Katsuki Miyauchi

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.

Ionic conductivity of Li2OB2O3 thin films

The ionic conductivity of evaporated Li2OB2O3 thin films has been studied. These thin films were found to show a considerably high ionic conductivity of 1 × 10−7 Ω−1 cm−1 at room temperature. The conductivity increases with increasing Li content and exhibits a maximum value near 3Li2O·B2O3. The structure of these films was determined using infrared absorption and laser Raman scattering spectroscopy. Using the results, the correlation between structure and conductivity is also discussed.

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.

Thin Film Growth of YBa2Cu3O7-x by ECR Oxygen Plasma Assisted Reactive Evaporation

A new apparatus equipped with an ECR oxygen plasma source, a co-evaporation system of Y, Ba and Cu and a differential pumping system was developed. YBa2Cu3O7-x superconducting films were obtained at a substrate temperature of 450–500°C. The critical temperatures of films deposited on SrTiO3, MgO and Si substrates were 87 K, 80 K and 63 K, respectively. These properties were closely related to the crystallinity of the film.

Electrochromism of WO3/LiAlF4/LiIn thin‐film overlayers

A thin, amorphous LiAlF4 film, with lithium ion conductivity of 1×10−4 S/m at 25 °C, has been prepared by vacuum evaporation. Utilizing this thin film as a solid electrolyte, an ITO/WO3/LiAlF4/LiIn overlayer has been constructed (ITO: indium‐tin‐oxide). For it, the electrochromism of WO3 due to lithium ion injection was observed.

Amorphous thin film ionic conductors of mLiF.nAlF3

Abstract The theoretical compound LiAlF 4 (=LiF.AlF 3 ) looks promising as a thin film ionic conductor. This paper describes an experiment to determine the conduction characteristics of that compound. A mixture of LiF and AlF 3 is evaporated under 1 mPa onto glass substrates kept at room temperature. The resulting 0.8 μm thick colorless transparent film is amorphous even after annealing at 600°C as judged by X-ray diffraction. AC conductivity is measured to be 1.0 × 1.0 −4 S/m at room temperature in a nitrogen atmosphere. This conductivity is determined to be principally ionic in nature, from lithium ions and/or protons. Further investigation of the molar ratio, the m and n for each component molecule, reveals that the optimum molar ratio, m/n, for the highest ionic conductivity ranges between 5 3 , corresponding to Li 5 Al 3 F 14 , and 1 1 , corresponding to LiAlF 4 . This conductivity is 10 6 times larger than that of either component material.

Low temperature growth of superconducting YBa2Cu3O7−x thin films by organometallic chemical vapour deposition

Abstract A superconducting YBa 2 Cu 3 O 7− x thin film with a zero-resistivity temperature of 83 K was grown on an SrTiO 3 (100) substrate at 700°C by organometallic chemical vapour deposition. Yttrium, barium and copper tetramethylheptanedione complexes and oxygen were used as source materials and the deposition pressure was 1.5 mmHg. The onset temperature for the superconducting transition was 86 K. Above this temperature the resistivity of the film decreased with decreasing temperature. The thin film is polycrystalline and has a crystallographic orientation in which the a axis is perpendicular to the substrate plane.

Preparation of YBa2Cu3O7-x Superconducting Thin Films by RF-Magnetron Sputtering

Thin films of Y-Ba-Cu-O system have been prepared by rf-magnetron sputtering technique. The sputtered film was a multilayer composed of (Ba, Cu, O) and (Y, Cu, O). The films were crystallized by a high temperature chemical reaction between BaCuO2 and Y2Cu2O5 layers. Critical temperatures of YBa2Cu3O7-x thin fims in this study were 80-85 K.

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.

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.