Abstract
Lithium nickel manganese cobalt oxides (NMCs) are promising cathode materials for high-performance lithium-ion batteries. Although these materials are commonly cycled within mild voltage windows (up to 4.3 V vs Li/Li+), operation at high voltages (>4.7 V vs Li/Li+) to access additional capacity is generally avoided due to severe interfacial and chemomechanical degradation. At these high potentials, NMC degradation is caused by exacerbated electrolyte decomposition reactions and non-uniform buildup of chemomechanical strains that result in particle fracture. By applying a conformal graphene coating on the surface of NMC primary particles, we find significant enhancements in the high-voltage cycle life and Coulombic efficiency upon electrochemical cycling. Postmortem X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy suggest that the graphene coating mitigates electrolyte decomposition reactions and reduces particle fracture and electrochemical creep. We propose a relationship between the spatial uniformity of lithium flux and particle-level mechanical degradation and show that a conformal graphene coating is well-suited to address these issues. Overall, these results delineate a pathway for rationally mitigating high-voltage chemomechanical degradation of nickel-rich cathodes that can be applied to existing and emerging classes of battery materials.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 11069-11079 |
| Number of pages | 11 |
| Journal | ACS Applied Energy Materials |
| Volume | 4 |
| Issue number | 10 |
| DOIs | |
| State | Published - Oct 25 2021 |
Funding
The authors thank Cesar Villa for helpful discussions about TEM, as well as Dr. Lei Li and Dr. Kan-Sheng Chen for early discussions on this project. This work was primarily supported by the Exelon Corporation. Graphene powder production was supported by the National Science Foundation Scalable Nanomanufacturing Program (NSF CMMI-1727846 and NSF CMMI-2039268) and the National Science Foundation Future Manufacturing Program (NSF CMMI-2037026). Electrochemical characterization was supported by the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences under Award No. DE-AC02-06CH11357. Synchrotron radiation powder X-ray diffraction was performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, The Dow Chemical Company, and DuPont de Nemours, Inc. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The authors thank DND-CAT Engineer Mike Guise for his valuable assistance in the beamline during the COVID-19 pandemic. The authors also thank DND-CAT Director Denis T. Keane for his support and helpful discussions. This work made use of the Keck-II and EPIC facilities of the Northwestern University NUANCE Center, which has received support from the SHyNE Resource (NSF ECCS-1542205), the IIN, and the Northwestern University MRSEC program (NSF DMR-1720139). Metal analysis was performed at the Northwestern University Quantitative Bio-Element Imaging Center, which is supported by NASA Ames Research Center NNA06CB93G.
Keywords
- Coulombic efficiency
- battery cathode
- chemomechanical degradation
- cycle life
- electrochemical creep
- high voltage
- lithium nickel manganese cobalt oxide
ASJC Scopus subject areas
- Chemical Engineering (miscellaneous)
- Energy Engineering and Power Technology
- Materials Chemistry
- Electrical and Electronic Engineering
- Electrochemistry
