A lithium-containing oxide having a cationic-disordered rock salt-type structure,

An electrolyte composition contains an ion conductive inorganic solid electrolyte, a polymer having an ability to preferentially conduct metal ions, and an ionic liquid.

A cathode active material for lithium secondary batteries contains secondary particles which are an aggregate of primary particles, in which the cathode active material for lithium secondary batteries has a layered structure, the cathode active material fo...