Calcium-Pillar Boosting Smooth Phase Transition in Potassium Vanadate Nanobelts toward Superior Cycling Performance...

The depletion of lithium resources has prompted exploration into alternative rechargeable energy storage systems, and potassium-ion batteries (PIBs) have emerged as promising candidates. As an active cathode material for PIBs, potassium vanadate (KV₂O₅) usually suffers from structural damage during electrochemical K-ion insertion/extraction and hence leading to unsatisfactory cycling performance. Here, we introduce Ca²⁺ ions as pillars into the potassium vanadate to enhance its structural stability and smooth its phase transition behavior. The additional Ca²⁺ not only stabilizes the layered structure but also promotes the rearrangement of interlayer ions and leads to a smooth solid-solution phase transition. The optimal composition K_0.36Ca_0.05V₂O₅ (KCVO) exhibits outstanding cyclic stability, delivering a capacity of ∼90 mA h g^-1 at 20 mA g^-1 with negligible capacity decay even after 700 cycles at 500 mA g^-1. Theoretical calculations indicate lower energy barriers for K⁺ diffusion, promoting rapid reaction kinetics. The excellent performances and detailed investigations offer insights into the structural regulation of layered vanadium cathodes.