1,721,090 research outputs found
Tailoring the morphology of LiCoO2: A first principles study
No full textSurface energies of several low-index surfaces of layered LiCoO2 are investigated as a function of the external lithium and oxygen chemical potentials by means of First Principles calculations in the generalized gradient approximation (GGA) to density functional theory (DFT), treating on-site electron correlation within the DFT+U framework. We find the set of surfaces contained in the equilibrium shape to be depending on environment. The(0001)and (10 (1) over bar4) surfaces are present for all reasonable values of the Li and O chemical potentials. The (01 (1) over bar2) surface, however, is stable only under oxidizing conditions. The equilibrium shape is sensitive to the equilibration environment because the thermodynamically favorable surface terminations and surface energies of the polar (0001) and (01 (1) over bar2) surfaces are a function of environment. This provides a lever to tailor the crystal shape according to application requirements (e.g., as active material in lithium-ion batteries)
X-ray tomography for lithium ion battery electrode characterisation — A review
No full textIn recent years, x-ray tomography has emerged as a powerful analytical tool for the study of lithium ion batteries and the processes occurring within. A region of specific interest is the electrode and, in particular, the heterogeneous and porous structure. The present paper is a review of studies that use x-ray tomography to characterise electrode structure, at both the cell and microstructure scales. At the cell level, x-ray tomography is used to investigate macroscopic design parameters, such as anode and cathode thicknesses, packing density and alignment of assembled cells, as well as to visualise any macroscopic structural defects, such as islanding. At the microstructure level, x-ray tomography allows for quantitative analysis of electrode structures to ascertain parameters such as particle size, tortuosity and volume fraction. The paper also explores different techniques that have been used across the field, from ex-situ, in-situ and operando techniques, to multimodal imaging methods, tomography informed design and results informed imaging
OpenImpala: OPEN source IMage based PArallisable Linear Algebra solver
No full textImage-based modelling has emerged as a popular method within the field of lithium-ion battery modelling due to its ability to represent the heterogeneity of the porous electrodes. A common challenge from image-based modelling is the size of 3D tomography datasets, which can be of the order of several billion voxels. Previously, different approximation methods have been used to simplify the computational problem, but each of these come with associated limitations. Here we develop a data-driven, fully parallelisable, image-based modelling framework called OpenImpala. Micro X-ray computed tomography (CT) is used to obtain 3D microstructural data from samples non-destructively. These 3D datasets are then directly used as the computational domain for finite-differences based direct physical modelling (e.g. to solve the diffusion equation directly on the CT obtained datasets). OpenImpala then calculates the equivalent homogenised transport coefficients for the given microstructure. These coefficients are written into parameterised files for direct compatibility with two popular continuum battery models: PyBamm and DandeLiion, facilitating the link between different scales of computational battery modelling. OpenImpala has been shown to scale well with an increasing number of computational cores on distributed memory architectures, making it applicable to large datasets typical of modern tomography
Mechano-electrochemistry effects due to deformation of copper oxide films
Full text linkIn an attempt to elucidate the relationship and underlying processes of metal oxidation under stress, we combined electrochemical characterisation with Density-Functional-Theory (DFT) calculations to interrogate the (100) surface of copper. The oxidised (100) surface shows a missing-row reconstruction, which is believed to be driven by surface stress. Hence, additional mechanical stimuli might have significant impact onto the onset of Cu oxidation. We find that different surface sites respond differently to strain. Oads at the thermodynamically favoured high-coordination hollow site (O coordinated with four Cu) is stabilised by up to 130meV by imposing 2% tensile strain onto the surface, while the low-coordination top site (O coordinated to one Cu) shows a markedly different sensitivity. Cramping into the hollow site, Oads induces compressive stress into the (100) surface, an effect that is largely absent for adsorption at the top site. We also find that the thermodynamic advantage of reconstructive underpotential surface oxidation is diminished under tensile strain. Hence, imposing tensile stress counter-balances the oxygen induced surface stress, which might have an implication on the onset of bulk copper oxidation. Studying Cu (100) single crystal surfaces in perchloric acid using cyclic voltammetry, we were able to confirm sensitivity of the electrochemical response towards elastic strai
Capacitive electronic metal-support interactions: outer surface charging of supported catalyst particles
No full textElectronic metal–support interactions (EMSI) in catalysis are commonly rationalized in terms of an electron transfer between support material and supported metal catalyst particles. This general perspective, however, cannot fully explain experimentally observed EMSI for metallic nanoparticu- late catalysts, because the strong charge screening of metals should locally confine effects of direct electronic interaction with the support to the catalyst–support interface (CSI), which, apart from the perimeter, is largely inaccessible for catalysis reactants. The concept of capacitive EMSI is proposed here for catalyst particles at the nanometer scale, where electronic equilibration results in a long-range charging of the catalytically active outer surface (CAOS) bypassing the expected strong metallic charge screening, which is confirmed and quantified by electrostatic and density functional theory simulations revealing a strong dependence on the coverage of the support surface with catalyst particles. This long-range charge transfer leads to a shift of the local work function at the CAOS. In order to describe the catalytic consequences, an amendment of d-band theory in terms of ‘d-band + work function’ is proposed. Furthermore, the charging of remote catalytic sites at the CAOS scales with the relative dielectric constant of the surrounding medium and it is concluded that EMSI can have surprisingly strong influence especially in the presence of a strongly polarisable dielectric
Dataset for: Phase behaviour of (Ti:Mo)S2binary alloys arising from electron-lattice coupling
No full textTraining set (DFT output) for CE models and MC simulations output for the manuscript Phase behaviour of (Ti:Mo)S2binary alloys arising from electron-lattice coupling</span
Edge and lithium concentration effects on intercalation kinetics for graphite anodes
No full textGraphite interfaces are an important part of the anode in lithium-ion batteries (LIBs), significantly influencing Li intercalation kinetics. Graphite anodes adopt different stacking sequences depending on the concentration of the intercalated Li ions. In this work, we performed first-principles calculations to comprehensively address the energetics and dynamics of Li intercalation and Li vacancy diffusion near the non-basal edges of graphite, namely the armchair and zigzag-edges, at high Li concentration. We find that surface effects persist in stage-II that bind Li strongly at the edge sites. However, the pronounced effect previously identified at the zigzag edge of pristine graphite is reduced in LiC12, penetrating only to the subsurface site, and eventually disappearing in LiC6. Consequently, the distinctive surface state at the zigzag edge significantly impacts and restrains the charging rate at the initial lithiation of graphite anodes, whilst diminishes with an increasing degree of lithiation. Longer diffusion time for Li hopping to the bulk site from either the zigzag edge or the armchair edge in LiC6 was observed during high state of charge due to charge repulsion. Effectively controlling Li occupation and diffusion kinetics at this stage is also crucial for enhancing the charge rate
Dataset: Capacitive Electronic Metal-Support Interactions: Outer Surface Charging of Supported Catalyst Particles
No full textDataset supports:
Binninger, T., Schmidt, T. J., & Kramer, D. (2017). Capacitive Electronic Metal–Support Interactions: Outer Surface Charging of Supported Catalyst Particles. Physical Review B.
This dataset contains input files for Comsol and Vasp used to simulate capacity electronic metal-support interactions
Funded by EPSRC</span
Physics based modelling of porous lithium ion battery electrodes—A review
No full textMathematical models have been used extensively to simulate physical and electrochemical processes occurring inside lithium-ion batteries. Physical based models, coupled with experimental validation, have revealed greater scientific understanding of the processes inside the battery. A region of specific interest is the porous electrode. However, the heterogeneous geometry of the porous structure presents practical difficulties in developing suitable models. The present paper is a review of the studies on the physical modelling of lithium ion porous electrodes. Here we review common methods to model the (de)intercalation behaviour of porous Li-ion battery electrodes. Advantages and drawbacks are contrasted to highlight some challenges that suggest directions and priorities for further research in the field
Phase behaviour of (Ti:Mo) S<sub>2</sub> binary alloys arising from electron-lattice coupling
No full textWhile 2D materials attract considerable interests for their exotic electronic and mechanical properties, their phase behaviour is still largely not understood. This work focuses on (Mo:Ti) S2 binary alloys which have captured the interest of the tribology community for their good performance in solid lubrication applications and whose chemistry and crystallography is still debated. Using electronic structures calculations and statistical mechanics we predict a phase-separating behaviour for the system and trace its origin to the energetics of the d-band manifold due to crystal field splitting. Our predicted solubility limits as a function of temperature are in accordance with experimental data and demonstrate the utility of this protocol in understanding and designing TMD alloys.</p
- …
