MATSUMI Laboratory
<Major Research Areas>Polymer Synthesis, Functional Polymers

From Hetero-Atom Chemistry
To Future Energy

Research activity

1Molecular design of electrolyte materials for
improvement of lithium secondary batteries.

　　Today, lithium secondary batteries are attracting much attention not only for the use in various mobile devices but also in automobiles, solar energy storage systems and so forth. Lithium ion batteries (LiBs) are expected to play a key role in smart grid systems to be developed in future. Despite the high energy density of LiBs, the number of problems associated with their usage has to be solved urgently. As solid polymer electrolytes for LiBs, polyether derivatives have been earnestly studied for the past several decades. These days, ionic liquids are also being intensely studied globally as a new class of electrolytes. However, both types of electrolytes generally suffer low lithium transference number. Under these contexts, we are developing various electrolytes including anion receptor or highly dissociable lithium salt structure making most of heteroatom chemistry. For instance, we reported a polymerized ionic liquid having alkylborane structure whose lithium transference number was found to be 0.87. This value is the highest among anion trapping type polymer electrolytes ever reported.

　　At the same time, most important matter is safety problem. As for LiBs, a number of explosion accidents have been reported during past several years, which led to the recall of huge number of battery products worldwide. There is an urgent social demand for safe and large scale energy storage systems. We are conducting studies for creation of standard electrolytes for new class of batteries through molecular design of flame-retardant electrolytes. We have synthesized a series of organic-inorganic hybrid type ion-gels by reaction of polysaccharides with boron compounds in ionic liquids. The materials obtained exhibited excellent ionic conductivity and non-flammable properties at the same time.

2Development of polymer photo sensitizer for dye sensitized solar cells

　　The solar cells that utilize limitless solar energy have been vigorously studied as key technology for the development of low carbon society. Particularly, growing attention is being focused on dye sensitized solar cells (DSCs) which is light, flexible and inexpensive. We recently succeeded in polymerizing β-diketonatoruthenium complex which are one of best known photo sensitizers in DSCs. The polymerization of photo sensitizers brings many advantages in characteristics of DSCs. 1. Polymer dyes enable efficient light harvest via energy transfer along the polymer chain (antenna effect). 2. By incorporating ruthenium on polymer, expensive ruthenium will be readily recovered by reprecipitation of polymer. 3. Adhesion of dye to electrode is improved by multi-point interaction (polymer effect). 4. By utilizing inexpensive organic unit as light harvesting antenna, amount of rare-metal (ruthenium) used is greatly reduced. We are developing various polymer ruthenium complexes by utilizing curcumin based bio-polyester as polymer ligand. The characteristics of the solar cells have been evaluated by constructing custom designed sandwich cells.

Equipment

nuclear magnetic resonance spectrometer, infrared spectrometer, impedance analyzer, electrochemical analyzer, high vacuum glove box, potentiogalvanostat, solar simulator, viscometer, differencial scanning calorimetry

The main research achievements in the past five years

1. T. Ogoshi, N. Ueshima, T. Yamagishi, Y. Toyoda, N. Matsumi, Ionic Liquid pillar[5]arene:Its Ionic Conductivity and Solvent-Free Complexation with a Guest, Chem. Commun., in press (2012).
2. S. R. Shankar, N. Matsumi, Hyperbranched Organoboron Polymer Electrolytes Derived from Glycerol, Polym. Bull., 68, 721-727 (2012).
3. N. Matsumi, A. Kagata, K. Aoi, K, Synthesis of Supramolecular Solid Polymer Electrolytes via Self-Assembly of Diborylated Ionic Liquid, J. Power Sources,195, 182-6186 (2010).
4. N. Matsumi, Y. Nakamura, K. Aoi, T. Watanabe, T. Mizumo, H. Ohno, Enhanced Ionic Conduction in Organoboron Ion Gels Facilely Designed via Condensation of Cellulose with Boric Acids in Ionic Liquids, Polym. J., 41, 437-441 (2009).
5. N. Matsumi, SPSJ Award for the Outstanding Paper in Polymer Journal Sponsored by ZEON (2009).