition metals and oxygen in the material, thereby enhancing the stability of the crystal structure, mitigating structural transformations during charge and discharge, and reducing Li / Ni mixing. Surface / interface modulation, on the other hand, involves constructing a buffer layer on the surface of the Cf-LLOs material to optimize the interfacial performance between the material and the electrolyte, reducing interfacial side reactions, and also blocking Ni²⁺ to some extent. + The migration of lithium ions improves the diffusion environment. Among the many surface / interface modulated and bulk doped materials, fluorine-containing compounds have attracted much attention from researchers due to their excellent chemical and electrochemical stability, which can effectively improve the cycling stability of materials. Among them, lithium fluoride interface layer modification and fluorine doping are the two most widely used methods. Both of these methods can improve some of the electrochemical performance of Cf-LLOs to a certain extent and alleviate their performance degradation problem.

[0054] While existing solutions such as bulk doping, surface / interface modulation, and fluorine modification can alleviate the performance defects of Cf-LLOs to some extent, these solutions still have significant shortcomings and fail to fundamentally solve the problem, thus failing to simultaneously achieve a dual improvement in high reversible capacity and excellent rate performance. Specifically, while bulk doping technology can enhance the stability of TM–O bonds and mitigate crystal structure transformation, it is difficult to effectively suppress irreversible oxygen release and interfacial side reactions between the material and electrolyte during charge and discharge. Irreversible oxygen release leads to material structure collapse, and interfacial side reactions consume electrolyte and active materials, ultimately resulting in battery performance degradation. Among fluorine modification solutions, gas-phase fluorination can achieve fluorine doping or interfacial modification, but this process is complex, requires harsh reaction conditions, and the rate performance of the modified material is still poor, failing to meet the requirements of high-power applications. Conventional fluorine doping technology, while improving the cycle stability of the material to some extent, is significantly lacking in improving rate performance and suppressing manganese dissolution. Manganese dissolution leads to the destruction of the material's crystal structure, further exacerbating performance degradation. In summary, existing modification schemes all have their own limitations, failing to simultaneously improve high reversible capacity and excellent rate performance, and also struggling to solve the core bottlenecks faced by Cf-LLOs in practical applications. Therefore, developing a modification scheme that can overcome the limitations of existing technologies and comprehensively improve the electrochemical performance of Cf-LLOs has become an urgent technical problem to be solved in the industry.

[0055] Based on the above problems, this application proposes a modified cobalt-free lithium-rich manganese-based cathode material and its preparation method. The following is a detailed description of this application in conjunction with the embodiments and accompanying drawings.

[0056] As one embodiment of the preparation method of the modified cobalt-free lithium-rich manganese-based cathode material of this application, it may include:

[0057] (1) Mixed Al-doped nickel-manganese hydroxide precursor Ni x Mn y Al z (OH)2 and LiOH·H2O, after calcination, yield lithium-rich manganese-based basic material Li. a Ni b Mn c Al d O2.

[0058] Ni x Mn y Al z In (OH)₂, the molar ratios x, y, and z of the elements satisfy:

[0059] x: 0.2-0.5;

[0060] y: 0.5-0.8;

[0061] z: 0.01-0.08;

[0062] Li a Ni b Mn c Al d In O2, the molar ratios of the elements a, b, c, and d satisfy:

[0063] a: 1.10-1.25;

[0064] b: 0.15-0.45;

[0065] c: 0.50-0.70;

[0066] d: 0.01-0.05.

[0067] The optimal molar ratio for Li ensures that the excess Li required for lithium-rich properties is maintained while avoiding crystal structure defects caused by excessive Li, thus guaranteeing the stable formation of the lithium-rich layered structure. The optimal molar ratio for Ni better balances the material's electrochemical activity and structural stability. The optimal molar ratio for Al precisely enhances the stability of the TM–O bond (transition metal-oxygen bond), effectively mitigating Li / Ni mixing and avoiding performance issues caused by improper Al doping. The optimal molar ratio for O better matches the crystal structure requirements of cobalt-free lithium-rich layered oxides (Cf-LLOs), improving the material's crystal structure regularity and reducing structural defects. This lays a solid foundation for subsequent fluorination modification and electrochemical performance enhancement. Furthermore, precise proportioning improves the consistency of material performance in batch production, facilitating parameter control for industrial mass production.

[0068] like Figure 1 The diagram shown illustrates the principle of the modified cobalt-free lithium-rich manganese-based cathode material preparation method in this embodiment. After mixing the Al-doped nickel-manganese hydroxide precursor with LiOH·H₂O as the lithium source, Li can be uniformly dispersed in the Al-doped nickel-manganese hydroxide precursor. During subsequent calcination, Li enters the crystal structure of the Al-doped nickel-manganese hydroxide precursor, forming a lithium-rich layered structure. Simultaneously, Al, as a bulk dopant, can form a uniform transition metal hydroxide system with Ni and Mn elements in advance, forming stable TM–O bonds. This application strictly controls the molar ratio of each element. Excessive Li ensures lithium-rich characteristics, while the combined effect of the Ni, Mn, and Al ratios balances the structural stability and electrochemical activity of the material. The O ratio matches the crystal structure requirements of the lithium-rich layered oxide.

[0069] This application achieves uniform mixing of Al-doped nickel-manganese hydroxide precursor and lithium source, providing a homogeneous raw material system for the formation of lithium-rich layered structures. Strict control of the molar ratio allows for the preliminary determination of the material's crystal structure, avoiding structural defects caused by elemental imbalances. Furthermore, the early incorporation of Al lays the groundwork for mitigating Li / Ni mixing and enhancing the stability of the TM–O bond. In addition, the uniformity of mixing directly affects the performance consistency of the material after subsequent calcination, reducing performance degradation caused by localized structural inhomogeneities.

[0070] (2) The lithium-rich manganese-based base material LNMA is mixed with NH4F to obtain an intermediate mixture.

[0071] Introducing a fluorine source prepares the material for subsequent fluorination modification, achieving a combination of bulk doping and fluorine modification. NH4F, as a mild fluorine source, exhibits good stability and a moderate fluorine content. When mixed with lithium-rich manganese-based materials, fluorine can be uniformly dispersed in the intermediate mixture. During subsequent calcination, NH4F decomposes to generate fluoride ions (F). - ), part of F - It will be doped into the bulk structure of the material, replacing some oxygen ions and enhancing the stability of the TM–O bond, while another part of the F... - A LiF buffer layer will form on the material surface, enabling surface interface regulation. Uniform mixing of the fluorine source with the initial mixture ensures the uniformity of subsequent fluorination modification, avoiding performance inconsistencies caused by excessively high or low local fluorine content.

[0072] (3) Disperse the intermediate mixture in N-methyl-2-pyrrolidone to obtain a dispersion mixture.

[0073] The intermediate mixture is uniformly dispersed in a dispersion medium to avoid particle agglomeration, ensuring uniform reaction of elements during subsequent calcination and improving the performance consistency of the final material. LNMA and NH4F in the intermediate mixture are both solid particles; direct calcination easily leads to particle agglomeration, resulting in uneven elemental reaction and localized structural defects. NMP (N-Methyl-2-pyrrolidone) serves as an excellent dispersion medium. Its strong polarity allows it to adsorb onto the surface of solid particles, reducing interparticle forces. Simultaneously, its good solubility allows for slight dissolution of some soluble raw materials, further achieving uniform element dispersion and preventing performance inconsistencies caused by agglomeration. This ensures the formation of a uniform crystal structure and surface modification layer during subsequent calcination.

[0074] (4) Obtain the solid part from the dispersion mixture and then calcine the solid part to obtain the fluorinated modified cobalt-free lithium-rich manganese-based cathode material.

[0075] The dispersion medium is removed by drying, followed by calcination to achieve crystallization and fluorination modification of the raw materials, ultimately forming a manganese-based cathode material with excellent performance. First, the solid portion is obtained from the dispersion mixture, essentially removing the NMP (nitrogen peroxide) that serves as the dispersion medium, allowing the raw material particles to re-aggregate while maintaining the uniformity of the dispersion. During the subsequent calcination process, NH4F decomposes into NH3 and HF. The generated HF reacts with residual alkali on the LNMA surface to form LiF. On the surface and near-surface regions of the LNMA, HF further reacts with metal ions to generate corresponding metal fluorides. Simultaneously, due to the F... - and O 2- The ionic radii are similar, and surface oxygen may be partially replaced by fluorine, thus effectively suppressing the formation of oxygen vacancies. Furthermore, the hydrogen released from the decomposition of NH3 may convert Mn... 4+ Restored to Mn 3+ This helps to form a spinel-like phase. Ultimately, a fluorinated, cobalt-free, lithium-rich manganese-based cathode material is obtained.

[0076] In some embodiments of this application, a mixed Al-doped nickel-manganese hydroxide precursor Ni x Mn y Al z The methods for reacting (OH)2 with LiOH·H2O include:

[0077] For Ni x Mn y Al z (OH)2 and LiOH·H2O were ball-milled in a solvent to obtain a slurry;

[0078] The slurry is dried to obtain a dried solid powder;

[0079] The dried solid powder is ground to obtain abrasive material;

[0080] The abrasive is subjected to three-stage calcination to achieve complete phase formation, thereby obtaining a lithium-rich manganese-based base material; in the three-stage calcination, the calcination temperature of each stage increases sequentially.

[0081] In this embodiment, the preparation of lithium-rich manganese-based basic materials is optimized into a process of ball milling slurry preparation, drying, grinding, and three-stage gradient calcination. Ball milling slurry preparation allows Ni to... x Mn y Al z(OH)₂ and LiOH·H₂O are fully dispersed in the solvent to prevent solid particle agglomeration and ensure uniform Li element distribution, providing a homogeneous raw material system for subsequent phase formation. Drying and grinding steps remove the solvent and refine the blocky slurry, increasing the specific surface area of ​​the raw material and facilitating heat transfer and reaction during subsequent calcination. Three-stage gradient heating calcination achieves gradual phase formation of the raw material, avoiding incomplete crystal structures, impurity phases, or structural defects caused by excessively rapid heating. This ensures the formation of a regular and stable lithium-rich layered structure in the lithium-rich manganese-based material, providing high-quality initial raw materials for subsequent fluorine modification and final material performance improvement. Simultaneously, the refined process improves the operability and controllability of the process, reducing performance fluctuations in industrial production.

[0082] In some embodiments of this application, the three-stage calcination method includes:

[0083] First stage: Slowly heat to 400-500℃ and hold at that temperature. This slowly removes residual solvents and moisture from the grinding material, allowing LiOH·H2O to gradually lose its water of crystallization and the Al-doped nickel-manganese hydroxide precursor to initially decompose. This avoids rapid heating that could cause water to evaporate quickly, generating bubbles and leading to pores and defects in the crystal structure.

[0084] The second stage involves rapid heating to 700℃ and holding at that temperature. This quickly promotes the initial reaction between Li and transition metal (Ni, Mn, Al) oxides, forming a preliminary lithium-rich layered structure, reducing the formation of intermediate impurity phases, and improving structural regularity.

[0085] The third stage involves rapid calcination to 800-900℃ and holding at that temperature. This process achieves complete densification of the crystal structure, forming stable TM–O bonds, further mitigating Li / Ni mixing. The gradient heating mode balances phase formation quality and production efficiency, avoiding particle sintering and agglomeration problems caused by single high-temperature calcination. This ensures that the lithium-rich manganese-based base material possesses good structural stability and electrochemical activity, providing a high-quality raw material foundation for subsequent modification steps.

[0086] As an example, in the three-stage calcination, the holding time after the first and second stages of calcination is 4-6 hours, and the holding time after the third stage of calcination is 8-12 hours.

[0087] In some embodiments of this application, Ni x Mn y Al zWhen (OH)₂ and LiOH·H₂O are ball-milled in a solvent, the molar ratio of Li to M is (1.4-1.5):1; where M = Ni + Mn + Al. The 1.4-1.5 times excess of Li ensures that Li fully participates in the phase-forming reaction during subsequent calcination, forming a lithium-rich layered structure and avoiding incomplete phase formation and capacity reduction due to insufficient Li. This ratio balances the relationship between excess Li and structural stability, avoiding crystal structure distortion caused by excessive Li, while ensuring that Al fully exerts its bulk doping effect, forming a stable system with Li, Ni, and Mn, thus guaranteeing complete phase formation in the subsequent three-stage calcination.

[0088] In some embodiments of this application, the mass fraction of NH4F is 1 wt%-5 wt%. This avoids the problem of inappropriate fluorine content. Too low a fluorine content prevents the formation of a uniform surface LiF buffer layer and effective bulk fluorine doping, making it difficult to optimize interface performance and enhance structural stability. Too high a fluorine content leads to fluoride accumulation on the material surface, blocking lithium-ion diffusion channels, reducing rate performance, and potentially causing crystal structure defects. The dosage range in this embodiment matches the subsequent calcination steps, ensuring that the F produced by the decomposition of NH4F... - Uniformly distributed in the bulk phase and surface of the material, the fluorine doping in the bulk phase and the surface LiF buffer layer work synergistically to effectively suppress irreversible oxygen release and interfacial side reactions, reduce manganese dissolution, and further improve the cycling stability and rate performance of the material.

[0089] In some embodiments of this application, the calcination temperature for the solid portion is 300℃-500℃. This allows for more uniform bulk doping of fluorine and formation of the surface LiF layer, avoids fluorine loss due to high temperatures, improves the reversible capacity and rate performance of the material, and balances process efficiency with material performance.

[0090] In some embodiments of this application, the method for obtaining a solid fraction from a dispersion mixture includes: drying the dispersion mixture by high-speed centrifugation. The oscillation treatment can break up the agglomerated solid particles after centrifugation, allowing the solid particles to be redispersed uniformly, thus avoiding uneven reaction of the agglomerated particles during subsequent calcination, which could lead to problems such as localized structural defects and uneven fluorine modification.

[0091] The present application will be further illustrated by the following embodiments:

[0092] Example 1

[0093] (1) Mixed Al-doped nickel manganese hydroxide precursor Ni x Mn y Al z(OH)₂ and lithium hydroxide monohydrate LiOH·H₂O, after calcination, yield lithium-rich manganese-based basic material Li. a Ni b Mn c Al d O2.

[0094] First, weigh out a certain amount of Ni x Mn y Al z Weigh out the appropriate mass of LiOH·H2O according to the Li / M (M = Ni + Mn + Al) molar ratio of 1.4:1. Add Ni... x Mn y Al z (OH)₂, LiOH·H₂O, and an appropriate amount of ethanol were ball-milled together in a ball mill jar for 6 hours to obtain a slurry. The slurry was then dried overnight at 80°C to obtain a dried solid powder. The dried solid powder was thoroughly ground in an agate mortar and then transferred to an alumina crucible. Finally, it was calcined in a muffle furnace according to the following three-step procedure:

[0095] (i) Slow-cook to 400°C and hold for 5 hours. This process involves the initial phase formation of the material.

[0096] (ii) Quickly heat to 700°C and hold for 5 hours. This process is the process of lithium ions entering the crystal lattice.

[0097] (iii) Then quickly heat to 900°C and hold for 6 hours. This process can be repeated two or more times. This process is the complete phase formation process of the material.

[0098] A lithium-rich manganese-based base material, denoted as LNMA powder, was obtained as the initial mixture.

[0099] In the initial mixture, the molar ratio of the elements satisfies:

[0100] a: 1.16;

[0101] b: 0.20;

[0102] c: 0.59;

[0103] d: 0.02.

[0104] (2) Weigh a small amount of the LNMA powder prepared above and mix it with NH4F with a mass fraction of 3wt%, and record it as LNMA-3 to obtain an intermediate mixture.

[0105] (3) Disperse the intermediate mixture in an appropriate amount of N-methyl-2-pyrrolidone (NMP), and then sonicate and magnetically stir to ensure uniform dispersion to obtain a dispersed mixture.

[0106] (4) After centrifuging the dispersion mixture at high speed for 5-10 minutes, the adsorption uniformity of ammonium fluoride on the material surface is further improved by oscillation treatment.

[0107] (5) The shaken dispersion mixture was dried overnight at 80-100°C. After thorough grinding, it was transferred to an alumina crucible and calcined in a muffle furnace at 450°C for about 5 hours. Finally, a fluorinated modified cobalt-free lithium-rich manganese-based cathode material was obtained.

[0108] Example 2

[0109] (1) Mixed Al-doped nickel manganese hydroxide precursor Ni x Mn y Al z (OH)₂ and lithium hydroxide monohydrate LiOH·H₂O, after calcination, yield lithium-rich manganese-based basic material Li. a Ni b Mn c Al d O2.

[0110] First, weigh out a certain amount of Ni x Mn y Al z Weigh out the appropriate mass of LiOH·H2O according to the Li / M (M = Ni + Mn + Al) molar ratio of 1.5:1. Add Ni... x Mn y Al z (OH)₂, LiOH·H₂O, and an appropriate amount of ethanol were ball-milled together in a ball mill jar for 8 hours to obtain a slurry. The slurry was then dried overnight at 90°C to obtain a dried solid powder. The dried solid powder was thoroughly ground in an agate mortar and then transferred to an alumina crucible. Finally, it was calcined in a muffle furnace according to the following three-step procedure:

[0111] (i) Slow-cook to 400°C and hold for 5 hours. This process involves the initial phase formation of the material.

[0112] (ii) Quickly heat to 700°C and hold for 5 hours. This process is the process of lithium ions entering the crystal lattice.

[0113] (iii) Then quickly heat to 900°C and hold for 6 hours. This process can be repeated two or more times. This process is the complete phase formation process of the material.

[0114] A lithium-rich manganese-based base material, denoted as LNMA powder, was obtained as the initial mixture.

[0115] The molar ratios of the elements in the initial mixture satisfy the following:

[0116] a: 1.23;

[0117] b: 0.20;

[0118] c: 0.58;

[0119] d: 0.02.

[0120] (2) Weigh a small amount of the LNMA powder prepared above and mix it with NH4F with a mass fraction of 1wt%, and record it as LNMA-1 to obtain an intermediate mixture.

[0121] (3) Disperse the intermediate mixture in an appropriate amount of N-methyl-2-pyrrolidone (NMP), and then sonicate and magnetically stir to ensure uniform dispersion to obtain a dispersed mixture.

[0122] (4) After centrifuging the dispersion mixture at high speed for 5-10 minutes, the adsorption uniformity of ammonium fluoride on the material surface is further improved by oscillation treatment.

[0123] (5) The shaken dispersion mixture was dried overnight at 80-100°C. After thorough grinding, it was transferred to an alumina crucible and calcined in a muffle furnace at 350°C for about 5 hours. Finally, a fluorinated modified cobalt-free lithium-rich manganese-based cathode material was obtained.

[0124] Example 3

[0125] (1) Mixed Al-doped nickel manganese hydroxide precursor Ni x Mn y Al z (OH)₂ and lithium hydroxide monohydrate LiOH·H₂O, after calcination, yield lithium-rich manganese-based basic material Li. a Ni b Mn c Al d O2.

[0126] First, weigh out a certain amount of Ni x Mn y Al z Weigh out the appropriate mass of LiOH·H2O according to the Li / M (M = Ni + Mn + Al) molar ratio of 1.45:1. Add Ni... x Mn y Al z (OH)₂, LiOH·H₂O, and an appropriate amount of ethanol were ball-milled together in a ball mill jar for 7 hours to obtain a slurry. The slurry was then dried overnight at 80°C to obtain a dried solid powder. The dried solid powder was thoroughly ground in an agate mortar and then transferred to an alumina crucible, followed by calcination in a muffle furnace using the following three steps:

[0127] (i) Slow-cook to 500°C and hold for 5 hours. This process involves the initial phase formation of the material.

[0128] (ii) Quickly heat to 700°C and hold for 5 hours. This process is the process of lithium ions entering the crystal lattice.

[0129] (iii) Then quickly heat to 900°C and hold for 6 hours. This process can be repeated two or more times. This process is the complete phase formation process of the material.

[0130] A lithium-rich manganese-based base material, denoted as LNMA powder, was obtained as the initial mixture.

[0131] The molar ratios of the elements in the initial mixture satisfy the following:

[0132] a: 1.19;

[0133] b: 0.20;

[0134] c: 0.58;

[0135] d: 0.02.

[0136] (2) Weigh a small amount of the LNMA powder prepared above and mix it with NH4F with a mass fraction of 5wt%, and record it as LNMA-5 to obtain an intermediate mixture.

[0137] (3) Disperse the intermediate mixture in an appropriate amount of N-methyl-2-pyrrolidone (NMP), and then sonicate and magnetically stir to ensure uniform dispersion to obtain a dispersed mixture.

[0138] (4) After centrifuging the dispersion mixture at high speed for 5-10 minutes, the adsorption uniformity of ammonium fluoride on the material surface is further improved by oscillation treatment.

[0139] (5) The shaken dispersion mixture was dried overnight at 80-100°C. After thorough grinding, it was transferred to an alumina crucible and calcined in a muffle furnace at 400°C for about 5 hours. Finally, a fluorinated modified cobalt-free lithium-rich manganese-based cathode material was obtained.

[0140] Example 4

[0141] (1) Mixed Al-doped nickel manganese hydroxide precursor Ni x Mn y Al z (OH)₂ and lithium hydroxide monohydrate LiOH·H₂O were calcined to obtain an initial mixture Li. a Ni b Mn c Al d O2.

[0142] First, weigh out a certain amount of Ni x Mn y Al z Weigh out the appropriate mass of LiOH·H2O according to the Li / M (M = Ni + Mn + Al) molar ratio of 1.4:1. Add Ni... x Mn y Al z (OH)₂, LiOH·H₂O, and an appropriate amount of ethanol were ball-milled together in a ball mill jar for 8 hours to obtain a slurry. The slurry was then dried overnight at 100°C to obtain a dried solid powder. The dried solid powder was thoroughly ground in an agate mortar and then transferred to an alumina crucible, followed by calcination in a muffle furnace according to the following three-step procedure:

[0143] (i) Slow-cook to 500°C and hold for 5 hours. This process involves the initial phase formation of the material.

[0144] (ii) Quickly heat to 700°C and hold for 5 hours. This process is the process of lithium ions entering the crystal lattice.

[0145] (iii) Then quickly heat to 900°C and hold for 6 hours. This process can be repeated two or more times. This process is the complete phase formation process of the material.

[0146] A lithium-rich manganese-based base material, denoted as LNMA powder, was obtained as the initial mixture.

[0147] The molar ratios of the elements in the initial mixture satisfy the following:

[0148] a: 1.15;

[0149] b: 0.21;

[0150] c: 0.57;

[0151] d: 0.02.

[0152] (2) Weigh a small amount of the LNMA powder prepared above and mix it with NH4F with a mass fraction of 3wt% to obtain an intermediate mixture.

[0153] (3) Disperse the intermediate mixture in an appropriate amount of N-methyl-2-pyrrolidone (NMP), and then sonicate and magnetically stir to ensure uniform dispersion to obtain a dispersed mixture.

[0154] (4) After centrifuging the dispersion mixture at high speed for 5-10 minutes, the adsorption uniformity of ammonium fluoride on the material surface is further improved by oscillation treatment.

[0155] (5) The shaken dispersion mixture was dried overnight at 80-100°C. After thorough grinding, it was transferred to an alumina crucible and calcined in a muffle furnace at 450°C for about 5 hours. Finally, a fluorinated modified cobalt-free lithium-rich manganese-based cathode material was obtained.

[0156] Example 5

[0157] (1) Mixed Al-doped nickel manganese hydroxide precursor Ni x Mn y Al z (OH)₂ and lithium hydroxide monohydrate LiOH·H₂O were calcined to obtain an initial mixture Li. a Ni b Mn c Al d O2.

[0158] First, weigh out a certain amount of Ni x Mn y Al z Weigh out the appropriate mass of LiOH·H2O according to the Li / M (M = Ni + Mn + Al) molar ratio of 1.5:1. Add Ni... x Mn y Al z (OH)₂, LiOH·H₂O, and an appropriate amount of ethanol were ball-milled together in a ball mill jar for 8 hours to obtain a slurry. The slurry was then dried overnight at 80°C to obtain a dried solid powder. The dried solid powder was thoroughly ground in an agate mortar and then transferred to an alumina crucible. Finally, it was calcined in a muffle furnace according to the following three-step procedure:

[0159] (i) Slow-cook to 450°C and hold for 5 hours. This process involves the initial phase formation of the material.

[0160] (ii) Quickly heat to 700°C and hold for 5 hours. This process is the process of lithium ions entering the crystal lattice.

[0161] (iii) Then quickly heat to 900°C and hold for 6 hours. This process can be repeated two or more times. This process is the complete phase formation process of the material.

[0162] A lithium-rich manganese-based base material, denoted as LNMA powder, was obtained as the initial mixture.

[0163] The molar ratios of the elements in the initial mixture satisfy the following:

[0164] a: 1.23;

[0165] b: 0.18;

[0166] c: 0.60;

[0167] d: 0.02.

[0168] (2) Weigh a small amount of the LNMA powder prepared above and mix it with NH4F with a mass fraction of 1wt% to obtain an intermediate mixture.

[0169] (3) Disperse the intermediate mixture in an appropriate amount of N-methyl-2-pyrrolidone (NMP), and then sonicate and magnetically stir to ensure uniform dispersion to obtain a dispersed mixture.

[0170] (4) After centrifuging the dispersion mixture at high speed for 5-10 minutes, the adsorption uniformity of ammonium fluoride on the material surface is further improved by oscillation treatment.

[0171] (5) The shaken dispersion mixture was dried overnight at 80-100°C. After thorough grinding, it was transferred to an alumina crucible and calcined in a muffle furnace at 400°C for about 5 hours. Finally, a fluorinated modified cobalt-free lithium-rich manganese-based cathode material was obtained.

[0172] This application breaks through the traditional design paradigm of interface engineering. By constructing an interface layer that is directionally controlled for dynamics, it directly compensates for the inherent defects of Cf-LLOs, providing important theoretical basis and structural guiding principles for the design of high-energy-density cobalt-free cathode materials.

[0173] To verify the technical effects of this application, the following verification was performed on Embodiment 1 of this application:

[0174] like Figure 2 As shown, three atomic models were constructed: the initial material LNMA ( Figure 2 a) Fluorine combines with transition metal ions (LNMA-TM-F, Figure 2 (b) and fluorine-substituted oxygen LNMA_Fluorine (LNMA-F(O), Figure 2 (c) The electronic density of states diagrams of the O 2p orbitals of the O atom and the TM 3d orbitals of the TM atom in these three atomic models are shown below. Figure 2 As shown. From Figure 2 As can be seen, the contribution of the original LNMA decreased to 78.10% and 77.22% after fluorination, while the contribution of the TM 3d state increased, indicating that fluorine modification enhanced the redox activity of cations and relatively weakened the redox activity of anions. This moderate suppression of anion redox helps to improve the structural stability of the material while maintaining high electrochemical performance. Meanwhile, the calculated band gap decreased from 0.32 eV of the original LNMA to 0.20 eV and 0.28 eV after fluorination, indicating enhanced electronic conductivity. The above verification illustrates the effect of fluorine introduction on the atomic and electronic structure of Cf-LLOs.

[0175] like Figure 3 As shown, Figure 3 In the image, 'a' is a transmission electron microscope image obtained using LNMA, which shows the overall morphology of a particle. Figure 3 In the image, b represents the image obtained using high-resolution mode of transmission electron microscopy, showing the measurement of the interplanar spacing of the bulk phase. For example... Figure 4 As shown, Figure 4 In the image, 'a' is a transmission electron microscope image of LNMA-3, showing the overall morphology of a single particle. Figure 4 Image b in the figure is an image obtained using the high-resolution mode of transmission electron microscopy, in which the bulk phase and near-surface interplanar spacing were measured. Figure 4 In the image, cd represents the Fourier transform of the corresponding region. Figure 4 In the diagram, 'e' represents the energy spectrum of LNMA-3, demonstrating the uniform distribution of all elements. From... Figure 3 and Figure 4 It can be seen that the interplanar spacing of LNMA-3 is slightly increased compared to LNMA, which is mainly attributed to the surface oxygen being covered by F. - Partial substitution modulates the TM–O bonding environment and weakens interlayer electrostatic interactions, inducing slight expansion along the c-axis and increasing the spacing between the Li2MnO3(003) crystal planes in LNMA-3. In the near-surface region, a spinel phase with a thickness of about 5 nm and a (311) crystal plane spacing of 0.24 nm can be observed.

[0176] like Figure 5 The image shows a schematic diagram of the energy dispersive spectroscopy (EDS) spot scanning analysis results of the fluorinated, cobalt-free, lithium-rich manganese-based cathode material LNMA-3 obtained in Example 1 under high-angle annular dark-field scanning transmission electron microscopy. Positions 1–4 were selected in the surface nanoparticle region, and positions 5 and 6 were selected in the surface matrix region. The results show that the surface particles are rich in manganese (Mn) but no fluorine (F) was detected, indicating that these particles are most likely spinel phase. Table 1 below shows the relative contents of fluorine and manganese in the six microregions 1–6.

[0177] Table 1. Relative contents of fluorine and manganese in six microregions

[0178]

[0179] like Figure 6 The diagram shows the physical characterization of LNMA and LNMA-x (x=1, 3, 5). Figure 6 In the diagram, 'a' represents the results of X-ray diffraction analysis of the crystal structure and phase composition of LNMA, LNMA-1, LNMA-3, and LNMA-5. From... Figure 6As shown in Figure a, the diffraction peaks at approximately 18° (003) and 45° (104), and the superlattice reflection peak at approximately 21° indicate that all samples (LNMA, LNMA-1, LNMA-3, and LNMA-5) are composed of two phases: LiMO2 (R–3m) and Li2MnO3 (C2 / m). The clearly split (006) / (102) and (108) / (110) peaks further demonstrate that the samples have a good layered ordered structure. The intensity ratio of the (003) / (104) peak is often used to evaluate the degree of Li / Ni cation mixing. After fluorination, this ratio increases significantly, with LNMA-3 showing the lowest degree of Li / Ni mixing. The overall shift of the (003) and (104) diffraction peaks to lower angles further confirms that the increased lithium interlayer spacing is beneficial to Li + Diffusion and transmission. Figure 6 Figure 'b' in the diagram represents the Rietveld refinement results based on the solid solution model. The similar lattice parameters of all samples indicate that NH4F treatment did not disrupt the intrinsic layered crystal framework of LNMA. With increasing NH4F dosage, both the a and c lattice parameters showed a slight increasing trend, while the c / a ratio gradually increased, further demonstrating that moderate fluorination can effectively expand the interlayer spacing and improve the layered order, thus providing a suitable environment for Li... + Migration provides a more favorable diffusion path. Figure 6 c in the figure is a schematic diagram of the Raman spectrum results, 380 cm⁻¹ - ¹ and 420 cm - The peak at ¹ corresponds to the symmetrical stretching vibration of monoclinic C2 / m phase Li2MnO3, while the peak at 480 cm⁻¹ corresponds to the symmetrical stretching vibration of monoclinic C2 / m phase Li2MnO3. - ¹ and 600 cm - The peaks at ¹ are attributed to the Eg (symmetric bending) and A1g (symmetric stretching) vibrational modes of the rhombohedral R–3m phase LiMO2, respectively. With increasing fluorine content, the Eg vibrational peak of the R–3m phase in LNMA-x (x = 1, 3, 5) exhibits a significant redshift, indicating stronger metal-fluorine (M–F) bond formation. Furthermore, at approximately 625 cm⁻¹... - The weak peak at ¹ can be attributed to the stretching vibration mode of the spinel phase, and its intensity increases with the degree of coating, further confirming the formation of the surface spinel phase. Figure 6 The diagram shows the surface chemical composition and valence state information of the samples obtained from X-ray photoelectron spectroscopy analysis of LNMA and LNMA-x (x=1, 3, 5). The intensity of the F 1s peak gradually increases with increasing fluorine content. The average oxidation state (AOS) of Mn was estimated using Mn 3s level splitting. The results show that the average valence state of Mn decreases with increasing NH4F content, indicating that Mn... 4+ Partially reduced to Mn³ +This leads to a decrease in the proportion of the Li2MnO3 phase and an increase in the proportion of the LiMO2 phase. The Ni 2p spectrum shows Ni³... + The increased fluorine content is consistent with the growth trend of the LiMO2 phase. The O 1s spectrum shows that with the increase of fluorine content, the oxygen vacancy ratio decreases while the lattice oxygen ratio increases, which is attributed to the partial replacement of surface oxygen by fluorine, thereby improving the structural stability of the lithium-rich layered oxide. The F 1s spectrum can be decomposed into two peaks corresponding to Li–F (low binding energy) and M–F (high binding energy), confirming that a LiF coating layer and metal–fluorine bonds are formed simultaneously on the surface of the fluorinated material.

[0180] Figure 7 The initial material LNM (an Al-free lithium-rich manganese-based base material) and the fluorinated modified material LNM-3 (where 3 represents the mass percentage of NH4F during modification) were assembled into coin cells at 2.0–4.7 V (vs. Li / Li). + The initial charge-discharge curves at 0.1 C within the voltage range are shown. The initial discharge specific capacity of the undoped Al-based LNM material is only about 270 mAh g⁻¹. -1 The initial discharge specific capacity of the fluorinated material LNM-3 is only about 285 mAh g. -1 .

[0181] To evaluate the electrochemical performance of the modified lithium-rich material LNMA, electrochemical tests were conducted at 2.0–4.7 V (vs. Li / Li). + Electrochemical tests were conducted on coin cells assembled from LNMA and LNMA-x (x = 1, 3, 5) materials within the voltage range. Figure 8 The figure shown is a graph of the electrochemical characterization test results of LNMA and LNMA-x (x=1, 3, 5). Figure 8 'a' in the figure shows all samples at 0.1 C (1C = 250 mA g). - The first charge-discharge curves under (¹) conditions. The first discharge specific capacity of LNMA is 278.32 mAh g. - ¹, the coulombic efficiency was only 77.79%, indicating severe interfacial side reactions and poor reversibility of oxygen redox. In contrast, the modified samples (LNMA-x) showed significantly improved performance, with LNMA-1, LNMA-3, and LNMA-5 exhibiting initial discharge capacity and initial coulombic efficiency (ICE) of 291.25 mAh g⁻¹. - ¹ / 86.56%, 310.11 mAh g - ¹ / 87.73% and 304.34 mAh g -¹ / 89.38%. An initial efficiency exceeding 85% indicates that surface fluorination effectively suppresses side reactions and improves the reversibility of oxygen redox. However, the capacity of LNMA-5 is slightly lower than that of LNMA-3, which, upon analysis, is attributed to the excessively thick surface coating reducing surface activity to some extent. The capacity surge near approximately 2.8 V is primarily due to the contribution of the surface spinel phase, a feature that becomes increasingly pronounced with increasing coating thickness, suggesting that the spinel phase provides additional capacity. Figure 7 The initial discharge specific capacity of the Al-doped initial material LNMA is approximately 10 mAh g higher than that of the undoped initial material LNM. -1 This demonstrates the successful incorporation of Al, and that the combination with oxygen enhances the reversibility of O. Furthermore, the incorporation of Al increases the content of the Li2MnO3 phase, elongating the charging platform. The fluorinated Al-doped material LNMA-x (1, 3, 5) has a much higher discharge specific capacity than the fluorinated undoped material LNM-3. Figure 8 Figure b shows the rate performance test results, with 5 cycles at 0.1C, 0.5C, 1C, and 2C. The average discharge specific capacity of LNMA at each rate is 277.01, 225.16, 201.24, and 174.57 mAh g, respectively. - ¹, while LNMA-3 reached 303.37, 258.49, 239.89 and 215.36 mAh g, respectively. - ¹. The superior rate performance can be attributed to the increased interlayer spacing and the introduction of the spinel phase, both of which synergistically accelerate the growth of Li. + Diffusion kinetics. Cycling performance at 0.5 C and 1 C is shown in Figures 7c and 7d, respectively. After 100 cycles at 0.5 C, the capacity retention of LNMA and LNMA-3 was 86.47% and 87.54%, respectively. After 150 cycles at 1 C, the capacity retention of LNMA and LNMA-3 was 81.25% and 83.42%, respectively.

[0182] This application achieves comprehensive modification of cobalt-free lithium-rich layered oxides (Cf-LLOs) through the synergistic effect of bulk Al doping and surface fluorine modification. Compared with existing single modification schemes, the overall technical effect is more advantageous and not limited to the individual effects of each step. From the perspective of structural stability, the combination of bulk Al doping and partial bulk F doping significantly enhances the stability of the TM–O bond, effectively mitigating the crystal structure transformation during charge and discharge, while suppressing Ni²⁺ degradation. +The migration of LiF significantly reduces Li / Ni mixing, clears lithium-ion diffusion channels, and fundamentally reduces material performance degradation. From an interfacial performance perspective, the surface LiF buffer layer formed during calcination effectively optimizes the interfacial contact between the material and the electrolyte, inhibits irreversible oxygen release and interfacial side reactions, and reduces manganese dissolution, further improving the material's cycle stability. From an electrochemical performance perspective, synergistic modification achieves a dual improvement in high reversible capacity and excellent rate performance. It retains the high energy density potential of Cf-LLOs while, through structural optimization and interfacial regulation, making the material's reversible capacity less prone to degradation and significantly improving rate performance, thus meeting the demands of high-energy-density, high-power batteries in consumer electronics, electric vehicles, and energy storage systems.

[0183] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a modified cobalt-free lithium-rich manganese-based cathode material, characterized in that, include: Mixed Al-doped nickel manganese hydroxide precursor Ni x Mn y Al z (OH)₂ and LiOH·H₂O: For Ni x Mn y Al z (OH)₂ and LiOH·H₂O are ball-milled and mixed in a solvent to obtain a slurry; the Ni x Mn y Al z When (OH)2 and LiOH·H2O are ball-milled in a solvent, the molar ratio of Li to M is (1.4-1.5):1; where M = Ni + Mn + Al; The slurry is dried to obtain a dried solid powder; The dried solid powder is ground to obtain abrasive material; The abrasive is subjected to three-stage calcination to achieve complete phase formation, yielding a lithium-rich manganese-based base material; in the three-stage calcination, the calcination temperature increases sequentially in each stage; the three-stage calcination method includes: First stage: Slowly heat to 400-500℃ and keep warm; Second stage: Quickly heat to 700℃ and keep warm; Third stage: Quickly heat to 800-900℃ and keep warm; The holding temperature after the first and second stages of calcination is 4-6 h, and the holding time after the third stage of calcination is 8-12 h. After calcination, lithium-rich manganese-based basic material Li was obtained. a Ni b Mn c Al d O2, the Ni x Mn y Al z In (OH)₂, the molar ratios x, y, and z of the elements satisfy: x：0.2-0.5； y：0.5-0.8； z：0.01-0.08； Li a Ni b Mn c Al d In O2, the molar ratios of the elements a, b, c, and d satisfy: a：1.10-1.25； b：0.15-0.45； c：0.50-0.70； d：0.01-0.05； A lithium-rich manganese-based base material was mixed with NH4F to obtain an intermediate mixture; the mass fraction of NH4F in the intermediate mixture was 1 wt%-5 wt%. The intermediate mixture was dispersed in N-methyl-2-pyrrolidone to obtain a dispersion mixture; A solid fraction is obtained from the dispersion mixture, and then the solid fraction is calcined to obtain a fluorinated, cobalt-free, lithium-rich manganese-based cathode material; the calcination temperature of the solid fraction is 300℃-500℃.

2. The method for preparing a modified cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, The lithium-rich manganese-based base material Li a Ni b Mn c Al d In O2, the molar ratios of the elements a, b, c, and d satisfy: a：1.16； b：0.20； c：0.59； d：0.02。 3. The method for preparing a modified cobalt-free lithium-rich manganese-based cathode material according to claim 1, characterized in that, The method for obtaining the solid portion from the dispersion mixture includes: centrifuging the dispersion mixture at high speed and then drying it to obtain the solid portion.

4. A modified cobalt-free lithium-rich manganese-based cathode material, characterized in that, The modified cobalt-free lithium-rich manganese-based cathode material was prepared using any one of the preparation methods described in claims 1 to 3.

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