  Grain boundary migration is driven by the boundary's curvature and external
loads such as temperature and stress. In intercalation electrodes an additional
driving force results from Li-diffusion. That is, Li-intercalation induces
volume expansion of the host-electrode, which is stored as elastic energy in
the system. This stored energy is hypothesized as an additional driving force
for grain boundaries and edge dislocations. Here, we apply the 2D
Cahn-Hilliard$-$phase-field-crystal (CH-PFC) model to investigate the coupled
interactions between highly mobile Li-ions and host-electrode lattice
structure, during an electrochemical cycle. We use a polycrystalline
FePO$_{4}$/ LiFePO$_{4}$ electrode particle as a model system. We compute grain
growth in the FePO$_{4}$ electrode in two parallel studies: In the first study,
we electrochemically cycle the electrode and calculate Li-diffusion assisted
grain growth. In the second study, we do not cycle the electrode and calculate
the curvature-driven grain growth. External loads, such as temperature and
stress, did not differ across studies. We find the mean grain-size increases by
$\sim11\%$ in the electrochemically cycled electrode particle. By contrast, in
the absence of electrochemical cycling, we find the mean grain-size increases
by $\sim2\%$ in the electrode particle. These CH-PFC computations suggest that
Li-intercalation accelerates grain-boundary migration in the host-electrode
particle. The CH-PFC simulations provide atomistic insights on
diffusion-induced grain-boundary migration, edge dislocation movement and
triple-junction drag-effect in the host-electrode microstructure.
