Article Metrics


Online attention

Capacity fading mechanisms of NCM-811 cathodes in lithium-ion batteries studied by X-ray diffraction and other diagnostics

DOI: 10.1149/2.0821915jes DOI Help

Authors: Franziska Friedrich (Technical University of Munich) , Benjamin Strehle (Technical University of Munich) , Anna Freiberg (Technical University of Munich) , Karin Kleiner (Technical University of Munich; Diamond Light Source) , Sarah J. Day (Diamond Light Source) , Christoph Erk (BASF SE Ludwigshafen) , Michele Piana (Technical University of Munich) , Hubert A. Gasteiger (Technical University of Munich)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Journal Of The Electrochemical Society , VOL 166 , PAGES A3760 - A3774

State: Published (Approved)
Published: November 2019
Diamond Proposal Number(s): 16866

Open Access Open Access

Abstract: Ni-rich layered oxides, like NCM-811, are promising lithium-ion battery cathode materials for applications such as electric vehicles. However, pronounced capacity fading, especially at high voltages, still lead to a limited cycle life, whereby the underlying degradation mechanisms, e.g. whether they are detrimental reactions in the bulk or at the surface, are still controversially discussed. Here, we investigate the capacity fading of NCM-811/graphite full-cells over 1000 cycles by a combination of in situ synchrotron X-ray powder diffraction, impedance spectroscopy, and X-ray photoelectron spectroscopy. In order to focus on the NCM-811 material, we excluded Li loss at the anode by pre-lithiating the graphite. We were able to find a quantitative correlation between NCM-811 lattice parameters and capacity fading. Our results prove that there are no considerable changes in the bulk structure, which could be responsible for the observed ≈20% capacity loss over the 1000 cycles. However, we identified the formation of a resistive surface layer, which is responsible for (i) an irreversible loss of capacity due to the material lost for its formation, and (ii) for a considerable impedance growth. Further evidence is provided that the surface layer is gradually formed around the primary NCM-811 particles.

Subject Areas: Chemistry, Energy, Materials

Instruments: I11-High Resolution Powder Diffraction