In situ X-ray diffraction studies of mixed LiMn2O4–LiNi1/3Co1/3Mn1/3O2 composite cathode in Li-ion cells during charge–discharge cycling

Abstract

Abstract The structural changes of the composite cathode made by mixing spinel LiMn 2 O 4 and layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 in 1:1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ∼5.2 V vs. Li/Li + , the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the LiNi 1/3 Co 1/3 Mn 1/3 O 2 component only. When the cell voltage reaches at ∼4.0 V vs. Li/Li + , lithium extraction from the spinel LiMn 2 O 4 component starts and becomes the major contributor for the cell capacity due to the higher rate capability of LiMn 2 O 4 . When the voltage passed 4.3 V, the major structural changes are from the LiNi 1/3 Co 1/3 Mn 1/3 O 2 component, while the LiMn 2 O 4 component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel LiMn 2 O 4 component, with much less changes in the layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research.