Layered LiMO2 (M = Ni, Co, and Mn) is a type of promising cathode materials for high energy density and high work voltage lithium-ion batteries. However, the poor rate performance and low power density hinder its further applications. The capacity fade is related to the structural transformation in the layered LiMO2. In this work, the structural changes of bi-material cathode composed of mesoporous graphene and layered LiNi1/3Co1/3Mn1/3O2 (NCM) were studied via in situ X-ray diffraction (XRD). During different C-rate charge–discharge test at the voltage range of 2.5–4.1 V, the composite cathode of NCM−graphene (NCM−G) reveals better rate performances than pure NCM cathode. The NCM−G composite electrode displays a higher rate capability of 76.7 mAh·g−1 at 5C rate, compared to the pure NCM cathode of 69.8 mAh·g−1 discharge capacity. The in situ XRD results indicate that a reversible phase transition from hexagonal H1 to hexagonal H2 occurs in layered NCM material during 1C charge–discharge process. With the current increasing to 2C/5C, the structure of layered NCM material for both electrodes reveals few changes during charge and discharge processes, which indicates the less utilization of NCM component at high C-rates. Hence, the improved rate performance for bi-material electrode is attributed to the highly conductive mesoporous graphene and the synergistic effect of mesoporous graphene and NCM material.

中文翻译：

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锂离子电池介孔石墨烯/LiNi1/3Co1/3Mn1/3O2复合正极的结构演变

层状 LiMO2（M = Ni、Co 和 Mn）是一种很有前途的高能量密度和高工作电压锂离子电池正极材料。然而，较差的倍率性能和低功率密度阻碍了其进一步应用。容量衰减与层状 LiMO2 的结构转变有关。在这项工作中，通过原位 X 射线衍射 (XRD) 研究了由介孔石墨烯和层状 LiNi1/3Co1/3Mn1/3O2 (NCM) 组成的双材料阴极的结构变化。在 2.5-4.1 V 电压范围内的不同 C 倍率充放电测试中，NCM-石墨烯（NCM-G）复合正极显示出比纯 NCM 正极更好的倍率性能。与 69.8 mAh·g-1 放电容量的纯 NCM 正极相比，NCM-G 复合电极在 5C 倍率下显示出更高的倍率容量 76.7 mAh·g-1。原位 XRD 结果表明，在 1C 充放电过程中，层状 NCM 材料发生了从六方 H1 到六方 H2 的可逆相变。随着电流增加到 2C/5C，两个电极的层状 NCM 材料的结构在充电和放电过程中几乎没有变化，这表明 NCM 组件在高 C 倍率下的利用率较低。因此，双材料电极倍率性能的提高归因于高导电介孔石墨烯以及介孔石墨烯和 NCM 材料的协同效应。两个电极的层状 NCM 材料的结构在充电和放电过程中几乎没有变化，这表明 NCM 组件在高 C 倍率下的利用率较低。因此，双材料电极倍率性能的提高归因于高导电介孔石墨烯以及介孔石墨烯和 NCM 材料的协同效应。两个电极的层状 NCM 材料的结构在充电和放电过程中几乎没有变化，这表明 NCM 组件在高 C 倍率下的利用率较低。因此，双材料电极倍率性能的提高归因于高导电介孔石墨烯以及介孔石墨烯和 NCM 材料的协同效应。