Fe-doping effects on the structural and electrochemical properties of 0.5Li 2 MnO 3 ·0.5LiMn 0.5 Ni 0.5 O 2 electrode material

With the aim of achieving a high-performance 0.5Li 2 MnO 3 ·0.5LiMn 0.5 Ni 0.5 O 2 material, a series of 0.5Li 2 MnO 3 ·0.5LiMn x Ni y Fe (1− x − y ) O 2 (0.3 ≤ x ≤ 0.5, 0.4 ≤ y ≤ 0.5) samples with low Fe content was synthesized via coprecipitation of carbonates. Its crystal structure and electrochemical performance were characterized by means of powder X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, galvanostatic charge/discharge testing, cyclic voltammetry, and electrochemical impedance spectra. Rietveld refinements with a model integrating R 3 m and Fm 3 m indicate that a low concentration of Fe incorporated in 0.5Li 2 MnO 3 ·0.5LiMn 0.5 Ni 0.5 O 2 decrease a disordered cubic domain of the composite structure. The preferential distribution of Fe in cubic rock-salt contributes to an unimaginable decrease of c -axis parameter of the predominant layered structure as the Fe content increases. Moreover, including Fe as a dopant can kinetically improve crystallization and also change the ratio of Mn 3+ /Mn 4+ and Ni 3+ /Ni 2+ . As a result, 0.5Li 2 MnO 3 ·0.5LiMn 0.4 Ni 0.5 Fe 0.1 O 2 exhibits lower Warburg impedance and higher reversible capacity than the undoped material.