Marrying V5S8 and Sb2S3 for volume-tolerant and high-rate potassium-ion storage

Abstract

To address the challenges of sluggish ion transport and severe volume fluctuation in potassium-ion batteries (PIBs) arising from the large K+ radius, we design a covalently bonded V5S8/Sb2S3 heterostructure encapsulated in N-doped carbon (V5S8/Sb2S3@NC). Calculations using density functional theory (DFT) show that the metallic V5S8 and semiconducting Sb2S3 form a bandgap-free interface, facilitating rapid charge transfer, while the V–S–Sb covalent bonds enhance interfacial stability. Where V5S8 undergoes partial (de)intercalation-induced amorphization that relaxes lattice stress and buffers the ~300% volume expansion of Sb2S3 to only ~112% (verified by in situ optical microscopy). The synergistic design delivers a high reversible capacity of 657.6 mA h g–1 at 0.05 A g–1, long-term cycling stability with 301.5 mA h g–1 retained after 600 cycles at 1 A g–1, and rate capability superior to most reported PIB anodes. This work highlights the critical role of covalent interface engineering and amorphization-regulated K+ storage for high-energy PIB anodes.