Impedance spectroscopy applied to lithium battery materials: good practices in measurements and analyses

This paper outlines a critical analysis of the currently available methodological framework for a comprehensive and reliable interpretation of impedance spectroscopy data of aprotic lithium-based secondary batteries. Impedance spectroscopy is a powerful experimental technique that can be used to assess the impedance of batteries over a range of frequencies. However, in typical battery configurations, all components contribute to the impedance response of the whole cell and the overlap of many of the different impedance responses often results in a complex experimental curve that is not easily easy to interpret. Various analytical approaches can be used to evaluate complex impedance data sets of batteries: (a) matching the impedance response of the cells in question with a previously published impedance model; (b) performing additional electrochemical measurements with different settings and/or on different cell designs to support the assignation of impedance contributions to specific physicochemical processes; (c) acquiring external physicochemical determinations, morphological and chemical data that can support or refute the results of impedance analysis; (d) developing theoretical models that reconcile physical insights at different length scales of the battery components with the equivalent circuit formalism.