Promoting polysulfide bidirectional conversion by one-dimensional p-n junctions for Li-S batteries

Sulfur redox reactions are crucial in lithium-sulfur (Li-S) batteries, typically characterized by intricate multiphase conversion processes. A catalytic approach to transform polysulfides effectively mitigates the shuttle effects in Li-S batteries. However, a catalyst consisting of a single component cannot fully participate in the two-way redox process. In this study, we have addressed these issues by fabricating one-dimensional ZnO@NiO core-shell nanobelts (CNBs), which establish a p-n junction interface. A built-in electric field (BIEF) at this interface results in the spontaneous redistribution of charges, facilitating the transfer of electrons between the ZnO and NiO surfaces. While this weakens the strong adsorption properties, it simultaneously expedites the transfer of polysulfide. As a result of the moderate adsorption capacity of polysulfide and the lowered energy barrier for sulfur conversion, the intrinsic catalytic activity of ZnO@NiO p-n junctions contributes to the increased speed of bidirectional sulfur conversion. The as-prepared cathode, composed of ZnO@NiO CNBs, demonstrates an outstanding discharge capacity of 1525.5 mA h g−1 at a rate of 0.1 C. Following 1000 cycles at a rate of 2 C, the ZnO@NiO CNBs cathode maintains a substantial capacity, with a retention rate of 73.60%, equivalent to an impressively low capacity loss of 0.026% per cycle. This research highlights the synergy of the BIEF and heterostructures in facilitating the gradual transport of polysulfides, offering new perspectives on designing interfacial structures for the controlled regulation of polysulfide redox reactions.