Study On Anions Modified Nickle Oxide And Electrochemical Performance Of Aqueous Energy Storage Device

Aqueous energy-storage devices have attracted much attention due to their safety,among which aqueous alkaline nickle-iron batteries come back to life due to low cost and high theoratically specific capacity.However,NiOOH,the charged state of Nickle-based cathode,is rather unstable in the alkaline electrolyte,which fastens the rate of self discharge.The iron-based anode tends to dissolve during the charge-discharge cycle,resulting in deteriorated cycle life and self discharge.Therefore,the suppression of self discharge may subserve widely application of nickle-iron batteries.In this paper,different anions were used for surface modification of NiO,and the redox additive K₃Fe（CN）₆was introduced into the electrolyte for collaborative energy storage.Firstly,H₂PO₄^-、PO₃^-were grafted onto NiO,its’specific capacity rised to 325.8 m C cm^-2、633.1 m C cm^-2 respectively in KOH、KHFC electrolyte.Furthermore,Fe（CN）₆^4-was attached to NiO（HNO）surface through ions exchange.The specific capacity of HNO was further enhanced to450 m C cm^-2、765 m C cm^-2.The enlarged specific capacity gap of different electrolyte proves the enhanced synergistic effect between electrode and electrolyte.What’s more,Fe（CN）₆^4-inhibits the transformation of NiOOH,improving the self-discharge performance of NiO.After resting in KHFC electrolyte for 100 hours,the self-discharge coulombic efficiency still remain77.76%.To the best of our acknowledge,the self-discharge performance obtained in this work is the most outstanding in NiO/K₃Fe（CN）₆ system reported ever.We coated carbon layer on Fe₃O₄,which not only promoted the rate capability,but also lengthened the cycle life.We assembled it with HNO into a nickle-iron battery HNO//Fe₃O₄-C,which achieves an energy density 91.7 Wh kg^-1 at an average power density of 0.99 k W kg^-1.Most importantly,the energy density of the battery remain 38.9%of the initial value even after resting 12 hours,which is almost two times higher than that of NiO//Fe₃O₄-C.The creative achievements obtained in this work,especially the research on the self-discharge mechanism of NiO,shows a feasible direction for the promotion of nickle-iron batteries performance.