New Insight on the Role of Electrolyte Additives in Rechargeable Lithium Ion Batteries

Abstract

Solid electrolyte interphase (SEI)-forming agents such as vinylene carbonate, sulfone, and cyclic sulfate are commonly believed to be film-forming additives in lithium-ion batteries that help to enhance graphite anode stability. However, we find that the film-forming effect and the resultant SEI may not be the only reasons for the enhanced graphite stability. This is because the as-formed SEI cannot inhibit Li -solvent co-intercalation once the additive is removed from the electrolyte. Instead, we show that the Li solvation structure, which is modified by these additives, plays a critical role in achieving reversible Li (de)intercalation within graphite. This discovery is confirmed in both carbonate and ether-based electrolytes. We show that the problem of graphite exfoliation caused by Li -solvent co-intercalation can be mitigated by adding ethene sulfate to tune the Li coordination structure. This work brings new insight into the role of additives in electrolytes, expanding the prevailing thinking over the past 2 decades. In addition, this finding can guide the design of more versatile electrolytes for advanced rechargeable metal-ion batteries. + + + + +