Effect of Electrolyte on High Sulfur Loading Li-S Batteries

Abstract

Practical lithium-sulfur batteries require high sulfur electrode loading and lean electrolyte designs, which entail more research efforts on the two cell-design parameters - sulfur loading and electrolyte/sulfur loading ratio (E/S). In this work, a systematic investigation is performed to understand the impact of these two variables over key Li-S cell performance parameters. It is demonstrated that Li-S cells’ power performance strongly depends on the E/S ratio, while both E/S ratio and sulfur loading significantly influence the cycle life of Li-S cells. Low E/S ratio and high sulfur loading both give rise to fast lithium anode corrosion, which induces fast capacity fade and Coulombic efficiency decay. Pre-passivation of the lithium anode with an ionic conductor Li3PO4 protection layer only improves the Coulombic efficiency retention at sulfur loading levels much lower than the practical threshold. Meanwhile, increasing the concentration of LiNO3 additive in the electrolyte is found effective in sustaining the cycling capacity and the Coulombic efficiency over a reasonable usage window (∼200 cycles). The role of LiNO3 is the protection of lithium anode during cycling.