Method for producing cathode, and method for producing oxide solid-state battery

A method for producing an oxide solid-state battery, the method comprising:

• obtaining a lithium containing composite oxide that has a layered rock-salt structure;
• determining the melting point of the lithium containing composite oxide,
• acid-treating particles of the lithium containing composite oxide;
• obtaining a lithium salt whose melting point is lower than that of the lithium containing composite oxide;
• obtaining a mixture by mixing the acid-treated particles with the lithium salt;
• obtaining a layered body by layering a layer that comprises the mixture, and a layer of an oxide solid electrolyte;
• determining a reaction temperature at which the mixture reacts with the oxide solid electrolyte;
• selecting a heating temperature that is greater than or equal to the melting point of the lithium salt and lower than the reaction temperature;
• and
• heating the layered body at the temperature, and sintering the mixture on a surface of the layer of the oxide solid electrolyte,
• wherein the lithium salt is a combination of lithium formate and lithium acetate.