Another common approach is based on Fickian diffusion theory, where the anomalous diffusion behavior is originated from inhomogeneous diffusion paths . Levi et al. and Osaka et al. have proposed to incorporate more than one Warburg element in EECM to tackle the anomalous diffusion impedance. This empirical adaptation is easy to implement and leads to good fitting results, but this comes at the cost of physical interpretability. Diard et al. proposed using a log-normal distribution of diffusion lengths to describe the inhomogeneous diffusion behavior, and the-oretical expressions of diffusion impedance were derived accordingly. Later, Song et al. took both distribution of diffusion lengths and diffusion geometry into account for the Warburg diffusion model, which was validated on Si nanowire electrodes. In practice, the estimation of the distribution of diffusion lengths as well as the diffusion geometry from LIBs is extremely challenging. Lately, Min et al. revealed that the characteristic diffusion length is independent from the secondary particle size for Li(NiMnCo)O 2 (NMC) cathode materials by conducting advanced single particle measurements. They attributed this unexpected observation to the cracks formation and electrolyte penetration on the secondary NMC particles as discussed in many previous studies . This could result in shorter diffusion lengths, and irregular diffusion geometry.