Co-Intercalation of Tetrahydrofuran and Propylene Carbonate with Alkali Metals in β-ZrNCl Layer Structured Crystal

Abstract

Abstract Alkali metal intercalation compounds of β-ZrNCl were prepared by both chemical and electrochemical processes in tetrahydrofuran (THF) and propylene carbonate (PC), used as solvents. Among the six combinations of alkali metals (Li, Na, and K) with THF and PC, only the Na–THF system did not form a co-intercalation phase. In the other systems, the solvent molecules co-intercalated with alkali metals in mono- and double layer arrangements between the chloride layers of β-ZrNCl, the structures of which were estimated from one-dimensional electron distribution maps along the direction normal to the basal plane. The electrochemical characteristics of β-ZrNCl, used as the cathode of a lithium battery, were greatly influenced by the electrolyte solvent used. The co-intercalation mechanisms are discussed in terms of the energetics of the solvation of alkali metal ions with polar molecules and an expansion of the β-ZrNCl interlayers.