PURPOSE: To improve discharging performance and life performance by tightly filling granulated powder-form silica around an electrode plate group formed of a positive electrode plate, a negative electrode plate and a separator, and between the electrode plates, and by specifying the interval between the electrode plates and the shape of silica.
CONSTITUTION: Granulated powder silica has a number of pores smaller than a conventional glass separator. Since the silica has a function of inhibiting permeation and shortcircuit of active material, this function is utilized to shorten the interval between electrode plates and to improve the characteristic at the time of large current charging/ discharging. A positive electrode plate of no more than 3mm in thickness is used, and the silica is tightly filled around the electrode group formed of the positive electrode plate, a negative electrode plate and a separator, as well as between the electrode plates, while the interval between the electrode plates is defined 30-60% of the thickness of the positive electrode plate. For the granulated powder silica, the silica having no less than 20% of pores of no more than 0.1μm is used. The distribution of the pore diameters of the granulated powder silica and of the glass separator is indicated in the diagram. In the diagram, A indicates that of the granulated silica and B that of the glass separator.
TAKAHASHI KATSUTO
SHIOMI MASAAKI
