PURPOSE: To obtain a super-ion conductive material having high electrical conductivity and giving a solid cell having high energy density, by mixing AgI with a mixture of Ag2S and Li2O, and calcining the mixture in vacuum.

CONSTITUTION: 1mol of AgI is mixed with 1mol of a mixture of Ag2S and Li2O, and sealed in evacuated pyrex tube. Sulfur powder for preventing the decomposition of the reaction product is also sealed in the pyrex tube at a position separated from the mixture. The mixture in the pyrex tube is heated and sintered to obtain the objective super-ion conductive material of formula (0≤x<1). A solid cell having an open-circuit voltage of about 2.2V, high energy- density and high reliability can be produced by using the super-ion conductive material as the electrolyte, and filling the electrolyte between the negative electrode 1 composed of lithium and the positive electrode 3 composed of iodine, bromine, chlorine, etc.