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Layered oxide, LiNi0.5Mn0.3Co0.2O2 (NMC532), is commonly used in the commercial high energy Li-ion batteries. However, such layered oxide cathode always faces the dilemma between high capacity and stable cycling. Upper charge cutoff voltage is one of the important factors that strongly influences both capacity and cycle life, unfortunately, exhibiting an opposite effect. A choice of an appropriate upper charge cutoff voltage is expected to achieve the balance between these two performance metrics. Therefore, it is of great significance to comprehensively understand the effect of incremental upper voltages, ranging from normally used cutoff voltage to slight overcharge voltage, on the cycling behaviors of the NMC532 cathode material. In this work, the systematic studies about the effect of the upper voltage on the NMC532 cathode material are investigated. Physical characterizations, i.e., ex situ synchrotron X-ray diffraction and X-ray absorption spectroscopy, provide information on the degradation of NMC532 material. Post-mortem analysis via combined scanning electron microscopy and electrochemical impedance spectroscopy reveals the degradation of the cathode-electrolyte-interface at high voltages. This comprehensive study shows the fundamental interplay among many electrochemically relevant factors, especially at different charge cutoff voltages [ABSTRACT FROM AUTHOR]

When lithium-ion batteries age with cycling, the loss of lithium inventory and active material may result in battery aging. The aging characteristics and mechanism of batteries under different cycle conditions differ. Therefore, battery cycle life tests were performed to explore the aging characteristics and mechanism of Li[Ni0.5Co0.2Mn0.3]O2 batteries. The results of the one-way analysis of variance show that the temperature has a slight effect on battery aging in the range of 25 °C-55 °C, but the discharge current has a great impact on battery aging in the range of 0.5C-2C. Battery aging mechanism can be analyzed by reconstructing charging voltage curves. But the hypothesis of the nondestructive method had not been verified through experiments. The hypothesis was verified through half-cell experiment, and the nondestructive diagnostic method was used to analyze the aging mechanisms of Li[Ni0.5Co0.2Mn0.3]O2 battery. The aging mechanism analysis results revealed that the main aging mechanism will change under different cycle conditions, therefore, the aging mechanism identification is necessary before establishing the battery life prediction model. [ABSTRACT FROM AUTHOR]