Effects of different elements based electrolyte additives on the performance and interfacial chemistry of high-voltage LiCoO2/artificial graphite pouch cell

Abstract

Film-forming electrolyte additives are widely used for optimizing cathode/electrolyte interphase (CEI) films of LiCoO2-based lithium-ion batteries. Nevertheless, the effects of the four typical additives with different elements including vinylene carbonate (VC), 1,3-propane sultone (PS), fluoroethylene carbonate (FEC), and adiponitrile (ADN) on interfacial chemistries of LiCoO2 cathode and practical performances of LiCoO2-based batteries at various temperatures are still unclear. Herein, the four additives are evaluated for a LiCoO2/artificial graphite pouch cell at 3−4.5 V. It is found that the additives significantly affect the discharge capacities of the cells at −20 °C and various rates, and stabilities when stored at 60 °C and cycled at room temperature. Among them, the FEC-containing cell exhibits the most outstanding performance while PS has a low positive effect on almost all properties. VC enables good kinetic abilities when ADN can improve stability. Combined with physical characterizations and theoretical calculation, the functional mechanisms of the additives on LiCoO2 cathode are understudied. Results demonstrate that the additives dictate CEI films possessing specific elements through oxygenolysis, surface adsorption or passivation, then adjust the morphologies and protection effects of CEI films. These findings can provide important information for fundamental exploration and engineering design of high-voltage LiCoO2-based batteries.