Accordion-Structured Hydrogel Battery Capable of Maintaining Ion Gradients for Extended Periods.

Inspired by the electric eel, biomimetic, biocompatible energy storage, and power generation technologies show promise for applications in portable and wearable electronic devices by mimicking the electric cell tandem structure of the electric eel and utilizing ionic gradients between hydrogel compartments to generate electricity. Previously, inspired by the unique morphology of the torpedo fish, an artificial flexible power source that can output a large current was introduced. This power source uses a hydrogel-infused paper hybrid to create, accordionize, and reconfigure arbitrary-sized gel films in series and parallel, and the power output of the flexible battery was significantly enhanced. However, maintaining the ionic gradient of hydrogel batteries during storage remains a challenge. Here, by borrowing the isolation properties of the accordion structure, we propose a unique paper accordion structure design to fabricate an Accordion-Structured Hydrogel Battery (ASHB). Pretreatment of hydrogel-injected paper strips improved storage stability and maintained the ionic gradient of hydrogel cells in the nonworking state, so that the cell's gradient retention time after the assembly is completed is increased by at least 30 h compared to stacking, and its per-cell operating voltage is still able to reach. The design also makes the assembly and use of flexible batteries more modular and holistic. In the future, it may be possible to power the cells with ions generated by the human body or the metabolites of living organisms, leading to the development of more efficient, sustainable, and eco-friendly power solutions.