High Li-Ion Conductivity in Li{N(SO<sub>2</sub>F)<sub>2</sub>}(NCCH<sub>2</sub>CH<sub>2</sub>CN)<sub>2</sub> Molecular Crystal
K. Tanaka, Yusuke Tago, Mitsuru Kondo, Yuki Watanabe, Kazunori Nishio, Taro Hitosugi, Makoto Moriya
Abstract
There is an urgent need to develop solid electrolytes based on organic molecular crystals for application in energy devices. However, the quest for molecular crystals with high Li-ion conductivity is still in its infancy. In this study, the high Li-ion conductivity of a Li{N(SO2F)2}(NCCH2CH2CN)2 molecular crystal is reported. The crystal shows a Li-ion conductivity of 1 × 10–4 S cm–1 at 30 °C and 1 × 10–5 S cm–1 at −20 °C, with a low activation energy of 28 kJ mol–1. The conductivity at 30 °C is one of the highest values attainable by molecular crystals, whereas that at −20 °C is approximately 2 orders of magnitude higher than previously reported values. Furthermore, the all-solid-state Li-battery fabricated using this solid electrolyte demonstrates stable cycling, thereby maintaining 90% of the initial capacity after 100 charge–discharge cycles. The finding of high Li-ion conductivity in molecular crystals paves the way for their application in all-solid-state Li-batteries.