Composite positive electrode material for all-solid-state battery, preparation method and all-solid-state battery

Abstract

The invention discloses a composite positive electrode material for an all-solid-state battery, a preparation method and the all-solid-state battery, and belongs to the technical field of all-solid-state batteries, the composite positive electrode material is composed of positive electrode active material particles and solid electrolyte filled in pore structures in the active material particles, and the solid electrolyte forms an ion conduction path in the active material particles. During preparation, an active substance precursor and a template material which can be sintered, decomposed and disappeared are mixed and subjected to heat treatment to form a porous active substance, and then the porous active substance is filled with the solid electrolyte. According to the all-solid-state battery adopting the positive electrode material, the diffusion speed of ions in active substance particles can be remarkably improved, and meanwhile, the all-solid-state battery has the characteristics of high output power, large capacity and long cycle life, and can meet the use requirements of electric vehicles, unmanned aerial vehicles and other scenes with strict requirements on battery performance.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state battery technology, and in particular to a composite cathode material for all-solid-state batteries, a preparation method thereof, and an all-solid-state battery. Background Technology

[0002] Solid-state batteries, with their advantages of high safety and high energy density, have broad application prospects in the new energy field, and the cathode material is a key component affecting their performance. Traditional solid-state batteries use cathode active materials composed of a mixture of active material particles and solid electrolyte particles. The diffusion rate of lithium ions within the cathode active material depends on the crystal structure of the active material itself, and is generally slower than the interparticle ion migration (interfacial resistance). This slow diffusion problem has become a major factor limiting the output characteristics and capacity performance of solid-state batteries, making it difficult to meet the high-power, high-capacity requirements of electric vehicles, drones, and other scenarios. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a cathode material and an all-solid-state battery, fundamentally improving the internal structure of the cathode active material, significantly increasing the ion diffusion rate within the active material particles, and thus obtaining an all-solid-state battery with both high output power and large capacity characteristics, thereby expanding its application fields. The content of this invention is as follows: The first objective of this invention is to provide a composite cathode material for all-solid-state batteries. The technical point is that it is composed of cathode active material particles and a solid electrolyte in a porous structure formed inside the active material particles, and the solid electrolyte forms an ion conduction pathway within the active material particles.

[0004] The second objective of this invention is to provide a method for manufacturing the composite cathode material for all-solid-state batteries as described in claim 1, the technical point of which is that it includes the following steps: 1) Mix the precursor of the positive electrode active material with a template material that can be decomposed and disappeared after sintering; 2) The mixture of the precursor and template material is subjected to heat treatment at 700-900℃ to decompose and disappear the template material and form a porous structure inside the positive electrode active material; A solid electrolyte is filled into the positive electrode active material that forms a porous structure.

[0005] The third objective of this invention is to provide an all-solid-state battery, the technical point of which is to use the above-mentioned composite cathode material as the cathode.

[0006] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. Traditional cathode materials can only make full use of the surface area of ​​active material particles. This invention constructs a porous structure inside the active material particles and fills it with a solid electrolyte to form a high-speed ion conduction pathway, so that ions can smoothly reach the interior of the active material and release the full capacity of the active material to the maximum extent.

[0007] 2. This composite structure can alleviate the stress on the active material particles during charging and discharging, enhance structural stability, and effectively inhibit performance degradation during long-term charge-discharge cycles.

[0008] Instruction manual illustrations Figure 1 A schematic diagram of Li6P5S1Cl1 particles filling the micropores of porous NCM811. Detailed Implementation

[0009] 1. Composite Cathode Material Structure Design: The composite cathode material of this invention consists of cathode active material particles and a solid electrolyte. The solid electrolyte fills the porous structure formed inside the active material particles, creating an ion conduction pathway within the particles. This structure allows lithium ions to diffuse within the active material particles simultaneously through two pathways: one along the traditional active material crystal structure, and the other through a high-speed conduction pathway of the solid electrolyte penetrating the active material, significantly improving ion diffusion efficiency.

[0010] 2. Preparation of composite cathode materials Preparation of porous active material: A positive electrode active material precursor (such as a nickel-rich layered oxide precursor) and a template material (preferably carbon nanotubes) are selected and mixed at a weight ratio of 1%-5%. The mixture is then heat-treated at 700-900℃. During the heat treatment, the template material decomposes and disappears, ultimately forming a uniform nanoscale porous structure inside the positive electrode active material. The specific surface area of ​​this porous structure is higher than that of the same component active material without a porous structure.

[0011] Solid electrolyte filling: The prepared porous active material is immersed in an organic solvent suspension containing nanoparticles of solid electrolyte (such as Argyrodite-type solid electrolyte Li6P5S1Cl1). Through a combination of ultrasonic treatment and vacuum drying, the solid electrolyte particles are deeply penetrated and completely filled into the micropores inside the active material to obtain a composite cathode material.

[0012] 3. All-solid-state battery assembly Positive electrode preparation: The above-mentioned composite positive electrode material particles are mixed with conductive additives (such as carbon black) and binder polymers and molded into a sheet structure to obtain the positive electrode of the all-solid-state battery.

[0013] Negative electrode preparation: Using conventional processes, if carbon is used as the active material, carbon, solid electrolyte, conductive additives and binders are mixed to form a negative electrode; if lithium metal is used as the active material, lithium foil and current collectors such as copper foil are laminated to form a negative electrode.

[0014] Solid electrolyte film preparation: Solid electrolyte powder, binder (such as SBR, PVDF) and solvent are mixed and stirred to form a slurry. The slurry is cast and coated on a release film, dried and formed into a film. Multiple layers can be stacked to a set thickness as required. Then, it is formed under high pressure by uniaxial or cold pressing isotropic pressing (CIP) equipment to obtain a dense and high-strength solid electrolyte film.

[0015] Battery assembly: The positive electrode, solid electrolyte film, and negative electrode are sequentially stacked and encapsulated in the battery case. After encapsulation, pressure is applied to ensure that each layer is tightly bonded, thus completing the assembly of the all-solid-state battery cell.

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0017] Example 1 1. Material preparation: The positive electrode active material precursor is a nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 (NCM811) precursor, the template material is carbon nanotubes (CNTs), and the solid electrolyte is Argyrodite type Li6P5S1Cl1.

[0018] 2. Preparation of porous active material: CNTs and NCM811 precursor were mixed at a weight ratio of 1%. The mixture was then subjected to calcination heat treatment. After the CNTs decomposed and disappeared, NCM811 particles with a nanoscale porous structure were obtained, with a specific surface area of ​​0.84 m². 2 / g.

[0019] 3. Solid electrolyte filling: Porous NCM811 particles are immersed in an organic solvent suspension containing Li6P5S1Cl1 nanoparticles, followed by ultrasonic treatment and vacuum drying, so that the Li6P5S1Cl1 particles fill the micropores of the porous NCM811. Figure 1 As shown, a composite cathode material was obtained.

[0020] 4. Battery assembly: The composite positive electrode material is mixed with carbon black and binder to form a positive electrode sheet; lithium metal is used as the active material, and lithium foil and copper foil are laminated to form a negative electrode sheet; a Li6P5S1Cl1 solid electrolyte film is prepared according to conventional processes; the positive electrode sheet, solid electrolyte film and negative electrode sheet are stacked, packaged and pressurized in sequence to complete the battery assembly.

[0021] Performance testing: At 25℃, with an input current of 0.5mA / cm 2 The battery was charged and discharged at a current density within a voltage range of 4V-2.5V. The initial discharge capacity (0.1C) was measured to be 162mAh / g, and the capacity retention rate after 10 cycles was 81%. This invention relates to a composite cathode material for all-solid-state batteries, its preparation method, and the all-solid-state battery itself. Example 2 The difference between this embodiment and Embodiment 1 is that the mixing weight ratio of CNT to NCM811 precursor is 3%. After heat treatment at 700-900℃, the specific surface area of ​​the porous NCM811 particles is 0.86m². 2 / g; the battery performance test showed an initial discharge capacity (0.1C) of 164mAh / g, and a capacity retention rate of 85% after 10 cycles.

[0022] Example 3 The difference between this embodiment and Embodiment 1 is that the mixing weight ratio of CNT to NCM811 precursor is 5%. After heat treatment at 700-900℃, the specific surface area of ​​the porous NCM811 particles is 0.90 m². 2 / g; the battery performance test showed an initial discharge capacity (0.1C) of 168mAh / g, and a capacity retention rate of 90% after 10 cycles.

[0023] Comparative Example 1 The difference between this comparative example and Example 1 is that the NCM811 precursor was not mixed with CNTs; instead, the NCM811 precursor was directly heat-treated at 700-900°C to obtain NCM811 particles without a porous structure, with a specific surface area of ​​0.76 m². 2 / g. Battery performance testing showed an initial discharge capacity (0.1C) of 160mAh / g, and a capacity retention rate of 80% after 10 cycles.

[0024] Comparative Example 2 The difference between this comparative example and Example 1 is that the weight ratio of CNT to NCM811 precursor is 10%. After heat treatment at 700-900℃, the specific surface area of ​​the porous NCM811 particles is 1.09 m². 2 / g; the battery performance test showed an initial discharge capacity (0.1C) of 154mAh / g, and a capacity retention rate of 77% after 10 cycles.

[0025] The above embodiments and comparative examples are based on the first cycle discharge capacity being 100%, and the relative values ​​of the tenth cycle discharge capacity are calculated. The latter was performed in a 25°C high-temperature bath at 0.5 mA / cm². 2 The current density was measured during charging and discharging in the voltage range of 4V-2.5V, and the results were shown in Table 1 below. Table 1 ; As can be seen from the above data, when the weight ratio of template material (CNT) is in the range of 1%-5%, the prepared composite cathode material and all-solid-state battery are superior to the schemes without template material or with excessive template material in terms of discharge capacity and cycle life, and can better achieve the technical objectives of the present invention.

[0026] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A composite cathode material for all-solid-state batteries, characterized in that, It consists of positive electrode active material particles and a solid electrolyte in a porous structure formed inside the active material particles, and the solid electrolyte forms an ion conduction pathway within the active material particles.

2. The composite cathode material for all-solid-state batteries according to claim 1, characterized in that, The positive electrode active material particles are nickel-rich layered oxides.

3. The composite cathode material for all-solid-state batteries according to claim 1, characterized in that, The solid electrolyte is an Argyrodite type solid electrolyte.

4. The composite cathode material for all-solid-state batteries according to claim 1, characterized in that, The porous structure formed by the internal pore structure of the active material particles has a higher specific surface area than that of the same composition of positive electrode active material that does not have this porous structure.

5. A method for manufacturing a composite cathode material for an all-solid-state battery according to any one of claims 1-3, characterized in that, Includes the following steps: 1) Mix the precursor of the positive electrode active material particles with a template material that can be decomposed and disappeared after sintering; 2) The mixture of the precursor and template material is subjected to heat treatment at 700-900℃ to decompose and disappear the template material and form a porous structure inside the positive electrode active material; 3) Fill the positive electrode active material that forms a porous structure with a solid electrolyte.

6. The method for manufacturing a composite cathode material for all-solid-state batteries according to claim 5, characterized in that, In step 1), the template material can be either carbon nanotubes or mesoporous silica.

7. The method for manufacturing a composite cathode material for an all-solid-state battery according to claim 6, characterized in that, The mixing ratio of the template material to the positive electrode active material precursor is 1%-5% by weight.

8. An all-solid-state battery, characterized in that, The composite cathode material according to any one of claims 1-3 is used as the cathode.

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