The quantitative analysis of electrochemical impedance spectroscopy (EIS) data is important for both characterization and prognostic applications in many electrochemical systems. Here we describe an open-source platform, the ImpedanceAnalyzer, for easy-to-use physics-based analysis of experimental EIS spectra. To demonstrate the use of the platform, we explore the basic capabilities of the pseudo two-dimensional (P2D) battery model to predict publicly available experimental EIS data from a 1500 mAh commercial lithium-ion (LiCoO 2 /graphite) cell. An a priori computed dataset of 38,800 P2D-based impedance spectra simulations, covering a wide range of frequencies (1 mHz to 100 kHz) and model parameters, enables a straightforward least squares matching approach for analyzing experimental spectra. We find an average error of 1.73% between the best-matching computed spectrum from the 38,800 member library and the experimental spectrum being analyzed. Our analysis shows there is significant opportunity to improve the fit between experimental data and physics-based impedance simulations by a combination of a larger computed dataset, local optimization, and further additions to the model physics. Electrochemical impedance spectroscopy (EIS) is a powerful tool for investigating a wide variety of electrochemical systems. 1-3 EIS spectra separate individual electrochemical processes by their characteristic timescales, enabling both qualitative and quantitative analysis of electron transport, 4,5 reaction rates and mechanisms, 6,7 intercalation processes, 8 mass transport, 9,10 and electrode structure. 11,12 The noninvasive nature of EIS also makes impedance measurements useful in prognostic applications such as fuel cell health estimations 13,14 or prediction of remaining useful lifetime in batteries. 15,16 Qualitative analysis of EIS spectra generally involves assessing the shape of Nyquist plot features to determine the relative importance of different physicochemical processes. 17,18 In contrast, quantitative analysis relies on fitting a model to the data in order extract values for specific thermodynamic, transport, and/or kinetic parameters. Most experimental datasets are analyzed quantitatively using an equivalent circuit analog. Fitting an equivalent circuit to EIS data is straightforward using standard least squares regression techniques. 19,20 A good fit can often be found with a relatively simple equivalent circuit, particularly if non-ideal elements like the constant phase element are used. Moreover, many simple equivalent circuits, like the Randles' circuit, 21 have physically interpretable parameters based on linearized electrochemical processes. However, as more complex equivalent circuits are derived and utilized, the lumped parameters can lose their direct physical interpretability and the structure of the equivalent circuit analogs themselves can be degenerate. 22 An alternative to equivalent circuits for quantitative analysis of EIS data is to directly fit the data with a physics-based mathematical model ...