Masatoshi Takahashi

Electrochemical characteristics of LiNiO2 and LiCoO2 as a positive material for lithium secondary batteries

Abstract The discharge characteristics of lithium nickel oxides have been improved by investigating their synthesizing conditions, such as their raw materials and heat-treating conditions. Lithium hydroxide (LiOH) and nickel hydroxide (Ni(OH)2) were found to be appropriate raw materials, and 750 °C in oxygen atmosphere was the most suitable heat-treating condition. Lithium nickel oxide synthesized under these suitable conditions showed a greater discharge capacity of more than 190 mAh/g than that of lithium cobalt oxide. The existence of lithium carbonate (Li2CO3) was detected, by the Fourier-transform infrared spectroscopy method, in lithium nickel oxide heat-treated in air. This suggests that the existence of Li2CO3 adversely affected the discharge characteristics of lithium nickel oxides.

Electrochemical behaviour of carbon electrodes in some electrolyte solutions

Abstract The electrochemical properties of coke and natural graphite in some electrolyte solutions containing diethylcarbonate (DEC) are studied. It is found that natural graphite exhibits am excellent performance, such as high discharge capacity (370 mAh −1 g), when a mixed solvent composed of ethylene carbonate (EC) and DEC is used. The charge/discharge characteristics of the coke electrode are mot influenced by the species of the electrolyte solution, but those of the natural graphite electrode are very much influenced by the species of the electrolyte solution. It is confirmed that there are three patterns in the behaviour of the graphite electrode in the electrolyte solutions tested in this investigation. In the first pattern, natural graphite can be charged to C 6 Li and them discharged. In the second pattern, the charging and discharging of the natural graphite electrode is impossible and destruction of the natural graphite crystal structure is observed. In the third pattern, lithium is intercalated into the graphite layer but the de-intercalation of lithium does not take place.

A study on electrolytes for manganese dioxide-lithium cells

Abstract The physical properties of organic electrolyte used in manganese dioxide-lithium cells play a major role in determining various cell characteristics. The influence on various cell characteristics of electrolytes has been investigated with flat cells. LiCF 3 SO 3 is the suitable solute in terms of low-temperature, storage and overdischarge characteristics. Mixture of ethylene carbonate (EC), 1,2-butylene carbonate (BC) and 1,2-dimethoxyethane (DME) is the suitable solvent in terms of high-rate discharge and storage characteristics.