Department of Chemistry, Institute of Inorganic and Applied Chemistry, University of Hamburg, Martin-Luther-King Platz 6, D-20146 Hamburg, Germany.
Phys Chem Chem Phys. 2019 Feb 6;21(6):3122-3133. doi: 10.1039/c8cp06443a.
The electric double layer formation of supercapacitors is governed by ion electrosorption at the electrode surface. Large surface areas are beneficial for the energy storage process, typically achieved by carbon electrode materials. It is a matter of debate whether pores provide the same contribution to the capacitance regardless of the size, or if subnanometer pores lead to an anomalous increase of capacitance. In our work, we developed a new model for normalized capacitance depending on pore sizes, using a combination of a sandwich type capacitor for micropores and double-cylinder capacitor model for larger pores. Modification factors for each capacitance value were calculated using the nonlinear generalized reduced gradient method to obtain a modified electric sandwich double-cylinder capacitor (ESDCC) model. The model was validated by comparing the measured capacitance values of a set of prepared activated carbons in organic electrolytes with simulated values according to the modified ESDCC model, using combined physisorption data of carbon dioxide and nitrogen. We concluded a non-constant capacitive contribution, with pores having the size of bare cations contributing to the capacitance to a larger extent and mesopores with the size of three solvated ions providing an unusual low contribution to the overall capacitance.
超级电容器的双电层形成受电极表面离子电吸附的控制。大的比表面积有利于储能过程，通常通过碳电极材料实现。争论的焦点是无论孔的大小如何，孔是否同样对电容有贡献，还是亚纳米孔导致电容异常增加。在我们的工作中，我们开发了一种新的归一化电容模型，该模型取决于孔径大小，使用夹层电容器（用于微孔）和双圆柱电容器模型（用于较大的孔）的组合。使用非线性广义简约梯度法计算每个电容值的修正因子，以获得修正后的电夹层双圆柱电容器（ESDCC）模型。通过使用二氧化碳和氮气的物理吸附数据的组合，将根据修正后的 ESDCC 模型模拟的一组在有机电解质中制备的活性炭的测量电容值与模拟值进行比较，对该模型进行了验证。我们得出的结论是非恒定的电容贡献，具有裸阳离子大小的孔对电容的贡献更大，而具有三个溶剂化离子大小的介孔对总电容的贡献异常低。
