Structural and electrochemical properties of the doped spinels Li1.05M0.02Mn1.98O3.98N0.02 (M = Ga3+, Al3+, or Co3+; N = S2- or F-) for use as cathode material in lithium batteries

The doped and milled spinels Li1.05M0.02Mn1.98O3.98N0.02 (M = Ga3+, Al3+ or Co3+; N = S2- or F-) are studied aiming at obtaining an improved charge/discharge cycling performance. These spinels are prepared by a solid-state reaction among the precursors epsilon-MnO2, LiOH, and the respective oxide/salt of the doping ions at 750 degrees C for 72 h and milled for 30 min. The obtained spinels are characterized by XRD, SEM, and determinations of the average manganese valence n. In the charge and discharge tests, the doped spinels present outstanding initial values of the specific discharge capacity C(117-126 mA h g(-1)), decreasing in the following order: C(Li1.05Al0.02Mn1.98S3.02O3.98) > C(Li1.05Al0.02Mn1.98F3.02O3.98) > C(Li1.05Ga0.02Mn1.98 S3.02O3.98) > C(Li1.05Ga0.02Mn1.98F3.02O3.98) > C(Li1.05Co0.02Mn1.98S3.02O3.98) > C(Li1.05Co0.02Mn1.98F3.02O3.98). The doped spinel Li1.05Ga0.02Mn1.98S3.02O3.98 presents an excellent electrochemical performance, with a low capacity loss even after 300 charge and discharge cycles (from 120 to 115 mA hg(-1) or 4%). (C) 2009 Elsevier B.V. All rights reserved.