Kazunobu Matsumoto

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.

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.

Self diffusion of Li+-ions in LixTi1+yS2 (v = 0.01–0.11)

Abstract Self diffusion of Li + ions in Li x Ti 1+y S 2 ( x =0–1, y =0.01–0.11) has been studies by means of the 7 Li NMR relaxation time T 1ϱ . Li x Ti 1.01 S 2 , with an approximately stoichiometric Ti content, had a self diffusion coefficient of 2 × 10 −10 cm 2 s −1 at 25°C for x ≤ 0.8. On the other hand, samples with the composition deviated from the stoichiometry had lower self diffusion coefficients and higher activation energies. Excess Ti ions showed the pinning and blocking effects which inhibit the Li + -ion diffusion in the interlayer of TiS 2 .