Keggin-Type Polyoxometalate and Co Nanoparticles Codecorated Separator for High-Performance Lithium–Sulfur Battery

The Li–S battery has garnered widespread attention as an intriguing new energy storage equipment due to its remarkable energy density and low cost. Nevertheless, the infamous shuttle effect seriously hinders the commercialization process. In order to address this issue, this study rationally synthesizes the composites comprising Keggin-type polyoxometalate and Co nanoparticles, which are then coated on a pristine polypropylene separator. The modified separator can greatly inhibit lithium polysulfide shuttling, thereby leading to a greatly improved electrochemical performance. At the first cycle, the fabricated Li–S battery exhibits a specific discharge capacity of 1335.7 mA h g–1, surpassing the 938.7 mA h g–1 capacity of an unmodified separator. At a current density of 1C, the initial reversible discharge capacity reaches 988.2 mA h g–1, and even after 500 cycles, it still retains a remaining capacity of 664.2 mA h g–1, with a capacity decay rate of 0.066% per cycle. Even at a high sulfur loading of 4.2 mg cm–2, the device displays a remarkable initial discharge capacity of 1158.2 mA h g–1, with a remaining capacity of 952.7 mA h g–1 after 70 cycles (0.1C). This significant performance enhancement could be ascribed to the synergistic effect of PMo12/Co–NCe, which exhibits greatly decreased electron transfer resistance and contact angle to the electrolyte, facilitating the rapid transport of Li-ion and kinetics. Meanwhile, the severe shuttle effect is alleviated effectively by combining the strong catalytic activity of PMo12 and Co nanoparticles with long-chain polysulfides.