High Performance All-Solid-State Li-S Battery Enabled by Interfacial Modification

All-solid-state batteries are considered a promising technology to enable future electric vehicles. The use of solid electrolyte in place of liquid electrolyte not only improves overall safety of the battery but also increases the energy density. Combining solid electrolyte with high capacity anodes and cathodes such as lithium metal and sulfur cathode to achieve all-solid-state Li-S battery (ASSLSB) further improves energy density. In addition, ASSLSB mitigates issues related to “polysulfide shuttle” present in liquid-based Li-S cells. Despite such advantages, achieving high performance ASSLSB is challenging due to poor interfacial properties at solid electrolyte/electrode interfaces.<br/> <br/>To address challenges related to poor interfacial contact, we use the strategy of modifying the interface by employing the highly concentrated solvate electrolyte, (MeCN)₂−LiTFSI:TTE, as an interlayer material at the electrolyte/electrode interfaces. The incorporation of the interlayer enhances the cyclability of the solid-state Li₂S cell compared to the bare counterpart. Electrochemical impedance spectroscopy of the interlayer-incorporated cell shows a gradual decrease in interfacial resistance as a function of cycle number, whereas the cell impedance of the bare cell remains constant.<br/> <br/>Another way to utilize the solvate electrolyte is to premix the solvate with solid electrolyte to prepare a solvate-solid electrolyte mixture (“solvSEM”) electrolyte. The cell using solvSEM electrolyte further improves the cycling performance in terms of active material utilization, capacity retention, and active material loading. The solvSEM electrolyte combines the benefits of solid electrolyte and solvate electrolyte in that solid electrolyte acts as a blocking layer for polysulfide dissolution and diffusion while solvate electrolyte forms the favorable ionic contact at battery interfaces.