Gigantic effect due to redox electrodes on thermoelectric properties of ionic thermoelectric devices

Breakthroughs in thermoelectric converters based on ionic conductive materials have opened up new possibilities in low-grade waste heat harvesting and wearable electronic applications. In order to increase energy output of thermoelectric devices, electrodes with higher specific capacitance are required to increase the energy density and power density of thermoelectric devices. In this work, Prussian blue graphite (PB-G) electrode sheets are prepared by electrodepositing Prussian blue onto graphite electrodes to obtain highly efficient flexible electrode materials for thermoelectric devices. The PB-G electrode was assembled with ion-conductive hydrogel to form a thermoelectric device. The specific capacitance of the PB-G electrode calculated by a galvanostatic charge-discharge was 1254.6 F·m−2, which was 710.3 F·m−2 higher than that of the graphite electrode (544.3 F·m−2). A significant enhancement was made in the instantaneous power density (∆T=30 K, 1145.45 mW·m−2) of the PB-G based thermoelectric devices by 14.71 times and a high output energy density foy 1.5 h (23.12 J·m−2) by 53 times than graphite electrode based thermoelectric devices. This work presents a new solution for increasing the output power of thermoelectric devices which could lead to a new vista for the application of low thermal energy acquisition in tunable ion thermoelectric (i-TE) devices.