3. In the case of Li 3 PS 4 , GBs also lead to an increased degree of reorientation by polyanions. Our simulations reveal that GBs have a significant effect on the timescale of the correlation of Li-ion diffusion in solid electrolytes even where the diffusivity is relatively unaffected. Incorporated polyanions able to undergo reorientation can act to maintain coordination environments in the vicinity of the GB, enabled more facile diffusion.