Liquid Alloy Enabled Solid‐State Batteries for Conformal Electrode–Electrolyte Interfaces

Abstract

Recent research efforts on solid-state alkali-metal batteries are pushing the limit of energy density to a higher level. However, the development of solid-state batteries is still hindered by many intrinsic limitations, among which the incompatibility between the solid electrolyte and the metal anode is a critical issue attracting massive research attention. A Na–K liquid alloy electrode is designed to form a conformal electrode–electrolyte interface with a solid electrolyte. Much enhanced electrode–electrolyte interfacial contact electrically and physically is observed with liquid metal anodes than solid alkali metals on solid electrolytes. Symmetric cells of the liquid metal electrolytes show much lower overpotential as well as better cyclability than the alkali-metal electrodes. Excellent cyclability over 500 cycles with reasonable capacity decay and good rate performance of full cells with the sodium rhodizonate and a ferricyanide potassium-ion cathode are both achieved. By adjusting salt and filler species in the polymer electrolyte, the wettability of liquid metal on the electrolyte can be further improved, and the raised ionic conductivity can further improve the battery performance of such a design.