Positive electrode for secondary battery and nonaqueous electrolyte secondary battery

Abstract

A positive electrode for a secondary battery according to an embodiment of the present disclosure comprises a positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the positive electrode current collector. The positive electrode mixture layer includes a first positive electrode active material and a second positive electrode active material having a volume-based median diameter D50 smaller than that of the first positive electrode active material. At least a portion of the surface of the first positive electrode active material is covered with a specific coating material, and the surface of the second positive electrode active material is not covered with the specific coating material. When a volume-based median diameter D50 of the first positive electrode active material is defined as D1 (µm) and a volume-based median diameter D50 of the second positive electrode active material is defined as D2 (µm), D1 and D2 satisfy the relationship 2.0≤D1 / D2≤15.0.

Claims

1. A positive electrode current collector and a positive electrode mixture layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode mixture layer comprises a first positive electrode active material and a second positive electrode active material having a volume-based median diameter D50 smaller than that of the first positive electrode active material, the surface of the first positive electrode active material is at least partially covered with a coating material, and the surface of the second positive electrode active material is not covered with the coating material, the coating material comprises Li, Ti, M1, and X, M1 is at least one selected from the group consisting of Be, Mg, Ca, Sr, Ba, Sc, Y, Al, Ga, In, Zr, and Sn, and X is at least one selected from the group consisting of F, Cl, Br, and I. A positive electrode for a secondary battery, wherein when the volume-based median diameter D50 of the first positive electrode active material is D1 (μm) and the volume-based median diameter D50 of the second positive electrode active material is D2 (μm), D1 and D2 satisfy the relationship 2.0 ≤ D1 / D2 ≤ 15.

0.

2. The positive electrode for a secondary battery according to claim 1, wherein when the content of the first positive electrode active material is W1 (mg) and the content of the second positive electrode active material is W2 (mg), W1 and W2 satisfy the relationship W1:W2 = 1:9 to 9:

1.

3. The positive electrode for a secondary battery according to claim 1, wherein D1 satisfies the relationship 8 μm ≤ D1 ≤ 17 μm.

4. The positive electrode for a secondary battery according to claim 3, wherein D2 satisfies the relationship 2 μm ≤ D2 ≤ 6 μm.

5. The positive electrode for a secondary battery according to claim 1, wherein the second positive electrode active material is a secondary particle formed by the aggregation of large primary particles with an average particle size of 0.5 μm or more, or a particle composed of substantially single particles.

6. The positive electrode for a secondary battery according to claim 1, wherein at least a portion of the surface of the first positive electrode active material is covered with the coating material in an amount of 0.1% by mass or more and 3.0% by mass or less, when the first positive electrode active material is considered to be 100% by mass.

7. The positive electrode for a secondary battery according to claim 1, wherein the average thickness of the coating material is 20 nm or more and 300 nm or less.

8. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode is the positive electrode for a secondary battery described in any one of claims 1 to 7.

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