FIGURE 1 TG/DSC curves of the precursors
XRD of the samples at 650 oC, 800 oC and 900 oC (Figure 2A-C) reveals the structure evolution from P3 to P2 during the temperature increase and that the mass loss on TGA might come with structure reconstruction. For instance, the P3-type layered structure is observed in the sample at 650oC, while the second phase P2 is seen in the samples above 800 oC. The formation of P3 phase is at a lower temperature than previously studied P3-phase cathodes that calcined at 700/750 oC 25–27. The P3 structure obtains Cm space group (PDF#00-054-0839). On the other hand, the P2-type layered structure with P63/mmc space group (PDF#01-070-3726) is gained in the sample NMC-900. The presence of P2 phase at a high temperature of 900 oC coincided with previous studies because the phase is more stable at high temperatures than P3 phase 23,28,29.