Solvent Molecular Design to Regulate the Intercalation Behavior in Ether Electrolyte for Stable Graphite Anodes in Potassium-Ion Batteries

It has been widely recognized that ether electrolytes show great advantages in building robust solid-electrolyte interphases (SEIs) for stable anode performance. However, its extension to the graphite electrode is hampered by the ether solvent cointercalation, leading to a lower capacity and higher potential than those in ester counterparts having neat cation insertion. Herein, the ether solvent molecules by optimizing the O/C atomic ratio through tailoring the end group and chain length are screened. Such a modification alters the solvation strength between K ions and the solvent, which dictates the intercalation behavior in graphite. In particular, an ethylene glycol diethyl ether-derived electrolyte is developed, which prevents the solvent cointercalation and induces the formation of binary intercalation compound KC8. Meanwhile, the novel ether electrolyte helps build a uniform and robust SEI, significantly boosting the rate capability and long-term stability of graphite anode. This work resolves the dilemma of ether electrolyte in realizing the stable and high-capacity graphite anode for facilitating its application in potassium-ion batteries.

Automated summary

Ether electrolytes have shown advantages in building stable solid-electrolyte interphases (SEIs), but their application to graphite electrodes is hindered by solvent cointercalation. This study develops a novel ether electrolyte that prevents solvent cointercalation and improves the stability and rate capability of graphite anodes. By optimizing the structure of ether solvent molecules, the intercalation behavior in graphite can be controlled.