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

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 (Li_xVS_y) by the mechanochemical treatment of Li₂S and V₂S₃. The Li_xVS_y 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 Li_xVS_y (~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 (ASSBs) with LixVSy 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 ASSBs.