A Biodegradable Gelatin-Based Hydrogel Polymer Electrolyte for Integrated Multimodal Physiological Signal Sensing and Long-Lifespan Rechargeable Zinc-Air Batteries.

The growing demand for wearable bioelectronics and energy devices requires reliable energy solutions with sustainable features, multimodal responsiveness, and improved electrochemical performance. Natural biomass-derived hydrogel polymer electrolytes are ideal candidates due to their high conductivity, safety, and environmental friendliness. Herein, we propose a biodegradable gelatin-based hydrogel polymer electrolyte (GBHPE) synthesized via one-pot free-radical polymerization of gelatin, acrylic acid, and acrylamide, followed by ZnO/KOH solution immersion for polyelectrolyte functionalization. The GBHPE exhibits excellent conductivity, stretchability, optical transparency, adhesion, moisture retention, biocompatibility, and biodegradability. Meanwhile, GBHPE shows high multimodal responsiveness and sensitivity for on-skin bioelectronics as a sensor to diverse pH, temperature, stress-strain, and bioelectric signals, effectively enabling human movement detection, temperature early warning, and underwater emergency Morse code communication. These results enhance GBHPE's practicality in flexible/wearable electronics and energy devices. Notably, the GBHPE performs exceptionally well in rechargeable zinc-air batteries (ZABs), delivering a prolonged cycling lifetime of 563.38 h, achieving a high specific capacity of 859.43 mAh·g-1, and demonstrating outstanding rate performance. Additionally, in Zn||Zn symmetric cells, it exhibits a 459.33 h deposition/stripping cycle life, reduced polarization, and effective dendrite suppression. Overall, this work provides a robust strategy for high-performance hydrogel polymer electrolytes, promising for integrated wearable bioelectronics and rechargeable ZABs.