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Lithium borohydride (LiBH 4 ), with high compatibility to lithium anode, low grain boundary resistance, and light mass, is regarded as a promising solid-state electrolyte. However, poor ionic conductivity at room temperature limits its practical application in all-solid-state lithium-ion batteries (ASSLBs). In the present study, Li(NH 3 ) x BH 4 @SiO 2 (0 ≤ x ≤ 0.5) composites were obtained by ammonia absorption and simple ball-milling. Among them, Li(NH 3 ) 0.5 BH 4 @ SiO 2 exhibits a high ionic conductivity of 3.95 × 10 −2 S cm −1 at 60 °C, with a lithium transference number up to 0.9999 at 30 °C. More importantly, the experimental results and density functional theory (DFT) calculations show that the skeleton and interfacial interaction of silica can effectively improve the electrochemical performance of the full cell. All-solid-state lithium−sulfur batteries exhibit a specific discharge capacity of 1221.7 mAh g −1 after 10 cycles. Reversible capacities of 1589, 1381, 1176, 969, and 695 mAh g −1 could be achieved at 0.1, 0.2, 0.3, 0.5, and 1C, respectively. These findings prove that Li(NH 3 ) x BH 4 @SiO 2 is an attractive electrolyte for next-generation ASSLBs.

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Replacing widely used organic liquid electrolytes with solid-state electrolytes (SSEs) could effectively solve the safety issues in sodium-ion batteries. Efforts on seeking novel solid-state electrolytes have been continued for decades. However, issues about SSEs still exist, such as low ionic conductivity at ambient temperature, difficulty in manufacturing, low electrochemical stability, poor compatibility with electrodes, etc. Here, sodium carbazolide (Na-CZ) and its THFcoordinated derivatives are rationally fabricated as Na + conductors, and two of their crystal structures are successfully solved. Among these materials, THF-coordinated complexes exhibit fast Na + conductivities, i.e., 1.20 × 10 À 4 S cm À 1 and 1.95 × 10 À 3 S cm À 1 at 90 °C for Na-CZ-1THF and Na-CZ-2THF, respectively, which are among the top Na + conductors under the same condition. Furthermore, stable Na plating/stripping is observed even over 400 h cycling, showing outstanding interfacial stability and compatibility against Na electrode. More advantages such as ease of synthesis, lowcost, and cold pressing for molding can be obtained. In situ NMR results revealed that the evaporation of THF may play an essential role in the Na + migration, where the movement of THF creates defects/vacancies and facilitates the migration of Na + .