Toward 500 Wh Kg−1 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⁻¹ 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⁻², resulting in unprecedented areal capacities over 20 mAh cm⁻². 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⁻¹ 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.