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.