Unraveling the state of charge-dependent electronic and ionic structure–property relationships in NCM622 cells by multiscale characterization

DOI: 10.1021/acsaem.1c03173

Authors: Albina Jetybayeva (Korea Advanced Institute of Science and Technology (KAIST)) , Nino Schön (Forschungszentrum Jülich; RWTH Aachen University) , Jimin Oh (Korea Advanced Institute of Science and Technology (KAIST); Electronics and Telecommunications Research Institute (ETRI)) , Jaegyu Kim (Korea Advanced Institute of Science and Technology (KAIST)) , Hongjun Kim (Korea Advanced Institute of Science and Technology (KAIST)) , Gun Park (Korea Advanced Institute of Science and Technology (KAIST)) , Young-Gi Lee (Electronics and Telecommunications Research Institute (ETRI)) , Rüdiger-A. Eichel (Forschungszentrum Jülich; RWTH Aachen University) , Karin Kleiner (University of Münster) , Florian Hausen (Forschungszentrum Jülich; RWTH Aachen University) , Seungbum Hong (Korea Advanced Institute of Science and Technology (KAIST); KAIST Institute for the NanoCentury)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Applied Energy Materials

State: Published (Approved)
Published: January 2022
Diamond Proposal Number(s): 19772

Abstract: LiNi0.6Co0.2Mn0.2O2 (NCM622) undergoes crystallographic and electronic changes when charging and discharging, which drive the cathode material close to or even beyond its stability window. To unravel the charge compensation mechanism of NCM622, spatially resolved atomic force microscopy (AFM) measurements in electrochemical strain microscopy (ESM) and conductive AFM (C-AFM) modes are obtained, and the spectroscopic information and crystallographic information are compared. All experiments are performed with two sets of samples: state-of-the-art samples that are composed of a binder, a conductive additive, and an active material and polished samples for single-particle analysis. Near-edge X-ray absorption fine structure spectroscopy shows that ionic Ni2+ reacts to give Ni3+ when charging and forms covalent bonds with its oxygen neighbors. A Ni2+/Ni3+ gradient across the particles balances out with the increasing state of charge, as verified by ESM. Therefore, the results also provide an important view that improves the mechanistic understanding of ESM in electrode materials. Finally, the interplay between the electronic and ionic conductivities and the crystallinities of NCM622 cathodes is elaborated and discussed.

Journal Keywords: NCM622; state of charge; electrochemical strain microscopy; conductive atomic force microscopy; near-edge X-ray absorption

Diamond Keywords: Batteries; Lithium-ion; Electric Vehicles

Subject Areas: Materials, Chemistry, Energy


Instruments: I11-High Resolution Powder Diffraction

Added On: 26/01/2022 09:01

Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science Chemical Engineering Engineering & Technology

Technical Tags:

Diffraction X-ray Powder Diffraction