Stable Na/K–S\nBatteries with Conductive Organosulfur\nPolymer Microcages as Cathodes

Na–S and K–S batteries, with high-energy\ndensity,\nusing naturally more abundant and affordable metals compared with\nrare resources like Li, Co, and Ni elements, have inspired intense\nresearch interest. However, the sulfur cathodes for Na/K storage are\nplagued by soluble polysulfide shuttling, larger volumetric deformation,\nand sluggish redox kinetics. Here, we report that a conductive organosulfur\npolymer microcage, fabricated facilely with the microbe and elemental\nsulfur as precursors, can effectively address these issues for stable\nhigh-capacity Na–S and K–S batteries. The covalently\nbonded short-chain sulfur species enable superior reaction kinetics\nand avoid soluble polysulfide formation. The microcage architecture\nwith built-in cavities buffers the volume deformation to ensure a\nresilient electrode. The resultant conductive organosulfur polymer\ncan promise a combination of high capacity and extraordinary cyclability\nwith a promising rate and Coulombic efficiency. Especially, as a K–S\nbattery cathode, it could deliver a high capacity of 1206.5 mAh g<sup>–1</sup> together with an extraordinary cyclability (>99%\ncapacity retention over 1100 cycles), which is much better than that\nof state-of-the-art sulfur cathodes. This work envisions new perspectives\non building conductive organosulfur cathode materials with high performance\nvia a simple and feasible protocol.