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

The phase transitionof the CaVO composite cathode resultsin structural stability after the initial charge, leading to excellentelectrochemical performance. Rechargeable aqueous zinc (Zn)-ion batteries (AZiBs)have beenemerging as a complementary technology to lithium-ion batteries inenergy storage applications owing to their safe operation, low cost,and eco-friendly features. However, the development of AZiBs for commercializationis 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 bya facile solvothermal synthesis and investigated as a cathode materialfor AZiBs. As a result, the CaVO composite cathode exhibited a highreversible capacity of 321.8 mA h g(-1) over 300 cyclesat 1 A g(-1) and maintained a reversible capacityof 268 mA h g(-1) over 600 cycles at 2 A g(-1). Interestingly, the CaVO composite cathode showed excellent operatingstability over 3000 cycles, even at a high current rate of 10 A g(-1). The assembled Zn/CaVO battery delivered outstandingenergy densities of 329 and 315 W h kg(-1) at powerdensities of 206 and 414 W kg(-1), respectively. Inaddition, an insight into the energy storage mechanism in Zn/CaVOcomposite rechargeable aqueous batteries was systematically elucidatedusing structural and morphological analyses. The CaVO composite cathodeserves as an excellent Zn2+ host owing to the presenceof Ca-ion pillaring, which results in good reversibility and excellentrate performance.