Fe-doping effects on the structural and electrochemical properties of 0.5Li2MnO3·0.5LiMn0.5Ni0.5O2 electrode material

• Published in: Journal of applied electrochemistry 2012-06, Vol.42 (6), p.409-417
• Main Authors: Lian, F., Gao, M., Qiu, W. H., Axmann, P., Wohlfahrt-Mehrens, M.
• Format: Article
• Language: English
• Subjects: Charge; Chemistry; Chemistry and Materials Science; Coprecipitation; Electrochemical impedance spectroscopy; Electrochemistry; Electrode materials; Field emission; Industrial Chemistry/Chemical Engineering; Iron; Nickel; Original Paper; Physical Chemistry; X-rays
• ISSN: 0021-891X; 1572-8838
• DOI: 10.1007/s10800-012-0414-4

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 m and Fm 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.