Ceramic Li Ion Electrolytes for Next Generation Solid-State Li Ion Batteries

At present, there is a growing interest in the development of safe and low-cost all-solid-state Li ion batteries for transport applications  due to their higher practical volumetric and gravimetric energy densities compared to other known secondary batteries. The commercial Li ion battery utilizes LiPF₆ dissolved organic polymer as an electrolyte, graphite anode and LiCoO₂ electrode that exhibit several issues including safety, low energy density and inadequate chemical stability and durability. To this end, numerous solid-state Li ion electrolytes such as two-dimensional layered structures Li-beta alumina and Li₃N, and three-dimensional structured Li₄SiO₄, Li_2+2xZn_1-xGeO₄, Li_1+xTi_2−xAl_xP₃O₁₂, (Li,Ln)TiO₃ and Li₅La₃M₂O₁₂ (M = Nb, Ta) have been studied for all-solid-state Li ion batteries. Among these materials, garnet-like oxides have recently gained much attention because of their high Li ion conductivity, low electronic conductivity at high Li activity, and high electrochemical stability window, up to 6 V/Li. The lithium stuffing in the parent garnet-type Li₅La₃M₂O₁₂ increases Li ion conduction. For example, x = 0.75 members of Li_5+2xLa₃M_2-xY_xO₁₂ show the highest Li ion conductivity of 10^-4 Scm^-1 at room temperature.  In this talk, role of crystal chemistry on Li ion conductivity of the garnet-type solid Li ion electrolytes will be presented.