Dense lithium lanthanum titanate, (Li,La)TiO 3, pellets were prepared using a spark-plasma sintering (SPS) method. The obtained (Li,La)TiO 3 pellets showed relatively high lithium ion conductivity, typically 10 −3 S cm −1 at 22 °C, with an activation energy of 30.1 kJ mol −1. Lithium manganese oxide, LiMn 2O 4, was deposited on (Li,La)TiO 3 pellets by an electrostatic spray deposition (ESD) method at 400 °C without significant formation of by-products at the interface (Li,La)TiO 3/LiMn 2O 4. An all-solid-state battery system, LiMn 2O 4/(Li,La)TiO 3/SPE/Li, where a solid polymer electrolyte (SPE) was sandwiched between (Li,La)TiO 3 and Li, showed good charge/discharge characteristics over 100 cycles at 60 °C.