Ionic interaction-mediated interlayer repulsion force promotes steadily shuttling of Zn2+ ions within VOPO4

Rechargeable zinc ion batteries (ZIBs) are devices with excellent grid storage potentials due to their low cost, inherit safety and material abundancy, but poor cathode stability associated with structural degradation remains a major challenge. In this study, a highly stable layered VOPO4 cathode is realized by optimizing interlayer repulsion via a sulfur mediation strategy that mitigates irreversible transformation and regulates the redox centers. Specifically, sulfur ions are pre-intercalated into the material crystal structure to provide resilience toward Zn intercalation/extraction, while weakening the Zn-O interaction to facilitate extensive ion extraction. X-ray analyses reveal formation of SO42- moieties that alter electronic configuration and strengthen interlayer interactions, which lead to significant elevation in redox accessibility and reaction reversibility. Benefiting from the optimizations, the sulfur intercalated VOPO4 delivers a remarkable capacity of 207 mAh g−1 at 0.1 A g−1 that far exceed the 91 mAh g−1 of pristine VOPO4•2 H2O, and capacity retention of 87.5% after 1500 cycles at 2.0 A g−1. Overall, a widely applicable sulfur intercalation strategy is demonstrated here to simultaneously promote redox utilization and structural stability of ZIBs cathode, while a deeper understanding on the interaction-mediating mechanism is unveiled.