Influences of Li-ion Coordination Structure on Compatibility Between Diglyme-based Electrolytes and Graphite Anode

With excellent rate performance, the reaction of Li-ether co- intercalation into graphite has received much research interest. However, the compatibility between diglyme-based electrolyte and graphite is unsatisfactory. To understand the mechanism of the side reaction, the electrochemical behaviors of two model electrolytes, diglyme- LiTFSI ( lithium trifluoromethanesulfonimide) and diglyme-LiBr, were investigated. Raman spectroscopy was used to quantitively study the solvation structure of the Li+, and X-ray photoelectron spectroscopy ( XPS) was used to analyze the interface between the graphite anode and electrolyte. The results showed that the origin of the irreversible capacity was the reductive decomposition of diglyme in the voltage range of 0. 2- 0. 6 V vs Li/ Li+. The side reaction was suppressed when the solvation number of the Li+ was low. Regulating the coordination structure of Li+ was the key to improving the compatibility between the graphite anode and diglyme-based electrolyte.