With both experimental inputs verified, the diffusion coefficients of Li + in NMC811 at various SoC obtained by the GITT and ICI method are exhibited in Figure . Overall, the results from the three analyses are close to each other and previously reported Li + diffusion coefficients in NMC811. Above 3.7 V, the match is especially close for the values from the GITT with 5-40 s interval and the ICI method. This is expected since the 𝑑𝐸 𝑑√𝑡 ⁄ values derived from both GITT and ICI method are in good agreement in Figure and the slopes of OCP from both methods are basically the same above 3.65 V. Below 3.7 V, differences between three analyses are obvious. In principle, the GITT results from the 50-150 s interval is the most credible one among the three because the interval contains the linear region of the E-√𝑡 plots at these SoC values. However, the extension of the data selection interval requires the increase in the time limit of semi-infinite diffusion (t << L 2 /D). The assumption is satisfied upon discharging due to the much lower diffusion coefficients, but not on charging. This issue will be discussed in details in Section 1 of the SI.