Facile carbon cloth activation strategy to boost oxygen reduction reaction performance for flexible zinc‐air battery application

Flexible and all-solid-state zinc-air batteries (ZABs) are highly useful and also in demand due to their theoretical high energy densities and special applications. The limitation in their performance arises due to their catalyst-coated cathode electrodes in terms of catalytic activity and stability as well as cost. In this paper, a novel and environmentally friendly activation strategy is developed to activate the carbon cloth (CC) for the electrodes. The activated CC serves as a catalyst-free air cathode with high conductivity, excellent mechanical strength, and flexibility, in addition to low cost. The strategy is performed by simply electro-oxidizing and electroreducing CC under ultrahigh direct current (DC) voltage in a diluted NH4Cl aqueous electrolyte. It is found that the electro-oxidation not only results in the formation of a graphene-like exfoliated carbon layer on the surface of CC but also induces the incorporation of oxygen-containing groups and doping of nitrogen and chloride atoms. After the electroreduction, the pi-conjugated carbon network of CC is partially restored, leading to the recovery of electroconductivity. Such an electroactivated CC shows excellent oxygen reduction reaction activity. The aqueous flexibility and all-solid-state ZABs are assembled using such an electroactivated CC cathode without any catalyst loading. Both ZABs can achieve good durability and deliver high peak power density and an energy density as high as 690 Wh kg(-1), demonstrating the excellent potential of this electroactivated CC in practical devices.