The Improved Performance of Gel Thermoelectric Chemical Cells by Designing a Concentration Gradient of Electrolyte and Asymmetric Electrodes

The use of gel thermoelectric chemical cell s to capture low-grade heat for the conversion to electricity is receiving considerable attention. However, improving the open-circuit voltage (Voc) and output power (P) of the cells is still an open problem. Herein, we demonstrate a thermoelectric chemical cell (Cu-cgTEc-C) in which the gel electrolyte contains a concentration gradient of potassium ferrocyanide and potassium ferricyanide (Fe(CN)64–/Fe(CN)63–), while the asymmetric electrodes include a copper foil and a carbon electrode. Benefiting from the effect of the concentration gradient of (Fe(CN)64–/Fe(CN)63–) in the gel electrolyte and the application of asymmetric electrodes, the Voc, P, and Seebeck coefficient (Se) of the Cu-cgTEc-C cell are 0.450 V, 183 μW, and 7.82 mV K-1, respectively. These values exceed those of the comparison cells in which the electrolyte has no concentration gradient or the electrodes are symmetrical electrodes. For the continuous charge and discharge test of a single Cu-cgTEc-C cell, the normalized power density and energy density are 1.40 mW m-2K-2, and 12.0 J m-2, respectively. This work not only provides an excellent thermoelectric chemical cell but also a novel idea in gel-based cell design.