Polyethylene glycol-based colloidal electrode via water competition for ultra-stable aqueous Zn-I batteries

Summary: Current solid- and liquid-state electrode materials with extreme physical states show inherent limitation in achieving the ultra-stable batteries. Herein, we present a colloidal electrode design with an intermediate physical state to integrate the advantages of both solid- and liquid-state materials. The colloidal electrode was designed based on the inherent water competition effect of (SO4)2− from the aqueous electrolyte and inherently water-soluble polyethylene glycol (PEG)/ZnI2 from the cathode. The constructed aqueous Zn||PEG/ZnI2 colloid battery demonstrated ultra-stable cycling performance with Coulombic efficiencies approaching 100% and a capacity retention of 86.7% over 10,700 cycles, without requiring anodic modification. In addition, the battery also exhibits compatibility with multiple operating conditions including fluctuating charging, limited self-discharging rate, different charging statuses, and fast charging. Moreover, the battery also shows practical potential by integrating with a photovoltaic solar panel charging. This design provides a broad platform for building the next-generation aqueous batteries with ultra-long lifetime.