In the fully discharged state (i.e. the as-received cell was first discharged to 2.65 V), the anode consisted mainly of the graphite phase. After applying a current (3.5 A corresponding to 1C), leading to a subsequent increase in voltage, the quantity of graphite rapidly decreased resulting in the formation of the lithiated graphite phase LiC30-30+ with its highest quantity at ~ 3.7 V. Following this, the LiC30-30+ gradually decreased to ~ 25 wt. % while the LiC12 gradually increased to ~ 55 wt. %. After reaching 4 V the quantity of LiC6 started to increase and reached 20 wt. % at 4.2 V. At 4.2 V the applied current was removed and the cell was allowed to relax for a time period of 10 min. An XRD-CT dataset was then collected and afterwards the cell was discharged to 2.65 V with 1 C rate (applying -3.5 A current). During the relaxation time and the XRD-CT scan (relaxation periods are not included in Figure ), the solid-state chemistry was slowly and gradually changing, resulting in a decrease of the LiC6 phase (from 20 wt. % to ~ 10 wt. %) and an increase of the LiC12 phase (from 55 wt. % to 70 wt. %) (i.e. during the relaxation the lithium is re-equilibrating between the partially reduced phases). During the discharge, the quantity of LiC12 gradually decreased and completely disappeared at ~ 3V. Simultaneously, the LiC30-30+ phase increased to 50 wt. % ~ 3.1 V and then decreased again to ~ 20 wt. % for the discharged cell. The graphite reappeared in the anode ~ 3.2 V and reached 80 wt. % for the discharged cell. The major difference between charge and discharge is based on the lithiation mechanism; the charge can be described as a continuous phase evolution in the range between graphite and LiC12 whereas the discharge occurs via a simultaneous growth of two phases LiC30-30+ and graphite with the latter one appearing below 3.3 V. The second cycle showed similar solid-state evolution regarding the amount of phases and the voltages at which the various phases appeared or disappeared; the main difference between the cycles was related to the graphite and LiC30-30+ weight fraction during cell charging. At the beginning of the second cycle, the cell did not recover 100 wt. % of the graphite phase and instead contained ~ 80 wt. % of graphite and ~ 20 wt. % of LiC30-30+. The second charging resulted in faster disappearance of the graphite which resulted in ca. 100 wt. % of LiC30-30+ at ~ 3.7 V (in the first cycle this quantity was ~ 90 wt. %). This behavior can be explained by the difference in the electrochemical protocol; the cell as received, before the in situ measurements, was discharged to 2.65 V with the potential held until the minimum current was reached. During the first cycle, the cell was discharged to 2.65 V (without keeping the voltage constant) and the relaxation period under open circuit voltage was applied before and during the acquisition of each XRD-CT dataset. ). At the charged state, the anode is composed primarily of LiC12, uniformly distributed in the electrode, as well as LiC6 and LiC30-30+ phases. The LiC6 was formed mainly at the anode surface (Figure ) while LiC30-30+ was found to be present in specific regions that can be identified as close to the Al tab and in the middle of the cell (Figure ). For the discharged state, the anode consisted of graphite, uniformly distributed in the cell, as well as the LiC30-30+ phases which appeared also in additional regions. These are present in the radial range between the Al tab and the steel casing; this "middle-region" is indicated by the arrows in Figure . When comparing the distribution of LiC30-30+ between the charged and discharged state, it can be seen that there are certain regions where the lithiation and delithiation of the anode is suppressed; these regions are in close proximity to the Al tab current collector and in the middle of the cell. The Al tab current collector and separator in the middle of the cell, where the cathode tape is removed, were previously shown to influence the lithium distribution in both the anode and cathode of AAA Li-ion commercial batteries . Our results indicate that a similar phenomenon can be observed in a cell of different size and battery cathode chemistry. It should be pointed out that no LiC18 was observed to form at the charged or discharged state. Figure presents the distribution of lattice parameters a and c of the NCA phase in the cell charged to 4.2 V and discharged to 2.65 V. Despite the NCA phase being uniformly distributed in the cathode (Figure ), differences in the distribution of lattice parameters could be identified in both the charged and discharged state. More precisely, in the region of the cathode which is directly connected to the Al tab (NCA ROI3 in Figure ), variations in the lattice parameters could be observed (Figure -S9, Table ); for the charged state the lattice parameter a was observed to be higher than the average lattice parameter a for the rest of the cathode and inversely for the lattice parameter c (i.e. lattice parameters c lower than the average lattice parameter c). The difference between the values of lattice parameters c (and a) can be used as an indication of the lithium distribution in the cathode; higher lattice parameter c suggests that the cathode phase contains less lithium in its structure . This comparison can be made by assuming that both materials belong to the same hexagonal cell and have the same chemical composition. Regarding the discharged state, heterogeneities in lattice parameters can be observed again for the cathode materials connected to the Al tab (NCA ROI3 in Figure ), but additionally in other areas (NCA ROI2 in Figure ). Interestingly, the regions shown by ROI2 in Figure are in close proximity to anode regions where the Li30-30+ phases were also observed for the discharged state. These observations suggest that for the discharge state, the cathode lithiation did not occur uniformly. The NCA ROI2 region contains the NCA structure with lower lattice parameter a and higher lattice parameter c, which suggests lower amounts of lithium in the cathode material. This is in agreement with the distribution of lithium in the anode, as these regions were seen to contain the LiC30-30+ phase instead of the fully de-lithiated graphite phase. In addition, the lattice parameters, and hence the amount of lithium, in the cathode material directly connected to the Al tab slightly changes between charged and discharged state. It should be noted that all the changes in the NCA lattice parameters (i.e. expansion vs contraction) are reversible and no difference between the various cycles were observed. After the initial two cycles, four additional cycles were performed following the same experimental protocol (Figure ). As expected, point XRD measurements and XRD line scans (Figure -S13) acquired during these four cycles did not indicate any deviations from the evolving solidstate chemistry reported above. In order to follow in situ the evolution of the LixC crystalline phases and changes in NCA lattice parameters in the battery cross section, six XRD-CT datasets were collected while charging the battery (the 7th cycle) to various potentials (3.7 V, 3.79 V, 3.85 V, 3.95 V and 4.2 V), allowing for 10 minutes of cell relaxation under OCV after reaching the set potential. The evolution of the crystalline phases present in the anode is shown in Figure (more information can be found in the Supporting Information Figure ). The spatial distribution of graphite and the two lithiated phases LiC30 and LiC30+ at the discharged cell (2.65 V) is in agreement with the previously reported results for the initial two cycles (Figure ). After charging the cell to 3.7 V, the graphite was seen to almost completely disappear while the amount of LiC30+ phase increased significantly, becoming uniformly distributed in the battery cross section. At 3.79 V, LiC30 became the predominant phase while LiC30+ decreased significantly but remained in the anode in the regions previously identified to exhibit heterogeneities in lithium concentration (Al tab -separator in the middle of the cell). The formation of LiC18 in the anode was observed at 3.85 V (from XRD point measurements it was not possible to differentiate between LiC18 and LiC12) and it was uniformly distributed in the anode electrode. In addition, a small amount of LiC12 started to form at the electrode surface, following the same behaviour seen for the LiC6 (Figure ). At 3.95 V, four different LixC phases were observed: LiC30+, LiC30, LiC18 and LiC12; from 3.95 V to 4.2 V the distribution of LiC30+ and LiC30 remained unchanged in the Al tab -separator region, while the LiC18 disappeared completely. At 3.95V, LiC12 became the predominant phase while a small amount of LiC6 formed at higher potentials above 3.95 V and primarily at the electrode surface. When comparing the distribution of the various LixC phases during the in situ charging, three regions can be clearly distinguished in the anode exhibiting distinct properties: (1) uniform/homogenous lithiation (HL), (2) delayed lithiation (DL) and (3) inactive-to-lithiation (IN) (Figure ). The region of uniform lithiation can be observed by the uniform distribution of LixC phases progressing in the following order: graphite → LiC30+ → LiC30 → LiC18→ LiC12 for the successive potentials during the in situ measurement. The region of delayed lithiation (DL) can be located in the previously discussed "middle-region", however it is not present at 4.2 V. The inactive region (IN) can be observed for the entire potential range (from 2.65 V to 4.2 V) and can be identified from the distribution of LiC30-30+ in the charged state at 3.95 V and above. The spatial distribution of lattice parameters a and c of the NCA phase during charging to 4.2 V is presented in Figure . As previously reported for the discharged cell (Figure ), three regions could be observed exhibiting different lattice parameters: (1) cathode directly connected to the Al tab (ROI3), (2) few layers in the cell (ROI2) and (3) the rest of the electrode layers (ROI1), the last one exhibiting higher lattice parameter a and lower lattice parameter c suggesting more lithium in its structure (diffraction patterns from these regions can be found in the Supporting Information Figure ). From 2.65 V to 3.7 V no significant changes in the lattice parameters a and c were observed. At 3.79 V and 3.85 V, the crystallographic properties of the NCA material from both the ROI1 and ROI2 regions started to change and consequently a decrease in lattice parameter a and increase in lattice parameter c was observed, which is typical for the layered materials during charging (i.e. while lithium is being removed from their structure). The values obtained for lattice parameters a and c became identical at 3.95 V for these two regions. This change is coincidental with the disappearance of the DL region from the anode, as discussed in the previous section, which is in close proximity to the ROI2 region. From 3.95 V, in the both ROI1 and ROI2 regions, the lattice parameter a continued to decrease (with a corresponding increase in lattice parameter c) while in the ROI3 region an increase in lattice parameter a and a decrease in lattice parameter c was observed. The in situ XRD-CT measurements performed while charging the battery to 4.2 V revealed heterogeneities in lithium distribution in both the cathode and the anode. As discussed in the previous section, there are three distinct regions in the cathode exhibiting different behaviour during de-lithiation. The ROI3 region is related to cathode material directly connected to the Al tab. In this region, the lattice parameters are experiencing only a minor change during the charging protocol. However it should be noted that the cathode material in this region is exhibiting the opposite behaviour to what is expected during charging of NCA. Specifically, an increase in lattice parameter a and decrease in lattice parameter c is observed as opposed to the typical behaviour which is decrease in lattice parameter a and increase in lattice parameter c. Heterogeneities related to the thickness of the cathode coating near the Al current collector have been previously suggested to lead to local variations in charge-and discharge current densities which can be associated with battery degradation . The rest of the cathode material (ROI1 and ROI2) exhibits typical changes in the lattice parameters of hexagonal structure suggesting that the close proximity of the aluminum tab directly affects the lithium distribution in the cathode material. It is important to note that no other phases (hexagonal or monoclinic) were observed during the experiment.