Engineering hollow core-shell hetero-structure box to induce interfacial charge modulation for promoting bidirectional sulfur conversion in lithium-sulfur batteries

Abstract

Severe polysulfide shuttling and sluggish sulfur redox kinetics significantly decrease sulfur utilization and cycling stability in lithium-sulfur batteries (LSBs). Herein, we develop a hollow CoO/CoP-Box core–shell heterostructure as a model and multifunctional catalyst modified on separators to induce interfacial charge modulation and expose more active sites for promoting the adsorption and catalytic conversion ability of sulfur species. Theoretical and experimental findings verify that the in-situ formed core–shell hetero-interface induces the formation of P-Co-O binding and charge redistribution to activate surface O active sites for binding lithium polysulfides (LiPSs) via strong Li-O bonding, thus strongly adsorbing with LiPSs. Meanwhile, the strong Li-O bonding weakens the competing Li-S bonding in LiPSs or Li2S adsorbed on CoO/CoP-Box surface, plus the hollow heterostructure provides abundant active sites and fast electron/Li+ transfer, so reducing Li2S nucleation/dissolution activation energy. As expected, LSBs with CoO/CoP-Box modified separator and traditional sulfur/carbon black cathode display a large initial capacity of 1240 mA h g−1 and a long cycling stability with 300 cycles (∼60.1% capacity retention) at 0.5C. Impressively, the thick sulfur cathode (sulfur loading: 5.2 mg cm−2) displays a high initial areal capacity of 6.9 mA h cm−2. This work verifies a deep mechanism understanding and an effective strategy to induce interfacial charge modulation and enhance active sites for designing efficient dual-directional Li-S catalysts via engineering hollow core–shell hetero-structure.