CHARACTERISTICS OF A THIN-FILM LITHIUM-ION BATTERY USING PLASTICIZED SOLID POLYMER ELECTROLYTE

Synthesis was performed on a three-dimensional cross-linked material c omprising principal chains of a random copolymer made of ethylene oxid e and propylene oxide as a solid polymer electrolyte, which was plasti cized by an organic solvent. This solid polymer electrolyte has an ion ic conductivity of 1.5 x 10(-3) S cm(-1) at 20 degrees C and good temp erature properties. The solid polymer electrolyte is high in mechanica l strength and thermal stability because of the three-dimensional cros slinking. We have manufactured successfully a lithium-ion battery of f ilm form and card size with a thickness of 0.45 mm by using this solid polymer electrolyte. Positive electrodes of the battery use LiCoO2 as an active material, and negative electrodes use a less highly graphit ized carbon material. The battery has an average voltage of 3.6 and a discharge capacity of about 100 mAh. In a 0.3C cycle test at 20 degree s C, the battery was shown to have retained a capacity of about 90% of the initial capacity at the 300th cycle.