Nonlinear (higher) harmonic analysis has been shown to be a powerful tool for characterizing complex electrochemical systems such as corrosion,2 hydrodynamic voltammetry,3 and solid oxide fuel cells4by providing rich information difficult or impossible to measure using typical linear impedance alone. Here we apply this extension of EIS, known as nonlinear EIS (NLEIS), to the study of lithium-ion batteries.
The price one pays for the greater information content of NLEIS experiments is the additional analysis required to interpret details of the harmonic response from the battery system. We address this analysis challenge by extending the impedance modeling work of Doyle, Meyers, and Newman5 into the nonlinear domain. We solve the frequency domain formulation of the pseudo 2-D battery model to efficiently compute the physics of the harmonic spectrum of the battery. The experimental results and modeling work are described in detail over the mHz to kHz frequency range needed to probe the full set of battery physicochemical processes. The results show the power of nonlinear impedance techniques for the analysis of lithium-ion batteries with an emphasis on the new physics revealed when one moves from the linear to the nonlinear regime.
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2. Darowicki, K. & Majewska, J. Harmonic Analysis Of Electrochemical and Corrosion Systems-A Review. Corros. Rev. 17, 383–400 (1999).
3. Medina, J. A. & Schwartz, D. T. Nonlinear Dynamics of Limiting Current in the Flow-Modulated Uniform-Injection Cell. J. Electrochem. Soc. 144, 155–164 (1997).
4. Wilson, J. R., Schwartz, D. T. & Adler, S. B. Nonlinear electrochemical impedance spectroscopy for solid oxide fuel cell cathode materials. Electrochimica Acta 51, 1389–1402 (2006).