Electrode and solid electrolyte thin films for secondary lithium-ion batteries

Electrostatic spray deposition (ESD) was employed to prepare thin layers of Li1.2Mn2O4 (nominal composition) and BPO4:0.035Li2O 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 Li1.2Mn2O4 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 BPO4:0.035Li2O layers could fill the pores of porous Li1.2Mn2O4 layers to form a dense intermediate electrolyte layer. Thin-film rocking-chair batteries, Li1.2Mn2O4BPO4:0.035Li2OLi1.2Mn2O4Al, were prepared and revealed an open-circuit voltage of about 1.2 V after charging.