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Enabling High-Energy Battery Performance of 4.8 V Li-Rich Layered Oxide Cathode with a High-Voltage Additive

Monday, 25 May 2015: 09:00
Salon A-4 (Hilton Chicago)
H. Q. Pham (Chungnam National University), E. H. Hwang, Y. G. Kwon (Leechem Co., Ltd.,), and S. W. Song (Chungnam National University)
Li-rich layered oxide of xLi2MnO3.(1−x)Li(Mn,Ni,Co)O2 is an attractive cathode material for high-energy density Li-ion batteries because of a possible attainment of high capacity as much as or higher than 250 mAhg−1 on the operation above 4.6 V vs. Li/Li+.1 Its performance however has been limited by high-voltage operation (> 4.3 V), due to anodic instability of conventional electrolyte and interfacial instability of the cathode. Here we report high performance of half-cell and full-cell with Li1.2Mn0.525Ni0.175Co0.1O2 cathode and fluorinated linear carbonate (di-(2,2,2 trifluoroethyl)carbonate, DFDEC) as a novel high-voltage electrolyte additive, on the high-voltage operation to 4.8 V.2 The full cell consisting of Li1.2Mn0.525Ni0.175Co0.1O2 cathode and graphite anode in the electrolyte of 1M LiPF6/EC:EMC only experiences a rapid capacity fade when being operated at 2.5- 4.75V, resulting in just 32 % capacity retention after 60 cycles. Although the performance improves with the use of DFDEC, a notable performance improvement is achieved when using the blended additives of DFDEC and VC, which is a well-known SEI-forming agent for graphite anode,3 delivering high discharge capacities of 231 − 189 mAhg−1 with the capacity retention of 82 % at the 60th cycle. The full-cell demonstrates doubled energy density (~278 Whkg−1) compared to ~136 Whkg−1 of a commercialized cell of graphite//LiCoO2. Spectroscopic surface chemistry studies indicate that DFDEC plays a critical role in stabilizing the SEI and inhibiting the interfacial degradation of cathode. The details of interfacial reaction (SEI formation) mechanisms, SEI composition and stability, and their relation to high-voltage cycling performance at room and elevated temperatures would be presented in the meeting.

References

1) M. M. Thackeray, S.-H. Kang, C. S. Johnson, J. T. Vaughey, S. A. Hackney, Electrochem. Commun., 8, 1531 (2006).

2) H. Q. Pham, K.-M. Nam, E.-H. Hwang, Y.-G. Kwon, H. M. Jung, S.-W. Song, J. Electrochem. Soc., 161, A2002 (2014).

3) L. El Ouatani, R. Dedryve╠re, C. Siret, P. Biensan, S. Reynaud, P. Iratçabal, D. Gonbeau, J. Electrochem. Soc., 156, A103 (2009).

Acknowledgements

This research was financially supported by the Korean Ministry of Trade, Industry & Energy (A0022–00725) and by the Ministry of Education (2012026203).