Temperature-Driven Chemical Segregation in Co-Free Li-Rich-Layered Oxides and Its Influence on Electrochemical Performance

Abstract

Co-free Li-rich layered oxides are gaining interest as feasible positive electrode materials in lithium-ion batteries (LIBs) in terms of energy density, cost reduction, and alleviating safety concerns. Unfortunately, their commercialization is hindered by severe structural degradation that occurs during electrochemical operation. The study at hand demonstrates advanced structural engineering of a Li-rich Co-free oxide with composition Li1.1Ni0.35Mn0.55O2 by spray pyrolysis and subsequent calcination of an aqueous precursor, creating a segregated structure of two distinct layered phases with space groups R3̅m (rhombohedral) and C2/m (monoclinic). This particular structure was investigated with powder neutron diffraction, high-resolution analytical transmission electron microscopy imaging, and electron energy loss spectroscopic characterization. This complex structure contributes to the high electrochemical stability and good rate capability observed for this compound (160 mAh/g at C/3 and 100 mAh/g at 1C). These results provide new insights into the feasibility of developing and commercializing cobalt-free positive electrode materials for LIBs.