Advances in Cathodes for High-Performance Magnesium-Sulfur Batteries: A Critical Review

Abstract

Large-scale energy storage with high performance and at a reasonable cost are prerequisites for promoting clean energy utilization. With a high theoretical energy density of 1722 Wh·kg−2, high element abundance (e.g., Mg of 23,000 ppm, S of 950 ppm on earth), and low theoretical cost, Mg-S batteries offer considerable potential as candidates for electrical energy storage. However, due to the intrinsic complex reaction chemistry of sulfur cathodes and metal anodes, such as slow diffusion of the divalent ion, the shuttle of soluble polysulfide, and irreversible deposition of Mg ions on metal electrodes, Mg-S batteries still need further optimization to meet requirements for practical applications. In addition to stabilizing metal anodes, developing a suitable sulfur cathode is desperately needed. This review summarizes recent research progress in sulfur cathodes, interlayers, and non-nucleophilic electrolytes, highlighting the main challenges and corresponding strategies for electrode material designs. Notably, we emphasize a fundamental understanding of the structure-composition relationship. Furthermore, state-of-the-art characterization techniques are described that help reveal the pertinent electrochemical mechanisms whereby Mg-S cells function. Finally, possible research directions are discussed.

Keywords

• magnesium sulfur batteries
• sulfur-based cathodes
• Mg polysulfides
• interlayer modification
• functional separator