An all solid-state high temperature cell is described using a solid solution of lithium germanium oxide (Li4GeO4) and lithium vanadium oxide (Li3VO4) with a general formula, Li3.6Ge0.6V0.4O4, as the lithium ion conducting solid electrolyte. The cyclic voltammetric experiments with the solid electrolyte exhibited the reversible deposition of lithium metal at platinum and gold working electrodes at potentials below ca. 0.5 V vs. the lithium-aluminum reference and showed the solid electrolyte to be electrochemically stable toward any oxidation up to a potential of ca. 4.5 V vs. a lithium-aluminum reference electrode. The cells employed a lithium-aluminum alloy as the anode and a chemical vapor deposited thin film of titanium disulfide as the cathode, and exhibited an open-circuit potential of ca. 2.1 V at 300-degrees-C. The cells exhibited excellent high rate capabilities and were discharged at current densities up to 100 mA/cm2.