Persistently self-powered wearable thermoelectric generator enabled by phase-change inorganics as the heat sink

Wearable electronics improve our lives such as work efficiency, health and lifestyle. Wearable thermoelectric generators (w-TEGs) offer a persistent solution to the power unit, but the low efficiency and toxicity of which limited its widespread application. The development of heat sink that increases the temperature difference is the key to improve thermoelectric conversion efficiency. In this work, an environmentally friendly and high-performance flexible inorganic phase change material (IPCM) was developed as the heat-sink of w-TEG. Thanks to the large latent heat of the phase change near 300 K, calcium chloride hexahydrate (CaCl2•6H2O) embedded in organics acts as an excellent heat reservoir enabling a persistent flexible sink for efficient w-TEGs. It turns out an over 35 μW/cm2 output lasting for 1.5 h (motionless) or over 8 h (motion) for a wrist w-TEG. Moreover, such a heatsink is resettable due to the phase-change reversibility, enabling a potential solution for persistently powering wearable sensors and functional devices.