Li-Ion Conductivity Enhancement of LiBH₄·xNH₃ with In Situ Formed Li₂O Nanoparticles

Interfacial engineering is an efficient approach to improve the ionic conductivity of solid-state electrolytes. In the present study, we report the enhancement of in situ formed nanocrystalline Li2O on the thermal stability and electrochemical properties of amide lithium borohydride, LiBH4·xNH3 (x = 0.67–0.8). LiBH4·xNH3–Li2O composites with different amounts of Li2O are prepared by a one-step synthesis process by ball milling the mixture of LiBH4, LiNH2, and LiOH in molar ratios of 1:n:n (n = 1, 2, 3, 4). Owing to the strong interfacial effect with nanocrystalline Li2O, LiBH4·xNH3 is converted to the amorphous state in the presence of 78 wt % Li2O at n = 4. Consequently, the ionic conductivity of LiBH4·xNH3 at 20 °C is improved by orders of magnitude up to 5.4 × 10–4 S cm–1, the NH3 desorption temperature is increased by more than 20 °C, and the electrochemical window is widened from 0.5 to 3.8 V.