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Identifying the origins of microstructural defects such as cracking within Ni‐rich NMC811 cathode particles for lithium‐ion batteries

DOI: 10.1002/aenm.202002655 DOI Help

Authors: Thomas M. M. Heenan (University College London; The Faraday Institution) , Aaron Wade (University College London; The Faraday Institution) , Chun Tan (University College London; The Faraday Institution) , Julia E. Parker (Diamond Light Source) , Dorota Matras (The Faraday Institution; Diamond Light Source) , Andrew S. Leach (University College London; The Faraday Institution) , James B. Robinson (University College London; The Faraday Institution) , Alice Llewellyn (University College London; The Faraday Institution) , Alexander Dimitrijevic (University College London; The Faraday Institution) , Rhodri Jervis (University College London; The Faraday Institution) , Paul D. Quinn (The Faraday Institution; Diamond Light Source) , Dan J. L. Brett (University College London; The Faraday Institution) , Paul R. Shearing (University College London; The Faraday Institution)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Energy Materials , VOL 1

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 20841 , 23858

Open Access Open Access

Abstract: The next generation of automotive lithium‐ion batteries may employ NMC811 materials; however, defective particles are of significant interest due to their links to performance loss. Here, it is demonstrated that even before operation, on average, one‐third of NMC811 particles experience some form of defect, increasing in severity near the separator interface. It is determined that defective particles can be detected and quantified using low resolution imaging, presenting a significant improvement for material statistics. Fluorescence and diffraction data reveal that the variation of Mn content within the NMC particles may correlate to crystallographic disordering, indicating that the mobility and dissolution of Mn may be a key aspect of degradation during initial cycling. This, however, does not appear to correlate with the severity of particle cracking, which when analyzed at high spatial resolutions, reveals cracking structures similar to lower Ni content NMC, suggesting that the disconnection and separation of neighboring primary particles may be due to electrochemical expansion/contraction, exacerbated by other factors such as grain orientation that are inherent in such polycrystalline materials. These findings can guide research directions toward mitigating degradation at each respective length‐scale: electrode sheets, secondary and primary particles, and individual crystals, ultimately leading to improved automotive ranges and lifetimes.

Journal Keywords: batteries; cathodes; degradation; electric vehicles; microstructure; NMC811; particle cracking

Diamond Keywords: Batteries; Electric Vehicles; Lithium-ion

Subject Areas: Materials, Chemistry, Energy


Instruments: I14-Hard X-ray Nanoprobe

Added On: 12/11/2020 09:36

Documents:
aenm.202002655.pdf

Discipline Tags:

Physical Chemistry Energy Energy Storage Automotive Materials Science Energy Materials Chemistry

Technical Tags:

Diffraction Imaging X-ray Fluorescence (XRF)