Alternating Current Methods for Battery Evaluation

Abstract

AbstractThe alternating current (AC) method is a powerful electrochemical measurement tool to evaluate the performance of batteries because the time constants in electrochemical signals can be discriminated without damage to the electrodes. An electrochemical impedance is determined by measuring the alternating current response to the alternating voltage imposed on the electrode/electrolyte interface. The electrode/electrolyte interface can be characterized by the interpretation of the electrochemical impedance spectrum. The AC method was recently called electrochemical impedance spectroscopy (EIS) because the impedance spectrum measured in a wide frequency range provides information concerning the detailed structure of the electrode/electrolyte interface. The typical interpretation of an impedance spectrum is explained using a simple equivalent circuit (Fig. 11.1). Figure 11.1a shows a conceptual scheme of an electrode contacted with an electrolyte. The anodic or cathodic reaction rate at the electrode/electrolyte interface has to do with the charge-transfer resistance R ct. In addition, an electric double layer is formed at the interface, and the double-layer capacitance is represented by C dl. Figure 11.1b describes an equivalent circuit involving R ct in parallel with C dl, which is in series with the electrolyte resistance R ele.KeywordsEquivalent CircuitImpedance SpectrumNyquist PlotAlternate CurrentConstant Phase ElementThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.