Ethylene Carbonate-Free Propylene Carbonate-Based Electrolytes with Excellent Electrochemical Compatibility for Li-Ion Batteries through Engineering Electrolyte Solvation Structure

Propylene carbonate (PC) -based electrolytes have many desirable advantageous properties compared to the currently used ethylene carbonate (EC) -based electrolytes for lithium ion batteries, however, their poor compatibility with the graphite anode hinders its applications. Here, a facile and effective strategy to make electrochemically compatible PC-based electrolytes by use of a weakly coordinating diethyl carbonate co-solvent to induce PF6- anions into the solvation shell of Li+ to form an anion-induced ion-solvent-coordinated (AI-ISC) structure is reported. Such an AI-ISC structure can lead to an increase of the lowest unoccupied molecular orbital energy level of the electrolyte, therefore considerably improving the reduction tolerance of the PC solvent. Furthermore, by using the film-forming additive (fluoroethylene carbonate, FEC), an electrochemically stable, EC-free PC-based electrolyte, which enables reversible Li+ intercalation on the graphite electrode is obtained. The graphite/LiNi0.5Mn0.3Co0.2O2 pouch cells using this PC-based electrolyte exhibit very similar room-temperature electrochemical performance to those using conventional EC-based electrolytes and excellent low-temperature performance. This work provides a new approach to make EC-free electrolytes with a similar AI-ISC structure but without the need for a high concentration of Li salt of highly concentrated electrolytes, which may bring new insights in the development of advanced electrolyte systems for wide battery applications.

Automated summary

This study introduces a simple and effective strategy to prepare electrochemically compatible PC-based electrolytes, utilizing a weakly coordinating diethyl carbonate co-solvent to enhance the reduction tolerance of PC solvent. By incorporating a film-forming additive, an electrochemically stable PC-based electrolyte that allows reversible Li+ intercalation on the graphite electrode is obtained.