Polyacrylamide soft colloidal electrode for long-lasting aqueous Zn-I batteries

Aqueous Zn-I batteries hold great potential for stationary energy storage applications. However, their development is challenged by limited device innovation, hindering improvements in long-term operation. In this study, we report an aqueous Zn-I battery design that leverages the water distribution control effect of sulfate ions (SO₄)²⁻. Due to their strong water affinity compared to polyacrylamide (PAM), (SO₄)²⁻ ions induce phase separation of PAM from the aqueous electrolyte, preventing its dissolution. By introducing iodide species within the PAM soft colloid, we construct an aqueous Zn-I battery. Comprehensive electrochemical performance evaluations, including rate capability, cycling stability, fast-charging, fluctuating charge conditions, various states of charge, and self-discharge performance, demonstrate long-term cycling stability over 30,000 cycles with a 94.3% capacity retention. Moreover, we demonstrated its compatibility with practical solar panels, suggesting its potential for integration with sustainable energy resources in the future. This study provides solid innovation in advancing aqueous Zn-I battery technology.