The theoretical capacity value for the cell was calculated based on the area of the electrode main body (30 mm 2 ) and the areal loading of the NMC811 electrode used, assuming the tab contribution was negligible to the overall total capacity. For the cell which contained 2.2 mAh cm -2 electrode the theoretical capacity calculated was 6.4 mAh. A lowcurrent potentiostat (SP-300, Bio-logic SAS) was used and a constant-current constantvoltage (CC-CV) charge protocol was employed to charge each cell to the voltages as stated (3.8 V, 4.0 V, 4.1 V, 4.2 V, 4.3 V, 4.4 V vs Li/Li + ) before discharging to the same voltages. A C/3 rate based on the theoretical capacity calculated was used, and the cells were allowed to rest after the CV step and the current had dropped below the C/20 threshold. During this rest period tomograms were obtained. To age the cell, 10 further cycles we conducted at 1C to between 2.5 and 4.4V without a constant voltage step. The cell was then imaged after the final discharge to 2.5 V. See figure in the SI for full electrochemical data.