All-solid-state lithium battery with LiBH₄ solid electrolyte

Electrochemical properties of all-solid-state lithium batteries using lithium borohydride (LiBH₄) as a solid electrolyte are presented for the first time. Despite its high conductivity and good compatibility with a lithium electrode, LiBH₄ has not been considered suitable for practical applications partly due to its high reducing capability when used with metal oxides. In our investigation, it was confirmed that contact between this hydride solid lithium ion conductor and LiCoO₂ results in a large interfacial resistance, and therefore significant capacity loss. In an attempt to minimize this effect, an intermediate Li₃PO₄ layer was employed. Our results indicate a significant improvement in both the rate and the cycle performance of LiBH₄ solid electrolyte batteries, suggesting that LiBH₄ can be used in practical applications as an electrolyte in all-solid-state lithium batteries.