Positive electrode material and method for preparing the same, positive electrode sheet, and all-solid-state battery

Abstract

The present application provides a positive electrode material, a method for preparing the same, a positive electrode sheet, and a all-solid-state battery. The positive electrode material includes a lithium-rich manganese-based positive electrode active material and a coating layer covering at least a part of the surface of the lithium-rich manganese-based positive electrode active material. The molecular formula of the lithium-rich manganese-based positive electrode active material is xLi 2-α MnO3·(1-x)Li 1-β Ni a Co b Mn c O 2-γ where a + b + c = 1, 0 < α + β ≤ 0.2, 0 < γ ≤ 0.1, 0 < x < 1. The coating layer satisfies the following formulas 1 and 2: 0.5×10 -3 S / cm ≤ T ≤ 5×10 -3 S / cm (Formula 1), H ≤ 10 -9 S / cm (Formula 2), where T is the ionic conductivity of the coating layer and H is the electronic conductivity of the coating layer. The positive electrode material according to the present application solves the problem of low initial coulombic efficiency of the lithium-rich manganese-based positive electrode material and improves the interface ion transfer efficiency and the stability of the positive electrode material.

Claims

1. A positive electrode material comprising a lithium-rich manganese-based positive electrode active material and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the molecular formula of the lithium-rich manganese-based positive electrode active material is xLi ２－α MnO ３ (1-x)Li １－β Ni ａ Co ｂ Mn ｃ O ２－γ Therefore, a + b + c = 1, 0 < α + β ≤ 0.2, 0 < γ ≤ 0.1, 0 < x < 1, The aforementioned coating layer satisfies the following equations 1 and 2, 0.5×10 －３ S / cm≦T≦5×10 －３ S / cm Formula 1 H≦10 －９ S / cm Formula 2 A positive electrode material characterized in that T is the ionic conductivity of the coating layer and H is the electronic electrical conductivity of the coating layer.

2. The positive electrode material according to claim 1, characterized in that the coating layer includes a halide solid electrolyte material.

3. The chemical composition of the halogen solid electrolyte material is Li ｄ MX ｅ The positive electrode material according to claim 2, wherein M is one or more of Ho, Y, Er, and Yb, X is Cl or Br, and 0 < d ≤ 10 and 1 ≤ e ≤ 13.

4. The positive electrode material according to claim 2 or 3, characterized in that the thickness of the coating layer is in the nanometer range.

5. The positive electrode material according to claim 4, characterized in that the thickness of the coating layer is 5-80 nm.

6. The positive electrode material according to claim 2 or 3, characterized in that the mass ratio of the coating layer in the positive electrode material is 0.1% to 0.5%.

7. The positive electrode material according to any one of claims 1 to 6, characterized in that the coating layer is dense and has no pores, or has pores with a diameter of 5 nm or less.

8. The specific surface area of ​​the aforementioned positive electrode material is 0.5–1.3 m². ２ / g, The positive electrode material according to any one of claims 1 to 7, characterized in that the size of the single crystal particles of the positive electrode material is 0.7 to 1.5 μm, and the particle size of the positive electrode material is 4 to 6 μm.

9. A method for preparing a positive electrode material according to any one of claims 1 to 8, Step 1) involves mixing the oxide of M, ammonium salt, lithium salt, and HX solution, stirring at 20-90°C, and obtaining a mixture with a pH of 1-3. Step 2) involves immersing a lithium-rich manganese-based material in the aforementioned mixture, allowing it to stand for 1-5 minutes, and then drying it to obtain a precursor. Step 3) includes heating the precursor to 400-600°C at a heating rate of 1-10°C / min under a protective atmosphere, and maintaining the temperature for 4-6 hours to obtain the cathode material. A preparation method characterized in that M is one or more of Ho, Y, Er, and Yb, and X is Cl or Br.

10. The general formula for the lithium-rich manganese material is xLi ２ MnO ３ ・(1-x)LiNi ａ Co ｂ Mn ｃ O ２ The preparation method according to claim 9, characterized in that a + b + c = 1, 0 ≤ a ≤ 1, 0 ≤ b ≤ 1, 0 ≤ c ≤ 1, and 0 < x < 1.

11. The preparation method according to claim 10, characterized in that the solid-liquid ratio of the lithium-rich manganese material to the mixed solution is (50-100) g: (0.1-1) L.

12. A positive electrode sheet comprising a positive electrode active layer and a current collector, wherein the positive electrode active layer comprises a positive electrode material, a sulfide solid electrolyte, a conductive agent, and a binder as described in any one of claims 1 to 8.

13. A solid-state battery, characterized by comprising the positive electrode sheet described in claim 12.

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