Platinum‐Induced Pseudo‐Zn‐Air Reaction Massively Increases the Electrochemical Capacity of Aqueous Zn/V 5 O 12 ·6H 2 O Batteries

How to effectively improve Zn 2+ ‐storage properties is now becoming an urgent issue in the development of high‐energy‐density aqueous zinc‐ion batteries. Here, a new method is proposed to massively increase the electrochemical capacity of aqueous Zn/V 5 O 12 ·6H 2 O batteries. By adding a small amount of platinum (Pt, 1.5 wt.%) and keeping other factors constant, the V 5 O 12 ·6H 2 O‐Pt electrodes deliver a much higher specific capacity (440 mAh g −1 at 500 mA g −1 ) than do V 5 O 12 ·6H 2 O electrodes (270 mAh g −1 at 500 mA g −1 ). The structural and morphological evolution of V 5 O 12 ·6H 2 O during cycling results in Zn 2+ ion insertion/extraction and the formation/disappearance of the zinc hydroxyl complex (Zn 4 SO 4 (OH) 6 ∙5H 2 O, ZHS), where the latter is closely related to the surface redox reaction, promoting Zn 2+ ion stripping/plating on the Zn anode and consequently leading to extra electron transfer. Electrochemical tests in the absence of oxygen reveal that the Pt additive has no contribution and is even counterproductive to electric conductivity but favors remarkable enhancement of the pseudocapacitance. Accordingly, it is apparent that a strong causal relationship exists between Pt and the ZHS. In consideration of the catalytic application for oxygen reduction, Pt is expected to play a vital role in enhancing the electrochemical capacity through the pseudo‐Zn‐air reaction. This finding introduces a new strategy for achieving high‐performance aqueous zinc‐ion batteries.