Enhanced discharge capacity of thermorechargeable batteries composed of Cd-PBA and a potential-matched PBA

Abstract

Thermorechargeable batteries (TBs), which can be charged by a temperature change ΔT via the difference in the electrochemical Seebeck coefficient α between the cathode and anode, are promising energy harvesters. In order to put TBs into practical use, it is necessary to increase the discharge capacity (Q_TB) per unit weight of the total active materials, which is governed by the temperature (; T is temperature) and capacity (; q is capacity) coefficients of the potential E of cathode and anode materials. Among the active materials, the cadmium Prussian blue analogue (Cd-PBA) with a large |α| and small β is an ideal anode material for TBs. Here, we developed a potential-matched cathode PBA by partially substituting the Co sites of Co-PBA with other transition metals. We found that the potential of Mn-substituted Co-PBA matches well with that of Cd-PBA. We demonstrated that Q_TB (=4.1–5.1 mA h g⁻¹) of CoMn-PBA/Cd-PBA TB is much larger than that (=0.7–1.1 mA h g⁻¹) of non-substituted Co-PBA/Cd-PBA TBs.