In Situ Ag Nanoparticles Reinforced Pseudo-Zn-Air Reaction Boosting Ag2V4O11 as High-Performance Cathode Material for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs), which are low-cost and environmentally friendly, have been regarded feasible for large-scale energy storage. But the widespread application of AZIBs is hindered by lack of suitable cathode materials with high capacity and long cycle life. The zinc-storage mechanisms, especially the formation of basic zinc salt (BZS), are still unclear. Here, Ag2V4O11 is developed as a cathode material for AZIBs, which delivers a specific capacity of 213 mA h g(-1) and excellent cycling performance (93% capacity retention after 6000 cycles). The reversible formation/decomposition of BZS and reduction/oxidation of metallic Ag are ascertained during the insertion/extraction of Zn(H2O)(6)(2+). Remarkably, the phase composition of BZS in Zn(CF3SO3)(2)-based electrolyte is identified first. The role of in situ formed Ag nanoparticles is simulated by employing the commercial Ag nanoparticles as an additive into the V2O5-based electrodes. The introduction of Ag significantly improves the specific capacity (at least 50% improvement) and accordingly it is proposed that the pseudo-Zn-air reaction (oxygen reduction reaction-like redox reaction happens on material surface in a closed system) promotes the electrochemical performance of Ag2V4O11. This work reveals the BZS rather than unknown new phases on the electrode surface and puts forward a possible way in raising electrochemical properties by utilizing the pseudo-Zn-air reaction.