Transport Performance of Molten Salt Electrolyte in a Fractal Porous FeS₂ Electrode: Mesoscale Modeling and Experimental Characterization

The fractal morphology of a porous electrode dramatically affects transport performance and electrochemical reactive properties of batteries. In this study, we reconstruct three-dimensional (3D) mesoscale geometrical models of an FeS2 cathode in thermal-activated batteries (TBs) by X-ray microcomputed tomography (micro-CT) technology and image-reconstructing methods. Then, on the basis of the mesoscale geometries and the intrinsic transport coefficients of the electrolyte ions, we explore the coupled transport performance of molten salt electrolytes in porous FeS2 electrodes at mesoscale by the numerical simulating method. Specifically, the dependence of the Li ions spatial concentration distribution and transport flux on the interfacial electrochemical reaction conditions, pore sizes, and tortuosity factors of porous electrodes will be systematically studied. Furthermore, the fitted effective diffusive coefficient (Deff) of the Li ions in a porous FeS2 electrode from the mesoscale model is compared with that measured by cyclic voltammogram (CV) data and calculated by the Bruggeman method, and the result confirms that the fitted Deff is closer to the actual value.