, where 𝜂 is the volume fraction occupied by the solid electrolyte and 𝐷 𝑒𝑓𝑓 is the effective diffusion coefficient. 𝐷 𝑒𝑓𝑓 is in turn calculated by solving Fick's first law in the solid electrolyte domain, with a concentration difference 𝛥𝑐 between the outer xy planes. 𝐷 𝑒𝑓𝑓 is obtained from the overall diffusive flux 𝑗 as: 𝐷 𝑒𝑓𝑓 = -𝑗 × length /𝛥𝑐. Since τ geo is a purely geometrical magnitude, it is independent of the values chosen for 𝛥𝑐 and the diffusion coefficient. Periodic boundary conditions were considered for the outer xz and yz planes.