Self-adaptive thermoelectric conversion under day-night large temperature differences enabled by superior thermal management capacity of phase change brine gels with high latent heat and high thermal conductivity

Thermoelectric conversion is a promising clean way to generate electricity. To efficiently utilize the large temperature differences naturally found in plateau regions, it is urgent to develop novel and compatible thermoelectric conversion technologies. Here, a self-adaptive thermoelectric conversion strategy is reported for conditions involving day-night large temperature differences enabled by superior thermal management capacity of phase change brine gels (PCBGs) with high latent heat and high thermal conductivity. The segmental adsorption of cold-storage brine by agar and the porous adsorption by expanded graphite (EG) synergistically enable high brine loading in the gel, yielding enthalpy and enthalpy efficiency values of 261.79 J·g −1 and 93.75 %, respectively. PCBGs also demonstrate excellent leakage resistance and cyclic stability. Surface modification of EG with gallic acid produces an evenly distributed composite of phase change brine and EG, yielding a thermal conductivity of up to 5.212 W·m −1 ·K −1 . PCBG is integrated with thermoelectric panel to form a self-adaptive thermoelectric conversion device. PCBGs take advantage of natural nighttime cooling to store cold, thereby providing a large temperature difference of 42°C for thermoelectric devices operating during the day. The output voltage and power reach 0.33 V and 14 mW, respectively. This work effectively mitigates the temperature impact of the plateau climate on thermoelectric devices, offering new insights into green power generation.