A cerium oxide-coated modified lithium-rich manganese-based positive electrode material, a preparation method, a preparation system and applications

Abstract

The application discloses a cerium oxide coated modified lithium-rich manganese-based positive electrode material, a preparation method, a preparation system and application, and relates to the technical field of lithium ion batteries. The application discloses a cerium oxide coated modified lithium-rich manganese-based positive electrode material, which is characterized by comprising a lithium-rich manganese-based matrix and a cerium oxide layer coated on the surface of the lithium-rich manganese-based matrix. The coated cerium oxide layer fundamentally improves the electrochemical defects of the LRM material, and simultaneously plays a dual role of a physical barrier and an oxygen buffer. 3+ / Ce 4+ The reversible redox pair realizes the stability of oxygen species and inhibits the irreversible conversion of the layered structure of the LRM matrix to a spinel / rock salt phase.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery materials, and relates to a lithium-rich manganese-based cathode material modified by cerium oxide coating, a preparation method, a preparation system and an application. Background Art

[0002] Lithium-rich manganese-based (LRM) cathode materials (such as xLi2MnO3・(1-x) LiMO2, 0 < x < 1, M is a transition metal) have become the core candidate materials for next-generation lithium-ion batteries due to their ultra-high specific capacity (≈250 mAh / g), high energy density (≈800 Wh / kg), cobalt-free, low cost and environmental friendliness. Their high capacity mainly stems from the anion redox reaction at high voltages, which can further enhance the battery energy output.

[0003] Lithium-rich manganese-based (LRM) materials face serious challenges in practical applications: at high voltages, lattice oxygen is easily irreversibly released, accompanied by the dissolution and migration of transition metals (TM), resulting in an irreversible transformation of the crystal structure from a layered phase to a spinel / rock salt phase, ultimately leading to significant capacity decay and voltage decay; meanwhile, the material surface is prone to side reactions with the electrolyte, forming a thick and unstable cathode-electrolyte interface (CEI) film, further deteriorating the electrochemical performance.

[0004] To solve the above problems, researchers have developed strategies such as bulk doping, morphology regulation and surface modification. Among them, surface coating has become the mainstream method due to its simple operation and direct effect. Although existing coating materials (such as Al2O3, TiO2) can isolate the electrolyte and reduce the dissolution of transition metals to a certain extent, they have obvious limitations: Al2O3 cannot inhibit the release of lattice oxygen, and TiO2 will reduce the lithium-ion conduction rate, and both are difficult to fundamentally solve the voltage decay problem.

[0005] Cerium oxide (CeO2), as a rare earth oxide, has excellent high-voltage stability, anti-corrosion oxidation and unique oxygen storage capacity (OSC). Its Ce 3+ / Ce 4+ reversible redox pair can form abundant oxygen vacancies, which can theoretically play both physical barrier and oxygen buffer dual roles. However, existing methods for coating LRM with CeO2 have problems such as uneven coating layer, complex process, high cost or limited performance improvement, which limit its industrial application. Summary of the Invention

[0006] To overcome the performance defects of existing lithium-rich manganese-based (LRM) cathode materials and the shortcomings of existing surface coating technologies, this invention addresses the technical problems of irreversible release of lattice oxygen, dissolution and migration of transition metals, severe voltage and capacity decay during high-voltage cycling of existing LRM materials, as well as the inability of existing coating materials to simultaneously achieve physical isolation and oxygen buffering, uneven coating layers in the coating process, and high difficulty in industrialization. This invention provides a cerium oxide-coated modified lithium-rich manganese-based cathode material, its preparation method, preparation system, and applications.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a cerium oxide-coated modified lithium-rich manganese-based cathode material, comprising a lithium-rich manganese-based matrix, wherein the surface of the lithium-rich manganese-based matrix is ​​coated with a cerium oxide layer, and the lithium-rich manganese-based matrix is ​​a lithium-rich manganese-based compound.

[0008] Furthermore, the thickness of the cerium oxide layer is 3-5 nanometers.

[0009] Furthermore, the cerium oxide layer has Ce 3+ and Ce 4+ .

[0010] A method for preparing a cerium oxide-coated modified lithium-rich manganese-based cathode material includes the following steps: (1) Pretreatment of lithium-rich manganese matrix: Clean and vacuum dry the lithium-rich manganese matrix; (2) Preparation of precursor solution: Prepare an aqueous solution of cerium nitrate (Ce(NO3)3・6H2O), stir until completely dissolved, and obtain cerium oxide precursor solution; (3) Precursor coating: The pretreated lithium-rich manganese matrix is ​​added to the cerium oxide precursor solution in proportion, and after mechanical stirring, it is ultrasonically treated so that the precursor is adsorbed on the surface of the lithium-rich manganese matrix. (4) Separation and drying: The lithium-rich manganese matrix coated in step (3) is collected by vacuum filtration, washed and dried to obtain precursor coated lithium-rich manganese matrix powder; (5) Calcination and forming: The precursor-coated lithium-rich manganese-based matrix powder is placed in a sintering furnace, calcined under a specific atmosphere and naturally cooled to room temperature, so that the precursor is transformed into a cerium oxide coating layer, and cerium oxide-coated lithium-rich manganese-based cathode material is obtained.

[0011] Furthermore, the pretreatment step of the lithium-rich manganese-based matrix is ​​to ultrasonically clean the lithium-rich manganese-based matrix with anhydrous ethanol for 15 minutes to remove surface impurities and disperse slightly agglomerated LRM secondary particles through ultrasonic cavitation effect, and then vacuum dry at 80°C for 12 hours.

[0012] Furthermore, the concentration of the cerium oxide precursor solution is 0.05–0.15 mol / L.

[0013] Furthermore, in the precursor coating step, the pretreated lithium-rich manganese-based matrix powder is added to the cerium oxide precursor solution according to a mass ratio of cerium nitrate to lithium-rich manganese-based matrix of 0.5:100, 1.0:100, 2.0:100, or 5.0:100. In this step, the shear force, dispersion force, and convection of mechanical stirring cause the precursor to be adsorbed on the surface and pores of the lithium-rich manganese-based matrix, forming a preliminary precursor adsorption layer. In this step, the cavitation effect and vibration of ultrasound are used to eliminate the uneven precursor coating caused by mechanical stirring, so that the cerium nitrate precursor is molecularly dispersed on the surface of the lithium-rich manganese-based matrix, forming a continuous and thin precursor adsorption layer.

[0014] Furthermore, in the calcination forming step, the temperature is slowly increased to 400-600℃ at a heating rate of 4-6℃ / min in a calcination atmosphere of air, oxygen or inert gas, and then calcined at this temperature for 4-6 hours. During the calcination process, the cerium nitrate precursor undergoes a complete thermal decomposition reaction and is completely converted into cerium oxide. It then forms a strong interfacial bond on the surface of the LRM matrix through a high-temperature solid-phase reaction, forming a cerium oxide coating layer.

[0015] A method for preparing a cerium oxide-coated modified lithium-rich manganese-based cathode material uses a preparation system comprising a main body of equipment, which includes a reaction vessel, and the reaction vessel integrates a stirring system, an ultrasonic dispersion system, a temperature control system, and auxiliary functional components. The stirring system is connected to the external power mechanism of the container and is used for dissolving and stirring cerium nitrate hexahydrate during the preparation of the precursor solution, as well as for adsorption and stirring after the lithium-rich manganese matrix and the cerium nitrate precursor are mixed, so that the precursor is attached to the surface of the lithium-rich manganese matrix. The ultrasonic dispersion system includes an ultrasonic transducer mounted on the side wall or bottom of the reaction vessel and an ultrasonic power adjustment button on the outside of the vessel. The ultrasonic power is precisely controlled to eliminate uneven coating after stirring, promote uniform dispersion of the precursor on the LRM surface, and form a synergistic effect with the stirring system. The temperature control system includes a heating module wrapped around the outside of the reaction vessel. The heating module is equipped with heating wires inside and a temperature control knob is located on the outside of the vessel. It can achieve precise temperature control within the range of 0-100℃, adapt to the auxiliary dissolution temperature control during the preparation of precursor solution, and maintain the constant temperature environment required throughout the coating process. The auxiliary functional components include a drain outlet at the bottom of the reaction vessel and a power interface on the side wall of the vessel. The drain outlet is used for the discharge of waste liquid after the experiment. The power interface provides unified power supply for the stirring system, ultrasonic dispersion system and temperature control system, ensuring the integrated operation of the equipment.

[0016] The application of the cerium oxide-coated modified lithium-rich manganese-based cathode material in lithium-ion batteries.

[0017] In summary, the advantages of this invention are: The cerium oxide layer of this invention fundamentally improves the electrochemical defects of LRM materials. The cerium oxide layer simultaneously functions as a physical barrier and an oxygen buffer: as a physical barrier, it effectively isolates the LRM substrate from the electrolyte, inhibiting electrolyte decomposition under high voltage and excessive growth of the electrode-electrolyte interface (CEI) film, reducing the dissolution and migration of transition metals; as an oxygen buffer, its abundant oxygen vacancies can rapidly capture lattice oxygen released from the LRM substrate under high voltage, through Ce... 3+ / Ce 4+ Reversible redox reactions stabilize oxygen species and inhibit the irreversible transformation of the layered structure of the LRM matrix into the spinel / rock salt phase, fundamentally solving the core problem of severe capacity and voltage decay in traditional LRM materials.

[0018] The cerium oxide coating of this invention is uniform and dense, balancing protection and lithium-ion conductivity. Through a synergistic process of "mechanical stirring + ultrasonic treatment" combined with the uniform adsorption characteristics of the cerium nitrate precursor, the cerium oxide layer is continuously, densely, and uniformly grown on the LRM substrate surface. The thickness of the cerium oxide layer is precisely controlled within the optimal range of 3-5 nanometers, ensuring effective protection of the LRM substrate without hindering the rapid conduction of lithium ions between the material surface and the bulk phase. This avoids the performance degradation problems caused by uneven coating layers or excessively thick / thin coating layers in existing coating technologies.

[0019] The electrochemical performance of the lithium-rich manganese-based cathode material prepared by this invention is significantly improved, and the cycle stability and voltage retention are greatly enhanced. The optimized cerium oxide-coated LRM material (cerium nitrate to LRM mass ratio 1.0:100) was cycled at 1C rate and within a voltage range of 2.0-4.8V. After 500 cycles, the capacity retention rate reached 75.0%, which is much higher than that of the uncoated pure LRM sample (44.36%). At the same time, the average voltage decay rate was only 0.076mV / cycle, which is about 70% lower than that of the uncoated sample (0.237mV / cycle), achieving dual stability of capacity and voltage.

[0020] The preparation method of this invention is simple and controllable, suitable for large-scale industrial production. The entire preparation process does not require complex special equipment. The selected cerium nitrate precursor is inexpensive and readily available. All process parameters (stirring time, ultrasonic power, calcination temperature / time / heating rate, etc.) are parameters that can be precisely controlled in conventional chemical production, and the process has good repeatability. The supporting preparation system realizes continuous operation of the coating process, reduces powder loss and pollution, reduces the difficulty of operation, is inexpensive, and is suitable for the needs of large-scale industrial production. Moreover, no toxic or harmful by-products are generated in the production process, making it environmentally friendly.

[0021] The interfacial interaction between the cerium oxide coating layer and the LRM matrix in this invention enhances the adhesion of the coating layer, preventing it from detaching during cycling. At the same time, it does not change the layered lithium storage structure of the LRM matrix itself, ensuring the material's high specific capacity and high energy density advantages. The modified LRM material exhibits significantly improved structural stability under high voltage, meeting the application requirements of next-generation high-energy-density, long-cycle-life lithium-ion batteries, and is particularly suitable for power battery products in the field of transportation electrification. Attached Figure Description

[0022] Figure 1 Scanning electron microscope (SEM) images of LRM without coating and LRM@1.0CeO2.

[0023] Figure 2 Transmission electron microscopy (TEM) images of uncoated LRM and LRM@1.0CeO2.

[0024] Figure 3 EDS image of Ce element for LRM@1.0CeO2.

[0025] Figure 4 XRD patterns of uncoated LRM and LRM with different CeO2 coating amounts.

[0026] Figure 5 XPS spectra of uncoated LRM and LRM with different CeO2 coating amounts.

[0027] Figure 6 The graph shows the electrochemical performance of uncoated LRM and LRMs with different CeO2 coating amounts.

[0028] Figure 7 This is a schematic diagram of the preparation system of the present invention. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0030] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with conventional techniques or conditions described in the literature in this field and the techniques or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. The source, trade name, and, where necessary, composition of the reagents used shall be indicated upon their first appearance; thereafter, unless otherwise specified, the same information shall apply to the same reagents used.

[0031] Example: A cerium oxide-coated modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based matrix, the surface of which is coated with a continuous, dense, and uniform cerium oxide (CeO2) layer, and the lithium-rich manganese-based matrix is ​​a lithium-rich manganese-based compound.

[0032] The thickness of the cerium oxide layer is precisely controlled within 3-5 nanometers. This thickness range can form an effective physical barrier to isolate the LRM substrate from the electrolyte, while not hindering the rapid conduction of lithium ions between the material surface and the bulk phase, thus balancing protection and ion conduction performance. The cerium oxide layer contains Ce 3+ and Ce 4+ The coexistence of reversible redox pairs, in which Ce 3+ The proportion of oxygen is 25-30%, and this valence distribution makes the cerium oxide layer rich in oxygen vacancies, providing active sites for the capture and stabilization of lattice oxygen; A slight interfacial interaction exists between the cerium oxide layer and the LRM matrix, causing a slight expansion of the LRM matrix lattice, which enhances the interfacial bonding force and prevents the coating layer from falling off during cycling. At the same time, it does not change the typical layered α-NaFeO2 structure (R-3m space group) of the LRM matrix, thus ensuring the lithium storage and release performance of the matrix itself.

[0033] Lithium-rich manganese-based cathode materials leverage the structural and compositional advantages of the cerium oxide layer to achieve a dual function of physical barrier and oxygen buffer, fundamentally solving the capacity decay and voltage decay problems of traditional LRM materials, and significantly improving electrochemical performance.

[0034] A method for preparing a cerium oxide-coated modified lithium-rich manganese-based cathode material includes the following steps: Pretreatment of lithium-rich manganese matrix: Cleaning and vacuum drying of the lithium-rich manganese matrix; The lithium-rich manganese-based substrate was ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove surface impurities, and then vacuum dried at 80°C for 12 hours. The lithium-rich manganese-based matrix uses commercially available lithium-rich manganese-based compounds, preferably Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 was used to weigh a quantitative amount of lithium-rich manganese-based compound and place it in an ultrasonic cleaning tank. Anhydrous ethanol was added as the cleaning medium, and the ultrasonic power was controlled at 100-300W for 15 minutes. This application utilizes the ultrasonic cavitation effect to remove impurities such as dust, residual electrolytes, and loose by-products generated during the preparation process adsorbed on the LRM surface, while simultaneously breaking up slightly aggregated secondary LRM particles to ensure a clean and well-dispersed matrix surface. After cleaning, LRM and anhydrous ethanol were separated by vacuum filtration using a Buchner funnel. The separated LRM was then spread evenly in a quartz petri dish (with a thickness not exceeding 1 cm) and placed in a vacuum drying oven. The drying temperature was set at 80℃ and the vacuum degree at -0.08~-0.1MPa for 12 hours. Vacuum drying rapidly removes anhydrous ethanol from the material surface and pores, avoiding residual moisture that could cause localized concentration changes in the precursor solution upon contact with water, thus ensuring effective adsorption of the precursor to the matrix surface. After drying, the powder was removed and sealed for storage to prevent moisture absorption from affecting subsequent processes.

[0035] (2) Preparation of precursor solution: Prepare an aqueous solution of cerium nitrate (Ce(NO3)3・6H2O), stir until completely dissolved, and obtain cerium oxide precursor solution; Dissolve cerium nitrate (Ce(NO3)3・6H2O) in deionized water and stir mechanically for 30 minutes until completely dissolved to prepare a transparent cerium oxide precursor solution with a concentration of 0.05-0.15 mol / L. Cerium nitrate hexahydrate (Ce(NO3)3⋅6H2O) with a purity ≥99.9% was selected as the cerium oxide precursor. It was dissolved in high-purity deionized water with a resistivity >18.2 MΩ・cm and mechanically stirred for 30 minutes until the cerium nitrate hexahydrate was completely dissolved, to prepare a colorless, transparent cerium oxide precursor solution with a concentration of 0.05-0.15 mol / L, free of visible solid particles. The next step was carried out immediately after preparation to avoid solvent evaporation or precursor hydrolysis. The selection of high-purity raw materials and solvents avoided the negative impact of impurity ions on the electrochemical performance of subsequent materials. Precise concentration control laid the foundation for the control of subsequent coating amount.

[0036] (3) Precursor coating: The pretreated lithium-rich manganese matrix is ​​added to the cerium oxide precursor solution in proportion, and after mechanical stirring, it is ultrasonically treated so that the precursor is uniformly adsorbed on the surface of the lithium-rich manganese matrix. Lithium-rich manganese-based matrix powder is added to the precursor solution, mechanically stirred for 1-3 hours, and then ultrasonically treated for 20-40 minutes with an ultrasonic power of 100-300W. The uniformity of the cerium oxide coating layer is ensured through the synergistic effect of stirring and ultrasound. According to the mass ratio of cerium nitrate to LRM matrix of 0.5:100, 1.0:100, 2.0:100, or 5.0:100, the pretreated LRM powder is slowly added to the precursor solution. Mechanical stirring is performed at room temperature for 1-3 hours to prevent powder agglomeration and the formation of sediment or scum, ensuring sufficient contact between the LRM powder and the precursor solution. Utilizing the shear force, dispersion force, and convection of the stirring, the precursor is fully and uniformly adsorbed onto the surface and pores of the LRM matrix, forming a preliminary precursor adsorption layer. After mechanical stirring, the entire mixed suspension is transferred to an ultrasonic disperser, and the ultrasonic power is set to 100-300W for ultrasonic treatment for 20-40 seconds. For minutes, the cavitation effect and vibration of ultrasound eliminate the uneven coating phenomena such as excessive local adsorption and particle agglomeration of precursors caused by mechanical stirring, so that the cerium nitrate precursor is uniformly dispersed at the molecular level on the LRM matrix surface, forming a continuous and thin precursor adsorption layer; the suspension is kept at room temperature during the ultrasound process to avoid the heat generated by ultrasound causing solvent evaporation and affecting the precursor concentration.

[0037] Separation and drying: The lithium-rich manganese matrix coated in step (3) is collected by vacuum filtration, washed and dried to obtain precursor coated lithium-rich manganese matrix powder; After coating, the LRM powder was purified by washing it three times with deionized water and anhydrous ethanol alternately. This effectively removed unadsorbed free cerium nitrate precursor, water-soluble impurities, and residual ions from the powder surface, preventing the formation of impurities during the calcination stage. The washed powder was then placed in a vacuum drying oven and dried at a constant temperature of 80°C for 12 hours to prevent the coating layer from cracking and falling off due to rapid solvent evaporation during calcination. This resulted in dry precursor-coated LRM powder with no solvent residue in the powder. Calcination and forming: The precursor-coated lithium-rich manganese-based matrix powder is placed in a sintering furnace, calcined under a specific atmosphere and naturally cooled to room temperature, so that the precursor is transformed into a cerium oxide coating layer, and cerium oxide-coated lithium-rich manganese-based cathode material is obtained. The calcination atmosphere is one of air, oxygen or inert gas, the calcination temperature is 400-600℃, the calcination time is 4-6 hours, the heating rate is 4-6℃ / min, and the calcination is allowed to cool naturally to room temperature.

[0038] The dried precursor-coated lithium-rich manganese-based matrix powder is placed in a high-temperature resistant alumina crucible. The crucible is then placed in a muffle furnace or tube furnace, and the temperature is slowly increased to 400-600℃ at a rate of 4-6℃ / min under a calcination atmosphere of air, oxygen, or inert gas. The mixture is then calcined at this temperature for 4-6 hours. During the calcination process, the cerium nitrate precursor undergoes a complete thermal decomposition reaction, transforming into cerium oxide (CeO2). This cerium oxide then forms a strong interfacial bond on the LRM matrix surface through a high-temperature solid-state reaction, resulting in a uniform, dense, and stable cerium oxide coating layer. After calcination, the heating device is turned off, allowing the material in the furnace to cool naturally to room temperature. This avoids thermal stress caused by rapid cooling, which could lead to microcracks between the coating layer and the matrix, or coating layer detachment. Finally, a cerium oxide-coated modified lithium-rich manganese-based cathode material is obtained.

[0039] The preparation method employs a step-by-step, controllable process involving LRM matrix pretreatment, cerium oxide precursor solution preparation, uniform precursor coating, separation and drying, and calcination. This, combined with precise optimization and synergistic control of process parameters at each step, the use of a combination of stirring and ultrasound, precise control of concentration and coating ratio, and a gentle calcination and cooling regime, ensures the uniformity and density of the cerium oxide coating layer. Simultaneously, it avoids the problems of excessively thick coating layers hindering lithium-ion conduction or excessively thin layers leading to insufficient protection. This achieves a uniform, dense, and robust coating of cerium oxide on the LRM matrix surface, effectively preventing issues such as coating layer agglomeration, cracking, and poor adhesion, significantly improving the structural stability and electrochemical performance of the final product.

[0040] A preparation system for a method of preparing cerium oxide-coated modified lithium-rich manganese-based cathode material includes a main equipment body that integrates stirring, ultrasonic dispersion, temperature control, and waste liquid discharge functions. It is adapted to the mixing and coating reaction of lithium-rich manganese-based matrix and cerium oxide precursor, and the precursor solution preparation process, realizing the integrated operation of "precursor solution preparation - uniform coating - process control". This avoids problems such as powder loss, contamination, and coating layer damage that occur during the transfer of multiple equipment, effectively ensuring the uniformity of the coating layer and the continuity of the process.

[0041] The main body of the equipment includes a sealed reaction vessel, which integrates the following key components both externally and internally. Each component is independently adjustable yet works collaboratively to precisely adapt to the parameter requirements of the preparation process: Stirring system: The reaction vessel is equipped with a stirring paddle, which is connected to the external power mechanism of the vessel. It can realize continuous mechanical stirring for 1-3 hours at room temperature. The stirring rate is adjustable. It is used for the dissolution and stirring of cerium nitrate hexahydrate during the preparation of precursor solution (ensuring complete dissolution within 30 minutes), as well as for the full adsorption and stirring after the lithium-rich manganese matrix and the precursor solution are mixed, ensuring that the precursor is uniformly attached to the surface of the lithium-rich manganese matrix. Ultrasonic dispersion system: The reaction vessel is equipped with an ultrasonic transducer on the side wall or bottom. An ultrasonic power adjustment button is provided on the outside of the vessel, which can precisely control the ultrasonic power to achieve precise control of 100-300W ultrasonic power, adapting to the ultrasonic treatment requirements of 20-40 minutes. It is used to eliminate the uneven coating phenomenon that may exist after stirring, promote the uniform dispersion of the precursor on the LRM surface, and form a synergistic effect with the stirring system. Temperature control system: The reaction vessel is wrapped with a heating module, which is equipped with heating wires inside. The temperature control knob is located on the outside of the vessel, which can achieve precise temperature control within the range of 0-100℃. It is suitable for auxiliary dissolution temperature control during precursor solution preparation, as well as maintaining the constant temperature environment required throughout the coating process (such as mild reaction conditions below 80℃), to avoid premature decomposition of the precursor due to excessively high local temperatures. Auxiliary functional components: The bottom of the reaction vessel is equipped with a drain outlet for the rapid and thorough discharge of waste liquid after the experiment, so as to avoid residual impurities affecting subsequent experiments; the side wall of the vessel is equipped with a power interface to provide unified power supply for the stirring system, ultrasonic dispersion system and temperature control system, so as to ensure the integrated operation of the equipment; the area inside the reaction vessel corresponding to the heating module is the heating zone to ensure heating uniformity and avoid local overheating that could cause premature decomposition of the precursor.

[0042] The preparation system of this application is an integrated preparation device with a simple overall structure and convenient operation. Each process parameter can be independently and precisely controlled, which is compatible with the preparation method of this invention. It not only improves the process repeatability of laboratory preparation, but also provides an equipment foundation for subsequent industrial scale-up production, effectively reducing equipment investment and operating costs in the production process.

[0043] To verify the effect of cerium oxide coating modification with different preparation ratios on the performance improvement of lithium-rich manganese-based cathode materials, Experiments 1-3 were set up. Example 1: Preparation of lithium-rich manganese-based cathode material (LRM@0.5CeO2) with cerium oxide coating modified by cerium nitrate to LRM at a mass ratio of 0.5:100, with a cerium oxide coating thickness of approximately 3 nm; The preparation method of the lithium-rich manganese-based cathode material in Experimental Example 1 is the same as that in the above examples. The difference is that 10.0g of commercial lithium-rich manganese-based compound is selected, and 0.05g of cerium nitrate hexahydrate and 300mL of high-purity deionized water are accurately weighed according to the concentration ratio of 0.05mol / L to prepare a cerium oxide precursor solution. 10.0g of lithium-rich manganese-based compound is added to the cerium oxide precursor solution to uniformly coat the precursor. After separation, drying and calcination molding processes, LRM@0.5CeO2 cathode material is obtained, and the thickness of its cerium oxide coating layer is about 3nm. Example 2: Preparation of cerium oxide-coated lithium-rich manganese-based cathode material (LRM@1.0CeO2) with a cerium nitrate to LRM mass ratio of 1.0:100 and a cerium oxide coating thickness of approximately 4 nm; The preparation method of the lithium-rich manganese-based cathode material in Experimental Example 2 is the same as that in the above examples. The difference is that 10.0g of commercial lithium-rich manganese-based compound is selected, and 0.10g of cerium nitrate hexahydrate and 300mL of high-purity deionized water are accurately weighed according to the concentration ratio of 0.10mol / L to prepare a cerium oxide precursor solution. 10.0g of lithium-rich manganese-based compound is added to the cerium oxide precursor solution to uniformly coat the precursor. After separation, drying and calcination molding processes, LRM@1.0CeO2 cathode material is obtained, and the thickness of its cerium oxide coating layer is about 4nm. Example 3: Preparation of cerium oxide-coated lithium-rich manganese-based cathode material (LRM@5.0CeO2) with a cerium nitrate to LRM mass ratio of 5.0:100 and a cerium oxide coating thickness of approximately 5 nm; The preparation method of the lithium-rich manganese-based cathode material in Experimental Example 2 is the same as that in the above examples. The difference is that 10.0g of commercial lithium-rich manganese-based compound was selected, and 0.50g of cerium nitrate hexahydrate and 300mL of high-purity deionized water were accurately weighed according to the concentration ratio of 0.15mol / L to prepare a cerium oxide precursor solution. 10.0g of lithium-rich manganese-based compound was added to the cerium oxide precursor solution to uniformly coat the precursor. After separation, drying and calcination molding processes, LRM@5.0CeO2 cathode material was obtained, and the thickness of its cerium oxide coating layer was about 5nm. To verify the effect of cerium oxide coating modification on the performance improvement of lithium-rich manganese-based cathode materials, a comparative example was set up: Comparative Example: Preparation of uncoated pure LRM cathode material. The specific preparation steps are as follows: Select commercially available lithium-rich manganese-based compound Li 1.2 Mn 0.54 Ni 0.13 Co 0.13Using O2 as a raw material, accurately weigh 10.0g of LRM powder and place it in a 500mL ultrasonic cleaning tank. Add 200mL of anhydrous ethanol, set the ultrasonic power to 200W, and ultrasonically clean at room temperature for 15 minutes. After vacuum filtration and separation, the LRM powder was spread evenly on a quartz petri dish and placed in a vacuum drying oven, where it was dried at 80℃ and -0.09MPa for 12 hours. After drying, the powder is removed, ground through a 200-mesh sieve in an agate mortar, and sealed for storage to obtain uncoated pure LRM cathode material.

[0044] Performance Testing and Result Analysis The cathode materials prepared in Experimental Examples 1-3 and the comparative examples were characterized structurally and tested electrochemically to verify the structural characteristics of the cerium oxide coating and the improvement effect of the modified material on electrochemical performance. The test methods were all conventional test methods in the field of lithium-ion battery materials, and the test conditions were uniformly 1C rate and 2.0-4.8V voltage range.

[0045] Figure 1 The images are scanning electron microscope (SEM) images of LRM without coating and LRM@1.0CeO2, where a and c represent SEM images of LRM without coating at different scales, and b and d represent SEM images of LRM@1.0CeO2 at different scales. Figure 2 The images are transmission electron microscopy (TEM) images of LRM without coating and LRM@1.0CeO2, where e represents the TEM image of LRM without coating and f represents the TEM image of LRM@1.0CeO2. Figure 1 as well as Figure 2 SEM and TEM images show that the uncoated LRM has a secondary particle aggregation structure, while the LRM@1.0CeO2 surface forms a uniform and continuous CeO2 coating layer (thickness ≈4nm) with no obvious agglomeration.

[0046] Figure 3 The image shows the EDS image of Ce element in LRM@1.0CeO2. As can be seen from the image, Ce element is uniformly distributed on the surface of LRM@1.0CeO2.

[0047] Figure 4The XRD patterns of uncoated LRM and LRM@0.5CeO2, LRM@1.0CeO2, and LRM@5.0CeO2 are shown, where a is the full spectrum, b is a magnified view of the (104) crystal plane, and c is a magnified view of the (003) crystal plane. The XRD patterns show that the coated LRM still maintains a typical layered α-NaFeO2 structure (R-3m space group), with no CeO2 impurity peaks (due to low content dispersion). The (003) and (104) crystal plane peaks are slightly shifted to lower angles, indicating a slight expansion of the lattice due to Ce ion doping, confirming the interfacial interaction between CeO2 and LRM. Figure 5 XPS tests showed that CeO2 was present in the CeO2 layer. 3+ and Ce 4+ coexist.

[0048] like Figure 6 As shown, under the test conditions of 1C rate and 2.0-4.8V: the initial discharge capacity of the uncoated LRM was 214.4mAh / g, which decreased to 95.1mAh / g after 500 cycles, with a capacity retention of 44.36% and an average voltage decay rate of 0.237mV / cycle; the initial discharge capacity of LRM@1.0CeO2 was 226.8mAh / g, which remained at 169.65mAh / g after 500 cycles, with a capacity retention of 75.0% and an average voltage decay rate of only 0.076mV / cycle; the performance of LRM@0.5CeO2 and LRM@5.0CeO2 was the next best, with the former having limited protection due to insufficient coating and the latter having an excessively thick coating layer that hindered lithium-ion conduction.

[0049] The above performance test results fully demonstrate that the electrochemical performance of the lithium-rich manganese-based cathode material modified by cerium oxide coating in this invention is significantly improved compared with the uncoated pure LRM material. The optimal ratio of cerium nitrate to LRM is 1.0:100, at which the thickness, uniformity, and interfacial bonding of the cerium oxide coating layer are all optimal. This ratio can fully exert the dual functions of physical barrier and oxygen buffer, effectively suppressing the release of lattice oxygen, dissolution of transition metals, and structural phase transition of LRM material, while not hindering the conduction of lithium ions, thus achieving a dual improvement in cycle stability and voltage retention.

[0050] The above embodiments demonstrate that the present invention, through an optimized cerium oxide coating process, successfully prepares high-performance cerium oxide-coated modified lithium-rich manganese-based cathode materials, effectively solving the core problems of severe capacity and voltage decay in existing lithium-rich manganese-based materials. Furthermore, the preparation method of the present invention is simple and controllable, uses readily available raw materials, and is low in cost. All equipment used is conventional, requiring no stringent reaction conditions. The accompanying preparation system also enables continuous operation of the coating process, significantly improving process repeatability and production efficiency, and has significant prospects for industrial application. All equivalent changes and modifications made according to the claims and description of the present invention should be covered within the scope of protection of the present invention.

[0051] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A cerium oxide-coated modified lithium-rich manganese-based cathode material, characterized in that: It includes a lithium-rich manganese-based matrix, the surface of which is coated with a cerium oxide layer, and the lithium-rich manganese-based matrix is ​​a lithium-rich manganese-based compound.

2. The cerium oxide-coated modified lithium-rich manganese-based cathode material according to claim 1, characterized in that: The thickness of the cerium oxide layer is 3-5 nanometers.

3. The cerium oxide-coated modified lithium-rich manganese-based cathode material according to claim 1, characterized in that: The cerium oxide layer has Ce 3+ and Ce 4+ .

4. A method for preparing a cerium oxide-coated modified lithium-rich manganese-based cathode material, characterized in that: Includes the following steps: Pretreatment of lithium-rich manganese matrix: Cleaning and vacuum drying of the lithium-rich manganese matrix; Preparation of precursor solution: Prepare an aqueous solution of cerium nitrate (Ce(NO3)3・6H2O), stir until completely dissolved, to obtain a cerium oxide precursor solution; Precursor coating: The pretreated lithium-rich manganese-based matrix is ​​added to the cerium oxide precursor solution in a certain proportion, mechanically stirred and then ultrasonically treated to allow the precursor to be adsorbed onto the surface of the lithium-rich manganese-based matrix. Separation and drying: The lithium-rich manganese matrix coated in step (3) is collected by vacuum filtration, washed and dried to obtain precursor coated lithium-rich manganese matrix powder; Calcination and forming: The precursor-coated lithium-rich manganese-based matrix powder is placed in a sintering furnace, calcined under a specific atmosphere and naturally cooled to room temperature, so that the precursor is transformed into a cerium oxide coating layer, and cerium oxide-coated lithium-rich manganese-based cathode material is obtained.

5. The method for preparing a cerium oxide-coated modified lithium-rich manganese-based cathode material according to claim 4, characterized in that: The pretreatment step of the lithium-rich manganese matrix is ​​to ultrasonically clean the lithium-rich manganese matrix with anhydrous ethanol for 15 minutes, remove surface impurities and disperse slightly agglomerated LRM secondary particles through ultrasonic cavitation effect, and vacuum dry at 80°C for 12 hours.

6. The method for preparing a cerium oxide-coated modified lithium-rich manganese-based cathode material according to claim 4, characterized in that: The concentration of the cerium oxide precursor solution is 0.05–0.15 mol / L.

7. The method for preparing a cerium oxide-coated modified lithium-rich manganese-based cathode material according to claim 4, characterized in that: In the precursor coating step, the pretreated lithium-rich manganese-based matrix powder is added to the cerium oxide precursor solution at a mass ratio of cerium nitrate to lithium-rich manganese-based matrix of 0.5:100, 1.0:100, 2.0:100, or 5.0:

100. In this step, the shear force, dispersion force, and convection of mechanical stirring cause the precursor to be adsorbed on the surface and pores of the lithium-rich manganese-based matrix, forming a preliminary precursor adsorption layer. In this step, the cavitation effect and vibration of ultrasound are used to eliminate the uneven precursor coating caused by mechanical stirring, so that the cerium nitrate precursor is molecularly dispersed on the surface of the lithium-rich manganese-based matrix, forming a continuous and thin precursor adsorption layer.

8. The method for preparing a cerium oxide-coated modified lithium-rich manganese-based cathode material according to claim 4, characterized in that: In the calcination and forming step, the temperature is slowly increased to 400-600℃ at a heating rate of 4-6℃ / min in a calcination atmosphere of air, oxygen or inert gas, and then calcined at this temperature for 4-6 hours. During the calcination process, the cerium nitrate precursor undergoes a complete thermal decomposition reaction and is completely converted into cerium oxide. It then forms a strong interfacial bond on the surface of the LRM matrix through a high-temperature solid-phase reaction, forming a cerium oxide coating layer.

9. The preparation system used in the method for preparing a cerium oxide-coated modified lithium-rich manganese-based cathode material according to any one of claims 4-8, characterized in that: The equipment includes the main body, which comprises a reaction vessel. The reaction vessel integrates a stirring system, an ultrasonic dispersion system, a temperature control system, and auxiliary functional components. The stirring system is connected to the external power mechanism of the container and is used for dissolving and stirring cerium nitrate hexahydrate during the preparation of the precursor solution, as well as for adsorption and stirring after the lithium-rich manganese matrix and the cerium nitrate precursor are mixed, so that the precursor is attached to the surface of the lithium-rich manganese matrix. The ultrasonic dispersion system includes an ultrasonic transducer mounted on the side wall or bottom of the reaction vessel and an ultrasonic power adjustment button on the outside of the vessel. The ultrasonic power is precisely controlled to eliminate uneven coating after stirring, promote uniform dispersion of the precursor on the LRM surface, and form a synergistic effect with the stirring system. The temperature control system includes a heating module wrapped around the outside of the reaction vessel. The heating module is equipped with heating wires inside and a temperature control knob is located on the outside of the vessel. It can achieve precise temperature control within the range of 0-100℃, adapt to the auxiliary dissolution temperature control during the preparation of precursor solution, and maintain the constant temperature environment required throughout the coating process. The auxiliary functional components include a drain outlet at the bottom of the reaction vessel and a power interface on the side wall of the vessel. The drain outlet is used for the discharge of waste liquid after the experiment. The power interface provides unified power supply for the stirring system, ultrasonic dispersion system and temperature control system, ensuring the integrated operation of the equipment.

10. The application of the cerium oxide-coated modified lithium-rich manganese-based cathode material according to claims 1-2 in lithium-ion batteries.

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