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高性能鋰離子電池負極材料一氧化錳/石墨烯復合材料的合成

Synthesis of MnO/reduced graphene oxide composites as high performance anode materials for Li-ion batteries

  • 摘要: 通過凍干-煅燒合成了一氧化錳/石墨烯(MnO/rGO)復合材料,并將其用作鋰離子電池負極材料.在500 mA·g-1的電流密度下,MnO/rGO復合材料表現出高達830 mAh·g-1的可逆容量,且在充放電循環160圈后,其可逆容量依然高達805 mAh·g-1.倍率測試結果顯示,循環225圈后,在2.0 A·g-1的電流密度下,其可逆容量高達412 mAh·g-1.復合材料中的石墨烯在提高材料導電性的同時有效地緩解了一氧化錳充放電過程中的體積膨脹.通過對比容量-電壓的微分分析,發現復合材料超出一氧化錳理論容量的部分是由形成了更高價態的錳引起的.MnO/rGO復合材料比純一氧化錳(p-MnO)更容易出現高價態的錳,可能是因為rGO上殘留的氧為電極反應提供了額外所需的氧源.該一氧化錳/石墨烯復合材料因其簡單綠色的合成過程及優異的電化學性質,有望在未來的鋰電負極中得到廣泛的實際應用.

     

    Abstract: MnO/reduced graphene oxide (MnO/rGO) composites synthesized through freeze-drying following annealing were used as anode materials for lithium ion batteries. At 500 mA·g-1, the MnO/rGO composite exhibits a reversible capacity as high as 830 mAh·g-1 and the specific capacitance remains at 805 mAh·g-1 after 160 discharge/charge cycles, demonstrating excellent cycling stability. It also shows good rate capacities and delivers a specific capacity of 412 mAh·g-1 at 2. 0 A·g-1 after 225 cycles at different rates. The rGO increases the electrical conductivity and provides space to accommodate the volume expansion of MnO during charge/discharge. The extra capacity, over the theoretical value of MnO, is attributed to the formation of higher oxidation state manganese according to the charge-voltage derivative analysis of the galvanostatic charge-discharge curves. A higher tendency to further oxidize Mn(Ⅱ) in the MnO/rGO composite maybe result in the extra oxygen source provided by rGO during the electrode reaction. The simple and green synthetic protocol and the excellent electrochemical performance demonstrate the great potential of the MnO/rGO composite anode in large scale production and applications.

     

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