Sulfide-Based Solid Electrolyte Particles

A sulfide-based solid electrolyte particle having a crystal phase of a cubic argyrodite-type crystal structure composed of Li, P, S and a halogen (Ha), wherein good contact between the sulfide-based solid electrolyte particles and positive or negative electrode active material particles is secured and improvements in the rate characteristic and the cycle characteristic are attained. The ratio (Z/Z) of an element ratio Zof the halogen (Ha) at the position of 5 nm in depth from the particle surface to an element ratio Zof the halogen (Ha) at the position of 100 nm in depth from the particle surface is 0.5 or lower and the ratio (Z/Z) of an element ratio Zof oxygen to the total Zof element ratios of P, S, O, and the halogen (Ha) at the position of 5 nm in depth from the particle surface is 0.5 or higher, as measured by XPS.