CA1129946A

CA1129946A - Method for the manufacture of an electrochemical cell or battery

Info

Publication number: CA1129946A
Application number: CA312,491A
Authority: CA
Inventors: Joannes J.P. Leyen
Original assignee: Electrochemische Energieconversie NV
Current assignee: Electrochemische Energieconversie NV
Priority date: 1977-10-14
Filing date: 1978-10-02
Publication date: 1982-08-17
Also published as: IT7851458A0; DE2844695A1; JPS6244386B2; GB2006101B; DE2844695C2; JPS5465338A; BE871222A; GB2006101A; FR2406313B1; ES474165A1; NL7810013A; IT1109213B; SE7810731L; FR2406313A1; CH644228A5

Abstract

A B S T R A C T
The invention relates to a method of manufacturing of an electro-chemical cell or battery, consisting of a stack of plate-shaped elements, including at least two electrode elements. The elements consist of a sheet or plate of electrode material which is mounted in a frame consisting entirely or partly of a thermoplastic material, in such a way that gas or liquid chambers are formed between the elements. These elements contain apertures which in the completed stack form channels for the supply or removal of liquid or gas. The thermoplastic material of adjacent elements are welded together by fusing the thermoplastic material and hardening it again.
At least one of the contact faces of successive elements is pro-vided with welding ridges consisting of the thermoplastic material around the edges of the orifices and along the inside and/or outside edge(s) of the element. The elements are attached to one another by vibration welding.
The method according to the invention is particularly suited for application to the manufacture of an electrochemical cell or battery in which gas and/or liquid transport occurs, as the channels serving for this are formed in a very simple way.

Description

A Method for the Manufacture of an Electrochemical Cell or Battery The invention relates to a method of manufacture of an electro-chemical cell or battery, for example a fuel cell or fuel cell battery, con-sisting of a stack of plate-shaped elements. Such stacks consist of at least two electrode elements, each of which comprises a sheet or plate of electrode material which is mounted in a frame consisting entirely or partly of a thermoplastic material, in such a way that gas or liquid chambers are formed between the elements. mese elements include apertures which in the completed stack form channels for the supply or removal of liquid or gas.
me elements are welded together by fusing the thermoplastic synthetic material locally around the edges of the orifices and/or along the inside and outside edge(s) of successive elements, and hardening it again.
A method disclosed elsewhere is carried out by fitting metal wires, Profiled metal sections or the like around the holes and along the edges in the frames of the elements, after which the connections around the holes are created by high~frequency heating of the metal wires, profiled metal sec-tions or the like. This causes the adjacent parts of the thermoplastic synthetic material to be heated to thus join together the two adjacent ele-ments around the holes and along the edges of the frames.
mis method has the disadvantage that a metal wire or profiled metal sectlon must be fitted where heating is to be effected locally. In addition, in many cases there are parts of some material other than that of the frames themselYes which display different levels of thermal contraction and expansion which can ~ive rise to leakage.
Another disadvantage is that during welding the thermoplastic material softens all around the wire or the metal profile, which can result in the orifices which in the completed stack form channels for the supply or -- 1 -- .

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removal of liquid or gas, filling up with softened material. To avoid this, it is customary to place pins or tubes - e.g. of metal - in the places where these oriEices are to be formed. mese pins or tubes are pulled out after the stack has been completed. me cross channels in particular are difficult to make in this way. Drilling the channels afterwards also presents obvious problems. m e object of the invention is to provide a method which does not have these disadvantages.
Accordin~ to the invention, such a method is characterised by the fact that in each case at least one of the contact planes of successive ele-ments is provided with welding ridges consisting of the thermoplastic syn-thetic material around the edges of the orifices and along the inside and/or outside edge(s) of the element, and that the elements are fixed one on top of the other by vibration welding.
In ~ibration welding the weldlng ridge undergoes rapid movement relative to the contact face of the adjacent element. As a result of the vibration, heatin~ occurs at the contact location and softening of the thermoplastic material is local. After hardening, a local weld is formed.
Examples of vibration welding are ultrasonic welding and friction welding. --~ n accordance with the present invention, it is unnecessary to have a metal wire or profiled metal section at the place of heating while at the same time strictly local heating can be effected at the contact surface between the welding ridge and the adjacent element~
An ad~antage of the method according to the invention is that due to the strictly local heating, the apertures ~that are to form the channels for the supply or removal of liquid or gas) will not fill up with melted thermoplastic material during welding. Moreover, the insertion of pins or ; tubes where these passages axe to be provided is not required nor is drilling of the elements after welding. The cross channels are formed in the same operation.
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' ' The stack may consist of more than two electrode elements and preferably of si~, twelve or more elements. Surprisingly, the welding of such numbers can be achieved by the me-thod according to this invention.
The method according to the invention is particularly suitable for the manufacture of an electrochemical cell or battery the electrode material of which is composed of several layers and in which at least one layer of each electrode is an electrically conductive metal gauæe.
In an embodiment of the method according to the invention, an electrode element consisting of a preformed frame to which is applied a sheet or plate of electrode material. The gauze of the electrode is bare where it contacts the frame. This sheet or plate is then subjected to the action of a welding horn having grooves in the plane of contact. During the ultrasonic welding, welding ridges are formed on the top of the stack as a result of the flow of thermoplastic material through the wire gauze into the grooves of the horn~
In a second embodiment, preformed electrode elements are used.
These elements each consist of a frame made entirely or partly of thermo-plastic material in which a sheet or plate of electrode material (the gauze o which is bare at the place of the frame) is mounted. The gauze is situated such that a first main surface of the frame largely coincides with the main surface of the metal gauze which is adjacent to it. The welding ridges are located on this first main surface.
Each successive electrode is applied to the stack so that this element is placed on the stack with the welding ridges on the underside and in contact with the stack. The second main surface of the frame located on the upper side is then subjected to the action o an ultrasonic welding horn. In this case, the welding horn is not grooved.

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In a third embodiment of the invention~ preformed electrode elements with welding ridges around the edges of the openings and along the inside and/oroutside edge(s) of the element are attached to one another by vibration welding.In this method two electrode elements to be fixed to each other are rapidly recip-rocated parallel to each other, with the welding ridges of the one element con-tacting the contact face of the other element. ~ great advantage of this embodi-ment is that a very large number of electrode elements can thus be united to a stack without deleteriously affecting the quality of the welds and without damag-ing the elements.
The preformed electrode elements can be made, for example, by injection moulding. The gauze is then placed against the wall of the mould in which grooves -for the formation of the welding ridges have been provided, and the welding ridg-es are created outside the gauze by the flow of the thermoplastic material through the wire gauze. Thus, in the injection moulding process the desired, greatest possible passage is always available for the melted plastic.
In the present invention, plastic is always welded to plastic, which greatly reduces the risk of defective welds.
In accordance with the present invention, there is provided a method of forming an electrochemical cell or battery consisting of a stack of planar elem-ents, including at least two planar electrode elements, each of which consists of a sheet or plate of electrode material which is mounted in a frame consisting entirely or partly of a thermoplas.tic material in such a way that gas or liquid chamb.ers are formed in the stack for the passage of fluids, said elements having fIrst and se.cQnd s.urfaces and b.eing formed wi~th.apertures therein, ~hich apertures in t~e co.=mp.leted s.~ack form sa~id caam.bers and channels: for the s:upply or removal '! of liquid or gas, compri~sing the steps-of; pr~yiding ridges of thermoplastic m~aterial o.n said fi.~rs.t surface, ad~acent to said apertures and adjacent to edges . ~ - 4 -' ,.

-: , , of said plates; placing a first and a second element in contact so that the ridges on the first surface of the first element contact the second surface of the second element; applying vibrational energy to cause said elements to vibrate relative to one another causing said ridges to heat and soften; allowing the thermoplastic material of said ridges to cool to thereby ~eld said first element to said second element along said ridges.
Fixing electrode parts to each other by ultrasonic welding has been dis-closed (French Patent Specification No. 2,115,263 and ~ritish Patent Specification No. 1,425,030). However, manufacture of a stack of plate-shaped elements with channels for the supply or removal of gas or liquid, in particular stacks with six or more or even twelve or more elements, cannot be derived from the present state of the art.
In drawings which illustrate embodiments of the invention: -Figure 1 is a top view of a stack under construction according to a first embodiment;
Figure 2 is an enlarged and more detailed view of the encircled section at II in Figure l;
Figure 3 is a cross section of a portion of the stack, along III~III in Figure 2;
Figure 4 which is show~n on the first page of drawings is a cross-section of a stack along IV-IV in Figure 1 with an ultrasonic welding horn on it, duringthe welding of a new plate-shaped element to it;
Figures 5 and 6 are more detailed views of the encircled section at V in Figure 4 repres.entin~, in Figure 5, the parts- to b.e welded in their correct posi-tion, b.ut drawn with.~e~tical spacing, and, in Figure 6, the arrangement duringwelding;
Fi~ure 7 is a partial cross-section of a stack under construction accord-ing to a second em~odiment of the invention; on the top is a new plate-shaped element to b.e welded thereto, by use of an ultrasonic welding horn placed on it.

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' In the figures, the same parts are always indicatea by the same reference numerals.
In the diagrammatic top view given in Fig. 1, the numeral 1 indi-cates a frame consisting of thermoplastic material in which is mounted a sheet of electrode material 2. The frame 1 and the sheet of electrode material 2 comprise the top frame and the top sheet of a stack which is under construction. Reference numerals 3 - 10 designate apertures in the frame. In the completed stack these apertures form channels for the supply or removal of liquid or gas. me central aperture 11 in the frame forms a gas or fluid chamber between two electrodes. Welding ridges 12 - 21 are situated around the orifices 3 - 10 and along the inside and outside edges of the frame.
These features are shown in greater detail and on a larger scale in Fig. 2 and Fig. 3. me welding ridges 12, 13, 20 and 21 are triangular in cross-section. Welding ridge 13 does not completely surround aperture 4 because in the frame of the element which is to be welded to the topmost element in the figure, there is a transverse channel communicating with the apertures for the supply of gas or liquid from channel 4 to the relevant chamber. mis channel must, of course, be bounded laterally by a gas- or liquid tight weld. Such transverse channels communicating with aperture 3 are indicated by 301 and 302 in ~ig. 3. Ridges which have melted to form welds are indicated by 21-01, 21-02 etc.; 12-01, 12-02 etc.; 20-02, 20-03 etc. Between electrodes 2-01 - 2-07 etc. there are chambers 11-01 - 11-06 etc. The individual frames welded to each other are indicated by 1-01, 1-02 etc.
In Fig. 4, reference numeral 41 is diagrammatic representation of a stack under construction, with a new element being fixed on it by means of an ultrasonic welding horn 42. me welding horn 42 is caused to vibrate : . : . ~ .

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ultrasonically by means of an ultrasonic generator 43.
As shown in Figs. 5 and 6, the welding horn 42 has grooves 54-55-56 at the location in which new welding ridges are to be formed during welding.
The frame 1-00 of the element to be welded to the stack has flat ridges 60, 61, 62 with grooves 57-58-59 respectively. During welding, melted material from the flat ridges 60, 61, 62 flows from the side walls of -the grooves 57, 58, 59 and then upwards into the grooves 54, 55, 56. The sheet of electrode material 2-00 of the element to be welded consists of a col-lector gauze 52 and one or more layers of electrochemically active material 51. At the edge 53 of the sheet the collector gauze is bare of other layers.
During welding, ridges 21, 12 and 20 of the frame 1-01, fuse with the material of the frame 1~00 and new ridges are formed on top of the frame 1-00.
Figure 7 illustrates a second embodiment of the invention wherein use is made of preformed elements in which the electrode sheet is already fixed in the frame. The electrode frame 72 with its welding ridges 75 which is to be welded to the stack has been placed on top of the stack 71 and the ultrasonic welding horn 73 has been placed in contact with the frame 72.
During manufacture by injection moulding the electrode sheet 74 has been fixed in the frame 72. The electrode sheet 75 lies in the approximate place of and in partial contact with, the under surface of the electrode sheet with welding ridge 75 penetrating the electrode gauze. The remaining features of Fig. 7 are self-evident having regard to the pre~ious explanation relating to the other figures.
Example I
According to the second e~bodiment of the invention (cf. also Fig. 7), preformed electrode elements of the type described, in which the thermoplastic ~aterial is a polyphenyloxide resin and the collector gauze is nickel gauze, are attached to one another by ultrasonic welding using a *Branson ultrasonic *Trade Mark 7 - . : : . -. ,, ~. :

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Z~46 welder operating at a frequency of 20 kHz.
In this way a stack containing twel-~e elements, with a closure plate on top and one underneath, was manufactured. In this stack gas-and liquid-tight welds are formed, and the channels (3) and cross-channels (301, 302) do not fill up with softened thermoplastic material.
Example II
According to a further embodiment of the invention, preformed electrode elements may be attached to each other by means of friction welding using a *Branson friction welder opera-ting at a frequency of 100 Hz.
In this way, a stack containing 32 elements, with a closure plate on top and another underneath, was manufactured. In this stack gas and liquid tight welds are formed, and the channels (3) and cross-channels (301, 302) do not fill up with softened thermoplastic material.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of forming an electrochemical cell or battery consist-ing of a stack of planar elements, including at least two planar electrode elements, each of which consists of a sheet or plate of electrode material which is mounted in a frame consisting entirely or partly of a thermoplastic material, in such a way that gas or liquid chambers are formed in the stack for the passage of fluids, said elements having first and second surfaces and being formed with apertures therein, which apertures in the completed stack form said chambers and channels for the supply or removal of liquid or gas, comprising the steps of:
providing ridges of thermoplastic material on said first surface, adjacent to said apertures and adjacent to edges of said plates;
placing a first and a second element in contact so that the ridges on the first surface of the first element contact the second surface of the second element;
applying vibrational energy to cause said elements to vibrate relative to one another causing said ridges to heat and soften;
allowing the thermoplastic material of said ridges to cool to thereby weld said first element to said second element along said ridges.

2. The method according to claim 1, wherein said sheet or plate of electrode material is composed of a plurality of layers of which layers at least one consists of a sheet of electrically conductive metal gauze; in-cluding the steps of:
placing said second element in contact with said first element so that the apertures therein are in alignment, applying said sheet of metal gauze to said first surface of said second element so that it covers the cen-tral open portion thereof and contacts a portion of said frame.

3. The method according to claim 2 including the steps of applying said sheet of metal gauze over said first surface of said second frame prior to weld-ing said second frame to said first frame, applying an ultrasonic welding horn to said second frame to cause thermoplastic material at the first surface thereof to heat and flow through said gauze into grooves in the welding horn to thereby form welding ridges and causing said first surface of said first frame to become welded to said second surface of said second frame.

4. The method according to claim 1 wherein said planar electrode element consists of a frame forming an outer perimeter of said element, said frame being composed at least in part of thermoplastic material and having a central portion wherein the electrode material is composed of several layers one of which layers consists of a sheet of electrically conductive metal gauze fixed to and partially overlying said frame, said thermoplastic ridges being situated on a surface of said frame including the steps of successively placing elements in contact with a partially assembled stack and welding each of said elements thereto in succession by use of ultrasonic energy.

5. The method according to claim 1 wherein said elements include a frame member having inner and outer edges, including the steps of providing thermoplas-tic ridges adjacent said outer edge and said inner edge and welding said ridges to a surface of an adjacent frame member by use of vibrational energy.

6. The method according to claim 5 including the steps of providing thermo-plastic ridges surrounding said apertures and welding said ridges to a surface of an adjacent frame member.

7. The method according to claim 5 wherein said frame members are formed with a recess in a surface forming a channel between said aperture and said inner edge, including the steps of providing ridges along said recess and said aperture and welding said ridges to a surface of an adjacent frame member to provide a means for communication of fluid between said aperture and a region beyond said inner edge.

8. The method according to claim 2, 5 or 7 including the step of heating said ridges by means of friction welding.

9. The method according to claim 2, 5 or 7 including the step of heating said ridges by means of ultrasonic energy to weld the elements together.