Ayca Senol Güngör

Last Name

Senol Güngör

First Name

Ayca

ORCID

0000-0001-8779-4920

Organisational unit

03895 - Wood, Vanessa / Wood, Vanessa

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Publications1 - 8 of 8

Energy storage ultra porous carbon blacks by high temperature oxidation
Kelesidis, Georgios A.; Rossi, Nicola; Senol Güngör, Ayca; et al. (2026)
Powder Technology
Ultra porous carbonaceous nanoparticles were prepared by judicious oxidation of various commercial carbon blacks (CBs) at high temperatures (1200 °C). X-ray diffraction, N₂ adsorption and microscopy analyses revealed that during such oxidation, O₂ diffuses through and reacts with CB, disordering its crystalline structure. The concurrent external and internal oxidation of CB results in tiny pores that greatly increase the specific surface area, SSA, from 240 up to 2185 ± 199 m²/g. This is about 150–200 % larger than the SSA of CB oxidized at low temperatures (450–550 °C), 50–100 % larger than the SSA of most porous CB commercially available and on par with that of commercial activated carbons (e.g. YP80). The potential of this ultra porous CB generated here for energy storage is showcased using electric double layer capacitors (EDLCs). The gravimetric capacitance of EDLCs using the above high SSA CB as active material is up to 60 % larger than those obtained from EDLCs based on YP80 or Ketjenblack at high scan rates (≥ 100 mV/s) and current densities of 0.02–5 A/g. The superior rate performance of these CBs is attributed to the high concentration of pores with a 2–8 nm radius formed largely by internal oxidation. Such pores cannot be produced at large concentrations by low temperature oxidation of CB that is used widely to enhance CB porosity. Hence, close control of the oxidation dynamics of CB can substantially increase supercapacitor performance.
Operando Scanning SAXS/WAXS Cell Design for Multiscale Analysis of All-Solid-State Battery Systems
von Mentlen, Jean-Marc; Fiedler, Magdalena; Neumayr, Klara; et al. (2025)
Batteries & Supercaps
Operando X-ray scattering techniques, particularly small- and wide-angle X-ray scattering (SAXS/WAXS), have been key for elucidating the physicochemical processes governing liquid-electrolyte batteries by providing real-time insights into phase transformations and nanoscale structural evolution. However, extending these methods to all-solid-state batteries has been experimentally challenging due to high X-ray absorption and nonideal operating pressures in transmission mode. Here a novel operando electrochemical cell design is presented that enables cross-sectional scanning SAXS/WAXS measurements, while maintaining the pressure necessary for solid-state operation. Applying this scanning SAXS/WAXS technique to all-solid-state lithium-sulfur batteries, it enables simultaneous mapping of the crystalline phase evolution and the nanoscale structural changes across distinct cell components during cycling. Spatially resolved WAXS revealed significant heterogeneity in the formation and distribution of Li₂S within the composite cathode. Simultaneously, WAXS captured an anisotropic lithiation mechanism in the Li-In anode, evidenced by the preferential disruption of In(110) planes and suggesting amorphous LiIn formation. Combined analysis of stable SAXS profiles and WAXS-derived Li₂S nanocrystallite sizes suggest that the sulfur conversion occurs within the nanopores of the templated carbon host. Control experiments using a liquid-electrolyte Li-S system validated the technique’s sensitivity to detect expected nanoscale changes, confirming the genuineness of the solid-state observations.
Intraparticular Heterogeneity Limits Capacity in Lithium-Sulfur Batteries With Carbonate Electrolyte
Senol Güngör, Ayca; von Mentlen, Jean-Marc; Garcia-Soriano, Francisco Javier; et al. (2026)
Battery Energy
The formation of a stable cathode-electrolyte interphase (CEI) is critical for the performance of lithium-sulfur (Li-S) batteries with carbonate-based electrolytes, as it suppresses parasitic polysulfide reactions and enables solid-state sulfur conversion. In nanoporous carbon hosts, the CEI together with nanopore confinement plays a key role in capacity retention and long-term cycling. Yet, its spatial formation, stability, and contribution to electrochemical performance remain poorly understood, partly due to challenges in characterization caused by beam and air sensitivity. Here, we employ cryogenic transmission electron microscopy (cryo-TEM) with electron energy loss spectroscopy and energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and electrochemical testing together with galvanostatic intermittent titration technique measurements to elucidate how carbon particle size affects CEI formation and electrochemical performance. We find that the CEI is not a uniform surface film but extends heterogeneously into the particle bulk. Mass transport during the first discharge dictates CEI development, and larger particles suffer from inactive regions due to the preferential CEI formation only in the outer regions of the particles. During extended cycling, charge transfer resistance at confined CEI/active material/carbon interfaces emerges as the dominant performance-limiting factor. These findings show that particle size controls CEI formation during initial discharge, offering guidance for designing carbon hosts from nano- to micrometer length scales in Li-S battery cathodes.
Fracture of hierarchical multi-layered bioinspired composites
Magrini, Tommaso; Senol Güngör, Ayca; Style, Robert; et al. (2022)
Journal of the Mechanics and Physics of Solids
Lightweight composites have revolutionized the sector of aircrafts and will continue to play a major role in future energy-efficient transportation systems. However, the design of composites featuring high strength and high fracture toughness remains challenging due to the usual trade-off between these properties in synthetic materials. Inspired by the strong and tough hierarchical architecture of mollusk shells, we create tough composites by combining soft polymer layers with alternating, nacre-like layers that are infiltrated with the same polymer. Here, we study the fracture behavior and the toughening mechanisms underlying the high crack growth resistance of these hierarchical composites. Polymer layers with different stiffness and yield strength were designed in order to evaluate the effect of plastic deformation and bridging of the polymer phase on the early and late stages of the fracture process. Controlled fracture experiments allowed us to visualize the interactions of a propagating crack with the hierarchical architecture and to quantify the resistance of the polymer layer against early-stage fracture. Our findings provide new insights into the interplay of multiscale toughening mechanisms in hierarchical bioinspired architectures and offer guidelines for the design and manufacturing of strong and tough lightweight composites.
Unraveling Multiphase Conversion Pathways in Lithium-Sulfur Batteries through Cryo Transmission Electron Microscopy and Machine Learning-Assisted Operando Neutron Scattering
von Mentlen, Jean-Marc; Senol Güngör, Ayca; Demuth, Thomas; et al. (2025)
ACS Nano
Understanding the complex physicochemical processes in conversion-type batteries requires investigations across multiple length scales. Here, we present a methodological approach to examine Li-S batteries on the nanoscale by combining cryogenic transmission electron microscopy (cryoTEM) with operando small-angle neutron scattering (SANS). CryoTEM revealed discharge products with a biphasic structure consisting of nanocrystalline Li2S within an amorphous Li2S x matrix. Data analysis of complementary operando SANS measurements was accelerated by a convolutional neural network trained to predict scattering curves based on plurigaussian random fields, enabling comprehensive parameter space exploration for model fitting. Our findings are in line with disproportionation-driven deposition of Li2S2 particles that agglomerate and partially reduce to Li2S via solid-state conversion. This challenges the conventional view of direct, stepwise electroreduction of polysulfides at the electrode-electrolyte interface. Overall, our multitechnique approach demonstrates the value of combining localized high-resolution imaging with time-resolved operando scattering measurements to understand complex electrochemical conversion pathways in next-generation energy storage systems.
Mineral composites: stay-in-place formwork for concrete using foam 3D printing
Bedarf, Patrick; Calvo-Barentin, Cristian; Martinez Schulte, Dinorah; et al. (2023)
Architecture, Structures and Construction
Optimizing the shape of concrete construction elements is significant in reducing their material consumption and totalweight while improving their functional performance. However, the resulting non-standard geometries are difficult andwasteful to fabricate with conventional formwork strategies. This paper presents the novel fabrication method of mineralfoam 3D printing (F3DP) of bespoke lost formwork for non-standard, material-efficient, lightweight concrete elements. Manyinnovative formwork studies have shown that stay-in-place formwork can help to reduce waste and material consumptionwhile adding functionality to building components. Foams are particularly suitable for this application because of their highstrength-to-weight ratio, thermal resistance, and good machinability. F3DP allows the waste-free production of geometricallycomplex formwork elements without long lead times and production-specific tooling. This paper presents the materialsystem and robotic F3DP setup with two experimental case studies: a perforated facade panel and an arched beam slab. Bothcases use concrete as structural material and strategically placed custom-printed foam elements. In this first preliminarystudy, concrete savings of up to 50% and weight reduction of more than 60% could be achieved. This is competitive withstandardized solutions such as hollow-core slabs but, in contrast, allows also for non-standard element geometries. Additionalfunctionality, such as programmed perforation, acoustic absorption, and thermal insulation, could be added through thestay-in-place formwork. Moreover, the challenges and future developments of F3DP for sustainable building processes arediscussed. Further studies are required to verify the findings. However, considering the urgent need for resource-efficient,low embodied-carbon solutions in the construction industry, this work is an important contribution to the next generation ofhigh-performance building components.
Robotic 3D Printing of Mineral Foam for a Lightweight Composite Facade Shading Panel
Bedarf, Patrick; Martinez Schulte, Dinorah; Senol Güngör, Ayca; et al. (2021)
CAADRIA ~ PROJECTIONS – Proceedings of the 26th International Conference of the Association for Computer-Aided Architectural Design
This paper presents the design and fabrication of a lightweight composite facade shading panel using 3D printing (3DP) of mineral foams. Albeit their important role in industrial construction practice as insulators and lightweight materials, only little research has been conducted to use foams in 3DP. However, the recent development of highly porous mineral foams that are very suitable for extrusion printing opens a new chapter for development of geometrically complex lightweight building components with efficient formwork-free additive manufacturing processes. The work documented in this paper was based on preliminary material and fabrication development of a larger research endeavor and systematically explored designs for small interlocking foam modules. Furthermore, the robotic 3D Printing setup and subsequent processing parameters were tested in detail. Through extensive prototyping, the design space of a final demonstrator shading panel was mapped and refined. The design and fabrication process is documented and shows the potential of the novel material system in combination with fiber-reinforced ultra-high performance concrete (UHPC). The resulting composite shading panel highlights the benefits of using mineral foam 3DP to fabricate freeform stay-in-place formwork for lightweight facade applications. Furthermore, this paper discusses the challenges and limitations encountered during the project and gives a conclusive outlook for future research.
Understanding Rate and Capacity Limitations in Li-S Batteries Based on Solid-State Sulfur Conversion in Confinement
Senol Güngör, Ayca; von Mentlen, Jean-Marc; Ruthes, Jean G.A.; et al. (2024)
ACS Applied Materials & Interfaces
Li-S batteries with an improved cycle life of over 1000 cycles have been achieved using cathodes of sulfur-infiltrated nanoporous carbon with carbonate-based electrolytes. In these cells, a protective cathode-electrolyte interphase (CEI) is formed, leading to solid-state conversion of S to Li2S in the nanopores. This prevents the dissolution of polysulfides and slows capacity fade. However, there is currently little understanding of what limits the capacity and rate performance of these Li-S batteries. Here, we aim to deepen our understanding of the capacity and rate limitation using a variety of structure-sensitive and electrochemical techniques, such as operando small-angle neutron scattering (SANS), operando X-ray diffraction (XRD), electrochemical impedance spectroscopy, and galvanostatic charge/discharge. Operando SANS and XRD data give direct evidence of CEI formation and solid-state sulfur conversion occurring inside the nanopores. Electrochemical measurements using two nanoporous carbons with different pore sizes suggest that charge transfer at the active material interfaces and the specific CEI/active material structure in the nanopores play the dominant role in defining capacity and rate performance. This work helps define strategies to increase the sulfur loading while maximizing sulfur usage, rate performance, and cycle life.

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Ayca Senol Güngör

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