Effect of excess lithium in LiMn2O4 and Li1.15Mn1.85O4 electrodes revealed by quantitative analysis of soft X-ray absorption spectroscopy
- Peking Univ., Beijing (China); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Peking Univ., Beijing (China)
We performed a comparative study of the soft x-ray absorption spectroscopy of the LiMn2O4 and Li1.15Mn1.85O4 electrode materials with a quantitative analysis of the Mn oxidation states. The revealed redox evolution of Mn upon the electrochemical cycling clarifies the effect of the excess Li in the materials, which naturally explains the different electrochemical performance. The spectral analysis perfectly agrees with the different initial cycling capacities of the two materials. The results show unambiguously that Mn3+ starts to dominate the electrode surface after only one cycle. More importantly, the data show that, while LiMn2O4 electrodes follow the nominal Mn redox evolution, the formation of Mn3+ on the electrode surface is largely retarded for the Li1.15Mn1.85O4 during most of the electrochemical process. Such a different surface Mn redox behavior leads to differences in the detrimental effects of Mn2+ formation on the surface, which is observed directly after only two cycles. Our results provide strong evidence that a key effect of the (bulk) excess Li doping is actually due to processes on the electrode surfaces.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); Shenzhen Municipal Government (China)
- Contributing Organization:
- Peking University; Shenzhen Graduate School (China)
- Grant/Contract Number:
- AC02-05CH11231; 2016YFB0700600; 2013N080; KYPT20141016105435850
- OSTI ID:
- 1393125
- Alternate ID(s):
- OSTI ID: 1343752; OSTI ID: 1348273
- Journal Information:
- Applied Physics Letters, Vol. 110, Issue 9; ISSN 0003-6951
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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