Study on Crystal Growth Kinetics and Preferred Orientation for LiF Crystal in Dimethyl Sulfoxide/1,3-Dioxolane-based Electrolyte

Abstract

The Li/CFx primary battery with the highest energy density has been widely applied in many fields. However, the Li/CFx battery has been suffering from some problems for large-scale applications, such as low energy density, which needs to be overcome urgently. Among the technical solutions, the modification of the discharge product layer is an effective approach to solve the problem. To adjust the pore structure of the discharge product layer, it is necessary to explore both the growth and the orientation kinetics of LiF crystals as the main discharge product of Li/CFx batteries. In this work, the growth kinetics of the LiF crystal during discharge in dimethyl sulfoxide/1,3-dioxolane (DMSO/1,3-DO)-based electrolytes is first explored by kinetic models of crystal growth. The calculated results show that the nucleation and nuclei growth mechanism is best suited for the growth kinetics of the LiF crystal in the DMSO/1,3-DO (5:5 v/v)-based electrolyte, which is different from the 2D diffusion mechanism of the LiF crystal in the PC/DME (5:5 v/v). Then, the orientation kinetics of LiF crystals is investigated by using quantum-chemical calculations. The simulation results reveal that the total chemical adsorption energies of both DMSO and 1,3-DO solvent molecules on the crystal planes of LiF could change with the ratio variation of DMSO/1,3-DO. The preferred crystal orientation growth of the LiF grain during discharge mainly depends on the total chemical adsorption energy on each crystal plane of LiF, which is caused by the selective adsorption of both DMSO and 1,3-DO on different crystal planes. The study of the growth kinetics of LiF grains and the preferred orientation growth can help our understanding of the structure control mechanism of discharge products of LiF. In general, this work may pave the way for the future development of a novel electrolyte of the large-capacity Li/CFx battery with high power density.