High-Capacity Calcium Vanadate Composite with Long-Term Cyclability as a Cathode Material for Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc (Zn)-ion batteries (AZiBs) have been emerging as a complementary technology to lithium-ion batteries in energy storage applications owing to their safe operation, low cost, and eco-friendly features. However, the development of AZiBs for commercialization is still in its infancy and is hindered by the unstable cathode. Herein, a calcium vanadate/vanadium oxide (CaV3O7/V2O3) composite (treated as CaVO) was prepared by a facile solvothermal synthesis and investigated as a cathode material for AZiBs. As a result, the CaVO composite cathode exhibited a high reversible capacity of 321.8 mA h g–1 over 300 cycles at 1 A g–1 and maintained a reversible capacity of 268 mA h g–1 over 600 cycles at 2 A g–1. Interestingly, the CaVO composite cathode showed excellent operating stability over 3000 cycles, even at a high current rate of 10 A g–1. The assembled Zn/CaVO battery delivered outstanding energy densities of 329 and 315 W h kg–1 at power densities of 206 and 414 W kg–1, respectively. In addition, an insight into the energy storage mechanism in Zn/CaVO composite rechargeable aqueous batteries was systematically elucidated using structural and morphological analyses. The CaVO composite cathode serves as an excellent Zn2+ host owing to the presence of Ca-ion pillaring, which results in good reversibility and excellent rate performance.