(Invited) Interface Engineered Lithium Garnets for Lithium-Metal Batteries

Abstract

Inorganic solid fast Li+ conductors based batteries are expected to overcome the limitations caused by the safety concerns of flammable organic electrolytes based Li+ batteries. Garnet structured solid electrolytes meet the requirements of being mechanically robust, display high ionic conductivities at room temperature, have large electrochemical window and more importantly few lithium garnets are electrochemically stable when in contact with metallic lithium [1]. However, all-solid-state Li metal batteries based on lithium garnet solid electrolytes have challenges in realizing high practical performances at room temperature due to their high electrode/electrolyte interfacial resistances, formation of reaction product layers at the interfaces and dendrite formation through the grain boundaries. Onset of lithium dendrite within the electrolyte on repeated cycling at high current densities could be fatal for lithium metal batteries. Homogeneous current distributions at the Li-electrolyte interface along with the synthesis of highly dense solid electrolyte are significantly vital to ensure the safe usage. Hence, it is of utmost importance to provide a favorable contact between Li metal and lithium garnet electrolyte to reduce the interfacial resistance and remove inhomogeneous current distribution. The surface modifications at Li/solid electrolyte interface will be a useful technique to improve the cycle stability and rate capability of charge discharge reaction. However, negating interfacial resistance and the reaction product layer at the cathode-lithium garnet electrolyte interface is still a challenge. The salient features of various strategies utilized to enhance the room temperature performance of Li metal battery based on garnet structured solid electrolyte will be discussed.