Kentaro Nakahara

Rechargeable batteries with organic radical cathodes

Abstract The first known application of stable radicals for energy storage systems is presented. A stable nitroxyl polyradical, poly (2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA) has been synthesized and applied to the cathode active materials in rechargeable batteries. These fabricated batteries have demonstrated an average discharge voltage of 3.5 V and a discharge capacity of 77 Ah/kg, which corresponds to 70% of the theoretical capacity. It should be noted that the capacity remains unchanged for over 500 cycles of charging and discharging at a high current density of 1.0 mA / cm 2 . Stable radicals promise to open new fields of use for plastic batteries.

Effect of Ethylene Oxide Structures in TEMPO Polymers on High Rate Discharge Properties

A copolymerized poly(4-vinyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (PTVE) was synthesized by cationic polymerization of a vinyl monomer bearing a 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) radical and an ethylene oxide or tri(ethylene oxide). The charge/discharge properties of copolymerized PTVE improved with the length of the ethylene oxide chain, and high rate and high power properties of the PTVE synthesized by copolymerization with tri(ethylene oxide) were much better than those of the PTVE homopolymer. Electrochemical measurements showed that the ionic conductivity of the polymer synthesized by copolymerization with tri(ethylene oxide) was higher than that of the PTVE homopolymer.

Analysis of mineral composition by infrared spectral imaging using quantum dot focal plane array sensor

In this report, mineral composition of rock samples including conglomerate, sandstone, and dolomite was analyzed by IR spectral imaging using QDIP focal plane arrays (FPAs) with a peak-responsivity wavelength of 6.5 μm (FPA 1) and 5.5 μm (FPA 2). The qualitative and quantitative analyses are presented, and the key factor that determines the quantitative precision is discussed. In the qualitative analysis, the luminance of the different components in the rock samples was compared in the image. In the FPA 1 images, the shell fossil in the conglomerate sample and the limestone in the sandstone sample were darker than the other parts of the rocks due to their low emittance at 6.5 μm. In contrast, the difference in the luminance is hardly observed in the FPA 2 images under the same conditions. In the quantitative analysis, the emittance of dolomite was measured. Ten points in the IR image were randomly selected and the average emittance was calculated. The obtained emittances were 0.544±0.012 (FPA 1) and 0.941±0.019 (FPA 2), which means the coefficient of variation of the emittance measurement is ±2.1%~2.2%. By calculating the propagation of error, the precision of thermocouples for monitoring the temperature of the rocks in the calibration contributes most significantly (73%) to the total error.

Effect of Ethylene Oxide Structures in TEMPO Polymers on High-Rate Discharge Properties

Introduction We have proposed an “organic radical battery” (ORB) in which stable organic radicals such as a nitroxide radical are applied to the electrode active material of a rechargeable battery. In the ORB an organic radical polymer poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (PTMA) bearing a 2,2,6,6tetramethylpiperidine-N-oxyl (TEMPO) radical was first used as a cathode active material. We reported that an Allaminated film packaged battery using PTMA might be suitable for high-power applications. We very recently synthesized poly(4-vinyloxy-2,2,6,6tetramethylpiperidine-N-oxyl) (PTVE) so as to improve the capacity of the ORB. The theoretical capacity of PTVE (135 mAh/g) is far higher than that of PTMA (111 mAh/g). 3 In this work, with a view to improving highspeed charge and high-output discharge properties of the ORB using modified PTVE copolymer, we have modified PTVE with ethylene oxide. We describe here the charge/discharge characteristics of a Li/copolymerized PTVE coin-type cell.