A positive electrode active material for an all-solid-state battery, a method of manufacturing the same, a composite positive electrode material for an all-solid-state battery, and an all-solid-state battery

Abstract

The present application relates to the field of solid-state batteries, and particularly relates to a positive electrode active material for a full solid-state battery, a preparation method thereof, a composite positive electrode material for a full solid-state battery, and a full solid-state battery. The positive electrode active material for the full solid-state battery is secondary particles formed by agglomeration of strip-shaped primary particles, the length of the strip-shaped primary particles is 0.5-1 microns, the diameter of the secondary particles is 3-5 microns, the specific surface area is 0.3-1 m 2 / g, and the porosity is less than 10%. The positive electrode active material for the full solid-state battery can solve the problems of physical contact failure of the solid-solid interface of the positive electrode, poor structural stability of the positive electrode matrix material, poor Li + transport dynamics in the positive electrode, and the like in the prior art.

Description

Technical Field

[0001] This invention relates to the field of solid-state batteries, and more particularly to a positive electrode active material and preparation method for all-solid-state batteries, a composite positive electrode material for all-solid-state batteries, and an all-solid-state battery. Background Technology

[0002] With the widespread application of lithium batteries in consumer electronics, electric vehicles, and energy storage, the performance requirements for them are increasing. Traditional liquid lithium batteries pose safety hazards due to the flammability, explosiveness, and leakage of their electrolytes, and their energy density is nearing its limit, necessitating improvements in both safety and energy density. All-solid-state batteries, which use solid electrolytes instead of organic electrolytes, hold promise for solving safety issues. Combining lithium metal anodes with high-energy-density nickel-rich ternary cathode materials can further enhance energy density.

[0003] However, in all-solid-state batteries, the microstructure and solid-solid contact of the composite electrode directly affect ion and electron conduction. Pressure needs to be applied to ensure tight contact between the positive electrode and electrolyte particles, but excessive pressure may cause the positive electrode particles to break. Furthermore, during charge and discharge, volume changes in the positive electrode particles can easily cause the layered structure to collapse, creating voids and cracks between the positive electrode and electrolyte particles, leading to mechanical contact failure. Therefore, improving the structural stability of the positive electrode material and its contact with the electrolyte is crucial. Existing technologies involving positive electrode active materials for all-solid-state batteries mainly improve electrode interface stability through coating and doping, but do not control the particle size and microstructure of the positive electrode active material.

[0004] Therefore, there is an urgent need to provide a positive electrode active material that can maintain good solid-solid interface contact and structural stability in all-solid batteries. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention provides a positive electrode active material and its preparation method for all-solid-state batteries, a composite positive electrode material for all-solid-state batteries, and an all-solid-state battery. This positive electrode active material for all-solid-state batteries can solve the problems of physical contact failure at the solid-solid interface of the positive electrode, poor structural stability of the positive electrode matrix material, and internal Li-C content issues in existing technologies. + Problems such as poor transport dynamics.

[0006] Therefore, in a first aspect, the present invention provides a positive electrode active material for all-solid-state batteries. The positive electrode active material for all-solid-state batteries is a secondary particle formed by the agglomeration of strip-shaped primary particles. The length of the strip-shaped primary particles is 0.5–1 μm, and the diameter of the secondary particles is 3–5 μm, with a specific surface area of ​​0.3–1 m². 2 / g, porosity <10%.

[0007] The positive electrode active material provided by this invention consists of secondary particles formed by the close packing of primary particles. The strip-shaped primary particles can be matched with a solid electrolyte to achieve sufficient contact between the positive electrode particles and the electrolyte, avoiding physical contact failure at the positive electrode interface. At the same time, the small-sized, dense secondary particles can reduce the Li inside the particles. + Transmission path, improve Li + The transport kinetics. The all-solid-state battery assembled based on this positive electrode active material exhibits excellent electrochemical performance.

[0008] According to an embodiment of the present invention, the aspect ratio of the primary particle is 3 to 6.

[0009] According to an embodiment of the present invention, the particle size ratio of the secondary particles to the primary particles is (4-8):1.

[0010] According to an embodiment of the present invention, the positive electrode active material for the all-solid-state battery includes a matrix and a coating layer covering the surface of the matrix;

[0011] The matrix has the composition shown in Formula I:

[0012] LiNi x Co y Mn z O2 type I;

[0013] Among them, 0 <x<1,0<y<1,x+y+z=1;

[0014] The matrix also contains element M, which is selected from at least one of Ti, Zr, Hf, V, Nb, Ta, W, B, Al, Si, and P.

[0015] The coating layer comprises lithium metal oxide containing doped elements.

[0016] According to an embodiment of the present invention, the doping element includes at least one selected from Ti, Zr, Hf, V, Nb, Ta, W, B, Al, Si, and P.

[0017] According to an embodiment of the present invention, the thickness of the coating layer is 2 to 50 nm.

[0018] According to an embodiment of the present invention, the diffusion depth of element M in the matrix is ​​1 to 200 nm, and the mass percentage of element M in the matrix is ​​0.01% to 15%.

[0019] A second aspect of the present invention provides a method for preparing the positive electrode active material for all-solid-state batteries described in the first aspect, comprising the following steps:

[0020] A positive electrode active material precursor is prepared by mixing the positive electrode active material precursor with a lithium salt to obtain a first mixture.

[0021] The first mixture is subjected to a first sintering treatment to obtain a first intermediate;

[0022] The first intermediate was mixed with the oxide to obtain a second mixture;

[0023] The second mixture is subjected to a second sintering process to obtain the positive electrode active material for the all-solid-state battery.

[0024] Thus, by using a stepwise thermal treatment sintering process, the microstructure of the cathode particles can be controlled and the interface modified. The all-solid-state battery assembled based on this cathode active material has excellent electrochemical performance. At the same time, this method can be tested on a large scale and has good prospects for industrial production applications.

[0025] According to an embodiment of the present invention, the mass ratio of the lithium salt to the positive electrode active material precursor is (1.01-1.5):1, preferably (1.02-1.3):1.

[0026] According to an embodiment of the present invention, the temperature of the first sintering treatment is 450-600°C and the time is 3-7 hours.

[0027] According to embodiments of the present invention, the oxide includes at least one selected from TiO2, ZrO2, HfO2, V2O5, Nb2O5, Ta2O5, WO3, B2O3, Al2O3, SiO2, and P2O5.

[0028] According to an embodiment of the present invention, the mass ratio of the oxide to the positive electrode active material precursor is (0.0005-0.3):1, preferably (0.001-0.15):1.

[0029] According to an embodiment of the present invention, the temperature of the second sintering treatment is 700-1000°C, and the time is 10-20 hours.

[0030] According to an embodiment of the present invention, the sintering atmosphere of the first sintering process and the second sintering process independently includes one of oxygen, air, and carbon dioxide.

[0031] The third aspect of the present invention provides a composite cathode material for all-solid-state batteries, the composite cathode material for all-solid-state batteries comprising the cathode active material for all-solid-state batteries described in the first aspect or the cathode active material for all-solid-state batteries obtained by the method described in the second aspect.

[0032] Therefore, the composite cathode material used in this all-solid-state battery can avoid physical contact failure at the cathode interface and reduce the internal Li content of the particles. + Transmission path, improve Li + Based on the transport kinetics, the all-solid-state battery assembled based on this composite cathode material exhibits excellent electrochemical performance.

[0033] According to an embodiment of the present invention, the composite cathode material for all-solid-state batteries further includes a sulfide solid electrolyte.

[0034] According to embodiments of the present invention, the sulfide solid electrolyte includes Li3PS4 and Li 10 GeP2S 12 Li7P3S 11 Li6PS5Cl, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li 5.5 PS 4.5 Cl 1.5 Li 5.5 PS 4.5 Cl 0.8 Br 0.7 At least one of them.

[0035] According to an embodiment of the present invention, the mass ratio of the positive electrode active material to the sulfide solid electrolyte in the composite positive electrode material is (0.5-20):1.

[0036] A fourth aspect of the present invention provides an all-solid-state battery, the all-solid-state battery comprising a positive electrode, the positive electrode comprising the positive electrode active material for an all-solid-state battery as described in the first aspect, or the positive electrode active material for an all-solid-state battery obtained by the method described in the second aspect, or the composite positive electrode material for an all-solid-state battery as described in the third aspect.

[0037] Therefore, this all-solid-state battery has good electrochemical performance.

[0038] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0039] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0040] Figure 1 The image shown is a low-magnification SEM image of the positive electrode active material obtained in Example 1 of the present invention;

[0041] Figure 2 This shows a high-magnification SEM image of the positive electrode active material obtained in Example 1 of the present invention;

[0042] Figure 3 The XRD diffraction pattern of the positive electrode active material obtained in Example 1 of the present invention is shown;

[0043] Figure 4 The image shows a SEM image of the composite cathode of the positive electrode active material obtained in Example 1 of the present invention in a sulfide all-solid-state battery;

[0044] Figure 5 The graph shows the first charge-discharge specific capacity performance of the all-solid-state battery assembled with the positive electrode active material obtained in Example 1 of the present invention.

[0045] Figure 6 The graph shows the rate performance of the all-solid-state battery assembled from the positive electrode active material obtained in Example 1 of the present invention.

[0046] Figure 7 The diagram shows the cycle performance of the all-solid-state battery assembled with the positive electrode active material obtained in Example 1 of the present invention. Detailed Implementation

[0047] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0048] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0049] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0050] To facilitate understanding of the invention, certain technical and scientific terms are specifically defined below. Unless otherwise expressly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains.

[0051] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.

[0052] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0053] Traditional cathode polycrystalline spheres have small primary particles and large secondary particles. Numerous interfaces and voids exist within the cathode particles, and the large secondary particles contain Li... + The transmission path is relatively long, Li + The transport kinetics are poor. Although small-particle-size single-crystal cathodes of Li... + It has excellent transmission performance, but stress concentration is easily generated during charging and discharging, which can cause cracks and results in poor stability.

[0054] Based on this, the first aspect of the present invention provides a positive electrode active material for all-solid-state batteries. The positive electrode active material for all-solid-state batteries is a secondary particle formed by the agglomeration of strip-shaped primary particles. The length of the strip-shaped primary particles is 0.5–1 μm, and the diameter of the secondary particles is 3–5 μm, with a specific surface area of ​​0.3–1 m². 2 / g, porosity <10%.

[0055] The positive electrode active material of this invention is formed by the close packing of primary particles into a secondary spherical shape. The elongated primary particles can be matched with a sulfide solid electrolyte of the same size to achieve sufficient contact between the positive electrode particles and the electrolyte, avoiding physical contact failure at the positive electrode interface. The small, dense secondary particles can reduce the internal Li content of the particles. + Transmission path, improve Li + The transport kinetics are improved, and the interface modification treatment suppresses interface side reactions and improves the structural stability of the positive electrode active material.

[0056] In this invention, "length" should be understood as the length of the longest diameter of a single particle.

[0057] According to a specific embodiment of the present invention, the aspect ratio of the primary particle is 3 to 6.

[0058] In this invention, "length-to-diameter ratio" should be understood as the ratio between the length of the longest diameter of a single particle and the length of the shortest diameter.

[0059] According to a specific embodiment of the present invention, the particle size ratio of the secondary particles to the primary particles is (4-8):1.

[0060] In this invention, "particle size ratio" should be understood as the ratio between the length of the longest diameter of the secondary particle and the length of the longest diameter of the primary particle.

[0061] According to a specific embodiment of the present invention, the positive electrode active material for the all-solid-state battery includes a matrix and a coating layer covering the surface of the matrix;

[0062] The matrix has the composition shown in Formula I:

[0063] LiNi x Co y Mn z O2 type I;

[0064] Among them, 0 <x<1,0<y<1,x+y+z=1;

[0065] The matrix also contains element M, which is selected from at least one of Ti, Zr, Hf, V, Nb, Ta, W, B, Al, Si, and P.

[0066] The coating layer comprises lithium metal oxide containing doped elements.

[0067] Therefore, this coating layer has the ability to transmit Li. + In addition to its functionality, the surface of the cathode particles underwent coating modification treatment. This interface modification suppressed interfacial side reactions and reduced interfacial impedance. The cathode particles were also doped internally, improving the stability of the cathode material matrix structure.

[0068] According to a specific embodiment of the present invention, the doping element includes at least one selected from Ti, Zr, Hf, V, Nb, Ta, W, B, Al, Si, and P.

[0069] According to a specific embodiment of the present invention, the thickness of the coating layer is 2 to 50 nm.

[0070] According to a specific embodiment of the present invention, the diffusion depth of element M in the matrix is ​​1 to 200 nm, and the mass percentage of element M in the matrix is ​​0.01% to 15%.

[0071] In this invention, "diffusion depth" should be understood as the depth of diffusion from the surface of a particle into the interior.

[0072] According to embodiments of the present invention, a second aspect provides a method for preparing the positive electrode active material for all-solid-state batteries described in the first aspect, comprising the following steps:

[0073] A positive electrode active material precursor is prepared by mixing the positive electrode active material precursor with a lithium salt to obtain a first mixture.

[0074] The first mixture is subjected to a first sintering treatment to obtain a first intermediate;

[0075] The first intermediate was mixed with the oxide to obtain a second mixture;

[0076] The second mixture is subjected to a second sintering process to obtain the positive electrode active material for the all-solid-state battery.

[0077] The cathode material is sintered through a stepwise heat treatment process, which enables microstructure control and interface modification of cathode particles. This method can be tested on a large scale and has good prospects for industrial production applications.

[0078] According to specific embodiments of the present invention, the preparation method of the positive electrode active material precursor is not particularly limited, and conventional precipitation methods can be used for preparation, without affecting the subsequent preparation of positive electrode active materials for all-solid-state batteries.

[0079] According to a specific embodiment of the present invention, the mass ratio of the lithium salt to the positive electrode active material precursor is (1.01 to 1.5):1. As some specific examples, the mass ratio of the lithium salt to the positive electrode active material precursor can be 1.01:1, 1.02:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, etc., preferably (1.02 to 1.3):1.

[0080] According to specific embodiments of the present invention, the type of lithium salt is not particularly limited, including but not limited to Li2CO3, LiOH·H2O, Li2O, LiNO3, and Li2C2O4.

[0081] According to a specific embodiment of the present invention, the mixing speed of the positive electrode active material precursor and the lithium salt can be 500-1000 rpm / s, and the mixing time can be 5-30 min.

[0082] According to specific embodiments of the present invention, the temperature and time of the first sintering treatment are not particularly limited. As some specific examples, the temperature of the first sintering treatment can be 450-600°C and the time can be 3-7 hours.

[0083] According to a specific embodiment of the present invention, the heating rate of the first sintering treatment can be 3 to 5 °C / min.

[0084] According to a specific embodiment of the present invention, the sintering atmosphere of the first sintering treatment includes one of oxygen, air, and carbon dioxide.

[0085] According to specific embodiments of the present invention, the oxide includes at least one selected from TiO2, ZrO2, HfO2, V2O5, Nb2O5, Ta2O5, WO3, B2O3, Al2O3, SiO2, and P2O5.

[0086] According to a specific embodiment of the present invention, the mixing speed of the first intermediate and the oxide can be 300-800 rpm / s, and the mixing time can be 5-20 min.

[0087] According to specific embodiments of the present invention, the mass ratio of the oxide to the positive electrode active material precursor is (0.0005 to 0.3):1. As some specific examples, the mass ratio of the oxide to the positive electrode active material precursor can be 0.0005:1, 0.001:1, 0.01:1, 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, etc., preferably (0.001 to 0.15):1.

[0088] According to specific embodiments of the present invention, the temperature and time of the second sintering treatment are not particularly limited. As some specific examples, the temperature of the second sintering treatment can be 700-1000°C and the time can be 10-20h.

[0089] According to a specific embodiment of the present invention, the heating rate of the second sintering treatment can be 1 to 8 °C / min.

[0090] According to a specific embodiment of the present invention, the sintering atmosphere of the second sintering treatment includes one of oxygen, air, and carbon dioxide.

[0091] According to embodiments of the present invention, a third aspect of the present invention provides a composite cathode material for all-solid-state batteries, comprising the cathode active material for all-solid-state batteries described in the first aspect or the cathode active material for all-solid-state batteries obtained according to the method described in the second aspect.

[0092] According to specific embodiments of the present invention, the composite cathode material for the all-solid-state battery further includes a sulfide solid electrolyte. As some specific examples, the sulfide solid electrolyte includes Li3PS4 and Li... 10 GeP2S 12 Li7P3S 11 Li6PS5Cl, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li 5.5 PS 4.5 Cl 1.5 Li 5.5 PS 4.5 Cl 0.8 Br 0.7 At least one of them.

[0093] According to a specific embodiment of the present invention, the mass ratio of the positive electrode active material to the sulfide solid electrolyte in the composite positive electrode material is (0.5-20):1.

[0094] According to a specific embodiment of the present invention, the preparation method of the composite cathode material for all-solid-state batteries is not particularly limited, and it is sufficient to mix the aforementioned cathode active material for all-solid-state batteries with a sulfide solid electrolyte.

[0095] According to an embodiment of the present invention, a fourth aspect of the present invention provides an all-solid-state battery, the all-solid-state battery including a positive electrode, the positive electrode including the positive electrode active material for all-solid-state batteries described in the first aspect, or the positive electrode active material for all-solid-state batteries obtained according to the method described in the second aspect, or the composite positive electrode material for all-solid-state batteries described in the third aspect.

[0096] Because of the good contact between the positive electrode particles and the solid electrolyte at the solid-solid interface, the interface Li + With good transmission and a stable positive electrode matrix material structure, the full cell has high discharge specific capacity, rate capability, and cycle performance.

[0097] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0098] Example 1

[0099] This embodiment provides a positive electrode active material for all-solid-state batteries, wherein the positive electrode active material is LiNi. 0.95 Co 0.04 Mn 0.01 O2 particles are primary particles that are elongated strips with a diameter-to-length ratio of 5:1 and a size of 3–4 μm. Secondary particles have a specific surface area of ​​0.5 m². 2 The cathode particles have a porosity of 8% and a particle size ratio of 5:1 between primary and secondary particles. The surface of the cathode particles is coated with a Li-Zr-O compound with a thickness of 5 nm. The cathode substrate material is doped with Zr. 4+ The element, with a doping depth of 20 nm and a mass percentage of 0.5%, is used. The specific preparation process includes the following steps:

[0100] Ni, the positive electrode precursor 0.95 Co 0.4 Mn 0.1(OH)2 and lithium salt LiOH·H2O were added to a high-speed mixer at a ratio of 1:1.1 for premixing at a speed of 500 rpm / s for 10 min to obtain mixture 1. Mixture 1 was then subjected to a first sintering treatment at a temperature of 550℃, a heating rate of 3℃ / min, and a holding time of 5 h. After cooling to room temperature in the furnace, pre-sintered material 1 was obtained. ZrO2 was added to pre-sintered material 1 at a mass ratio of 0.005:1 to the positive electrode precursor, and then added to a high-speed mixer for a second mixing treatment at a speed of 300 rpm / s for 5 min to obtain mixture 2. Mixture 2 was then subjected to a second sintering treatment at a temperature of 850℃, a heating rate of 5℃ / min, and a holding time of 15 h. After cooling to room temperature in the furnace, the final positive electrode active material was obtained. The atmosphere for both sintering processes was oxygen.

[0101] The low-magnification and high-magnification SEM images of the positive electrode active material are shown below. Figure 1-2 . Figure 3 Its XRD diffraction pattern.

[0102] Example 2

[0103] This embodiment provides a positive electrode active material for all-solid-state batteries, wherein the positive electrode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2 particles are primary particles that are elongated strips with a diameter-to-length ratio of 4:1 and a size of 0.6–0.8 μm. Secondary particles have a size of 4–5 μm and a specific surface area of ​​0.6 m². 2 The cathode particles have a porosity of 9% and a particle size ratio of 7:1 between primary and secondary particles. The surface of the cathode particles is coated with a Li-Nb-O compound with a thickness of 10 nm. The cathode substrate material is doped with Nb. 5+ The element, with a doping depth of 25 nm and a mass percentage of 1%, is used. The specific preparation process includes the following steps:

[0104] Ni, the positive electrode precursor 0.8 Co 0.1 Mn 0.1(OH)2 and lithium salt LiOH·H2O were added to a high-speed mixer at a ratio of 1:1.08 for premixing at a speed of 600 rpm / s for 12 min to obtain mixture 1. Mixture 1 was then subjected to a first sintering treatment at a temperature of 500℃, a heating rate of 4℃ / min, and a holding time of 6 h. After cooling to room temperature in the furnace, pre-calcined material 1 was obtained. Nb2O5 was added to pre-calcined material 1 at a mass ratio of 0.01:1 to the positive electrode precursor, and then added to a high-speed mixer for a second mixing treatment at a speed of 800 rpm / s for 10 min to obtain mixture 2. Mixture 2 was then subjected to a second sintering treatment at a temperature of 830℃, a heating rate of 6℃ / min, and a holding time of 12 h. After cooling to room temperature in the furnace, the final positive electrode active material was obtained. The atmosphere for both sintering processes was oxygen.

[0105] Example 3

[0106] This embodiment provides a positive electrode active material for all-solid-state batteries, wherein the positive electrode active material is LiNi. 0.6 Co 0.2 Mn 0.2 O2 particles are primary particles that are elongated strips with a diameter-to-length ratio of 3:1 (0.5–0.6 μm), while secondary particles have a size of 4–5 μm and a specific surface area of ​​0.4 m². 2 The cathode particles have a porosity of 7% and a particle size ratio of 8:1 (secondary to primary particles). The surface of the cathode particles is coated with a Li-Al-O compound with a thickness of 15 nm. The cathode substrate material is doped with Al. 3+ The element, with a doping depth of 30 nm and a mass percentage of 2%, is used. The specific preparation process includes the following steps:

[0107] Ni, the positive electrode precursor 0.6 Co 0.2 Mn 0.2 (OH)2 and lithium salt Li2CO3 were premixed in a high-speed mixer at a ratio of 1:1.07 at a speed of 700 rpm / s for 8 min to obtain mixture 1. Mixture 1 was then subjected to a first sintering treatment at a temperature of 480℃, a heating rate of 5℃ / min, and a holding time of 6 h. After cooling to room temperature in the furnace, pre-calcined material 1 was obtained. Al2O3 was added to pre-calcined material 1 at a mass ratio of 0.02:1 to the positive electrode precursor, and then subjected to a second mixing treatment in a high-speed mixer at a speed of 400 rpm / s for 10 min to obtain mixture 2. Mixture 2 was then subjected to a second sintering treatment at a temperature of 780℃, a heating rate of 7℃ / min, and a holding time of 10 h. After cooling to room temperature in the furnace, the final positive electrode active material was obtained. The atmosphere for both sintering processes was oxygen.

[0108] Example 4

[0109] This embodiment provides a positive electrode active material for all-solid-state batteries, wherein the positive electrode active material is LiNi. 0.88 Co 0.08 Mn 0.04 O2 particles are primary particles that are elongated strips with a length-to-diameter ratio of 6:1, ranging from 0.8 to 1 μm in size. Secondary particles have a size of 4 to 5 μm and a specific surface area of ​​0.8 m². 2 The cathode particles have a porosity of 10% and a particle size ratio of 5:1 between primary and secondary particles. The surface of the cathode particles is coated with a Li-Zr-O compound with a thickness of 5 nm. The cathode substrate material is doped with Zr. 4+ The element, with a doping depth of 50 nm and a mass percentage of 3%, is used. The specific preparation process includes the following steps:

[0110] Ni, the positive electrode precursor 0.88 Co 0.08 Mn 0.04 (OH)2 and lithium salt Li2CO3 were premixed in a high-speed mixer at a ratio of 1:1.08 for 10 min at a speed of 800 rpm / s to obtain mixture 1. Mixture 1 was then subjected to a first sintering treatment at a temperature of 530℃, a heating rate of 3℃ / min, and a holding time of 6 h. After cooling to room temperature in the furnace, pre-calcined material 1 was obtained. ZrO2 was added to pre-calcined material 1 at a mass ratio of 0.03:1 to the positive electrode precursor, and then subjected to a second mixing treatment in a high-speed mixer at a speed of 600 rpm / s for 15 min to obtain mixture 2. Mixture 2 was then subjected to a second sintering treatment at a temperature of 760℃, a heating rate of 5℃ / min, and a holding time of 20 h. After cooling to room temperature in the furnace, the final positive electrode active material was obtained. The atmosphere for both sintering processes was oxygen.

[0111] Example 5

[0112] This embodiment provides a positive electrode active material for all-solid-state batteries, wherein the positive electrode active material is LiNi. 0.94 Co 0.02 Mn 0.04 O2 particles are primary particles that are elongated strips with a diameter-to-length ratio of 5:1 (0.5–0.7 μm), while secondary particles have a size of 3–4 μm and a specific surface area of ​​0.3 m². 2 / g, porosity 5%, secondary particle size ratio of primary particles 5:1, positive electrode particles are coated with a Li-Hf-O compound, coating thickness 8nm, Hf is doped in the positive electrode matrix material. 4+The element, with a doping depth of 20 nm and a mass percentage of 2%, is used. The specific preparation process includes the following steps:

[0113] Ni, the positive electrode precursor 0.94 Co 0.02 Mn 0.04 (OH)2 and lithium salt LiOH·H2O were added to a high-speed mixer at a ratio of 1:1.07 for premixing at a speed of 600 rpm / s for 5 min to obtain mixture 1. Mixture 1 was then subjected to a first sintering treatment at a temperature of 520℃, a heating rate of 4℃ / min, and a holding time of 7 h. After cooling to room temperature in the furnace, pre-calcined material 1 was obtained. HfO2 was added to pre-calcined material 1 at a mass ratio of 0.02:1 to the positive electrode precursor, and then added to a high-speed mixer for a second mixing treatment at a speed of 400 rpm / s for 8 min to obtain mixture 2. Mixture 2 was then subjected to a second sintering treatment at a temperature of 820℃, a heating rate of 6℃ / min, and a holding time of 18 h. After cooling to room temperature in the furnace, the final positive electrode active material was obtained. The atmosphere for both sintering processes was oxygen.

[0114] Comparative Example 1

[0115] The same cathode precursor material, lithium salt and transition metal oxide as in Example 1 were used, and the mass ratio was also the same as in Example 1. The difference was that a one-step sintering process was used, that is, the three raw materials were added together in a high-speed mixer and mixed, and the resulting mixture was subjected to one-step sintering treatment at a sintering temperature of 850°C. The mixture was then cooled to room temperature in the furnace to obtain the final cathode active material. The sintering atmosphere was also the same as in Example 1.

[0116] The obtained positive electrode active material is LiNi 0.95 Co 0.04 Mn 0.01 O2, primary particles are elongated strips of 0.1–0.2 μm in size with an aspect ratio of 1.5:1, secondary particles are 10–12 μm in size with a specific surface area of ​​3 m². 2 / g, porosity 20%, the surface of the positive electrode particles is coated with a Li-Zr-O compound, the coating thickness is 10nm, and Zr is doped in the positive electrode matrix material. 4+ The element has a doping depth of 40 nm and a mass percentage of 1%.

[0117] Preparation of composite cathode material for all-solid-state batteries: This composite cathode material consists of a sulfide solid electrolyte and the cathode active material prepared in Examples 1-5 or Comparative Example 1. The specific preparation process is as follows: the sulfide solid electrolyte and the cathode active material are added to a mixer at a mass ratio of 7:3 and mixed evenly to obtain the final composite cathode material. Figure 4This is a SEM image of the composite cathode material obtained based on Example 1.

[0118] Assembly of the all-solid-state battery: The all-solid-state battery consists of a sulfide solid electrolyte, a lithium indium alloy anode, and the positive electrode active material prepared in Examples 1-5 or Comparative Example 1. The specific assembly process is as follows: First, 100 mg of sulfide solid electrolyte is placed into a Φ10 mm mold and pressed into an intermediate layer under a pressure of 200 MPa; then, 10 mg of composite positive electrode material (composed of 7 mg of high-nickel positive electrode material and 3 mg of sulfide solid electrolyte) is added to one end of the intermediate layer and pressed into shape under a pressure of 200 MPa; finally, a certain amount of lithium indium alloy anode is added to the other end of the intermediate layer and assembled into an all-solid-state battery under a pressure of 240 MPa.

[0119] Testing of all-solid-state batteries: Test temperature 30℃, voltage range 2.6~4.4V vs. Li + / Li. The full cell at 0.1C (1C = 200 mAg) -1 The first-cycle charge-discharge capacity and coulombic efficiency were tested at a current density of 0.2C, 0.5C, 0.8C, 1C, 2C, and 3C; rate performance was tested at different current densities; and long-cycle performance was tested at a current density of 1C. The results are shown in Table 1. Figure 5-7 The graph shows the electrochemical performance test results of the positive electrode active material assembly obtained in Example 1 of this invention.

[0120] Table 1

[0121]

[0122] Analysis of the experimental results shows that the positive electrode active material for the all-solid-state battery of the present invention has large primary particles. These large primary particles can fully contact the sulfide solid electrolyte, reducing physical contact failure at the positive electrode solid-solid interface. The secondary particles of this positive electrode active material are smaller, which can shorten the internal Li... + The transmission path improves Li + The transport dynamics are described. All-solid-state batteries composed using the positive electrode active material of this invention exhibit excellent discharge specific capacity, high rate performance, and stable long-cycle performance. This is attributed to the unique microstructure of the positive electrode material of this invention, which consists of large primary particles and small secondary particles. This structure helps reduce solid-solid interface contact failure, while the coating and doping modification improves the stability of the positive electrode interface and structure.

[0123] Comparing Example 1 and Comparative Example 1, it was found that smaller primary particles of the positive electrode active material increase the interface within the polycrystalline secondary particles, while larger secondary particles contain Li... + A longer transport path will cause the Li inside the cathode material to... +The transport kinetics are poor. The electrochemical performance of the all-solid-state battery in Comparative Example 1 is worse than that in Example 1. Therefore, based on the comparison of the microstructure of the positive electrode active material, it can be shown that adjusting the microstructure of the positive electrode active material is crucial to improving the electrochemical performance of the all-solid-state battery.

[0124] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0125] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An all-solid-state battery, characterized in that, The all-solid-state battery includes a positive electrode, which comprises a positive electrode active material for all-solid-state batteries or a composite positive electrode material for all-solid-state batteries. The composite positive electrode material for all-solid-state batteries includes the positive electrode active material for all-solid-state batteries. The positive electrode active material for the all-solid-state battery is a secondary particle formed by the agglomeration of strip-shaped primary particles. The length of the strip-shaped primary particles is 0.5~1μm, and the diameter of the secondary particles is 3~5μm, with a specific surface area of ​​0.3~1m². 2 / g, porosity <10% The particle size ratio of the secondary particles to the primary particles is (4~8):

1. The aspect ratio of the primary particles is 3 to 6. The positive electrode active material for the all-solid-state battery includes a matrix and a coating layer covering the surface of the matrix; The matrix has the composition shown in Formula I: LiNi x Co y Mn z O2 type I; Among them, 0 <x<1,0<y<1,x+y+z=1; The matrix also contains element M, which is selected from at least one of Ti, Zr, Hf, V, Nb, Ta, W, B, Al, Si, and P. The coating layer comprises a lithium metal oxide containing doped elements; The doping element includes at least one of Ti, Zr, Hf, V, Nb, Ta, W, B, Al, Si, and P; The diffusion depth of element M in the matrix is ​​1~200nm.

2. The all-solid-state battery according to claim 1, characterized in that, The thickness of the coating layer is 2~50nm.

3. The all-solid-state battery according to claim 2, characterized in that, The mass percentage of element M in the matrix is ​​0.01% to 15%.

4. The all-solid-state battery according to any one of claims 1-3, characterized in that, The preparation method of the positive electrode active material for the all-solid-state battery includes the following steps: A positive electrode active material precursor is prepared by mixing the positive electrode active material precursor with a lithium salt to obtain a first mixture. The first mixture is subjected to a first sintering treatment to obtain a first intermediate; The first intermediate was mixed with the oxide to obtain a second mixture; The second mixture is subjected to a second sintering process to obtain the positive electrode active material for the all-solid-state battery.

5. The all-solid-state battery according to claim 4, characterized in that, The mass ratio of the lithium salt to the positive electrode active material precursor is (1.01~1.5):

1.

6. The all-solid-state battery according to claim 5, characterized in that, The mass ratio of the lithium salt to the positive electrode active material precursor is (1.02~1.3):

1.

7. The all-solid-state battery according to claim 4, characterized in that, The temperature of the first sintering treatment is 450~600℃, and the time is 3~7h.

8. The all-solid-state battery according to claim 4, characterized in that, The oxide includes at least one of TiO2, ZrO2, HfO2, V2O5, Nb2O5, Ta2O5, WO3, B2O3, Al2O3, SiO2, and P2O5.

9. The all-solid-state battery according to claim 4, characterized in that, The mass ratio of the oxide to the positive electrode active material precursor is (0.0005~0.3):

1.

10. The all-solid-state battery according to claim 9, characterized in that, The mass ratio of the oxide to the positive electrode active material precursor is (0.001~0.15):

1.

11. The all-solid-state battery according to claim 4, characterized in that, The second sintering treatment is performed at a temperature of 700~1000℃ for 10~20 hours.

12. The all-solid-state battery according to claim 4, characterized in that, The sintering atmosphere of the first sintering treatment and the second sintering treatment independently includes one of oxygen, air, and carbon dioxide.

13. The all-solid-state battery according to claim 1, characterized in that, The composite cathode material for all-solid-state batteries also includes sulfide solid electrolytes.

14. The all-solid-state battery according to claim 13, characterized in that, The sulfide solid electrolyte includes Li3PS4, Li 10 GeP2S 12 Li7P3S 11 Li6PS5Cl, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li 5.5 PS 4.5 Cl 1.5 Li 5.5 PS 4.5 Cl 0.8 Br 0.7 At least one of them.

15. The all-solid-state battery according to claim 14, characterized in that, The mass ratio of the positive electrode active material to the sulfide solid electrolyte in the composite positive electrode material is (0.5-20):1.

Images