Low-grade heat boost for rechargeable batteries

Jointly led by Professor Hyun-Wook Lee and Professor Dong-Hwa Seo from the School of Energy and Chemical Engineering at the Ulsan National Institute of Science and Technology (UNIST), South Korea, in collaboration with Professor Seok Woo Lee from Nanyang Technological University, Singapore, the work focused on developing a highly efficient Thermally Regenerative Electrochemical Cycle (TREC) system capable of converting small temperature differences into usable energy.

According to the team, conventional energy-harvesting systems face challenges when it comes to effectively utilising low-grade heat sources, but TREC systems offer a viable solution as they integrate battery functionality with thermal-energy-harvesting capabilities. In this study, the research team investigated the role of structural vibration modes to enhance the efficacy of TREC systems.

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By analysing how changes in covalent bonding influence vibration modes - specifically affecting structural water molecules - the researchers discovered that minute amounts of water induce strong structural vibrations within cyanide ligands’ A1g stretching mode. These vibrations contribute to a larger temperature coefficient within a TREC system and, based on these insights, the team designed and implemented a highly efficient TREC system using a sodium-ion-based aqueous electrolyte.