Organic materials for the improvement and understanding of electrochemical devices

The contents of this thesis focus on how organic materials can be applied to improve Li+ based batteries. There is specific focus mostly on cathode materials and a single project involving electrolytes. For cathodes the main focus is how quinone polymers can be applied as Li+ cathodes and results in a 4e- cathode with record breaking capacity. We then go on to do some minor mechanistic and fundamental studies. The second cathode focus is how organic materials can augment existing technology. In this regard we investigate how alkyl phosphonates can form monolayer coating on Lithium Manganese Oxide cathode particles to suppress Mn dissolution during cycling. Finally we modify Li-S cathodes by chemically crosslinking poly-sulfide with conductive poly aniline to increase cycle life and cathode sulfur loadings. To improve Li+ electrolytes we demonstrate that persistently porous organic cages can serve as host structures to form solid-liquid electrolyte nano-composites. Taken together this work demonstrates the innovative impact Organic materials can have on battery technology

Autonomous Light Management in Flexible Photoelectrochromic Films Integrating High Performance Silicon Solar Microcells

Commercial smart window technologies for dynamic light and heat management in building and automotive environments traditionally rely on electrochromic (EC) materials powered by an external source. This design complicates building-scale installation requirements and substantially increases costs for applications in retrofit construction. Self-powered photoelectrochromic (PEC) windows are an intuitive alternative wherein a photovoltaic (PV) material is used to power the electrochromic device, which modulates the transmission of the incident solar flux. The PV component in this application must be sufficiently transparent and produce enough power to efficiently modulate the EC device transmission. Here, we propose Si solar microcells (μ-cells) that are i) small enough to be visually transparent to the eye, and ii) thin enough to enable flexible PEC devices. Visual transparency is achieved when Si μ-cells are arranged in high pitch (i.e. low-integration density) form factors while maintaining the advantages of a single-crystalline PV material (i.e., long lifetime and high performance). Additionally, the thin dimensions of these Si μ-cells enable fabrication on flexible substrates to realize these flexible PEC devices. The current work demonstrates this concept using WO₃ as the EC material and V₂O₅ as the ion storage layer, where each component is fabricated via sol-gel methods that afford improved prospects for scalability and tunability in comparison to thermal evaporation methods. The EC devices display fast switching times, as low as 8 seconds, with a modulation in transmission as high as 33%. Integration with two Si μ-cells in series (affording a 1.12 V output) demonstrates an integrated PEC module design with switching times of less than 3 minutes, and a modulation in transmission of 32% with an unprecedented EC:PV areal ratio

Autonomous Light Management in Flexible Photoelectrochromic Films Integrating High Performance Silicon Solar Microcells

Commercial smart window technologies for dynamic light and heat management in building and automotive environments traditionally rely on electrochromic (EC) materials powered by an external source. This design complicates building-scale installation requirements and substantially increases costs for applications in retrofit construction. Self-powered photoelectrochromic (PEC) windows are an intuitive alternative wherein a photovoltaic (PV) material is used to power the electrochromic device, which modulates the transmission of the incident solar flux. The PV component in this application must be sufficiently transparent and produce enough power to efficiently modulate the EC device transmission. Here, we propose Si solar microcells (μ-cells) that are i) small enough to be visually transparent to the eye, and ii) thin enough to enable flexible PEC devices. Visual transparency is achieved when Si μ-cells are arranged in high pitch (i.e. low-integration density) form factors while maintaining the advantages of a single-crystalline PV material (i.e., long lifetime and high performance). Additionally, the thin dimensions of these Si μ-cells enable fabrication on flexible substrates to realize these flexible PEC devices. The current work demonstrates this concept using WO₃ as the EC material and V₂O₅ as the ion storage layer, where each component is fabricated via sol-gel methods that afford improved prospects for scalability and tunability in comparison to thermal evaporation methods. The EC devices display fast switching times, as low as 8 seconds, with a modulation in transmission as high as 33%. Integration with two Si μ-cells in series (affording a 1.12 V output) demonstrates an integrated PEC module design with switching times of less than 3 minutes, and a modulation in transmission of 32% with an unprecedented EC:PV areal ratio

Organic materials for the improvement and understanding of electrochemical devices

The contents of this thesis focus on how organic materials can be applied to improve Li+ based batteries. There is specific focus mostly on cathode materials and a single project involving electrolytes. For cathodes the main focus is how quinone polymers can be applied as Li+ cathodes and results in a 4e- cathode with record breaking capacity. We then go on to do some minor mechanistic and fundamental studies. The second cathode focus is how organic materials can augment existing technology. In this regard we investigate how alkyl phosphonates can form monolayer coating on Lithium Manganese Oxide cathode particles to suppress Mn dissolution during cycling. Finally we modify Li-S cathodes by chemically crosslinking poly-sulfide with conductive poly aniline to increase cycle life and cathode sulfur loadings. To improve Li+ electrolytes we demonstrate that persistently porous organic cages can serve as host structures to form solid-liquid electrolyte nano-composites. Taken together this work demonstrates the innovative impact Organic materials can have on battery technology.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste

RU Leaks

Jersey roots, and global reach of free speech on the InternetSpring 201

2-Pyridone and Derivatives: Gas-Phase Acidity, Proton Affinity, Tautomer Preference, and Leaving Group Ability

The fundamental properties of the parent and substituted 2-pyridones (2-pyridone, 3-chloro-2-pyridone, and 3-formyl-2-pyridone) have been examined in the gas phase using computational and experimental mass spectrometry methods. Newly measured acidities and proton affinities are reported and used to ascertain tautomer preference. These particular substrates (as well as additional 3-substituted pyridones) were chosen in order to examine the correlation between leaving group ability and acidity for moieties that allow resonance delocalization versus those that do not, which is discussed herein

Solid–Liquid Lithium Electrolyte Nanocomposites Derived from Porous Molecular Cages

We demonstrate that solid–liquid nanocomposites derived from porous organic cages are effective lithium ion electrolytes at room temperature. A solid–liquid electrolyte nanocomposite (SLEN) fabricated from a LiTFSI/DME electrolyte system and a porous organic cage exhibits ionic conductivity on the order of 1 × 10^–3 S cm^–1. With an experimentally measured activation barrier of 0.16 eV, this composite is characterized as a superionic conductor. Furthermore, the SLEN displays excellent oxidative stability up to 4.7 V vs Li/Li⁺. This simple three-component system enables the rational design of electrolytes from tunable discrete molecular architectures

Three-dimensional mesostructures as high-temperature growth templates, electronic cellular scaffolds, and self-propelled microrobots

Exploiting advanced 3D designs in micro/nanomanufacturing inspires potential applications in various fields including biomedical engineering, metamaterials, electronics, electromechanical components, and many others. The results presented here provide enabling concepts in an area of broad, current interest to the materials community––strategies for forming sophisticated 3D micro/nanostructures and means for using them in guiding the growth of synthetic materials and biological systems. These ideas offer qualitatively differentiated capabilities compared with those available from more traditional methodologies in 3D printing, multiphoton lithography, and stress-induced bending––the result enables access to both active and passive 3D mesostructures in state-of-the-art materials, as freestanding systems or integrated with nearly any type of supporting substrate