Bifunctional self-segregated electrolyte realizing high-performance zinc-iodine batteries

Abstract

Static rechargeable zinc-iodine (Zn-I₂) batteries are superior in safety, cost-effectiveness, and sustainability, giving them great potential for large-scale energy storage applications. However, the shuttle effect of polyiodides on the cathode and the unstable anode/electrolyte interface hinder the development of Zn-I₂ batteries. Herein, a self-segregated biphasic electrolyte (SSBE) was proposed to synergistically address those issues. The strong interaction between polyiodides and the organic phase was demonstrated to limit the shuttle effect of polyiodides. Meanwhile, the hybridization of polar organic solvent in the inorganic phase modulated the bonding structure, as well as the effective weakening of water activity, optimizing the interface during zinc electroplating. As a result, the Zn-I₂ coin cells performed a capacity retention of nearly 100% after 4000 cycles at 2 mA cm⁻². And a discharge capacity of 0.6 Ah with no degradation after 180 cycles was achieved in the pouch cell. A photovoltaic energy storage battery was further achieved and displayed a cumulative capacity of 5.85 Ah. The successfully designed energy storage device exhibits the application potential of Zn-I₂ batteries for stationary energy storage.