Cost-effective thermoelectric conversion from low-grade heat using a bimetallic sulfur-based thermally regenerative ammonia battery

Abstract

A bimetallic sulfur-based thermally regenerative ammonia battery (S-TRAB) equipped with Zn and S/Cu₂S electrodes is proposed as an efficient system for converting low-grade thermal energy into electricity. The S/Cu₂S electrode functions as the cathode in the discharging process and as the anode during charge, facilitated by the NH₃ ligand difference in the electrolyte. Thermal energy can be harnessed to dissociate NH₃ from the exhaust anolyte and then redistribute it to the fresh anolyte. The S-TRAB can operate with a high discharge voltage of 1.62 V and a low charge voltage of 0.96 V, yielding a peak power density of 769 W m⁻². Furthermore, the cascade Cu²⁺/Cu reaction by the catalysis of the Cu₂S electrode results in additional power generation, leading to a net energy density of 854 Wh m⁻³ and a thermoelectric efficiency of 0.97% (relative Carnot efficiency of 10.9%). With the use of inexpensive materials, the S-TRAB has a low industrial cost of $1.98 W⁻¹. This study highlights the potential of the S-TRAB system as a promising solution for thermoelectric conversion, offering high power density and conversion efficiency and paving the way for effective thermoelectric energy harvesting.