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Enhanced performance of LiFePO 4 originating from the synergistic effect of graphene modification and carbon coating
Journal of Alloys and Compounds ( IF 5.8 ) Pub Date : 2018-10-01 , DOI: 10.1016/j.jallcom.2018.07.078
Guodong Jiang , Zhihai Hu , Jian Xiong , Xing Zhu , Songdong Yuan

Abstract LiFePO4@Carbon/reduced graphene oxide (LFP@C/rGO) composites as cathode materials for lithium-ion batteries were prepared by a simple solvothermal method followed with a carbon coating. The characterizations indicated that LiFePO4 particles with pure orthorhombic olivine phase were attached to graphene oxide, which could be reduced in the synthesis of LiFePO4 and constructed a conductive network in the composite. After a post carbon encapsulation, a uniform and thin carbon layer on LiFePO4 was formed and could quickly collect electrons via a shorter pathway around LiFePO4 nanoparticles during the charge/discharge. The results showed LFP@C/rGO composites delivered a discharge specific capacity of 148.3 mAh/g at the rate of 1 C, higher than LiFePO4 only modified with graphene or coated with carbon layers. The discharge capacity of 129 mAh/g can still be maintained when the current density increased to 20 C. Furthermore, LFP@C/rGO manifested a satisfactory lifespan and no capacity fading was observed after 200 cycles at the rate of 10 C. Compared with synthesized LiFePO4@C, LFP@C/rGO composites also exhibited a high capacity of 108 mAh/g at −20 °C at a rate of 1 C. Even after 500 charge/discharge cycles, capacity fading was scarcely seen. Electrochemical tests suggested the unique architecture resulted in a synergistic effect between 3D reduced graphene oxide (rGO) conductive network and carbon coating, which remarkably improved the conductivity of electrode and electrochemical kinetics, contributing to outstanding rate performance and cycle life.

中文翻译:

源自石墨烯改性和碳涂层的协同效应的 LiFePO 4 性能增强

摘要 LiFePO4@Carbon/还原氧化石墨烯(LFP@C/rGO)复合材料作为锂离子电池正极材料,通过简单的溶剂热法和碳涂层制备。表征表明,具有纯斜方晶橄榄石相的 LiFePO4 颗粒附着在氧化石墨烯上,可以在 LiFePO4 的合成中被还原并在复合材料中构建导电网络。在碳封装后,在 LiFePO4 上形成了均匀且薄的碳层,并且可以在充电/放电过程中通过 LiFePO4 纳米颗粒周围的较短路径快速收集电子。结果表明,LFP@C/rGO 复合材料在 1 C 倍率下的放电比容量为 148.3 mAh/g,高于仅用石墨烯改性或涂有碳层的 LiFePO4。当电流密度增加到 20 C 时,仍然可以保持 129 mAh/g 的放电容量。此外,LFP@C/rGO 表现出令人满意的寿命,并且在 10 C 倍率下循环 200 次后没有观察到容量衰减。合成的 LiFePO4@C、LFP@C/rGO 复合材料在 -20 °C 和 1 C 的速率下也表现出 108 mAh/g 的高容量。即使在 500 次充电/放电循环后,也几乎没有看到容量衰减。电化学测试表明,这种独特的结构在 3D 还原氧化石墨烯 (rGO) 导电网络和碳涂层之间产生了协同效应,显着提高了电极的电导率和电化学动力学,有助于实现出色的倍率性能和循环寿命。LFP@C/rGO 表现出令人满意的寿命,并且在 10 C 倍率下循环 200 次后没有观察到容量衰减。与合成的 LiFePO4@C 相比,LFP@C/rGO 复合材料在 - 下也表现出 108 mAh/g 的高容量20 °C,1 C 的速率。即使在 500 次充电/放电循环后,也几乎没有看到容量衰减。电化学测试表明,这种独特的结构在 3D 还原氧化石墨烯 (rGO) 导电网络和碳涂层之间产生了协同效应,显着提高了电极的电导率和电化学动力学,有助于实现出色的倍率性能和循环寿命。LFP@C/rGO 表现出令人满意的寿命,并且在 10 C 倍率下循环 200 次后没有观察到容量衰减。与合成的 LiFePO4@C 相比,LFP@C/rGO 复合材料在 - 下也表现出 108 mAh/g 的高容量20 °C,1 C 的速率。即使在 500 次充电/放电循环后,也几乎没有看到容量衰减。电化学测试表明,这种独特的结构在 3D 还原氧化石墨烯 (rGO) 导电网络和碳涂层之间产生了协同效应,显着提高了电极的电导率和电化学动力学,有助于实现出色的倍率性能和循环寿命。LFP@C/rGO 复合材料在 -20 °C 和 1 C 的速率下也表现出 108 mAh/g 的高容量。即使在 500 次充电/放电循环后,也几乎没有看到容量衰减。电化学测试表明,这种独特的结构在 3D 还原氧化石墨烯 (rGO) 导电网络和碳涂层之间产生了协同效应,显着提高了电极的电导率和电化学动力学,有助于实现出色的倍率性能和循环寿命。LFP@C/rGO 复合材料在 -20 °C 和 1 C 的速率下也表现出 108 mAh/g 的高容量。即使在 500 次充电/放电循环后,也几乎没有看到容量衰减。电化学测试表明,这种独特的结构在 3D 还原氧化石墨烯 (rGO) 导电网络和碳涂层之间产生了协同效应,显着提高了电极的电导率和电化学动力学,有助于实现出色的倍率性能和循环寿命。
更新日期:2018-10-01
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