Synergetic effect of high Ni ratio and low oxygen defect interface zone of single crystals on the capacity retention of lithium rich layered oxides

Origin and characterization of the oxygen loss phenomenon in the layered oxide cathodes of Li-ion batteries

Li-ion batteries have been widely applied in the field of energy storage due to their high energy density and environment friendliness. Owing to their high capacity of ∼200 mA h g-1 and high cutoff voltage of ∼4.6 V vs. Li+/Li, layered lithium transition metal oxides (LLMOs) stand out among the numerous cathode materials. However, the oxygen loss of LLMO cathodes during cycling hampers the further development LLMO cathode-based Li-ion batteries by inducing a dramatic decay of electrochemical performance and safety issues. In this regard, the oxygen loss phenomenon of LLMO cathodes has attracted attention, and extensive efforts have been devoted to investigating the origins of oxygen loss in LLMO cathodes by various characterization methods. In this review, a comprehensive overview of the main causes of oxygen loss is presented, including the state of charge, side reactions with electrolytes, and the thermal instability of LLMO cathodes. The characterization methods used in the scope are introduced and summarized based on their functional principles. It is hoped that the review can inspire a deeper consideration of the utilization of characterization techniques in detecting the oxygen loss of LLMO cathodes, paving a new pathway for developing advanced LLMO cathodes with better cycling stability and practical capabilities.

NAi/Li Antisite Defects in the Li1.2Ni0.2Mn0.6O2 Li-Rich Layered Oxide: A DFT Study

Li-rich layered oxide (LRLO) materials are promising positive-electrode materials for Li-ion batteries. Antisite defects, especially nickel and lithium ions, occur spontaneously in many LRLOs, but their impact on the functional properties in batteries is controversial. Here, we illustrate the analysis of the formation of Li/Ni antisite defects in the layered lattice of the Co-free LRLO Li1.2Mn0.6Ni0.2O2 compound through a combination of density functional theory calculations performed on fully disordered supercells and a thermodynamic model. Our goal was to evaluate the concentration of antisite defects in the trigonal lattice as a function of temperature and shed light on the native disorder in LRLO and how synthesis protocols can promote the antisite defect formation.