Low-tortuous and dense single-particle-layer electrode for high-energy lithium-sulfur batteries

Abstract

Reducing cathode porosity is essential to balancing the electrolyte distribution in lithium-sulfur (Li-S) cells, conserving more pore-filling electrolyte to extend cell cycle life. However, low-porosity electrodes built with nanosized sulfur/carbon (S/C) materials suffer from high tortuosity that significantly deteriorates electrode wetting and hence sulfur utilization. Enabling operation of high-loading sulfur electrodes under both low-porosity and lean-electrolyte conditions is still a challenge and is seldom discussed. In this study, we demonstrated a facile strategy for constructing low-tortuosity through-pores across both vertical and planar directions of electrodes by casting large particles into single-particle-layer electrodes. Through multi-scale characterizations and simulations, correlations between material/electrode structures, electrolyte permeability, polysulfide migration, and sulfur reactions were elucidated. The high-loading and dense sulfur cathode fabricated by this method delivers a high specific capacity (>1000 mA h g−1) at a very low electrolyte/sulfur (E/S) ratio of 4 μL mg−1. This study provides a practical approach to reducing the tortuosity of dense sulfur electrodes by manipulating the porosity distribution, which would be also applicable to improving the rate capability of other high-energy electrodes.