Double-Sheet Vanadium Oxide as a Cathode Material for Calcium-Ion Batteries

Calcium-ion batteries (CIBs) are theoretically considered one of the potential post-lithium-ion battery technologies. However, only a few host materials are known to intercalate Ca ions. Herein, we demonstrate the use of double-sheet vanadium oxide V2O5 . 0.63H(2)O as a high-performance cathode material for CIBs. The vanadium oxide was synthesized via an electrochemical oxidation process on a graphite foil substrate. The material exhibited a high reversible capacity of 204 mAh g(-1) at a 0.1 C rate in an aqueous electrolyte, with an average discharge voltage of 2.76 V vs. Ca/Ca2+, and a capacity retention of 86% after 350 cycles. The reaction mechanism can be described as a combination of diffusion-controlled intercalation and surface-limited pseudo-capacitance reactions. This study provides a new type of Ca host material, motivating further development of new CIB cathode materials.