"Membrane-Free Battery for Harvesting Low-Grade Thermal Energy"

Yuan Yang : James Loomis, Hadi Ghasemi, Seok Woo Lee, Yi Jenny Wang, Yi Cui, and Gang Chen; Nano Letters, 10/13/14.

Additional Authors: James Loomis, Hadi Ghasemi, Seok Woo Lee, Yi Jenny Wang, Yi Cui, and Gang Chen

Abstract:

Abstract Image

Efficient and low-cost systems are desired to harvest the tremendous amount of energy stored in low-grade heat sources (<100 °C). An attractive approach is the thermally regenerative electrochemical cycle (TREC), which uses the dependence of electrode potential on temperature to construct a thermodynamic cycle for direct heat-to-electricity conversion. By varying the temperature, an electrochemical cell is charged at a lower voltage than discharged; thus, thermal energy is converted to electricity. Recently, a Prussian blue analog-based system with high efficiency has been demonstrated. However, the use of an ion-selective membrane in this system raises concerns about the overall cost, which is crucial for waste heat harvesting. Here, we report on a new membrane-free battery with a nickel hexacyanoferrate (NiHCF) cathode and a silver/silver chloride anode. The system has a temperature coefficient of −0.74 mV K–1. When the battery is discharged at 15 °C and recharged at 55 °C, thermal-to-electricity conversion efficiencies of 2.6% and 3.5% are achieved with assumed heat recuperation of 50% and 70%, respctively. This work opens new opportunities for using membrane-free electrochemical systems to harvest waste heat.