The positive electrode active material of the present disclosure includes a complex oxide represented by a formula (1): LiNi.sub.xMe.sub.1-xO.sub.2 as a main component and contains water generated during heating at 300° C. in Karl Fischer titration in an amount of 317.5 ppm by mass or less. Here, x satisfies 0.5 ≤ x ≤ 1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.

The positive electrode active material of the present disclosure includes a complex oxide represented by a formula (1): LiNi.sub.xMe.sub.1-xO.sub.2 as a main component and contains water generated during heating at 300° C. in Karl Fischer titration in an amount of 317.5 ppm by mass or less. Here, x satisfies 0.5 ≤ x ≤ 1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.

A solid electrolyte material includes a first crystal phase. The first crystal phase has a composition that is deficient in Li as compared with a composition represented by the following composition formula (1).
Li.sub.3Y.sub.1Cl.sub.6  formula (1)

A solid electrolyte material includes a first crystal phase. The first crystal phase has a composition that is deficient in Li as compared with a composition represented by the following composition formula (1).
Li.sub.3Y.sub.1Cl.sub.6  formula (1)

The solid electrolyte material of the present disclosure includes Li, Sc, and Cl. In an X-ray diffraction pattern of the solid electrolyte material obtained using Cu-Kα rays, there are at least two peaks in a diffraction angle 2θ range of 27° or more and 36° or less, and a peak with the highest intensity within the diffraction angle 2θ range of 27° or more and 36° or less has a half value width of 0.5° or less.

The positive electrode active material of the present disclosure includes a complex oxide represented by formula (1): LiNi.sub.xMe.sub.1-xO.sub.2 as a main component and has a hydrogen element content of 238.8 ppm by mass or less. Here, x satisfies 0.5≤x≤1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.

The positive electrode active material of the present disclosure includes a complex oxide represented by formula (1): LiNi.sub.xMe.sub.1-xO.sub.2 as a main component and has a hydrogen element content of 238.8 ppm by mass or less. Here, x satisfies 0.5≤x≤1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.

The positive electrode active material of the present disclosure includes a complex oxide represented by a formula (1): LiNi.sub.xMe.sub.1-xO.sub.2 as a main component and contains water in an amount of 2.9 ppm by mass or more and 44.7 ppm by mass or less. Here, x satisfies 0.5≤x≤1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.

The positive electrode active material of the present disclosure includes a complex oxide represented by a formula (1): LiNi.sub.xMe.sub.1-xO.sub.2 as a main component and contains water in an amount of 2.9 ppm by mass or more and 44.7 ppm by mass or less. Here, x satisfies 0.5≤x≤1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.

Provided is a positive electrode material which further improves charge/discharge efficiency. The positive electrode material according to the present disclosure includes a positive electrode active material and a first solid electrolyte material. The first solid electrolyte material includes Li, M, and X, and does not include sulfur. M is at least one selected from the group consisting of metalloid elements and metal elements other than Li. X is at least one selected from the group consisting of Cl, Br, and I. The positive electrode active material includes a metal oxyfluoride.