Comprehending garnet solid electrolytes and interfaces in all-solid lithium-ion batteries

All-solid-state batteries using solid electrolytes are projected as an ideal solution towards next-generation energy storage applications, specifically in the automotive sectors. In this context, solid electrolytes are very critical in reaching higher energy density (e.g., >500 Wh. kg−1) with the possibility of employing lithium metal anode without any dendrite formation. Various materials explored as solid electrolytes until now include inorganic (sulfides, oxides, garnets, argyrodites etc.), polymer and composite polymer electrolytes with adequate Li + conductivity. An in-depth analysis of the solid-state systems led to the existence of many unexplored areas and multiple challenges to be resolved for commercialization. The focus of this review is to critically analyze and compare different electrolytes concerning various performance characteristics such as ionic conductivity, stability, and polarization and converges to the viable garnet systems. The review also highlights the significant issues, such as interfacial, mechanical, and electrochemical stabilities associated with solid electrolytes when assembled as solid battery devices, along with the projected strategies. Even though the solid electrolytes can be produced with Li conductivity of as high as 0.1 S cm−1, adapting them for all-solid-state batteries for automotive applications is possible only when the electrode-electrolyte interfacial issues are resolved, and economically viable large-scale thin film manufacturing is established.