Controlling Ion Coordination Structure and Diffusion Kinetics for Optimized Electrode-Electrolyte Interphases and High-Performance Si Anodes
Haiping Jia, Peiyuan Gao, Lianfeng Zou, Kee Sung Han, Mark Engelhard, Yang He, Xin Zhang, Wengao Zhao, Ran Yi, Hui Wang, Chongmin Wang, Xiaolin Li, Ji‐Guang Zhang
Abstract
The cycling performance of batteries is largely determined by the electrode-electrolyte interphase associated with the chemical and electrochemical properties of electrolyte salts and solvents. In this work, the correlations between the electrode (cathode/anode)-electrolyte interphase, ion coordination structure, and diffusion kinetics were analyzed systematically using localized high-concentration electrolytes (LHCEs) as a model system. The fundamental mechanism behind the enhanced cycling stability of silicon (Si)-based lithium (Li)-ion batteries using optimized LHCEs is investigated. Among all the LHCEs tested, 1.8 M lithium bis(fluorosulfonyl)imide with carbonate solvents and fluorinated diluents (1:2 molar ratio) had the highest proportion of solvent-separated ion pairs and contact ion pairs and the fastest ion diffusion. This LHCE formed the most stable electrode-electrolyte interphase and hence had the best Si anode performance. These results reveal the fundamental mechanism behind the stability of LHCEs and provide guidance on the new electrolyte design for Si anodes and other battery systems.