Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-07-10
2003-12-02
Kalafut, Stephen (Department: 1745)
Metal working
Method of mechanical manufacture
Electrical device making
C029S002000, C029S730000, C029S731000, C429S147000, C429S240000, C429S239000, C141S032000
Reexamination Certificate
active
06656232
ABSTRACT:
This application is a U.S. National Phase application of PCT International application PCT/JP99/05529.
TECHNICAL FIELD
The present invention concerns a method for manufacturing an electrode and an electrode used for batteries, etc. such as nickel hydrogen battery, nickel cadmium battery, etc., and an apparatus for forming an electrode for a battery constructed by spirally winding a porous metallic supporting base filled with active material, and an electrode manufacturing by this processing method.
BACKGROUND ART
The electrode of a secondary battery comprises foamed metal having continuous 3-dimensional network structure highly porous as supporting base and active material filled in this foamed metal. An electrode having such construction demonstrates comparatively excellent discharge characteristics. Moreover, these days, there is a strong request for improvement of high-efficiency discharge characteristics. To achieve that objective, the following construction is proposed: The manufacturing method comprises a process of forming a portion in which the core material portion is exposed without filling active material on one side along the longitudinal direction of the electrode, and a process of forming an about cylindrical electrode group by spirally winding positive and negative electrodes placed one upon another alternately, through a separator, and the end face of said about cylindrical electrode group is constructed only with the core material portion not filled with active material. By this construction, an exposed portion of a metal suitable for welding is formed and, by tabless system, the lead piece is welded to this exposed portion of metal. A secondary battery is proposed for the collecting characteristics of which are improved by such construction.
However, an electrode using foamed metal as core material does not have any solid metallic part in the core portion to which the lead piece can be directly welded. As countermeasures for it are proposed a method of further providing a metal sprayed layer on one side of the electrode on which to weld the lead piece, a method of depositing metal foil in advance for reinforcement, etc., to improve the electric conductivity of the material core portion. Moreover, in the Japanese Patent Laid-Open Publication No. 139251/87 is disclosed a method in which the portion not filled with active material in the electrode core material using foamed metal sheet is compressed in the direction of breadth of the electrode, as a measure for reinforcing the lead piece welding portion of the core material. By this method, the density and strength of the metallic part are increased, enabling welding of the lead piece.
This conventional method is indicated in FIG.
7
. The entire surface of the slender and rectangular electrode material
51
is pinched from both the left and the right sides by flat plane, and a strong pressurizing force F
1
is applied to that surface by an air cylinder
52
. While preventing production of any deformation such as bend, unevenness, change of thickness, etc. on the surface of the electrode and in the state in which one side of the electrode material
51
is supported from below, a strong pressurizing force P is applied by using a press
53
, in the direction of breadth of the electrode, from the side of the electrode material not filled with active material. The portion not filled with active material of the foamed metal forming one side in longitudinal direction of the electrode material
51
is compressed, to crush the voids produced with foaming. By this method, the density and strength of the metallic part in one side not filled with active material of the electrode material
51
are increased. In this way, attempts were made for achieving easy welding and improvement of quality.
However, generally, the filling volume of active material is variable depending on the portions of the surface of electrode and, therefore, the thickness of the surface of electrode is uneven. For that reason, it was difficult to uniformly support the surface of the electrode with metallic plane of high hardness from both sides of the electrode material. Moreover, variations were produced also in the filling width of active material in longitudinal direction of the electrode material
51
. For that reason, the supporting state of the electrode material changes at the portion in longitudinal direction and, when an attempt is made to apply a uniform pressurizing force in the longitudinal direction of the electrode material with a press, both the state of the electrode material receiving the pressurizing force of the press and the supporting state of the electrode material change. As a result, variations were liable to be produced in the strength and density of the side of electrode serving as lead welding portion, thus making it difficult to manufacture electrodes fully satisfactory from the viewpoint of quality. In the case where priority is given to increasing the strength and density of the lead welding portion of the electrode material by increasing the pressurizing force P of the press applied in the direction of breadth of the electrode material
51
, the pressurizing force has influences on the entire breadth of the electrode and the breadth of electrode tends to get narrower on the entire length, and the electrode is deformed under a strong pressurizing force applied locally. It was therefore difficult to form a lead welding portion of high density suitable for welding with a narrow width locally, only on one side of the breadth of electrode over the entire length of the electrode material. Furthermore, it was also difficult to fully retain excellent characteristics of foamed metal in other portions. Still more, this conventional method was insufficient particularly in productivity, and was therefore far from satisfactory.
In the conventional art described above, it was difficult to form any high-density lead welding portion suitable for welding of tabless lead uniformly and with high quality, over the entire length of one side in longitudinal direction of the electrode material, because the filling condition of active material in the electrode material produces variations by delicately changing locally. In addition, when a high-grade plasticity processing is applied to the foamed metal, as described above, the foamed metal is crushed, and the high-density foamed metal portion gets hard and fragile. For that reason, this conventional method also presents a defect that, in a subsequent process, fissures and cracks are produced when forming a cylindrical shape by spirally winding the positive and negative pole plates one upon another through a separator.
The Japan abstract J 57 80672 discloses the manufacturing of an electrode plate for alkaline batteries. A metal fibre substrate of rectangular form having a main area and an end section extending in the lengthwise direction and not being filled with active material. This strip like end section being folded in two or more plies. After this folding step the folded section is compressed to decrease the thickness thereof by applying a force to the folded section.
The object of the present invention is to provide an electrode enabling improvement of both battery performances and productivity in the processes for manufacturing an electrode, a method for manufacturing an electrode and an apparatus for manufacturing an electrode.
These objects are achieved with respect to a method for manufacturing an electrode by the features of claim
1
, to an apparatus for forming an electrode by the features of claim
6
, and to an electrode for a battery by the features of claim
12
, respectively.
Advantageous developments are claimed by the dependent claims.
DISCLOSURE OF THE INVENTION
A manufacturing method of electrode according to the present invention comprises:
(a) a step of filling active material in foamed metal having voids and supplying electrode material having filled portion filled with active material, unfilled portion not filled with the active material, and a boundary line between t
Ando Tsuneo
Katsumata Ikuo
Takeshima Hiroki
Usui Hiroyuki
Alejandro Raymond
Kalafut Stephen
Matsushita Electric - Industrial Co., Ltd.
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