NOVELTY - A lithium ion secondary battery (100) comprises an electrode assembly (200); a case (300) for accommodating the electrode assembly and an electrolyte; a cap assembly (400) for sealing an opening in the case; and a first insulating plate positioned between the electrode assembly and the case, and a second insulating plate positioned between the electrode assembly and the cap assembly, where at least one of the first and second insulating plates comprises a material selected from polyvinylidene fluoride (PVDF) or a polymer having an ester group or a carboxyl group.    USE - As a lithium ion secondary battery (claimed) useful in light electrical and electronic apparatuses such as mobile telephones, notebook computers, and camcorders.    ADVANTAGE - The insulating plates do not exclusively contact the electrolyte, enabling the electrolyte to easily flow in the battery, and improves electrolyte impregnation and electrolyte impregnation speed, thus improving productivity.    DETAILED DESCRIPTION - A lithium ion secondary battery (100) comprises an electrode assembly (200); a case (300) for accommodating the electrode assembly and an electrolyte; a cap assembly (400) for sealing an opening in the case; and a first insulating plate positioned between the electrode assembly and the case, and a second insulating plate positioned between the electrode assembly and the cap assembly, where at least one of the first and second insulating plates comprises a material selected from polyvinylidene fluoride (PVDF) or a polymer having an ester group or a carboxyl group; or formed of polyethylene (PE) or polypropylene (PP) and has at least one surface coated with a material selected from polyvinylidene fluoride (PVDF), a polymer having an ester group or a carboxyl group or a surfactant. The first and second insulating plates further comprise an oxide selected from silica and aluminum oxide. The second insulating plate is cylindrical.    DESCRIPTION OF DRAWING(S) - The figure shows cross-sectional view of the battery.    Battery (100)    Electrode assembly (200)    Case (300)    Cap assembly (400)    Safety vent (410)