Organic Radical Polymers for Energy Storage

Organic radical polymers were studied from two aspects – electron/ion transfer during the reduction-oxidation reaction and its application as a battery electrode. The former revealed fundamental reaction mechanisms that govern electrochemical behaviors of the organic radical polymers, while the latter tackled practical issues of electrode dissolution using a synthetic approach. The doping mechanism of nitroxide radical polymer PTMA was quantitatively investigated using quartz crystal microbalance with dissipation monitoring (EQCM-D) during electrochemical processes. Results showed that two doping mechanisms exist – doping by lithium expulsion and anion uptake. The relative dominance of one over the other was controlled by anion type, electrolyte concentration, and timescale. These results could apply in any scenario in which electrolyte is in contact with a non-conjugated redox-active polymer and present a means of quantifying doping effects. A one-step post-synthetic, carbon-compatible crosslinking method was developed to effectively crosslink the PTMA electrode and prevent its dissolution. The highest electrode capacity of 104 mAh g-1 (vs. a theoretical capacity of 111 mAh g-1) was achieved by introducing 1mol% of the crosslinker, whereas the highest capacity retention (99.6%) was obtained with 3mol% crosslinker. Both lithium expulsion and anion uptake were observed in doping, and the dominance was related to crosslinking density (i.e. free volume) in the electrode. This study indicated the importance of forming a network using a minimum amount of crosslinker, persevering radical content during crosslinking, and allowing enough free volume for electrolyte penetration. The electron and ion transfer mechanism of conjugated radical polymers (CRPs) with intentionally varied radical loadings (0, 25 or 100%) was studied to understand their inferior capacity compared to their non-conjugated partners. Results showed that the electron transfer shifted from delocalized electron transfer to localized electron hopping under higher radical loading. The extent of internal charge transfer between the conjugated backbone and the pendant radical was dominated by the radical loading. Doping occurred by exchanging one anion and one solvent molecule for every electron transferred in the CRP with 100% radical loading. For future design, the trade-off between radical loading and electronic conductivity need to be balanced

The influence of the electrolyte on the electrochemical behavior of PTMA as cathodic electrode material

The TEMPO-based polymer PTMA is a standard material for the research of organic radical batteries and displays a high capacity and a high rate stability at elevated currents when used with lithium-ion battery electrolytes. However, these electrolytes are the source of safety concerns and cause the dissolution of the organic electrode active material in the electrolyte, which limits the cycle life and leads to increased self-discharge. The aim of this thesis is to investigate the complex interactions and the resulting electrochemical behavior of PTMA-based electrodes in combination with different alternative electrolytes. The integrated publications establish the important role of the electrolyte for organic active materials and the lack of studies on this topic. Subsequently, the great influence of the electrolyte composition and concentration on the performance of PTMA-based electrodes is highlighted. In particular, a positive effect of highly concentrated electrolytes on the stability and self-discharge of PTMA-based electrodes is revealed. Based on this, the use of aprotic and protic ionic liquids as electrolytes for PTMA is investigated. There, a superior performance for PTMA in FSI--based aprotic ionic liquids is obtained. Lastly, the important aspect of self-discharge of PTMA with respect to current, rest time and electrolyte is studied. It is shown that the self-discharge mechanism strongly depends on the applied charging current, which is affected by the transport properties of the used electrolyte. The results of this dissertation show that the electrochemical behavior of PTMA is significantly affected by the alternative electrolytes. It is evident that with the use of different electrolyte concepts, the performance of PTMA can be optimized in a task-specific manner. In addition, the studies show that the electrolyte of an electrochemical investigation setup can be understood as a tool that can influence and elucidate the processes within the cells

Synthesis and Conductivity Studies of Tetraarylphosphonium Salts As Potential Electrolytes in Advanced Batteries

The purpose of this study was to synthesize polysubstituted tetraarylphosphonium/tetrakis (pentafluorophenyl) borate salts 3, also known as TAPR/TFAB where R is a substituent, and to measure their conductance/conductivity in low-polarity media such as tetrahydrofuran (THF) and dichloromethane (DCM). Such determination was to provide a rationale to the question of whether these compounds, and other weakly coordinating cations/anions combinations are suitable electrolytes for advanced batteries which are energized in safer, low-polarity organic solvents

Synthesis of nanometer-sized radical polymers and their arrangement on micro-fabricated substrates

制度:新 ; 文部省報告番号:甲2322号 ; 学位の種類:博士(工学) ; 授与年月日:2007/3/15 ; 早大学位記番号:新438

Redox-active radical polymers

制度:新 ; 文部省報告番号:甲2400号 ; 学位の種類:博士(工学) ; 授与年月日:2007/3/15 ; 早大学位記番号:新448

Radical polymers and their application to organic memory devices

制度:新 ; 文部省報告番号:甲2488号 ; 学位の種類:博士(工学) ; 授与年月日:2007/7/26 ; 早大学位記番号:新459

高分子型水素キャリア:合成と電解水素化

早大学位記番号:新7506早稲田大

Synthesis of Metal-Containing Polymers and Stable Organic Radical-Containing Polymers and Their Use as Advanced Functional Materials

The work presented in this thesis details the synthesis and characterization of two different families of multifunctional polymers. The first family involved the incorporation of stable 6-oxoverdazyl radicals into polymer scaffolds. This was originally achieved by the polymerization of the radical precursors, phenyl- and isopropyl-6-oxotetrazanes, followed by post-polymerization oxidation to afford the phenyl- and isopropyl-6-oxoverdazyl polymers. A second methodology involved the direct polymerization of isopropyl-6-oxoverdazyl radicals using ring-opening metathesis polymerization (ROMP) to afford polymers with controlled molecular weights and narrow molecular weight distributions. The polymers were characterized by the close comparison of the physical and spectroscopic properties to related model compounds. The semiconducting behaviour of the latter polymer was explored and ultimately exploited in flash memory devices. The second family included redox-active Ni(II) complexes of Goedken’s macrocycle. This macrocycle was incorporated into main-chain polymers via a step growth mechanism involving Sonogashira cross-coupling with π-conjugated solubilizing organic spacers and into side-chain polymers via a chain growth polymerization using ROMP. The resulting polymers spectroscopic and physical properties were characterized and compared to a variety of model compounds. Main-chain Ni(II) complexes of Goedken’s macrocycle and fluorene copolymers were further functionalized with Co2(CO)8 via the alkyne synthetic handle to yielded heterobimetallic copolymers that yielded metal-rich nanomaterials upon pyrolysis in a reducing atmosphere. Combined, this work represents a significant advance in the synthesis, characterization and application of synthetic multifunctional polymers

Aqueous one-pot synthesis of epoxy-functional diblock copolymer worms from a single monomer: new anisotropic scaffolds for potential charge storage applications

Nitroxide-functional polymers have garnered considerable interest in recent years and appear to hold promise for energy storage applications. However, their synthesis can be both expensive and time-consuming. Here, we propose a highly convenient method for the preparation of TEMPO-functional diblock copolymer nanoparticles directly in water. Epoxy-functional diblock copolymer worms are synthesized from a single monomer, glycidyl methacrylate (GlyMA), using a three-step, one-pot protocol in aqueous solution via polymerization-induced self-assembly (PISA). First, an initial aqueous emulsion of GlyMA was heated at 85 °C for 9 h to afford an aqueous solution of glycerol monomethacrylate (GMA). Then reversible addition-fragmentation chain transfer (RAFT) polymerization of GMA was conducted in aqueous solution using a dicarboxylic acid-based RAFT agent to produce a water-soluble PGMA homopolymer. Finally, chain extension of this pre-cursor block via RAFT aqueous emulsion polymerization of GlyMA at 50 °C produced amphiphilic diblock copolymer chains that self-assembled in situ to form a 15% w/w aqueous dispersion of diblock copolymer worms. These worms can be derivatized directly using 4-amino-TEMPO in aqueous solution, affording novel crosslinked anisotropic nanoparticles that contain a relatively high density of stable nitroxide radicals for potential charge storage applications</p