Electricity: battery or capacitor charging or discharging – Cell or battery charger structure
Reexamination Certificate
2000-10-06
2001-10-16
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Cell or battery charger structure
Reexamination Certificate
active
06304057
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery module constituted by a plurality of prismatic cells connected adjacent each other, each of the cells accommodating therein an electrode plate group, comprising laminated positive and negative electrode plates with intervening separators therebetween, and particularly to the structure for fixing the electrode plate group in position within the cell.
2. Description of Related Art
Alkaline rechargeable batteries such as nickel metal hydride batteries are superior in energy density characteristics and have been used as the power source for an electric vehicle in recent years. Japanese Laid-Open Patent Application No. 7-161377 proposes a rechargeable battery, that is compact yet outputs a large amount of energy, in which a prismatic battery case accommodates therein, together with liquid electrolyte, positive and negative electrode plates stacked upon one another parallel to the long lateral walls of the battery case with intervening separators therebetween, the open end of the battery case being sealed with a lid member.
The battery disclosed in this publication is further described with reference to FIG.
4
. Reference numeral
31
and
32
respectively denote a battery case and a cover, both made of polypropylene. An electrode plate group
33
is accommodated within the battery case
31
together with liquid electrolyte, and the open end of the battery case is sealed with the cover
32
. The electrode plate group
33
comprises a plurality of negative electrode plates that are obtained by applying a paste mainly consisting of hydrogen-absorption alloy onto a flat plate core material, and a plurality of positive electrode plates that are obtained by packing powder mainly consisting of nickel hydroxide in a core material made of nickel porous material, these positive and negative electrode plates being laminated alternately with intervening separators made of polypropylene that is treated to obtain hydrophilicity. The positive electrode plates and the negative electrode plates are respectively connected to a positive and a negative electrode columns
35
a
,
35
b
through respective collector plates
34
a
,
34
b
, and the positive and negative electrode columns
35
a
,
35
b
are fixedly mounted to the cover
32
. In this state, there is a gap t
1
of about 2 to 10 mm between the bottom of the electrode plate group
33
and the inner bottom face of the battery case
31
, and a gap t
2
of about 1 to 5 mm between the lateral edges of the electrode plate group and the inner lateral face of the battery case.
These gaps t
1
, t
2
are formed for the purpose of: 1) making the liquid distribution of electrolyte uniform, and 2) preventing the electrode plate group
33
from being compressed by the inner walls of the battery case
31
when the electrode plate
33
expands during the charging and discharging of the battery. This is because deformation of the electrode plate group
33
may lead to inefficient use of active material and deterioration of discharge capacity, rises in the internal pressure during charging, short-circuits, or peeling of active material from the electrode plates.
However, in the sealed prismatic battery described above, the electrode plate group
33
is fixed to the cover
32
through the electrode columns
35
a
,
35
b
. Accordingly, there are variations in the position of the electrode plate group
33
with respect to the battery case
31
due to the positional displacement between the battery case
31
and the cover
32
during welding, and the gaps t
1
, t
2
are not uniformly formed, and electrode plates are sometimes deformed, leading to aforementioned various problems such as deterioration of discharge capacity due to insufficient use of active material, rises in the internal pressure during charging, and peeling of active material from the electrode plates. Further, there was the problem that the liquid electrolyte could not be distributed uniformly.
SUMMARY OF THE INVENTION
In view of these problems of the prior art, it is an object of the present invention to provide an improved structure for sealed prismatic cells that constitute a battery module, in which the electrode plate group can be fixed in position with respect to the cell case regardless of positional displacement between the cell case and a lid member for sealing the cell case, so that the battery performance is not compromised by the deformation of the electrode plates caused by the expansion/contraction of the electrode plates during charging and discharging, and in which liquid electrolyte can be uniformly distributed.
To achieve the above object, in a battery module according to the present invention that is constituted by a plurality of cells connected together adjacent each other, each of the plurality of cells comprises:
a prismatic cell case having short lateral walls and long lateral walls;
a group of electrode plates constituted by laminating a plurality of positive electrode plates and a plurality of negative electrode plates parallel to the long lateral walls of the cell case with intervening separators therebetween;
a collector plate of positive polarity and a collector plate of negative polarity, respectively bonded to the plurality of positive electrode plates and to the plurality of negative electrode plates at lateral opposite ends of the group of electrode plates, wherein each of the collector plates is fixed on the short lateral walls of the cell case so as to arrange the group of electrode plates in a predetermined position within the cell case;
liquid electrolyte accommodated in the cell case; and
a lid member for sealing an open end of the cell case.
Since the electrode plate group is fixed to the cell case through the collector plates, it can properly be fixed in position with respect to the cell case regardless of positional displacement between the lid member and the cell case that occur when welding them together, and therefore, there can be provided sufficient gaps between the electrode plate group and the inner bottom or lateral faces of the cell case to allow expansion and contraction of the electrode plates during charging and discharging, whereby deterioration of the battery performance resulting from deformation of the electrode plates can be prevented.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.
REFERENCES:
patent: 3844841 (1974-10-01), Baker
patent: 4693535 (1987-09-01), Frode
patent: 0264862 (1988-04-01), None
patent: 0962993 (1999-12-01), None
patent: 1059680 (2000-12-01), None
patent: 7161377 (1995-06-01), None
patent: 7220715 (1995-08-01), None
patent: 99/21236 (1999-04-01), None
Fujioka Noriyuki
Hamada Shinji
Ikoma Munehisa
Morishita Nobuyasu
Greenblum & Bernstein P.L.C.
Matsushita Electric - Industrial Co., Ltd.
Tso Edward H.
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