Carbon paper is commonly used to fabricate electrodes for batteries, and its morphology is crucial to the internal mass transport. In this work, geometric models of carbon paper are obtained by experimental and numerical reconstruction methods. The micromorphology of the carbon paper is obtained with a scanning electron microscope and an X-ray computed tomography scanner, and the binary slicing method is used in the experimental reconstruction method. Three different methods are used for numerical reconstruction, namely the layered 2D fibre, 3D fibre stacking and layered 3D fibre stacking methods. The structure and characteristic parameters of the carbon paper, such as pore size distribution, dimensionless specific surface area, effective diffusion coefficient and anisotropic coefficient, are statistically analysed for comparison. The dimensionless effective diffusion coefficients of Li+ in different directions in the electrolyte-filled carbon paper are obtained using lattice Boltzmann method. Results show that the internal structural features directly affect mass transport. The curves of the calculated effective diffusivity versus porosity are well fitted using a power function similar to Bruggeman equation within the porosity range of 0.66–0.86. The anisotropic coefficient is obtained from the effective diffusion coefficient in different directions.

中文翻译：

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用格子玻尔兹曼方法重构复写纸及结构特征参数分析

复写纸通常用于制造电池电极，其形态对内部质量传输至关重要。在这项工作中，复写纸的几何模型是通过实验和数值重建方法获得的。复写纸的微观形貌是用扫描电子显微镜和X射线计算机断层扫描仪获得的，实验重建方法采用二元切片法。三种不同的方法用于数值重建，即分层 2D 纤维、3D 纤维堆叠和分层 3D 纤维堆叠方法。对碳纸的孔径分布、无量纲比表面积、有效扩散系数和各向异性系数等结构和特征参数进行统计分析，进行比较。使用格子Boltzmann方法获得了Li+在填充电解质的碳纸中不同方向的无量纲有效扩散系数。结果表明，内部结构特征直接影响质量传输。计算的有效扩散率与孔隙率的曲线在孔隙率 0.66-0.86 范围内使用类似于布鲁格曼方程的幂函数拟合得很好。各向异性系数由不同方向的有效扩散系数得到。计算的有效扩散率与孔隙率的曲线在孔隙率 0.66-0.86 范围内使用类似于布鲁格曼方程的幂函数拟合得很好。各向异性系数由不同方向的有效扩散系数得到。计算的有效扩散率与孔隙率的曲线在孔隙率 0.66-0.86 范围内使用类似于布鲁格曼方程的幂函数拟合得很好。各向异性系数由不同方向的有效扩散系数得到。