Operando XRD patterns were recorded at 100 °C on the cathode side of pellets while galvanostatic discharging being performed. The 2-theta range was limited to 21.5°-40.5° with a scan time of 26 min as a compromise to record a representative and suitable angular range for later data analysis while optimizing the measurement time for both time resolution and signal-to-noise ratio. An incident slit size of 0.6° and a step size 0.005° were used in order to produce good signal intensities and data resolution. To obtain sufficiently time-resolved data allowing for both phase analysis and quantification, a loop measurement was programmed to record XRD patterns during galvanostatic discharge process, at 1-h intervals. Therefore, the corresponding specific capacity difference between two patterns obtained in this work is around 7 mAh g -1 . An image of the measurement setup is shown in Figure S 6Figure S 6a.