Synthesis and Characterization of Magnesium and Manganese Doped LiCoO2
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LiCo1-2xMgxMnxO2 (0 ≤ x ≤ 0.05) positive electrode materials were prepared from Co1-2xMgxMnx(OH)2 (0 ≤ x ≤ 0.05) co-precipitated precursor materials by mixing precursor materials with Li2CO3 and heating. All precursor and lithiated materials were characterized by Scanning Electron Microscopy, X-ray Diffraction (XRD), Inductively Coupled Plasma – Optical Emissions Spectroscopy, in situ XRD, and electrochemical testing. Increasing Mg/Mn content in the material was found to slightly increase the 1st charge capacity, decrease the 1st discharge capacity, and increase the 1st cycle irreversible capacity when cycling up to 4.7 V, likely due to oxygen loss at high voltage. Cells with even 1% Mg/Mn doping were shown to have markedly improved cycling performance, but cells with higher Mg/Mn content did not further improve cycling performance. Results suggest that the cycling improvements stem from suppressing the cell resistance growth and not from the suppression of the O3-O6-O1 phase transitions at high voltage.