The Effect of Nanolayer AlF₃ Coating on LiMn₂O₄ Cycle Life
in High Temperature for Lithium Secondary Batteries¹

Haowen Liu^z and Dingguo Tang

Hubei Province Key Laboratory of Catalysis and Materials Science, College Of Chemistry and Materials Science,
S. Cent. Univ. Nationalities, Wuhan 430074, P. R. China

Received March 18, 2008

Abstract—The surface of the spinel LiMn₂O₄ was coated with AlF₃ by a chemical process to improve its elec-
trochemical performance at high temperatures. The morphology and structure of the original and AlF₃-coated
LiMn₂O₄ samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM).
All the samples exhibited a pure cubic spinel structure without any impurities in the XRD patterns. It was found
that the surfaces of the original LiMn₂O₄ samples were covered with a nanolayer AlF₃ after the treatment. The
charge/discharge of the materials were carried at 220 mA/g in the range of 3.0 and 4.4 V at 55. While the
original LiMn₂O₄ showed 17.8% capacity loss in 50 cycles at 55, the AlF₃-coated LiMn₂O₄ (118.1 mA h/g)
showed only 3.4% loss of the initial capacity (122.3 mA h/g) at 55. It is obvious that the improvement in
cycling performance of the coated-LiMn₂O₄ electrode at 55 is attributed to the presence of AlF₃ on the sur-
face of LiMn₂O₄.

Key words: lithium ion battery, AlF₃, coatings, electrical properties

DOI: 10.1134/S1023193509070088

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