Charge–discharge properties of LiCoO2 electrodes modified by olivine-type compounds of LiMgPO4 for lithium secondary batteries

Fine particles of Olivine-type LiMgPO4 were prepared directly from a mixture of Li2O, MgO, and P2O5 as starting materials using a mechanical milling technique at room temperature. LiMgPO4 fine particles were investigated as surface modification materials of LiCoO2 cathodes in lithium cells. Electrolytes of these cells were 1 mol dm−3 LiPF6-ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (3:7 volume ratio). LiMgPO4-modified LiCoO2 cathodes exhibited better charge–discharge performance for high charge cut-off potential of 4.5 V (vs. Li/Li+) in lithium cells than that of LiCoO2 cathode. Olivine-type LiMgPO4 may inhibit oxidative decomposition of the electrolytes on LiCoO2 particle surface without a crystal structure change of LiCoO2 for high charge cut-off potentials.

► Olivine-type LiMgPO4-modified LiCoO2 cathodes exhibited a good cycle performance. ► LiMgPO4 may inhibit oxidative decomposition of electrolytes on LiCoO2 electrode. ► LiMgPO4 fine particle is expected to work as a new buffer layer on LiCoO2.