| POLYMERS Vol.69 No.3 |
| >> Japanese | >> English |
COVER STORY
Polymers in Next Generation Batteries |
| COVER STORY: Highlight Reviews |
| Polymer Electrolyte Membranes for Polymer Electrolyte Fuel Cells and Solid Alkaline Fuel Cells | Takeo YAMAGUCHI, Masashi MIYANISHI |
| <Abstract> Polymer-electrolyte fuel cells (PEFCs) represent a superior system that exhibits high-efficiency, offering better power generation, meeting the desired levels of demand. However, in order to facilitate widespread use of fuel cells, cost and lifetime problems must be resolved. Solid alkaline fuel cells (SAFCs) are another system that holds the potential to achieve high-energy conversion efficiency without Pt catalysts. Although most of metal catalysts can be used under alkaline environment, development of durable electrolyte membranes in alkaline media is the key for this technology. We are systematically designing and developing new materials from the molecular level to the device level. In the fuel cell systems, different components such as membrane, catalysts, and catalyst layer share significant functions and work in a well-coordinated manner, and hence, the total cell system must be optimized for the best performance. Specifically, pore-filling electrolyte membranes, packed acid type electrolyte membranes and durable anion-exchange membranes are developed based on the approach. Keywords: Polymer Electrolyte Fuel Cell / Solid Alkaline Fuel Cell / Membrane / Pore Filling Membrane / Anion Exchange Membrane |
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| Properties and Applications of Carbonate-Based Polymer Electrolytes | Yoichi TOMINAGA |
| <Abstract> In recent years, solid polymer electrolytes (SPE) have attracted much attention as “soft ionics” that contribute to next-generation batteries together with inorganic-based solid electrolytes as hard ionics. SPE is expected to be a suitable electrolyte material that contributes to the development of wearable electronics in order to make the battery thinner and lighter and simplify the manufacturing process. This review focuses on aliphatic polycarbonates as novel polymer matrix for SPE that exhibit unique ion-conductive properties such as increasing ionic conductivity and decreasing glass transition temperature with higher salt concentrations and better Li transference numbers of more than 0.5. This review also describes that concentrated poly(ethylene carbonate)-Li salt electrolytes have extraordinary electrochemical properties such as preventing Al corrosion reaction, excellent oxidation stability and good battery cyclability. Keywords: Solid Polymer Electrolyte / Ion-Conductive Polymer / Concentrated Electrolyte / Aliphatic Polycarbonate / CO2/Epoxide Copolymer / Lithium Battery / Lithium Transference Number / Oxidation Stability |
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| Progress in Organic Polymer Batteries | Kenichi OYAIZU |
| <Abstract> Organic high-density redox polymers are characterized by a large population of chemically robust and redox-active electron-releasing and -gaining sites that allow efficient redox-gradient-driven electron- or charge-transport and storage throughout the polymer layer via electron self-exchange reactions. Typically, the redox-active sites are quinones, imides, and organic robust radicals, which are bound to non-conjugated main chains such as polymethacrylate, polyacrylamide, polyvinylether, polyether and polynorbornene. The redox polymers give rise to high current density and areal capacity to allow a rapid charging/discharging capability that has relevance to high-density energy storage with excellent cyclability in electrode performance. The redox polymers are used as the electrode-active materials in organic polymer batteries. Targets of their application include high-power, flexible/stretchable and environmentally benign energy storage devices. Recently, fast charging mediators, organic redox flow batteries, and concept of superlithiation have been developed as the new trend of research in organic polymer batteries. Keywords: Redox Polymer / Charge Transport / Charge Storage / Mediator / Fast Charging / Redox Flow Battery / Superlithiation / Organic Polymer Battery |
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| COVER STORY: Topics and Products |
| Development of a Highly Safe and High Energy Density Lithium Battery using a New, Hardly Combustible Electrolyte | Atsushi UNEMOTO, Jun KAWAJI, Takefumi OKUMURA, Itaru HONMA |
| <Abstract> In this study, a novel quasi-solid-state electrolyte, whose lithium-ion conducting liquid was quasi-solidified at oxide particle surfaces, was developed. As the lithium-ion conducting liquid, solvate ionic liquid, comprised of an equimolar complex of lithium bis(trifluoromethanesulfonyl)amide and tetraglyme, was used. The resultant electrolyte, possessing solid-like high safety and liquid-like high lithium-ion conductivity, was used for 100 Wh and 363 Wh L－1-class high-capacity lithium battery assembly. The assembled battery exhibited an initial discharge capacity of 32 Ah with an average voltage of 3.67 V. Regardless of high energy-type, the discharge capacity remained as high as 26.2 Ah at 2 C. Repeated operation was also successfully demonstrated. The 118th discharge capacity retention ratio was as high as 96%. The developed lithium battery generated neither fire nor smoke in a nail-penetration test, suggesting that the developed lithium battery has high safety. Keywords: Lithium-Ion Battery / High Capacity / High Energy Density / Quasi-Solid-State Electrolyte / Safety / Nail-Penetration Test |
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| Effective Molecular Design of Anion Conductive Polymers for Alkaline Fuel Cells | Junpei MIYAKE, Kenji MIYATAKE |
| <Abstract> An anion conductive polymer is one of the key materials in alkaline fuel cells. While a number of molecular designs have been made, ionic conductivity and stability of the existing anion conductive polymers are insufficient. In this article, an effective molecular design for improving the properties of anion conductive polymers is described. A novel copolymer (QPAF-4) functions well in an operating fuel cell, not only as a membrane but also as a catalyst binder. Well-balanced combination of the polymer main chain (composed of aromatic rings and perfluoroalkylene groups without any heteroatom linkages) and the cationic groups (pendant trimethylammonium head groups with an alkylene spacer) was effective to improve the properties for alkaline fuel cells. Keywords: Anion Conductive Polymers / Fuel Cells / Membranes / Ionomers |
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| Development of Rechargeable Devices Using Plastic Crystals as Flexible Solid Electrolytes | Masahiro YOSHIZAWA-FUJITA |
| <Abstract> Plastic crystals including ionic compounds have recently been studied as a new class of ion conductors due to their partly liquid-like degrees of freedom that lead to high small-ion mobility such as for lithium ions and protons. In particular, organic ionic plastic crystals (OIPCs) are attractive materials as solid electrolytes because they are non-volatile, which is a desirable safety feature of electrochemical devices. OIPCs typically have disk and/or spherical shapes in ionic structures. Recently, we synthesized novel OIPCs based on pyrrolidinium salts. They exhibit a high ionic conductivity value at room temperature. On the other hand, in order to improve the mechanical properties of OIPCs, we prepared polymer composites. A PVDF nanofiber matrix is beneficial for the preparation of ultrathin flexible electrolyte membranes. Recently, further progress has been made using PVDF nanoparticles. The interfacial interaction between the polymer surface and the OIPC component ions improved not only the mechanical properties but also the ionic conductivity. Keywords: Organic Ionic Plastic Crystals / Mesophase / Solid-State Electrolytes / Rechargeable Devices / Li-Ion Batteries |
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| Polymeric Materials for New Water Electrolyzer Cell | Masamichi NISHIHARA, Yuki TERAYAMA |
| <Abstract> We developed a new water electrolysis system, a water-absorbing porous electrolyte electrolysis cell. In this water electrolysis system, pressurized water can be supplied to a porous hydrophilic electrolyte. To realize this water electrolysis system, we developed several components which were made of polymeric materials. A hydrophobic gas diffusion layer (GDL) for this electrolyzer was made by mixing solution of acetylene black, PTFE particles and PVDF. The obtained hydrophobic GDL showed an improved water-resistancy, lower electric resistance and lower gas permeability for this electrolyzer. The catalyst layer was also developed with a mixture of PtC, PTFE particles and PVDF to keep enough hydrophobicity. The electrolyte layer was produced from a porous zeolite as a proton conductor and poly(vinyl alcohol) (PVA) as a polymer matrix. Even though a porous proton conductive electrolyte membrane was used, this electrolyte system worked successfully. This cell is very unique and has the potential to widely expand hydrogen production systems, because we can apply different polymeric materials for this cell system. Keywords: Water-Absorbing Porous Electrolyte Electrolysis Cell / Hydrogen Production |
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| Polymer Science and I: A Personal Account |
| Toward a Free-Standing and Self-Righting Polymer | Atsuro TAKAI |
| <Abstract> In this essay, I look back on my academic career and describe my determination to become a free-standing and worldwide recognized researcher with an indomitable spirit, comparing it to traditional Japanese crafts “Okiagari-koboshi （self-righting doll）”. |
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| Front-Line Polymer Science |
| Nano DDS Based on Polymer Technology | Nobuhiro NISHIYAMA |
| <Abstract> The study on nano-scaled drug delivery system (nanoDDS) has steadily progressed, and its importance is increasing in the biomedical fields. Especially, new-modality drugs such as nucleic acid drugs and gene therapy has been receiving great attention, and nanoDDS should be indispensable for the realization of their clinical application. In addition, the combination of nanoDDS and medical devices is expected to realize new cancer diagnosis and treatment. This paper outlines the progress of nanoDDS research, especially focusing on the synthetic polymer-based technologies, and future prospects together with the results of recent studies in the related fields. Keywords: Drug Delivery Systems (DDS) / Biomedical Polymers / Polymeric Micells / Cancer Therapy / Cancer Diagnosis / Necleic Acids / Medical Devices |
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