Facile Synthesis of The Li-Rich Layered Oxide Li_(1.23)Ni_(0.09)Co_(0.12)Mn_(0.56)O2 with Superior Lithium Storage Performance and New Insights into Structural Transformation of the Layered Oxide Material during Charge-Discharge Cycle: In Situ XRD Characterization

摘要

In this work, the Li-rich oxide Li_(1.23)Ni_(0.09)Co_(0.12)Mn_(0.56)O2 was synthesized through a facile route called aqueous solution-evaporation route that is simple and without waste water. The as-prepared Li_(1.23)Ni_(0.09)Co_(0.12)Mn_(0.56)O2 oxide was confirmed to be a layered LiMO2—Li2MnO3 solid solution through ex situ X-ray diffraction (ex situ XRD) and transmission electron microscopy (TEM). Electrochemical results showed that the Li-rich oxide Li_(1.23)Ni_(0.09)Co_(0.12)Mn_(0.56)O2 material can deliver a discharge capacity of 250.8 mAhg~(-1) in the 1st cycle at 0.1 C and capacity retention of 86.0% in 81 cycles. In situ X-ray diffraction technique (in situ XRD) and ex situ TEM. were applied to study structural changes of the Li-rich oxide Li_(1.23)Ni_(0.09)Co_(0.12)Mn_(0.56)O2 material during charge—discharge cycles. The study allowed observing experimentally, for the first time, the existence of β-MnO2 phase that is appeared near 4.54 V in the first charge process, and a phase transformation of the β-MnO2 to layered Li_(0.9)MnO2 is occurred in the initial discharge process by evidence of in situ XRD pattrens and selected area electron diffraction (SAED) patterns at different states of the initial charge and discharge process. The results illustrated also that the variation of the in situ X-ray reflections during charge—discharge cycling are clearly related to the changes of lattice parameters of the as-prepared Li-rich oxide during the charge—discharge cycles.