A hydrogel thermoelectrochemical cell with high self-healability and enhanced thermopower both induced by zwitterions

Thermocells with high thermopower have received much attention in recent years owing to their capability of converting heat to electricity. In particular, endowing these thermocells with promising self-healability and stretchability after self-healing are of fundamental importance to self-powered wearable electronics. However, there is still a lack of such effective thermocells due to the contradictory characteristics of good self-healing properties and good thermopower enhancement. Herein, by employing a zwitterionic polymer (poly[2-(methacryloyloxy)-ethyl]dimethyl-(3-sulfo-propyl) ammonium hydroxide) P(SBMA), we have successfully fabricated a hydrogel thermocell with high self-healability (90%), stretchability after self-healing (325%) and enhanced thermopower (3.5 mV K⁻¹). In detail, we have not only proposed and verified that the zwitterion-boosted thermopower is due to the selective interactions between the cation in SBMA and Fe(CN)₆⁴⁻, but we have also realized self-healing and stretchability after self-healing in a hydrogel thermocell. In addition, the thermocell is still self-healable at a low temperature of −10 °C upon the addition of LiCl. The applicability of the hydrogel thermocell as a self-powered wearable energy converter is demonstrated by stably lighting an LED lamp and by the thermovoltage output under extreme conditions, including self-healing and stretching after self-healing. This work provides an effective strategy to develop promising thermocells for self-powered wearable electronics.