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Title: Effect of excess lithium in LiMn2O4 and Li1.15Mn1.85O4 electrodes revealed by quantitative analysis of soft X-ray absorption spectroscopy

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.
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [2] ;  [4] ; ORCiD logo [2]
  1. School of Advanced Materials, Peking University, Shenzhen Graduate School, Shenzhen 518055, People's Republic of China; Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA
  2. Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA
  3. Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA
  4. School of Advanced Materials, Peking University, Shenzhen Graduate School, Shenzhen 518055, People's Republic of China
Publication Date:
Grant/Contract Number:
AC02-05CH11231; 2016YFB0700600; 2013N080; KYPT20141016105435850
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 110; Journal Issue: 9; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); Peking Univ., Beijing (China)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V); Shenzhen Municipal Government (China)
Contributing Orgs:
Peking University; Shenzhen Graduate School (China)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; Battery electrode materials, Soft x-ray spectroscopy, Li excess, spinel materials; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Electrodes; Electrochemistry; Doping; Surface oxidation; Spectrum analysis
OSTI Identifier:
1393125
Alternate Identifier(s):
OSTI ID: 1343752; OSTI ID: 1348273