A simple, low-temperature route was developed to process bulk solid-state Li-ion batteries employing Al-doped Li7La3Zr2O12 solid electrolyte (thickness: ∼ 0.5mm; 25°C conductivity: ∼ 2×10−4 S cm−1). A composite Cu0.1V2O5–based slurry was directly painted on Li7La3Zr2O12 and dried at 120°C to prepare the cathode film. The opposite side of the electrolyte was subsequently exposed to molten Li to form the anode. The discharge capacity of the solid state battery was 53mAhg−1 (calculated based on the weight of active cathode material) at room temperature with 5μAcm−2 discharging current. Severe capacity decay occurred after the initial discharging. A comparable liquid electrolyte battery was tested at room temperature for comparison and had a much slower decay rate. However, when the operating temperature of the solid state battery was increased to 50°C, the cell performance significantly improved. At 50°C, the battery exhibited 176mAhg−1 initial discharging capacity at 5μAcm−2 current density and 93mAhg−1 initial capacity under a 10μAcm−2 discharging current density. After 20 cycles, the capacity decayed to 68.6mAhg−1 when cycled at a 10μAcm−2 current density. Impedance spectroscopy was used to investigate the interface resistance of the battery at different temperatures. The results indicated that both the cathode and anode interface resistance were dramatically reduced at 50°C. The decrease in interface resistances at elevated temperature is proposed as the main reason for the observed battery performance enhancement.