where ΔEOC is the change in the open-circuit potential (OCP) from the rests before and after the current pulse, and ΔtI is the period of the current pulse (denoted as τ in the original paper 1 ). It is worth noting that Equation applies to the concentration of the entire electrode. In order to relate the measured electrode potential, which reflects the surface concentration, to the bulk concentration, the measurement should ideally be done when the concentration is uniform throughout the electrode. This is indicated by the fully relaxed electrode potential, i.e. dE/dt = 0, also known as the open-circuit condition. In practice, it takes long time to achieve equilibrium in the electrode, which is the reason for the substantial time consumption of GITT. 𝑑𝐸 𝑑√𝑡 ⁄ is the slope on the plot of E against √𝑡. In the original GITT paper, 1 Equation 16 is further reduced by assuming that E is linear to √𝑡 during the whole current pulse. However, this assumption is less likely to hold for electrode particles in a composite electrode since the duration for the semi-infinite diffusion condition, t << L 2 /D, is reduced by the shorter L, compared to the bulk electrode used in the original paper. Two solutions to solve the issue are: 1) selecting only the data lying in the linear region on the E-√𝑡 plot or 2) fitting the data with the full solution (Equation ) to Fick's second law (method P3 and P5 in the reference, respectively). In this work, we will proceed with the first solution and examine the effect of data selection on the GITT analysis.