Robust, Efficient, and Recoverable Thermocells with Zwitterion‐Boosted Hydrogel Electrolytes for Energy‐Autonomous and Wearable Sensing

Abstract The rapid growth of flexible quasi‐solid‐state thermocells (TECs) provides a fresh way forward for wearable electronics. However, their insufficient mechanical strength and power output still hinder their further applications. This work demonstrates a one‐stone‐two‐birds strategy to synergistically enhance the mechanical and thermoelectrochemical properties of the [Fe(CN)6]3−/4−‐based TECs. By introducing Hofmeister effect and multiple non‐covalent interactions via betaine zwitterions, the mechanical strength of the conventional brittle gelatin hydrogel electrolytes is substantially improved from 50 to 440 kPa, with a high stretchability approaching 250 %. Meanwhile, the betaine zwitterions strongly affect the solvation structure of [Fe(CN)6]3− ions, thus enlarging the entropy difference and raising the thermoelectrochemical Seebeck coefficient from 1.47 to 2.2 mV K−1. The resultant quasi‐solid‐state TECs exhibit a normalized output power density of 0.48 mW m−2 K−2, showing a notable improvement in overall performance compared to their counterparts without zwitterion regulation. The intrinsic thermo‐reversible property also allows the TECs to repeatedly self‐recover through sol‐gel transformations, ensuring reliable energy output and even recycling of TECs in case of extreme mechanical damages. An energy‐autonomous smart glove consisting of eighteen individual TECs is further designed, which can simultaneously monitor the temperature of different positions on any touched object, demonstrating high potential in wearable applications.