Promoting Robust Potassium Storage via Engineered Zn─S Bond

An engineered Zn─S bond that involves partial cation-site substitution in ZnS@carbon nanosphere (Fe-ZnS@C) highly strengthens the Zn─S bond and stabilizes the ZnS lattice structure. The optimized ZnS achieves charge redistribution around the metal-sulfur bond, enhancing bond energy and highly relieving the uneven internal mechanical stress caused by large K⁺, thus mitigating capacity degradation issues arising from lattice collapse.

Abstract

Zinc sulfide (ZnS) is recognized as a promising anode material for potassium-ion batteries (PIBs) due to its high theoretical capacity. However, the ZnS experiences bond cleavage and lattice structure collapse when it accommodates large potassium ions, leading to short cycle life and low practical capacity. In this study, an engineered Zn─S bond is reported that involves partial cation-site substitution (e.g., with iron) in ZnS@carbon nanosphere (Fe-ZnS@C), which highly strengthens Zn─S bond and stabilizes the ZnS lattice structure. The optimized ZnS achieves charge redistribution around the metal-sulfur bond, enhancing bond energy and highly relieving the uneven internal mechanical stress caused by large K+, thus mitigating capacity degradation issues arising from lattice collapse. Consequently, the Fe-ZnS@C demonstrates slight structural variation at the lattice scale and exceptional reaction kinetics, delivering an ultra-high reversible specific capacity (608.6 mAh g⁻¹ at 100 mA g⁻¹), long-term cycling stability (over 1000 cycles with 95.2% capacity retention), and high-rate capability (270.3 mAh g⁻¹ at 3000 mA g⁻¹). This work provides valuable insights into addressing lattice collapse issues and opens new avenues for stable potassium storage in transition metal sulfides.