High-performance composite positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the field of battery materials, and discloses a high-performance composite positive electrode material and a preparation method and application thereof.The preparation method of the high-performance composite positive electrode material comprises the steps that an MOF material and a flaky conductive carbon material are mixed through ball milling, then a solid electrolyte material is added for continuous ball milling, then the positive electrode material is added for continuous ball milling, roasting is conducted in the inert atmosphere, and the high-performance composite positive electrode material is obtained. Obtaining a finished product. An electron-ion-active material interpenetrating structure is formed by the MOF material, the sheet-shaped conductive carbon material and the solid electrolyte material, so that the interface contact can be improved, the stability of the composite positive electrode can be improved, the cycle life of the battery can be remarkably prolonged, and the requirements of the long-cycle-life solid-state lithium metal battery can be met.

Description

Technical Field

[0001] This invention belongs to the field of battery materials, and relates to a cathode material, specifically a high-performance composite cathode material and its preparation method and application. Background Technology

[0002] With the surge in demand for high-energy-density and high-safety batteries from fields such as new energy vehicles and energy storage power stations, traditional liquid lithium-ion batteries are struggling to meet the development requirements of next-generation energy storage technologies due to issues such as electrolyte leakage and thermal runaway risks. Solid-state lithium batteries, which replace liquid electrolytes with solid electrolytes, have become a research hotspot for next-generation energy storage devices due to their advantages such as high energy density and high safety.

[0003] As a core component of solid-state batteries, composite cathodes must simultaneously meet requirements for electron conduction, ion transport, and interface stability. Currently, traditional composite cathodes suffer from the following problems: high interfacial reactivity between the solid electrolyte (such as sulfide Li6PS5Cl) and the ternary high-nickel NCM active material of the cathode, easily generating high-resistivity byproducts, leading to a decline in cycle performance; uneven dispersion of electronic conductors (such as carbon materials) and ion conductors (such as solid electrolytes), blocking electron-ion transport pathways; and low mechanical strength of the composite system, leading to structural collapse due to the volume expansion of the active material during charge and discharge, further exacerbating performance degradation and affecting the electrochemical performance of the battery. Summary of the Invention

[0004] In view of the defects and deficiencies of the existing technology, the present invention provides, firstly, a method for preparing a high-performance composite cathode material; secondly, a high-performance composite cathode material; and thirdly, a battery.

[0005] In a first aspect, the present invention provides a method for preparing a high-performance composite cathode material, comprising the following steps: Step 1: Ball milling is used to mix MOF material and sheet-like conductive carbon material to obtain the first material; Step 2: Ball mill the solid electrolyte material and the first material to obtain the second material; Step 3: Ball milling is used to mix the second material and the cathode material to obtain an intermediate product; Step 4: Calcining the intermediate product in an inert atmosphere to obtain the high-performance composite cathode material.

[0006] Preferably, in step 1, the MOF material is any one or both of ZIF-8 and Zr-MOF.

[0007] Preferably, in step 1, the sheet-like conductive carbon material is any one or more of flake graphite, expanded graphite sheets, and graphene sheets.

[0008] Preferably, in the first material obtained in step 1, the mass ratio of MOF material to sheet-like conductive carbon material is 7:(2-4).

[0009] Preferably, in step 1, the ball milling speed is 200-300 rpm and the ball milling time is 2-3 hours.

[0010] Preferably, in the second material obtained in step 2, the mass ratio of the solid electrolyte to the first material is (1-2):1.

[0011] Preferably, in step 2, the ball milling speed is 200-300 rpm and the ball milling time is 4-5 h.

[0012] Preferably, in step 2, the solid electrolyte material is LPSC (Li6PS5Cl) or LGPS (Li 10 GeP2S 12 It can be any one or more of LIC (Li3InCl3) and LZC (Li2ZrCl6).

[0013] Preferably, in step 2, the particle size of the solid electrolyte is 100-500 nm.

[0014] Preferably, in step 3, the cathode material is LiNi. x Co y Mn 1-x-y O2, 0.8≤x<1, 0.08≤y≤0.12.

[0015] Preferably, in step 3, the mass ratio of the positive electrode material to the second material is (60%-85%):(15%-40%).

[0016] Preferably, in step 3, the ball milling speed is 150-200 rpm and the ball milling time is 30-60 min.

[0017] Preferably, in step 4, the calcination temperature is 300-400℃ and the calcination time is 1-3h.

[0018] Secondly, the present invention provides a high-performance composite cathode material, which is prepared by the above-described preparation method.

[0019] Preferably, the material comprises a positive electrode material and a second material, wherein the positive electrode material and the second material are uniformly distributed; the chemical formula of the positive electrode material is LiNi. x Co y Mn 1-x-y O2, 0.8≤x<1, 0.08≤y≤0.12, the second material includes MOF material, sheet-like conductive carbon material and solid electrolyte material.

[0020] Thirdly, the present invention provides a battery comprising a high-performance composite cathode material prepared by the preparation method described in the first aspect.

[0021] Compared with the prior art, the present invention has the following significant advantages: (1) The present invention adopts a stepwise composite ball milling process. First, MOF material ZIF-8 and conductive carbon are pre-ball milled and composited to construct a homogeneous and dense ZIF-8-conductive carbon composite matrix. A continuous and uniformly distributed electronic conduction network is built inside the matrix. Then, Li6PS5Cl solid electrolyte is introduced through secondary ball milling, which allows the solid electrolyte particles to be fully dispersed and uniformly embedded in the formed ZIF-8-conductive carbon matrix. After being composited with NCM active material, a three-dimensional interpenetrating structure in which active material, electronic conduction pathway and ion transport pathway are intertwined can be formed, which can effectively optimize the interface contact effect, enhance the overall conductivity and ion conduction ability, improve the stability of composite cathode structure, and significantly extend the battery cycle life, which can meet the use requirements of long-cycle solid lithium metal batteries.

[0022] (2) This invention provides a low-cost and easy-to-operate method for preparing composite electrode materials. This composite cathode with an interpenetrating electron-ion-active material structure has broad application prospects. Attached Figure Description

[0023] Figure 1 The graph shows the cycle performance of batteries assembled from the cathode materials obtained in Examples 1-4 and Comparative Examples 1-5. Detailed Implementation

[0024] The present invention provides the following specific technical solutions.

[0025] In a first aspect, the present invention provides a method for preparing a high-performance composite cathode material, comprising the following steps: Step 1: Ball milling and mixing MOF material 1 and sheet-like conductive carbon material to obtain the first material; Step 2: Ball mill the solid electrolyte material and the first material to obtain the second material; Step 3: Ball milling is used to mix the second material and the cathode material to obtain an intermediate product; Step 4: Calcining the intermediate product in an inert atmosphere to obtain the high-performance composite cathode material.

[0026] Research has revealed that the synergistic effect of MOF materials and sheet-like conductive carbon materials can compensate for the performance shortcomings of solid electrolyte matrices. The porous channels of MOF materials can construct efficient ion transport pathways and enhance the electrochemical stability of the matrix. Sheet-like conductive carbon materials can build continuous conductive networks to improve electron conduction efficiency and can also counteract volume deformation of the matrix during charging and discharging through bridging. Solid electrolytes themselves possess excellent lithium-ion / metal-ion conduction properties, providing a basic channel for ion migration. Combined with the porous ion transport pathways of MOF materials, this forms a multi-level ion conduction network, significantly improving the overall ion transport efficiency. To improve electron transport efficiency, MOF material ZIF-8 is first ball-milled and composited with conductive carbon to construct a homogeneous and dense ZIF-8-conductive carbon composite matrix, in which a continuous and uniformly distributed electron conduction network is built. Then, Li6PS5Cl solid electrolyte is introduced through secondary ball milling, which allows the solid electrolyte particles to be fully dispersed and uniformly embedded in the formed ZIF-8-conductive carbon matrix. The three components complement the performance shortcomings of a single system, achieving efficient electron-ion conduction in the composite cathode and enhancing the structural stability, interfacial stability, and electrochemical cycle stability of the cathode material.

[0027] Preferably, in step 1, the MOF material is any one or both of ZIF-8 and Zr-MOF.

[0028] Preferably, in step 1, the sheet-like conductive carbon material is any one or more of flake graphite, expanded graphite sheets, and graphene sheets.

[0029] Preferably, in the first material obtained in step 1, the mass ratio of MOF material to sheet-like conductive carbon material is 7:(2-4).

[0030] Research has revealed that, under the aforementioned optimized ratio, MOF and conductive carbon exhibit significant synergistic effects. A higher proportion of MOF forms a dense protective layer, ensuring ion transport through its porous structure; while conductive carbon constructs a highly efficient conductive network, compensating for the insufficient conductivity of MOF. This well-matched ratio reduces interfacial impedance, improves battery rate and cycle performance, enhances the mechanical strength of the cathode material, reduces matrix structural damage, and ensures stable battery operation.

[0031] Preferably, in step 1, the ball milling speed is 200-300 rpm and the ball milling time is 2-3 hours.

[0032] Preferably, in the second material obtained in step 2, the mass ratio of the solid electrolyte to the first material is (1-2):1.

[0033] Research has shown that a suitable ratio between the solid electrolyte and the first material ensures sufficient electrolyte content to guarantee ion transport efficiency, while allowing the MOF and conductive carbon to fully exert their functions of stabilizing the interface, improving conductivity, and enhancing mechanical strength. The appropriate dosage of each component avoids excess or deficiency of any single component, resulting in the second material possessing both excellent electrochemical performance and structural stability, thus meeting the high-efficiency operation requirements of the battery.

[0034] Preferably, in step 2, the ball milling speed is 200-300 rpm and the ball milling time is 4-5 h.

[0035] Preferably, in step 2, the solid electrolyte material is LPSC (Li6PS5Cl) or LGPS (Li 10 GeP2S 12 It can be any one or more of LIC (Li3InCl3) and LZC (Li2ZrCl6).

[0036] Preferably, in step 2, the particle size of the solid electrolyte is 100-500 nm.

[0037] Preferably, in step 3, the cathode material is LiNi. x Co y Mn 1-x-y O2, 0.8≤x<1, 0.08≤y≤0.12.

[0038] Preferably, in step 3, the mass ratio of the positive electrode material to the second material is (60%-85%):(15%-40%).

[0039] Research has shown that within the above-mentioned preferred range, the core capacity advantage of high-nickel cathode materials can be retained, the required amount of solid electrolyte for all-solid-state batteries can be met to achieve efficient lithium conduction, and the synergistic effect of MOF and conductive carbon can be used to enhance electron conduction and structural stability, ultimately achieving a performance balance and efficient compatibility between active materials and functional auxiliary materials.

[0040] Preferably, in step 3, the ball milling speed is 150-200 rpm and the ball milling time is 30-60 min.

[0041] Preferably, in step 4, the calcination temperature is 300-400℃ and the calcination time is 1-3h.

[0042] Preferably, the preparation method of MOF material includes: mixing Zn(NO3)2·6H2O methanol solution and C4H6N2 methanol solution, stirring the reaction at room temperature, washing the resulting white precipitate with methanol solution multiple times, and drying to obtain MOF material.

[0043] In practical applications, MOF materials can be prepared using the methods described above, or commercially available MOF materials can be used.

[0044] Secondly, the present invention provides a high-performance composite cathode material, which is prepared by the above-described preparation method.

[0045] Research has revealed that the NCM cathode core ensures a high capacity foundation, while the shell composed of MOF materials, sheet-like conductive carbon materials, and solid electrolyte materials works synergistically. The MOF material stabilizes the interface, inhibits transition metal dissolution, and promotes ion transport; the sheet-like conductive carbon material enhances conductivity and mechanical strength; and the electrolyte ensures ion conduction. The combination of these three significantly reduces interfacial impedance, improves battery rate performance and cycle stability, and achieves both high energy density and safety.

[0046] Preferably, the material comprises a positive electrode material and a second material, wherein the positive electrode material and the second material are uniformly distributed; the chemical formula of the positive electrode material is LiNi. x Co y Mn 1-x-y O2, 0.8≤x<1, 0.08≤y≤0.12, the second material includes MOF material, sheet-like conductive carbon material and solid electrolyte material.

[0047] Thirdly, the present invention provides a battery comprising the above-described high-performance composite cathode material or the high-performance composite cathode material prepared by the above-described preparation method.

[0048] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0049] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0050] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0051] In a specific embodiment of this invention, the MOF material used is ZIF-8. The preparation steps include: adding 0.7437g of Zn(NO3)2·6H2O and 17.020g of C4H6N2 to 10mL and 90mL of CH3OH solution, respectively, and placing them on a magnetic stirrer. Stirring at 300rpm for 30min until completely dissolved, resulting in clear and transparent CH3OH solutions of Zn(NO3)2·6H2O and C4H6N2. The CH3OH solution of Zn(NO3)2·6H2O is added to the CH3OH solution of C4H6N2, and the mixture is stirred at room temperature for 24h. The reaction solution is then transferred to a centrifuge for centrifugation at 8000rpm for 10min, yielding a white precipitate. This precipitate is washed five times with CH3OH solution and finally dried in a 60℃ oven to obtain the ZIF-8 material.

[0052] Example 1: A method for preparing a high-performance composite cathode material includes the following steps: Step 1: Add Li6PS5Cl to a ball mill jar and ball mill it for 5 hours at a speed of 400 rpm. The ball mill beads are 10 mm in diameter and the material-to-ball ratio (mass ratio) is 1:15 to obtain Li6PS5Cl with a particle size of 100-500 nm.

[0053] Step 2: Take 70mg ZIF-8 and 30mg flake graphite and ball mill them together at 300rpm for 3h to obtain ZIF-8-conductive carbon; then add 100mg Li6PS5Cl obtained in step 1 and continue ball milling at 300rpm for 4h to form the second material.

[0054] Step 3: Take 30 mg of the second material obtained in Step 2 and 70 mg of commercial LiNi 0.8 Co 0.1 Mn 0.1 O2 ball milling was used to mix the products at a speed of 150 rpm for 30 minutes to obtain an intermediate product.

[0055] Step 4: The intermediate product is calcined at 350°C for 2 hours under an argon atmosphere. The resulting solid particles are the high-performance composite cathode material.

[0056] Example 2: A method for preparing a high-performance composite cathode material includes the following steps: Step 1, Li 10 GeP2S 12The material was added to a ball mill jar and ball-milled for 6 hours at a speed of 400 rpm. The ball beads were 10 mm in diameter, and the material-to-ball ratio (mass ratio) was 1:20, resulting in Li particles with a particle size of 100-500 nm. 10 GeP2S 12 .

[0057] Step 2: Mix 70 mg ZIF-8 with 20 mg expanded graphite sheets, ball mill at 300 rpm for 3 hours to obtain ZIF-8-conductive carbon; then add 100 mg of Li obtained in Step 1. 10 GeP2S 12 Continue ball milling at 300 rpm for 4 hours to form the second material.

[0058] Step 3: Take 25 mg of the second material obtained in Step 2 and 75 mg of commercial LiNi 0.8 Co 0.1 Mn 0.1 O2 ball milling was used to mix the products. The ball milling speed was 150 rpm and the ball milling time was 45 min to obtain the intermediate product.

[0059] Step 4: The intermediate product is calcined at 300°C for 3 hours under an argon atmosphere. The resulting solid particles are the high-performance composite cathode material.

[0060] Example 3: A method for preparing a high-performance composite cathode material includes the following steps: Step 1: Add Li3InCl3 to a ball mill jar and ball mill it for 6 hours at a speed of 400 rpm. The ball mill beads are 10 mm in diameter and the material-to-ball ratio (mass ratio) is 1:20 to obtain Li3InCl3 with a particle size of 100-500 nm.

[0061] Step 2: Take 70mg ZIF-8 and 40mg graphene sheet and ball mill them together at 300rpm for 3h to obtain ZIF-8-conductive carbon; then add 110mg Li3InCl3 obtained in step 1 and continue ball milling at 300rpm for 4h to form the second material.

[0062] Step 3: Take 20 mg of the second material obtained in Step 2 and 80 mg of commercial LiNi 0.8 Co 0.1 Mn 0.1 O2 ball milling was used to mix the products at a speed of 150 rpm for 60 min to obtain an intermediate product.

[0063] Step 4: The intermediate product is calcined at 400°C for 1 hour under an argon atmosphere. The resulting solid particles are the high-performance composite cathode material.

[0064] Example 4: A method for preparing a high-performance composite cathode material includes the following steps: Step 1: Add Li2ZrCl6 to a ball mill jar and ball mill it for 6 hours at a speed of 400 rpm. The ball mill beads are 10 mm in diameter and the material-to-ball ratio (mass ratio) is 1:20 to obtain Li2ZrCl6 with a particle size of 100-500 nm.

[0065] Step 2: Mix 70mg ZIF-8 with 30mg graphene sheets in a ball mill at 300rpm for 3h to obtain ZIF-8-conductive carbon; then add 200mg Li2ZrCl6 obtained in Step 1 and continue ball milling at 300rpm for 4h to form the second material.

[0066] Step 3: Take 15 mg of the second material obtained in Step 2 and 85 mg of commercial LiNi 0.8 Co 0.1 Mn 0.1 O2 ball milling was used to mix the products. The ball milling speed was 200 rpm and the ball milling time was 60 min to obtain the intermediate product.

[0067] Step 4: The intermediate product is calcined at 380°C for 2 hours under an argon atmosphere. The resulting solid particles are the high-performance composite cathode material.

[0068] Comparative Example 1: A method for preparing a composite positive electrode includes the following steps: Step 1: Add Li6PS5Cl to a ball mill jar and ball mill it for 5 hours at a speed of 400 rpm. The ball mill beads are 10 mm in diameter and the material-to-ball ratio (mass ratio) is 1:15 to obtain Li6PS5Cl with a particle size of 100-500 nm.

[0069] Step 2: Take 30mg of conductive carbon and 100mg of Li6PS5Cl obtained in Step 1 and ball mill them at a speed of 300rpm for 4h to form the second material.

[0070] Step 3: Take 30 mg of the second material obtained in Step 2 and 70 mg of commercial LiNi 0.8 Co 0.1 Mn 0.1 O2 ball milling was used to mix the products at a speed of 150 rpm for 30 minutes to obtain an intermediate product.

[0071] Step 4: The intermediate product is calcined at 350°C for 2 hours under an argon atmosphere. The resulting solid particles are the composite cathode material.

[0072] Comparative Example 2: A method for preparing a composite positive electrode includes the following steps: Step 1: Add Li6PS5Cl to a ball mill jar and ball mill it for 5 hours at a speed of 400 rpm. The ball mill beads are 10 mm in diameter and the material-to-ball ratio (mass ratio) is 1:15 to obtain Li6PS5Cl with a particle size of 100-500 nm.

[0073] Step 2: Take 70 mg ZIF-8 and 100 mg Li6PS5Cl obtained in Step 1 and ball mill them at a speed of 300 rpm for 4 hours to form the second material with ZIF-8 coated electrolyte.

[0074] Step 3: Take 30 mg of the second material obtained in Step 2 and 70 mg of commercial LiNi 0.8 Co 0.1 Mn 0.1 O2 ball milling was used to mix the products at a speed of 150 rpm for 30 minutes to obtain an intermediate product.

[0075] Step 4: The intermediate product is calcined at 350°C for 2 hours under an argon atmosphere. The resulting solid particles are the composite cathode material.

[0076] Comparative Example 3: A method for preparing a composite positive electrode includes the following steps: Step 1: The Li6PS5Cl was ball-milled in a ball mill jar to obtain Li6PS5Cl with a particle size of 100-500nm. The ball milling time was 5h and the ball milling speed was 400rpm. The ball milling beads were 10mm in diameter and the material-to-ball ratio (mass ratio) was 1:15.

[0077] Step 2: Take 30 mg of Li6PS5Cl obtained in Step 1 and 70 mg of commercial LiNi 0.8 Co 0.1 Mn 0.1 O2 ball milling was used to mix the products at a speed of 150 rpm for 30 minutes to obtain an intermediate product.

[0078] Step 3: The intermediate product is calcined at 350°C for 2 hours under an argon atmosphere. The resulting solid particles are the composite cathode material.

[0079] Comparative Example 4: A method for preparing a composite positive electrode includes the following steps: Step 1, take 30mg ZIF-8 and 70mg commercial LiNi 0.8 Co 0.1 Mn 0.1 O2 ball milling was used to mix the products at a speed of 150 rpm for 30 minutes to obtain an intermediate product.

[0080] Step 2: The intermediate product is calcined at 350°C for 2 hours under an argon atmosphere. The resulting solid particles are the composite cathode material.

[0081] Comparative Example 5: A method for preparing a composite positive electrode includes the following steps: Step 1: Take 30 mg of conductive carbon and 70 mg of commercial LiNi 0.8 Co 0.1 Mn 0.1 O2 ball milling was used to mix the products at a speed of 150 rpm for 30 minutes to obtain an intermediate product.

[0082] Step 2: The intermediate product is calcined at 350°C for 2 hours under an argon atmosphere. The resulting solid particles are the composite cathode material.

[0083] Comparative Example 6: A method for preparing a composite cathode material includes the following steps: Step 1: Add Li6PS5Cl to a ball mill jar and ball mill it for 5 hours at a speed of 400 rpm. The ball mill beads are 10 mm in diameter and the material-to-ball ratio (mass ratio) is 1:15 to obtain Li6PS5Cl with a particle size of 100-500 nm.

[0084] Step 2: Take 70mg ZIF-8, 30mg flakes and 100mg Li6PS5Cl obtained in Step 1 and ball mill them together with graphite. The ball milling speed is 300rpm and the ball milling time is 7h to obtain the second material.

[0085] Step 3: Take 30 mg of the second material obtained in Step 2 and mix it with 70 mg of commercial LiNi0.8Co0.1Mn0.1O2 by ball milling at 150 rpm for 30 min to obtain the intermediate product.

[0086] Step 3: The intermediate product is calcined at 350°C for 2 hours under an argon atmosphere. The resulting solid particles are the composite cathode material.

[0087] The cathode materials obtained in Examples 1-4 and Comparative Examples 1-5 were assembled into batteries using the following methods.

[0088] Assemble the PEek cell mold battery in a glove box filled with argon atmosphere, where the water and oxygen content are both below 0.1 ppm. Take 70 mg of Li6PS5Cl powder and spread it evenly in the designated area of ​​the PEek cell mold. Start the tablet press and apply a pressure of 4t for 30 seconds to press it into a dense electrolyte sheet. Evenly spread 10 mg of composite cathode material on one side of the pressed Li6PS5Cl electrolyte sheet, ensuring that the material coverage area is compatible with the electrolyte sheet. Then apply a pressure of 3t through the tablet press to tightly press the composite cathode and the electrolyte sheet together. Use a punching tool to punch indium foil into a circle with a diameter of 10 mm and lithium foil into a circle with a diameter of 4 mm. First, lay the circular indium foil flat on the other side of the Li6PS5Cl electrolyte sheet where the cathode is not pressed together. Then place the circular lithium foil in the center of the indium foil, ensuring that the lithium foil is aligned with the indium foil and the electrolyte sheet. A pressure of 1t was applied to the overall structure inside the mold, and the layers were pressed and held for a period of time to ensure tight adhesion. After standing for 8 hours, the mold was activated at a current density of 0.1C under a voltage of 2.18-3.68V (LiIn as the reference electrode) and then subjected to cyclic testing at 1C. Figure 1 The graph shows the cycle performance of batteries assembled from the cathode materials obtained in Examples 1-4 and Comparative Examples 1-5.

[0089] Table 1. Electrochemical performance data of batteries assembled from the cathode materials prepared in Examples 1-4 and Comparative Examples 1-5. As shown in Table 1, the present invention utilizes solid electrolytes and ZIF... 8 is first combined with conductive carbon to form a second material, and then combined with the ternary cathode material LiNi 0.8 Co 0.1 Mn 0.1 The high-performance composite cathode material obtained by O2 composite and calcination treatment is significantly better than the comparative example in terms of electrochemical performance.

[0090] Compared with comparative examples that use solid electrolyte alone, ZIF-8 alone, conductive carbon alone, lack ZIF-8, lack conductive carbon synergy, and lack calcination treatment, the cathode material assembled batteries prepared in Examples 1-4 of this invention have higher initial discharge capacity at 0.1C rate. At 1C rate, they not only have excellent initial capacity, but also retain more than 94% of their capacity after 200 cycles. In particular, the capacity retention rates of Examples 1 and 3 are as high as 99.27% ​​and 99.99%, respectively, showing extremely high cycle stability and structural stability.

[0091] In Example 1, ZIF-8 and flake graphite were first ball-milled to construct a uniform ZIF-8-conductive carbon composite matrix. Then, Li6PS5Cl solid electrolyte was introduced stepwise and ball-milled a second time. This allowed the electrolyte particles to be uniformly dispersed and embedded within the composite conductive network, forming a continuous and stable ion-electron transport channel. After subsequent composite calcination with NCM811, the interface bond was tight and there were few side reactions. In contrast, in Comparative Example 6, ZIF-8, flake graphite, and Li6PS5Cl were ball-milled simultaneously and for a long time in one go. This easily caused the ZIF-8 structure to collapse and break, the carbon material and electrolyte to disperse and agglomerate randomly, and the conductive / ion transport network to become disordered and discontinuous, resulting in a significant increase in interface impedance. Therefore, compared with Comparative Example 6, Example 1 has higher initial discharge capacity at 0.1C and 1C, and the capacity retention rate after 200 cycles is significantly better. This fully demonstrates that the stepwise composite and progressive coating dispersion process can significantly optimize the component distribution and interface structure, effectively improving the electrochemical activity and cycle stability of the cathode material.

[0092] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance composite cathode material, characterized in that, Includes the following steps: Step 1: Ball milling is used to mix MOF material and sheet-like conductive carbon material to obtain the first material; Step 2: Ball mill the solid electrolyte material and the first material to obtain the second material; Step 3: Ball milling is used to mix the second material and the cathode material to obtain an intermediate product; Step 4: Calcining the intermediate product in an inert atmosphere to obtain the high-performance composite cathode material.

2. The method for preparing the high-performance composite cathode material as described in claim 1, characterized in that, In step 1, the MOF material is any one or two of ZIF-8 and Zr-MOF; the sheet-like conductive carbon material is any one or more of flake graphite, expanded graphite sheets, and graphene sheets; the ball milling speed is 200-300 rpm, and the ball milling time is 2-3 hours.

3. The method for preparing the high-performance composite cathode material as described in claim 1 or 2, characterized in that, In the first material obtained in step 1, the mass ratio of MOF material to sheet-like conductive carbon material is 7:(2-4).

4. The method for preparing the high-performance composite cathode material as described in claim 1, characterized in that, In step 2, the solid electrolyte material is Li6PS5Cl, Li 10 GeP2S 12 The solid electrolyte has one or more of the following: Li3InCl3, Li2ZrCl6; the particle size of the solid electrolyte is 100-500 nm; the ball milling speed is 200-300 rpm; and the ball milling time is 4-5 h.

5. The method for preparing the high-performance composite cathode material as described in claim 1 or 4, characterized in that, In the second material obtained in step 2, the mass ratio of the solid electrolyte to the first material is (1-2):

1.

6. The method for preparing the high-performance composite cathode material as described in claim 1, characterized in that, In step 3, the cathode material is LiNi. x Co y Mn 1-x-y O2, 0.8≤x<1, 0.08≤y≤0.12; the mass ratio of the positive electrode material and the second material is (60%-85%):(15%-40%); the ball milling speed is 150-200 rpm, and the ball milling time is 30-60 min.

7. The method for preparing the high-performance composite cathode material as described in claim 1, characterized in that, In step 4, the roasting temperature is 300-400℃ and the roasting time is 1-3h.

8. A high-performance composite cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The high-performance composite cathode material as described in claim 8, characterized in that, It includes a positive electrode material and a second material, wherein the positive electrode material and the second material are uniformly distributed; the chemical formula of the positive electrode material is LiNi. x Co y Mn 1-x-y O2, 0.8≤x<1, 0.08≤y≤0.12, the second material includes MOF material, sheet-like conductive carbon material and solid electrolyte material.

10. A battery, characterized in that, Including the high-performance composite cathode material prepared by the preparation method according to any one of claims 1-7.

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