Recent Advancements in Li-Ion Conductors for All-Solid-State Li-Ion Batteries

Inorganic solid lithium ion conductors are potential candidates as replacement for conventional organic electrolytes for safety concerns. However, achieving a Li-ion conductivity comparable to that in existing liquid electrolytes (>1 mS cm(-1)) remains a challenge in solid-state electrolytes. One of the approaches for achieving a desirable conductivity is doping of various elements into the lattice framework. Our discussion on the structure and conductivity of crystalline Li-ion conductors includes description of NAtrium Super Ionic CONductor (NASICON)-type conductors, garnet-type conductors, perovskite-type conductors, and Lithium Super Ionic CONductor (LISICON)-type conductors. Moreover, we discuss various strategies currently used to enhance ionic conductivity, including theoretical approaches, ultimately optimizing the electrolyte/electrode interface and improving cell performance.