Electrostatic spray deposition (ESD) was employed to prepare thin layers of Li 1.2 Mn 2 O 4 (nominal composition) and BPO 4 :0.035Li 2 O for all-solid-state thin film lithium-ion batteries. The relationships between layer morphologies and deposition conditions such as solvent composition of the precursor solutions and substrate temperature were investigated. It was found that a low substrate temperature and/or high boiling point of the solvent may lead to a relatively dense structure. Reticular porous structures are formed, if films were deposited at 250°C and a mixture of 85 vol.% butyl carbitol and 15 vol.% ethanol was used as the solvent. The Li 1.2 Mn 2 O 4 layers, formed in the 250–400°C temperature range, were amorphous or micro-crystalline. After annealing beyond 600 °C, they could be crystallized into a spinel-structured material. Glassy BPO 4 :0.035Li 2 O layers could fill the pores of porous Li 1.2 Mn 2 O 4 layers to form a dense intermediate electrolyte layer. Thin-film rocking-chair batteries, Li 1.2 Mn 2 O 4 |BPO 4 :0.035Li 2 O|Li 1.2 Mn 2 O 4 |Al, were prepared and revealed an open-circuit voltage of about 1.2 V after charging.