Enabling the high energy density Li-ion batteries requires the use of high-capacity cathode material such as Li-rich layered oxide cathode (xLi₂MnO₃·(1-x)LiMO₂ (M=Mn,Ni,Co)) that can be charged to high-voltage above 4.4 V vs. Li/Li⁺. The development of new electrolyte components with high anodic stability above 4.4 V vs. Li/Li⁺ is thus the necessity of high-voltage charging of Li-rich layered oxide cathode. Our recent research results have shown that the use of high-voltage electrolyte additives is effective in charging the Li-ion cell with Li-rich layered oxide cathode above 4.6 V vs. Li/Li⁺ and even at elevated temperatures, which enables high-energy density Li-ion cells. Systematic surface analyses of the cathodes revealed that the formation of surface protective film by the use of high-voltage additives led to interfacial stabilization of both cathode and anode and significantly improved cycling performance, compared to the case of conventional electrolyte. In this presentation, we report the stabilization of high-voltage interface of Li-rich layered oxide cathode under a harsh condition of high charge cut-off voltage above 4.6 V vs. Li/Li⁺ using fluorinated carbonates as high-voltage electrolyte additives. The results of mechanistic studies of high-voltage surface film formation and composition, and interfacial stability of Li-rich layered oxide cathode using surface sensitive spectroscopy combined with electrochemical impedance spectroscopy would be discussed.

Acknowledgements: This research was supported by the Korean Ministry of Trade, Industry & Energy (R0004645) and Chungnam National University.