Magnetic bistable organic ionic plastic crystal with room temperature ion conductivity comparable to NASICON and superionic conduction in a broad temperature window

摘要

Organic ion plastic crystals (OIPCs) show promising applications in various all solid-state electrochemical energy storage devices. In this regard, superionic conducting OIPCs with a broad temperature window are highly in demand. Herein, we report an OIPC, [DEIm][Ni(mnt)2] (1; DEIm+ = 1,3-diethyl-1H-imidazolium and mnt2− = maleonitriledithiolate), showing crystal–crystal and crystal–plastic crystal transformations prior to melting. 1 exhibits magnetic bistability and negative thermal expansion, which are coupled with crystal–crystal transformation, the recorded room temperature ionic conductivity (σ) at the 10−4 S cm−1 level for the as-prepared crystals, comparable to the room temperature fast ion conductor NASICON (Na3Zr2Si2PO12), and the superionic conduction beyond 10−1 S cm−1 with a broad temperature window (σ = 0.19–0.94 S cm−1 in 318–368 K for the annealed crystals and σ ≈ 1.77 S cm−1 in 408–453 K in the plastic crystal phase). These results will allow for expanding the scope of OIPCs, providing an ideal platform for seeking multifunctional superionic conducting OIPCs.