Reconstructed Orthorhombic V2O5 Polyhedra for Fast Ion Diffusion in K-Ion Batteries

Potassium-ion batteries (KIBs) are a promising alternative to lithium-ion batteries because of the abundance, low cost, and redox potential of K; however, the significantly larger radius of K+ inevitably destabilizes the crystal structure of the cathode material, impeding the diffusion of K+. Here, to lower the insertion energetics and diffusion barriers of K+, we synthesizedδ-K0.51V2O5 nanobelts (KVOs) with a large interlayered structure and optimized growth orientation by reconstructing the V–O polyhedra of orthorhombic V2O5; these exhibited a high average voltage (3.2 V), high capacity (131 mAh g−1), and superior rate capability even at 10 A g−1. By coupling the electrochemical experiments with theoretical calculations, we found that the excellent K-ion storage performance of KVO is attributed to its large interlayered structure and unique 1D morphology. Additionally, we assembled a full KIB composed of KVO and graphite with high energy and power densities, proving its feasibility as a promising new battery.