Insight into poly(1,3-dioxolane)-based polymer electrolytes and their interfaces with lithium Metal: Effect of electrolyte compositions

The transport properties and electrochemical stability of advanced lithiummetal batteries are severely constrained by the actual electrolyte compositions. Herein, for comprehensive atomistic insights and the development of electrolyte scientific theory, molecular dynamics technology is employed to investigate the electrochemical properties of recently attractive poly(1,3-dioxolane)-based electrolytes and their interfaces with lithium metal. This work elaborates on the characteristics of Li+ solvation environments and the effects of polymer chain length or plasticizer content on the experiment-concerned properties of bulk electrolytes, including solvation sheath structures, ionic diffusions, conductivities, transport numbers, etc. Meanwhile, to clarify the influence of polymer or salt concentration on the electrolyte/lithium metal interface, three distinctive interface models were proposed and analyzed based on different electrolyte compositions in this work: liquid-based, polymer-based, and highly-concentrated systems. Compared with the unfavorable liquid interface layer in the liquid-based system, the latter two systems have more electrochemically stable interfacial construction due to the appearance of polymer on the lithium metal surface. Besides, the Li+ solvation structure, which is related to the lithium electrodeposition, exhibits orientation, e.g., small organic liquid molecules in the liquid-based system are more likely to appear on the side that is accessible to the lithium metal surface. These small molecules are essentially excluded from the Li+ solvation structures in the polymer-based electrolyte, which is another important factor for stabilizing the interface. Furthermore, compared with the bulk electrolytes, it is found that ionic conductions at the interfaces are not attenuated in all systems. This work presents a comprehensive, profound view from bulk to interfacial properties, thus providing a theoretical cornerstone for the composition design and performance optimization of polymer electrolytes for lithium metal batteries.