Tetsuichi Kudo

Thin film solid electrolyte and its application to secondary lithium cell

A thin film solid-state lithium secondary cell, Li/Li3.6Si0.6P0.4O4/TiS2, has been studied and cell performance evaluated. The electrolyte thin film developed was amorphous, ionic conductivity was 5×10−6 (ohm cm)−1 and its Li+ transference number was 1.0. The cathode film was composed of small and narrow plate-like TiS2 crystals intersecting each other, and had a preferred orientation of the crystallographic c-axis parallel to the substrate plane. The apparent chemical diffusion coefficient of Li+ in TiS2 film was 1.1×10−11 cm2/s. The open circuit voltage of the cell was about 2.5 V, and the short circuit current was 1.3 mA/cm2. It was also demonstrated that the cell was discharged about 2000 times.

Carbon monoxide gas sensor made of stabilized zirconia

Abstract The emf of zirconia galvanic cells, O2(I)+CO, Pt/stabilized ZrO2/Pt, O2(II), becomes anomalously higher than that calculated from Nernsts equation when PCO/PO2(I)

Ionic conductivity of electrolytes formed from PEO-LiCF3SO3 complex low molecular weight poly(ethylene glycol)

Films of poly(ethylene oxide)-LiCF3SO3-based complexes containing different amounts of poly(ethylone glycol) (PEG) with molecular weights ranging from 400 to 2000 were prepared by solution casting. The ionic conductivity is presented as a function of temperature, molecular weight and the PEG content used. The conductivity increases with decreasing molecular weight of PEG and with increasing PEG content. The incorporation of PEG with a molecular weight of 600 or less gives rise to a maximum conductivity value of 3 × 10−3 Sm−1 at 25° C. The conductivity enhancement at room temperature can be attributed to the increase in the amorphous regions responsible for the ionic conduction.

Peroxopolytungstic acids synthesized by direct reaction of tungsten or tungsten carbide with hydrogen peroxide

Synthese de W-IPA par reaction de W metallique avec H 2 O 2 et de CW-HPA par reaction de WC avec H 2 O 2 . Spectres Raman et RMN

Study of oxygen adsorption on platinum through observation of exchange current in a solid electrolyte concentration cell

Abstract To investigate oxygen adsorption of Pt, the exchange current ( i 0 ) in a solid electrolyte concentration cell is measured potentiostatically using a reference, counter, and working electrode with oxygen partial pressure ( P O 2 ) ranging from 6 × 10 1 to 2 × 10 4 Pa, at temperatures between 600 and 1000 K. It is found that i 0 is a function of P O 2 with a maximum at a specific P O 2 which depends on temperature, and the slope of the log i 0 vs log P O 2 for a higher P O 2 region is approx. 0.2 and that for a lower P O 2 region is between 0.2 and 0.6. These results are explained in terms of an electrochemical reaction of oxygen dissociatively adsorbed on Pt via a two-electron mechanism. On the basis of Langmuirs adsorption isotherm, the heat of oxygen adsorption on Pt is determined to be 180 KJ mol −1 .

Interpretation of the electromotive forces of solid electrolyte concentration cells during carbon monoxide oxidation on platinum

Abstract The electromotive force (emf) of solid electrolyte concentration cells used in CO + O2 nonequilibrium conditions has been studied by comparing the behavior of the reaction rate and emf for deposited Pt with that of the reaction rate and surface concentration of CO (as determined by infrared spectroscopy) for dispersed Pt. It was confirmed that the emf is generated by a mixed electrode potential involving electrochemical reactions of O2− with the CO and oxygen adsorbed on Pt during CO oxidation on Pt. Taking this mechanism as a basis for investigation, surface CO was detected even under conditions where CO was very scarce compared to oxygen. This indicates that CO oxidation on Pt proceeds via a Langmuir-Hinshelwood mechanism involving surface reaction between adsorbed species over the whole range of gas composition. Oscillations in emf, rate, and surface concentration of CO shown over a certain range of gas composition were presumed to be caused by the surface state where CO adsorbed on Pt became mobile.

Titanium disulfide films fabricated by plasma CVD

Abstract Titanium disulfide films are fabricated by plasma-enhanced chemical vapour deposition using TiCl 4 and H 2 S as source gases. The fabricated films have a nearly stoichiometric composition and preferred orientation whereby crystallographic c-axis is parallel to the substrate plane. The chemical diffusion coefficient of lithium in Ti 1.02 S 2 film was found to be 10 −11 - 10 −9 cm 2 /s depending on the lithium concentration. The activation energy of diffusion was found to be 30–60 kJ/mol. In addition, the secondary battery performance of thin film solid-state cell, Li/Li 3.6 Si 0.6 P 0.4 O 4 /TiS 2 was studied.

Carbon monoxide oxidation on platinum studied by local current and emf in a solid electrolyte concentration cell

Surface oxygen and CO concentrations (NO and NCO) adsorbed on Pt during oxidation are determined as functions of PO2 and pCO by local current and emf measurements for a solid electrolyte concentration cell in the region where PCO is low compared to PO2. The temperature range is 570 to 680 K, PO2 is between 1 × 102 and 5 × 104 Pa, and PCO ranges from 2.5 to 1 × 104 Pa. The local current is measured potentiostatically using reference, counter, and working electrodes. As a result, NO is determined to be proportional to PO20.0 · PCO0.1 and NCO to PCOδPO2 at about 640 K, where δ increases from 1 to about 1.6 as PCO increases. At lower temperatures, such as 580 K, NO is determined to be proportional to PO20.3 · PCO0.1, and NCO to the same formula as at 640 K. The dependence of NO is considered in terms of electronic effects of adsorbed CO on the Pt surface and that of NCO in terms of the residence time of mobile CO adsorbed on Pt. It is also considered that the initiation of oscillation in CO oxidation is related to the mobility of CO adsorbed on Pt. In the region where CO is more abundant, surface concentrations cannot be determined due to the predominance of resistance polarization in the local current.

New amorphous thin films of lithium ion conductive solid electrolyte

Abstract The electrical properties of amorphous thin films in the Li 2 O-SiO 2 -ZrO 2 system, which is thermodynamically stable with Li, were investigated in order to develop electrolytes for thin film solid state ionic devices. Films were deposited by planar-magnetron type rf-sputtering. These films had high ionic conductivities of 1≈4×10 −4 S/m at 25 °C with activation enthalpies of 51≈54 kJ/mol over the compositional range of 0.5 and Li/(Li+Si+Zr)≅0.8. The electron transference number for this high ionic conductive film was found to be less than 10 −5 by Wagner polarization technique. The Li + ion transference number was thought to be unity by d.c. conductivity values in comparison with the value obtained from complex impedance analysis.

Peroxypolytungstic acids: A new inorganic resist material

Recently reported amorphous polytungstic acids containing peroxo groups are found to provide a new inorganic resist. A homogeneous resist film can be formed easily with the spin coating method. This film is made insoluble in water by deep ultraviolet, x ray, and electron beam irradiation. The oxygen reactive ion etching (O2 RIE) durability is found to be high enough that a bilayer resist scheme employing this resist as a top imaging layer gives a high resolution pattern (line and space: 0.38 μm). The mechanism for the radiation induced reaction is also discussed.