Patent ID: 6506515
Filing Date: 2003-01-14
Classification: H01M,Y02E,Y02P,Y02T,Y10T

Abstract:
A lithium secondary battery comprising:a battery case; and an internal electrode body contained in the battery case and including a positive electrode, a negative electrode and a separator made of porous polymer, the positive electrode and the negative electrode being wound or laminated so that the positive electrode and negative electrode are not brought into direct contact with each other via the separator, wherein a minimum value of a working volume ratio of each positive and negative active material is regarded as an experimental safe working volume ratio X3 when the usage rate of the negative electrode is 100%, and electrode areas of the positive and negative electrodes are divided into n elements respectively, each of said elements being substantially the same size and having a diameter of about 20 mm, yielding a ratio of the average value of working volume weight of the positive and negative active materials at the element to be regarded as an average working ratio Xav while the working volume ratio of the positive and negative active materials constitutes a normal distribution of dispersion &sgr;, n being at least 100, and the faulty rate of batteries using the elements is expressed with an upper probability Q(u)(where u=X3âˆ’Xav)/&sgr;) of the normal distribution, then, nxQ(u) being a faulty rate of the lithium secondary battery is set to be 1 ppm or less.