Fig. shows the XRD spectra of the three BM samples (BM1, BM2, and BM3) from 2θ of 15° to 60°, whereas Fig. shows an enhanced plot from 2θ of 40° to 43.8°. The diffraction peaks for BM1, BM2, and BM3 in Fig. are matched with the ICDD PDF-4+ database (summarized in Table ), and it is determined that Li[NixMnyCoz]O2 (shown as ◆) and graphite (shown as ★) are the two main crystalline species along with the insignificant presence of Al2O3 20 (from current collector and shown as ■). Fig. shows that graphite in all three BM samples appears with an intense characteristic peak at ~26.5°. This characteristic peak may belong to either 2H (hexagonal phase) with an hkl of (002), 3R (rhombohedral phase) with an hkl of (003) or a convolution of both depending upon the crystal structure of graphite. Graphite consists of a layered crystal structure with two major types of stacking sequences: ABAB stacking (2H phase) and ABCABC stacking (3R phase). The characteristic peaks of the 2H and 3R phases (~26.5°) completely overlap, however, previous work has shown that the 2θ range between 40° and 48° can be used to differentiate and quantify the 2H and 3R phases. A qualitative analysis of Fig. shows that BM1 may contain a relatively larger proportion of the 3R phase due to the higher (101)3R peak intensity compared to the other two BM samples. It is reported that the electrochemical properties of graphite are affected by the weight ratio of 2H and 3R phases, making it valuable to quantify this ratio. Furthermore, mechanical pre-treatment of BM (such as ball milling and attrition milling) and high-temperature heat treatment of graphite recycled from BM can change the ratio of 2H and 3R under certain conditions by converting one phase to the other one. Fig. shows that the peaks at 2θ of 18.6°, 36.7°, 37.8°, 38.4°, 44.4°, 48.6°, and 58.6° belong to (003), ( ), ( ), ( ), ( ), ( ) and ( ) hkl of Li[NixMnyCoz]O₂. Table shows that ICDD entries belonging to different NMC chemistries have equivalent structural parameters, thus identification of the exact NMC chemistry using qualitative analysis of XRD spectra is not readily achievable due to the overlapping of the peaks concerned. However, these findings when combined with the results from the metal composition data of each BM sample (Table ) point to the fact that BM1, BM2, and BM3 samples have NMC622, NMC111, and NMC901 chemistries, respectively. Thus, XRD analysis (Fig. ) coupled with metal composition data can be used to examine the properties of the bulk materials i.e., metallic impurities, crystalline phases, (NMC and graphite), and phase composition. into highly water-soluble compounds (Li₂CO₃ and Li₂O). XRD spectra of pyrolyzed BM (Fig. ) were also matched with the ICDD PDF-4+ database, and the identified crystalline phases include graphite, Li[NixMnyCoz]O₂, metal oxides (NiO, MnO), metallic phases (Ni, Mn, Co), Li2CO3, Li2O, LiF, and Al2O3 (corresponding PDF entries are summarized in Table ). The intense graphite peak at ~26.5° in XRD spectra of pyrolyzed BM indicates that the majority of graphite remains intact after pyrolysis (Fig. ), however, pyrolyzed BM3 exhibits a relatively higher fraction of the 3R graphite phase compared, as evidenced by the prominent (101)3R peak at ~43.5 (Fig. ), compared to that of untreated BM (Fig. ). The majority of Li[NixMnyCoz]O₂ phase has been reduced indicated by relatively small peaks at ~18.6° and 36.7°. It is important to note that overlapping diffraction peaks of different metal oxides (e.g., MnO, NiO) can hinder their clear distinction through just qualitative analysis. For pyrolyzed BM1 and BM2, the peak at ~59.3° suggests the presence of NiO or MnO. Whereas, for pyrolyzed BM3, the intense peaks at ~44.5° and ~51.9°, attributable to metallic Ni, suggest that NiO was completely reduced to Ni in this sample. Further insights into the pyrolysis pre-treatment of NMC BM can be acquired by analyzing the gases evolved from the reduction reactions as well as from the decomposition of organic species (electrolytes, PVDF, surface coatings). Fig. presents the XRD patterns of pyrolyzed BM1, pyrolyzed BM2, and pyrolyzed BM3. It has been reported that during pyrolysis, graphite acts as a reducing agent, converting the transition metals in Li[NixMnyCoz]O₂ partially or fully to their respective oxides (e.g., NiO, MnO) and metallic phases (e.g., Ni, Mn, Co). Simultaneously, Li in Li[NixMnyCoz]O₂ is transformed into highly water-soluble compounds (Li₂CO₃ and Li₂O). XRD spectra of pyrolyzed BM (Fig. ) were also matched with the ICDD PDF-4+ database, and the identified crystalline phases include graphite, Li[NixMnyCoz]O₂, metal oxides (NiO, MnO), metallic phases (Ni, Mn, Co), Li2CO3, Li2O, LiF, and Al2O3 (corresponding PDF entries are summarized in Table ). The intense graphite peak at ~26.5° in XRD spectra of pyrolyzed BM indicates that the majority of graphite remains intact after pyrolysis (Fig. ), however, pyrolyzed BM3 exhibits a relatively higher fraction of the 3R graphite phase compared, as evidenced by the prominent (101)3R peak at ~43.5 (Fig. ), compared to that of untreated BM (Fig. ). The majority of Li[NixMnyCoz]O₂ phase has been reduced indicated by relatively small peaks at ~18.6° and 36.7°. It is important to note that overlapping diffraction peaks of different metal oxides (e.g., MnO, NiO) can hinder their clear distinction through just qualitative analysis. For pyrolyzed BM1 and BM2, the peak at ~59.3° suggests the presence of NiO or MnO. Whereas, for pyrolyzed BM3, the intense peaks at ~44.5° and ~51.9°, attributable to metallic Ni, suggest that NiO was completely reduced to Ni in this sample. Further insights into the pyrolysis pre-treatment of NMC BM can be acquired by analyzing the gases evolved from the reduction reactions as well as from the decomposition of organic species (electrolytes, PVDF, surface coatings).