Battery use is growing rapidly in consumer electronics, vehicles, and grid applications. In nearly all applications, there is a desire to operate the battery aggressively (i.e., faster charging, deeper discharging, etc.) without compromising safety or cycle life.
Unfortunately, most batteries are operated conservatively owing to poor diagnostic insight into the internal states of the battery. We describe the use of moderate amplitude current perturbations to drive batteries into the weakly nonlinear regime, where the fundamental and higher harmonic response of the voltage provides new insights into battery states. Experiments and simulations are combined to illustrate the physics and chemistry that is accessible with this form of nonlinear electrochemical impedance spectroscopy. As with nonlinear optical techniques, we show that the second harmonic response is sensitive to symmetry breaking in the charge transfer reaction at either electrode, with the frequency of symmetry-breaking being characteristic of the positive or negative electrodes. Our long term goal is to combine this physics-rich probing of batteries with statistical predictors to estimate the state of health and remaining usable life of a battery, opening new avenues for more aggressive battery management.
Daniel Schwartz is the Director of the Clean Energy Institute and is currently Boeing-Sutter Professor of Chemical Engineering at the UW.
He received his Ph.D. in Chemical Engineering from the University of California, Davis in 1989. Prof. Schwartz is a Fellow of the Electrochemical Society and has been recognized for his contributions by awards from the NSF, DOE, ECS, and others. He served on the Technical Advisory Board for the State’s Energy Strategy and is a current board member for the Washington Clean Tech Alliance. His research explores transport and reaction in electrochemical systems, including the performance of complex electrodes used in energy storage and conversion.