Organic Crystalline Solid Electrolytes with High Mg-Ion Conductivity Composed of Nonflammable Ionic Liquid Analogs and Mg(TFSA) 2 .

The development of solid electrolytes with Mg-ion conductivity at room temperature is an important issue to achieve all-solid magnesium batteries. We focus on organic ionic crystals with Mg-ion conduction paths in addition to nonflammable and nonvolatile features as an innovative candidate of solid electrolytes with Mg-ion conductivity. Herein, we show the development of novel organic ionic crystals, [N(CH 3 ) 4- n (CH 2 CH 3 ) n ][Mg{N(SO 2 CF 3 ) 2 } 3 ] ( n = 0 or 2), using analogs of ionic liquids, [N(CH 3 ) 4 ][N(SO 2 CF 3 ) 2 ] (N 1111 TFSA) and [N(CH 3 ) 2 (CH 2 CH 3 ) 2 ][N(SO 2 CF 3 ) 2 ] (N 1122 TFSA), and magnesium salt, Mg{N(SO 2 CF 3 ) 2 } 2 (Mg(TFSA) 2 ). We also report the crystal structures of the obtained crystals and the high Mg-ion conductivity of 10 -4 S cm -1 under mild conditions of 80 °C in the solid state. These results indicate that organic ionic crystals with ion conduction paths have significant potential as safe solid electrolytes and provide insights into developing innovative Mg-ion conductors.