Toward Stimulating the Chemistry Process for Garnet Electrolyte-Based Molten Li-S Batteries: Modulation of the End-Product in the Cathode with High Loading

Due to their low self-discharge rate, no intermediate product dissolution in the cathode, and easy recycle of electrode materials, solid electrolyte-based molten lithium sulfur batteries can be one of the highly anticipated advanced electrochemical chemistry technologies for grid-scale energy storage. However, the actual energy density and reversibility of them still face severe challenges for low active materials loading and the inherent low conductivity of sulfur and its end-products. In this work, with the iodide modulation effect, small size (∼5 nm for the primary particles) and low relative crystallinity discharge end-products in the sulfur cathode can be formed, contributing to the immense specific capacity and reversibility. As validated by theoretical calculations, iodide ions in the homogeneous molten composite cathode display a profound comprehensive effect on the chemical reaction and cycling stability. As a result, high sulfur loading (over 80 mg cm^-2) with a significant utilization rate can be achieved, corresponding to a single Li-S cell of 1.39 Ah and a volumetric energy density of 528.5 Wh L^-1 based on the overall cell volume; simultaneously, a prominent cycling stability during 300 cycles along with an impressive reversibility is obtained.