Spatially resolved operando synchrotron-based x-ray diffraction measurements of Ni-rich cathodes for Li-ion batteries

DOI: 10.3389/fceng.2021.794194

Authors: Andrew Stephen Leach (University College London; The Faraday Institution) , Alice Llewellyn (University College London; The Faraday Institution) , Chao Xu (The Faraday Institution; University of Cambridge; ShanghaiTech University) , Chun Tan (University College London; The Faraday Institution) , Thomas M. M. Heenan (University College London; The Faraday Institution) , Alex Dimitrijevic (University College London; The Faraday Institution) , Karin Kleiner (University of Münster (WWU)) , Clare P. Grey (The Faraday Institution; University of Cambridge) , Dan J. L. Brett (University College London; The Faraday Institution) , Chiu C. Tang (Diamond Light Source) , Paul R. Shearing (The Faraday Institution; University College London) , Rhodri Jervis (The Faraday Institution; University College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Frontiers In Chemical Engineering , VOL 3

State: Published (Approved)
Published: January 2022
Diamond Proposal Number(s): 22498 , 24122

Abstract: Understanding the performance of commercially relevant cathode materials for lithium-ion (Li-ion) batteries is vital to realize the potential of high-capacity materials for automotive applications. Of particular interest is the spatial variation of crystallographic behavior across (what can be) highly inhomogeneous electrodes. In this work, a high-resolution X-ray diffraction technique was used to obtain operando transmission measurements of Li-ion pouch cells to measure the spatial variances in the cell during electrochemical cycling. Through spatially resolved investigations of the crystallographic structures, the distribution of states of charge has been elucidated. A larger portion of the charging is accounted for by the central parts, with the edges and corners delithiating to a lesser extent for a given average electrode voltage. The cells were cycled to different upper cutoff voltages (4.2 and 4.3 V vs. graphite) and C-rates (0.5, 1, and 3C) to study the effect on the structure of the NMC811 cathode. By combining this rapid data collection method with a detailed Rietveld refinement of degraded NMC811, the spatial dependence of the degradation caused by long-term cycling (900 cycles) has also been shown. The variance shown in the pristine measurements is exaggerated in the aged cells with the edges and corners offering an even lower percentage of the charge. Measurements collected at the very edge of the cell have also highlighted the importance of electrode alignment, with a misalignment of less than 0.5 mm leading to significantly reduced electrochemical activity in that area.

Journal Keywords: NMC811; Li-ion batteries; operando XRD; SXRD; operando electrochemistry; operando spectroelectrochemistry; battery degeneration

Diamond Keywords: Batteries; Lithium-ion

Subject Areas: Materials, Chemistry, Energy


Instruments: I11-High Resolution Powder Diffraction

Added On: 04/02/2022 08:41

Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science

Technical Tags:

Diffraction