Reconstruction of Carbon Papers and Analysis of Structural and Characteristic Parameters Through Lattice Boltzmann Metho
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Reconstruction of Carbon Papers and Analysis of Structural and Characteristic Parameters Through Lattice Boltzmann Method Yanan Gao1 · Zhi Wen1 · Xie Deng1 · Mingze Shi1 · Xunliang Liu1 Received: 24 July 2020 / Accepted: 10 November 2020 © Springer Nature B.V. 2020
Abstract 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. Keywords Lattice Boltzmann method · Lithium air battery · Carbon paper reconstruction · Mass transport List of Symbols C Concentration of Li+ (mol m3) C0 Initial concentration of Li+ (mol m3) Cin Concentration of Li+ inlet (mol m3) Cout Concentration of Li+ outlet (mol m3) D0 Diffusion coefficient of Li+ (m2 s−1) i+ in the porous medium ( m2 s−1) Deff Effective diffusion coefficient of L f Anisotropic coefficient * Xunliang Liu [email protected] 1
School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China
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i+ diffusion gi Equilibrium distribution function of L + i diffusion gi Distribution function of L eq
Greek Letters α Bruggeman index ε Porosity of carbon paper τ Dimensionless relaxation factor 𝜔i Weight coefficient in i directions Subscripts and Superscripts A Layered two-dimensional fibre method B Three-dimensional fibre stacking method C Layered three-dimensional fibre stacking method EXP Experimental reconstruction method tp Through plane direction ip In-plane direction
1 Introduction Lithium–air batteries (LABs) have the highest theoretical energy density in electrochemical energy storage systems (Andersen et al. 2015). The development of research on reaction mechanism and electrolyte and electrode structures of LABs has emphasised its great potential
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