An object of the present invention is to provide a battery having a
film-type casing which is excellent in energy density as well as in
strength. Disclosed is a battery having a film-type casing that houses an
electrode body, the casing being formed of a film folded together, and the
electrode body being formed of at least one positive electrode plate and
negative electrode plate laminated together with a separator sandwiched
between the electrode plates and having at least one rectangular-shaped
outer surface, the battery comprising a reinforcing sheet attached the
electrode body so as to cover an area of the rectangular-shaped outer
surface corresponding to at least one corner of the positive electrode
plate. With this structure, an impact of a drop to a corner of the casing
is absorbed by the reinforcing sheet, which prevents the positive
electrode from tearing the separator and thus from electrically shorting
with the negative electrode plate. The present invention is especially
effective when the negative electrode plate and positive electrode plate
are band-shaped, the negative electrode plate is wider than the positive
electrode plate, and the electrode body is a spiral electrode body formed
by winding the positive electrode plate and the negative electrode plate
together with the separator sandwiched therebetween.
