Elucidating and Mitigating High-Voltage Interfacial Chemomechanical Degradation of Nickel-Rich Lithium-Ion Battery Cathodes via Conformal Graphene Coating
- Authors
- Publication Date
- Sep 28, 2021
- Source
- OASIS@POSTECH
- Keywords
- License
- Unknown
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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. © / 1 / 1 / N / scie / scopus