Fire-retardant polyampholyte-alginate organogel electrolyte for stable zinc-ion batteries

Although Li-ion batteries dominate the energy storage market, they suffer from flammability and safety issues, highlighting the need for safer alternatives. Aqueous zinc-ion batteries (ZIBs) are safe, eco-friendly, and inexpensive. However, they face challenges, including hydrogen evolution, dendrite growth, limited temperature tolerance, and poor cycling stability. Hydrogel electrolytes provide flexibility and ionic conductivity but are limited by deformation-induced failure and side reactions. Herein, we developed a polyampholyte/sodium alginate (PA/SA) organogel electrolyte using ethylene glycol and Zn (BF₄)₂ as flame retardants to overcome these limitations. The Polyampholyte network promoted ion dissociation, resulting in a high ionic conductivity of 4.36 × 10⁻³ S cm⁻¹, while alginate reinforced the gel through Zn²⁺ crosslinking, leading to an enhanced mechanical strength of 109.84 kPa. The PA/SA organogel exhibited extended cycling stability of 1000 h in Zn||Zn symmetric cells, far surpassing the 400 h stability of aqueous electrolyte. In full-cell tests with NaVO cathodes, the system achieved an initial discharge capacity of 126 mAh g⁻¹ and, after 1900 cycles, maintained nearly twice the capacity retention compared with liquid electrolytes. The flexibility and durability of the electrolyte make it particularly attractive for flexible and biocompatible energy storage, offering a promising pathway for next-generation portable and wearable electronics.