A low resistance and stable lithium-garnet electrolyte interface enabled by a multifunctional anode additive for solid-state lithium batteries

Solid-state batteries (SSBs) have attracted considerable attention due to their high intrinsic stability and theoretical energy density. As the core part, garnet electrolyte has been extensively investigated due to its high lithium-ion conductivity, wide electrochemical potential window, and easy synthesis. However, the poor and electrochemically unstable interfacial contact between the electrolyte and lithium anode greatly impedes the practical use of garnet based SSBs. Here, we report that such an interface challenge can be perfectly tackled by introducing multifunctional Li0.3La0.5TiO3 (LLTO) as an additive into the lithium anode. The limited reaction between the LLTO and lithium effectively changes the physical properties of the lithium anode, making it perfectly compatible with the garnet surface, and consequently significantly decreasing the interfacial resistance from 200 to only 48 Ω cm2 and greatly improving the interface stability and avoiding dendrite formation. Interestingly, LLTO provides additional lithium storage, and the close interface contact and the high lithium-ion conductivity of LLTO ensure high rate performance. Consequently, the symmetrical cell runs stably at 0.1 mA cm-2 for 400 h without obvious degradation. The SSB assembled with the LiFePO4 cathode and Li-LLTO composite anode demonstrates a specific capacity of 147 mA h g-1 and remarkable cycling stability with only 10% capacity decay over 700 cycles at 1C.