As described in section 2, we carried out large scale MD simulations to explore Li diffusion at different stages, Li contents and temperatures. Figure tween different stages. On the other hand, using AC impedance method, the D versus x curve reported in Piao et al's work does not exhibit the phase transition induced diffusivity drop character. Instead, the D value decreases significantly at 0 < x < 0.5 from 10 -9 to 10 -11 cm 2 /s. Interestingly, in Park et al's work, an opposite trend was observed, with D increasing from 10 -11 to 10 -10 cm 2 /s at 0 < x < 0.5. Moreover, experimental data of D in graphite is also inconsistent and spans 10 - to 10 -16 cm 2 /s . Apart from different measuring methods, particle size and shape of the graphite electrode as well as its surface area in contact with the electrolyte solution could all contribute to the inconsistent D values . Though our calculated D values are within this range, it is difficult to compare the absolute values of each.