High Specific Energy Li7La3Zr2O12 Solid Electrolyte Based Thermal Battery

Garnet-type Ta-doped Li7La3Zr2O12 (LLZTO) solid electrolyte has been widely investigated for secondary Li ionic or metal batteries at ambient temperature. Because of the increasing ionic conductivity of LLZTO with temperature, we applied the LLZTO solid electrolyte to thermal battery working at 550 °C. The LLZTO presents ultrahigh specific energy as the discharge specific energy and specific power is 605 W h kg−1 and 2.74 kW kg−1 at 100 mA cm−2 with a cut-off voltage of 1.8 V, respectively. This is larger than the LiF–LiCl-LiBr electrolyte which is commonly used in thermal battery with a specific energy of 514 W h kg−1. The internal resistance of the single cell reaches 0.65 Ω, but the specific energy remains at about 400 W h kg−1 as the current density increases to 400 mA cm−2. We report the application of LLZTO in thermal battery with high specific energy, large current, and high voltage discharge for the first time, broadening the application range of solid electrolytes.