Extended Data Fig. 7: Spatial propagation of (de)lithiation heterogeneities at the surface and core of NMC811 agglomerates.

Charge-discharge cycle of NMC811 at C/2 and 2 C showing projections from shells at exterior and centre of agglomerate at set points during the cycle (letters A to F). For NMC811 the semi-major axes of the surface ellipsoid are 3.5, 2.8 and 6.5 μm, for the core it is 1.2, 1 and 1.8 μm. As for LCO some movement of intensity from the edges of the projection to the centre on delithiation and a reverse on lithiation can be observed, however the exact nature of the motion is unclear. For NMC811 there are a range of domains with different degrees of lithiation at the start of the charge, further complicating the analysis. Qualitatively it appears the overall difference in degree of lithiation within and between domains decreases on charge and increases once again on discharge. However, further work is required to fully interpret these observations. Data across the two C-rates represent measurements of identical agglomerates. At a rate of C/2: A – 3.85 V, B – 4.00 V, C – 4.17 V, D – 3.85 V, E – 3.73 V F – 3.55 V. At a rate of 2 C: A – 3.90 V, B – 4.01 V, C – 4.17 V, D – 3.72 V, E – 3.64 V F – 3.45 V.