The construction of concentration gradient inducing low resistance for Li7La3Zr2O12-based thermal battery

Abstract

Ta-doped Li7La3Zr2O12 (LLZTO) electrolytes not only show considerable potentials in solid-state Li metal batteries, but also display great possibility in thermal battery working at elevated temperature with high security. However, the great resistance of the single cell has hindered its practical application for the large interfacial resistance and high Li+ transport pressure. Herein, a new effective approach to construct intense interface and distinct concentration gradient of O2– and Cl- through pre-discharge state at small current (PDS) was successfully employed to decline the resistance of the LLZTO-based thermal battery under thermal and electric field. The formed intense interface is conductive under the thermal field than the pristine poor contact at the interface. The obtained significant and distinct concentration gradient of O2– and Cl- under the joint function of thermal and electric field achieves larger effective charge transport after PDS, suggesting lower polarization and resistance of the single cell owing to the relaxing burden of Li+. Consequently, the resistance of the single cell decreases to 2.4 Ω from 3.7 Ω, coming with larger specific energy at 500 °C (from 444 Wh kg−1 to 1038 Wh kg−1). This work provides a facile strategy to decline the resistance of the battery through the construction of concentration gradient, which is also promising to be used for battery whose materials are sensitive to electric or thermal field.