A composite cathode for lithium batteries based on multi-level particle size electrolytes, a preparation method thereof, and applications

Abstract

The present invention discloses a lithium battery composite positive electrode based on a multi-level particle size electrolyte, and its preparation method and application, which relates to the field of lithium battery technology. The method first mixes the positive electrode active material with the coarse sulfide electrolyte powder to obtain a first premix, then mixes the first premix with the fine sulfide electrolyte powder to obtain a second premix, and finally mixes the second premix with a conductive agent to obtain a composite positive electrode material, and the mixing is all performed by intermittent ball milling. This method can make the sulfide electrolytes of different particle sizes more evenly distributed, the coarse powder provides an efficient ion transmission channel, the fine powder optimizes the contact interface, and improves the ionic conductivity and active material utilization rate. At the same time, intermittent ball milling can release energy, avoid the melting and decomposition of the positive electrode material and the distortion of the electrolyte crystal lattice, and effectively improve the performance of the composite positive electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a lithium battery composite positive electrode based on a multi-grade particle size electrolyte, and a preparation method and application thereof. Background Art

[0002] As the next generation of high-energy-density energy storage devices, all-solid-state sulfide lithium batteries theoretically achieve a dual breakthrough in intrinsic safety and energy density by replacing traditional organic electrolytes with non-flammable solid electrolytes. Sulfide solid electrolytes are considered one of the most commercially promising technologies in the field of all-solid-state batteries due to their high ionic conductivity, wide electrochemical window, and good interfacial compatibility with electrode materials. Unlike liquid batteries, solid electrolytes cannot spontaneously fill the pores between the positive and negative electrodes through liquid infiltration. Lithium ion transport relies entirely on solid-solid contact, and in practical applications, they still face the key problem of poor solid-solid contact leading to low ion transport efficiency. Therefore, the positive electrode of an all-solid-state battery must be designed as a composite structure, that is, the active material, sulfide electrolyte, conductive agent, adhesive, etc. are mechanically mixed to form a multiphase composite system. How to optimize and composite the positive electrode process is a difficult problem that needs to be solved urgently.

[0003] Traditional mixing processes can easily lead to agglomeration or uneven distribution of electrolyte particles, and insufficient effective ion transmission paths. During the laboratory research and development stage, the preparation of composite positive electrodes usually relies on mechanical mixing techniques, such as conventional grinding, high-energy ball milling, or high-speed shearing. However, sulfide solid electrolytes are prone to agglomeration due to the strong van der Waals forces between particles. During the grinding or ball milling process, the electrolyte often adheres to the tank wall, resulting in uneven distribution of active substances and electrolytes. To solve this problem, conventional solutions require multiple interruptions in the process to scrape off the electrolyte attached to the tank wall, and to force the mixing uniformity by extending the grinding time. However, such methods lead to high equipment shutdown frequency, a surge in energy consumption, and are prone to damage to the active material structure, making it difficult to adapt to large-scale production needs.

[0004] In addition, the preparation of traditional solid-state battery composite positive electrodes often uses binders (such as PTFE) to ensure the stability of the electrode structure and the contact between the components. However, the binder, as an insulating polymer, forms a dielectric barrier at the active material / electrolyte interface, resulting in a significant increase in the internal impedance of the positive electrode, severely limiting the dynamics of lithium ion cross-interface transmission, and affecting the rate performance; at the same time, the addition of the binder will occupy a certain electrode volume and mass, reduce the proportion of active material, and thus affect the energy density of the battery; therefore, the present invention adopts a binder-free composite positive electrode preparation process that ensures battery performance, which is of great significance to promoting the practical application of all-solid-state sulfide lithium batteries. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a lithium battery composite positive electrode based on a multi-grade particle size electrolyte and a preparation method and application thereof.

[0006] The object of the present invention is achieved through the following technical solutions:

[0007] <First Aspect>

[0008] The present invention provides a method for preparing a composite positive electrode material, comprising the following steps:

[0009] S1, the positive electrode active material and D 50 =5~20μm sulfide electrolyte coarse powder is mixed to obtain a first premix;

[0010] S2, the first premix and D 50 = 0.2~1 μm sulfide electrolyte fine powder is mixed to obtain a second premix;

[0011] S3, mixing the second premix and the conductive agent to obtain a composite positive electrode material;

[0012] The mixing is performed by intermittent ball milling.

[0013] As an embodiment, the intermittent ball milling is performed for 20 to 30 minutes, followed by a pause of 5 to 10 minutes, and repeated 4 to 10 times.

[0014] In some embodiments, the intermittent ball milling is performed by ball milling for 25 minutes, pausing for 5 minutes, and repeating 4 to 8 times.

[0015] As an embodiment, the ball-to-material ratio in the intermittent ball milling is (3~4):1.

[0016] In some embodiments, the ball-to-material ratio in the intermittent ball milling is 4:1.

[0017] As an embodiment, the intermittent ball mill uses zirconia grinding balls.

[0018] As an embodiment, the rotation speed of the intermittent ball mill is 200-400 rpm.

[0019] In some embodiments, the intermittent ball milling has a rotation speed of 200 rpm.

[0020] As an embodiment, the volume ratio of the positive electrode active material and the ball mill jar is 1.5g: 100~500mL.

[0021] In some embodiments, the volume ratio of the positive electrode active material to the ball mill jar is 1.5g:100mL.

[0022] As an embodiment, the positive electrode active material includes one or more of high nickel single crystal ternary material, high nickel polycrystalline ternary material, and lithium cobalt oxide.

[0023] As an embodiment, the positive electrode active material includes one or more of NCM111, NCM424, NCM523, NCM622, NCM811, NCM90, NCM92, and NCM95.

[0024] In some embodiments, the positive electrode active material is NCM92.

[0025] As an embodiment, the sulfide electrolyte includes Li3PS4, Li 5.5 PS 4.5 Cl 1.5 , Li6PS5Br, Li6PS5I or more.

[0026] In some embodiments, the sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 .

[0027] As an embodiment, the conductive agent includes one or more of VGCF, Ketjen Black, and super-P.

[0028] As an embodiment, the mass ratio of coarse powder to fine powder in the sulfide electrolyte is 1: (1~5).

[0029] In some embodiments, the mass ratio of the coarse powder to the fine powder is 1:1.5.

[0030] As an embodiment, the mass ratio of the positive electrode active material to the sulfide electrolyte is (70~90): (10~20).

[0031] In some embodiments, the mass ratio of the positive electrode active material to the sulfide electrolyte is 80:18.

[0032] As an embodiment, the mass ratio of the positive electrode active material to the conductive agent is (70~90): (1~5).

[0033] In some embodiments, the mass ratio of the positive electrode active material to the conductive agent is 80:2.

[0034] <Second Aspect>

[0035] The present invention provides a composite positive electrode material, which is prepared according to the above method.

[0036] <Third Aspect>

[0037] The present invention provides application of the composite cathode material in an all-solid-state lithium battery.

[0038] As an embodiment, the composite positive electrode material is pressed to obtain a positive electrode sheet.

[0039] As an embodiment, the electrolyte sheet in the battery is the same material as the sulfide electrolyte described in the composite positive electrode material.

[0040] As an embodiment, the negative electrode in the battery is a lithium-silicon alloy.

[0041] In some embodiments, the negative electrode is Li 22 Si5 alloy.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] This invention provides a novel method for preparing a solid-state sulfide lithium battery composite cathode. By matching electrolytes of varying particle sizes, the composite cathode performance is enhanced. The composite is made from active material, sulfide electrolyte, and conductive carbon through mechanical ball milling. The addition of conductive carbon improves the composite's electronic conductivity. The addition of sulfide electrolyte provides interparticle contact, improving ion transport from the composite cathode to the cathode / electrolyte interface. This improvement is primarily reflected in the following aspects:

[0044] (1) Multi-level particle size electrolytes synergistically optimize the ion transport network of the composite cathode

[0045] A step-by-step addition process of coarse powder first and then fine powder was adopted to construct a "skeleton support-gap filling" structure. First, the electrolyte with larger particles was pre-coated with the active material through ball milling to provide an efficient ion transmission channel; in the subsequent ball milling, the electrolyte with smaller particles filled the gap between the large-particle electrolyte and the active material, increasing the contact area between the electrolyte and the active material, taking into account both conductive performance and contact area.

[0046] Furthermore, the coarse-to-fine method offers a clear advantage in addressing the problem of ball milling sticking to the wall. Since the coarse powder is mixed with the active material first, the fine powder is less likely to come into contact with the tank wall. Adding the fine powder first, on the other hand, can lead to localized accumulation of fine powder, hindering the even distribution of the coarse powder and thus reducing overall battery performance. Furthermore, the strong adhesion of the fine powder leads to a high sticking rate, hindering production operations.

[0047] Therefore, a step-by-step addition process of coarse powder first and then fine powder is adopted to make the electrolyte particles more evenly distributed. The coarse powder provides an efficient ion transmission channel, and the fine powder optimizes the contact interface, thereby improving the ionic conductivity and active material utilization rate, and the assembled full battery performance is better.

[0048] (2) Synergistic effect of intermittent ball milling process and distributed material addition

[0049] From the perspective of energy control and material performance protection, intermittent ball milling plays a key role. The ball milling process generates energy. If the milling process continues, the energy accumulates, causing the heat energy generated by particle friction to far exceed the material's phase transition threshold. The present invention utilizes intermittent ball milling, which promptly releases the energy generated by the milling process, effectively preventing excessive energy accumulation. This not only prevents the cathode material from melting and decomposing due to excessive energy, but also avoids localized crystal lattice distortion in the sulfide electrolyte due to excessive energy, thereby ensuring the stability of the physical and chemical properties of components such as the cathode active material, electrolyte, and conductive carbon.

[0050] From the perspective of material mixing and transmission network construction, the combination of step-by-step ball milling and intermittent ball milling first ensures the homogeneous distribution of positive electrode active materials, electrolytes and conductive carbon, provides conditions for sufficient contact between particles and constructs an efficient ion-electron transmission network.

[0051] In terms of material compounding and performance improvement, the present invention first ball-mills the sulfide cathode material and electrolyte, then adds a conductive agent for further compounding. This ensures full contact between the cathode active material and the electrolyte, creating a better ion transport channel. The conductive agent is then evenly distributed between the cathode material and the electrolyte, ensuring high electronic conductivity for the composite cathode material.

[0052] (3) Achieving high-performance composite cathode without binder

[0053] This invention achieves the production of a high-performance, binder-free composite cathode through the addition of distributed electrolyte particles and intermittent ball milling. This not only avoids the negative effects of binders, but also simplifies the preparation process and reduces production costs. Furthermore, by eliminating the influence of the binder, the composite cathode can more fully utilize the properties of the active material, significantly improving battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0055] Figure 1 A schematic diagram of the microstructure of the composite cathode material provided by the present invention;

[0056] Figure 2 The first cycle charge and discharge curves of Example 1, Comparative Example 1 and Comparative Example 2 at a rate of 0.1C are shown;

[0057] Figure 3 This is the first cycle charge and discharge curve of Comparative Example 3 at a rate of 0.1C;

[0058] Figure 4 This is the first cycle charge and discharge curve of Comparative Example 4 at a rate of 0.1C;

[0059] Figure 5 This is a comparison chart of the cycle performance of the sulfide solid-state batteries prepared in Example 1 and Comparative Examples 1-2 at a rate of 0.5C. DETAILED DESCRIPTION

[0060] The present invention will be described in detail below with reference to the examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make several adjustments and improvements without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0061] This embodiment provides a method for preparing a composite positive electrode for a lithium battery based on a multi-grade particle size electrolyte. The microstructure of the composite positive electrode material is as follows: Figure 1 As shown in the schematic diagram.

[0062] Example 1

[0063] This embodiment provides a method for preparing a composite positive electrode material, the steps of which are as follows:

[0064] In an argon glove box, 1.6 g NCM92 and 144 mg Li 5.5 PS 4.5 Cl 1.5 Coarse powder (D 50 5μm, ionic conductivity of 10.32mS / cm) were premixed in a mortar, ground for 10 minutes, and then added to a zirconia ball mill with a ball-to-material ratio of 4:1. The ball mill was sealed with insulating tape and intermittently ball milled at 200 rpm for 2 hours (ball milling for 25 minutes, pause for 5 minutes, repeated 4 times). After ball milling, the mixture was transferred to a glove box and the ball-to-material separation was performed to obtain the first premix;

[0065] The first premix and 216 mg of Li 5.5 PS 4.5 Cl 1.5 Fine powder (D 50 500 nm, ionic conductivity of 2.72 mS / cm) were premixed in a mortar, then loaded into a ball mill and sealed ball mill, and intermittently ball milled at 200 rpm for 4 h (ball milling for 25 min, pause for 5 min, repeated 8 times). After ball milling, the mixture was transferred to a glove box and the ball and material were separated to obtain a second premix;

[0066] The second premix and 40 mg of VGCF were premixed in a mortar, then loaded into a ball mill and a sealed ball mill, and intermittently ball milled at a speed of 200 rpm for 2 hours (ball milling for 25 minutes, pause for 5 minutes, repeated 4 times). After ball milling, the mixture was transferred to a glove box for ball-material separation to obtain a composite positive electrode material.

[0067] In this embodiment, before loading the ball mill, 5 mm zirconia beads and a 100 mL zirconia ball mill were dried in a 60° C. oven for 4 h and then transferred into an argon glove box.

[0068] In this embodiment, the water content in the glove box is less than 1 ppm, and the oxygen content is less than 1 ppm.

[0069] In this embodiment, VCGF was purchased from CLUDE, model number VGCF-H.

[0070] Comparative Example 1

[0071] This comparative example provides a method for preparing a composite positive electrode material. Compared with Example 1, only electrolyte powder is added to the prepared composite positive electrode material. The steps are as follows:

[0072] In an argon glove box, 1.6 g NCM92 and 360 mg Li 5.5 PS 4.5 Cl 1.5 Fine powder (D 50 500 nm, ionic conductivity of 2.72 mS / cm) were premixed in a mortar, then loaded into a ball mill, sealed ball mill, and intermittently ball milled at 200 rpm for 6 h (ball milling for 25 min, pause for 5 min, repeated 12 times). After ball milling, the mixture was transferred to a glove box and the ball and material were separated to obtain a premix;

[0073] The premix and 40 mg of VGCF were premixed in a mortar, then loaded into a ball mill and sealed, and intermittently ball milled at 200 rpm for 2 h (ball milling for 25 min, pause for 5 min, repeated 4 times). After ball milling, the mixture was transferred to a glove box for ball-material separation to obtain a composite positive electrode material.

[0074] Comparative Example 2

[0075] This comparative example provides a method for preparing a composite positive electrode material. Compared with Example 1, only coarse electrolyte powder is added to the prepared composite positive electrode material. The steps are as follows:

[0076] In an argon glove box, 1.6 g NCM92 and 360 mg Li 5.5 PS 4.5 Cl 1.5 Coarse powder (D 505μm, ionic conductivity of 10.32mS / cm) were premixed in a mortar, then loaded into a ball mill and sealed ball mill, and intermittently ball milled at 200rpm for 6h (ball milling for 25min, pause for 5min, repeated 12 times). After ball milling, the mixture was transferred to a glove box and the ball and material were separated to obtain a premix;

[0077] The premix and 40 mg of VGCF were premixed in a mortar, then loaded into a ball mill and sealed, and intermittently ball milled at 200 rpm for 2 h (ball milling for 25 min, pause for 5 min, repeated 4 times). After ball milling, the mixture was transferred to a glove box for ball-material separation to obtain a composite positive electrode material.

[0078] Comparative Example 3

[0079] This comparative example provides a method for preparing a composite positive electrode material. Compared with Example 1, the order of adding the coarse electrolyte powder and the fine electrolyte powder in the prepared composite positive electrode material is opposite, and the steps are as follows:

[0080] In an argon glove box, 1.5 g NCM92 and 216 mg Li 5.5 PS 4.5 Cl 1.5 Fine powder (D 50 500 nm, ionic conductivity of 2.72 mS / cm) were premixed in a mortar, ground for 10 min, and then added to a zirconia ball mill with a ball-to-material ratio of 4:1. The ball mill was sealed with insulating tape and intermittently ball milled at 200 rpm for 4 h (ball milling for 25 min, pause for 5 min, repeated 8 times). After ball milling, the mixture was transferred to a glove box and the ball-to-material separation was performed to obtain the first premix;

[0081] The first premix and 144 mg Li 5.5 PS 4.5 Cl 1.5 Coarse powder (D 50 5μm, ionic conductivity of 10.32mS / cm) were premixed in a mortar, then loaded into a ball mill and sealed ball mill, and intermittently ball milled at 200rpm for 2h (ball milling for 25min, pause for 5min, repeated 4 times). After ball milling, the mixture was transferred to a glove box and the ball and material were separated to obtain a second premix;

[0082] The second premix and 40 mg of VGCF were premixed in a mortar, then loaded into a ball mill and a sealed ball mill, and intermittently ball milled at a speed of 200 rpm for 2 hours (ball milling for 25 minutes, pause for 5 minutes, repeated 4 times). After ball milling, the mixture was transferred to a glove box for ball-material separation to obtain a composite positive electrode material.

[0083] Comparative Example 4

[0084] This comparative example provides a method for preparing a composite positive electrode material. Compared with Example 1, continuous ball milling is used in the ball milling process, and the steps are as follows:

[0085] In an argon glove box, 1.6 g NCM92 and 144 mg Li 5.5 PS 4.5 Cl 1.5 Coarse powder (D 50 5 μm, ionic conductivity of 10.32 mS / cm) were premixed in a mortar, ground for 10 min, and then added to a zirconia ball mill with a ball-to-material ratio of 4:1. The ball mill was sealed with insulating tape and ball milled at 200 rpm for 100 min. After ball milling, the mixture was transferred to a glove box and the ball-to-material ratio was separated to obtain a first premix;

[0086] The first premix and 216 mg of Li 5.5 PS 4.5 Cl 1.5 Fine powder (D 50 500 nm, ionic conductivity of 2.72 mS / cm) were premixed in a mortar, then loaded into a ball mill and sealed ball mill, and ball milled at 200 rpm for 200 min. After ball milling, the mixture was transferred to a glove box and the ball and material were separated to obtain a second premix;

[0087] The second premix and 40 mg of VGCF were premixed in a mortar, then loaded into a ball mill and a sealed ball mill, and ball milled at 200 rpm for 100 min. After ball milling, the mixture was transferred to a glove box for ball-material separation to obtain a composite positive electrode material.

[0088] Test Analysis

[0089] Assembling the pressure cell

[0090] In an argon glove box, 100 mg of Li 5.5 PS 4.5 Cl 1.5 Coarse electrolyte powder (particle size 5 μm, ionic conductivity 10.32 mS / cm) was placed in a pressure cell mold with a diameter of 10 mm. The electrolyte powder was flattened by rotating stainless steel columns and pressed into tablets on a tablet press at a pressure of 120 MPa for 2 minutes to obtain electrolyte tablets.

[0091] 20 mg of the composite positive electrode material powder prepared in the above examples or comparative examples was placed on one side of the electrolyte sheet, flattened, and pressed into a sheet at a pressure of 360 MPa for 2 minutes to obtain a positive electrode sheet, and the surface of the sheet was covered with a 10 mm diameter Al foil (85 μm thick) as a positive electrode current collector;

[0092] 12 mg of Li was placed on the other side of the electrolyte sheet. 22 Si5 alloy was used as the negative electrode sheet, and Cu foil (45 μm thick) was set on the negative electrode surface as the negative electrode current collector;

[0093] After the assembly is completed, a pressure of 38 MPa is applied and maintained for 2 minutes to obtain a sulfide all-solid-state lithium-ion battery.

[0094] Test Analysis

[0095] Ionic conductivity:

[0096] The ionic conductivity of the composite cathode materials prepared in each embodiment and comparative example was measured using the electrochemical impedance spectroscopy (EIS). A small amplitude AC voltage (frequency range of 0.1 Hz to 1 MHz) was applied to the material, and the resistance value was obtained by measuring the impedance spectrum (Nyquist plot). , the ionic conductivity of the material is calculated by the formula :

[0097]

[0098] in is the thickness of the test material (measured by a micrometer screw), The cross-sectional area of the test material (related to the battery mold, this material is ).

[0099] Active substance utilization rate ( ) is calculated as:

[0100]

[0101] Theoretical specific capacity is calculated based on the chemical formula of the active material (e.g., the theoretical specific capacity of NCM92 is approximately 275 mAh / g); actual specific capacity is determined through charge-discharge testing. A higher active material utilization rate indicates a better cathode material composite method.

[0102] The calculation formula of wall adhesion rate is:

[0103]

[0104] The initial material mass and the mass of the adhered material are obtained by direct weighing. The lower the wall adhesion rate, the better the ball milling composite effect of the material.

[0105] The ionic conductivity, active material utilization rate, and wall adhesion rate of Example 1 and Comparative Examples 1 to 4 were tested, and the test results are shown in Table 1.

[0106] Table 1

[0107]

[0108] The assembled battery was placed in a 25°C constant temperature and humidity incubator under a constant pressure of 38 MPa using a pressure die. The sulfide all-solid-state lithium-ion battery was tested using a Newway battery testing system (equipment model: CT-4000). The test charge and discharge rates were 0.1C to 0.5C, with a charge and discharge cut-off voltage of 2.5V to 4.3V. The charge and discharge capacities described in this document are the specific capacities calculated for the corresponding active materials.

[0109] Charge / discharge specific capacity (mAh g -1 ) =

[0110] Figures 2 to 4 The first cycle charge and discharge curves of Example 1 and Comparative Examples 1 to 4 at a rate of 0.1C are compared. The voltage change of Example 1 during the charge and discharge process is relatively stable, indicating that the battery capacity is fully utilized, the charge and discharge characteristics are excellent, and the voltage stability is strong. During the first cycle charge and discharge process of Example 1, the first cycle charge specific capacity reaches 266mAh g -1 ; Figure 5 This graph compares the cycling performance of the sulfide solid-state batteries prepared in Example 1 and Comparative Examples 1-2 at a rate of 0.5C. As can be seen, Example 1 maintains a high capacity retention of 89.5% after 200 cycles at a rate of 0.5C. Compared to the four comparative examples, Example 1 exhibits superior capacity retention and voltage stability, maintaining a high and stable voltage across a wider specific capacity range, demonstrating superior battery performance.

[0111] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a composite positive electrode material, characterized in that: The following steps are involved: S1, the positive electrode active material and D 50 =5~20μm sulfide electrolyte coarse powder is mixed to obtain a first premix; S2, the first premix and D 50 = 0.2~1 μm sulfide electrolyte fine powder is mixed to obtain a second premix; S3, mixing the second premix and the conductive agent to obtain a composite positive electrode material; The mixing is performed by intermittent ball milling.

2. The method according to claim 1, characterized in that The positive electrode active material includes one or more of high nickel single crystal ternary material, high nickel polycrystalline ternary material, and lithium cobalt oxide.

3. The method according to claim 1, characterized in that The sulfide electrolyte includes Li3PS4, Li 5.5 PS 4.5 Cl 1.5 , Li6PS5Br, Li6PS5I or more.

4. The method according to claim 1, wherein The conductive agent includes one or more of VGCF, Ketjen Black, and super-P.

5. The method according to claim 1, wherein The mass ratio of coarse powder to fine powder in the sulfide electrolyte is 1: (1-5).

6. The method according to claim 1, characterized in that The mass ratio of the positive electrode active material to the sulfide electrolyte is (70~90): (10~20).

7. The method according to claim 1, characterized in that The mass ratio of the positive electrode active material to the conductive agent is (70~90): (1~5).

8. The method according to any one of claims 1 to 7, characterized in that It also includes one or more of the following technical features: A. The intermittent ball milling process is as follows: milling for 20-30 minutes, pausing for 5-10 minutes, and repeating 4-10 times; B. The ball-to-material ratio in the intermittent ball milling is (3-4): 1; C. The rotation speed of the intermittent ball mill is 200-400 rpm; D. The volume ratio of the positive electrode active material and the ball mill jar is 1.5g:100~500mL.

9. A composite positive electrode material, characterized in that It is prepared according to the method according to any one of claims 1 to 8.

10. Use of the composite cathode material according to claim 9 in an all-solid-state lithium battery.

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