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Ex-situ and In-situ Soft X-Ray Spectro-Microscopy Studies of Manganese Oxide Electrodes for Energy Storage ApplicationsEraky, Haytham January 2024 (has links)
Energy storage systems such as batteries and supercapacitors store electrical energy in the form of chemical energy and release it when required. Among the various electrode materials, manganese oxides (MnOx) are promising electrode materials for these devices. Despite its outstanding theoretical capacitance, Mn-based oxide electrodes have several limitations that impede their electrochemical performance. Understanding how the charges are efficiently stored in the electrodes or across the electrode/electrolyte interface is crucial for developing advanced electrode material in the field of energy storage applications.
The goal of my thesis is to develop and apply synchrotron-based scanning transmission X-ray microscopy (STXM) to investigate changes in the oxidation state of Mn and their spatial distributions in MnOx electrodes in the context of energy storage and release. To achieve high- precision qualitative and quantitative STXM identification and mapping of different MnOx species, calibrated and high-quality reference Mn 2p and O 1s NEXAFS (near edge X-ray absorption fine structure) spectra were measured. In collaboration with Wenjuan Yang and her PhD supervisor, Prof. Igor Zhitomirsky, I performed ex-situ STXM studies on Mn3O4-based supercapacitor electrode materials to investigate the influence of different synthesis methods and activation protocols on the charging behavior and capacitance performance. In collaboration with Pablo Ingino and his supervisor, Prof. Martin Obst (Bayreuth University), and my colleague, Dr. Chunyang Zhang, I helped develop a three-electrode, microfluidic-based flow electrochemical device for in-situ STXM. This device was used to electrodeposit MnO2 on the working electrode (WE) and track the oxidation state and morphological changes by STXM while scanning the potential of the cell in different electrolyte pH. The in-situ STXM studies showed a spontaneous reduction of the initially deposited MnO2 resulting from the local pH change at the WE. Additionally, a significant change from a quasi-uniform MnO2 film to a dendritic MnO2 structure was observed at oxidative potential. This dendritic growth resulted from dissolution/redeposition of MnO2 during charging/discharging processes, indicating a partial reversibility of dissoluble Mn species. The ex-situ and in-situ STXM studies I performed provide mechanistic insights that will help further improve Mn oxides-based electrodes and their applications as energy storage devices. / Thesis / Doctor of Philosophy (PhD)
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DEVELOPMENT OF BATTERIES FOR IMPLANTABLE APPLICATIONSPurushothaman, Bushan K. 30 June 2006 (has links)
No description available.
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Preparation and Electrochemical Testing of Flexible Carbon Nanofiber Electrodes from ElectrospinningBeach, Jeremy 04 December 2017 (has links)
The purpose of this research project was to determine the processing conditions necessary for preparing flexible carbon nanofiber electrodes by electrospinning and to explore various applications for those electrodes. It was found that by varying only the relative humidity while electrospinning a poly(acrylonitrile) precursor, fragile or flexible freestanding carbon nanofiber electrodes were prepared. The relative humidity during electrospinning controlled the fiber diameter, the bulk porosity of the material, and flexibility of the final carbon electrode. Higher porosity mats electrospun in a high relative humidity environment prevented fiber sintering, which if not minimized, resulted in non-flexible carbon electrodes. Both flexible and fragile electrodes were freestanding, binderless, and collectorless. Additionally, they required no further processing before use and were 100 wt.% active material. When cycled galvanostatically as a lithium ion battery anode, the flexible electrode exhibited a specific capacity of 379 mAH g-1 at the 100th cycle and capacity retention was 97.4% relative to the fifth cycle. When applied as an active material support electrode for lithium ion battery cathodes, the carbon support was successfully utilized with both micron and nano structured active material and cycled for 100 cycles with limited capacity loss. The same electrodes were also found to be a viable replacement for Pt electrode based actuators/artificial muscles. However, this application requires much further research to understand better the required processing and effects of the physical properties of the electrode on actuator performance. In addition to this, the flexible electrodes have a wide variety of other potential applications including, electrochemical storage and conversion devices, chemical sensing, and filtration. The focus of this work was electrochemical storage and conversion devices in the form of lithium ion battery anodes and cathodes as well as ionic polymer composite actuators. / PHD
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Separator-free rechargeable lithium ion cells produced by the extrusion lamination of polymer gel electrolytesWard, Ian M., Kaschmitter J,J., Thompson, Glen P., Wellings, Simon C., Hubbard, H.V.St.A., Wang, H.P. January 2006 (has links)
No / Polymer gel electrolytes (PGE) based on polyvinylidene fluoride (PVDF), lithium salts and appropriate solvent systems, developed at Leeds University, have been shown to form tough rigid films with conductivities approaching 10¿2 S cm¿1. A continuous process has now been developed for the construction of rechargeable lithium cells by extruding the PGE as a melt and directly laminating between the anode and cathode electrodes. On cooling, the solid PGE acts as electrolyte and separator and binds the cell laminate together from within requiring no external case. This process has been successfully applied for the fabrication of cells with electrodes developed by SpectraPower Inc. in a commercial process enabling cell laminates with PGE thickness less than 0.1 mm and with energy densities approaching 170 Wh kg¿1. A prototype manufacturing facility has been set up to produce rechargeable cells of high specific capacity and high energy density. Future developments will enable rechargeable lithium ion cells to be produced on a continuous process as flat sheets opening the way for novel battery geometries.
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Materials Design toward High Performance Electrodes for Advanced Energy Storage ApplicationsCheng, Qingmei January 2018 (has links)
Thesis advisor: Udayan Mohanty / Rechargeable batteries, especially lithium ion batteries, have greatly transformed mobile electronic devices nowadays. Due to the ever-depletion of fossil fuel and the need to reduce CO2 emissions, the development of batteries needs to extend the success in small electronic devices to other fields such as electric vehicles and large-scale renewable energy storage. Li-ion batteries, however, even when fully developed, may not meet the requirements for future electric vehicles and grid-scale energy storage due to the inherent limitations related with intercalation chemistry. As such, alternative battery systems should be developed in order to meet these important future applications. This dissertation presents our successes in improving Li-O2 battery performance for electric vehicle application and integrating a redox flow battery into a photoelectrochemical cell for direct solar energy storage application. Li-O2 batteries have attracted much attention in recent years for electric vehicle application since it offers much higher gravimetric energy density than Li-ion ones. However, the development of this technology has been greatly hindered by the poor cycling performance. The key reason is the instability of carbon cathode under operation conditions. Our strategy is to protect the carbon cathode from reactive intermediates by a thin uniform layer grown by atomic layer depostion. The protected electrode significantly minimized parasitic reactions and enhanced cycling performance. Furthermore, the well-defined pore structures in our carbon electrode also enabled the fundamental studies of cathode reactions. Redox flow batteries (RFB), on the other hand, are well-suited for large-scale stationary energy storage in general, and for intermittent, renewable energy storage in particular. The efficient capture, storage and dispatch of renewable solar energy are major challenges to expand solar energy utilization. Solar rechargeable redox flow batteries (SRFBs) offer a highly promising solution by directly converting and storing solar energy in a RFB with the integration of a photoelectrochemical cell. One major challenge in this field is the low cell open-circuit potential, mainly due to the insufficient photovoltages of the photoelectrode systems. By combining two highly efficient photoelectrodes, Ta3N5 and Si (coated with GaN), we show that a high-voltage SRFB could be unassistedly photocharged and discharged with a high solar-to-chemical efficiency. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
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Continuum Level Physics-based Model on Understanding and Optimizing the Lithium Transport in High-Energy-Density LIB/LMB ElectrodesHui, Zeyu January 2022 (has links)
As an efficient means of energy storage, rechargeable batteries, especially the lithium-ion batteries (LIBs) have been a vital component in solving the upcoming energy crisis and environmental problems. Recently, the development of electric vehicle market puts new requirement on the next generation LIBs, including superior energy density, safety and cycling stability, etc. Compared with experimental investigation, Physics-based models provide a surrogate method to not only tackle the underlying physics of the complex battery system, but also optimize the design of battery systems. In this thesis, I will show how I use the physics-based continuum model and cooperate with some experimental methods to understand the lithium transport phenomena inside the multiscale battery electrode systems, based on which the models are then applied to guide the experimental optimization of battery electrode design and to quantitively understand the degradation of high-performance electrodes.
The thesis is divided into three parts. First part (Chapter 2) presents a systematical model selection study on the multiscale LiNi₀.₃₃Mn₀.₃₃Co₀.₃₃O₂ (NMC₁₁₁) electrode. Discharge and voltage relaxation curves, interrogated with theory, are used to distinguish between lithium transport impedance that arise on the scale of the active crystal and on the scale of agglomerates (secondary particles) comprised of nanoscale crystals. Model-selection algorithms are applied to determine that the agglomerate scale transport is dominant in the NMC₁₁₁ electrode studied here. This study not only discovers the dominant length scale for lithium transport, but also provide a validated model (the agglomerate model) for later study.
The second part (Chapter 3 & 4) talks about understanding & optimization of ion transport in porous electrodes. In Chapter 3, multi-scale physics-based models for different active material systems, which have been parameterized and validated with discharge experiments, are optimized by varying porosity and mass loading to achieve maximum volumetric energy density. The optimization results show that with a re-scaling of the current rate, the optimal results follow a general design rule that is captured in a convenient correlation. Chapter 4 extends the model to simulate the performance of advanced electrode architectures utilizing aligned channels, by quantifying the impact of aligned channel electrode structures on cell rate capability. Then the optimization algorithm in Chapter 3 is applied to these aligned-channel electrodes.
The final part (Chapter 5) shows how I use the physics-based model to quantitatively analyze the battery degradation. The validated model is applied to cycling data to obtain parameter estimates indicative of degradation modes. It’s found that growth rates of interfacial impedance and active material loss are greater at 4.5 V, as might be expected. However, when charged to 4.5V, degradation rates are lower at a cycling C-rate of 1.0 h⁻¹ than at 0.5 h⁻¹. Once performance changes are quantified, we use further simulation to evaluate the contribution of individual degradation modes to fade of cell performance metric such as capacity, power density, and energy density.
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Materials Design for Lithium Batteries with High Energy DensityJin, Tianwei January 2024 (has links)
Lithium-ion batteries (LIBs) play a pivotal role in advancing transportation electrification, offering a crucial solution to address climate change and fossil fuel depletion, but the current energy density of LIBs remains unsatisfying, limiting electric transportation range. To address this limitation, extensive efforts focus on developing novel electrode materials, including high-voltage cathodes and high-specific-capacity electrodes. However, the pursuit of higher energy densities introduces safety concerns due to the higher possibility of thermal runaway and flammable nature of conventional liquid electrolytes. In this doctoral thesis, I will present several innovative strategies for high-performance lithium battery systems aimed at enhancing the mileage of electric transportation without compromising or even enhancing safety.
The first part (Chapter 3) discusses a novel design for structural batteries. Structural batteries are the energy storage devices with enhanced mechanical properties integrated as structural components in vehicles to reduce vehicle weights and increase mileage. Through the development of a scalable and feasible tree-root-like lamination at the electrode/separator interface, an 11-fold enhancement in the flexural modulus of pouch cells is achieved, and the underlying mechanism is revealed by finite element simulations. This lamination has a minimal impact on the electrochemical performance of LIBs and the smallest reported specific energy reduction of ~3% in structural batteries. The prototype "electric wings" showcases stable flight for an aircraft model, highlighting the effectiveness and scalability of engineering interfacial adhesion in developing structural batteries with superior mechanical and electrochemical properties.
The second part (Chapter 4) presents a design rule for polymer electrolytes to enhance lithium metal battery safety. Lithium metal batteries are attractive for electric transportation due to their high energy densities, but their application is hindered by the safety concerns from dendrite growth. In this work, we observe that if the compositions of polyethylene oxide (PEO) electrolytes are near the boundary between amorphous and polymer-rich regions, concentration polarization in electrolytes will induce a phase transformation and create a PEO-rich phase at the electrode surface. This new phase is mechanically rigid with a Young’s modulus of ∼1-3 GPa so that it can suppress lithium dendrites, which allows Li/PEO/LiFePO₄ cells with such a phase transformation demonstrate superior lithium reversibility without dendrites for 100 cycles.
The third part (Chapter 5) proposes an innovative cathode design for all-solid-state Li-S batteries (ASSLSBs) which have ultra-high energy densities and enhanced battery safety. However, conventional cathode designs of filling sulfur in carbon hosts suffer from accelerated decomposition of electrolytes and sulfur detachment, leading to significant capacity loss. As a solution, I propose that nonconductive polar hosts allow long cycling life of ASSLSBs via stabilizing the adjacent electrolytes and bonding sulfur/Li₂S steadily to avoid detachment. By using a mesoporous SiO₂host filled with 70 wt.% sulfur as the cathode, we demonstrate steady cycling in ASSLSBs with a capacity reversibility of 95.1% in the initial cycle and a discharge capacity of 1446 mAh g-1 after 500 cycles at C/5.
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Studies On Lead-Acid, Nickel-Based And Silver-Zinc Rechargeable BatteriesHariprakash, B 05 1900 (has links) (PDF)
No description available.
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Silicon Inverse Opal-based Materials as Electrodes for Lithium-ion Batteries: Synthesis, Characterisation and Electrochemical PerformanceEsmanski, Alexei 19 January 2009 (has links)
Three-dimensional macroporous structures (‘opals’ and ‘inverse opals’) can be produced by colloidal crystal templating, one of the most intensively studied areas in materials science today. There are several potential advantages of lithium-ion battery electrodes based on inverse opal structures. High electrode surface, easier electrolyte access to the bulk of electrode and reduced lithium diffusion lengths allow higher discharge rates. Highly open structures provide for better mechanical stability to volume swings during cycling.
Silicon is one of the most promising anode materials for lithium-ion batteries. Its theoretical capacity exceeds capacities of all other materials besides metallic lithium. Silicon is abundant, cheap, and its use would allow for incorporation of microbattery production into the semiconductor manufacturing. Performance of silicon is restricted mainly by large volume changes during cycling.
The objective of this work was to investigate how the inverse opal structures influence the performance of silicon electrodes. Several types of silicon-based inverse opal films were synthesised, and their electrochemical performance was studied.
Amorphous silicon inverse opals were fabricated via chemical vapour deposition and characterised by various techniques. Galvanostatic cycling of these materials confirmed the feasibility of the approach taken, since the electrodes demonstrated high capacities and decent capacity retentions. The rate performance of amorphous silicon inverse opals was unsatisfactory due to low conductivity of silicon. The conductivity of silicon inverse opals was improved by crystallisation. Nanocrystalline silicon inverse opals demonstrated much better rate capabilities, but the capacities faded to zero after several cycles.
Silicon-carbon composite inverse opal materials were synthesised by depositing a thin layer of carbon via pyrolysis of a sucrose-based precursor onto the silicon inverse opals in an attempt to further increase conductivity and achieve mechanical stabilisation of the structures. The amount of carbon deposited proved to be insufficient to stabilise the structures, and silicon-carbon composites demonstrated unsatisfactory electrochemical behaviour.
Carbon inverse opals were coated with amorphous silicon producing another type of macroporous composites. These electrodes demonstrated significant improvement both in capacity retentions and in rate capabilities. The inner carbon matrix not only increased the material conductivity, but also resulted in lower silicon pulverisation during cycling.
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Silicon Inverse Opal-based Materials as Electrodes for Lithium-ion Batteries: Synthesis, Characterisation and Electrochemical PerformanceEsmanski, Alexei 19 January 2009 (has links)
Three-dimensional macroporous structures (‘opals’ and ‘inverse opals’) can be produced by colloidal crystal templating, one of the most intensively studied areas in materials science today. There are several potential advantages of lithium-ion battery electrodes based on inverse opal structures. High electrode surface, easier electrolyte access to the bulk of electrode and reduced lithium diffusion lengths allow higher discharge rates. Highly open structures provide for better mechanical stability to volume swings during cycling.
Silicon is one of the most promising anode materials for lithium-ion batteries. Its theoretical capacity exceeds capacities of all other materials besides metallic lithium. Silicon is abundant, cheap, and its use would allow for incorporation of microbattery production into the semiconductor manufacturing. Performance of silicon is restricted mainly by large volume changes during cycling.
The objective of this work was to investigate how the inverse opal structures influence the performance of silicon electrodes. Several types of silicon-based inverse opal films were synthesised, and their electrochemical performance was studied.
Amorphous silicon inverse opals were fabricated via chemical vapour deposition and characterised by various techniques. Galvanostatic cycling of these materials confirmed the feasibility of the approach taken, since the electrodes demonstrated high capacities and decent capacity retentions. The rate performance of amorphous silicon inverse opals was unsatisfactory due to low conductivity of silicon. The conductivity of silicon inverse opals was improved by crystallisation. Nanocrystalline silicon inverse opals demonstrated much better rate capabilities, but the capacities faded to zero after several cycles.
Silicon-carbon composite inverse opal materials were synthesised by depositing a thin layer of carbon via pyrolysis of a sucrose-based precursor onto the silicon inverse opals in an attempt to further increase conductivity and achieve mechanical stabilisation of the structures. The amount of carbon deposited proved to be insufficient to stabilise the structures, and silicon-carbon composites demonstrated unsatisfactory electrochemical behaviour.
Carbon inverse opals were coated with amorphous silicon producing another type of macroporous composites. These electrodes demonstrated significant improvement both in capacity retentions and in rate capabilities. The inner carbon matrix not only increased the material conductivity, but also resulted in lower silicon pulverisation during cycling.
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