This thesis is dedicated to developing three different types of ferrocene-containing polymers for organic lithium-ion battery and resistive memory applications. Chapter 1 gives an overview of organic cathode-active materials, polymeric resistive memories and ferrocene-containing polymers. Furthermore, the previously reported applications of ferrocene-containing polymeric systems in electrochemical energy storage and electronical memory devices were also comprehensively summarized. In chapter 2, conjugated ferrocene-containing side-chain metallopolymers PFcFE1, PFcFE2, PFcFE3 and PFcFE4 were designed and synthesized via Sonogashira cross-coupling polycondensation. The charging-discharging processes of triphenyamine-based PFcFE1 and thiophene-modified PFcFE4 have been successfully studied as cathode materials. PFcFE1 composite electrode showed a capacity of 90 mAh g-1 and the cathode composed of PFcFE4 retained over 90% of the initial capacity after 100 charging-discharging cycles at 10 C. These results demonstrate the great potentials of these ferrocene-containing side-chain polymers as active cathode materials for organic lithium-ion battery applicaitons. Besides, all prepared ferrocene-containing metallopolymers PFcFE1, PFcFE2, PFcFE3 and PFcFE4 also exhibited nonvolatile resistive switching behaviors with the flash memory effect of PFcFE1, PFcFE2 and PFcFE3 as well as the WORM memory feature of PFcFE4, indicating the easily tuned memory properties by changing the chemical structures of the active polymeric backbones. It is also worth noting that the ITO/PFcFE1/Al memory device showed a high ON/OFF current ratio of 103 to 104, a low switch-on voltage of -1.0 V, a long retention time of 1000 s and a large read cycle number up to 105, which is superior to other reported ferrocene-containing memory examples. Chapter 3 focuses on the development of non-conjugated ferrocene-containing copolymers PVFVM1, PVFVM1-1, PVFVM2, PVFVM3, PVFVM4, PVFVM5 and PVFVM6 based on different heteroaromatic moieties which were prepared by AIBN initiated chain addition polymerization. The as-prepared copolymers PVFVM1 and PVFVM1-1 exhibited electrochemical characteristics of both ferrocene and triphenylamine pendants with reversible multiple redox waves at the half potentials of E1/2 = --0.06, 0.30, and 0.42 V (vs. Fc/Fc+). Notably, the composite electrode based on PVFVM1 afforded a discharge capacity of 102 mAh g--1 at 10 C, corresponding to 98% of its theoretical capacity. The cycle endurances of the active polymer electrodes composed of PVFVM1 or PVFVM1-1 were both evaluated for over 50 numbers and no significant capacity reduction over cycles were observed. On the other hand, initial I-V results of memory devices based on PVFVM1, PVFVM1-1, PVFVM2, PVFVM3, PVFVM4 and PVFVM6 also revealed their huge potentials in electronic information storage. The stability and reproducibility of the corresponding memory devices based on these materials will be futher evaluated in the near future. We used 1,1'-ferrocenediboronic acid bis(pinacol) ester to develop conjugated ferrocene-containing main-chain metallopolymers in chapter 4. All these rational designed metallopolymers FcMMP1, FcMMP2, FcMMP3 and FcMMP4 with one or two ferrocene moieties were produced via Suzuki cross-coupling polycondensation. Their structural information, molecular masses, photophysical features and thermal properties have been well studied. Electrochemical performances of the formed polymers were also examined to clarify their potential as cathode-active materials. Other charge-storage characteristics and switching behaviors of these prepared ferrocene-containing main-chain metallopolymers for organic battery and memory applications are under further investigation.

One application for photovoltaic (PV) technology is in providing electricity for educational aids, in developing areas remote from grid supply. Technical, social and economic aspects of this option are investigated, in local context, by examining the use of small PV systems to power educational television and video in secondary schools in Bophuthatswana. Technical performance was assessed through monitoring PV system behaviour and climatic variables over an extended period, using remote data-capture techniques at a demonstration site. Modelling provided for further prediction of performance in nonobserved conditions. Social and educational aspects of the schools television project were investigated through interviews with educationists, planners, project administrators and a limited sample of teachers and pupils in Bophuthatswana. Overall conclusions are that PV systems can provide a reliable and technically appropriate solution to the problem of powering light electrical loads in off-grid schools. Levelised unit energy costs can be acceptable if PV systems are critically sized, and if there is close match between designed capacity and actual load energy demand. If this is not the case - as in Bophuthatswana school systems - unit energy costs may be very high. Organisational features of project implementation and inadequate central resources, particularly for delivering appropriate educational software to schools, have impaired the potential of the project, and the equipment in schools is under-utilised. Proceeding from an inductive performance analysis of the monitored system, a PV system performance model was developed, in order to assess the optimum sizing of components in small stand-alone photovoltaic systems in such applications, and to judge the sizing of the systems installed. The model is based upon critical runs of adverse weather, leading to-wards system loss of power to load. It predicts the minimum insolation required to avoid system loss of power to load over runs of days, and compares this with percentiles for plane-of-array insolation over runs of days, derived from long term · hourly weather station records. The approach allows development of a loss of power probability (LOPP) sizing methodology which preserves the run-length characteristics of local climatic data. Sizing predictions from this method are compared with other sizing methodologies, and are used to indicate design savings possible for the monitored systems. The proposed critical-run LOPP sizing method has potential for incorporation in a microcomputer-based sizing tool, suitable for more accurate design of photovoltaic systems with battery storage in local applications.

Sodium-ion batteries (SIBs) are considered as a promising alternative to lithium-ion batteries (LIBs) for large-scale renewable energy storage units due to the abundance of sodium resource and its low cost. However, the development of anode materials for SIBs to date has been mainly limited to some traditional anodes for LIBs, such as carbonaceous materials. SnSe2 is a member of two dimensional layered transition metal dichalcogenide (TMD) family, which has been predicted to have high theoretical capacity as anode material for sodium ion batteries (756 mAh g-1), thanks to its layered crystal structure. Yet, there have been no studies on using SnSe2 as Na ion battery anode. In this thesis, we developed a simple synthesis method to prepare pure SnSe2 nanosheets, employing N2 saturated NaHSe solution as a new selenium source. The SnSe2 2D sheets achieve theoretical capacity during the first cycle, and a stable and reversible specific capacity of 515 mAh g-1 at 0.1 A g-1 after 100 cycles, with excellent rate performance. Among all of the reported transition metal selenides, our SnSe2 sample has the highest reversible capacity and the best rate performances. A combination of ex-situ high resolution transmission electron microscopy (HRTEM) and X-ray diffraction was used to study the mechanism of sodiation and desodiation process in this SnSe2, and to understand the reason for the excellent results that we have obtained. The analysis indicate that a combination of conversion and alloying reactions take place with SnSe2 anodes during battery operation, which helps to explain the high capacity of SnSe2 anodes for SIBs compared to other binary selenides. Density functional theory was used to elucidate the volume changes taking place in this important 2D material.

Thesis advisor: Udayan Mohanty / Thesis advisor: Dunwei Wang / With the fast development of society, the demand for batteries has been increasing dramatically over the years. To satisfy the ever-increasing demand for high energy density, different chemistries were explored. From the first-generation lead–acid batteries to the state-of-the-art LIBs (lithium ion batteries), the energy density has been improved from 40 to over 200 Wh kg⁻¹. However, the development of LIBs has approached the upper limit. Electrode materials based on insertion chemistry generally deliver a low capacity of no more than 400 mAh/g. To break the bottleneck of current battery technologies, new chemistries are needed. Moving from the intercalation chemistry to conversion chemistry is a trend. The conversion electrode materials feature much higher capacity than the conventional intercalation-type materials, especially for the O₂ cathode and Li metal anode. The combination of these two can bring about a ten-folds of energy density increase to the current LIBs. Moreover, to satisfy the safety requirements, either using non-flammable electrolytes to reduce the safety risk of Li metal anode or switch to dendrite-free Mg anode is a good strategy toward high energy density batteries. First, to enable the conversion-type O₂ cathode, a wood-derived, free-standing porous carbon electrode was demonstrated and successfully be applied as a cathode in Li-O₂ batteries. The spontaneously formed hierarchical porous structure exhibits good performance in facilitating the mass transport and hosting the discharge products of Li₂O₂. Heteroatom (N) doping further improves the catalytic activity of the carbon cathode with lower overpotential and higher capacity. Next, to solve the irreversible Li plating/stripping and safety issues related with Li metal anode, we introduced O₂ as additives to enable Li metal anode operation in non-flammable triethyl phosphate (TEP) electrolyte. The electrochemically induced chemical reaction between O₂- derived species and TEP solvent molecules facilitated the beneficial SEI components formation and effectively suppressed the TEP decomposition. The promise of safe TEP electrolyte was also demonstrated in Li-O₂ battery and Li-LFP battery. If we think beyond Li chemistries, Mg anode with dendrite-free property can be a promising candidate to further reduce the safety concerns while remaining the high energy density advantage. Toward the end of this thesis, we developed a thin film metal–organic framework (MOF) for selective Mg²⁺ transport to solve the incompatibility issues between the anode and the cathode chemistry for Mg batteries. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

L'invention des batteries au lithium (LIBs) a déclenché le déploiement massif de technologies portables et encourage de nos jours l'électrification du transport. Ceci mène au besoin de LIBs avec une densité d'énergie encore plus importante, des temps de recharge plus court, un coût plus faible et une sécurité maximale. Dans ce contexte, cette thèse de doctorat se concentre sur la modélisation présentant un outil pour caractériser et simuler les performances de LIB sous des conditions dynamiques pour des applications de puissance. Un nouveau modèle mathématique représentant l'inertie de transport du lithium avec l'approche de Maxwell-Cattaneo-Vernotte est proposé. L'implication de ce modèle dans la simulation sur la réponse dynamique de LIBs sous des pulsations de courant est exploré. Ce modèle est construit avec une approche multi échelle et démontré pour des matériaux actifs de type graphite pour les électrodes négatives. Tout d'abord, un modèle analytique est développé pour extraire et caractériser la diffusion du lithium ainsi que l'inertie dans le matériau actif de l'expérience de PITT. Les valeurs extraites sont par la suite intégrées dans des modèles de demi-cellule pour calibrer la réponse expérimentale en courant. Une étude comparative des modèles p-2D et 3D réalisés de manière systématique. Les résultats montrent l'implication de la diffusion inter-particule sur la performance de LIB aussi bien que la dynamique onduleuse de transport du lithium dans la phase solide soulignant fortement l'inhomogénéité/anisotropie de la dispersion du lithium dans le graphite à une échelle macroscopique. Finalement, la faisabilité d'intégrer le modèle proposé dans un modèle de cellule complète est explorée / The invention of the lithium ion batteries (LIBs) triggered the massive deployment of portable technologies, and is nowadays encouraging the electrification of the transportation. This leads to the need of LIBs with even higher energy densities, shorter recharging times, lower cost and maximal safety. This PhD thesis focuses on computational modeling as a tool to characterize and simulate the LIB operation under dynamical conditions representative of power applications. It proposes a new mathematical model accounting for lithium transport inertia within the Maxwell-Cattaneo-Vernotte framework, and explores its implications for the simulation of the dynamical response of LIBs to current pulses. This model is built through a multiscale approach and demonstrated for graphitic active materials for negative electrodes. First, an analytical model is derived to extract and characterize lithium diffusion and inertia in the active material from PITT experiments. Extracted values are then used in a half cell model to fit experimental current evolution curves, through p-2D and 3D-resolved models which are comparatively investigated. The results show the implication of inter-particle diffusion on the performance of the LIB as well as the wavy lithium transport dynamics in the solid phase emphasizing the inhomogeneous/anisotropic lithium dispersion in the graphitic material at a macroscopic level. Finally, the feasibility of utilizing such a model for complete cell simulations is investigated

Lithium is a very attractive material for batteries. It has low redox potential (-3.04V vs SHE) and high theoretical capacity of 3860 mAh g-1. So, lithium batteries would have high energy density. During charging and discharging of the batteries, the interface between electrode and electrolyte changes as lithium is deposited or dissolved. If the deposition is dendritic, it can short circuit and cause failure of the battery. During dissolution of lithium from the electrode, pits can form on the surface and some part of lithium is detached. It is called dead lithium since it is not electrochemically active. Solid electrolyte and lithium metal interfaces are characterized by high interfacial resistance. The interface between electrode and electrolyte is critical to the safety and performance of lithium batteries. The aim of this research is to understand the evolution of interface between electrode and electrolyte as charging or discharging occurs. Three kinds of interfaces are considered, interface formed between intercalation anode and liquid electrolyte, interface of metal anode and liquid electrolyte and interface between metal anode and solid electrolyte.<br>Stringent performance and operational requirements in electric vehicles can push lithium-ion batteries toward unsafe conditions. Electroplating and possible dendritic growth are a cause for safety concern as well as performance deterioration in such intercalation chemistry-based energy storage systems. There is a need for better understanding of the morphology evolution due to electrodeposition of lithium on graphite anode surface, and the interplay between material properties and operating conditions. In this work, a mesoscale analysis of the underlying multi-modal interactions is presented to study the evolution of morphology due to lithium deposition on typical graphite electrode surfaces. It is found that electrodeposition is a complex interplay between the rate of reduction of Li ion and the intercalation of Li in the graphite anode. The morphology of the electrodeposited film changes from dendritic to mossy structures due to the surface diffusion of lithium on the electrodeposited film.<br>Dendritic deposition on lithium metal anode during charging poses a safety concern. During discharging, formation of dead lithium results in low Coulombic efficiency. In this work, a comprehensive understanding of the interface evolution leading to the formation of dead lithium is presented based on a mechanism-driven probabilistic analysis. Non-dendritic interface morphology is obtained under reaction controlled scenarios. Otherwise, this may evolve into a mossy, dendritic, whisker or needle-like structures with the main characteristic being the propensity for undesirable vertical growth. During discharging, pitted interface may be formed along with bulk dissolution. Surface diffusion is a key determinant controlling the extent of dead lithium formation, including a higher probability of the same when the effect of surface diffusion is comparable to that of ionic diffusion in the electrolyte and interface reaction.<br>One of the biggest advantages of solid electrolyte over liquid electrolyte is its mechanical rigidity which provides resistance to dendritic deposition. The electrodeposition at the interface of solid electrolyte and lithium metal anode will be affected by the nature of the interface formed between solid electrolyte and lithium metal, i.e. coherent, semi-coherent or incoherent depending on the misfit between the two crystal lattices. A coupled energetics and deposition mesoscale model is developed to investigate the nature of deposition and surface roughness of the deposition. The strength of interaction between metal anode surface and solid electrolyte surface at the interface is key in determining the roughness of the morphology during deposition. The energy is localized to region near the interface. With surface diffusion at the interface, the roughness of the interface as well as the energy near the interfacial region decreases.

Advancements in Li-ion batteries are needed especially for the development of electric vehicles and stationary energy storage. Prior research has shown mesoscale variations in electrode electronic conductive properties, which can cause capacity loss and uneven electrochemical behavior of Li-ion batteries. A micro-four-line probe (μ4LP) was used to measure electronic conductivity and contact resistance over mm-length scales in that prior work. This work describes improvements to overcome the challenge of unreliable surface contact between theμ4LP and the sample. Ultimately a second generation flexible probe called the micro-radial-surface probe (μ4LP) was designed and produced. The test fixture was also optimized to obtain consistent contact with the new measurement probe and to perform measurements at a lower force. The μ4LP was then used to study the effect of heterogeneity on calendering, which is the compression of electrode films to obtain a uniform thickness and desired porosity. The thickness, electronic conductivity and contact resistance of two cathodes and one anode were measured before and after calendering. The the spatial standard deviation divided by the mean was used as a measure of heterogeneity. The results show variability in conductive properties increased for two of the three samples after calendering, despite the increased uniformity in thickness of the electrodes. This suggests that additional quality control metrics are needed besides thickness to be able to identify uneven degradation and produce longer lasting batteries.

Advancements in Li-ion batteries are needed especially for the development of electric vehicles and stationary energy storage. Prior research has shown mesoscale variations in electrode electronic conductive properties, which can cause capacity loss and uneven electrochemical behavior of Li-ion batteries. A micro-four-line probe (μ4LP) was used to measure electronic conductivity and contact resistance over mm-length scales in that prior work. This work describes improvements to overcome the challenge of unreliable surface contact between theμ4LP and the sample. Ultimately a second generation flexible probe called the micro-radial-surface probe (μ4LP) was designed and produced. The test fixture was also optimized to obtain consistent contact with the new measurement probe and to perform measurements at a lower force. The μ4LP was then used to study the effect of heterogeneity on calendering, which is the compression of electrode films to obtain a uniform thickness and desired porosity. The thickness, electronic conductivity and contact resistance of two cathodes and one anode were measured before and after calendering. The the spatial standard deviation divided by the mean was used as a measure of heterogeneity. The results show variability in conductive properties increased for two of the three samples after calendering, despite the increased uniformity in thickness of the electrodes. This suggests that additional quality control metrics are needed besides thickness to be able to identify uneven degradation and produce longer lasting batteries.

Indiana University-Purdue University Indianapolis (IUPUI) / Recent innovations in portable electronics, electric vehicles and power generation by wind and solar have expanded the need for effcient battery storage. Lithium-ion batteries have been the frontline contender of battery storage yet are not able to match current demands. Alternatively, lithium-sulfur batteries are a promising technology to match the consumer demands. Elemental sulfur cathodes incur a variety of problems during cycling including the dissolution of intermediate lithium polysul- fides, an undesirable volume change (~ 80%) when completely reduced and a high dependence on liquid electrolyte, which quickly degrades the cell's available energy density. Due to these problems, the high theoretical capacity and energy density of lithium sulfur cells are unattainable. In this work, A new class of phenyl polysul- fides, C6H5SxC6H5(4 < x <6), are developed as liquid sulfur containing cathode materials. This technology was taken a step further to fulfill and emerging need for exible electronics in technology. Phenyl tetrasulfide (C6H5S4C6H5) was polymerized to form a high energy density battery with acute mobility. Lithium half-cell testing shows that phenyl hexasulfide (C6H5S6C6H5) can provide a specific capacity of 650mAh/g and capacity retention of 80% through 500 cycles at 1C rate along with superlative performance up to 10C. Furthermore, 1, 302W h/ kg and 1, 720W h/L are achievable at a low electrolyte/active material ratio. Electrochemical testing of polymer phenyl tetrasulfide reveals high specific capacities of 634mAh /g at 1C, while reaching 600mAh /g upon mechanical strain testing. This work introduces novel cathode materials for lithium-sulfur batteries and provides a new direction for the development of alternative high-capacity flexible cathode materials.

Indiana University-Purdue University Indianapolis (IUPUI) / With the exponential rise in manufacturing and usage of Li-ion batteries (LIBs) in the last decade, a huge quantity of spent LIBs is getting scrapped every year. Along with the efforts to making more capable and safer batteries over the last three decades, there is an immediate need for recycling these scrapped batteries. Most of these batteries typically use lithium manganese oxide (LMO), lithium cobalt oxide (LCO), lithium iron phosphate (LFP), and lithium nickel manganese cobalt oxide (NMC) cathode chemistries, and developing a technique towards regenerating these cathodes can ensure huge economic and environmental benefits for the present and future. This research focuses on a set of direct regeneration techniques with the goal of regenerating used cathode materials to be reused in LIBs. Used Apple iPad2 batteries with LCO chemistry and Nissan LEAF batteries with a combination of LMO-NMC chemistry are selected for this research. The scope of research can be divided into two parts as liberation/separation of cathode material and regeneration of liberated cathode. The liberation/separation process is carried out with the aid of ultrasonication and organic solvents with the objective being keeping the morphology and chemical composition intact for a better quality of the material. The regeneration process uses a hydrothermal technique with variations of parameters. 1:1 and 1:5 molar ratios between cathode material and a lithium lithiation agent are chosen to understand the effects of the molar ratio on cathode regeneration. In addition, the effects of processing solution (water vs. a solvent) are examined by replacing water with TEG. The effects of heat treatment on cathode regeneration are also investigated by observing phase changes of materials at different temperatures.