Lithium battery mechanical-chemical blended positive electrode material and preparation method thereof

Abstract

This invention provides a mechatronic blended cathode material for lithium batteries and its preparation method. The mechatronic blended cathode material consists of micron-sized lithium cobalt oxide particles and nano-sized lithium manganese iron phosphate particles. The lithium cobalt oxide is a layered, high-capacity cathode material, while the lithium manganese iron phosphate is an olivine-type, highly stable cathode material. This mechatronic blended cathode material is prepared through an integrated process of wet mixing, vacuum drying, gradient high-energy ball milling, and gradient micron-mesh sieving. The gradient high-energy ball milling employs alternating forward and reverse rotation with gradient speed increases and decreases, anchoring the nano-sized lithium manganese iron phosphate particles to the surface of the micron-sized lithium cobalt oxide particles through mechatronic action, forming a discontinuous protective interface that protects the lithium cobalt oxide cathode particles from continuous electrolyte erosion during cycling. The interaction between the two cathode materials gives the mechatronic blended cathode material high ionic conductivity and excellent electrochemical performance, meeting the high specific energy and high safety requirements of lithium batteries. The preparation process is controllable and highly adaptable, suitable for the industrial production of lithium-ion battery cathode materials.

Description

Technical Field

[0001] This invention relates to the field of lithium battery cathode material development, specifically to a lithium battery mechanochemical blend cathode material and its preparation method. Background Technology

[0002] Currently, the new energy industry, as a core supporting field for the development of new productive forces and the promotion of new equipment, places higher demands on the performance of new energy devices and key materials. High specific energy and high safety have become the core research and development directions for lithium-ion battery cathode materials. Lithium-ion batteries are widely used in fields such as 3C electronic products, among which lithium cobalt oxide cathode materials are highly regarded due to their high theoretical specific capacity (274 mAh / g) and high energy density (4.45 V vs Li / Li). + Theoretical energy density approximately 740 Wh / kg), high pressure density (4.2 g / cm³), high Li + Its advantages, such as high conductivity and high electronic conductivity, have made it a key research focus for cathode materials in lithium-ion batteries.

[0003] However, lithium cobalt oxide cathode materials have obvious technical defects in practical applications: during multiple charge-discharge cycles of lithium batteries, the electrolyte will react with the lithium cobalt oxide cathode material, continuously eroding the lithium cobalt oxide particles, causing damage to the particle surface, destroying its crystal structure stability and interface stability, thereby causing rapid degradation of battery performance and exacerbating the risk of thermal runaway, which seriously limits the further promotion and application of lithium cobalt oxide cathode materials.

[0004] To address these issues, existing technologies have proposed modification strategies such as elemental doping and surface coating. However, these traditional modification methods involve complex preparation processes, high production costs, and are not environmentally friendly, making large-scale industrial application difficult. Furthermore, existing technologies lack a process for achieving efficient mechanochemical blending of lithium cobalt oxide and high-stability cathode materials. This makes it impossible to achieve a tight bond between the two materials in a simple and controllable manner, hindering the improvement of cycle stability and safety while maintaining the high specific energy advantage of lithium cobalt oxide. Simultaneously, the optimization of the mechanochemical blending ratio lacks a clear direction, and the bonding mechanism between lithium cobalt oxide and high-stability cathode materials is unclear, preventing the optimization of battery performance.

[0005] To address the shortcomings of the existing technology, a simple, controllable, low-cost, and environmentally friendly preparation method is needed. This method would address the issues of lithium cobalt oxide particles being easily corroded by electrolytes, rapid battery performance degradation, and insufficient safety through a mechanochemical blending strategy, thereby achieving a balance between high specific energy and high safety in lithium batteries.

[0006] A patent search revealed invention patent CN111916688A, which discloses a method for preparing a high-capacity, high-voltage lithium cobalt oxide composite cathode material, including the following steps: 1. Preparing a first type of cathode material I and refining it; 2. Post-processing the refined cathode material I to obtain nanoscale cathode material I; 3. Mixing the nanoscale cathode material I with a second type of cathode material II to obtain the lithium cobalt oxide composite cathode material. This patented preparation process lacks precise control steps such as gradient high-energy ball milling; it only involves simple mixing and cannot form a stable protective interface.

[0007] In summary, given the problems of the existing technologies, researching a mechanical-chemical blended cathode material for lithium batteries and its preparation method has become a critical task that urgently needs to be addressed. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the purpose of this invention is to provide a lithium battery mechanical-chemical blended cathode material and its preparation method.

[0009] A method for preparing a lithium battery mechanochemical blended cathode material according to the present invention includes the following steps: Micron-sized lithium cobalt oxide particles and nano-sized lithium manganese iron phosphate particles are wet-mixed, vacuum-dried, and then subjected to gradient high-energy ball milling to obtain a mechanochemical blended cathode material. The gradient high-energy ball mill uses an alternating forward and reverse rotation method, with the preset speed gradient increasing and then decreasing sequentially to form at least one speed-up and speed-down cycle; Gradient high-energy ball milling includes a low-speed section, a medium-speed section, and a high-speed section. The low-speed section is used to initially mix the two materials evenly. The medium-speed section is used to evenly distribute the nano-sized lithium manganese iron phosphate particles onto the surface of the micron-sized lithium cobalt oxide particles. The high-speed section is used to anchor the lithium manganese iron phosphate particles onto the surface of the lithium cobalt oxide particles through mechanochemical action, forming a discontinuous protective interface.

[0010] Preferably, the wet mixing process includes: weighing and pre-grinding lithium cobalt oxide particles and lithium manganese iron phosphate particles according to the mixing ratio, then placing them in an organic solvent and stirring to mix. The organic solvent is N-methylpyrrolidone, the stirring speed is 200-700 r / min, and the stirring time is 10-14 h.

[0011] Preferably, the vacuum drying temperature is 60–120°C, the vacuum degree is -0.1–-0.5 MPa, and the drying time is 12–20 h.

[0012] Preferably, the rotational speed range of the gradient high-energy ball mill is 500–1500 r / min, and the rotational speed gradient is 100–500 r / min.

[0013] Preferably, in the gradient high-energy ball milling, the rotation speed in the low-speed section is 500-700 r / min, the rotation speed in the medium-speed section is 800-900 r / min, the rotation speed in the high-speed section is 1000-1200 r / min, the single ball milling time is 10-12 min, and the number of speed-up and speed-down cycles is 1-4.

[0014] Preferably, during the gradient high-energy ball milling process, the material temperature is controlled at 60-80°C, the ball milling process is carried out under vacuum conditions, and the rotation mode is alternating between rotation and revolution.

[0015] Preferably, after gradient high-energy ball milling, a gradient micron-mesh sieving step is also included, in which sieves with increasing mesh sizes are used for grading and screening, with the mesh size range being 50 to 500 mesh, to finally obtain a mechanochemical blended cathode material with a particle size of 15 to 25 μm, and the sieving time for each stage is 10 to 20 min.

[0016] The present invention also provides a lithium battery mechanochemical blended cathode material obtained by the above-mentioned preparation method of lithium battery mechanochemical blended cathode material. The lithium battery mechanochemical blended cathode material is composed of micron-sized lithium cobalt oxide particles and nano-sized lithium manganese iron phosphate particles. The nano-sized lithium manganese iron phosphate particles are anchored to the surface of the micron-sized lithium cobalt oxide particles through mechanochemical action to form a discontinuous protective interface.

[0017] Preferably, the particle size of lithium cobalt oxide particles is 5–30 μm, and the particle size of lithium manganese iron phosphate particles is 80–500 nm; based on a total weight of 10 parts, lithium cobalt oxide accounts for 3–7 parts, and lithium manganese iron phosphate accounts for 7–3 parts.

[0018] Preferably, the lithium battery mechanical-chemical blended cathode material is used in lithium batteries operating at 3.0–4.45 V, with a theoretical specific capacity of 170–175 mAh / g.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention employs an integrated process of wet mixing, vacuum drying, gradient high-energy ball milling, and gradient micron-mesh sieving to prepare mechanochemical blended cathode materials for lithium batteries. The gradient high-energy ball milling uses an alternating forward and reverse rotation with a gradient increase and decrease in rotation speed. The parameters of the vacuum drying and gradient micron-mesh sieving steps are controllable. The entire preparation process is simple, stable, highly efficient, and environmentally friendly. The mechanochemical blended cathode materials prepared by this process have a particle size controlled at 15–25 μm, uniform particle distribution, and stable structure, enabling large-scale production.

[0020] 2. In the integrated preparation process, the low-speed section of the gradient high-energy ball mill can initially and uniformly mix lithium cobalt oxide and lithium manganese iron phosphate. The medium-speed section can uniformly distribute lithium manganese iron phosphate particles on the surface of lithium cobalt oxide particles. The high-speed section can form a discontinuous protective interface through mechanochemical action, effectively reducing the erosion of lithium cobalt oxide particles by the electrolyte, enhancing the structural stability, capacity release capability and cycle stability of the lithium cobalt oxide cathode, and significantly improving the comprehensive electrochemical performance of the mechanochemical blend cathode material. This enables the theoretical specific capacity of the mechanochemical blend cathode material to reach 170-175 mAh / g, which is suitable for lithium batteries operating at 3.0-4.45 V.

[0021] 3. The mechanochemical blending cathode strategy and integrated preparation process of the present invention have universality. In addition to the mechanochemical blending system of lithium cobalt oxide and lithium manganese iron phosphate, this strategy and process can also be applied to the mechanochemical blending preparation of cathode materials of other systems, and can be widely used in lithium-ion battery cathode materials and related energy fields. Attached Figure Description

[0022] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a flowchart illustrating a method for preparing a lithium battery mechanical-chemical blended cathode material according to an embodiment of the present invention. Figure 2 This is a cycle life test diagram of the LCO-3 (LCO:LFMP=3:7) cathode material in an embodiment of the present invention. Figure 3 This is a TEM image of the LCO-5 (LCO:LFMP=5:5) cathode material in an embodiment of the present invention; Figure 4 This is a cycle life test diagram of the LCO-5 (LCO:LFMP=5:5) cathode material in an embodiment of the present invention; Figure 5 This is a cycle life test diagram of the LCO-7 (LCO:LFMP=7:3) cathode material in an embodiment of the present invention; Figure 6 This is a cycle life test diagram of the LCO cathode material in the comparative example of this invention; Figure 7 This is a cycle life test diagram of the LFMP cathode material in the comparative example of this invention; Figure 8 This is a cycle life test diagram of the LCO / LFMP-3-C cathode material in the comparative example of this invention; Detailed Implementation The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0023] This invention discloses a mechanochemical blended cathode material for lithium batteries and its preparation method. The mechanochemical blended cathode material consists of micron-sized lithium cobalt oxide particles and nano-sized lithium manganese iron phosphate particles. The lithium cobalt oxide is a layered, high-capacity cathode material, while the lithium manganese iron phosphate is an olivine-type, highly stable cathode material. This mechanochemical blended cathode material is prepared through an integrated process of wet mixing, vacuum drying, gradient high-energy ball milling, and gradient micron-mesh sieving. The gradient high-energy ball milling employs alternating forward and reverse rotation with gradient speed increases and decreases, anchoring the nano-sized lithium manganese iron phosphate particles to the surface of the micron-sized lithium cobalt oxide particles through mechanochemical action, forming a discontinuous protective interface. This protects the lithium cobalt oxide cathode particles from continuous electrolyte erosion during cycling. The interaction between the two cathode materials gives the mechanochemical blended cathode material high ionic conductivity and excellent electrochemical performance, meeting the high specific energy and high safety requirements of lithium batteries. The preparation process is controllable and highly adaptable, suitable for the industrial production of lithium-ion battery cathode materials.

[0024] Example 1: This embodiment provides a method for preparing a lithium battery mechanical-chemical blended cathode material, including the following steps: Micron-sized lithium cobalt oxide particles and nano-sized lithium manganese iron phosphate particles are wet-mixed and vacuum-dried, then subjected to gradient high-energy ball milling, followed by a gradient micron-mesh sieving step, using sieves with increasing mesh sizes for classification and sieving to obtain a mechanochemical blended cathode material.

[0025] Specifically, wet mixing utilizes the high wettability of organic solvents to achieve molecular-level pre-distribution of lithium cobalt oxide and lithium manganese iron phosphate in a liquid phase system, effectively eliminating residual gas between powders and ensuring uniformity of initial contact. In this embodiment, wet mixing includes: weighing lithium cobalt oxide particles (LCO, average particle size 12 μm) and lithium manganese iron phosphate particles (LFMP, average particle size 200 nm) at a mass ratio of 3:7, grinding them four times with an agate mortar for 10 min each time to obtain a premixed material. The premixed material is placed in a glass bottle, and a magnetic stir bar and excess N-methylpyrrolidone (NMP) solvent are added. The amount of NMP added is not less than 2 / 3 of the glass bottle volume, and the mixture is stirred at 300 r / min for 12 h to obtain a mixed solution. The purpose of pre-grinding is to initially mix the two cathode materials, and the purpose of magnetic stirring in NMP solvent is to ensure more thorough contact between the two cathode materials.

[0026] Furthermore, vacuum drying thoroughly removes the solvent through gradient temperature control, providing dry particles with high surface energy for subsequent ball milling, which is beneficial for the full release of the active material's capacity. Specifically, the vacuum drying temperature is 60–120°C, the vacuum degree is -0.1–-0.5 MPa, and the drying time is 12–20 h. The purpose of vacuum drying is to remove excess NMP solvent. In this embodiment, the mixed solution is placed in a vacuum drying oven and dried at a vacuum degree of -0.1 MPa and a temperature of 100°C for 16 h to completely remove the NMP solvent. This step maintains a highly active particle surface, providing favorable conditions for subsequent anchoring and yielding pretreated material.

[0027] The gradient high-energy ball mill uses an alternating forward and reverse rotation method, with the preset speed gradient increasing and then decreasing sequentially to form at least one speed-up and speed-down cycle; Gradient high-energy ball milling includes low-speed, medium-speed, and high-speed sections. The low-speed section is used to initially wet and homogenize the spatial distribution of the material. The medium-speed section provides moderate shear force to help nano-manganese iron phosphate overcome electrostatic agglomeration and distribute evenly to the surface of micron-sized lithium cobalt oxide particles. The high-speed section provides instantaneous high energy to induce mechanochemical effects, anchoring the lithium manganese iron phosphate particles to the surface of the lithium cobalt oxide particles and forming a discontinuous protective interface.

[0028] Furthermore, the rotational speed range of the gradient high-energy ball mill is 500–1500 r / min. Through experimental screening, it was determined that when the rotational speed gradient is 100–500 r / min (preferably 200 r / min), it can ensure the uniform dispersion of nanoparticles while avoiding excessive breakage.

[0029] In gradient high-energy ball milling, the rotation speed in the low-speed section is 500–700 r / min, the rotation speed in the medium-speed section is 800–900 r / min, and the rotation speed in the high-speed section is 1000–1200 r / min. The single ball milling time is 10–12 min, and the number of speed-up and speed-down cycles is 1–4.

[0030] During gradient high-energy ball milling, the material temperature is controlled between 60 and 80°C, and the milling process is carried out under vacuum conditions, with rotation alternating between self-rotation and revolution. The purpose of gradient high-energy ball milling is to homogenize the mixture and simultaneously provide mechanical activation, making it more uniform and ensuring more thorough contact.

[0031] In this embodiment, the pretreated material is placed in a ball mill jar and subjected to gradient high-energy ball milling using alternating forward and reverse rotation (alternating rotation and revolution). The specific process is as follows: Low speed range: ball mill at 600 r / min for 10 min; Medium speed range: ball mill at 900 r / min for 10 min; High-speed section: ball mill at 1200 r / min for 10 min; Medium speed range: ball mill at 900 r / min for 10 min; Low speed section: ball mill at 600 r / min for 10 min; The above-mentioned speed gradient is completed in sequence as one acceleration and deceleration cycle, and a total of 3 cycles are performed. The ball milling process is maintained in a high vacuum state throughout, and the material temperature is controlled at 60~80℃ to obtain a premixed material.

[0032] Furthermore, the gradient micron mesh sieving step dynamically removes fine agglomerates that may be generated during ball milling, precisely controlling the diameter of the composite particles within the micron range, thus ensuring the high consistency and edge stability of the mechanochemical blended cathode material during electrode preparation.

[0033] Specifically, the sieve mesh size ranges from 50 to 500 mesh, preferably 100 mesh, resulting in a particle size of 15 to 25 μm for the final mechanochemical blend cathode material. The sieving time for each stage is 10 to 20 minutes. The purpose of using a gradient micron-mesh sieve is to control the particle diameter of the premixed materials within the micron scale, ensuring better consistency in the final mechanochemical blend cathode.

[0034] Through experimental screening, it was determined that the premixed material was sequentially sieved through 50 mesh → 100 mesh → 200 mesh → 500 mesh sieves, with each sieve taking 15 minutes and a total sieve time of 60 minutes. This method not only removed agglomerates that might be generated during ball milling but also ensured that the particle size was controlled within a suitable range of 15–25 μm. A mechanochemical blended cathode material with uniform particle size distribution was obtained, denoted as LCO-3 (LCO:LFMP = 3:7).

[0035] Battery assembly and testing: A positive electrode sheet was prepared using a mechanical-chemical blend of LCO-3 (80:10:10 by mass), polyvinylidene fluoride (PVDF), and conductive carbon black (Super P) as raw materials, and NMP as solvent. A CR2025 coin cell was assembled using commercially available polypropylene (PP) as the separator, lithium foil as the negative electrode, and commercially available ethylene carbonate (EC) electrolyte in the following order: negative electrode shell, gasket, positive electrode sheet, separator, electrolyte, lithium foil, gasket, spring contact, and positive electrode shell. The assembled cells were then pressed using a pressing machine. The prepared coin cells were allowed to stand overnight at room temperature for 20 hours, and their electrochemical performance was tested using a Blue Electric testing system. The test voltage range was 3.0–4.45 V.

[0036] Performance results: like Figure 2As shown, the LCO-3 mechanochemical blend cathode material exhibits excellent electrochemical performance, with a capacity retention of 74% after 200 cycles. Example 2: The present invention also provides a lithium battery mechanochemical blend cathode material, which can be realized by performing the process steps of the preparation method of lithium battery mechanochemical blend cathode material. That is, those skilled in the art can understand the preparation method of lithium battery mechanochemical blend cathode material as the preferred embodiment of lithium battery mechanochemical blend cathode material.

[0037] Specifically, the lithium-ion battery mechanochemical blended cathode material consists of layered, high-capacity micron-sized lithium cobalt oxide particles and olivine-type, highly stable nano-sized lithium manganese iron phosphate particles. The nano-sized lithium manganese iron phosphate particles are anchored to the surface of the micron-sized lithium cobalt oxide particles through mechanochemical action, forming a discontinuous protective interface. This anchoring structure achieves effective isolation of active materials at the microscale. Utilizing the excellent thermal stability and structural rigidity of lithium manganese iron phosphate, it significantly suppresses interfacial side reactions between lithium cobalt oxide and the electrolyte during high-voltage cycling, effectively improving the structural stability and cycle life of the cathode material.

[0038] Furthermore, the particle size of lithium cobalt oxide particles is 5–30 μm, and the particle size of lithium manganese iron phosphate particles is 80–500 nm; based on a total weight of 10 parts, lithium cobalt oxide accounts for 3–7 parts, and lithium manganese iron phosphate accounts for 7–3 parts in the mechanical and chemical blended cathode material for lithium batteries.

[0039] Furthermore, the mechanical-chemical blended cathode material for lithium batteries is used in lithium batteries operating at 3.0–4.45 V, with a theoretical specific capacity of 170–175 mAh / g.

[0040] Example 3: The only difference between this embodiment and Embodiment 1 is that: During wet mixing, the mass ratio of LCO to LFMP is 5:5. The remaining steps (wet mixing parameters, vacuum drying parameters, gradient high-energy ball milling parameters, gradient micron mesh sieving parameters) are the same as in Example 1, and the resulting mechanochemical blended cathode material is denoted as LCO-5 (LCO:LFMP=5:5).

[0041] The battery assembly and testing methods are the same as in Example 1.

[0042] Performance results: like Figure 3 and Figure 4As shown, the LCO-5 mechanochemical blend cathode material exhibits good mixing effect and excellent electrochemical performance. Lithium manganese iron phosphate particles are anchored on the surface of lithium cobalt oxide particles, forming a discontinuous protective interface. After 500 stable cycles, the capacity retention rate is 94%.

[0043] Example 4: The only difference between this embodiment and Embodiment 1 is that: During wet mixing, the mass ratio of LCO to LFMP was 7:3. All other steps were the same as in Example 1, and the resulting mechanochemical blended cathode material was designated LCO-7 (LCO:LFMP = 7:3). Battery assembly and testing methods were the same as in Example 1.

[0044] Performance results: like Figure 5 As shown, the capacity retention rate of the LCO-7 mechanochemical blend cathode material was 75% after 90 cycles, indicating that the interfacial stability was insufficient due to the unsuitable mechanochemical mixing ratio.

[0045] Comparative Example 1: The only difference between this embodiment and Embodiment 1 is that: During wet mixing, only LCO was used, and LFMP was not added. The remaining wet mixing, vacuum drying, gradient high-energy ball milling, and gradient micron-mesh sieving steps were the same as in Example 1, and the resulting material was denoted as LCO cathode material.

[0046] The battery assembly and testing methods are the same as in Example 1.

[0047] Performance results: like Figure 6 As shown, the LCO cathode material exhibits a high discharge capacity, reaching 168 mAh / g in the first cycle. However, its cycling performance is not ideal, with a capacity retention of only 78% after 100 cycles. This indicates that its cycling performance still needs further improvement.

[0048] Comparative Example 2 The only difference between this embodiment and Embodiment 1 is that: During wet mixing, only LFMP is used, and LCO is not added. The remaining steps are the same as in Example 1, and the resulting material is referred to as LFMP cathode material.

[0049] The battery assembly and testing methods are the same as in Example 1.

[0050] Performance results: like Figure 7 As shown, the LFMP cathode material retains 86% of its capacity after 200 cycles. However, its discharge capacity is only 100~110 mAh / g, which is attributed to its insufficient intrinsic conductivity and lithium-ion transport rate.

[0051] Comparative Example 3: The only difference between this embodiment and Embodiment 1 is that: The material was ball-milled at a constant speed of 900 r / min for 150 min without gradient speed increase. The remaining steps were the same as in Example 1, and the resulting mechanochemical blend cathode material was designated LCO / LFMP-3-C.

[0052] The battery assembly and testing methods are the same as in Example 1.

[0053] Performance results: like Figure 8 The LCO / LFMP-3-C cycle, as shown, exhibited a capacity retention of only 65% ​​after 200 cycles, indicating insufficient interfacial stability in the hybrid cathode material prepared using conventional processes, resulting in poor electrochemical performance. Therefore, high-energy ball milling with varying speeds is an effective method to achieve uniform anchoring of nanoparticles on the surface of micron-sized particles.

[0054] like Figure 2 As shown in the figure, the performance comparison summary is as follows.

[0055] As can be seen from the above results, the present invention has successfully achieved the anchoring of nano-sized lithium manganese iron phosphate on the surface of micron-sized lithium cobalt oxide through gradient high-energy ball milling process. While maintaining a high specific capacity, it has significantly improved cycle stability and is superior to conventional ball milling mixing methods.

[0056] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0057] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for preparing a lithium battery mechanochemical blended cathode material, characterized in that, Includes the following steps: Micron-sized lithium cobalt oxide particles and nano-sized lithium manganese iron phosphate particles are wet-mixed, vacuum-dried, and then subjected to gradient high-energy ball milling to obtain a mechanochemical blended cathode material. The gradient high-energy ball mill adopts an alternating forward and reverse method, with the preset speed gradient first increasing and then decreasing sequentially to form at least one speed-up and speed-down cycle; The gradient high-energy ball mill includes a low-speed section, a medium-speed section, and a high-speed section. The low-speed section is used to initially mix the two materials evenly. The medium-speed section is used to evenly distribute nano-sized lithium manganese iron phosphate particles onto the surface of micron-sized lithium cobalt oxide particles. The high-speed section is used to anchor the lithium manganese iron phosphate particles onto the surface of the lithium cobalt oxide particles through mechanochemical action, forming a discontinuous protective interface.

2. The method for preparing the lithium battery mechanochemical blended cathode material according to claim 1, characterized in that, The wet mixing process includes: weighing and pre-grinding lithium cobalt oxide particles and lithium manganese iron phosphate particles according to the mixing ratio, and then mixing them in an organic solvent, wherein the organic solvent is N-methylpyrrolidone, the stirring speed is 200-700 r / min, and the stirring time is 10-14 h.

3. The method for preparing the lithium battery mechanochemical blended cathode material according to claim 1, characterized in that, The vacuum drying temperature is 60–120°C, the vacuum degree is -0.1–-0.5 MPa, and the drying time is 12–20 h.

4. The method for preparing the lithium battery mechanochemical blended cathode material according to claim 1, characterized in that, The rotational speed range of the gradient high-energy ball mill is 500–1500 r / min, and the rotational speed gradient is 100–500 r / min.

5. The method for preparing the lithium battery mechanical-chemical blended cathode material according to claim 2, characterized in that, In the gradient high-energy ball milling, the rotation speed in the low-speed section is 500-700 r / min, the rotation speed in the medium-speed section is 800-900 r / min, the rotation speed in the high-speed section is 1000-1200 r / min, the single ball milling time is 10-12 min, and the number of speed-up and speed-down cycles is 1-4.

6. The method for preparing the lithium battery mechanochemical blended cathode material according to claim 1, characterized in that, During the gradient high-energy ball milling process, the material temperature is controlled at 60-80℃, the ball milling process is carried out under vacuum conditions, and the rotation mode is alternating between rotation and revolution.

7. The method for preparing the lithium battery mechanochemical blended cathode material according to claim 1, characterized in that, Following the gradient high-energy ball milling, a gradient micron-mesh sieving step is also included, in which sieves with increasing mesh sizes are used for grading and screening, with the mesh size range being 50 to 500 mesh, ultimately yielding a mechanochemical blended cathode material with a particle size of 15 to 25 μm. Each sieving stage takes 10 to 20 minutes.

8. A lithium battery mechanochemical blended cathode material obtained by the preparation method of the lithium battery mechanochemical blended cathode material according to any one of claims 1-7, characterized in that, The lithium battery mechanochemical blend cathode material is composed of micron-sized lithium cobalt oxide particles and nano-sized lithium manganese iron phosphate particles. The nano-sized lithium manganese iron phosphate particles are anchored to the surface of the micron-sized lithium cobalt oxide particles through mechanochemical action, forming a discontinuous protective interface.

9. The lithium battery mechanochemical blend cathode material according to claim 8, characterized in that, The lithium cobalt oxide particles have a particle size of 5–30 μm, and the lithium manganese iron phosphate particles have a particle size of 80–500 nm; based on a total weight of 10 parts, the lithium battery mechanical-chemical blended cathode material contains 3–7 parts of lithium cobalt oxide and 7–3 parts of lithium manganese iron phosphate.

10. The lithium battery mechanochemical blend cathode material according to claim 8, characterized in that, The aforementioned lithium battery mechanical-chemical blended cathode material is used in lithium batteries operating at 3.0–4.45 V, with a theoretical specific capacity of 170–175 mAh / g.

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