Theoretical Analysis of Carrier Ion Diffusion in Superconcentrated Electrolyte Solutions for Sodium-Ion Batteries

Superconcentrated electrolyte solutions are receiving increasing attention as a novel class of liquid electrolyte for secondary batteries because of their unusual and favorable characteristics, which arise from a unique solution structure with a very small number of free solvent molecules. The present theoretical study investigates the concentration dependence of the structural and dynamical properties of these electrolyte solutions for Na-ion batteries using large-scale quantum molecular dynamics simulations. Microscopic analysis of the dynamical properties of Na+ ions reveals that ligand (solvent/anion) exchange reactions, an alternative diffusion pathway for Na+ ions, are responsible for carrier ion diffusion in the superconcentrated conditions.

超浓电解质溶液作为一类新型二次电池液态电解液正受到日益广泛的关注，其独特且优异的特性源于仅含极少量自由溶剂分子的特殊溶液结构。本理论研究采用大规模量子分子动力学模拟，探究了钠离子电池用此类电解质溶液的结构与动力学特性的浓度依赖性。对钠离子动力学特性的微观分析表明，配体（溶剂/阴离子）交换反应作为钠离子的一条替代扩散路径，是超浓条件下载流子离子扩散的主导机制。