Environmentally Friendly Phytic Acid Additive Enabling Simultaneous Optimization on Electrode Interface and Coordination Environment for Stable Aqueous Zinc-Ion Batteries

Despite with advantages of water compatibility, low cost, high safety and capacity, aqueous zinc ion batteries (ZIBs) are facing challenges from zinc dendrite, side reactions and low coulombic efficiency, which limits their broad application and mass production. In this paper, phytic acid (PA), an inositol polyphosphate, is introduced as an additive in 1M ZnSO₄ electrolyte to suppress zinc dendrite and H₂ evolution. The simulation and experimental results show that the phytic acid additive can absorb on the zinc anode surface, covering the active sites for H₂ production and guiding the uniform diffusion and deposition of zinc ions. Besides, PA has six phosphate groups, with each phosphorus atom bounding to 4 oxygen atoms. The electronegative oxygen atoms have a strong affinity to Zn²⁺, and can compete with water molecules in the Zn (H₂O)₆²⁺, changing the coordination environment of zinc ions. With PA additive, the zinc dendrite and side reactions are suppressed, and a high coulombic efficiency of 99.4% and long cycling stability of more than 1200cycles can be obtained at the current density of 1mA cm^-2 and capacity of 1mAh cm^-2. When coupling with I₂/AC cathode, the full cell with PA additive delivers a high capacity of 120mAh g^-1 at current density of 1A g^-1, and can stably cycle for more than 3000cycles, while the battery using 1M ZnSO₄ failed at 1300cycles. This work provides a simple but promising approach to the development of high-performance aqueous ZIBs.