Enhancing the Cycle Life of Zn3[Fe(CN)6]2/Zn Aqueous Batteries through Simultaneous Interfacial Regulation on Both Cathode and Anode

As promising candidates for large-scale energy storage applications, aqueous zinc ion batteries (AZIBs) face challenges due to the electrochemical instability of cathode materials and Zn anodes. Introducing additives into the electrolyte is an effective approach to improving the compatibility of electrodes. In this work, trace amounts of poly(acrylic acid) (PAA) are utilized as electrolyte additives in 1.0 M ZnSO4 to enhance the cycle performance of the Zn3[Fe(CN)6]2/Zn battery. PAA demonstrates strong interfacial engineering ability on both the cathode and anode. PAA directly reacts with the Zn anode, leading to the formation of PAA–Zn films growing on the anode surface. The interfacial film inhibits the parasitic hydrogen evolution reactions, reducing the generation of byproducts. Regulating the anode's interfacial structure promotes the uniform deposition of Zn. The electrolyte with 0.8 wt % PAA additives enables a long cycle life exceeding 300 h at 5 mA·cm–2 and 2.5 mAh·cm–2 in Zn/Zn symmetric cells, along with a high Coulombic efficiency of 98.07% in Cu/Zn asymmetric cells. Meanwhile, PAA preferentially adsorbs on the surface of the Zn3[Fe(CN)6]2 cathode, inhibiting the dissolution of ferricyanide anions in aqueous solution and reducing the self-discharge behavior. Thanks to the interfacial regulation of PAA on both the cathode and anode, the cycle performance of the Zn3[Fe(CN)6]2/Zn full cell is significantly enhanced to nearly six times that without PAA additives. This work lays the groundwork for the development of electrolyte additives that can improve the electrochemical performance of both the cathode and anode of AZIBs.