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Ralf F.
Ziesche
,
Jennifer
Hack
,
Lara
Rasha
,
Maximilian
Maier
,
Chun
Tan
,
Thomas M. M.
Heenan
,
Henning
Markötter
,
Nikolay
Kardjilov
,
Ingo
Manke
,
Winfred
Kockelmann
,
Dan J. L.
Brett
,
Paul R.
Shearing
Open Access
Abstract: In recent years, low-temperature polymer electrolyte fuel cells have become an increasingly important pillar in a zero-carbon strategy for curbing climate change, with their potential to power multiscale stationary and mobile applications. The performance improvement is a particular focus of research and engineering roadmaps, with water management being one of the major areas of interest for development. Appropriate characterisation tools for mapping the evolution, motion and removal of water are of high importance to tackle shortcomings. This article demonstrates the development of a 4D high-speed neutron imaging technique, which enables a quantitative analysis of the local water evolution. 4D visualisation allows the time-resolved studies of droplet formation in the flow fields and water quantification in various cell parts. Performance parameters for water management are identified that offer a method of cell classification, which will, in turn, support computer modelling and the engineering of next-generation flow field designs.
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Mar 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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William Q.
Walker
,
Kylie
Cooper
,
Peter
Hughes
,
Ian
Doemling
,
Mina
Akhnoukh
,
Sydney
Taylor
,
Jacob
Darst
,
Julia
Billman
,
Matthew
Sharp
,
David
Petrushenko
,
Rhodri
Owen
,
Martin
Pham
,
Thomas
Heenan
,
Alexander
Rack
,
Oxana
Magdysyuk
,
Thomas
Connolley
,
Dan
Brett
,
Paul
Shearing
,
Donal
Finegan
,
Eric
Darcy
Diamond Proposal Number(s):
[24112, 20903, 17641]
Abstract: Consideration of thermal runaway heat output variability is paramount for the development of safe lithium-ion battery assemblies. This study utilizes data gathered from fractional thermal runaway calorimetry (FTRC) experiments to conduct a comparative analysis of thermal runaway heat output for three cell formats (18650, 21700, and 33600) as a function of trigger method (heaters, internal short-circuiting device, and nail penetration). The analysis is based on comparisons for the calculated total energy yield, fractional energy yield, heat rate, and heat flux. This study reveals that nail penetration tends to result in higher thermal runaway heat output for larger cells (21700 & 33600); these experiments also tended to result in higher fractions of the total energy being released through the cell body. The smaller cells (18650) did not appear to have significant variation in heat output as a function of trigger method. This finding suggests that, for this cell type, worst-case scenario heat output could be achievable in assembly level testing regardless of the utilized trigger method. This study also demonstrates successful translation of FTRC results, as recorded in the Battery Failure Databank, into meaningful analysis that breaks down the influence of specific conditions on thermal runaway heat output.
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Mar 2022
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Abstract: Advanced batteries are critical to achieving net zero and are proposed within decarbonization strategies for transport and grid-scale applications, alongside their ubiquitous application in consumer devices. Immense progress has been made in lithium battery technology in recent years, but significant challenges remain and new development strategies are required to improve performance, fully exploit power density capacities, utilize sustainable resources, and lower production costs. Suitable characterization techniques are crucial for understanding, inter alia, three-dimensional (3D) diffusion processes and formation of passivation layers or dendrites, which can lead to drastic capacity reduction and potentially to hazardous short circuiting. Studies of such phenomena typically utilize 2D or 3D imaging techniques, providing locally resolved information. 3D X-ray imaging is a widely used standard method, while time-lapse (4D) tomography is increasingly required for understanding the processes and transformations in an operational battery. Neutron imaging overcomes some of the limitations of X-ray tomography for battery studies. Notably, the high visibility of neutrons for light-Z elements, in particular hydrogen and lithium, enables the direct observation of lithium diffusion, electrolyte consumption, and gas formation in lithium batteries. Neutron imaging as a non-destructive analytical tool has been steadily growing in many disciplines as a result of improvements to neutron detectors and imaging facilities, providing increasingly higher spatial and temporal resolutions. Further, ongoing developments in diffraction imaging for mapping the structural and microstructural properties of battery components make the use of neutrons increasingly attractive. Here, we provide an overview of neutron imaging techniques, generally outlining advances and limitations for studies on batteries and reviewing imaging studies of lithium batteries. We conclude with an outlook on development methods in the field and discuss their potential and significance for future battery research.
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Jan 2022
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I11-High Resolution Powder Diffraction
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Andrew Stephen
Leach
,
Alice
Llewellyn
,
Chao
Xu
,
Chun
Tan
,
Thomas M. M.
Heenan
,
Alex
Dimitrijevic
,
Karin
Kleiner
,
Clare P.
Grey
,
Dan J. L.
Brett
,
Chiu C.
Tang
,
Paul R.
Shearing
,
Rhodri
Jervis
Diamond Proposal Number(s):
[22498, 24122]
Open Access
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.
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Jan 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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Matt
Sharp
,
John
Darst
,
Peter
Hughes
,
Julia
Billman
,
Martin
Pham
,
David
Petrushenko
,
Thomas
Heenan
,
Rhodri
Jervis
,
Rhodri Ellis
Owen
,
Drasti
Patel
,
Wenjia
Du
,
Harry
Michael
,
Alexander
Rack
,
Oxana
Magdysyuk
,
Thomas
Connolley
,
Dan
Brett
,
Gareth
Hinds
,
Matthew
Keyser
,
Eric
Darcy
,
Paul
Shearing
,
William Q.
Walker
,
Donal
Finegan
Diamond Proposal Number(s):
[24112, 20903, 17641]
Open Access
Abstract: Thermal runaway of lithium-ion batteries can involve various types of failure mechanisms each with their own unique characteristics. Using fractional thermal runaway calorimetry and high-speed radiography, the response of three different geometries of cylindrical cell (18650, 21700, and D-cell) to different abuse mechanisms (thermal, internal short circuiting, and nail penetration) are quantified and statistically examined. Correlations between the geometry of cells and their thermal behavior are identified, such as increasing heat output per amp-hour (kJ Ah-1) of cells with increasing cell diameter during nail penetration. High-speed radiography reveals that the rate of thermal runaway propagation within cells is generally highest for nail penetration where there is a relative increase in rate of propagation with increasing diameter, compared to thermal or internal short-circuiting abuse. For a given cell model tested under the same conditions, a distribution of heat output is observed with a trend of increasing heat output with increased mass ejection. Finally, internal temperature measurements using thermocouples embedded in the penetrating nail are shown to be unreliable thus demonstrating the need for care when using thermocouples where the temperature is rapidly changing. All data used in this manuscript are open access through the NREL and NASA Battery Failure Databank.
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Jan 2022
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B18-Core EXAFS
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Diamond Proposal Number(s):
[24178]
Open Access
Abstract: Nickel-rich cathodes (LiNixMnyCo1-x-yO2, x > 0.6) permit higher energy in lithium-ion rechargeable batteries but suffer from accelerated degradation at potentials above 4.1 V versus Li/Li+. Here, we present a proof-of-concept in situ pouch cell and methodology for correlative 2D synchrotron transmission X-ray microscopy with 3D lab-based micro-CT. XANES analysis of the TXM data enables tracking of Ni edge energy within and between the polycrystalline NMC811 particles embedded in the operating electrode through its initial delithiation. By using edge energy as a proxy, state-of-charge heterogeneities can be tracked at the nanoscale, revealing the role of cracked particles as potential nucleation points for failure and highlighting the challenges in achieving uniform (de-)lithiation. We propose, in future work, to leverage the pouch cell design presented here for longitudinal TXM-XANES studies of nickel-rich cathodes across multiple cycles and operating variables and investigate the effect of dopants and microstructural optimization in mitigating degradation.
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Nov 2021
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B18-Core EXAFS
I22-Small angle scattering & Diffraction
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Jingyu
Feng
,
Rongsheng
Cai
,
Emanuele
Magliocca
,
Hui
Luo
,
Luke
Higgins
,
Giulio L. Fumagalli
Romario
,
Xiaoqiang
Liang
,
Angus
Pedersen
,
Zhen
Xu
,
Zhenyu
Guo
,
Arun
Periasamy
,
Dan
Brett
,
Thomas S.
Miller
,
Sarah J.
Haigh
,
Bhoopesh
Mishra
,
Maria-Magdalena
Titirici
Diamond Proposal Number(s):
[26201, 27900]
Open Access
Abstract: Atomically dispersed transition metal-nitrogen-carbon catalysts are emerging as low-cost electrocatalysts for the oxygen reduction reaction in fuel cells. However, a cost-effective and scalable synthesis strategy for these catalysts is still required, as well as a greater understanding of their mechanisms. Herein, iron, nitrogen co-doped carbon spheres (Fe@NCS) have been prepared via hydrothermal carbonization and high-temperature post carbonization. It is determined that FeN4 is the main form of iron existing in the obtained Fe@NCS. Two different precursors containing Fe2+ and Fe3+ are compared. Both chemical and structural differences have been observed in catalysts starting from Fe2+ and Fe3+ precursors. Fe2+@NCS-A (starting with Fe2+ precursor) shows better catalytic activity for the oxygen reduction reaction. This catalyst is studied in an anion exchange membrane fuel cell. The high open-circuit voltage demonstrates the potential approach for developing high-performance, low-cost fuel cell catalysts.
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Aug 2021
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
E01-JEM ARM 200CF
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Zhangxiang
Hao
,
Junrun
Feng
,
Yiyun
Liu
,
Liqun
Kang
,
Bolun
Wang
,
Junwen
Gu
,
Lin
Sheng
,
Ruoyu
Xu
,
Sushila
Marlow
,
Dan J.l.
Brett
,
Yunhui
Huang
,
Feng Ryan
Wang
Diamond Proposal Number(s):
[22572, 21641, 22604, 26717, 29407]
Abstract: Polymer materials offer controllable structure-dependent performances in separation, catalysis and drug release. Their molecular structures can be precisely tailored to accept Li+ for energy storage applications. Here the design of sp2 carbon-based polyphenylene (PPH) with high lithium-ion uptakes and long-term stability is reported. Linear-PPH (L-PPH) exceeds the performance of crosslink-PPH (C-PPH), due to the fact that it has an ordered lamellar structure, promoting the Li+ intercalation/deintercalation channel. The L-PPH cell shows a clear charge and discharge plateau at 0.35 and 0.15 V vs. Li+/Li, respectively, which is absent in the C-PPH cell. The Li+ storage capacity of L-PPH is five times that of the C-PPH. The reversible storage capacity is further improved to 261 mAh g−1 by functionalizing the L-PPH with the –SO3H groups. In addition, the Li-intercalated structures of C-PPH and L-PPH are investigated via near-edge X-ray absorption fine structure (NEXAFS), suggesting the high reversible Li+ - C=C bond interaction at L-PPH. This strategy, based on new insight into sp2 functional groups, is the first step toward a molecular understanding of the structure storage-capacity relationship in sp2 carbon-based polymer.
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Jul 2021
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B18-Core EXAFS
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Siyu
Zhao
,
Ruikuan
Xie
,
Liqun
Kang
,
Manni
Yang
,
Xingyu
He
,
Wenyao
Li
,
Ryan
Wang
,
Dan J. L.
Brett
,
Guanjie
He
,
Guoliang
Chai
,
Ivan P.
Parkin
Diamond Proposal Number(s):
[19850]
Open Access
Abstract: It remains a challenge to develop efficient electrocatalysts in neutral media for hydrogen evolution reaction (HER) due to the sluggish kinetics and switch of the rate determining step. Although metal phosphides are widely used HER catalysts, their structural stability is an issue due to oxidization, and the HER performance in neutral media requires improvement. Herein, a new material, i.e., grapevine‐shaped N‐doped iron phosphide on carbon nanotubes, as an efficient HER catalyst in neutral media is developed. The optimized catalyst shows an overpotential of 256 mV at a large current density of 65 mA cm−2, which is even 10 mV lower than that of the commercial 20% Pt/C catalyst. The excellent performance of the catalyst is further studied by combined computational and experimental techniques, which proves that the interaction between nitrogen and iron phosphides can provide more efficient active structures and stabilize the metal phosphide electrocatalysts for HER.
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May 2021
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B18-Core EXAFS
|
Diamond Proposal Number(s):
[10306, 19850]
Open Access
Abstract: Understanding the surface structure of bimetallic nanoparticles is crucial for heterogeneous catalysis. Although surface contraction has been established in monometallic systems, less is known for bimetallic systems, especially of nanoparticles. In this work, the bond length contraction on the surface of bimetallic nanoparticles is revealed by XAS in H2 at room temperature on dealloyed Pt–Sn nanoparticles, where most Sn atoms were oxidized and segregated to the surface when measured in air. The average Sn–Pt bond length is found to be ∼0.09 Å shorter than observed in the bulk. To ascertain the effect of the Sn location on the decrease of the average bond length, Pt–Sn samples with lower surface-to-bulk Sn ratios than the dealloyed Pt–Sn were studied. The structural information specifically from the surface was extracted from the averaged XAS results using an improved fitting model combining the data measured in H2 and in air. Two samples prepared so as to ensure the absence of Sn in the bulk were also studied in the same fashion. The bond length of surface Sn–Pt and the corresponding coordination number obtained in this study show a nearly linear correlation, the origin of which is discussed and attributed to the poor overlap between the Sn 5p orbitals and the available orbitals of the Pt surface atoms.
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May 2021
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