Composite particles for all-solid-state secondary battery electrode and method of producing same, electrode for all-solid-state secondary battery, and all-solid-state secondary battery

1. Composite particles for an all-solid-state secondary battery electrode comprising an electrode active material, a binder, and an inorganic solid electrolyte, wherein

the inorganic solid electrolyte is distributed more in an outer part than in an inner part, and

the composite particles for an all-solid-state secondary battery electrode have a volume-average particle diameter of not less than 5 μm and not more than 90 μm, wherein

a degree of uneven distribution of the inorganic solid electrolyte in the composite particles for an all-solid-state secondary battery electrode is 0.01 or more, where the degree of uneven distribution of the inorganic solid electrolyte indicates, in a cross-section of a composite particle, a ratio S1/S2 of an average value S1 of the amount of the inorganic solid electrolyte contained per unit area in the inner part relative to an average value S2 of the amount of the inorganic solid electrolyte contained per unit area in the cross-section, where the inner part of a composite particle is a region for which the distance in a radial direction of the composite particle from the center of the composite particle is not more than half of the distance in the radial direction from the center of the composite particle to the circumferential surface of the composite particle, and the outer part is a part positioned further outward than the inner part in the radial direction.

2. The composite particles for an all-solid-state secondary battery electrode according to claim 1 , wherein a ratio of a number-average particle diameter of the inorganic solid electrolyte relative to a number-average particle diameter of the electrode active material is not less than 0.08 and not more than 0.8.

3. The composite particles for an all-solid-state secondary battery electrode according to claim 1 , further comprising a polymeric solid electrolyte.

4. An electrode for an all-solid-state secondary battery comprising an electrode mixed material layer containing the composite particles for an all-solid-state secondary battery electrode according to claim 1 .

5. An all-solid-state secondary battery comprising a positive electrode, a solid electrolyte layer, and a negative electrode, wherein

at least one of the positive electrode and the negative electrode is the electrode for an all-solid-state secondary battery according to claim 4 .

6. A method of producing composite particles for an all-solid- state secondary battery electrode, comprising:

granulating a slurry composition containing an electrode active material and a binder to obtain base particles; and

externally adding an inorganic solid electrolyte to the base particles, wherein

the composite particles comprise the electrode active material, the binder, and the inorganic solid electrolyte, wherein

the inorganic solid electrolyte is distributed more in an outer part than in an inner part, and

the composite particles for an all-solid-state secondary battery electrode have a volume-average particle diameter of not less than 5 μm and not more than 90 μm, where the inner part of a composite particle is a region for which the distance in a radial direction of the composite particle from the center of the composite particle is not more than half of the distance in the radial direction from the center of the composite particle to the circumferential surface of the composite particle, and the outer part is a part positioned further outward than the inner part in the radial direction.

7. The method of producing composite particles for an all-solid-state secondary battery electrode according to claim 6 , wherein the slurry composition is granulated in an environment having a dew point of 0° C. or higher.