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 NH 4 Cl 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 π-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. K E Y W O R D Scarbon cloth, catalyst-free, electroactivation, nitrogen and chlorine co-doping, oxygencontaining groups, ultrahigh and ultralow direct current voltage

As a possible anode for the next generation of electrochemical energy storage batteries, potassium metal has attracted a great deal of attention in recent years. However, potassium metal batteries suffer from poor stability and low coulombic efficiency due to unfavorable dendrite growth and severe volume expansion of potassium metal anodes during charge and discharge processes. Here, a strategy is developed to inhibit dendrite growth, reduce volume expansion and improve the stability of the potassium metal anode by using three-dimensional (3D) copper foam chemically loaded with a thin layer of uniform gold particles (Au/Cu) as the anode substrate. As the host of potassium deposition for forming K/Au/Cu foam anode, such a 3D copper foam with large specific surface area can reduce the potassium deposition current density. The gold particles on the Cu foam surface with a good affinity to potassium can reduce the potassium deposition overpotential, provide deposition sites and realize uniform and dense deposition. As a result, a stable cycle of more than 500 cycles is achieved by using such a K/Au/Cu foam anode. A full cell with K/Au/Cu foam anode and Prussian blue cathode delivers much better coulombic efficiency, cycle stability and low-temperature performance when compared to that without gold deposition anode (K/Cu). Both the experimental characterization for material structure/morphology/composition and theoretical DFT calculations are carried out for fundamental understanding of the performance enhancement mechanism. The main advantages of this 3D K/Au/Cu foam are its potassiophilicity and less volume expansion during charge/discharge processes, which can reduce or eliminate the potassium dendrite growth through forming favorable and stable solid electrolyte interface.