Toward 500 Wh Kg in Specific Energy with Ultrahigh Areal Capacity All-Solid-State Lithium-Sulfur Batteries.

All-solid-state lithium-sulfur (Li-S) batteries are considered a top choice to achieve 500 Wh kg in specific energy while meeting safety requirements for applications such as future electric aviation. A key bottleneck is that S as the active material lacks sufficient conductivities, making it difficult for effective utilization especially in the solid-state. In addition, to achieve high cell-level specific energy, not only a high-utilization S cathode is required, but also the excess weight needs to be balanced and minimized from the solid-state electrolyte (SSE) separator and the Li metal anode. In this report, solid-state S composite cathodes are designed with an argyrodite sulfide SSE and holey graphene as the electrically conducting scaffold. These solid-state cathodes exhibit high S utilization even at ultrahigh mass loadings up to 15 mg cm, resulting in unprecedented areal capacities over 20 mAh cm. In combination with the simultaneous reduction of the SSE separator thickness as well as the use of a low-excess Li metal anode, a unit cell specific energy value of 505 Wh kg is achieved. Significant design space remains to further optimize individual cell components, providing a feasible outlook to advancing specific energy alongside other critical cell metrics, including power and cyclability, toward practical cells and battery packs.