ALL-SOLID SECONDARY BATTERY

An all-solid secondary battery including a positive electrode layer including a positive current collector and a positive active material layer on one or more surfaces of the positive current collector is provided. The battery includes a negative electrode layer and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. The positive active material layer includes a composite electrolyte and a lithium-containing sulfide-based positive active material including Li2S and/or a Li2S-containing composite. The composite electrolyte includes a polymer, a lithium salt, and an ionic liquid having a saturated solubility of lithium polysulfide of 5 wt% or less at 25 °C.