Abstract

KALAISELVI, N. et al. LiMg_y1Cr_y2Mn_2-y1-y2O4 (0.0 £ y₁ £ 0.30; y₂ = 0.30 - y₁) as a Cathode Active Material for Lithium Batteries . Port. Electrochim. Acta [online]. 2005, vol.23, n.2, pp.247-262. ISSN 0872-1904.

LiMn₂O₄ is an attractive 4 V positive material in lithium rechargeable batteries owing to its favourable electrochemical characteristics besides its economic and environmental advantages. However, problems of limited cyclability, especially at elevated temperatures, have limited the utility and commercialization of this cathode material. Stabilization of the LiMn₂O₄ spinel structure has been sought to be realized by doping the spinel with suitable cations. In this paper, the results of an exploratory research on the capacity and cyclability of LiMn₂O₄ cathodes simultaneously doped with Cr³⁺ and Mg²⁺ are reported. LiMg_y1Cr_y2Mn_2-y1-y2O₄ spinels with y₁ = 0.00, 0.05, 0.10, 0.20, 0.25 and 0.30 and y₂ (0.3 - y₁) were synthesized by a solid-state fusion method. While Mg²⁺ bestows a positive effect on cyclability, it leads to a considerable reduction in capacity due to the oxidation of Mn³⁺ to the inactive Mn⁴⁺ as a result of charge compensation. Cr³⁺ on the other hand, leads only to half as much reduction in capacity while according added stability to the structure. Any expectation of a synergistic effect by Cr³⁺ and Mg²⁺ ions was belied by these findings.

Keywords : magnesium; chromium; LiMn₂O₄; cyclic voltammetry; impedance measurements; lithium battery cathode.

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