Multifunctional MnO2-Carbon Nanoarchitectures Exhibit Battery and Capacitor Characteristics in Alkaline Electrolytes
Multifunctional MnO2-Carbon Nanoarchitectures Exhibit Battery and Capacitor Characteristics in Alkaline Electrolytes
复制标题
DOI：
10.1021/jp9070696
复制
发表时间：
2009-10-15
影响因子：
3.7
通讯作者：
Greenbaum, Steve G.
中科院分区：
文献类型：
--
作者：
Long, Jeffrey W.;Sassin, Megan B.;Greenbaum, Steve G.
我们证明，当锰氧化物以纳米尺度的涂层分布在碳纳米泡沫衬底的壁上时，它在含有LiOH的碱性电解液中表现出伏安特征，这是电化学电容器或电池的特征，取决于所研究的电位范围。在正电势范围内观察到了假电容，非原位X射线吸收光谱证实了当Mn的氧化态在3.72-3.43之间切换时，自然的层状水钠铝石MnOx结构保持不变。当循环范围扩展到更负的电势极限时，观察到明确的还原和氧化特征，相关的可逆变化在25次循环后的锰氧化态为0.71。在这些深度放电条件下，纳米MnOx涂层的水钠锰矿和伽马-MnOOH形式的可逆相互转化促进了高电荷存储容量。用固体Li-7核磁共振研究了来自碱性电解液的Li+在提高MnOx-碳纳米泡沫循环稳定性中的作用。
We demonstrate that, when distributed as nanoscale coatings on the walls of carbon nanofoam substrates, manganese oxides exhibit voltammetric signatures in LiOH-containing alkaline electrolytes that are characteristic of either electrochemical capacitors or batteries, depending on the potential range investigated. Pseudocapacitance is observed for positive potential ranges, and ex-situ X-ray absorption spectroscopy confirms that the native layered birnessite MnOx structure is retained as the Mn oxidation state is toggled between 3.72 and 3.43. When the cycling range is extended to more negative potential limits, well-defined reduction and oxidation features are observed, with an associated reversible change in the Mn oxidation state of 0.71 after 25 cycles. For these deep-discharge conditions, high charge-storage capacities are facilitated by the reversible interconversion of birnessite and gamma-MnOOH forms of the nanoscale MnOx coating. Solid-state Li-7 NMR is used to investigate the role of Li+ from the alkaline electrolyte in enhancing the cycling stability of the MnOx-carbon nanofoam.