Superionic glasses and glass–ceramics in the Li2S–P2S5 system for all-solid-state lithium secondary batteries

Abstract

Glass-based superionic materials are among the most promising candidates for inorganic solid electrolytes applicable to all-solid-state battery systems. We have developed a variety of sulfide-based glassy electrolyte systems. This paper reviews the advantages and development of sulfide-based superionic glasses and glass–ceramics, and the application of these materials to all-solid-state battery systems. The most important advantage of glass-based electrolytes is the fact that the superionic conducting crystals are easily formed as a metastable phase from glassy materials. The heating of Li2S–P2S5 glasses results in the formation of superionic Li7P3S11 glass–ceramic. The conductivity was improved up to 5×10−3Scm−1 at room temperature by doping with other elements and optimization of the glass formation and crystallization processes. The application of these glass-based solid electrolytes to a variety of all-solid-state lithium secondary batteries is also reported, using not only typical electrode active materials such as LiCoO2 and Li4Ti5O12, but also materials that are difficult to use in liquid electrolyte batteries, such as elemental sulfur.