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CN-121983552-A - Single crystal-polycrystal composite positive electrode material, preparation method thereof, solid-state battery positive electrode layer and solid-state battery

CN121983552ACN 121983552 ACN121983552 ACN 121983552ACN-121983552-A

Abstract

The invention provides a single crystal-polycrystal composite positive electrode material, a preparation method thereof, a solid battery positive electrode layer and a solid battery, wherein the single crystal-polycrystal composite positive electrode material comprises a single crystal positive electrode material, a polycrystal positive electrode material and a solid electrolyte material, the grain diameter D50 of the polycrystal positive electrode material is larger than the grain diameter D50 of the single crystal positive electrode material and smaller than or equal to 1, and the solid electrolyte material is larger than the grain diameter D50 of the single crystal positive electrode material. According to the invention, through three-level grain composition, the mass ratio of the monocrystalline anode material to the polycrystalline anode material is controlled, so that the monocrystalline grains construct a rigid framework, the polycrystalline grains and the electrolyte fill gaps, the contact area of the active material and the electrolyte is increased, the stack pressure is reduced, the compaction density is increased, and the problems of poor interface stability, poor multiplying power performance and high cost are solved.

Inventors

  • HE FENG
  • YANG MAOXIA
  • DUAN JIDONG
  • ZHAO RUIRUI

Assignees

  • 成都亿纬锂能有限公司

Dates

Publication Date
20260505
Application Date
20260225

Claims (10)

  1. 1. The single crystal-polycrystal composite positive electrode material is characterized by comprising a single crystal positive electrode material, a polycrystal positive electrode material and a solid electrolyte material, wherein the particle size D50 of the polycrystal positive electrode material is larger than the particle size D50 of the single crystal positive electrode material, and the particle size D50 of the single crystal positive electrode material is larger than the particle size D50 of the solid electrolyte material; the mass ratio of the polycrystalline anode material to the monocrystalline anode material is less than or equal to 1.
  2. 2. The single crystal-polycrystalline composite positive electrode material according to claim 1, wherein the polycrystalline positive electrode material comprises a polycrystalline substrate and an ion conductor coating layer on the surface of the polycrystalline substrate; preferably, the particle diameter D50 of the polycrystalline positive electrode material is 2 μm to 10 μm, preferably 4 μm to 6 μm; Preferably, the particle diameter D50 of the single crystal positive electrode material is 1 μm to 4 μm, preferably 1.2 μm to 1.8 μm; Preferably, the solid electrolyte material has a particle size D50 of 0.2 μm to 3 μm, preferably 0.5 μm to 1.0 μm; Preferably, the difference between the particle size D50 of the polycrystalline positive electrode material and the particle size D50 of the single crystal positive electrode material is more than or equal to 1 mu m; preferably, the difference between the particle diameter D50 of the single crystal positive electrode material and the particle diameter D50 of the solid electrolyte material is not less than 0.5 μm.
  3. 3. The single crystal-polycrystal composite positive electrode material according to claim 1 or 2, characterized in that the mass ratio of the polycrystal positive electrode material to the single crystal positive electrode material is (2-5): 5-8; Preferably, the mass ratio of the polycrystalline positive electrode material to the solid electrolyte material is 1 (0.2-0.8); Preferably, the mass ratio of the polycrystalline substrate to the ion conductor coating layer is 1 (0.01-0.03).
  4. 4. The single crystal-polycrystalline composite cathode material according to claim 1 or 2, wherein the polycrystalline substrate and single crystal cathode material comprise a ternary cathode material; preferably, the chemical general formula of the ternary positive electrode material is LiNi 1-x-y Co x Mn y O 2 , wherein x is more than or equal to 0.3, y is more than or equal to 0 and less than or equal to 0.3; Preferably, the solid electrolyte material comprises a sulfide solid electrolyte material; Preferably, the ion conductor coating comprises LiNbO 3 and/or LiPO 3 .
  5. 5. The single crystal-polycrystal composite positive electrode material according to claim 1 or 2, further comprising a conductive agent therein; Preferably, the mass ratio of the polycrystalline positive electrode material to the conductive agent is 1 (0.04-0.12); Preferably, the conductive agent includes VGCF.
  6. 6. The single crystal-polycrystal composite positive electrode material according to claim 1 or 2, characterized in that the compacted density of the single crystal-polycrystal composite positive electrode material is 3g/cm 3 or more; preferably, the ion conductivity of the single crystal-polycrystal composite positive electrode material is above 0.6 mS/cm; Preferably, the electron conductivity of the single crystal-polycrystal composite positive electrode material is 0.6mS/cm or more.
  7. 7. A method for producing the single crystal-polycrystal composite positive electrode material according to any one of claims 1 to 6, comprising the steps of: and mixing the monocrystalline cathode material, the polycrystalline cathode material and the solid electrolyte material to obtain the monocrystalline-polycrystalline composite cathode material.
  8. 8. The method according to claim 7, wherein a conductive agent is further added during the mixing.
  9. 9. A solid-state battery positive electrode layer obtained by cold pressing the single crystal-polycrystal composite positive electrode material according to any one of claims 1 to 6.
  10. 10. A solid-state battery characterized in that the solid-state battery comprises a solid-state electrolyte sheet, a negative electrode layer on one side of the solid-state electrolyte sheet, and a solid-state battery positive electrode layer according to claim 9 on the other side.

Description

Single crystal-polycrystal composite positive electrode material, preparation method thereof, solid-state battery positive electrode layer and solid-state battery Technical Field The invention belongs to the technical field of batteries, and relates to a single crystal-polycrystalline composite positive electrode material, a preparation method thereof, a solid-state battery positive electrode layer and a solid-state battery. Background Compared with a liquid battery, the solid battery has the advantage of high safety, the positive electrode material is an important component of the solid battery, the positive electrode of the existing all-solid battery is generally divided into a pure polycrystalline positive electrode system and a pure monocrystalline positive electrode system, wherein the pure polycrystalline positive electrode system takes layered oxide polycrystalline particles as an active material, and is mixed with electrolyte (such as sulfide electrolyte) through ball milling and cold press molding to construct a composite positive electrode, and in order to inhibit interface side reaction of the polycrystalline particles and the electrolyte, a coating layer is often adopted to modify the polycrystalline surface. However, the pure polycrystalline positive electrode system has the following problems that (1) the mechanical stability is poor, the charge-discharge volume expansion of polycrystalline particles is not matched with the deformation of solid electrolyte (large brittleness and low elastic modulus), so that electrode delamination and electrolyte particles are broken, the capacity retention rate is generally lower than 60 percent after 300 times of circulation, (2) interface reaction is intense, transition metal at the crystal boundary of the polycrystalline particles is easy to dissolve out and reacts with the solid electrolyte to generate an insulating product, the interface impedance can reach 5-8 times of the initial value after 100 times of circulation, and (3) the ion transmission is blocked, the thickness of a reaction layer formed by the crystal boundary and the solid electrolyte is increased along with the circulation, for example, the thickness is increased to 50-100nm, so that the reaction layer becomes an ion transmission barrier. Aiming at the problem of severe interface reaction between polycrystal and electrolyte, the pure single crystal positive electrode system adopts single crystal particles without crystal boundary as active materials to reduce reaction sites and match with composite electrolyte to reduce interface impedance. However, the conventional pure single crystal positive electrode system has the following problems that ① interface contact fails, the single crystal surface is smooth, the wettability with solid electrolyte is poor, the physical contact area is lower than that of polycrystal with the same volume, and high stack pressure is required to be applied to maintain a conductive network. ② The cost and the processing difficulty are that the monocrystalline particles are synthesized by sintering at 1050-1100 ℃ to ensure that the cost of the anode is 3-4 times higher than that of a pure polycrystalline system, and the problems of SE agglomeration and uneven particle distribution are easy to occur during cold press molding. In summary, the pure polycrystalline system has low cost but the interface reaction is out of control, the pure monocrystalline system has improved stability but poor contact performance and high cost, and the existing coating and doping technology can only delay the interface reaction and can not solve the problems of poor interface stability, low ion transmission efficiency and high cost, so that the anode material with high interface stability, excellent ion transmission performance and low cost needs to be provided. Disclosure of Invention The invention aims to provide a single crystal-polycrystal composite positive electrode material, a preparation method thereof, a solid battery positive electrode layer and a solid battery, wherein the single crystal-polycrystal composite positive electrode material is subjected to three-level grain composition, and the mass ratio of the single crystal positive electrode material to the polycrystal positive electrode material is controlled, so that single crystal grains form a rigid framework, polycrystal grains and electrolyte fill gaps, the contact area of an active material and the electrolyte is increased, the stacking pressure is reduced, the compaction density is increased, and meanwhile, the problems of poor interface stability, poor multiplying power performance and high cost are solved. In order to achieve the aim of the invention, the invention adopts the following technical scheme: In a first aspect, the present invention provides a single crystal-polycrystalline composite cathode material, wherein the single crystal-polycrystalline composite cathode material comprises a single crystal cathode