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Elucidating and Mitigating High-Voltage Interfacial Chemomechanical Degradation of Nickel-Rich Lithium-Ion Battery Cathodes via Conformal Graphene Coating

  • Luu, Norman S.
  • Lim, Jin-Myoung
  • Torres-Castanedo, Carlos G.
  • Park, Kyu-Young
  • Moazzen, Elahe
  • He, Kun
  • Meza, Patricia E.
  • Li, Wenyun
  • Downing, Julia R.
  • Hu, Xiaobing
  • Dravid, Vinayak P.
  • Barnett, Scott A.
  • Bedzyk, Michael J.
  • Hersam, Mark C.
Publication Date
Sep 28, 2021
[email protected]
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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

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