Structural and electrochemical properties of Li(Fe, Co)xMn2 – xO4 solid solution as 5 V positive electrode materials for Li secondary batteries

Solid solutions, Li(Fe, Co)xMn2 − xO4 (0 ≤ x ≤ 0.5 for Fe, 0 ≤ x ≤ 1.0 for Co) were synthesized by solid state reaction at 1023–1073 K in O2 atmosphere. The compositional dependence of lattice parameters and cation distribution was studied by neutron diffraction Rietveld refinement. It was revealed that Fe and Co partially occupied tetrahedral 8a sites and the 1∶3 and 1∶1 ordering did not occur on Fe (Co) and Mn ions in octahedral 16d sites. X-Ray absorption fine structure (XAFS) analysis showed the variation of valences and metal–oxygen interatomic distances of Mn, Fe, and Co. The Fe–O distance was longer whereas the Co–O distance was shorter compared to the averaged M16d–O32e distance calculated from the lattice parameters. Charge and discharge properties were studied in voltage range 3.0–5.3 V vs. Li/Li+.