Many promising supercapacitor electrode materials have high resistivity and require conductive additives to function effectively. However, the detailed role of the additive is not understood. Here, this question is resolved by applying a quantitative model for resistance‐limited supercapacitor electrodes to Co(OH)₂‐nanosheet/carbon nanotube composites. Without nanotubes, theory predicts and experiments show that while the low‐rate capacitance increases linearly with electrode thickness, the high rate capacitance decreases with thickness due to slow charging. Experiments supported by theory show that nanotube addition has two effects. First, the nanotube network effectively distributes charge, increasing the intrinsic electrode performance to the limit associated with its accessible surface area. Second, at high‐rate, the increased electrode conductivity shifts the rate‐limiting resistance from electrode to electrolyte, thus removing the thickness‐dependent capacitance falloff. Furthermore, the analysis quantifies the out‐of‐plane conductivity of the nanotube network, identifies the cross‐over from resistance‐limited to diffusion‐limited behavior, and allows full electrode modeling, facilitating rational design.

中文翻译：

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量化纳米管在纳米：纳米复合超级电容器电极中的作用

许多有前途的超级电容器电极材料具有高电阻率，并且需要导电添加剂才能有效发挥作用。但是，该添加剂的详细作用尚不清楚。在这里，通过将电阻受限的超级电容器电极的定量模型应用于Co（OH）₂来解决此问题纳米片/碳纳米管复合材料。理论预测和实验表明，如果没有纳米管，则低速电容随电极厚度线性增加，而高速电容则由于缓慢充电而随厚度减小。理论支持的实验表明，添加纳米管有两个作用。首先，纳米管网络有效地分配了电荷，从而将本征电极性能提高到与其可及表面积相关的极限。其次，在高速率下，增加的电极电导率将限速电阻从电极转移到电解质上，从而消除了取决于厚度的电容衰减。此外，该分析量化了纳米管网络的平面外电导率，确定了从电阻限制行为到扩散限制行为的交叉，