EIS data at 50% SOC (3.82 V vs. Li/Li + ) and its fitted data are shown in Figure (b) and (c). The major time constant is attributed to the charge transfer resistance coupled with the double-layer capacitance. The low frequency impedance exhibits anomalous diffusion behavior, which can be accurately fitted by the PDW model. The fitting residual is approximately xix two orders of magnitude lower than the EIS modulus, indicating a generally good fit. The similar fitting quality has been achieved for the entire dataset. The fitted parameters and their relative errors are listed in Table .