UC Berkeley

The intersection of heat transfer and electrochemistry has been traditionally limited to understanding temperature rise in electrochemical systems and implementing heat transfer principles for battery thermal management. However, the link between electrochemistry and thermal transport is more fundamental. Electrochemical processes, through reversible or irreversible entropy change, generate heat and have their unique thermal signatures. Additionally, temperature influences the transport and kinetic processes within an electrochemical system. In this work, we utilize this relationship between electrochemical processes, heat generation and thermal transport to develop thermal metrologies that are capable of providing significant electrochemical insights that traditional electrochemical methods cannot. To do so, we first develop the basic understanding of thermal transport in electrochemical systems and formulate the concept of different types of heat generation resulting from different electrochemical processes. Additionally, we formulate a new calorimetry technique to quantify the heat generation rate in large cells and extend an existing thermal metrology (the 3ω method) to provide insights into morphological changes at an electrochemical interface, namely the lithium metal-solid state electrolyte interface. Finally, we combine the principles of frequency domain heat generation of electrochemical processes with frequency domain thermal transport analysis to come up with a new electrochemical-thermal metrology Multiharmonic ElectroThermal Spectroscopy (METS), capable of spatially resolving thermal signatures to allow accurate measurement of thermodynamic (entropic), transport and kinetic properties with a spatial resolution of microns.