Li_xVS_y nanocomposite electrodes for high-energy carbon-additive-free all-solid-state lithium-sulfur batteries

Abstract

All-solid-state (ASS) lithium-sulfur batteries are promising power sources with the potential for high capacity and safety. Lithium metal polysulfide cathodes can address issues arising from the low electronic conductivity of Li2S and S. This study synthesized lithium vanadium polysulfides (Lix VSy ) by the mechanochemical treatment of Li2S and V2S3. The Lix VSy system contains nanocomposites of Li2S and LiVS2 in an amorphous matrix; lithiation and delithiation occur in both Li2S and LiVS2 during charging and discharging. LiVS2 enhances the electronic conductivity of Lix VSy (~10-1-10-2 S cm-1) and the reversibility of charge-discharge reactions because of its high electronic conductivity and layered structure. Therefore, ASS batteries with Lix VSy show high capacity (~650 mAh g-1), even without conductive additives. Here, ASS full cells with high loading assembled using a composite cathode comprising Li8VS5.5 and a solid electrolyte in a 80:20 (wt.%) ratio (33 mg cm-2) and a composite Si anode (10.4 mg cm-2) exhibited a high areal capacity of 15 mAh cm-2, resulting in calculation of high energy densities of 853 Wh L-1 and 515 Wh kg-1 when assuming the cells were enlarged and stacked. This study is expected to expedite research on the development of high-performance ASS batteries.