MLZ Conference 2024: Neutrons for Energy Storage

4 Jun 2024, 09:00 → 7 Jun 2024, 14:15 Europe/Berlin

Schloss Fürstenried (Munich)

In order to submit an abstract for the conference, please click on "Call for Abstracts". In order to register for the conference, please visit the registration website.

Storage and effective usage of renewable energy will be one of the major challenges our society will face in 21th century. This century will witness a major transformation in how energy is acquired, stored, and utilized globally. Neutron scattering contributes significantly to the advancement of energy storage technologies by providing detailed insights into the structural and dynamic properties of materials. This information is instrumental in designing and improving materials for more efficient, durable, and sustainable energy storage solutions.

Characterization of energy materials: studies of structural and dynamic properties of materials at the atomic and molecular levels, which is crucial for understanding the behavior of materials used in energy storage devices such as batteries and fuel cells.

Battery Research: neutron scattering provides insights into the structural changes occuring within electrode materials during charging and discharging cycles, variously stabilized aging states and different cell designs, thus helping researchers design more efficient and durable battery materials.

Hydrogen Storage: For hydrogen storage materials, neutron scattering is valuable for studying the interactions between hydrogen and the storage material, creating a necessary base for designing materials that can store and release hydrogen more effectively, contributing to advancements in hydrogen-based energy storage.

Understanding Diffusion Processes: Neutron scattering is particularly useful for studying diffusion processes in energy materials. In energy storage, diffusion of ions or molecules within electrodes or electrolytes is a critical factor influencing the performance of batteries and other storage systems.

In Situ and Operando Studies: Neutron scattering techniques allow for in situ studies, meaning researchers can observe and analyze materials under actual operating conditions. This is essential for gaining insights into the dynamic behavior of materials during energy storage processes.

Catalyst Research: Neutron scattering helps in understanding the behavior of catalysts used in various energy conversion and storage systems. This knowledge is crucial for optimizing catalyst performance and improving the efficiency of processes like fuel cells.

The MLZ Conference Neutrons for Energy Storage is meant to be a forum for experts from research and industry and aims to enhance and adapt the potential of neutron scattering methods (in combination with complementary tools) for the characterization and the development of materials and solutions for new generation energy storage. Series of presentations (in forms of talks and posters) will be presented by renowned international researchers in the field to demonstrate state-of-the-art methods and their applications.

Tuesday 4 June

Day1: Registration

1 Welcome & Organisational details

2 Welcome & Organisational details

12:00 Lunch break

3 Exploration and optimization on the structural properties of cathode materials for high-performance lithium and sodium-ion batteries

Although the research on the cathode materials for lithium-ion and sodium-ion batteries has attracted extensive interest, the deep understanding on their structural properties and the insight into their structural evolution are still lack. By taking advantages of sensitive, penetrative and nondestructive properties of neutrons, we adopted ex-situ and in-operando neutron diffraction techniques to explore the structural characteristics of cathode materials of lithium and sodium-ion batteries, especially the structural evolution of cathodes during cycling in real time. It is revealed that structural defects formed in layered cathodes and they varied upon charging and discharging. Moreover, the visualization of the ion migration pathway in cathode indicated that ions diffused via different hopping paths at different states of charge. Based on the relationship between structural and electrochemical properties of cathode materials, we modified and optimized the performances of cathodes by adopting different synthesis procedures, which are of scientific and practical significance. Besides of the research on cathode materials, the construction progress of Peking University high-resolution neutron powder diffractometer at China Spallation Neutron Source will also be presented.

Speaker: Yinguo Xiao (Peking University)

4 Operando observation of local lithium crystallites inside the polymer electrolyte in lithium metal batteries by nanofocus wide-angle X-ray scattering

Single-ion conducting polymers are a promising candidate as solid-state electrolyte in lithium metal batteries due to a theoretical transference number of one, which is accompanied by the suppression of lithium dendrite growth. This can extend the cycle life and improve the overall safety of lithium metal batteries. However, the practical usage is still under debate, mainly due to low ionic conductivity and hence poor cell performance. Furthermore, dendritic growth of lithium has also been reported in single-ion conducting polymer based cells. Here, we study operando the local formation process of lithium crystallites inside the polymer electrolyte in their early stage with symmetric lithium cells by nanofocus wide-angle X-ray scattering (nWAXS). With this technique, we can spatially resolve the crystalline structure of the cell on a nanoscale by scanning an area of interest of the polymer during the battery operation. With such approach, we can identify rare events, which will help to understand the failure mechanisms in these battery types.

Speaker: Fabian Alexander Christian Apfelbeck (Technical University of Munich, TUM School of Natural Sciences, Department of Physics, Chair for Functional Materials)

5 A new model for the structure of hard carbons used as anodes in sodium-ion batteries

Cotton is one of the main constituents of textile residues (> 33%) and can be used as raw material in the new value chain for sodium-ion battery (SIB) anodes, providing a double impact on the ecologic transition: a residual material is recovered for the circular economy and the further growth of renewable energies is promoted. Besides, SIBs will play a substantial role for the future electrochemical energy storage system as they are supposed to fill the gap left behind by the availability issues of lithium and other metals and it is the technology of choice for large-scale stationary application. However, SIBs still require a significant development boost for the electrodes, both anodes and cathodes as well as the complete cell configuration. Lithium technology involving a graphite support cannot be used due to different atom properties, mainly the atom size (as Na+ is larger than Li+). Hard carbon-based materials are promising materials to overcome this issue due to their safety, economic feasibility, high capacity, and good stability. One route to hard carbons involves hydrothermal carbonization (HTC) followed by a thermal post-treatment, although this valorisation route involves many knowledge gaps.
It is known that the crucial transformation of hydrochar into hard carbon proceeds in the range of 500 to 900 °C, forming graphitic domains and a porous structure. Hard carbons (from other sources) have been studied for their application as electrodes, with the focus on the sodium storage mechanism as well as the structure-function correlation. Sodium storage may be related to: (1) adsorption/chemisorptions at defect sites/heteroatoms of graphitic planes; (2) intercalation between two graphitic planes with suitable interlayer distance; and (3) nanopore filling of small internal closed pores (up to 1 or 2 nm).
Herein, a new model for the structure of hard carbons derived from hydrochar is presented based on the transformation visualized in the van-Krevelen diagram. The transformation of cotton into carbon materials (elimination of the oxygen and hydrogen content) is governed by dehydration and condensation reactions. It is proposed that the intermediate is a linear polymer of aromatic nature that is enrolled like a wool ball, as inferred from FESEM images. With further thermal treatment graphene domains should grow; however, the tridimensional structure is already fixed and, therefore, the carbon material is not transformed into graphite which is the condition to be classified as hard carbon.
The new structure can be regarded as a fusion of the house of card model and the curved planes proposed for the structure of hard carbons before. It allows to identify different types of pores in the material: on one hand, flat interplanar spaces with distances superior of the one of graphite; on the other hand, conical ones with oxygen functionalities resembling to defect sites in graphene. The proposed structure is in accordance with XPS and Raman analysis; however, no clear proofs can be achieved with these techniques.
Stronger evidences for the characterization of the porous structure, especially for closed pores and graphitic domains should be obtained in scheduled experiments (ReMade program), namely by X-ray diffraction (structure) and small angle X-ray and neutron scattering (SAXS and SANS, pores). SANS can be carried out on as-prepared, empty samples ("dry" samples) and on samples with deuterated toluene adsorbed ("wet" samples). Measurements on “dry” samples will provide the total scattering from all porosity, including both open and closed pores. SANS on “wet” samples, when filling the open pores with the appropriated amount of deuterated toluene to match the scattering of the carbon matrix, will eliminate the contribution of the open porosity providing information about the remaining, inaccessible, closed pores. The full characterization of different sets of samples and further correlation with electrochemical measurements will allow the selection of the best preparation method for anode materials and will contribute to a better understanding of the basics for an optimized electrochemical performance, especially for the sodium storage mechanism.
It is the aim of this contribution to devise and apply neutron scattering methods to further explore the structure of hydrochar-derived hard carbons and, thereby, to optimize their properties for sodium storage in rechargeable batteries.

Speaker: Michael Renz (ITQ)

6 Lithium Distribution in 18650-type Li-ion batteries over its lifetime

During the electrochemical cycling of lithium-ion batteries, ionic and electron transfer occur simultaneously, i.e., lithium ions and electrons are exchanged between positive and negative electrodes. Besides the material's properties, such an exchange is influenced by cell characteristics, such as electrode dimensions and geometry, current density, temperature, pressure, reaction rate, etc. In cell designs adopting high volumetric and gravimetric densities, these parameters are neither uniformly distributed nor static in general and, therefore, serve as stabilizing factors of heterogeneous state in Li-ion batteries, which is typically reflected in the non-uniform distribution of the intercalated lithium in the electrodes [1, 2].
Previous studies revealed the modification of the lithium-ion distribution in the graphite anode of 18650-type lithium-ion batteries upon increasing cell aging [3]. The current research investigates this effect in detail on quasi-identical commercial cells with different stabilized aging states by applying spatially resolved neutron powder diffraction. Details of lithium distribution over the lifetime of a commercial 18650-type lithium-ion battery were determined.

1. Senyshyn, A., et al., Homogeneity of lithium distribution in cylinder-type Li-ion batteries. Scientific Reports, 2015. 5(1): p. 18380.
2. Petz, D., et al., Heterogeneity of Graphite Lithiation in State-of-the-Art Cylinder-Type Li-Ion Cells. Batteries & Supercaps, 2021. 4(2): p. 327-335.
3. Mühlbauer, M.J., et al., Inhomogeneous distribution of lithium and electrolyte in aged Li-ion cylindrical cells. Journal of Power Sources, 2020. 475: p. 228690.

Speaker: Dominik Petz

14:40 Coffee break

7 Exploiting neutron techniques to reveal the hidden secrets of batteries

Nowadays, increasingly sophisticated methods are applied for more and more complex battery materials in order to gain a better understanding of the complex processes in electrochemistry. A particular challenge here is to investigate electrochemically relevant processes that occur on different length and/or time scales in such a way that these processes are not influenced by the method. One often looks for probes that can measure a sufficient volume of the sample non-destructively and at the same time are sensitive to the important small charge carriers.
Such challenges are often solved with neutrons because they are ideal for these tasks. Neutrons have a relatively high sensitivity to light chemical elements such as lithium, sodium, hydrogen and they can easily distinguish neighboring elements of the periodic table. The large cross section of the incident neutron beam together with the large penetration depth of neutrons into materials open up unique measurements, including the examination of entire large batteries in the beam.
This contribution gives an overview of how dedicated neutron techniques are applied for specific questions on a wide variety of length and time scales [1]. The main applied neutron method is neutron diffraction (ND) to understand at the atomic level changes such as phase transformations or the intercalation processes. Often measurements are carried out operando, particularly on complete cylindrical cells [2]. The neutron depth profiling method (NDP) is suitable for lithium distribution determination on the surface of electrodes [3]. Neutron imaging (NI) techniques, including neutron radiography or neutron tomography, is an ideal tool for studying and monitoring the wetting process during electrolyte filling of prismatic hard shell cells or pouch bag cells on the macroscopic length scale [4]. Further methods as quasi-elastic neutron scattering (QENS), small-angle neutron scattering (SANS), prompt gamma activation analysis (PGAA) or positron methods are suitable tools.

References:
[1] R. Gilles,
How neutrons facilitate research into gas turbines and batteries from development to engineering applications, Journal of Surface Investigations: X-Ray, Synchrotron and Neutron Techniques, (2020), 14, Suppl. 1, S69.
[2] V. Zinth, C. von Lüders, J. Wilhelm, S.V. Erhard, M. Hofmann, S. Seidlmayer, J. Rebelo-Kornmeier, W. Gan, A. Jossen, R. Gilles
Inhomogeneity and relaxation phenomena in the graphite anode of a lithium ion battery probed by in situ neutron diffraction, Journal of Power Sources (2017), 361, 54.
[3] M. Trunk, L. Werner, R. Gernhäuser, B. Märkisch, Z. Revay, H. A. Gasteiger, M. Wetjen, R. Gilles,
Materials science application of neutron depth profiling at the Prompt Gamma-ray Activation Analysis (PGAA) of Heinz Maier-Leibnitz Zentrum, Materials Characterization (2018), 146, 127.
[4] F.J. Günter, J. Keilhofer, C. Rauch, S. Rössler, M. Schulz, W. Braunwarth, R. Gilles, R. Daub,G. Reinhart,
Influence of pressure and temperature on the electrolyte filling of lithium-ion cells: Experiment, model, method, Journal of Power Sources (2022), 517, 230668.

Speaker: Ralph Gilles

8 Coupling Neutron Tomography with X-Ray Absorption and Scattering Tomography to Resolve Damage in Lithium Ion Batteries

Neutron based techniques are uniquely interesting to study Lithium-Ion Batteries (LIBs). The direct sensitivity of neutrons towards lithium nuclei offer a plethora of opportunities to investigate the complex processes interacting to allow these devices to store electrical energy. Neutron computed tomography (NCT) in particular is interesting, as it allows one to directly map the distribution of lithium inside cells.

Thanks to the non-destructive nature of neutron methods, it further becomes possible to perform complementary techniques as well. By coupling NCT with X-Ray based Computed Tomography (NXCT) it becomes possible to segment different components by leveraging differences in the attenuation coefficients for elements with respect to neutrons and X-Rays. Further, diffraction/scattering based techniques can be employed as well, which offer a view into the processes occurring on the atomic/nano-scale. By utilising Small- and Wide-Angle X-Ray Scattering Computed Tomography (SWAXS-CT), which is capable of spatially resolving scattering properties in two dimensions, another source of insights can be gathered to aid in the study of LIBs.

In this work we measure aged industry-grade silicon-based LIBs with NXCT to investigate where lithium is located in degraded cells. This is combined with operando SWAXS-CT measurements performed on the same cell to map the crystallographic properties and match them with features observed in NXCT. Combining these techniques allowed us to probe peculiar zones inside the cells where the current collector has been massively deformed. We identify and characterise the resulting changes to the lithiation behaviour through localised operando scattering analysis and match the observations with insights gained from the neutron-based analysis. This correlated methodology ultimately enabled us to resolve the origins of these defects and offers valuable insights for manufacturers (1).

(1) E. Lübke et al, in review

Speaker: Erik Lübke (Institut Laue-Langevin (ILL))

9 Applications of Neutron diffraction on cathode materials for Na-ion and Li-ion batteries

High resolution neutron powder diffractometer (HRPD) and High intensity neutron powder diffractometer (HIPD) at China Advanced Research reactor have been opened to users around the world since 2023. Up to now, many experiments in the field of Na-ion and Li-ion batteries have been performed. Here we will introduce the progress of two neutron powder diffractometers and share several meaningful research results. Firstly, we investigated the effect of multiple elements on Na/vacancy ordering, Transition metal (TM) ordering in layered oxide NaxTMO2, thereby explained the performance enhancement mechanism in the view of microstructure. In addition, our users proposed an innovative approach to address structural/chemo-mechanical degradation of LiCoO2 via the integration of chemical short-range disorder (CSRD) into LiCoO2 cathodes. Owing to the opposite sign of neutron-scattering lengths of Li and Co, -1.9 and 2.49 fm, respectively, the Rietveld refinement of NPD data indicated the presence of Li/Co mixing in the crystal structure, which involves the localized distribution of elements within a lattice over spatial dimensions, spanning a few nearest neighbor spacings. Therefore, the rationally designed LiCoO2 cathode with CSRD showed increased cycle life and rate capability compared to conventional cathodes.

Speaker: Dr Xiaobai Ma (China Institute of Atomic Energy)

10 Investigating Phase Equilibrium during Synthesis of LNMO via Comprehensive Neutron and X-ray Diffraction Study

$LiNi_{0.5}Mn_{1.5}O_4$ (LNMO) emerges as a highly promising material for positive electrodes in Li-ion batteries (LIBs), owing to its elevated operating voltage (4.8 V vs $Li^+/Li$) attributed to the $Ni^{4+}/Ni^{3+}/Ni^{2+}$ redox couples, crucial for development LIBs$^1$.
LNMO crystallizes with different extents of $Ni/Mn$ ordering; in the fully ordered phase ($P4_332$ space group), Ni and Mn ions occupy $4a$ and $12d$ octahedral sites respectively, whereas in the fully disordered phase ($Fd\bar{3}m$ space group), they share the same $16d$ site. Elevated temperatures (>750°C), required to obtain the disordered phase, induce oxygen loss, forming rock salt-based impurities and reducing $Mn(IV)$ to $Mn(III)$.
The degree of $Ni/Mn$ ordering significantly impacts LNMO's performance; disordered LNMO demonstrates enhanced performance at high C-rates and improved cycling stability compared to ordered LNMO$^{2,3}$. Additionally, disordered Mn-rich LNMO ($Ni/Mn = 22/78$) can be prepared without oxygen deficiency, leading to superior electrochemical performance$^4$. This unexpected finding motivates a systematic exploration of the Ni/Mn ratio's effect on LNMO's phase equilibrium and electrochemical behavior. In this investigation, $ex\:situ$ and $in\:situ$ Neutron and Synchrotron X-ray powder diffraction under air and oxygen atmospheres were conducted to monitor the $Ni/Mn$ ordering process during LNMO synthesis with varying initial $Ni/Mn$ ratios (25/75 for stoichiometric LNMO and 23/77 for Mn-rich LNMO).
Our results 1 demonstrate that oxygen release disrupts the $Ni/Mn$ ordering process for both $Ni/Mn$ ratios, indicating that fully disordered LNMO cannot be achieved without rock salt-based impurities. Moreover, our data suggest that the extent of $Ni/Mn$ ordering in LNMO is governed primarily by the concentration of $Mn(III)$ in LNMO's crystal structure, which can be controlled by adjusting the $Ni/Mn$ ratio and partial oxygen pressure during synthesis. In addition, Mn-rich LNMO samples exhibit superior discharge capacity, C-rate capability, and capacity retention, indicating an important role of Mn excess in enhancing the electrochemical performance of LNMO$^5$.

References
(1) Liang, G.; K. Peterson, V.; Wai See, K.; Guo, Z.; Kong Pang, W. Developing High-Voltage Spinel $LiNi_{0.5}Mn_{1.5}O_4$ Cathodes for High-Energy-Density Lithium-Ion Batteries: Current Achievements and Future Prospects. J. Mater. Chem. A 2020, 8 (31), 15373–15398. https://doi.org/10.1039/D0TA02812F.
(2) Casas-Cabanas, M.; Kim, C.; Rodríguez-Carvajal, J.; Cabana, J. Atomic Defects during Ordering Transitions in $LiNi_{0.5}Mn_{1.5}O_4$ and Their Relationship with Electrochemical Properties. J. Mater. Chem. A 2016, 4 (21), 8255–8262. https://doi.org/10.1039/C6TA00424E.
(3) Kim, J.-H.; Huq, A.; Chi, M.; Pieczonka, N. P. W.; Lee, E.; Bridges, C. A.; Tessema, M. M.; Manthiram, A.; Persson, K. A.; Powell, B. R. Integrated Nano-Domains of Disordered and Ordered Spinel Phases in $LiNi_{0.5}Mn_{1.5}O_4$ for Li-Ion Batteries. Chem. Mater. 2014, 26 (15), 4377–4386. https://doi.org/10.1021/cm501203r.
(4) Aktekin, B.; Valvo, M.; Smith, R. I.; Sørby, M. H.; Lodi Marzano, F.; Zipprich, W.; Brandell, D.; Edström, K.; Brant, W. R. Cation Ordering and Oxygen Release in $LiNi_{0.5-x}Mn_{1.5+x}O_{4-y}$ (LNMO): In Situ Neutron Diffraction and Performance in Li Ion Full Cells. ACS Appl. Energy Mater. 2019, 2 (5), 3323–3335. https://doi.org/10.1021/acsaem.8b02217.
(5) Tertov, I.; Kwak, H.; Cabelguen, P-E.; Kumakura, S.; Suard, E.; Fauth, F.; Hansen, T.; Croguennec L.; Masquelier, C. In preparation.

Speaker: Ilia TERTOV (Institut Laue Langevin)

16:50 Coffee break

11 Quantification of reactions on absolute scales via operando neutron and X-ray methods to understand energy storage systems

Quantitative insight into reactions as well as into structural (physical and electronic) and morphological properties on an absolute scale and under reactions conditions is imperative towards understanding atomic- to meso-scale mechanisms and processes in energy storage systems. Interpreted in the context of device performance, this knowledge can be used for rational design of and new concepts for improved materials and processes.

In the first part of contribution, the particular usefulness of operando neutron and X-ray methods for the quantification of reactions on absolute scales will be discussed conceptually. It will be rationalized how the respective information can be utilized to understand energy-relevant systems, using the examples of electrochemical energy storage, electrochemical desalination, and thermocatalysis. In the second part, specific science examples will be discussed in which a variety of different X-ray and neutron methods were employed. These include the surface electrochemistry of model electrodes, the degradation mechanism during extreme fast charging of Li-ion batteries, and the dynamics and transport in electrolytes.

The final part of the talk will be devoted to future opportunities to utilize neutrons (in combination with and inspired by X-rays) to study dynamic processes in energy storage systems.

Speaker: Hans-Georg Steinrück (FZ Jülich, Institute for a Sustainable Hydrogen Economy (INW) / RWTH Aachen)

12 Operando Investigation of NMC622/Argyrodite based All-Solid-State Battery using Neutron Diffraction

Operando Investigation of NMC622/Argyrodite based All-Solid-State Battery using Neutron Diffraction

All-solid-state batteries (ASSBs) are gaining increased attention due to their potential for enhanced safety and higher energy density compared to conventional metal-ion batteries. They are particularly suited for industrial applications like oil wells, where battery operation at high temperatures is necessary$^{1}$. A deep understanding of the assembly and electrochemical cycling mechanisms of ASSBs is still needed to assess reactivity and structural evolution of the active materials. The positive electrode material, LiNi0.6Mn0.2Co0.2O2 (NMC622), currently utilized in commercial Li-ion batteries for its balance of high energy density, safety, and durability, is being considered for ASSBs$^{2}$. Additionally, mixed-halide argyrodite solid electrolytes are recognized for their high ionic conductivity and softness, despite their relatively high chemical instability and reactivity.

We investigated operando the solid-state battery system comprising of NMC622 and a mixed-halide solid electrolyte Li$_{6-x}$PS$_{5-x}$BrCl$_{x}$ synthesized in-house$^{3}$ which possesses a RT ionic conductivity of 10$^{-2}$ S.cm$^{-1}$ thus allowing to build very thick ASSBs. Due to the high penetration power of the neutron beam and its sensitivity to light elements such as Lithium$^{4}$, neutron diffraction (ND) is the method of choice. By combining ex situ and operando ND techniques, we analysed the reactivity at the solid-solid interfaces and thus the stability of each component (NMC622, Argyrodite), and more generally all the mechanisms involved upon electrochemical operation, at room temperature and upon increasing temperature (100$^{\circ}$C)$^{5}$.

Operando ND measurement of ASSB

References

1. R. R. Kohlmeyer, et al. "Pushing the thermal limits of Li-ion batteries." Nano Energy 64, (2019)
2. O. Dolotko, et al. "Understanding structural changes in NMC Li-ion cells by in situ neutron diffraction." J. Power Sources 255, 197-203 (2014)
3. J. Auvergniot, C. Masquelier, V. Viallet, D. Shanbhag, World Patent WO2023/247531A1 (2023)M.
4. Bianchini, et al., "A new null matrix electrochemical cell for Rietveld refinements of in-situ or operando neutron powder diffraction data." J. Electrochem. Soc. , 160(11), A2176 (2013)
5. MG. Boebinger, et al. "Understanding transformations in battery materials using in situ and operando experiments: progress and outlook." ACS Energy Letters, 5, 335-345 (2020)

Speaker: Sreelakshmi ANIL KUMAR (ILL Grenoble)

18:20 Dinner

Wednesday 5 June

13 Probing Stuctures, Dynamics and Reactions in Electrolytes and Energy Systems by complementary neutron scattering techniques across extended scales and conditions

Energy conversion and storage devices as proton-exchange membrane fuel cells (PEMFC) or Li-ion batteries (LIB) are complex electrochemical cells composed of an electrolyte sandwiched by two electrodes. The layered geometry allows ion fluxes through the electrolyte from one electrode to another. Ions also diffuse inside the porous structures of conductive layers (e.g. catalytic layers in PEMFC, positive/negative mcirostructured electrodes in LIB) where electrochemical reactions take place (oxygen reduction in a fuel cell and conversion/intercalation reaction in a LIB cathode, typically). While the fuel cell converts the chemical energy into electrical current by using a continuous flux of reactants, the battery stores the chemical energy in the host structures, with ions shuttling back and fort during charges/discharges cycles along the battery lifetime. In both energy devices, understanding the basic working and degradation mechanisms across an extended range of lentgh and time scales is key to optimize performance and durability.
Neutron techniques are beneficial to non-destructively study the bulk properties of active material and/or individual components, as well as their interfaces, and also monitor the dynamics in the operating/cycling systems. The so-called operando experiments are enabling to measure a quantity of interest and its transformations/evolutions during PEMFC or LIB function – for instance, host material structures & nanostructures, species states and distribution, etc [1]. These quantities can be measured in representative conditions using custom operando cells, or even commercial cells in some cases, in fresh and also in aged systems, hence enabling to understand the origins of performance loss.
In this talk we will emphasize recent developments of neutron imaging and microbeam small angle scattering methods that are employed, including correlatively, to study water management in PEMFC [2,3] and lithiation heterogeneities in LIBs [4]. We will also show the advances in multi-resolution QENS to uncover the characteristics of ion mobility in polymer systems capable to conduct protons, hydroxides, hydrides or lithium ions [5,6].
[1] D. Atkins,et al. Accelerating Battery Characterization Using Neutron and Synchrotron Techniques: Toward a Multi-Modal and Multi-Scale Standardized Experimental Workflow. Advanced Energy Materials, 12, (17), 2102694, 2022.
[2] Martinez, N. et al. Combined Operando High Resolution SANS and Neutron Imaging Reveals in-Situ Local Water Distribution in an Operating Fuel Cell. ACS Appl. Ener. Mat. 2, 8425–8433, 2019.
[3] Lee, J. et al. Neutron imaging of operando proton exchange membrane fuel cell with novel membrane. J Power Sources 496, 2021.
[4] E. Lübke, et al. The Origins of Critical Deformations in Cylindrical Silicon Based Li-Ion Batteries. Energy & Envir. Science, 2024, in review.
[5] F. Foglia et al, Decoupling polymer, water and ion transport dynamics in ion-selective membranes for fuel cell applications. Journal of Non-Crystalline Solids: X 13 100073, 2022
[6] Takeiri, F. et al. Hydride-ion-conducting K2NiF4-type Ba–Li oxyhydride solid electrolyte. Nature Materials, 21, 325–330, 2022.

Speaker: Sandrine LYONNARD (CEA)

14 Oxide Ion Dynamics in Bi$_2$O$_3$-based Solid Electrolytes: Combining Quasielastic Neutron Scattering with Ab Initio Molecular Dynamics

Solid oxide ion conductors are important materials in applications like oxygen-permeable membranes and solid oxide fuel cells (SOFC). In the latter, they are used as solid electrolytes. Current SOFC electrolyte materials, however, require high temperatures to achieve a sufficiently high oxide ion conductivity for device applications. Developing materials with excellent ionic conductivity at intermediate temperatures (400–600 °C) is a crucial step in making SOFC more widely applied. Understanding the relationship between structural properties and high ionic conductivity is therefore an important part of current research on energy materials. Quasielastic neutron scattering is an excellent method for studying solid state diffusion and allows the observation of oxygen dynamics on a microscopic timescale. Combined with ab initio molecular dynamics simulations, it can provide a comprehensive insight into diffusion processes on the atomic scale. We used this combined approach to investigate and compare the different oxide ion dynamics in two isostructural materials: Bi$_{0.852}$V$_{0.148}$O$_{1.648}$ and Bi$_{0.852}$P$_{0.148}$O$_{1.648}$, and account for the superior performance of the vanadate. Using the backscattering spectrometer IN16b and the time-of-flight spectrometer IN5 at the ILL allowed direct observation of dynamics on the nanosecond and picosecond timescales, and analysis in conjunction with molecular dynamics simulations allowed us to elucidate the structural characteristics important for oxide ion conduction in these doped bismuth oxides.

Speaker: Bettina Schwaighofer (Institut Laue Langevin, Durham University)

15 Energy Storage Applications of Neutron Imaging at MLZ

The fundamentally different interaction of x-rays and neutrons with matter renders neutron imaging a valuable and complementary tool for non-destructive testing applications. Many light elements which are generally hard to detect with x-rays show excellent contrast in neutron imaging. Most prominently, these are hydrogen, lithium and boron. At the same time metals are often significantly more transparent for neutrons than for x-rays. The excellent contrast for hydrogen and lithium makes neutron imaging ideally suited to study energy storage and conversion systems such as fuel cells, electrolysers or lithium-ion batteries.
In our presentation we will give an overview of recent experiments on energy storage applications performed in collaboration with users and industrial customers. In CO2 electrolyzers, we have investigated the dynamic distribution of water and salt precipitates at different current densities and identified their influence on the performance of the electrolyzer cells.
An important economic aspect in the manufacturing of lithium-ion batteries is the process of filling the batteries with electrolyte prior to cell formation. Failure to complete the wetting of the cell, leads to the irreversible loss of capacity. Here, neutron imaging provides an ideal tool to follow the wetting process in real time and provide pathways for the optimization. Even large lead acid batteries can be investigated using fission neutrons uniquely available at our beam line NECTAR, thus providing unique insights into full scale battery systems.

Speaker: Richi Kumar

10:20 Coffee break

16 Four Dimensional Isotope Tracking with the N4DP Instrument at MLZ

Neutron Depth Profiling (NDP) is a non-destructive, element-specific, high-resolution nuclear analytical technique commonly used to study concentration profiles of lithium, boron, nitrogen, helium, and several other light elements in various host materials. The N4DP instrument is located at the Prompt Gamma Activation Analysis (PGAA) beamline of the Heinz Maier-Leibnitz Zentrum (MLZ), which provides a cold neutron flux of up to $5\times10^{10}\,$s$^{-1}$cm$^{-2}$. The NDP technique uses the capture reaction of a specific nuclide with a subsequent decay into ions of well-defined energies. From the energy loss of these ions, concentration depth profiles can be determined with a precision of tens of nanometers.

Operating systems with light elements, such as lithium, require intensive monitoring studies to explain morphological interface effects. For example, in the operation of thin-film batteries, it is of great interest to follow the movement of the Li cloud during (dis-)charging with high precision. In addition, inhomogeneities in such electrochemical processes also require good spatial resolution to obtain concentration information at different locations within the battery. However, there is a lack of detectors with high detection efficiency and temporal resolution. We have developed a detector system based on double-sided silicon strip detectors (DSSSD) with extremely thin and homogeneous entrance windows to provide laterally resolved NDP measurement types for the N4DP instrument. A highly segmented DSSSD with 32$\times$266 stripes, including integrated, self-triggering electronics for vacuum operation, has been successfully tested and evaluated at the Research Reactor in Delft (RID), Netherlands. Using a dual-detector setup in a camera-obscura geometry, we achieved the image and reconstruction of Li-containing targets over a wide range of parameters. These range from a spatial resolution down to $\sim$100\,$\mu$m$\times$200\,$\mu$m, and a lower integration time limit in the order of seconds to collect sufficient statistics to monitor local variations of the Li concentration. This project is supported by the BMBF, contract No. 05K16WO1, 05K19WO8.

Speaker: Robert Neagu (TUM)

17 Neutron depth profiling and GD-OES as tools for characterization of Li plating in Si/graphite anodes from Li-ion battery cells

The loss of Li inventory is a common aging mechanism in Li-ion batteries. To better understand these underlying reversible and irreversible degradation processes in Si/graphite electrodes, depth-resolved methods need to be used to obtain information on the decomposition products of the lithium-containing electrolyte across the electrode thickness. In this work we present two Post-Mortem analytical methods, which can be used to obtain quantified Li depth profiles to depths bigger than 10 µm from the electrode surface, the neutron depth profiling (NDP) and glow discharge optical emission spectroscopy (GD-OES). The validation of GD-OES using NDP by examining the Si/graphite anodes from cylindrical 21700 cells is presented. These two methods are complementary to each other since they are based on different measurement principles and an improvement for the GD-OES calculations of depth profiles of Li in electrodes has been established. It has been demonstrated that the preferential sputtering can occur on the anode surface during the GD-OES measurements. This phenomenon is caused by the higher sputter rate of Li, as it is mainly present in the Li plated layer or in the solid electrolyte interface (SEI).

Speaker: Ivana Pivarnikova

18 Unraveling Supercritical H2 and D2 Adsorption in Nanoporous Carbon: Insights from Neutron Scattering

Neutrons serve as invaluable tools for probing hydrogen (H2) storage within porous materials, particularly in the context of investigating supercritical H2 and deuterium (D2) adsorption in nanoporous carbon. Through the application of Small-Angle Neutron Scattering (SANS) and using an analytical scattering function resembling slit pores, corresponding to Meso-, Supermicro-, and ultramicropores according to IUPAC guidelines, allows to fit the SANS signals accurately. Further utilizing a hierarchical contrast model, pore size-dependent densities have been calculated, revealing a noteworthy observation: both H2 and D2 exhibit a tendency to approach solid density within ultramicropores. Moreover, essential exchange of H with D, predominantly present at the surface, has been observed [1]. Further elucidating the dynamics of adsorbed H2, Inelastic Neutron Scattering (INS) and Quasi-Elastic Neutron Scattering (QENS) techniques have been employed in studying ordered mesoporous and microporous carbon structures. This multifaceted investigation sheds light on the mechanisms underlying H2 storage in nanoporous carbon, offering significant insights for future developments in this critical field.
References:
[1] S. Stock, M. Seyffertitz, N. Kostoglou, M.V. Rauscher, V. Presser, B. Demè, V. Cristiglio, M. Kratzer, S. Rols, C. Mitterer, O. Paris, Hydrogen Densification In Carbon Nanopore Confinement: Insights From Small-Angle Neutron Scattering Using A Hierarchical Contrast Model, Submitted for publication. https://doi.org/10.2139/ssrn.4617430.

Acknowledgements:
The authors would like to acknowledge the beamtime allocation at the Institute Laue-Langevin (ILL) in Grenoble under proposal no. 1-04-218 and 1-04-239. Furthermore, the authors would like to acknowledge the input to this work by V. Presser, V. Cristiglio, M. Kratzer, and S. Rols.

Speaker: Sebastian Stock (Montanuniversität Leoben, Chair of Physics)

12:00 Lunch break

FRMII Guided Tour

Convener: Anatoliy Senyshyn

Day2: Poster Session

18:20 Dinner

Day2: Poster Session

Thursday 6 June

19 Dense packing of molecular hydrogen in a porous hydride and the value of in situ diffraction studies of gas adsorption

Nanoporous materials have attracted great attention for gas storage, however, high volumetric storage capacity remains still a challenge. We investigate [1] a magnesium borohydride framework with small pores and a unique partially negatively-charged non-flat interior for hydrogen and nitrogen uptake by using neutron powder diffraction, volumetric gas adsorption, inelastic neutron scattering, and first-principles calculations. Hydrogen and nitrogen occupy distinctly different adsorption sites in the pores with very different limiting capacities: 2.33 H2 and 0.66 N2 per Mg(BH4)2. Molecular hydrogen is packed extremely dense with about twice the density of liquid hydrogen (144 g H2/L of pore volume), independently measured by three experimental methods. A penta-dihydrogen cluster is discovered where H2 molecules in one position have rotational freedom whereas in another have a well-defined orientation and a directional interaction with the framework. This study [1] reveals that densely packed hydrogen can be stabilized in small-pore materials at ambient pressures.
Studies of physisorbed hydrogen require the use of neutron powder diffraction. For heavier molecules, in situ X-ray powder diffraction allows to study adsorption thermodynamics and kinetics [2, 3], revealing simultaneously the microscopic origins of guest-host and guest-guest interactions. (Quasi)-equilibrium isotherms and isobars can be built directly from sequential Rietveld refinements, both on adsorption and desorption, thus addressing the hysteresis and kinetics of gas adsorption/desorption. Detailed picture of guest reorganization with an increasing uptake can be obtained.
[1] H. Oh, …, Y. Filinchuk, Small-pore hydridic frameworks store densely packed hydrogen. Nature Chem., 2024, DOI: https://doi.org/10.1038/s41557-024-01443-x
[2] I. Dovgaliuk, V. Dyadkin, M. Vander Donckt, Y. Filinchuk, D. Chernyshov, ACS Appl. Mater. Interfaces 12, 2020, 7710.
[3] I. Dovgaliuk, I. Senkovska, X. Li, V. Dyadkin, Y. Filinchuk, D. Chernyshov, Angew. Chem. Int. Ed., 60, 2021, 5250.

Speaker: Yaroslav Filinchuk (Université catholique de Louvain)

20 Use of Neutron Diffraction for the Characterization of Metal Hydrides

For the development of hydrogen as an energy carrier efficient ways to store hydrogen should be implemented. Beside storage in pressure tanks and in liquid form, an effective way to store hydrogen is in metal hydrides. Metal hydrides are attractive for storing hydrogen because they have high volumetric capacities, low operational pressure, and could be used for any scale of applications. In order to design metal hydrides that will match the operational conditions, a fundamental understanding of hydrogen-metal interaction is needed. Practically the only way to probe hydrogen in the crystal structure of a metal hydride is by using neutrons. In this talk we will present a few examples of using neutrons to get a better knowledge of a metal hydride. First, we will show that one can use the different scattering lengths of deuterium and hydrogen to study the dynamic of hydrogenation in the Mg-Fe system. The second example will be the phase transformation of BCC to FCC in a Ti-V-Mn alloys. Here, we used that fact that the BCC alloy is effectively a null matrix and the appearance of the hydride phase is very easy to identify during in-situ experiments. We will conclude the talk with a short discussion of other ways to use neutrons to characterize metal hydrides.

Speaker: Jacques Huot (Université du Québec à Trois-Rivières (UQTR))

21 Investigation of a hydrogen storage process using in situ SANS measurements and simulations

The global energy demand is increasing year by year. The current trend of satisfying energy requirements mostly with fossil fuels is expected to lead to an irreversible increase in temperature. Therefore, alternative energy sources must be explored. Hydrogen is a promising alternative to fossil fuels due to its high gravimetric energy density. However, the low volumetric density of hydrogen in the gas and liquid phase restricts its use as a fuel [1]. The storage of hydrogen using metal hydrides may be a possible solution to this problem. Therefore, in this work, a mixture of MgNH2, LiBH4, and LiH was investigated using neutron scattering as a possible hydrogen storage material. Hydrogen absorption and desorption were followed on the nanoscale with in situ small-angle neutron scattering (SANS) measurements [2].
The scattering curves do not allow a direct deduction of the processes happening in the material, but they are a sensitive tool to check the applicability of different hypotheses. As the simplest possible model, diffusion of hydrogen into and out of a spherical isotropic grain of hydrogen storage material was simulated and the corresponding scattering patterns were calculated using a method introduced recently [3]. The disparity between the simulation results and the measurements shows that a more complicated model has to be used for the description of the sample. Therefore, anisotropic structures of absorbed and desorbed states were generated. A refined version of this model resulted in scattering curves that are compatible with the measured data.
The overall conclusion of this work is that SANS probes the sample at a length scale that detects the nanoscopic microstructure of the hydrogen storage material. Therefore important insights can be extracted from SANS measurements before going to a bigger engineering scale, where the storage material can be approximated as an isotropic material.
[1] C. Pistidda, doi - http://doi.org/10.3390/hydrogen2040024
[2] N. Aslan et al., doi - http://dx.doi.org/10.3233/JNR-190116
[3] A. Majumdar et al., doi - https://doi.org/10.3390/ijms25031547

Speaker: Arnab Majumdar (Helmholtz Zentrum hereon)

10:20 Coffee break

22 What we Learn from Positron Annihilation Spectroscopy on Energy Materials such as Proton Exchange Membranes

In the research on energy materials the positron is applied as a highly mobile probe for the detection of vacancy-like defects and their chemical surrounding in a non-destructive way. (Coincidence) Doppler broadening spectroscopy ((C)DBS) of the positron annihilation line is used to investigate defect distributions or the identification of vacancies, e.g. in electrode materials in order to understand how structural and Li vacancies affect parameters such as capacity, rate capability, and aging [1]. Positron annihilation lifetime spectroscopy (PALS) provides a powerful technique for characterizing the free volume and, more specifically, the mean pore size in polymers.
We performed PALS measurements on proton exchange membranes (PEMs) at different humidity in order to study the change of the free volume and the pore size distribution [2,3]. Such PEMs are used in fuel cells in which the humidity control and water management is high importance to improve the fuel cell efficiency. A slight decrease in the free volume was found up to a relative humidity of 30% whereas it increases strongly for a relative humidity of more than 30%. The volume of the voids doubles from 0.036 to 0.078nm3 by changing the relative humidity from 30 to 80% [3]. In this contribution, I will give a brief overview of positron applications on different materials relevant for energy research, focusing specifically on measurements on PEMs.

[1] S. Seidlmayer, I. Buchberger, M. Reiner, T. Gigl, R. Gilles, H.A. Gasteiger, and C. Hugenschmidt; J. Power Sources 336 (2016) 224
[2] M. Gomaa, C. Hugenschmidt, M. Dickmann, E.E. Abdel-Hady, H.F.M. Mohamed, and M.O. Abdel-Hamed; Phys. Chem. Chem. Phys. 20 (2018) 28287
[3] M. Gomaa, C. Hugenschmidt, M. Dickmann, M. Abdel-Hamed, E. Abdel-Hady, H. Mohamed; Acta Phys. Pol. A 132 (2017) 1519

Speaker: Christoph Hugenschmidt (MLZ/FRM II, TU München)

23 Understanding Li/Ni disorder effects in NCA-type battery cathodes

The replacement of combustion engines by battery-powered electric drivetrains is one of many important steps in order to reduce the emission of greenhouse gases on the way to a green future. Thus, the demand on Li-ion batteries with higher capacities, energy\power densities and cycling life is increasing. Based on these requirements different kinds, of commercial used mixed lithium transition metal oxide cathode materials have been developed. One of the most encouraging cathode material is high nickel content LixNi0.8Co0.15Al0.05O2 (NCA), crystallizing in a NaCrS2-structure type and possessing high power\energy densities at lower costs and increased safety due to the minimized amounts of costly, rare and reactive cobalt [1, 2]. However, nickel-containing LIBs show poor thermal stability, capacity and power fading, as well as an efficiency loss due to the blocking of the 2D diffusion pathways of Li-ions caused by mixed occupations of Li/Ni (cation mixing) in the cathode. In order to address the problem of cation mixing ex situ neutron powder diffraction at the high-resolution powder diffractometer SPODI (FRM II) was applied on extracted NCA materials harvested from a series of 18650-type cells charged to different states. The collected structural data was modeled using full-profile Rietveld refinement and obtained results were discussed dependent on its electrochemical behavior. A decreasing character of lithium concentration upon cell charging along with charge-independent transition metal occupations revealed the absence of cation mixing in the NCA cathode during the discharge from 4.2 to 2.5 V in full cell configuration against the graphite negative electrode.
References
[1] G. Zhao, X. Wang and M. Negnevitsky, iScience, 2022, DOI 10.1016/j.isci.2022.103744
[2] A. Purwanto, C. S. Yudha, U. Ubaidillah, H. Widiyandari, T. Ogi and H. Haerudin, Materials Research Express, 2018, DOI 10.1088/2053-1591/aae167

Speaker: Tobias Hölderle (FRMII TUM)

24 Inelastic Neutron Scattering applied to porous materials

Neutron scattering is a rare experimental technique because there are only a few places worldwide where it is
possible to perform the required experiments. The Spallation Neutron Source at ORNL in East Tennessee is the most advanced pulsed neutron source. The interaction of neutrons with the nuclei provides unique information on light elements (like hydrogen). It can distinguish between neighboring elements and isotopes, complementing X-ray capabilities and other photon-based techniques. In the case of Inelastic Neutron Scattering (INS), the technique is the neutron analog of Raman and infrared spectroscopies. Instead of using photons as the probing beam, a neutron beam illuminates the sample. The penetrating power of neutrons means that with the adequate selection of materials, it is possible to build sample environments that can manage extreme conditions in pressure and temperature without the need for optically transparent windows—giving the technique much versatility. Gas handling experiments are trivial. The main disadvantages of INS are that measurements usually require cryogenic temperatures, the neutron fluxes are low when compared with photons, and accessing neutron scattering facilities is challenging.
Atomistic computer modeling, particularly DFT, molecular dynamics, etc., is routinely used to interpret and analyze experimental results. The interplay of atomistic modeling and experimental data is unique and allows access to a precious insight into the mechanistic interpretation of the data.
Porous materials have space voids where it is possible to adsorb molecules. Trapping these molecules to "store" them or sometimes react chemically is used in many applications. This talk will present examples of INS spectroscopy applied to small molecule adsorption on porous
materials, with particular emphasis on hydrogen molecules. Materials from zeolites and carbons to metal-organic frameworks highlight the unique information the technique provides and how computer models are essential to interpreting the data.

Speaker: Anibal (Timmy) Ramirez-Cuesta (Oak Ridge National Laboratory)

12:00 Lunch break

25 Electrolyte Motion Induced Salt Inhomogeneity in Large- Format Lithium-Ions Cells – Implications for Cell Lifetime and Performance

In 2023, the Dalhousie group demonstrated that expansion of active materials causes electrolyte flow in cylindrical cells upon cell cycling. We show that this electrolyte motion can cause severe inhomogeneity in the spatial distribution of conducting salt inside the jelly roll/stack in cylindrical cells and also in prismatic lithium-ion cells under high compression. This novel mechanism -which we termed „electrolyte motion induced salt inhomogeneity” (EMSI) – has a very strong impact on cell lifetime and performance, especially when applying high charge or discharge currents.
We present 1) experimental data on the build-up of the LiPF6 salt gradient (and a novel and simple experimental approach for measuring this gradient), 2) a consistent mechanistic explanation, 3) 3D simulation with coupling of electrochemistry and fluid-dynamics and 4) a discussion on the implications of this novel ageing mechanism and possible applications of neutron imaging/ diffraction in this respect.

Speaker: Dr Johannes Wandt

26 Investigating the Influence of Cyclic Ageing on the Structure of NCM Cathodes and Graphite Anodes in commercial 21700 Li Ion Batteries

Li-ion batteries as energy storage devices play a significant role in the global agenda to mitigate emissions, move to sustainable energy sources, and fight climate change. In recent years, new battery formats have emerged with the intention of increasing energy. Moving from the conventional cylindrical 18650 design to the 21700 format can achieve higher energy content per cell.[1] These batteries are used in different scopes, such as electric vehicles in the automotive industry.
By scaling up the size of the battery, effects such as temperature and electrolyte distribution or inhomogeneities are gaining more influence on the cycling behaviour of the battery in comparison to smaller lab-size batteries.[2] Therefore, studying commercial cells to understand the lithiation and ageing mechanisms inside the electrodes is as essential.
Here, in-operando neutron diffraction experiments were conducted on 21700 cells with NCM as a cathode material and graphite as an anode material at the DMC instrument at the Paul Scherrer Institute (PSI). By comparing three different states of health, the influence of cyclic ageing on the electrodes could be investigated.
The loss of capacity can be seen in the electrochemical data and the structural change of the electrodes. The movement of the 113 NCM-peak is reduced for the aged cell, indicating that unit cell change is restricted due to the loss of Li. Simultaneously, the range in which the lattice parameters are moving during cycling is shifting to lower values for the aged cells suggesting that the cathode is pushed to higher potentials. For the anode, the amount of the LiC6 phase is decreased for the aged cells, which confirms the loss of Li and is in accordance with the results from the cathodes.

[1] J. B. Quinn, T. Waldmann, K. Richter, M. Kasper, M. Wohlfahrt-Mehrens, J. Electrochem. Soc. 2018, 165, A3284-A3291.
[2] D. Beck, P. Dechent, M. Junker, D. U. Sauer, M. Dubarry, Energies 2021, 14, 3276.

Speaker: Thien An Pham

14:00 Excursion and dinner outside

An excursion to the Deutsche Museum with dinner in the nearby restaurant. Shuttle bus service from/to the Conference Venue to the Deutsche Museum will be provided.

Friday 7 June

27 New Current Collectors for Lithium-Metal Batteries

Lithium-metal batteries (LMBs) are considered the next big step towards higher energy densities. The anticipated increase in energy density, however, can be achieved solely, if the lithium foil used at the negative electrode will be sufficiently thin.[1,2] This, in turn, requires an essentially perfect reversibility of the lithium plating and stripping process with a Coulombic efficiency approaching 100%, i.e., the absence of essentially any side reaction that consumes electrochemically active lithium (and electrolyte), and a very homogeneous lithium deposition upon charge.[3,4] The commonly used commercial copper foil, however, does not allow for one or the other. Herein, our recent work on the development of new current collectors for the negative electrode of LMBs is presented, including the modification of the copper current collector to enhance the reversibility and homogeneity of the lithium plating process as well as fundamentally new concepts. A particular focus is set on the development of a better understanding of relevant impact factors, always keeping in mind in every case the eventual requirements for complete LMB cells that could be of commercial relevance.

References
[1] J. Liu, Z. Bao, Y. Cui, E. J. Dufek, J. B. Goodenough, P. Khalifah, Q. Li, B. Y. Liaw, P. Liu, A. Manthiram, Y. S. Meng, V. R. Subramanian, M. F. Toney, V. V. Viswanathan, M. S. Whittingham, J. Xiao, W. Xu, J. Yang, X.-Q. Yang, J.-G. Zhang, Nature Energy 2019, 4, 180.
[2] C. Niu, D. Liu, J. A. Lochala, C. S. Anderson, X. Cao, M. E. Gross, W. Xu, J.-G. Zhang, M. S. Whittingham, J. Xiao, J. Liu, Nat Energy 2021, 6, 723.
[3] X. He, D. Bresser, S. Passerini, F. Baakes, U. Krewer, J. Lopez, C. T. Mallia, Y. Shao-Horn, I. Cekic-Laskovic, S. Wiemers-Meyer, F. A. Soto, V. Ponce, J. M. Seminario, P. B. Balbuena, H. Jia, W. Xu, Y. Xu, C. Wang, B. Horstmann, R. Amine, C.-C. Su, J. Shi, K. Amine, M. Winter, A. Latz, R. Kostecki, Nat. Rev. Mater. 2021, 6, 1036.
[4] B. Horstmann, J. Shi, R. Amine, M. Werres, X. He, H. Jia, F. Hausen, I. Cekic-Laskovic, S. Wiemers-Meyer, J. Lopez, D. Galvez-Aranda, F. Baakes, D. Bresser, C.-C. Su, Y. Xu, W. Xu, P. Jakes, R.-A. Eichel, E. Figgemeier, U. Krewer, J. M. Seminario, P. B. Balbuena, C. Wang, S. Passerini, Y. Shao-Horn, M. Winter, K. Amine, R. Kostecki, A. Latz, Energy Environ. Sci. 2021, DOI 10.1039/D1EE00767J.

Speaker: Dominic Bresser (Karlsruhe Institute of Technology (KIT))

28 Perfluoropolyether based polymer coatings for iinterfacial stability in lithium-based batteries

Lithium metal batteries are next-generation energy storage devices that rely on the stable electrodeposition of lithium metal during the charging process. A major challenge associated with this battery chemistry is related to the uneven Li deposition that leads to dendritic growth and poor coulombic efficiency (CE). A promising strategy for addressing this challenge is utilizing a polymer coating on the anodic surface to protect it and improve interfacial stability.
In this contribution, we demonstrate the influence of mechanical strengths in perfluoropolyether based polymer coatings on battery performance, and show that batteries prepared with polymer coatings having lower mechanical strength and better flowability exhibit higher CEs and a homogeneous Li deposition in comparison to those prepared using mechanically rigid polymers [1]. Further, we investigate polymer dynamics as a function of mechanical strength and/or Li salt using QENS in an attempt to correlate the observed dynamics with their viscosity and ionic conductivity.

[1] Huang, Z. ; Choudhury, S. ; Paul, N. ; Thienenkamp, J. H. ; Lennartz, P. ; Gong, H. ; Müller-Buschbaum, P. ; Brunklaus, G. ; Gilles, R. ; Bao, Z. Effects of Polymer Coating Mechanics at Solid‐Electrolyte Interphase for Stabilizing Lithium Metal Anodes, Adv. Energy Mater. 2022, 12, 2103187.

Speaker: Dr Neelima Paul (Technical University of Munich, Heinz Maier-Leibnitz Zentrum (MLZ))

10:20 Coffee break

29 Tuning Ion Mobility in Lithium Argyrodite Solid Electrolytes via Entropy Engineering

Solid-state batteries (SSBs) are attracting great interest leading to potentially higher energy and power densities compared to conventional Li-ion batteries based on liquid electrolytes. However, they are plagued by the development of advanced solid electrolytes (SEs), mainly lacking in ionic conductivity and electrochemical stability; thus, the ongoing quest for exploration of new materials and compositions. Inducing a large structural disorder, i.e. high configurational entropy, has recently emerged as a new strategy to overcome limitations of conventional SE materials. In this regard, few multicomponent SE materials have been reported up to now, showing favorable charge-transport properties [1,2]. However, a thorough understanding on how configurational entropy affects ionic conductivity is lacking. In this regard, we have investigated a large series of multication- and anion substituted lithium argyrodites. Structure-property relationships related to ion mobility were probed using a combination of powder diffraction techniques, solid-state nuclear magnetic resonance spectroscopy, and charge-transport measurements.
In this contribution, we present an overview of our recent work and show correlations between configurational entropy and ionic conductivity [1,3]. To the best of our knowledge our results present the first experimental evidence of a direct correlation between occupational disorder in the cationic, or anionic host lattice and lithium transport. By controlling the configurational entropy through the composition, i.e. entropy engineering, high bulk ionic conductivities up to 20 mS/cm at room temperature were achieved for optimized lithium argyrodite compositions. Our results indicate the possibility of improving ionic conductivity in ceramic ion conductors via entropy engineering, unlocking the compositional limitations for the design of advanced electrolytes and opening up new avenues in the field.

References:
[1] J. Lin, G. Cherkashinin, M. Schäfer, G. Melinte, S. Indris, A. Kondrakov, J. Janek, T. Brezesinski, F. Strauss, ACS Material Letters 4, 11 (2022)
[2] Y. Li, S. Song, H. Kim, K. Nomoto, H. Kim, X. Sun, S. Hori, K. Suzuki, N. Natsui, M. Hirayama, T. Mizoguchi, T. Saito, T. Kamiyama, R. Kanno, Science 381, 50 (2023)
[3] S. Li, J. Lin, M. Schaller, S. Indris, X. Zhang, T. Brezesinski, C.-W. Nan, S. Wang, F. Strauss, Angewandte Chemie International Edition e202314155 (2023)

Speaker: Dr Florian Strauss (Karlsruher Institut für Technologie)

30 Combined neutron depth-profiling with ion-beam analysis study of Li surface gradients in Li-garnet solid electrolytes from all-solid-state-batteries

Knowledge of surface and interface interaction is crucial for future next-generation battery concepts like all-solid-state batteries (ASSB). Spatial and time dependent Li distribution plays a significant role in understanding performance, aging, and failure mechanisms. However, Li detection remains a challenging task and only few techniques enable measuring its spatial distribution in battery components or even full cells. Non-destructive techniques are even more scarce. To our knowledge only neutron depth-profiling (NDP) and Ion-Beam-Analysis (IBA) are capable of absolute Li quantification under the given sample conditions. Both techniques originate from the utilization of nuclear processes to gain information about the nuclei present in the sample. However, due to the nature of the two approaches they differ in their resolving capabilities. IBA has a high lateral resolution but is rather limited in depth resolution, while NDP is conversely having a high depth but low lateral resolution. Thus, a combination of both methods would make the best of both worlds. Our study combines both techniques on identical samples of Li-ASSBs and allows us benchmark for the first time the strength and drawbacks of the two methods. We derive depth dependent Li-concentrations and validate a microstructural model of charge, discharge, and relaxation of ASSBs together with an electrochemical analysis. The work shows the fundamental advantages of such a combined approach to optimize materials and battery cells for ASSBs.

Speaker: Stefan Seidlmayer (Universität Bayreuth, BayBatt, Lehrstuhl für Anorganische Aktivmaterial für elektrochemische Energiespeicher,)

31 Operando visualization of mass transfer in sodium-zinc liquid metal batteries

The Horizon 2020 project SOLSTICE aims to deliver two different working battery prototypes based on the price-competitive Na-Zn chemistry. The first concept benefits from the existing and successful ZEBRA® technology where the Ni-electrode is replaced by cheap and abundant Zn while the second approach aims to remove the need for the solid ion-conductive membrane by using molten salt electrolyte. To support this objective, small-scale experimental cells have been developed for fundamental research. They have been designed to allow for in situ radiographic imaging of the interior. The main objective is to charge and discharge the cells during dynamic neutron radiography, in order to observe the mass transfer of electroactive species and any flow that occurs during cycling. The focus is on how these phenomena depend on the geometry and chemical composition of the different cell components, such as the positive and negative current collectors. Neutron radiography experiments have been successfully conducted at the Paul Scherrer Institut (PSI) in Villigen, Switzerland, using the NEUTRA instrument of the neutron spallation source SINQ. Analysis of the obtained data, in particular the recorded radiographic image sequences fully demonstrating what happens during the cycling of the cells, will be presented at the conference.

Speaker: Dr Martins Sarma (Helmholtz-Zentrum Dresden - Rossendorf)

32 Concluding remarks & Summary

12:00 Lunch break