3D tomography and imaging
3D tomography and imaging research
2011-03 Investigation of battery failure with XCT
Investigation of lithium-ion polymer battery cell failure using X-ray computed tomography. V. Yufit, P. Shearing, R.W. Hamilton, P.D. Lee, M. Wu, N.P. Brandon. Electrochemistry Communications. 2011, 13, 608–610.
The paper presents the first application of laboratory X-ray μCT for post-mortem analysis of a failed lithium-ion polymer battery pouch cell. Analysis of the μCT data allowed quantification of the physical distortion within the individual cell layers of both an untested and failed cell. In the failed cell, the maximum separation of the electrode assemblies was measured in each direction (XY = 833 μm, YZ = 787 μm), representing a significant increase from the untested cell, where the spacing was below 43 μm. Deformation was more prominent in the central region of the cell since both ends of the battery electrodes remained tightly clamped even after failure. Based on the visually observed volume expansion and the deformation of the cell architecture observed by μCT we conclude that the deformation was caused by pressure build up as a result of gas generation, which could have arisen from a short circuit in the cell.
2013-05 Image based modelling of LFP microstructures for lithium-ion batteries
Image based modelling of microstructural heterogeneity in LiFePO4 electrodes for Li-ion batteries. S.J. Cooper, D.S. Eastwood, J. Gelb, G. Damblanc, D.J.L. Brett, R.S. Bradley, P.J. Withers, P.D. Lee, A.J. Marquis, N.P. Brandon, P.R. Shearing. Journal of Power Sources. 2014, 247, 1033-1039.
Battery and fuel cell simulations commonly assume that electrodes are macro-homogeneous and isotropic. These simulations have been used to successfully model performance, but give little insight into predicting failure. In Li-ion battery electrodes, it is understood that local tortuosity impacts charging rates, which may cause increased degradation. This report describes a novel approach to quantifying tortuosity based on a heat transfer analogy applied to X-ray microscopy data of a commercially available LiFePO4 electrode. This combination of X-ray imaging and image-based simulation reveals the microscopic performance of the electrode; notably, the tortuosity was observed to vary significantly depending on the direction considered, which suggests that tortuosity might best be quantified using vectors rather than scalars.
2013-10 XCT of mesocarbon microbead anodes for lithium-ion batteries
Three-dimensional high resolution X-ray imaging and quantification of lithium ion battery mesocarbon microbead anodes. F. Tariq, V. Yufit, M. Kishimoto, P. R. Shearing, S. Menkin, D. Golodnitsky, J. Gelb, E. Peled and N. P. Brandon. Journal of Power Sources. 2014, 248, 1014-1020.
In order to improve lithium ion batteries it is important to characterise real electrode geometries and understand how their 3D structure may affect performance. In this study, high resolution synchrotron nano-CT was used to acquire 3D tomography datasets of mesocarbon microbead (MCMB) based anodes down to a 16 nm voxel size. A specimen labelling methodology was used to produce anodes that enhance the achievable image contrast, and image processing routines were utilised to successfully segment features of interest from a challenging dataset. The 3D MCMB based anode structure was analysed revealing a heterogeneous and bi-modally distributed microstructure. The microstructure was quantified through calculations of surface area, volume, connectivity and tortuosity factors. In doing so, two different methods, random walk and diffusion based, were used to determine tortuosity factors of both MCMB and pore/electrolyte microstructures. The tortuosity factors (2–7) confirmed the heterogeneity of the anode microstructure for this field of view and demonstrated small MCMB particles interspersed between large MCMB particles cause an increase in tortuosity factors. The anode microstructure was highly connected, which was also caused by the presence of small MCMB particles. The complexity in microstructure suggests inhomogeneous local lithium ion distribution would occur within the anode during operation.
2014-05 In-operando XCT of silicon lithiation
In-Operando X-ray Tomography Study of Lithiation Induced Delamination of Si Based Anodes for Lithium-Ion Batteries. F. Tariq, V. Yufit, D. S Eastwood, Y. Merla, M. Biton, B. Wu, Z. Chen, K. Freedman, G. Offer, E. Peled, P. D. Lee, D. Golodnitsky and N. Brandon. ECS Electrochemistry Letters. 2014, 3, 7, A76-A78.
Silicon-Lithium based rechargeable batteries offer high gravimetric capacity. However cycle life and electrode microstructure failure mechanisms remain poorly understood. Here we present an X-ray tomography method to investigate in-operando lithiation induced stress cracking leading to the delamination of a composite Si based electrode. Simultaneous voltage measurements show increased cell resistance correlating with severe delamination and microstructural changes. 3D analysis revealed 44.1% loss of the initial electrode-current collector area after 1 hour of operation at 2.4 mA/cm2 and a 21.2% increase in new anode surface area. The work represents a new basis for future investigation of Si based anodes.
2016-09 Enhanced imaging of lithium ion battery electrode materials
Enhanced Imaging of Lithium Ion Battery Electrode Materials. M. Biton, V. Yufit, F. Tariq, M. Kishimoto, N. Brandon. Journal of the Electrochemical Society. 2017, 164, 1, A6032-A6038.
In this study we present a novel method of lithium ion battery electrode sample preparation with a new type of epoxy impregnation, brominated (Br) epoxy, which is introduced here for the first time for this purpose and found suitable for focused ion beam scanning electron microscope (FIB-SEM) tomography. The Br epoxy improves image contrast, which enables higher FIB-SEM resolution (3D imaging), which is amongst the highest ever reported for composite LFP cathodes using FIB-SEM. In turn it means that the particles are well defined and the size distribution of each phase can be analyzed accurately from the complex 3D electrode microstructure using advanced quantification algorithms.
The authors present for the first time a new methodology of contrast enhancement for 3D imaging, including novel advanced quantification, on a commercial Lithium Iron Phosphate (LFP) LiFePO4 cathode. The aim of this work is to improve the quality of the 3D imaging of challenging battery materials by developing methods to increase contrast between otherwise previously poorly differentiated phases. This is necessary to enable capture of the real geometry of electrode microstructures, which allows measurement of a wide range of microstructural properties such as pore/particle size distributions, surface area, tortuosity and porosity. These properties play vital roles in determining the performance of battery electrodes.