Stable Interface Formation between TiS2 and LiBH4 in Bulk-Type All-Solid-State Lithium Batteries

Atsushi Unemoto, Tamio Ikeshoji, Syun Yasaku, Motoaki Matsuo, Vitalie Stavila, Terrence J. Udovic, Shin Ichi Orimo

Research output: Contribution to journalArticlepeer-review

106 Citations (Scopus)


In this study, we assembled a bulk-type all-solid-state battery comprised of a TiS2 positive electrode, LiBH4 electrolyte, and Li negative electrode. Our battery retained high capacity over 300 discharge-charge cycles when operated at 393 K and 0.2 C. The second discharge capacity was as high as 205 mAh g-1, corresponding to a TiS2 utilization ratio of 85%. The 300th discharge capacity remained as high as 180 mAh g-1 with nearly 100% Coulombic efficiency from the second cycle. Negligible impact of the exposure of LiBH4 to atmospheric-pressure oxygen on battery cycle life was also confirmed. To investigate the origin of the cycle durability for this bulk-type all-solid-state TiS2/Li battery, electrochemical measurements, thermogravimetry coupled with gas composition analysis, powder X-ray diffraction measurements, and first-principles molecular dynamics simulations were carried out. Chemical and/or electrochemical oxidation of LiBH4 occurred at the TiS2 surface at the battery operating temperature of 393 K and/or during the initial charge. During this oxidation reaction of LiBH4 with hydrogen (H2) release just beneath the TiS2 surface, a third phase, likely including Li2B12H12, precipitated at the interface between LiBH4 and TiS2. Li2B12H12 has a lithium ionic conductivity of log(σ / S cm-1) = -4.4, charge transfer reactivity with Li electrodes, and superior oxidative stability to LiBH4, and thereby can act as a stable interface that enables numerous discharge-charge cycles. Our results strongly suggest that the creation of such a stable interfacial layer is due to the propensity of forming highly stable, hydrogen-deficient polyhydro-closo-polyborates such as Li2B12H12, which are thermodynamically available in the ternary Li-B-H system. (Figure Presented).

Original languageEnglish
Pages (from-to)5407-5416
Number of pages10
JournalChemistry of Materials
Issue number15
Publication statusPublished - 2015 Aug 11


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