In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2016-03, No. 2 ( 2016-06-10), p. 157-157
Abstract:
In the presence of literatures [1-4], high-voltage ( 〉 4.8V; 5V class) Li-rich layer compounds (Li[Ni x Li (1-2x)/3 Mn (2-x)/3 ]O 2 ) have been reported to the next candidate of cathode materials in order to increase the power and energy density instead of LiCoO 2 or LiNi x Mn y Co z O 2 conventional materials. These high-voltage Li-rich layer materials dedicate their high reversible capacities more than 270 mAh g -1 , which is almost twice as higher as LiCoO 2 . However, this material suffers dramatically challenge due to the irreversible phase change in the first charge. Several studies had discussed the failure mechanism of this high voltage material; however, those comments are different. Mantia et al. [1] have demonstrated direct evidence of oxygen evolution from the Li-excess material at high potentials by in situ differential electrochemical mass spectrometry (DEMS) as well as Hy et al. [2] shown an oxygen activation occurs following electrochemical reaction and forms an irreversible formation of Li 2 O by surface enhanced Raman spectroscopy (SERS). In Jiang’s result [3], they are unable to detect any oxygen in their ex situ observation. Their XRD pattern and 6 Li MAS NMR spectrum comment O 2- loss is accompanied with the electrolyte to form CO 2 . In our novel in-situ gas evolution experiment, we showed that there are two reaction mechanisms in the first charge process in Figure 1. In the first reaction mechanism, the CO 2 (m/z 44) and CO (m/z 28) generate drastically at the potential of 4.25V. In comparison with cyclic voltammogram (CV) (not shown in here), the potential of 4.25V is indicated to the reaction of Ni 3+ /Ni 4+ ; therefore, the gas evolution at this stage can be concluded the electrolyte is partially decomposed with the catalyst of Ni 3+ /Ni 4+ and the oxygen evolution is not correlated. Second reaction mechanism starts at 4.65V, the CO 2 forms solely in accompanied with oxygen evolution (m/z 32) from cathode material. Above result indicates that the second reaction mechanism is lead by the oxygen evolution and further reacts with electrolyte. In this research, we establish a novel in-situ observation for evaluating gas evolution and define the reaction mechanisms of high voltage cathode material. Reference [1] F. La Mantia, F. Rosciano, N. Tran, P. Novak, J. Appl. Electrochem. 38 (2008) 893 [2] Sunny Hy, Felix, John Rick, Wei-Nien Su, Bing Joe Hwang, J. Am. Chem. Soc. 136 (2014) 999 [3] Meng Jiang, Baris Key, Ying S. Meng, and Clare P. Grey,
Chem. Mater. 21 (2009) 2733 Figure 1
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2016-03/2/157
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2016
detail.hit.zdb_id:
2438749-6
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