Insertion/removal kinetics of lithium ion in spinel LiCuxMn2−xO4
(School of Chemistry and Environment, South China Normal University,Guangzhou 510006, China )
Abstract: The insertion/removal processes of lithium ion in spinel lithium manganese oxide(LiMn2O4) and copper doped spinel lithium manganese oxide (LiCuxMn2−xO4) on a powder microelectrode were studied by electrochemical impedance spectroscopy(EIS), cyclic voltammetry(CV) and X-ray diffractometry(XRD). The insertion/removal process of lithium ion in the spinel oxides consists of three steps: charge transfer of lithium ion on the surface of the spinel oxides, diffusion and occupation of lithium ion in the lattice of the spinel oxide. Similar to chromium, the doping of copper in spinel lithium manganese oxide results in the increase of the charge transfer resistance and the double layer capacitance for lithium insertion or removal, and the decrease of the diffusion coefficient of lithium ion in the lattice of spinel oxide. However, the insertion capacitance, a parameter reflecting the occupation of lithium ion in the lattice of the spinel oxide, is hardly influenced by the doping of copper. The influence of the doped copper on the kinetic process of lithium insertion/removal in spinel lithium manganese oxide is related to the contraction of spinel lattice.
Key words: insertion and removal kinetics; spinel lithium manganese dioxide; doping; copper