Layered Iron Vanadate As a High-Energy Cathode Material for Nonaqueous Calcium-Ion Batteries

Abstract

Calcium-ion batteries (CIBs) are one of the promising candidates for post-lithium-ion batteries. However, only a few types of host materials are known to intercalate calcium ions reversibly in a nonaqueous electrolyte. Here, we demonstrate the electrochemical performances and evidence of calcium-ion intercalation into iron vanadate, FeV 3 O 9 ∙xH 2 O, as a cathode material for CIBs at ambient temperature. FeV 3 O 9 ∙xH 2 O was prepared via a facile water-bath method. It shows reversible calcium intercalation with a first discharge capacity of 334.4 mAh g −1 at 20 mA g −1 rate with an average voltage of ~2.26 V (vs. Ca/Ca 2+ ) and excellent capacity retention in an electrolyte of 0.5 M Ca(ClO 4 ) 2 in acetonitrile. The high performance of the material with a layered structure and a wide range of vanadium oxidation states provides insights into the search for new oxide-based high-energy cathode materials for CIBs.