Lithium Ionic Conductor Thio-LISICON: The Li[sub 2]S-GeS[sub 2]-P[sub 2]S[sub 5] System

The new crystalline material family, lithium superionic conductor (thio-LISICON), was found in the system. The solid solution member in shows the highest conductivity of at 25°C of any sintered ceramic, together with negligible electronic conductivity, high electrochemical stability, no reaction with lithium metal, and no phase transition up to 500°C. Its material design concepts of changing constituent ions with various ionic radii, valence, and polarizability are described.