Ionic Thermoelectric Materials with Long Operation and High Energy Density

Abstract Ionic thermoelectrics (i-TE) possesses great potential in powering distributed electronics, because it can generate thermopower up to tens of millivolts per Kelvin 1, 2. However, due to the fact that ions cannot enter external circuit, the utilization of i-TE is currently based on capacitive charge/discharge 3, which results in discontinuous working mode and low energy density 4. Here, we introduce an ion-electron thermoelectric synergistic (IETS) effect by utilizing an ion-electron conductor. Electrons/holes can drift under the electric field generated by thermodiffusion of ions, thus converting the ionic current into electrical current that can pass through the external circuit. Due to the IETS effect, i-TE is able to operate continuously for over 3000 min. Moreover, our i-TE exhibits a thermopower of 32.7 mV K-1 and an energy density of 553.9 J m-2, which is more than 6.9 times of the best reported value. Consequently, direct powering of electronics by i-TE is realized. This work provides a new strategy for the design of high-performance i-TE materials.