| 1. |
- Atkins, Duncan, et al.
(författare)
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Accelerating Battery Characterization Using Neutron and Synchrotron Techniques: Toward a Multi-Modal and Multi-Scale Standardized Experimental Workflow
- 2022
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 12:17
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Tidskriftsartikel (refereegranskat)abstract
- Li-ion batteries are the essential energy-storage building blocks of modern society. However, producing ultra-high electrochemical performance in safe and sustainable batteries for example, e-mobility, and portable and stationary applications, demands overcoming major technological challenges. Materials engineering and new chemistries are key aspects to achieving this objective, intimately linked to the use of advanced characterization techniques. In particular, operando investigations are currently attracting enormous interest. Synchrotron- and neutron-based bulk techniques are increasingly employed as they provide unique insights into the chemical, morphological, and structural changes inside electrodes and electrolytes across multiple length scales with high time/spatial resolutions. However, data acquisition, data analysis, and scientific outcomes must be accelerated to increase the overall benefits to the academic and industrial communities, requiring a paradigm shift beyond traditional single-shot, sophisticated experiments. Here a multi-scale and multi-technique integrated workflow is presented to enhance bulk characterization, based on standardized and automated data acquisition and analysis for high-throughput and high-fidelity experiments, the optimization of versatile and tunable cells, as well as multi-modal correlative characterization. Furthermore, new mechanisms, methods and organizations such as artificial intelligence-aided modeling-driven strategies, coordinated beamtime allocations, and community-unified infrastructures are discussed in order to highlight perspectives in battery research at large scale facilities.
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| 2. |
- Gustafsson, Olof
(författare)
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Crystallographic studies of non-equilibrium structural changes in cathode materials
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Battery cathode materials are a key focus for improvement of Li-ion battery chemistries due their limits in terms of capacity and cost. During insertion and extraction of Li, many cathode materials exhibit structural changes, ranging from e.g. phase transitions to amorphization. Such structural rearrangements can be unfavourable for electrochemical performance due to the incompatibility between any intermediate phases formed. The crystalline structure can be readily studied using diffraction techniques such as X-ray and neutron diffraction, making them a versatile tool for identifying and understanding these structural changes. The work in this thesis focuses on utilizing diffraction to study equilibrium and non-equilibrium changes in the crystalline structure of the two cathode materials LiNi0.5Mn1.5O4 and Li2VO2F. Both of these materials display interesting structural behaviour upon electrochemical cycling, some of it which can be linked to how the cations arrange in the structure. As such, the work presented here aims to elucidate further on the cationic structural features of these materials and how these may impact their use in batteries. For both LiNi0.5Mn1.5O4 and Li2VO2F, the (re)arrangement of cations in the structure was found to play a crucial role for both equilibrium and non-equilibrium structural transitions occurring. In particular, the formation of phases that could be regarded as disadvantageous from a battery application perspective could be attributed to cationic diffusion. Due to the many structural similarities of transition metal oxide-based cathode materials, structural reorganization following similar mechanisms involving cationic rearrangement could be expected also in other materials similar to those studied here. As such, strategies for mitigating any unwanted redistribution of cations in the structure should be considered for improving the performance of this class of cathode materials.
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| 3. |
- Ihrfors, Charlotte, 1989-
(författare)
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Electrochemical characterisations of TiO2 nanotube and lithium-metal electrodes for lithium-based batteries
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lithium-ion batteries have since their introduction on the commercial market in the early 1990s played an important role within the field of energy storage. In this thesis both titanium dioxide, TiO2, and lithium metal are investigated based on their properties as anodes for lithium-based battery technologies. TiO2 nanotubes with lengths between 4.5 and 40 µm were synthesized through a two-step anodization of titanium metal foil in a fluoride containing electrolyte. The formed nanotubes were investigated using scanning electron microscopy and electrochemically evaluated in pouch-cell batteries. For the long nanotubes, especially the 40 µm long ones, the results indicate that the lithiation and delithiation processes are limited by the solid state diffusion of lithium ions within the electrode material for the employed cycling conditions. Studies of the TiO2 nanotubes at elevated temperatures, 80 °C, showed a good temperature stability both in a conventional organic electrolyte and in an ionic liquid based electrolyte. In full cells the ionic liquid electrolyte was needed to get a good performance mainly due to the LiFePO4 cathode. Despite a good general performance, the TiO2 nanotubes show capacity losses during high rate cycling. This effect was studied using galvanostatic cycling including open circuit periods and analyses of the cycled electrodes with inductive coupled plasma atomic emission spectroscopy. The results indicate the presence of a lithium trapping effect in the TiO2 electrodes caused by the lithium diffusion within the electrode material. The trapping effect was also seen in a comparative study involving TiO2 nanoparticles and nanotubes. The comparison also showed that the electrochemical performance depended on the electrode design.Enabling of 2D lithium growth and avoiding lithium dendrite formation are of great importance for both battery research and practical applications. In this thesis an approach based on formation of a large amount of equally sized lithium nuclei on the surface in combination with a diffusion controlled deposition is described. To achieve this an electrolyte with a low lithium ion concentration, where the migrations is taken care of by a supporting salt, was used in combination with an initial potentiostatic pulse. This approach was found to yield a homogeneous coverage of lithium nuclei and dendrite-free deposition.
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