Kazuhiro Tachibana

Polymer electrolytes based on dicationic polymeric ionic liquids: application in lithium metal batteries

Polymeric ionic liquids (PILs) have stirred up great interest for their potential applications as electrolyte hosts in lithium metal batteries (LMBs) because of their desirable performance. In this work, PIL-based gel polymer electrolytes applied in lithium metal batteries (LMBs) at low–medium temperatures (25 °C, 30 °C and 40 °C) are first reported. A novel imidazolium-tetraalkylammonium-based dicationic polymeric ionic liquid, poly(N,N,N-trimethyl-N-(1-vinlyimidazolium-3-ethyl)-ammonium bis(trifluoromethanesulfonyl)imide) is successfully synthesized, and its structure and purity are confirmed by 1H NMR, FTIR and elemental analysis. Subsequently, the ternary gel polymer electrolytes are prepared by blending the as-synthesized dicationic PIL as the polymer host with 1,2-dimethyl-3-ethoxyethyl imidazolium bis(trifluoromethanesulfonyl)imide (IM(2o2)11TFSI) ionic liquid and LiTFSI salt in different weight ratios. The PIL-LiTFSI-IM(2o2)11TFSI electrolytes reveal low glass transition temperatures around −54 °C and high thermal stability to about 330 °C. Moreover, the ternary gel polymer electrolytes show good ion conductivity around 10−4 S cm−1 at low–medium temperatures, high electrochemical stability and good interfacial stability with lithium metal. Particularly, the Li/LiFePO4 cells assembled with polymer electrolytes at a rate of 0.1 C are able to deliver discharge capacities of about 160 mA h g−1, 140 mA h g−1 and 120 mA h g−1 at 40 °C, 30 °C and 25 °C, respectively, with excellent capacity retention, as well as exhibiting acceptable rate capability. These findings reveal that dicationic PIL-based electrolytes have great potential for use as safe electrolytes in LMBs.

A dual-electrode flow sensor fabricated using track-etched microporous membranes ☆

A new dual-electrode flow sensor has been fabricated by piling the microporous membrane electrodes which have 7-10μm thickness. The electrode was prepared by sputtering of platinum onto both sides of the membrane filter which contain a smooth flat surface as well as cylindrical pores with uniform diameters. The electrolysis is performed when the sample solution flows through the membrane electrode, and a generated analyte on the first working electrode is instantaneously transported to the surface of second working electrode which is located at the downstream of the first one. In this case, the sample solution surely flows through the pores of the membrane filters. As the result, highly efficient electrolysis was achieved at each electrode, and the collection efficiency values as high as 100% were obtained in the wide range of flow rate. Good responses to the injections of sample solutions were also confirmed in the FIA system.

Development of in situ a.c. impedance measurement system under constant-current conditions and its application to galvanostatic discharge of electrolytic manganese dioxide in alkaline solution

Abstract An inexpensive a.c. impedance measurement system to elucidate the solid-phase electrochemical reactions inside the active materials of batteries during charge and discharge has been developed by using a cheap galvanostat and a personal computer. In order to develop a simple, in situ, a.c. impedance measurement system for evaluating cells, the impedance of manganese dioxide in alkaline solution under constant-current discharge has been measured. To obtain the impedance, a discrete sinusoidal current is superimposed on the cell under the constant-current polarization, and the resulting transfer function is calculated by a single, sine wave, correlation method. Software developed in this study makes it possible to measure the impedance without using a frequency-response analyzer. A large sinusoidal current of magnitude up to that of the discharge current can be superimposed while keeping the sinusoidal potential response in the linear range, and this enables reliable impedance measurements to be conducted. The impedance and frequency characteristics thus obtained reflect well the discharge behaviour of manganese dioxide in alkaline solution.

Relationship between Dipole Moment of Organic Compound Impurity in Liquid Crystal Field and Leakage Current of Liquid Crystal Cell

The degradation of the reliability of liquid crystal display (LCD) is dependent on ions in the liquid crystal (LC) cell. However, we found that the nonionic organic compounds added into the LC material also decreased the reliability of LCD because of the leakage current. The conductivity and the dielectric constant of the LC cells containing an LC mixture (ZLI-2293) with or without the nonionic organic compounds were examined by the AC impedance method. The leakage current, as well as the conductivity, was found to be related to the dipole moment of the compound. Therefore, if the dipole moment of the compound is larger than 4 D, the current will tend to leak in the LC cell.

Adhesion Property between Aluminum Current Collector and Carbon Conductor at Polarized Condition of Positive Electrode for Lithium-Ion Secondary Battery

The carbon conductor is exfoliated from the aluminum current collector when overcharged. That exfoliation results from stress caused by volume expansion of the carbon conductor, not from electrolyte wetting, internal electrostatic force, or a carbon intercalation reaction. Electrolysis of the anion is the reason. Therefore, we are taking care to evaluate adhesion properties not only at coating, but also at charging.