Engineering the solid electrolyte interphase (SEI) that forms on the electrode is crucial for achieving high performance in metal-ion batteries. However, the mechanism of SEI formation resulting from electrolyte decomposition is not fully understood at the molecular scale. Herein, a new strategy of switching electrolyte to tune SEI properties is presented, by which a unique and thinner SEI can be pre-formed on the graphite electrode first in an ether-based electrolyte, and then the as-designed graphite electrode can demonstrate extremely high-rate capabilities in a carbonate-based electrolyte, enabling the design of fast-charging and wide-temperature lithium-ion batteries (e.g., graphite | LiNi0.6Co0.2Mn0.2O2 (NCM622)). A molecular interfacial model involving the conformations and electrochemical stabilities of the Li+-solvent-anion complex is presented to elucidate the differences in SEI formation between ether-based and carbonate-based electrolytes, then interpreting the reason for the obtained higher rate performances. This innovative concept combines the advantages of different electrolytes into one battery system. It is believed that the switching strategy and understanding of the SEI formation mechanism opens a new avenue to design SEI, which is universal for pursuing more versatile battery systems with greater stability.
Bibliographical noteKAUST Repository Item: Exported on 2022-09-14
Acknowledgements: J.M. greatly acknowledges the support from the National Natural Science Foundation of China (22122904). This work was also supported by the National Natural Science Foundation of China (21978281, 22109155). The authors also thank the Independent Research Project of the State Key Laboratory of Rare Earth Resources Utilization (110005R086), Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. The computational work was done on the KAUST supercomputer.