Okitoshi Kimura

Ion rechargeable batteries using synthetic organic polymers

Abstract We have newly developed multi-porous sheets fabricated from chemically polymerized polyaniline which are applicable for positive electrodes of ion rechargeable batteries. We have also developed novel multi-porous sheets for negative electrodes made of carbon material which are derived from synthetic organic polymer. Both sheets fabricated to have an area of maximum 1000cm 2 and thickness of 0.3∼3.0mm are reinforced by synthetic short fiber. Because of fiber-reinforcement, these sheets show excellent mechanical properties and easy handling in spite of their high porosity. The polyaniline positive electrodes have been combined with the carbon negative electrodes to produce high energy density cells having excellent cycle life and a high working voltage. Preliminary prototype CR 2016 cells made of these electrodes in welded steel can have demonstrated up to 17 mWh/cell.

Polaronic transition in electrochemical polymerized polyaniline

Abstract Polyaniline films prepared by electrochemical polymerization in sulfuric acid show stability for doping (energy density 140–160 Ah/kg) and undoping in non-aqueous electrolyte by choosing suitable conditions. According to cyclic voltammetry with lower potential sweep rates (

In Situ Conductivity, Electron Spin Resonance and Absorption Spectra Measurements in Polyaniline During Electrochemical Doping

In in situ measurements of ESR during electrochemical doping in polyaniline, the maximum spin density is observed at 3.25 V. ESR linewidth decreases upon doping, but after exhibiting a minimum value at 3.5 V, it increases again, tending to saturation. On the other hand, in situ conductivity measurement demonstrates the maximum value (1.6 S/cm) at around 3.5 V. Taking into consideration the complex absorption spectral change upon doping, the results are discussed in terms of polaron and bipolaron models. At higher doping levels, suppression of the interchain transfer of polaronic species due to Coulomb interaction is introduced to explain the decrease of conductivity.

An ESR study on polyaniline in nonaqueous electrolyte

Abstract ESR measurements were performed for polyaniline (PANI) at various doping levels electrochemically controlled in aprotic conditions, LiBF4/PC-DME and LiAsF6/PC-DME. Spin density and linewidth in the ESR spectrum of LiBF4-doped PANI (PANI/BF4−) change dramatically at c. 3.2 V versus Li/Li+ indicating the formation of bipolarons. On the contrary, the variation of the ESR spectrum of LiAsF6-doped PANI (PANI/AsF6−) in the same potential range is less clear. This corresponds to the fact that the change in spectrum and electrical conductivity of PANI/AsF6− is much slower up to highly positive potentials, which is explained in terms of high stability of the polaronic state. Effects of O2 and H2O on the ESR signal of PANI/BF4− are significant; linewidth of the signal changes reversibly by reacting with O2 and H2O without change in conductivity, suggesting a facile relaxation of the polaronic spins by interacting with paramagnetic spins of O2.

Non-linear electric properties of polyaniline doped with organic acceptors

Abstract Complexes of polyaniline (PANI) with various organic r -electron acceptors such as TCNQ and others were prepared by the automatic doping method. The relationship between current and applied voltage was linear and ohmic in argon atmosphere at voltages below 5 V, but in air it was non-linear. A field-effect current was observed at PANI-chloranil complex on silicon substrate.

New type polymer electrode using soluble polyaniline

Abstract A new type of electrode has been prepared by the coating method from a solution mixture of polyaniline(PANI) and V 2 O 5 . The composite electrode exhibited high capacity density of 200 mAh cm −3 , favorable redox activity explainable by the bi-ion-transfer mechanism, and high redox stability against the over-discharging. This result was supported from X ray diffraction patterns of the composite electrode.