| sXRD maps, graphite (002), NMC811 (101), and NMC811 (003) | Spatially uniform at all measured voltages, with no distinct domains or sharp gradients |
|---|---|
| NMC811 (003) | Expanded up to approximately 4.0 V, then contracted at higher voltages |
| NMC811 (101) | Evolved more weakly and plateaued at higher voltages |
| Graphite (002) at 2.5 V | Mild spatial gradient before charging; disappeared on charging |
| Graphite (002) at 4.0 and 4.3 V | Uniform shift to positive values |
| Discharge return | Reflections returned close to their initial positions; small residual positive offset near the electrode edges in graphite (002) |
| Inactivity-map Dice coefficient at the 0.85 threshold | 0.00 |
Arthur Fordham, Thomas Dore, Yuhan Liu, Liam Bird, Pranay Gandharapu, Alice Llewellyn, Robert Scott Young, P. M. Anuradha Bandaranayake, Ashok S Menon, Eleni Fiamegkou, Stefan Michalik, Genoveva Burca, Alexander J. E. Rettie, Paul R. Shearing, Thomas Miller, James B. Robinson, Louis Piper, Rhodri Jervis. “The influence of formation protocol on heterogeneous degradation of lithium-ion pouch cells revealed by spatially resolved synchrotron X-ray diffraction.” ChemRxiv (). https://doi.org/10.26434/chemrxiv.15007496/v1
| Spatial lattice response | Heterogeneous, with circular inactive areas especially at the bottom and right, farthest from the tabs |
|---|---|
| Graphite (002), 3.35–3.55 Å | Voltage-dependent splitting and asymmetry, with a second peak at intermediate and high states of charge |
| NMC811 (003), 4.7–4.9 Å | Simultaneous broadening and nonlinear shifts with voltage |
| NMC811 (101), dark-blue spots at 2.5 V | Likely artefacts from local peak-fitting instabilities or detector effects |
| Inactivity-map Dice coefficient at the 0.85 threshold | 0.37 |
| sXRD response | Largely homogeneous |
|---|---|
| Graphite (002) | Small inactive region near the lower-left edge of the tabs |
| Peak definition and reversibility | Peaks remained well defined and largely reversible; voltage-induced shifts remained parallel across state of charge |
| NMC811 (003) | Comparatively sharp and symmetric |
| Spatially averaged XRD | Systematic but reduced peak shifts compared with post-formation data, with slight peak broadening |
| Inactivity-map Dice coefficient at the 0.85 threshold | 0.83 |
| sXRD response | More severe heterogeneity than in both post-formation maps |
|---|---|
| Graphite (002) map | Large portion showed no lattice-parameter change on charging |
| Spatial correspondence | Graphite heterogeneity at 4.0 V was reflected in a similar NMC pattern at 4.3 V |
| Graphite (002) | Higher d-spacing than post-formation at equivalent voltages, with reduced intensity and increased broadening |
| NMC811 (003) | Increased asymmetry and broadening, reduced c-axis contraction, and higher d-spacing at 4.3 V than post-formation |
| Peak splitting | Small degree in some regions, but not widespread |
| Operando point diffraction | Pronounced broadening, dispersion, and hysteresis; graphite reflections less well resolved |
| Inactivity-map Dice coefficient at the 0.85 threshold | 0.52 |
| Mapped response | Homogeneous across most of the mapped region |
|---|---|
| Inactive region during charge | Roughly 15 % of the electrode surface |
| sXRD left-tab-region assignment | Attributed to a manufacturing or compression defect |
| sXRD anomalous-contrast assignment | Attributed to a beam or detector artefact, such as transient beam instability or non-planarity of the electrode surface |
| Operando point diffraction | Clear and reversible lattice evolution in NMC811 and graphite |
| sXRD maps | Spatially consistent and homogeneous, with uniform lithiation and little spatial variation in lattice parameters |
|---|---|
| Mapped voltages during charge | 2.5, 4.0, and 4.3 V |
| Operando point diffraction | Clear and reversible lattice evolution in NMC811 and graphite |
| Inactivity-map Dice coefficient at the 0.85 threshold | 0.85 |