PNNL

Abstract

Highly porous electrode architecture is widely used to enhance sulfur utilization in lithium-sulfur (Li-S) batteries. However, the high porosity significantly sacrifices cell-level energy density and shortens cell lifespan by trapping the electrolyte from supporting cell cycling. Enabling low-porosity cathodes is a crucial step toward development of realistic high-energy Li-S cells at lean electrolyte conditions, but remains a challenge due to the lack of applicable materials and rational electrode designs fulfilling practical requirements. Here, by controlling the electrode microstructure, high-mass-loading and dense sulfur cathodes with ~45% porosity have been achieved and demonstrated to deliver a high discharge capacity (>1000 mAh g-1) at a very low electrolyte/sulfur (E/S) ratio of 4 µL mg-1. Combining with multi-scale characterizations and simulations, we elucidated the critical roles of both material’s and electrode’s structure in determining electrolyte permeability, polysulfide migration, and sulfur reactions under practical conditions. Our investigation reveals that precise manipulation of electrode architecture is essential to realize high-energy Li-S cells.