Analysis of Main Factors Limiting the Improvement of Electrochemical Performances of Low‐Concentration Electrolyte

Abstract

The low‐concentration electrolyte possesses the benefits of desirable wettability, low viscosity, and low cost. However, the mechanism of its poor electrochemical performance is not clear. Herein, the properties of interfacial films on the surface of LiFePO4 (LFP) cathode material formed by electrolytes with different concentrations are compared by interfacial component analysis. It is shown that moderate content of lithium fluoride increases the length of Li+–ethylene carbonate bond from 1.676 to 1.824 Å through lithium bond and then decreases the desolvation activity energy of Li+ ion, which effectively promotes the desolvation process of Li+ ion at the interface of LFP/electrolyte, and finally ensures the perfect performance of the battery. That is, the fundamental cause for the undesirable electrochemical performances of the low‐concentration electrolyte is the low content of LiF components in the interface film rather than the low ionic conductivity of the electrolyte itself. This indicates the direction of optimizing the electrochemical performance of low‐concentration electrolytes.