Atomic layer deposition of core-shell structured V₂O₅@CNT sponge as cathode for potassium ion batteries

Potassium-ion batteries (KIBs) represent one of the most promising alternatives to lithium-ion batteries (LIBs) considering the potential low cost and abundant potassium resource. In this work, we demonstrate a core-shell structured sponge cathode for KIBs, where amorphous V₂O₅ uniformly coats on carbon nanotube (CNT) sponge via atomic layer deposition (ALD). The V₂O₅@CNT sponge shows several advantages as cathode: (1) the three-dimensional (3D) conductive network of CNT sponge offers a fast electron transport pathway, (2) the porous nature and high surface area of CNT sponge enables enough access for electrolyte to V₂O₅, (3) the amorphous structure of V₂O₅ offers a fast kinetics upon K-ion insertion/deinsertion. The V₂O₅@CNT sponge cathode delivers a high capacity of 206 mA h/g and moderate cycling and rate performance in common carbonate-based electrolyte system.