Two Dimensional Li Diffusion in Ion-Conductive Lithium Lanthanum Titanates

Abstract

Developing energy storage systems is an indispensable and keyfactor in realizing a sustainable society. Although a pumped storage hydroelectric power station converts gravitational to kinetic energy via the movement of water and constitutes a reliable secondary battery system, such a system is a huge facility covering a vast area. By substituting the less dense substance Li for water and replacing the stronger chemical interaction of Li for the weaker gravitational force, a Li-ion battery attains high energy density. 1,2 Currently, most Li-ion batteries use a combustible liquid electrolyte solution, which requires them to be securely and heavily sealed in small packages. The use of a liquid electrolyte in batteries not only creates safety issues but also leads to degradation due to repetitive cycling. An irreversible reaction with Li is reported to happen at the anode surface, known as the solid electrolyte interface (SEI) region. 3 Preventing the loss of active Li at the SEI and eliminating the combustible liquid from the battery, will open the door to the development of large size, high-capacity batteries. For thisreason, researchers have devoted their attentions to incorporating a solid electrolyte into Li-ion battery systems. We have focused our efforts on studying the fundamental mechanism of Li diffusion in a particular solid electrolyte system, the lithium lanthanum titanates (LLTO), which show a high conductivity of 10 −3 Sc m −1 . 4,5