An enhanced interface between garnet solid electrolyte and lithium through multifunctional lithium titanate anode-additive for solid-state lithium batteries

Garnet-structured solid-state electrolytes are getting considerable attention due to their high figure of merit over other inorganic solid-state electrolytes. The high lithium-ion conductivity and exceptional stability with metallic lithium over a wide voltage window open the door for the practical realization of an all-solid-state battery. However, the lithiophobic nature of garnet solid electrolytes creates huge interface resistance, which restricts achieving high critical current density. Herein a multifunctional composite anode containing lithium metal and lithium titanate (Li4Ti5O12) is introduced to tackle the interface challenges with the garnet solid electrolyte. The partial reduction of titanium in the composite enhances the electronic conductivity of the anode, and the intrinsic structural advantages of lithium titanate are expected to accommodate volume change as well. The prepared symmetric cell with the composite anode is found to have a minimal areal-specific resistance of 27 Ω cm2, while that of the pristine lithium anode is 249 Ω cm2. The cell has also run with a better critical current density (0.35 mA cm−2) than the pristine lithium (0.15 mA cm−2). A full cell study with a lithium iron phosphate cathode offers a capacity of 145 mAh g−1 at 0.2 C and runs for 100 cycles at 1 C with minimum capacity loss.