Wholly degradable quasi-solid-state thermocells for low-grade heat harvesting and precise thermal sensing

Abstract

Thermocells (TECs) have attracted increasing attention in the past decade due to their capability of directly converting low-grade heat into electricity. Various TECs with improved thermoelectrochemical performance and additional functionalities have been developed; however, little attention has been paid to TEC systems that are particularly associated with environmental challenges arising from end-of-life electronic waste. In this study, a novel approach to harnessing low-grade heat and precise thermal sensing through the design and implementation of wholly degradable quasi-solid-state TECs is introduced. Emphasizing sustainable energy solutions, these TECs utilize composite film electrodes and hydrogel electrolytes, exhibiting good thermoelectrochemical performance and mechanical flexibility with stable energy output under repeated large deformations. Moreover, these TECs are wholly degradable under mild conditions, presenting a significant advancement in minimizing environmental impact post-use. The practical applications of these TECs are validated in flexible integrated devices for body heat harvesting and smartphone temperature monitoring, achieving device-level degradability within 8 hours and energy-autonomous precise thermal sensing with less than 1% deviation. This study bridges the gap between efficient low-grade heat harvesting and environmental sustainability goals, marking a step forward in the field of sustainable energy technologies.