Nagase ChemteX in Osaka developed a positive-electrode material for lithium-ion batteries that uses sulfur. In the test that used sulfide solid for the electrolyte layer, the battery with a sulfur-based positive electrode exhibited 4.3 times more discharge capacity than the conventional battery with a cobalt-based positive electrode. Sulfur has over 10 times more theoretical discharge capacity than cobaltic acid lithium that is currently dominant as a positive electrode material. Although sulfur is cheap and abundant, its decreases output as the filling rate in the positive electrode increases. In addition, should it be used with organic solvent electrolyte layer, it dissolves to deteriorate the charge-discharge cycle.
The filling rate of sulfur of the new material is higher than 50%, and the company successfully increased the output by adopting the structure that decreases electric resistance and a sulfur solid electrolyte layer in place of the traditional organic solvent electrolyte to prevent combustion and reduce the deterioration due to the charge-discharge cycle, and by adjusting the figure and ratio of conduction assistance of electrons and ions. In the output test, the sulfur-based electrode exhibited 4.3 times more discharge capacity than cobaltic acid lithium in a current density of 2 mA. The company plans to commercialize it for smartphones toward 2018. Nagase ChemteX is a wholly-owned subsidiary of Nagase.
Demand for positive electrode materials of
lithium-ion battery is growing quite rapidly