Charge-discharge characteristics and phase transitions of mixed LiNi0.8Co0.2O2 and LiMn2O4 cathode materials for lithium-ion batteries

The charge-discharge characteristics of the composite cathode made of the m ixture of LiNi0.8Co0.2O2 and LiMn2O4 was studied in a battery cell using a lithium foil as an anode. Three plateaus were observed at 3.85 V, 4.0 V and 4.2 V during charge. The operating voltage of the composite cathode is hig her than the single-component cathode LiNi0.8Co0.2O2. Compared to the other single-component LiMn2O4 cathode, a smaller capacity fading was obtained f or the composite cathode. The synchrotron based In situ x-ray diffraction ( XRD) was used to study the phase transitions of the composite cathode durin g charge-discharge. In the composite cathode, the phase transitions of each component during charge-discharge can be clearly identified. These phase t ransitions are basically the same as observed in single-component cathode: the phase transitions from hexagonal I(HI) to hexagonal II (H2), and then t o hexagonal III (H3) were observed for the component of LiNi0.8Co0.2O2, and the phase transitions from cubic I(C1) to cubic II (C2), and then to cubic III (C3) were observed for the component of LiMn2O4. However; some interes ting new kinetic effects, which ave differentiation the single-component ca thode, were observed.