An increase in the energy density of lithium-ion batteries has long been a competitive advantage for advanced wireless devices and long-driving electric vehicles. Li-rich layered oxide, xLi₂MnO₃∙(1−x)LiMn_1−y−zNi_yCo_zO₂ (LMNC), is a promising high-capacity cathode material for high-energy batteries, whose capacity increases by increasing the charge cut-off voltage to above 4.6 V vs. Li/Li⁺.^1,2 Li-rich layered oxide cathode however suffers from a rapid capacity fade during the high-voltage cycling because of instable cathode-electrolyte interface, and the occurrence of metal-dissolution, particle cracking and structural degradation, particularly, at elevated temperatures.² Herein, we report the development of a novel high-voltage binder (P), which mitigates the cathode degradation problems through superior binding ability to conventional polyvinylidenefluoride (PVdF) binder and the formation of robust surface structure at the cathode. While P-LMNC//graphite full-cell with 1M LiPF₆/EC:EMC without any electrolyte additive shows a stable cycling performance over 100 cycles even in the harsh operation condition of 55 ^○C between 2.5 and 4.7 V at 0.2C delivering capacity retention of 89% and high cyclic coulombic efficiencies close to 100%, a very rapid capacity fade and poor coulombic efficiencies are observed with PVdF-LMNC//graphite full-cell.³ This is so far the best and first performance ever reported for high-voltage full-cell at elevated temperature without any electrolyte additive. The detailed studies of surface composition and formation mechanism, and their relation to high-voltage and high-temperature cycling performance would be presented in the meeting.

Acknowledgements

This research was supported by National Research Foundation of Korea (NRF-2015R1D1A1A01060838) and Chungnam National University.

References

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2. H. Q. Pham, E.-H. Hwang, Y.-G. Kwon, S.-W. Song, J. Power Sources, 323, 220, (2016).
3. H. Q. Pham, G. Kim, H. M. Jung, S.-W. Song, Adv. Func. Mater., in press (2017).