Enhancing room-temperature ionic conductivity of Na2B12H12 via BN incorporation for all-solid-state sodium metal batteries

Because of their exceptional safety and thermal stability, all-solid-state sodium batteries are viable next-generation energy storage technologies, while borohydride-based solid electrolytes have garnered considerable interest for their favorable electrochemical stability. Nevertheless, Na 2 B 12 H 12 ’s poor room-temperature ionic conductivity continues to be a significant obstacle that restricts its usefulness. To address this issue, this work proposes a simple mechanochemical compositing strategy. By introducing boron nitride (BN) as a multifunctional interfacial modifier, the ionic conduction performance is significantly enhanced. The Na 2 B 12 H 12 /BN composite electrolyte is prepared via high-energy ball milling. Structural characterizations reveal that the incorporation of BN induces a mechanochemistry-driven phase and structural transformation in Na 2 B 12 H 12 and creates abundant heterointerfaces. Electrochemical measurements show that the optimized composite electrolyte achieves a high room-temperature ionic conductivity of 2.2 × 10 −4 S cm −1 , almost an order of magnitude higher than that of ball-milled pristine Na 2 B 12 H 12 , with a reduced activation energy of 0.31 eV. Furthermore, the electrolyte exhibits excellent stability against a Na-Sn alloy, enabling symmetric cells to cycle stably for over 800 h. An all-solid-state sodium battery assembled with Na 3 V 2 (PO 4 ) 3 as the cathode and a Na-Sn alloy as the anode demonstrates outstanding cycling stability (80% capacity retention after 100 cycles at 0.5 C) and rate capability. This work offers new insights for the creation of sophisticated all-solid-state sodium batteries by rationalizing the design of high-performance borohydride-based solid electrolytes through interfacial engineering using inert nanomaterials. A mechanochemical Na 2 B 12 H 12 -BN composite electrolyte exhibits enhanced room-temperature ionic conductivity through induced structural disorder, enabling stable all-solid-state sodium batteries with over 800 h symmetric-cell cycling and durable full-cell performance. • A mechanochemical BN-based composite strategy enables enhanced room-temperature ionic conductivity in Na 2 B 12 H 12 . • BN induces lattice distortion and partial amorphization within the Na 2 B 12 H 12 framework. • The composite electrolyte enables stable symmetric-cell cycling for 800 h and 80% capacity retention in full cells after 100 cycles .