The presence of γ has been linked to poor electrochemical performance in experiments. For the exhausted particle, the amount of trapped Li may exceed 25% due to sluggish kinetics throughout the charge process, which could explain the observation of charged particles stuck at higher Li contents in a recent NMR study. Atomistic Origin. The different effects of the two surface phases can be understood from the Li-hopping energy landscapes in Figure . Conductivity is determined by the product of carrier concentration and mobility (diffusivity). It is important to note that in the pristine and fatigued particles, respectively. In the pristine particle, the H3 phase grows inwards from the surface; while in the fatigued particle, it grows outwards from the center of the particle. Figure ) show the 3D structure of the remaining Li. The H3 phase expands across all Li layers in both cases, reflecting the strong attraction between Li in neighboring layers. In summary, the β phase exhibits high Li mobility/diffusivity, allowing fast Li transport as long as free Li are available to serve as carrier. However, it supresses carrier formation in the H2 phase during charge by sealing the surface and pining nearby Li. During discharge, carriers are injected from outside, so Li transport remains unimpeded by the presence of the β phase.