Highly stable all-solid-state batteries with Li–LTO composite anode

Abstract

Garnet-structured solid electrolytes have been widely examined owing to their good stability with metallic lithium, wide electrochemical potential window, high lithium ionic conductivity, and easy synthesis. One of the primary challenges in establishing solid-state electrolytes is the high resistance arising from the poor contact between the rigid solid–solid type electrode–electrolyte interface, which limits efficient battery operation. To address these challenges, we demonstrate the potential of a lithium–lithium titanate (Li₄Ti₅O₁₂; Li–LTO) composite anode for use as an alternative to the metallic lithium anode in all-solid-state batteries. The reaction that takes place between the lithium metal and lithium titanate changes the physical properties of the anode and makes it physically and electrochemically compatible with the garnet solid electrolyte. The wettability of the anode with garnet electrolyte is effectively enhanced by partial titanium reduction that occurs in the composite of Li–LTO. As a result, there is a drastic decrease in the areal-specific resistance from 371 to 21 Ω cm² for the pure metallic lithium anode and composite anode, respectively. The symmetric cell with composite anode demonstrated a high critical current density of 0.8 mA cm⁻². The cycling stability of the composite anode was illustrated by symmetric cell cycling for 3000 hours at 0.1 mA cm⁻² without a short circuit. The full cell with Li–LTO composite anode and lithium iron phosphate cathode displays stable cycling performance with good capacity retention.