在传统电池和超级电容器中，寻求改善的能量密度有时会采取特别有趣的路径。在由空军科学研究办公室支持的研究中，UCLA的一个团队与其他机构（密西西比州立大学，内华达大学，中央南大学）合作，并着眼于树叶的结构。
叶子和电极都有一个共同的目标:Maximize their surface area-to-mass ratio to better attract and retain source material. In the case of plants, the leaves seek to capture carbon dioxide needed for photosynthesis; for the supercap, it’s grabbing ions in the electrolyte solution that retain energy until needed later.
研究人员坚持认为，与标准超级胶囊相比，给定质量的电容量增加了30％，同时提供了10倍的功率。他们同样重要的是，他们说，这些细胞在10,000电荷/放电周期后保留了95％的电容，这是许多“改进”设计不足的区域。
The ideas, process, and results are detailed in their very lengthy paper “用于超级电容器的Brand-Branchlet叶子叶子纳米结构“ 出版于自然，以及其他广泛的Supplementary Information。Their “recreation” of nature’s branch-and-leaves approach is based on a pair of carbon-atom nanostructures. For branches, they used arrays of hollow cylinders of carbon nanotubes (CNTs) with a 20- to 30-nm diameter. In contrast, the leaves are sharp-edged and built of graphene petals (GPs)—ultra-thin sheets of carbon up to 100 nm wide that are arranged on the nanotube stems（图。1）。
1. The branch-and-leaves design is made up of arrays of hollow, cylindrical carbon nanotubes (the “branches”) and sharp-edged petal-like structures (the “leaves”) made of graphene. (Source: UCLA)
最后，他们将这些结构制成隧道形阵列。传输存储能量的离子可以在电解质和表面之间以“电阻”少得多的“电阻”流过这些阵列。所得结构使设计能够提供更多的能量，并以更高的效率进行功能（图2）。
2. CNT/GP微型配件的结构表征，显示了碳布上叶子上的CNT/GP微型管的示意图，碳布（CC）基板用于高性能超级电容器电极（请注意黄色阴影区域在示意图中表示要放大的选定区域）（a）；低放大倍数（C）在碳纤维上的CNT微丝线的均匀覆盖范围；以及从纳米管出现的花瓣（H）的高分辨率TEM图像。（来源：UCLA）
发现
结果表明，面积的电容为2.35 f/cm2大约500 f/gm（基于活性材料质量）。他们推测，杂交结构中的尖锐石墨烯 - 彼得边缘可能会增加电荷存储，并减轻电解质离子对电极的快速访问。
The team noted that there are problems generally associated with CNT-based array electrodes, including poor nanotube bonding to substrates, low tube-to-tube charge-transfer efficiency, and easy destruction of the tube orientation. These weaknesses have resulted in poor mechanical robustness, high internal resistance, and poor cyclic stability. However, they maintain that their approach largely overcomes these well-known problems.
此外，他们指出：“据我们首次，设计了带有空心通道的微型管道，以将无障碍电极表面积增加到电解质，并促进电荷/放电期间的快速扩散，”当然，这是一个令人印象深刻的主张。他们补充说，石墨烯花瓣大大提高了碳 - 纳米管微芯的机械鲁棒性，有助于在操作过程中保留结构取向。
3.显示的是高电流电荷/放电曲线在高电流密度为40至100 mA/cm（A）的高电荷/放电曲线，以及在电流电荷/放电曲线（b）中计算得出的电流密度的方向电容和电容保留。（来源：UCLA）
The researchers presented extensive results across multiple parameters and perspectives. Among these results were graphs showing the charge/discharge curves as well as the areal capacitances and capacitance retention as a function current-related factors（图3）。
The electrode also performs well in acidic conditions and high temperatures, both environments in which supercapacitors could be used if their performance was stable.
