Chlorine‐rich lithium argyrodites enables superior performances for solid‐state Li–Se batteries at wide temperature range

Abstract All‐solid‐state Li–Se battery shows great potential as a candidate for next‐generation energy storage devices due to its high energy density and safety. However, the low ionic conductivity of the solid electrolytes and large volume changes of Se active materials are two of the major issues that limit its applications. Herein, a simple solid‐state reaction method is applied to synthesize chlorine‐rich argyrodite Li 5.5 PS 4.5 Cl 1.5 electrolyte with high conductivity of 6.25 mS·cm −1 at room temperature. Carbon nanotube (CNT) is introduced as the host for Se to obtain Se/CNT composite with both enhanced electronic conductivity and lower volume expansion during the electrochemical reaction process. All‐solid‐state Li–Se battery using Li 5.5 PS 4.5 Cl 1.5 as solid electrolyte combined with Se/CNT cathode and Li‐In anode shows a discharge capacity of 866 mAh·g −1 for the 2nd cycle under 0.433 mA·cm −2 at room temperature. Moreover, the assembled battery delivers a high discharge capacity of 1026 mAh·g −1 for the 2nd cycle when cycled at the same current density at 60 °C and maintains a discharge capacity of 380 mAh·g −1 after 150 cycles. Owing to the high Li‐ion conductivity of Li 5.5 PS 4.5 Cl 1.5 electrolyte, the assembled battery displays a high discharge capacity of 344 mAh·g −1 under 0.113 mA·cm −2 at − 20 °C and remains 66.1% after 200 cycles. In addition, this all‐solid‐state Li–Se battery shows ultralong cycling performances up to 1000 cycles under 0.433 mA·cm −2 at − 20 °C. This work offers the design clue to fabricate the all‐solid‐state Li–Se battery workable at different operating temperatures with an ultralong cycling life.