Critical material and device parameters for building a beyond-500-Wh/kg lithium-sulfur battery

Rechargeable batteries with cell-level specific energy beyond 500 Wh/kg have shown promise in powering long-range electric cars and near-space operations of (un)manned aerial vehicles. Lithium-sulfur (Li-S) batteries, with their exceptionally high theoretical specific energy, emerge as a competitive candidate for achieving the target. In this Review, we analyzed the critical parameters, at a material level and a device level, for practically realizing a beyond-500-Wh/kg Li-S battery. For the S cathode, the mass percentage of S in the S/C composites has been identified as positively correlated with the maximum areal-mass-loading of S on the electrode, and negatively correlated with the “electrolyte to S” ratio, so that it plays a decisive role in improving the battery energy. The use of a high-S-percentage cathode also enables reduced cost, easy manufacture, and improved safety of the battery, yet also introduces new issues such as slow charge transfer, parasitic mass transfer of polysulfides and drastic volume variation during Li uptake and release. Strategies, such as optimizing the cathode conversion electrochemistry, regulating the electrolyte composition, and managing the cell (dis)charge protocol were proposed to address the above challenges. We hope that the work offers insights into reasonable materials and battery design for next-generation energy storage. • A laminated pouch cell model is proposed, highlighting the roles of high-S-percentage cathodes in enhancing energy-density. • The parameters of high-S-percentage cathodes are quantified, underscoring their advantages and challenges. • Potential strategies are summarized to address the challenges and advance the development of high-S-percentage cathodes.