Elevating kinetics of passivated Fe anodes with NH_(4)Cl regulator:Toward low-cost,long-cyclic and green cathode-free Fe-ion aqueous batteries

The environment benignity and battery cost are major concerns for grid-scale energy storage applications.The emerging dendrite-free Fe-ion aqueous batteries are promising due to the rich natural abundance,low cost and non-toxicity for Fe resources.However,serious passivation reactions on Fe anodes and poor long-term cyclability for matched cathodes still stand in the way for their practical usage.To settle above constraints,we herein use NH_(4)Cl as the electrolyte regulator to elevate the reaction kinetics of passivated Fe anodes,and also propose a special cathode-free design to prolong the cells lifetime over 1,000 cycles.The added NH_(4)Cl can erode/break inert passivation layers and strengthen the ion conductivity of electrolytes,facilitating the reversible Fe plating/stripping and Fe^(2+)shuttling.The highly puffed nano carbon foams function as current collectors and actives anchoring hosts,enabling expedite Fe^(2+)adsorption/desorption,FeII/FeIII redox conversions and FeIII deposition.The configured rocking-chair Fe-ion cells have good environmental benignity and decent energy-storage behaviors,including high reactivity/reversibility,outstanding cyclic stability and far enhanced operation longevity.Such economical,long-cyclic and green cathode-free Fe-ion batteries may hold great potential in near-future energy-storage power stations.