Optimal liquid sulfur deposition dynamics for fast-charging Li-S batteries

It is urgent to develop fast-charging batteries to eliminate the charging concerns when using electric vehicles. The fluid nature of liquid sulfur was found to enhance areal capacities and contribute to lithium-sulfur (Li-S) fast-charging batteries. However, the deposition kinetics of liquid sulfur in Li-S batteries remain underexplored. This study uses a micro-battery device to track the in-situ deposition of liquid sulfur on carbon film. Surprisingly, slower reaction and sulfur growth kinetics were observed even under high overpotential and high-conductivity substrates, indicating that excessive sulfur droplet formation impedes both reaction and growth kinetics. This insight guided the tailoring of carbon nanofiber cathodes, resulting in 94% capacity retention even with a significant increase in charging rate (from 1 C to 8 C). This research advances our understanding of liquid sulfur in Li-S batteries and provides guidance for designing high-performance, fast-charging cathodes.