Defective Boron Nitride Inducing the Lithium-ion Migration on the Sub-Surface of LiBH₄

The safety issues oflithium-ion batteries provoke the development of highly secure solidelectrolytes. Hydride electrolytes owning the high electrochemical stabilityand anode compatibility may sufficiently relieve theconcerns of safety. However, the low ionic conductivity at room temperature hampersits further application. Herein, the strategy of defect-induced (BH₄)^– deformation to achieve high ionicconductivity LiBH₄/BN composite electrolyte is suggested. The theoreticalcalculations indicate that the volume of the (BH₄)^– tetrahedron is expanded by 14%. Such atetrahedron deformation weakens the Li-H interaction forces in LiBH₄, and thus promotes the Li-ion migration. The LiBH₄/BN composites are enabled to deliver lithium ionicconductivity of 1.15 × 10^–4 S cm^–1 at 40 °C with a Li-ion transference number of 97%, persuading an excellent solidelectrolyte for all-solid-state batteries. The sub-surface of LiBH₄ offers the lowest migration barrier among all possiblechannels, paving the optimal way for Li-ion migration. Furthermore, the LiBH₄/BN electrolytes supply excellent electrochemical stabilityand electrode compatibility. The utilized strategy of outfield induction (notonly defects) and ligand deformation (not only (BH₄)^–) may also be extended to other solid electrolytes.