Crystalline solid solutions of 1:1 Li3PO4/Li4SiO4 were synthesized and tested electrochemically using thin film physical vapor deposited electrodes. After cathode deposition, the electrolyte/cathode structures were annealed at 700 degreesC for 2 h-a process that resulted in cathode crystallization without encouraging deleterious interfacial reactions. Results indicate that the electrolyte functioned well in this configuration. Test cells were taken through multiple charge/discharge cycles at different rates and temperatures and demonstrated a marked enhancement in performance parameters in comparison to previous reports. It is suggested that this material could function well in Li batteries fabricated using proper form factors. (C) 2004 Elsevier B.V. All rights reserved.