Here, all the fittings were performed with a fixed diffusion length L of 300 nm, approximately 1 to 2 times the size of primary particles. This choice was made primarily because the obtained diffusion coefficients are close in magnitude to those from LNMO electrodes. Additionally, different L values were also tested. The fitting results from different L values are shown in the Supplementary Materials (Table ). When L increases from 150 nm to 750 nm, D 1 and D 2 increase by a factor of 2.5. Other parameters stays the same except Λ, which shows changes with different L values. It might be due to the fitting process.