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This work is devoted to the study of fundamental properties of LiFePO4 (LFP) olivine in view of the optimization of this material for its use as a positive electrode material in Li-ion batteries. The investigation of the electronic and magnetic properties appears to be successful for the detection of a small amount of impurities. By the combination of X-ray diffraction, optical spectroscopy, and magnetometry, we characterize the local structure and the morphology of LFP particles. The impact of the ferromagnetic clusters (γ-Fe2O3 or Fe2P) on the electrochemical response is examined. The electrochemical performance of the optimized LFP powders investigated at 60 °C is excellent in terms of capacity retention (153 mAh/g at 2 C) as well as cycling life. No iron dissolution was observed after 200 charge–discharge cycles at 60 °C for cells containing Li foil, Li4Ti5O12, or graphite as negative electrodes. [ABSTRACT FROM AUTHOR]

We present the synthesis, characterization, and electrode behavior of LiNi0.5Mn1.5O4 spinels prepared by the wet-chemical method via citrate precursors. The phase evolution was studied as a function of nickel substitution and upon intercalation and deintercalation of Li ions. Characterization methods include X-ray diffraction, SEM, Raman, Fourier transform infrared, superconducting quantum interference device, and electron spin resonance. The crystal chemistry of LiNi0.5Mn1.5O4 appears to be strongly dependent on the growth conditions. Both normal-like cubic spinel [ Fd3m space group (SG)] and ordered spinel ( P4 1 32 SG) structures have been formed using different synthesis routes. Raman scattering and infrared features indicate that the vibrational mode frequencies and relative intensities of the bands are sensitive to the covalency of the (Ni, Mn)-O bonds. Scanning electron microscopy (SEM) micrographs show that the particle size of the LiNi0.5Mn1.5O4 powders ranges in the submicronic domain with a narrow grain-size distribution. The substitution of the 3d8 metal for Mn in LiNi0.5Mn1.5O4 oxides is beneficial for its charge–discharge cycling performance. For a cut-off voltage of 3.5–4.9 V, the electrochemical capacity of the Li//LiNi0.5Mn1.5O4 cell is ca. 133 mAh/g during the first discharge. Differences and similarities between LiMn2O4 and LiNi0.5Mn1.5O4 oxides are discussed. [ABSTRACT FROM AUTHOR]