Impact of Synthesis Chelation on the Crystallography and Capacity of Li-Rich LiNiMnFeO Cathode Particles.

The quest for removal of cobalt from battery materials has intensified in the face of intensifying demand for batteries. Cobalt-free lithium-rich LiNiMnFeO (LNMFO) is synthesized under variation of chelating agent ratio and pH using the sol-gel method. Systematic search of the chelation and pH space found that the extractable capacity of the synthesized LNMFO is most clearly correlated to the ratio of chelating agent to transition metal oxide; a ratio of transition metal to citric acid of 2:1 achieves greater capacity at the expense of relative capacity retention. Charge-discharge cycling, d/d analysis, XRD, and Raman at different charging potentials are used to quantify the different degrees of activation of the LiMnO phase in the LNMFO powders synthesized under different chelation ratios. SEM and HRTEM analysis are employed to understand the effect of particle size and crystallography on the activation of LiMnO phase in the composite particles. An unprecedented use of the marching cube algorithm to evaluate atomic scale tortuosity of crystallographic planes in HRTEM revealed that subtle undulations in the planes in addition to stacking faults correlate to the extracted capacity and stability of the various LNMFO synthesized.