A Small Electrolyte Drop Enables a Disruptive Semisolid High-Energy Sulfur Battery Cell Design via an Argyrodite-Based Sulfur Cathode in Combination with a Metallic Lithium Anode

Abstract

Lithium–sulfur batteries with liquid electrolytes are discussed as the most promising post-lithium-ion-battery technology in literature due to their high theoretical specific energy and first prototype cells delivering >470 Wh kg−1. Although several electrolyte and material concepts are developed that partially solve the issue of the so-called shuttle mechanism, the most promising concept to genuinely confine sulfur species in the cathode is all-solid-state argyrodite–sulfur cathodes leading to almost theoretical active material utilization by maintaining reasonable sulfur loadings and electrolyte to sulfur ratios. However, this battery concept has so far not achieved reversible cycling against metallic lithium anodes as it requires high pressures for manufacturing, and ductile lithium metal creeps along the grain boundaries of the solid electrolyte particles leading to short cuts of the cells. Recent findings show that metallic lithium, however, can be stably cycled with dimethoxyethane/lithium-bis(fluorosulfonyl)imide (DME/LiFSI)-based electrolytes. Herein, for the first time, a semisolid concept is presented combining the benefits of an argyrodite-based solid-state cathode and a DME/LiFSI/hydrofluoroether-based anolyte concept – in coin cells and first pouch cells. This disruptive approach enables projected specific energies higher than 600 Wh kg−1 at cell stack level.