1,720,952 research outputs found
Fast interfaces
No full textLi4Ti5O12 is a commonly used negative electrode material, but the origin of its fast rate capability has puzzled scientists for decades. Now, a facile Li-ion transport route featuring metastable intermediates is revealed to rationalize the fast-charging kinetics.Accepted Author ManuscriptRID/TS/Instrumenten groepRST/Storage of Electrochemical Energ
Electrode assembly for a lithium ion battery, process for the production of such electrode assembly, and lithium ion battery comprising such electrode assemblies
No full textThe invention provides an electrode assembly for a lithium ion battery, the electrode assembly comprising a lithium storage electrode layer on a current collector, wherein the lithium storage electrode layer is a porous layer having a porosity in the range of -35 %, with pores having pore widths in the range of 1-100 [mu]m, and having a porous layer thickness in the range of 5-500 [mu]m. The invention also provides a lithium ion battery comprising such electrode assemblies as anode and cathode. Further, a process for the production is provided.RST/Radiation, Science and TechnologyApplied Science
In operando phase transitions and Lithium ion transport in LiFePO4
No full textChemical energy storage in Li-ion batteries is a key technology for the future renewable society. Their energy and power density is largely determined by electrode materials that are able to host lithium in their crystal structure. Aiming at faster and more efficient energy storage, one of the key objectives in Li-ion batteries is to improve the charge transport through the complex heterogeneous electrode morphology. The complex transport phenomena and phase behavior are timely topics and subject of many studies and intense debates. Remarkably, our current knowledge is mostly based on ex-situ techniques or techniques that do not have sufficient time and space resolution to reveal the actual phase nucleation and growth in individual grains. On the electrode length scale the absence of experimental probes that allow direct observation of Li-ion transport in electrodes under realistic in-operando conditions hinders fundamental understanding and the development of rational strategies towards improved electrodes. For LiFePO4, a state of the art cathode material for today’s Li-ion batteries, such direct insights are of high fundamental and practical impact, potentially creating new perspectives in the working and improvements of electrode materials in general. This is the main object of this thesis, revealing the cycling rate dependent phase transition behavior and Li-ion transport throughout the electrodes in LiFePO4 under realistic in-operando conditions.RST/Radiation, Science and TechnologyApplied Science
A Template for Enhanced Lithium Ion Battery Electrodes
No full textDictated by exhausting sources of conventional fossil fuels, their irreversible damage on environment, international conflicts for oil resources – distressing global economy, worldwide research has focused towards developing alternate, but sustainable, sources of energy generation and storage to meet global energy demands and emission-free mobility applications. In recent years, electric cars have become a contemporary notion of sustainable mobility. This has been enabled by the progress in electrochemical energy storage and conversion in batteries. Among the various types of batteries, lithium ion batteries are recognized for their high energy and power density, prerequisites for a long-range and fast charging of electric vehicles. Despite recent developments lithium ion batteries at present are not able to provide the desired energy and power density output for electric vehicles to compete with conventional fossil fuels. The research presented in this thesis explores various fundamental and technical facets of lithium ion batteries aiming at improvement of the energy and power performanceRadiation Science & Technology - Reactor Institute DelftApplied Science
Lithium and Sodium Insertion in Nanostructured Titanates: Experiments and simulations
No full textNanostructured materials are featured by providing a variety of favourable electrical properties, as the reduced ion and electron transport paths enable significant enhancement on (de)intercalation rates and hence high power. For TiO2 anatase, nano-sizing results in a curved open cell voltage profile with a much shorter plateau region in comparison with that of micron sized materials. The main objective of this thesis is to gain insight in the impact of particle size on the Li-ion storage and Na-ion storage in anatase TiO2 using a combined experimental, theoretical approach. In addition a novel Na-ion titanium oxide storage compound is tested and characterized. Nanostructuring has a striking influence on the thermodynamics and kinetics of Li-ion insertion reactions in anatase TiO2. The particle size dependent phase transformations in anatase TiO2 upon lithiation are systematically studied. The equilibrium voltage measured by galvanostatic intermittent titration technique decreases progressively with particle size reduction, which is attributed to the difference in surface energy of the pristine and lithiated phases. Based on the evolution of domain size and phase fraction of the two phases, it is concluded that the first-order phase transition proceeds by continuous nucleation upon lithium insertion. For all particle sizes the phase boundary is found to migrate under non-equilibrium conditions even under very slow (dis)charge conditions. Remarkably, the degree of non-equilibrium condition increases with particle size decreasing, which is rationalized by the difference in the observed phase transition behaviour between small and large particles. The absence of phase coexistence in smaller particles in combination with the sluggish ionic transport rationalizes the better electrochemical performance of the nano-structured anatase TiO2 as compared to the micro sized material. These results suggest a very low nucleation barrier for the formation of new phases and a sluggish ionic migration during phase boundary movement. Therefore strategies to improve the rate performance of nano structured anatase TiO2 should concentrate on improving the interstitial diffusion, for instance by appropriate doping with Nb or Zn. Based on the experimental study on the particle size dependent phase transition behaviour, the impact of particle size and surface orientation on the lithium ion insertion in anatase TiO2 is systematically investigated by using DFT first-principles calculations and surface cluster expansion. Nano-sized TiO2 is modelled by surface slabs with two thermodynamically stable orientations {101} and {001}. The calculated formation energies for bulk and surface structures suggest that the stable Li configuration of Li0.5TiO2 titanate phase depends on the surface orientation. For the Li composition below Li0.5TiO2, the calculated size dependent voltage curves are in qualitative agreement with the experimental results. The calculations show that the voltage difference between the different surface orientations is due to the different Li-O and Ti-O bond length in the surface region. For the Li composition above Li0.5TiO2, the relative magnitudes of the voltage profiles between different surface directions and particle sizes are not consistent with the experimental observations. This is suggested to be the consequence of the stoichiometric surface slabs. A surface excess of oxygen is shown to explain the larger intercalation voltages in smaller particles with the composition above Li0.5TiO2. The demand for renewable energy resources has initiated the search for high performance and cost effective battery systems. Na-ion as a charge carrier is one of the most promising alternatives to Li-ions due to its high abundance, low cost, and comparable high cell potential. Rudola et al. explored Na-ion storage in a novel compound Na2Ti6O13, demonstrating a reversibly uptake of 1 Na ion per formula unit (49.5 mAh/g) by a solid solution mechanism at an average potential of 0.8 V In this thesis it is shown that by lowering the cut-off voltage from 0.3 V to 0 V vs Na/Na+ the capacity of the layered Na2Ti6O13 negative electrode material can be enhanced from 49.5 mAh/g (Na2+1Ti6O13) to a promising 196 mAh/g (Na2+4Ti6O13) for at least 10 cycles, after which it gradually reduces. To understand the structural changes in-situ X-ray diffraction is performed and compared with Density Functional Theory calculations. A consistent evolution of the lattice parameters and Na-ion positions is observed. The results show that Na-ion intercalation in the Na2+xTi6O13 host structure is limited to Na2+2Ti6O13 in a solid solution reaction. Only small changes in lattice parameters indicate that the insertion reaction is highly reversible. Further increasing the Na composition below 0.3 V appears to lead to loss in crystallinity, which in combination with solid electrolyte interface formation is suggested to be the origin of the gradually reducing reversible capacity. The promising Li-ion storage properties of TiO2 anatase provide the motivation to embark on the study of Na-ion insertion in anatase TiO2. Electrochemical and X-ray experiments and DFT calculations are performed to improve the understanding about the particle size dependent electrochemical Na-ion storage in the TiO2 anatase. Reducing the particle size results in a distinct increase of the reversible capacity, also introducing stronger degradation of the cycling stability. The highest specific reversible capacity (210mAh/g) was found for 7 nm TiO2 anatase, which is among the largest reported in literature. Although bulk storage is generally assumed, X-ray diffraction on the electrodes after discharge and charge shows negligible changes on the lattice parameters, indicating that Na-ion insertion in the TiO2 lattice does not occur significantly. Nevertheless DFT calculation predicts that the fully occupied Na1TiO2 (capacity 334mAh/g) can be thermodynamically achieved at a positive voltage (0.3V). The fact that Na-ion insertion does not occur is most likely due to the large energy barrier for Na-ion diffusion which is calculated to be ~0.84eV at the dilute limit. These results indicate that the inserted sodium ions are mainly accommodated at the surface region. Therefore strategies to improve the electrochemical performance of Na storage by TiO2 anatase should focus on improving the surface and electrolyte stability.Radiation, Radionuclides & ReactorsApplied Science
Di-block copolymers as solid-state electrolytes for lithium ion batteries: Novel and solvent-free production methods
No full textNovel and solvent-free routes for producing solid-state electrolyte membranes for lithium ion batteries containing Li[N(CF3SO2)2] (LiTFSI) and Arnitel® copolymers produced and provided by DSM are proposed and elaborated in this graduation project. Other lithium salts such as Li[B(C2O4)2] (LiBOB) and LiCl have also been tested, but more research has been focused on LiTFSI. Arnitel materials with variable proportions of poly(ethylene oxide) (PEO) and polybutylene terephthalate (PBT) have been used. The presented solvent-free methods of incorporating the lithium salt are intended as an alternative to the solvent route, that involves the use of hazardous HFiP, previously investigated in internal DSM research. The methods proposed in this work are based on two different concepts: one involves melting the polymer and mixing in the lithium salt (referred to as melt-mixing), while the other two techniques make use of water as a medium to carry and incorporate the salt in the polymer chains. This has been performed on Arnitel pellets (method named water soaking) and on thin films of the same material (referred to as thin film soaking). The water can then be removed by complete drying. Samples produced through melt-mixing and water soaking have then undergone hot pressing and thus thin (150-200µm) free-standing electrolytes have successfully been prepared. DSC and electrochemical analysis such as impedance measurements between room temperature and approximately 65°C, cyclic voltammetry and lithium plating experiments are presented. The samples prepared during this research proved to have room temperature conductivity as high as 10-5 S/cm. Electrochemical stability seems instead to be an issue in the lower voltage, but this is ascribed to the inherent behaviour between the lithium electrolyte and seems to be independent of the production method used. Such electrochemical results are aligned with the internal DSM data on samples produced via the solvent route: it is therefore possible to consider the proposed production routes as feasible alternatives for cheaper, safer and more environmentally friendly methods to produce Arnitel-based solid-state electrolytes for lithium ion batteries.Material Science and EngineeringMechanical, Maritime and Materials Engineerin
Profiled membranes as replacement for non-conducting spacers in a Concentration Gradient Flow Battery
No full textThe number of sustainable electrical energy sources is growing rapidly. These energy sources have a fluctuating and irregular pattern over time. Therefore, electricity storage is needed in the nearby future. The Concentration Gradient Flow Battery (CGFB), which uses the Blue Energy technology as a storage mechanism, has a promising market potential. Advantages among others are low cost and a small impact on the environment. This battery is currently under development by AquaBattery. However, for the CGFB to be cost competitive with other storage technologies, it needs further improvement. A new stack design with integrated profiled membranes may be such an improvement. To research the viability of profiled membranes a Design Science (DS) approach was used. The DS approach distinguishes four phases: conceptualization, experimentation, implementation, and evaluation. The results showed the differences in effects on CGFB performance between the profiled membranes and non-conducting spacers. The profiled membranes were then integrated in a new stack design and experimentally tested on a larger scale. Finally, this thesis formulates guidelines for further research of the CGFB. In doing so, it can help AquaBattery to achieve its goals of making, scaling-up and selling a large amount of batteries in the upcoming years.Electrical Engineering | Sustainable Energy Technolog
Reviving the rock-salt phases in Ni-rich layered cathodes by mechano-electrochemistry in all-solid-state batteries
No full textThe rock-salt phase (RSP) formed on the surface of Ni-rich layered cathodes in liquid-electrolyte lithium-ion batteries is conceived to be electrochemically "dead". Here we show massive RSP forms in the interior of LiNixMnyCo(1−x-y)O2 (NMC) crystals in sulfide based all solid state batteries (ASSBs), but the RSP remains electrochemically active even after long cycles. The RSP and the layered structure constitute a two-phase mixture, a material architecture that is distinctly different from the RSP in liquid electrolytes. The tensioned layered phase affords an effective percolation channel into which lithium is squeezed out of the RSPs by compressive stress, rendering the RSPs electrochemically active. Consequently, the ASSBs with predominant RSP in the NMC cathode deliver remarkable long cycle life of 4000 cycles at high areal capacity of 4.3 mAh/cm2. Our study unveils distinct mechano-electrochemistry of RSPs in ASSBs that can be harnessed to enable high energy density and durable ASSBs.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Storage of Electrochemical Energ
Towards High Energy Density Anode-less Lithium Metal Batteries: A Study of Lithium Dendrites Suppression and Elimination
No full textRechargeable Li-ion batteries for the market of electrical vehicles, portable equipment for entertainment, computing and telecommunication surge for the past decades, but the increasing demands introduce great challenges towards future battery systems that require higher energy and power density, improved safety as well as a longer lifespan. Lithium metal batteries can deliver higher energy densities compared with commercialized LIBs but the practical applications have been hindered due to the growth of lithium dendrites in liquid lithium metal batteries. The uncontrollable dendrite leads to the repeated formation of solid electrolyte interphase, irreversible capacity loss, short circuits, and safety hazards with liquid electrolytes. Compared to liquid electrolytes, solid-state electrolytes might be a better choice, but the reliance of ionic diffusion at the contact of solid particles is crucial presenting a major challenge. Moreover, the effective use of high capacity cathodes in combination with Li metal in a solid-state battery is another big challenge for future battery development. Therefore, to unlock the full potential of LMBs with high energy density and safe operation, it is imperative to devote efforts in solid-state batteries design. This thesis aims to search effective methods for enabling safe and high-energy-density solid-state Li metal batteries, starting from the developments of new concepts in liquid-based batteries and heading for an anode less Li metal solid-state battery configuration step by step
- …
