Ultrathin MnO2 nanofibers grown on graphitic carbon spheres as high-performance asymmetric supercapacitor electrodes
Ultrathin MnO2 nanofibers grown on graphitic carbon spheres as high-performance asymmetric supercapacitor electrodes
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DOI：
10.1039/c1jm13872c
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发表时间：
2012-01-01
影响因子：
--
通讯作者：
Zhao, X. S.
中科院分区：
文献类型：
--
作者：
Lei, Zhibin;Zhang, Jintao;Zhao, X. S.
为了提高二氧化锰的电化学活性表面积，在KMnO 4水溶液中，采用石墨空心碳球（GHCS）为载体，在石墨空心碳球（GHCS）上生长二氧化锰纳米纤维。GHCS与MnO_4 ~-发生化学计量比的氧化还原反应，生成了MnO_2含量可控的GHCS-MnO_2复合材料。结果发现，这些MnO 2纳米纤维垂直生长在GHCS的外表面上，产生复合电极，显示出良好的电子传输，快速的离子渗透，快速和可逆的法拉第反应，以及优异的倍率性能时，用作超级电容器电极材料。以GHCS-MnO 2为正极、GHCS为负极的非对称超级电容器电池在1.0 mol L-1的Na 2SO 4水溶液电解液中以2.0 V的电池电压可逆充放电，能量密度为22.1 Wh kg（-1），功率密度为7.0 kW kg（-1）。该非对称超级电容器具有优异的电化学循环稳定性，使用恒电流充放电技术测量1000次连续循环后，其初始电容为99%，库仑效率为90%。
Growing MnO2 nanofibers on graphitic hollow carbon spheres (GHCS) is conducted by refluxing GHCS in a KMnO4 aqueous solution aimed to enhance the electrochemically active surface area of MnO2. The stoichiometric redox reaction between GHCS and MnO4- yields GHCS-MnO2 composites with controllable MnO2 content. It is found that these ultrathin MnO2 nanofibers are vertically grown on the external surface of the GHCS, yielding a composite electrode showing good electron transport, rapid ion penetration, fast and reversible Faradic reaction, and excellent rate performance when used as supercapacitor electrode materials. An asymmetric supercapacitor cell with GHCS-MnO2 as the positive electrode and GHCS as the negative electrode can be reversibly charged/discharged at a cell voltage of 2.0 V in a 1.0 mol L-1 Na2SO4 aqueous electrolyte, delivering an energy density of 22.1 Wh kg(-1) and a power density of 7.0 kW kg(-1). The asymmetric supercapacitor exhibits an excellent electrochemical cycling stability with 99% initial capacitance and 90% coulombic efficiency remained after 1000 continuous cycles measured using the galvanostatic charge-discharge technique.