Abstract
Spinel-type lithium manganese oxide (LiMn2O4) cathodes suffer from severe manganese dissolution in the electrolyte, compromising the cyclic stability of LMO-based Li-ion batteries (LIBs). In addition to causing structural and morphological deterioration to the cathode, dissolved Mn ions can migrate through the electrolyte to deposit on the anode, accelerating capacity fade. Here, we examine single-crystal epitaxial LiMn2O4(111) thin-films using synchrotron in situ X-ray diffraction and reflectivity to study the structural and interfacial evolution during cycling. Cyclic voltammetry is performed in a wide range (2.5-4.3 V vs Li/Li+) to promote Mn3+formation, which enhances dissolution, for two different electrolyte systems: an imidazolium ionic liquid containing lithium bis-(trifluoromethylsulfonyl)imide (LiTFSI) and a conventional carbonate liquid electrolyte containing lithium hexafluorophosphate (LiPF6). We find exceptional stability in this voltage range for the ionic liquid electrolyte compared to the conventional electrolyte, which is attributed to the absence of Mn dissolution in the ionic liquid. X-ray reflectivity shows a negligible loss of cathode material for the films cycled in the ionic liquid electrolyte, further confirmed by inductively coupled plasma mass spectrometry and transmission electron microscopy. Conversely, a substantial loss of Mn is found when the film is cycled in the conventional electrolyte. These findings show the significant advantages of ionic liquids in suppressing Mn dissolution in LiMn2O4LIB cathodes.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 35664-35673 |
| Number of pages | 10 |
| Journal | ACS Applied Materials and Interfaces |
| Volume | 15 |
| Issue number | 29 |
| DOIs | |
| State | Published - Jul 26 2023 |
Funding
This research was primarily supported by the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, and Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The authors thank beamline scientist Jenia (Evguenia) Karapetrova for supporting the in situ X-ray experiments at the Advanced Photon Source 33-BMC beamline. They also thank Denis Keane for his assistance in the lab located in the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) situated in Sector 5 of the Advanced Photon Source. DND-CAT is supported by Northwestern University, The Dow Chemical Company, and DuPont de Nemours, Inc. This work made use of the X-ray Diffraction and Pulsed Laser Deposition Facilities supported by the MRSEC program of the National Science Foundation (NSF DMR-1720139) at the Materials Research Center of Northwestern University and the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205). Metal analysis by ICP-MS was performed at the Northwestern University Quantitative Bio-element Imaging Center (QBIC), generously supported by NASA Ames Research Center Grant NNA04CC36G. XPS measurements were performed in the Keck-II facility of the Northwestern University NUANCE Center, which is supported by NSF DMR-1720139 and NSF ECCS-1542205.
Keywords
- LIB
- LiMnO
- epitaxial thin-films
- in situ
- ionic liquid
- manganese dissolution
ASJC Scopus subject areas
- General Materials Science