2006 Fiscal Year Final Research Report Summary
Synthesis of Radical Polymers and their Application as an Organic Radical Battery
| Project/Area Number |
17350061
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Polymer chemistry
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| Research Institution | Waseda University |
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Principal Investigator |
NISHIDE Hiroyuki Waseda University, Faculty of Science and Engineering, Professor, 理工学術院, 教授 (90120930)
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| Co-Investigator(Kenkyū-buntansha) |
SUGA Takeo Waseda University, Faculty of Science and Engineering, Research Associate, 理工学術院, 助手 (10409659)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Radical polymer / Nitroxide / Redox / Secondary battery / Electrode-active material / Electron transfer process / Photocrosslinking |
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| Research Abstract |
(1) Main chain structure and its redox-activity A polyether derivative bearing the redox-active 2,2,6,6-tetramethylpiperidinyl-N-oxy (TEMPO) moiety was insoluble, but slightly swollen in the electrolyte solution. The glass transition temperature (T_g) was below room temperature, and more flexible than the polymethacrylate derivatives. The cell performance fabricated with this polymer was maintained even with a higher radical polymer loading in the composite electrode, which revealed the flexible polyether backbone could contribute to its higher compatibility with the electrolyte solution and the current collector, and could also serve as a matrix for rapid electron transfer.
Photocrosslinking was chosen as a method for providing tunable solubility of the radical polymer, increasing mechanical toughness of the film, improving design flexibility and enabling patterning of the device. A photocrosslinked TEMPO-substituted polynorbomene was obtained using a bis(azide) crosslinker, which was
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carefully designed to eliminate side reactions on the nitroxide moiety. The obtained radical thin film exhibited a rapid and reversible redox at 3.58 V vs. Li/Li^+ and served as a cathode-active material even without any current collector. This approach facilitated battery manufacture via a wet, printable, and rollable process, leading to an organic-based, flexible paper battery.
(2) Electron transfer process of the radical polymer film and fabrication of the composite electrode A radical film obtained by photocrosslinking of the poly(TEMPO-substituted norbomene) displayed the redox behavior with a narrow peak-to-peak separation, resulting from the surface-confined redox species, which supported the rapid and quantitative electron transfer within 250 nm thickness. A SEM image of the radical polymer/carbon composite electrode also showed the carbon nanofiber was fully covered with the polymer (ca. 100 nm thickness) and suggested the electron can be transferred by the electron-hopping mechanism within the polymer layer.
(3) N-type radical polymers and their application as a totally organic-derived secondary battery Cyclic voltammetry, in-situ electrolytic ESR and UV/vis spectroscopy revealed that the reversible p-type redox of poly[4-(N-t-butyl-N-oxylamino)styrene], attributed to the oxoammonium cation formation and n-type redox of poly(nitroxylstyrene) o-substituted with trifluoromethyl group corresponding to the aminoxy anion formation, was tuned by the electronic effects of substituent groups. P-and n-type redox switching with chemical modification also promises a potential application of these polymers as cathode-and anode-active materials in all-organic batteries. Poly(galvinoxylstyrene) exhibited a reversible redox at 3.15 V vs. Li/Li+ under basic conditions, attributed to the n-type redox reaction between the galvinoxyl radical and galvinoxylate anion. A test cell fabricated with this polymer anode and poly(TEMPO-substituted norbornene) cathode, displayed stable charge-discharge curves at a plateau voltage of 0.66 V, which agreed well with the difference of the formal redox potentials for both radical polymers.
Through this study, the redox activity of the radical polymers has been correlated with their chemical structures and an all-organic-based battery was constructed, for the first time, with both radical polymers. Less
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