Although lithium-sulfur batteries exhibit a fivefold higher energy density than commercial lithium-ion batteries, their volume expansion and insulating nature, and intrinsic polysulfide shuttle have hindered their practical application. An alternative sulfur host is necessary to realize porous, conductive, and polar functions; however, there is a tradeoff among these three critical factors in material design. Here, the authors report a layered porous carbon (LPC) with VO2 /V3 S4 heterostructures using one-step carbonization-sulfidation of metal-organic framework templates as a sulfur host that meets all the criteria. In situ conversion of V-O ions into V3 S4 nuclei in the confined 2D space generated by dynamic formation of the LPC matrix creates {200}-facet-exposed V3 S4 nanosheets decorated with tiny VO2 nanoparticles. The VO2 /V3 S4 @ LPC composite facilitates high sulfur loading (70 wt%), superior energy density (1022 mA h g-1 at 0.2 C, 100 cycles), and long-term cyclability (665 mA h g-1 at 1 C, 1000 cycles). The enhanced Li-S chemistry is attributed to the synergistic heterocatalytic behavior of polar VO2 and conductive V3 S4 in the soft porous LPC scaffold, which accelerates polysulfide adsorption, conversion, and charge-transfer ability simultaneously.
Keywords: heterocatalysts; layered porous carbons; lithium-sulfur batteries; metal-organic-frameworks; polar mediators.
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