Fig. 6: Coverage of Li-dense and -dilute regions near the surface influences the overall lithium insertion impedance.

a Histogram of lithium concentration distribution on the surfaces of all measured particles, comparing 0-hour and 4-h relaxation periods. b A representative particle during relaxation at <x> = 0.95 after complete discharge. The pixel nearest to the surface is referred to as the surface pixel, and only these pixels are shown. Below each image, the surface coverage of Li-dilute (purple) and Li-dense (orange) pixels is indicated. c Evolution of charge-transfer resistance during discharge and subsequent relaxation processes. The inset schematic shows the electrical circuit used for in-situ GEIS fitting. d Overpotential derived from the bulk electrochemical curve of a 5 C charge after various relaxation times in the fully discharged state. e Schematics illustrating the expected changes in overall resistance with relaxation due to redistributions in the surface lithium concentration. Source data are provided as a Source Data file.