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Instruments / Technical Area	Publication Details	Published	Actions
I15-1-X-ray Pair Distribution Function (XPDF)	Comparative microstructural analysis of non-graphitic carbons by wide-angle X-ray and neutron scattering Torben Pfaff , Felix M. Badaczewski , Marc Oliver Loeh , Alexandra Franz , Jens-Uwe Hoffmann , Manfred Reehuis , Wolfgang G. Zeier , Bernd M. Smarsly The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.9b03590 Diamond Proposal Number(s): [13560] Show Abstract ▼ Abstract: Non-graphitic carbons (NGCs) represent the most abundant class of \(sp^2\)-hybridized carbon materials (coal, char coal, activated carbon, etc.). These carbons consist of small graphene layer stacks possessing significant structural disorder both in the single graphene sheets and the stacking. In this study an advanced evaluation approach for the wide-angle neutron scattering (WANS) was developed, based on the method introduced by Ruland and Smarsly (2002). In particular, we elucidated if and how the enhanced WANS data quality and larger values of the modulus of the scattering vector \(s\)-range affect the accuracy and the values of the size and disorder parameters - being fitting parameters by themselves - in comparison to wide-angle x-ray scattering (WAXS), which is usually performed by laboratory equipment. We find a reasonable agreement for the parameters \(L_\mathrm{a}\) and \(L_\mathrm{c}\), i.e. the lateral dimension and stack height, within the error bars, while for the disorder parameters different results for WAXS and WANS were found, the origin of which is discussed. Thus, this study addresses the general issue of how reliably microstructural parameters can be determined from WAXS/WANS, by fitting simulated WAXS and WANS curves, which are quality-impaired by added Gaussion noise at different levels and cut-off at different \(s\)-values. From this analysis we estimated the minimal data quality required for a reliable NGC microstructural analysis based on WAXS/WANS. As an important finding, these simulations show that typical, standard WAXS laboratory setups are sufficient to provide reliable values for the most relevant structural parameters. Furthermore, pair-distribution function (PDF) analyses were performed on WAXS data obtained from a Synchrotron facility. Comparing PDF and WAXS/WANS fitting analysis thus suggests the presence of small highly ordered oligoaromatic domains embedded in the larger graphene sheets, questioning the classical view on the NGC microstructure.	Jul 2019
I15-Extreme Conditions	The critical role of the crystallite size in nanostructured Li4Ti5O12 anodes for lithium ion batteries Junpei Yue , Felix M. Badaczewski , Pascal Voepel , Thomas Leichtweiß , Doreen Mollenhauer , Wolfgang G. Zeier , Bernd M. Smarsly Acs Applied Materials & Interfaces DOI: 10.1021/acsami.8b05057 Diamond Proposal Number(s): [13560] Show Abstract ▼ Abstract: Lithium titanate Li4Ti5O12 (LTO) is regarded as a promising alternative to carbon-based anodes in lithium-ion batteries. Despite its stable structural framework, LTO exhibits disadvantages such as the sluggish lithium-ion diffusion and poor electronic conductivity. In order to modify the performance of LTO as an anode material, nanosizing constitutes a promising approach, and the impact is studied here by systematical experimental approach. Phase-pure polycrystalline LTO nanoparticles (NPs) with high crystallinity and crystallite sizes ranging from 4 to 12 nm are prepared by an optimized solvothermal protocol and characterized by several state-of-the-art technologies including HRTEM, XRD, PDF (pair distribution function) analysis, Raman spectroscopy and XPS. Through a wide array of electrochemical analyses, including charge/discharge profiles, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), a crystallite size of approx. 7 nm is identified as optimum particle size. Such NPs exhibit as good reversible capacity as the ones with larger crystallite sizes, but a more pronounced interfacial charge storage. By decreasing the crystallite size to about 4 nm the interfacial charge storage increases remarkably, however resulting in a loss of reversible capacity. An in-depth structural characterization using the PDF obtained from synchrotron XRD data indicates an enrichment in Ti for NPs with the small crystallite sizes, and this Ti-rich structure enables a higher Li storage. The electrochemical characterization confirms this result and furthermore points to a plausible reason why a higher Li-storage in very small nanoparticles (4 nm) results in a loss in the reversible capacity.	Jun 2018

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