High-temperature Ionic Transport and Electrochemical Characteristics of Porous CoS2 Electrodes in Ternary Molten Salt Electrolytes

Systematic researches of ionic transport and electrochemical characteristics have been seldom implemented for the porous CoS2 electrode in ternary LiCl-LiBr-KBr, which are ideal and main form for advanced thermal batteries. In the work, we systematically measured the combined electrochemical and transport kinetic parameters of CoS2/LiCl-LiBr-KBr system at the varied high temperature. Specifically, we firstly explored the discharge mechanism of CoS2/molten LiCl-LiBr-KBr using galvanostatic discharge experiment and X-ray diffraction (XRD). For the ionic transport performance, the diffusion coefficient of active Li ions was calculated from cyclic voltammograms (CV) data, and the ionic conductivity of LiCl-LiBr-KBr and electric conductivity of CoS2 and generated Co9S8 were also measured. Then, the interfacial electrochemical characteristics (exchange current density and transfer coefficients) were comparatively studied by the electrochemical impedance spectroscopy (EIS) and linear sweep voltammograms (LSV) method. Based on the above-mentioned results, we further investigated the comprehensive effects of these factors on the electrochemical and transport behavior by proposing a equivalent-circuit model of the porous CoS2 electrode soaked in LiCl-LiBr-KBr molten salts. The results of this research is basis for the design and optimization of the new thermal battery cell, and will contribute to a knowledge-based development of the advanced TBs in the future.