Optimized strategies to enhance electrochemical properties of ammonium vanadates for aqueous Zn ion batteries

Vanadium-based oxides cathodes in aqueous Zn ion batteries are being widely investigated. Strategies to improve their electrochemical property are focused on the development of ion insertion/desertion kinetics, and pre-insertion of ions or molecules. However, few works focuses on the pseudocapacitive behaviors vs capacity. In this work, ammonium vanadates with different surface areas and architectures are designed, and it is find that the designed structure electrodes show rather high initial capacities of 574.6 and 524.0 mAh/g at 0.1 A/g, which are much higher than the unoptimized cathode. Based on in-depth investigation, the improvement originates from the increased capacitive contribution convinced by kinetics and actual electrochemical surface area. Moreover, the higher surface area brings inevitable worse problems of collapses and dissolution, which lead to a rapid decline of capacities. In this consideration, VOSO4 is firstly used as an electrolyte additive to relieve the capacity decay through the introduced electrodeposition of active material, which could be a general approach. such a result gives a new sight for the design and optimized strategies of high performance vanadium-based cathodes in aqueous zinc ion batteries.