High ionic conductivity in Li4(BH4) 3I/(d-BN) solid electrolytes through synergistic defect engineering and phase stabilization

Solid electrolytes offer a transformative solution to the safety challenges that have long hindered conventional lithium-ion batteries (LIBs), which rely on organic liquid electrolytes. Among them, hydride-based materials such as LiBH 4 stand out due to their exceptional electrochemical stability and strong compatibility with anode materials. However, their inherently poor ionic conductivity at room temperature (RT, ~10 −8  S cm −1 ) remains a critical bottleneck, primarily attributed to the rigid crystalline framework of hydride structures, which impedes lithium-ion diffusion. In this study, we overcome this limitation by introducing defective hexagonal boron nitride (d-BN) and iodine solutes into a LiBH 4 matrix.(i.e. Li 4 (BH 4 ) 3 I/2(d-BN)) This strategic integration induces structural deformation in the BH 4 tetrahedra, creating optimized pathways for enhanced lithium-ion transport. As a result, the composite achieves an impressive ionic conductivity of 5.9 × 10 −4  S cm −1 at 40 °C and 4.0 × 10 −4  S cm −1 at 25 °C, approaching the conductivity requirement for the commercialization of solid-state electrolyte batteries (10 −3  S cm −1 ), positioning this material among the highest-performing solid hydride electrolytes to date. Mechanistic insights from density functional theory (DFT) and molecular dynamics (MD) simulations revealed that iodine and BN incorporation weakens Li B interactions, extends Li H bond lengths, and reduces the energy barrier for Li-ions migration. In addition, this gain in conductivity is accompanied by a strong cycling performance (The capacity retention rate of the optimized TiS 2 |Li 4 (BH 4 ) 3 I/2d-BN|Li battery exceeds 86 % after 30 charge-discharge cycles at 0.1C). These findings highlight the promise of Li 4 (BH 4 ) 3 I/d-BN composites as efficient solid-state electrolytes for next-generation energy storage applications.