High-Performance Cu-Based Liquid Thermocells Enabled by Thermosensitive Crystallization and Etched Carbon Cloth Electrode

Abstract Thermocells are garnering increasing attention as a promising thermoelectric technology for harvesting low-grade heat. However, their performance is often limited by the scarcity of high-performance redox couples that possess both high thermopower and rapid redox kinetics. This work addresses this challenge by leveraging our recently developed copper (I/II) (Cu + /Cu 2+ ) redox couple. We significantly enhance the performance of Cu-based liquid thermocells by integrating a thermosensitive crystallization process with etched carbon cloth electrodes, achieving synergistic improvements in thermodynamic and kinetic performance. The thermosensitive crystallization process establishes a persistent Cu 2+ concentration gradient, boosting the thermopower from 1.47 to 2.93 mV K −1 . Moreover, the etched carbon cloth electrodes provide a larger electroactive surface area and demonstrate a higher current density. Consequently, the optimized Cu + /Cu 2+ system achieved an exceptional normalized power density P max ( ΔT ) −2 of 3.97 mW m ‒2 K −2 . A thermocell module comprised of 20 cells directly power various electronic devices at a temperature difference of 40 K. This work successfully exhibits potential of Cu + /Cu 2+ redox couple in thermoelectric conversion and introduces a valuable redox couple for high-performance thermocells.