In-beam activation analysis facility at MLZ, Garching

Révay, Zsolt; Kudějová, P.; Kleszcz, Krzysztof; Söllradl, S.; Genreith, Christoph

doi:10.1016/j.nima.2015.07.063

Cited by 48 publications

(21 citation statements)

References 21 publications

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“…33 The beamline provides a collimated cold neutron beam with an area of 12.6 mm 2 and a flux of 1.35 × 10 9 cm −2 s −1 which can be reduced by different attenuators (5.9%, 16%, and 47%) to mitigate pile-up effects at count rates above 10 3 s −1 . 35 The 14 mm diameter SiG electrodes were placed in the NDP vacuum chamber with the coating facing the incoming beam at an angle of 45 • . The N4DP setup at the PGAA facility is described in more detail by Trunk et al 33 High-resolution cross-sectional SEM images.-The morphology of the SiG electrodes in their pristine state and after different numbers of cycles was investigated by high-resolution cross-sectional scanning electron microscopy (SEM).…”

Section: Methodsmentioning

confidence: 99%

Quantifying the Distribution of Electrolyte Decomposition Products in Silicon-Graphite Electrodes by Neutron Depth Profiling

Wetjen

Trunk

Werner

et al. 2018

J. Electrochem. Soc.

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Silicon-based anodes for lithium-ion batteries exhibit severe volumetric changes of the active material particles during (de-)lithiation, resulting in continuously occurring side reactions at the silicon/electrolyte interface over extended charge/discharge cycling. The thus formed and accumulating electrolyte decomposition products lead to a growth of the solid-electrolyte-interphase (SEI) on the silicon particles. This results not only in an ongoing loss of electrolyte but also in a significant swelling and impedance increase of silicon-based anodes which significantly compromises their cycle-life. In the present study, neutron depth profiling (NDP) is used post mortem as a non-destructive, highly lithium-sensitive technique to (i) quantify the amount of lithium-containing electrolyte decomposition products in silicon-graphite (SiG) electrodes (35 wt% silicon, areal capacity ∼1.7 mAh cm −2), (ii) monitor their distribution across the SiG electrode thickness, and (iii) determine the active material utilization across the electrode over 140 cycles. Hence, SiG negative electrodes are aged and characterized by means of galvanostatic cycling in SiG//LiFePO 4 pseudofull cells, using a capacitively oversized positive electrode and an electrolyte mixture consisting of 1 M LiPF 6 in EC:EMC with 5 wt% FEC. High-resolution cross-sectional SEM images and post-mortem characterization of the SiG electrodes with respect to changes in electrode mass thickness complement the analysis.

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Section: Methodsmentioning

confidence: 99%

Quantifying the Distribution of Electrolyte Decomposition Products in Silicon-Graphite Electrodes by Neutron Depth Profiling

Wetjen

Trunk

Werner

et al. 2018

J. Electrochem. Soc.

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“…The three investigated Nb samples were prepared from the same single-crystal commercially obtained from MaTeck 25 . The concentration of impurities of the crystal has been measured by neutron activation and prompt gamma activation analysis 26 . Hydrogen, tungsten and tantalum have been tracked as main detectable impurities with a concentration between 200-350 ppm each 27 .…”

Section: Experimental Methodsmentioning

confidence: 99%

Domain formation in the type-II/1 superconductor niobium: Interplay of pinning, geometry, and attractive vortex-vortex interaction

et al. 2017

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Vortex attraction which can cause a bundling of vortices has been observed in a multitude of type-II superconductors. While its underlying mechanisms have been extensively studied, the morphology of the emerging vortex superstructure has only been rarely considered. Here, we present a comprehensive experimental study on the type-II/1 superconductor niobium which focuses on the transformation of its homogeneous vortex lattice into an inhomogeneous domain structure at the onset of vortex attraction. By means of small-angle neutron scattering, ultra-small-angle neutron scattering, and neutron grating interferometry, the vortex lattice, the micrometer-scale vortex domain structure as well as its distribution could be investigated. In particular, we focus on the transformation of the vortex lattice at the transition to the intermediate mixed state which is characterized by vortex attraction. We have found that the phase separation of the vortex lattice into an irregular domain structure takes place via a process showing strong similarity to spinodal decomposition. While pinning disorders the domain morphology, the characteristic length scale of the domain structure is governed by an interplay of field distortion energy and domain surface tension. Finally, geometric barriers in the disc-shaped samples provoke an inhomogeneous distribution of domains on the macroscopic scale.

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“…The prompt gamma rays were detected with a high-purity germanium (HPGe) detector with a relative efficiency of 60% surrounded by a bismuth germanate scintillator annulus as a Compton suppressor. 33 The spectra were collected using an ORTEC Dspec-50 spectrometer. The gamma spectra were evaluated using the Hypermet-PC program, and the list of peak energies and areas were statistically analyzed, then fit to elemental data in the spectroscopy database, as described by Z. Révay.…”

Section: Methodsmentioning

confidence: 99%

Gas Evolution and Capacity Fading in LiFe_xMn_1-xPO₄/Graphite Cells Studied by Neutron Imaging and Neutron Induced Prompt Gamma Activation Analysis

Starke

Seidlmayer

Schulz

et al. 2017

J. Electrochem. Soc.

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The gas evolution in LFP/graphite and LFMP/graphite cells during the formation has been analyzed via neutron imaging (NI). The results show that in LFMP/graphite cells approximately 30% more gas is generated in comparison to LFP/graphite and stronger gas evolution is associated with the presence of Mn. For the LFP/graphite cell two different linear phases in gas evolution rate can be detected while LFMP/graphite cells reveal an additional phase. In both full-cells a distinct relation between gas evolution and electrode potentials has been determined. Additional neutron induced Prompt Gamma Activation Analysis (PGAA) measurements were carried out in order to correlate long-term Mn dissolution and capacity retention. Long-term cycling showed higher capacity retention for the LFMP/graphite cells. The results of PGAA prove that Mn dissolution decreases rapidly with increased cycle number and the Mn dissolution rate of LFMP is far below values observed for oxide-type cathode materials. Long-term cycling showed that the negative effects of higher irreversible capacity loss in the formation step and more gas evolution of LFMP/graphite cells in comparison to LFP/graphite cells is compensated after several cycles due to higher capacity retention. Due to their high energy density and operating voltage lithiumion batteries are a key technology for mobile applications such as communication devices and electric vehicles.1-3 But also stationary energy storage systems are increasingly developed under usage of lithium-ion technology. Those stationary storage systems range from small (e. g. home storage for photovoltaic plants) to large scale applications (grid stabilization). [4][5][6] Especially in cases of high capital expenditures, consumers and operators expect a long battery lifetime in terms of capacity and charge and discharge characteristics.Applications like home energy storage require high operational safety standards. These requirements are met by the cathode active material LiFePO 4 (LFP), which has first been described in 1997. Phospho-olivines such as LFP provide good operational characteristics in terms of thermal runaways and are furthermore environmentally friendly and cost-efficient. The dissolution of Mn from LFMP as such has recently been investigated and a strong correlation between dissolved Mn and traces of H 2 O contamination in the electrolyte has been stated. It has also been found that in case of LFMP there is no selective dissolution of Mn since Fe is dissolved as well and the Mn/Fe ratio in the electrolyte and the active material is equal. 18Another study has shown that transition metal dissolution also occurs in oxide-type active materials such as layered Nickel-ManganeseCobalt oxide based active materials (NMC). 19 In case of NMC all z E-mail: benjamin.starke@haw-landshut.de present transition metals Ni, Mn and Co dissolve in the electrolyte and migrate to the anodic graphite. But while Ni and Co remain in the oxidation state +II, Mn is reduced to Mn 0 and subsequently reoxidized to Mn 2+ under co...

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In-beam activation analysis facility at MLZ, Garching

Cited by 48 publications

References 21 publications

Quantifying the Distribution of Electrolyte Decomposition Products in Silicon-Graphite Electrodes by Neutron Depth Profiling

Quantifying the Distribution of Electrolyte Decomposition Products in Silicon-Graphite Electrodes by Neutron Depth Profiling

Domain formation in the type-II/1 superconductor niobium: Interplay of pinning, geometry, and attractive vortex-vortex interaction

Gas Evolution and Capacity Fading in LiFe_xMn_1-xPO₄/Graphite Cells Studied by Neutron Imaging and Neutron Induced Prompt Gamma Activation Analysis

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In-beam activation analysis facility at MLZ, Garching

Cited by 48 publications

References 21 publications

Quantifying the Distribution of Electrolyte Decomposition Products in Silicon-Graphite Electrodes by Neutron Depth Profiling

Quantifying the Distribution of Electrolyte Decomposition Products in Silicon-Graphite Electrodes by Neutron Depth Profiling

Domain formation in the type-II/1 superconductor niobium: Interplay of pinning, geometry, and attractive vortex-vortex interaction

Gas Evolution and Capacity Fading in LiFexMn1-xPO4/Graphite Cells Studied by Neutron Imaging and Neutron Induced Prompt Gamma Activation Analysis

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Gas Evolution and Capacity Fading in LiFe_xMn_1-xPO₄/Graphite Cells Studied by Neutron Imaging and Neutron Induced Prompt Gamma Activation Analysis