A method for preparing high-disorder layered lithium cobalt oxide positive electrode material by thermal ion exchange, the material and application thereof

Abstract

The application provides a method for preparing a high-disorder layered lithium cobaltate positive material by thermal ion exchange, the material and application thereof, and comprises the following steps: taking cobaltic tetroxide particles as a cobalt source, grinding and mixing the cobaltic tetroxide particles with sodium carbonate and nano-magnesium oxide, pre-burning at a lower temperature to complete carbonate decomposition and solid-phase diffusion, and then sintering at a medium-high temperature for a long time to obtain a layered sodium cobaltate precursor; then mixing the precursor with a lithium nitrate / lithium chloride molten salt system, carrying out a thermal ion exchange reaction at 200-320 DEG C, washing and desalting by using deionized water, and drying to obtain a layered lithium cobaltate powder with a high interlayer stacking disorder degree. The material has regular and uniform primary particles, and the particle size is mainly 1-10 microns; the material exhibits excellent cycle stability and rate performance in a voltage window of 3.0-4.6 V, improves the structural stability and kinetic performance under high-voltage working conditions, and is suitable for large-scale preparation.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, and more specifically, it relates to a method, materials and applications for preparing highly disordered layered lithium cobalt oxide cathode materials by thermal ion exchange. Background Technology

[0002] Lithium cobalt oxide (LiCoO2) is widely used in consumer electronics and some high-energy-density systems due to its high compaction density and mature processing. However, under high-voltage charge-discharge or high-rate conditions, traditional layered LiCoO2 is prone to structural evolution and interfacial side reactions, resulting in capacity decay, increased impedance, and restricted kinetics. In recent years, ion exchange routes have been considered an effective means to improve the high-voltage stability and kinetic performance of LiCoO2 by reconstructing the layered structure and controlling the degree of disorder under relatively mild conditions. However, existing ion-exchange lithium cobalt oxide still faces problems such as difficulty in improving the degree of ion exchange, difficulty in balancing disorder and structural stability, and insufficient process repeatability and scale-up consistency. Therefore, there is an urgent need for a simple, scalable method for preparing lithium cobalt oxide cathode materials that can stably obtain highly disordered layered structures while balancing cycle stability and high-rate performance. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method, material, and application for preparing highly disordered layered lithium cobalt oxide cathode materials via thermal ion exchange. This addresses the technical issues in existing lithium cobalt oxide cathode material preparation methods, such as difficulty in improving ion exchange levels, difficulty in balancing disorder and structural stability, and insufficient process repeatability and scale-up consistency.

[0004] The purpose and effects of this invention, which describes a method for preparing highly disordered layered lithium cobalt oxide cathode material via thermal ion exchange, the material itself, and its applications, are achieved through the following specific technical means: A method for preparing highly disordered layered lithium cobalt oxide cathode material via thermal ion exchange, wherein the cathode material is a layered lithium cobalt oxide with the following chemical composition: Where 0.001≤x≤0.050; the material has interlayer stacking disorder characteristics, and its XRD shows peak broadening / peak intensity variation on the basis of layered main peak to characterize the increase in disorder; the primary particles of the material have a regular polyhedral morphology and an average particle size of 1~10μm.

[0005] In a preferred embodiment, the average particle size is preferably 3 to 8 μm.

[0006] In a preferred embodiment, the capacity retention rate of the positive electrode material after cycling 300 times at a 1C rate within a voltage window of 3.0 to 4.6V is not less than 85%.

[0007] A method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange includes the following steps: S1: Precursor for solid-phase synthesis of sodium cobaltate; Weigh out Co3O4 particles and Na2CO3 powder, and mix them according to the molar ratio of Na to Co of 1.00 to 1.20. Add nano MgO powder as a dopant source, with the amount of MgO being 0.1 to 5 mol% of the molar amount of Co. Grind and mix the above raw materials evenly. S2: Sintering; The mixture obtained in step S1 is placed in a muffle furnace or tube furnace for pre-calcination, and the temperature is increased to 450-600℃ at a rate of 1-10℃ / min and held for 2-10 hours. Then, high-temperature sintering is carried out by heating to 750-900℃ at a rate of 1-10℃ / min and holding for 50-150h. After cooling, layered sodium cobaltate precursor powder is obtained. S3: Thermo-ion exchange; The layered sodium cobaltate precursor powder obtained in step S2 is mixed with lithium salt and then subjected to thermal ion exchange. The lithium salt is a mixed salt of LiNO3 and LiCl, and the molar ratio of LiNO3 to LiCl is 70:30 to 95:5. The molar ratio of Li ions to Na ions in the mixture is 1 to 20:1. The mixture is heated to 200 to 320°C at a rate of 2 to 10°C / min and held at this temperature for 1 to 12 hours to complete the ion exchange. S4: Washing and drying; The powder after the reaction in step S3 was washed with deionized water until there was no obvious nitrate / chloride ion residue in the filtrate, and then dried at 60-120℃ to obtain a highly disordered layered lithium cobalt oxide cathode material.

[0008] In a preferred embodiment, in step S2, the pre-firing temperature is 500°C and the holding time is 4 hours; the high-temperature sintering temperature is 800°C and the holding time is 80-120 hours.

[0009] In a preferred embodiment, in step S3, the molar ratio of LiNO3:LiCl is 88:12, the molar ratio of Li ions to Na ions is 5:1, the exchange temperature is 260°C, and the holding time is 4 hours.

[0010] In a preferred embodiment, in step S1, the excess coefficient of Na2CO3 relative to stoichiometry is 1.05 ± 0.05.

[0011] In a preferred embodiment, the amount of MgO added is 1 mol.

[0012] A lithium-ion battery positive electrode sheet, the positive electrode sheet comprising the highly disordered layered lithium cobalt oxide positive electrode material according to any one of claims 1 to 3, a conductive agent and a binder; wherein the mass ratio of the highly disordered layered lithium cobalt oxide positive electrode active material: conductive agent: binder is (7-9):(0.5-1.5):(0.5-1.5).

[0013] Application of highly disordered layered lithium cobalt oxide cathode material in lithium-ion batteries: Highly disordered layered lithium cobalt oxide cathode material is used as a cathode active material in lithium-ion batteries.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The overall process route of solid-state synthesis of sodium cobalt oxide precursor combined with low-temperature thermal ion exchange is adopted. The raw materials used are all inorganic salts and metal oxides commonly used in industrial production. No special or expensive raw materials are required. The preparation process is short and has no complicated special steps. The target material can be obtained simply through solid-state sintering and low-temperature heat exchange. The process parameters of each step have a wide range and are easy to control, which can improve the repeatability of the process and the consistency of products between different production batches. It is suitable for the requirements of large-scale industrial production and avoids the problems of high scale-up difficulty and significant performance fluctuations between different batches of products in the traditional ion-exchange lithium cobalt oxide preparation process.

[0015] 2. By synergistically regulating Mg doping with the LiNO3 / LiCl molten salt system, a high degree of Na / Li exchange can be achieved at a relatively low thermal ion exchange temperature. Simultaneously, under the regulatory effect of magnesium, a controllable interlayer stacking disorder structure is induced, enabling precise control of the degree of disorder. This approach not only improves the lithium-ion transport kinetics within the material but also enhances its structural and interfacial stability, resolving the technical contradiction of simultaneously achieving improved disorder and maintained structural stability in traditional ion-exchange lithium cobalt oxide materials.

[0016] 3. The prepared highly disordered layered lithium cobalt oxide cathode material exhibits a regular polyhedral morphology and uniform particle size distribution in its primary particles. Under high-voltage charge-discharge conditions, it can suppress harmful structural phase transitions and electrode interface side reactions. Simultaneously, the disordered stacking structure between layers provides more lithium-ion transport channels, enabling the material to possess both excellent long-cycle stability and high-rate discharge capability. This makes it suitable for high-power, high-voltage lithium-ion battery applications, meeting the demands of high-power, high-energy-density lithium-ion battery applications and expanding the practical application range of lithium cobalt oxide cathode materials. Attached Figure Description

[0017] Figure 1 This is the XRD pattern of the highly disordered layered lithium cobalt oxide cathode material in this invention; Figure 2 This is a SEM image of the highly disordered layered lithium cobalt oxide cathode material in this invention; Figure 3 This is the cycle performance curve of the highly disordered layered lithium cobalt oxide cathode material of this invention in a lithium-ion battery; Figure 4 This is the rate performance curve of the highly disordered layered lithium cobalt oxide cathode material of this invention in lithium-ion batteries; Figure 5 This is a flowchart of the steps of a method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange according to the present invention. Detailed Implementation

[0018] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the technical solutions of the present invention, but should not be used to limit the scope of protection of the present invention.

[0019] Example 1:

[0020] As attached Figures 1 to 4 As shown: This invention provides a method for preparing highly disordered layered lithium cobalt oxide cathode materials via thermal ion exchange. The cathode material is a layered lithium cobalt oxide with the following chemical composition: Where 0.001≤x≤0.050; magnesium is uniformly doped into the lattice structure of lithium cobalt oxide, replacing some of the cobalt atoms and stabilizing the layered main framework. It also unifies the layer slip pattern and improves the interlayer distance. The material exhibits disordered interlayer stacking, and its XRD pattern shows peak broadening or intensity variation based on the layered main peak, characterizing the increased disorder. This disordered interlayer stacking structure breaks the strict interlayer order in traditional lithium cobalt oxide materials, avoiding stress concentration caused by interlayer slip during charging and discharging. The primary particles of the material have a regular polyhedral morphology with an average particle size of 1–10 μm. The regular polyhedral morphology can improve the compaction density of the material, and the uniform particle size distribution can ensure the dispersion and coating consistency of the slurry during electrode preparation, reducing the porosity difference within the electrode. This results in a highly disordered layered lithium cobalt oxide cathode material. The primary particles exhibit a regular polyhedral morphology and uniform particle size distribution. Under high-voltage charge and discharge conditions, they can suppress harmful structural phase transitions and electrode interface side reactions, reduce the dissolution of active materials and the increase in interfacial impedance during charge and discharge. At the same time, the disordered stacking structure between layers provides more transport channels for lithium ions, shortens the diffusion distance of lithium ions, and reduces the migration resistance of lithium ions inside the material. This gives the material both good long-cycle stability and high-rate discharge capability. This material, as a positive electrode active material, is mixed with conductive agents and binders in a certain proportion to form a slurry, which is then coated on the surface of aluminum foil current collectors. After drying, rolling, and stamping, it is made into a lithium-ion battery positive electrode sheet, suitable for high-power, high-voltage lithium-ion battery applications. It can meet the usage requirements of lithium-ion batteries in high-power, high-energy-density application scenarios and expand the practical application range of lithium cobalt oxide positive electrode materials.

[0021] The average particle size of the highly disordered layered lithium cobalt oxide cathode material is preferably 3–8 μm. This particle size range can balance the material's compaction density and lithium-ion transport performance. Too small a particle size will result in an excessively large specific surface area, increasing the probability of side reactions at the electrode interface. Too large a particle size will prolong the diffusion distance of lithium ions within the particles, reducing the material's rate performance. Materials within this particle size range can achieve high compaction density during electrode rolling while ensuring a uniform pore structure within the electrode, which is beneficial for electrolyte wetting and lithium-ion transport, thus improving the overall electrochemical performance of the electrode. The capacity retention rate of the cathode material after 300 cycles at 1C within a voltage window of 3.0–4.6V is not less than 8%. The 5% voltage window covers the commonly used charge and discharge range of lithium-ion batteries in current consumer electronics. The 1C rate corresponds to the battery's conventional charge and discharge rate, and 300 cycles correspond to the typical usage cycle of consumer electronics products. This capacity retention rate ensures that the battery maintains a stable discharge capacity during long-term use, reducing the problem of reduced battery life due to capacity decay. At the same time, the stable cycle performance under high voltage can be adapted to battery systems with higher energy density, meeting the dual requirements of portable electronic devices for long battery life and high power output. When the positive electrode sheet made of this material is assembled into a lithium-ion battery, it can maintain a stable structure and performance under high-voltage charge and discharge conditions, extending the overall lifespan of the battery.

[0022] Please see as follows Figure 5 As shown, the present invention also provides a method for preparing highly disordered layered lithium cobalt oxide cathode materials by thermal ion exchange, comprising the following steps: S1: Precursor for solid-phase synthesis of sodium cobaltate; Weigh out Co3O4 particles and Na2CO3 powder, and prepare the mixture according to a Na to Co molar ratio of 1.00–1.20. Add nano-MgO powder as a dopant source, with the amount of MgO being 0.1–5 mol% of the molar amount of Co. Grind and mix the above raw materials evenly. Specifically, solid-phase synthesis of sodium cobaltate precursor provides a structurally stable layered precursor for subsequent thermal ion exchange reactions, and is a fundamental step in preparing highly disordered layered lithium cobaltate cathode materials. Co3O4 particles and Na2CO3 powder are weighed and mixed at a Na to Co molar ratio of 1.00–1.20. This molar ratio range ensures that the cobalt source reacts fully to form the layered sodium cobaltate phase, avoiding unreacted cobalt oxide residues that could affect subsequent ion exchange efficiency. Nano-MgO powder is added as a dopant source, with the MgO amount being 0.1–5 mol% of the Co molar amount. The nano-MgO powder is uniformly dispersed in the raw material mixture, facilitating subsequent sintering. The sodium cobalt oxide lattice provides a basis for the disordered control of interlayer stacking in the final lithium cobalt oxide material. The above raw materials are placed in a ball mill or mortar and ground and mixed evenly to ensure that the raw material particles are in full contact, reduce the activation energy of the subsequent solid-phase reaction, ensure that the reaction process proceeds uniformly, and avoid product performance differences caused by local component inhomogeneity. Specifically, in step S1, the excess coefficient of Na2CO3 relative to the stoichiometry is 1.05±0.05. An appropriate excess of Na2CO3 can compensate for the volatilization loss of sodium element during high-temperature sintering, ensure the accuracy of the stoichiometry of the sodium cobalt oxide precursor, and at the same time promote the full progress of the solid-phase reaction, improve the purity and crystallinity of the precursor.

[0023] S2: Sintering; The mixture obtained in step S1 is placed in a muffle furnace or tube furnace for pre-calcination, and the temperature is increased to 450-600℃ at a rate of 1-10℃ / min and held for 2-10 hours. Then, high-temperature sintering is carried out by heating to 750-900℃ at a rate of 1-10℃ / min and holding for 50-150h. After cooling, layered sodium cobaltate precursor powder is obtained. Specifically, a stepwise sintering process is used to achieve sufficient phase formation, crystallinity control, and particle morphology stability of the sodium cobaltate precursor, providing a structurally complete and uniformly composed layered precursor foundation for the subsequent thermal ion exchange reaction. The mixture obtained in step S1 is placed in a muffle furnace or tube furnace for pre-calcination, with the temperature increased to 450-600℃ at a heating rate of 1-10℃ / min and held for 2-10 hours. The pre-calcination stage allows for the complete decomposition of sodium carbonate and the release of carbon dioxide gas, while promoting the initial solid-phase diffusion between the cobalt and sodium sources, forming the initial crystal nuclei of sodium cobaltate. This avoids material splashing and localized compositional unevenness caused by the rapid decomposition of sodium carbonate at high temperatures. The gradual heating rate ensures a stable decomposition reaction and reduces the porosity differences within the material. Furthermore, the preferred pre-calcination temperature is 500℃ and the holding time is 4 hours. This parameter combination ensures the complete decomposition of sodium carbonate and the formation of an appropriate number of uniformly sized initial crystal nuclei, providing a good foundation for subsequent crystal growth.

[0024] After pre-firing, high-temperature sintering is carried out, with the temperature increased to 750-900℃ at a heating rate of 1-10℃ / min and held for 50-150h. Further, the preferred high-temperature sintering temperature is 800℃ and the holding time is 80-120h. This parameter range allows the sodium cobaltate crystals to grow to a suitable size while maintaining the integrity of the layered structure, avoiding excessive particle growth and sintering agglomeration caused by excessively high temperature or long time, and ensuring that the subsequent thermal ion exchange reaction can be carried out uniformly inside the particles. The high-temperature sintering stage allows the initial crystal nuclei to grow fully, forming a well-crystallized layered sodium cobaltate crystal structure. At the same time, it controls the morphology and size distribution of the particles. Long-term heat preservation ensures that the solid-phase reaction is complete, eliminates unreacted raw material residues, and allows magnesium to be uniformly doped into the sodium cobaltate crystal structure. This provides the preconditions for inducing interlayer stacking disorder during the subsequent ion exchange process. After sintering, the furnace is naturally cooled to room temperature to obtain layered sodium cobaltate precursor powder. Natural cooling avoids the internal stress generated inside the crystal caused by rapid cooling, ensuring the structural stability of the precursor.

[0025] S3: Thermo-ion exchange; The layered sodium cobaltate precursor powder obtained in step S2 was mixed with lithium salt and then subjected to thermal ion exchange. The lithium salt was a mixed salt of LiNO3 and LiCl, with a molar ratio of LiNO3:LiCl of 70:30 to 95:5. The molar ratio of Li ions to Na ions in the mixture was 1 to 20:1. The mixture was heated to 200 to 320°C at a rate of 2 to 10°C / min and held at this temperature for 1 to 12 hours to complete the ion exchange. Specifically, thermal ion exchange is the core process for achieving layered structure reconstruction and disorder control. Through ion substitution reactions in the molten salt system, sodium ions in the sodium cobaltate precursor are replaced with lithium ions, while preserving the layered main structure and inducing interlayer stacking disorder, providing a structural basis for the final material's electrochemical performance. The layered sodium cobaltate precursor powder is mixed with a lithium salt, a mixture of LiNO3 and LiCl, with a LiNO3:LiCl molar ratio of 88:12. This ratio lowers the melting point of the mixed molten salt to a suitable range while maintaining high lithium ion activity. The ion exchange reaction is carried out at a lower temperature, while simultaneously adjusting the ion activity of the molten salt to promote sodium ion extraction and lithium ion insertion, avoiding problems such as excessively high melting points of single lithium salts or excessively slow ion exchange rates. The molar ratio of Li ions to Na ions in the mixture is 5:1, and the excess lithium ions can promote the extraction of sodium ions and the insertion of lithium ions. The forward ion exchange reaction increases the degree of sodium ion replacement and reduces the residue of unexchanged sodium ions. This ensures a high degree of ion exchange while avoiding excessive lithium salt residue that would burden subsequent washing. The mixture is heated to 260°C at a rate of 2–10°C / min and held for 4 hours to complete the ion exchange. This temperature is lower than the sintering temperature of traditional solid-state lithium cobalt oxide preparation, which avoids excessive particle growth and structural sintering. At the same time, it ensures that the molten salt is in a molten state, providing sufficient kinetic conditions for ion migration and enabling full Na / Li exchange. The gradual heating rate allows the molten salt to melt uniformly and come into full contact with the precursor particles, ensuring that the ion exchange reaction proceeds uniformly within the particles. It also induces a suitable degree of interlayer stacking disorder, avoiding the destruction of the layered structure caused by excessively high temperatures or excessive holding times. The holding time controls the degree of ion exchange and the formation of interlayer stacking disorder.

[0026] By synergistically regulating Mg doping and the LiNO3 / LiCl molten salt system, a high degree of Na / Li exchange can be achieved at a relatively low thermal ion exchange temperature. Magnesium pre-doping into the lattice of the sodium cobalt oxide precursor reduces interlayer binding energy, promoting sodium ion extraction and lithium ion insertion. Simultaneously, during ion exchange, magnesium stabilizes the layered main framework, preventing collapse of the layered structure during ion replacement. Furthermore, under the regulatory effect of magnesium, a controllable interlayer stacking disorder structure is induced, achieving controllable disorder. This approach not only improves the lithium-ion transport kinetics within the material—interlayer stacking disorder increases lithium-ion transport channels, shortens the lithium-ion diffusion distance, and reduces lithium-ion migration resistance—but also enhances the material's structural and interfacial stability. Magnesium can suppress interlayer slip and structural phase transitions during charging and discharging, reducing interfacial side reactions. This solves the technical contradiction of simultaneously improving disorder and maintaining structural stability in traditional ion-exchange lithium cobalt oxide materials.

[0027] S4: Washing and drying; The powder after the reaction in step S3 was washed with deionized water until there was no obvious nitrate / chloride ion residue in the filtrate, and then dried at 60-120℃ to obtain a highly disordered layered lithium cobalt oxide cathode material.

[0028] Specifically, washing and drying are crucial steps in removing residual soluble lithium salts and reaction byproducts after the thermal ion exchange reaction. These steps are key to ensuring the stable electrochemical performance of the final cathode material. The powder after step S3 is washed multiple times with deionized water. After each wash, the filtrate is qualitatively tested for nitrate and chloride ions until no obvious nitrate or chloride ions remain in the filtrate. Residual nitrate, chloride ions, and unreacted lithium salts can affect the dispersion and coating quality of the slurry during subsequent electrode preparation. They can also trigger interfacial side reactions during battery charging and discharging, increasing electrode interfacial impedance and accelerating battery capacity decay. Therefore, thorough washing can eliminate these adverse effects and ensure the purity and performance stability of the material. After washing, the powder is placed in a forced-air drying oven or vacuum drying oven and dried at a temperature range of 60–120°C to obtain a highly disordered layered lithium cobalt oxide cathode material. This temperature range can effectively remove adsorbed moisture from the powder surface and pores, preventing the material from absorbing water and deteriorating during storage. At the same time, it will not damage the layered structure and disordered stacking characteristics of the material, ensuring the structural integrity of the material.

[0029] This paper presents a comprehensive process route that combines solid-state synthesis of sodium cobalt oxide precursors with low-temperature thermal ion exchange. The raw materials used are all common inorganic salts and metal oxides found in industrial production, eliminating the need for special or expensive raw materials. This reduces raw material procurement costs and ensures supply chain stability. The preparation process is short and free of complex special steps; the target material can be obtained solely through solid-state sintering and low-temperature heat exchange. This reduces the number of production steps, shortens the production cycle, and lowers energy consumption and labor costs. The process parameters for each step are wide-ranging and easily controllable, eliminating the need for high-precision specialized production equipment. This improves process repeatability and product consistency between different production batches, reducing batch-to-batch performance fluctuations and adapting to the requirements of large-scale industrial production. It avoids the problems of high scale-up difficulty and significant performance fluctuations between different batches inherent in traditional ion-exchange lithium cobalt oxide preparation processes. Furthermore, this process route eliminates the need for toxic and harmful reaction reagents, making the production process more environmentally friendly and meeting industrial environmental protection requirements.

[0030] A method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange is disclosed. The amount of MgO added is 1 mol%. This doping amount can form uniform magnesium atom substitution in the lithium cobalt oxide lattice, which can effectively stabilize the layered host structure, suppress interlayer slip and structural phase transition during charging and discharging, and provide suitable lattice distortion conditions for inducing interlayer stacking disorder during ion exchange. This avoids insufficient structural stabilization caused by too low magnesium doping amount, while preventing the reduction of active sites and specific capacity caused by too high magnesium doping amount.

[0031] A lithium-ion battery positive electrode sheet comprises a highly disordered layered lithium cobalt oxide positive electrode material, a conductive agent, and a binder. The highly disordered layered lithium cobalt oxide positive electrode active material serves as the core electrochemical active component, providing reversible capacity during battery charge and discharge. The conductive agent forms a continuous electron transport network within the positive electrode sheet, reducing the ohmic impedance of the electrode and increasing the electron transport rate. The binder bonds the positive electrode active material particles together with the conductive agent and ensures good bonding between the active material and the aluminum foil current collector, preventing active material detachment during rolling and cycling. The mass ratio of the highly disordered layered lithium cobalt oxide positive electrode active material to the conductive agent to the binder is (7–9):(0.5–1.5):(0.5–1.5). This mass ratio range balances the energy density, electronic conductivity, and mechanical strength of the positive electrode sheet, ensuring that the electrode sheet possesses good electron transport performance and structural stability while having a high active material loading.

[0032] The application of highly disordered layered lithium cobalt oxide cathode material in lithium-ion batteries: Highly disordered layered lithium cobalt oxide cathode material is used as the positive electrode active material in lithium-ion batteries. After the positive electrode sheet made of this material is stacked and packaged with the negative electrode sheet, separator and electrolyte, the electrolyte is injected to assemble a lithium-ion battery. It can maintain stable cycle performance and rate performance under high voltage charge and discharge conditions. It is suitable for multiple fields such as consumer electronics portable devices, high-power energy storage devices and high-energy-density power lithium-ion batteries. It can improve the overall energy density and service life of the battery and meet the diverse performance requirements of lithium-ion batteries in different application scenarios.

[0033] Example 2: Structural and Morphological Characterization The material structure was obtained through XRD testing, such as... Figure 1 As shown, the obtained material exhibits a layered structure and high degree of disorder; the material morphology was characterized by SEM, such as... Figure 2 As shown, the obtained particles are regular and uniform, with the primary particle size mainly around 5 μm.

[0034] Example 3: Electrochemical Performance The obtained positive electrode material, conductive agent, and binder are mixed to form a slurry, which is then coated onto an aluminum foil current collector. After drying, rolling, and stamping, coin cells are assembled and electrochemical tests are performed. Figure 3 As shown, after 300 cycles at a 1C rate within a voltage window of 3.0–4.6V, the capacity retention is approximately 90%; Figure 4 As shown, the material maintains a high reversible capacity within a rate range of 0.2C to 10C, demonstrating excellent kinetic performance.

[0035] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing 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 can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange, characterized in that: The cathode material is a layered lithium cobalt oxide with the following chemical composition: Where 0.001≤x≤0.050; the material has interlayer stacking disorder characteristics, and its XRD shows peak broadening / peak intensity variation on the basis of layered main peak to characterize the increase in disorder; the primary particles of the material have a regular polyhedral morphology and an average particle size of 1~10μm.

2. The method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange according to claim 1, characterized in that: The average particle size is preferably 3 to 8 μm.

3. The method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange according to claim 2, characterized in that: The capacity retention rate of the cathode material after 300 cycles at a 1C rate within a voltage window of 3.0–4.6V is no less than 85%.

4. A method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange according to any one of claims 1-3, characterized in that: It includes the following steps: S1: Precursor for solid-phase synthesis of sodium cobaltate; Weigh out Co3O4 particles and Na2CO3 powder, and mix them according to the molar ratio of Na to Co of 1.00 to 1.

20. Add nano MgO powder as a dopant source, with the amount of MgO being 0.1 to 5 mol% of the molar amount of Co. Grind and mix the above raw materials evenly. S2: Sintering; The mixture obtained in step S1 is placed in a muffle furnace or tube furnace for pre-calcination, and the temperature is increased to 450-600℃ at a rate of 1-10℃ / min and held for 2-10 hours. Then, high-temperature sintering is carried out by heating to 750-900℃ at a rate of 1-10℃ / min and holding for 50-150h. After cooling, layered sodium cobaltate precursor powder is obtained. S3: Thermo-ion exchange; The layered sodium cobaltate precursor powder obtained in step S2 is mixed with lithium salt and then subjected to thermal ion exchange. The lithium salt is a mixed salt of LiNO3 and LiCl, and the molar ratio of LiNO3 to LiCl is 70:30 to 95:

5. The molar ratio of Li ions to Na ions in the mixture is 1 to 20:

1. The mixture is heated to 200 to 320°C at a rate of 2 to 10°C / min and held at this temperature for 1 to 12 hours to complete the ion exchange. S4: Washing and drying; The powder after the reaction in step S3 was washed with deionized water until there was no obvious nitrate / chloride ion residue in the filtrate, and then dried at 60-120℃ to obtain a highly disordered layered lithium cobalt oxide cathode material.

5. The method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange according to claim 4, characterized in that: In step S2, the pre-firing temperature is 500℃ and the holding time is 4h; the high-temperature sintering temperature is 800℃ and the holding time is 80-120h.

6. The method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange according to claim 4, characterized in that: In step S3, the molar ratio of LiNO3:LiCl is 88:12, the molar ratio of Li ions to Na ions is 5:1, the exchange temperature is 260℃, and the holding time is 4h.

7. The method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange according to claim 4, characterized in that: In step S1, the excess coefficient of Na2CO3 relative to the stoichiometry is 1.05 ± 0.

05.

8. The method for preparing highly disordered layered lithium cobalt oxide cathode material by thermal ion exchange according to claim 7, characterized in that: The amount of MgO added was 1 mol.

9. A positive electrode sheet for a lithium-ion battery, characterized in that, The positive electrode sheet comprises the highly disordered layered lithium cobalt oxide positive electrode material according to any one of claims 1 to 3, a conductive agent, and a binder; wherein the mass ratio of the highly disordered layered lithium cobalt oxide positive electrode active material: conductive agent: binder is (7 to 9):(0.5 to 1.5):(0.5 to 1.5).

10. The application of the highly disordered layered lithium cobalt oxide cathode material as described in any one of claims 1 to 3 in lithium-ion batteries, characterized in that, Highly disordered layered lithium cobalt oxide cathode material is used as a cathode active material in lithium-ion batteries.

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