Material Development of the Lgps Based Solid Electrolytes — Structure, Conductivity and Battery Characteristics

Lithium superionic conductors, which can be used as solid electrolytes, promise the potential to replace organic liquid electrolytes and thereby improve the safety of next-generation high-energy batteries. Although the advantages of non-flammable solid electrolytes are widely acknowledged, their low ionic conductivities and low chemical and electrochemical stabilities prevent them from being used in practical applications. The new lithium superionic conductor, Li 10 GeP 2 S 12 (LGPS) exhibits an extremely high bulk conductivity of over 10 -2 S cm -1 at room temperature (27 °C), and is a potential electrolyte candidate for an all solid-state battery [1]. In order to explore the material variety of the LGPS based electrolytes, solid solutions of the pseudo binary Li 4 GeS 4 – Li 3 PS 4 system were investigated. In addition, the new material systems were synthesized with the cation and/or anion substitutions (Si, Ge, Sn, O etc). The solid solution was synthesized for the LGPS parent phase in the binary system, and the conductivity varied with the lithium composition. The structures were determined by X-ray and neutron diffraction analyses, and the relationship between the ionic conduction and structures was clarified. The ionic conductivity and electrochemical stability varied with the compositions examined by the cation and/or anion substitutions. Battery performances using these LGPS systems were investigated. Based on the materials varieties and the battery performances using the LGPS electrolytes, the advantages of the all solid-state batteries will be discussed. Reference [1] N. Kamaya et al., Nat Mater , 10 , 682-686 (2011).