Doping engineering of scandium‐based solid‐state electrolytes toward superior ionic conductivity

Abstract One key research point of solid‐state electrolytes (SSEs) is ionic conductivity. To date, their ionic conductivity is relatively low to meet the requirements of practical applications; thus, more investigations on the migration mechanisms are needed. Here, we constructed scandium‐based halide SSEs (Li_3‐xSc_1‐x(Zr/Hf)_xCl₆, x = 0 ~ 0.5). The highest ionic conductivities (1.61 and 1.33 mS/cm) and the lowest activation energies (0.326 and 0.323 eV) are shown in Li_2.6Sc_0.6Zr_0.4Cl₆ (LSZC~0.4) and Li_2.6Sc_0.6Hf_0.4Cl₆ (LSHC~0.4), respectively. Their electrochemical windows in the cells of Li/Li₇P₃S₁₁/LSZC~0.4/LSZC~0.4‐C and Li/Li₇P₃S₁₁/LSHC~0.4/LSHC~0.4‐C are 1.3 ~ 4.2 V and 1.6 ~ 4.1 V versus Li⁺/Li, respectively. The crystal structures and the Li⁺ chemical environments were investigated by X‐ray diffraction and ⁷Li solid‐state magic angle spinning nuclear magnetic resonance, indicating weaker bond strengths of LiCl to facilitate the transportation of Li⁺. The potential reason explaining the increased ionic conductivity was determined based on the bond valence site energy theory. image