Unlocking liquid sulfur chemistry for fast-charging lithium-sulfur batteries

Abstract

A recent study of liquid sulfur produced in an electrochemical cell has prompted further investigation into regulating Li–S oxidation chemistry. In this research, we examined the liquid-to-solid sulfur transition dynamics by visually observing the electrochemical generation of sulfur on a graphene-based substrate. We investigated the charging of polysulfides at various current densities and discovered a quantitative correlation between the size and number density of liquid sulfur droplets and the applied current. However, the areal capacities exhibited less sensitivity. This observation offers valuable insights for designing fast-charging sulfur cathodes. By incorporating liquid sulfur into Li–S batteries with a high sulfur loading of 4.2 mg cm–2, the capacity retention can reach ∼100%, even when increasing the rate from 0.1 to 3 C. This study contributes to a better understanding of the kinetics involved in the liquid–solid sulfur growth in Li–S chemistry and presents viable strategies for optimizing fast-charging operations.