高性能锂离子电池负极材料一氧化锰/石墨烯复合材料的合成

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

  • 摘要: 通过冻干-煅烧合成了一氧化锰/石墨烯(MnO/rGO)复合材料,并将其用作锂离子电池负极材料.在500 mA·g-1的电流密度下,MnO/rGO复合材料表现出高达830 mAh·g-1的可逆容量,且在充放电循环160圈后,其可逆容量依然高达805 mAh·g-1.倍率测试结果显示,循环225圈后,在2.0 A·g-1的电流密度下,其可逆容量高达412 mAh·g-1.复合材料中的石墨烯在提高材料导电性的同时有效地缓解了一氧化锰充放电过程中的体积膨胀.通过对比容量-电压的微分分析,发现复合材料超出一氧化锰理论容量的部分是由形成了更高价态的锰引起的.MnO/rGO复合材料比纯一氧化锰(p-MnO)更容易出现高价态的锰,可能是因为rGO上残留的氧为电极反应提供了额外所需的氧源.该一氧化锰/石墨烯复合材料因其简单绿色的合成过程及优异的电化学性质,有望在未来的锂电负极中得到广泛的实际应用.

     

    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.

     

/

返回文章
返回