A High‐Performance Li–B–H Electrolyte for All‐Solid‐State Li Batteries

Highly Li‐ion conductive Li 4 (BH 4 ) 3 I@SBA‐15 is synthesized by confining the LiI doped LiBH 4 into mesoporous silica SBA‐15. Uniform nanoconfinement of P 6 3 mc phase Li 4 (BH 4 ) 3 I in SBA‐15 mesopores leads to a significantly enhanced conductivity of 2.5 × 10 −4 S cm −1 with a Li‐ion transference number of 0.97 at 35 °C. The super Li‐ion mobility in the interface layer with a thickness of 1.2 nm between Li 4 (BH 4 ) 3 I and SBA‐15 is believed to be responsible for the fast Li‐ion conduction in Li 4 (BH 4 ) 3 I@SBA‐15. Additionally, Li 4 (BH 4 ) 3 I@SBA‐15 also exhibits a wide apparent electrochemical stability window (0 to 5 V vs Li/Li + ) and a superior Li dendrite suppression capability (critical current density 2.6 mA cm −2 at 55 °C) due to the formation of stable interphases. More importantly, Li 4 (BH 4 ) 3 I@SBA‐15‐based Li batteries using either high‐capacity sulfur cathode or high‐voltage oxide cathode show excellent electrochemical performances, making Li 4 (BH 4 ) 3 I@SBA‐15 a very attractive electrolyte for next‐generation all‐solid‐state Li batteries.