Metal working – Method of mechanical manufacture – Electrical device making
Patent
1998-12-02
2000-07-11
Maples, John S.
Metal working
Method of mechanical manufacture
Electrical device making
296231, 429 36, H01M 1004, H01M 824
Patent
active
060866438
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for the fabrication of electrochemical cells and, in particular, to a method for the fabrication of industrial electrolytic or galvanic cells which comprise a plurality of components joined together in a stack.
Industrial electrolytic or galvanic cells, such as secondary batteries, fuel cells and electrolysers, typically consist of modules which each comprise a number of stacked, layered components which are clamped together in a stack. For example, in a secondary battery of the redox flow type the components typically consist of electrically insulating flow-frames, each containing an electrode, with a plurality of such flow-frames being sandwiched together with other components such as membranes and meshes. Secondary batteries of this type are well known to a person skilled in the art.
In the assembly of the modules from their component parts the most important considerations are: isolated from each other and contained successfully with minimal leakage to the outside, it is necessary for satisfactory seals to be provided between the individual layers of the stack and between the individual compartments within the stack, for example, by sealing a frame around the perimeter of each electrode; relation to the adjacent components; and remain intact and undisturbed as the rest of the stack is formed and the unit sealed. Some membranes may have a tendency to tear, crease, fold or puncture and/or may be highly sensitive to the partial pressure of water.
Conventionally, fluid seals have been achieved, for example, by employing an elastomeric seal arrangement between each flow frame, such as an O-ring or flat gasket. Conventional locating and holding devices may be used to position individual components with respect to their neighbours and then to fix them in place to form a sub-module. However, when the stack consists of large numbers of components, a reliable assembly of the stack with a plurality of O-rings is still difficult to achieve and is labour intensive. Elastomeric materials which are chemically resistant to aggressive electrolyte chemicals are relatively costly and can make up a significant proportion of the total cost of such an assembly. Furthermore, the requirement for O-ring grooves may conflict with the easy and reliable fulfilment of the other functions of the frame, such as the flow distribution of liquid electrolytes, especially with stacks containing thin frames, for example when the thickness of the frame approaches <2.5 times the thickness of electrolyte feed channel.
It has also been proposed to create fluid seals with the avoidance of the cumbersome and costly assembly of O-rings by welding the layers together, for example using friction welding for frame to frame seals, and/or laser welding for electrode to frame seals. Disadvantages of this method include the possible disruption of carefully positioned and conditioned membranes by movement and/or heat during frame-to-frame sealing, the need to have compatible materials which can be welded together successfully, the inability to disassemble and the method of guaranteeing the reliability of the weld.
A further type of sealing arrangement has been proposed in which a sealing mechanism is incorporated into the form of the flow frame and in which a flexible blade locates with a special channel specifically for the purpose of completing the seal. A sealing arrangement of this type is disclosed in U.S. Pat. No. 4,640,876. The flexible blade which completes the seal is, however, difficult to manufacture and due to flexing would be susceptible to environmental and mechanical degradation.
FR-A-2292345 describes a tongue and groove arrangement for joining together the frame components of a electrical cell. The tongue on one frame is fitted into the corresponding groove on an adjacent frame and the frames fixed together using adhesives, solvents or ultrasonic welding.
FR-A-2700639 describes a seal formed by pinching a flat metallic sheet between a tongue and a groove formed opposite one another on adjacen
REFERENCES:
patent: 3320092 (1967-05-01), Tapsell
patent: 3565693 (1971-02-01), Tapsell
Clark Duncan Guy
Joseph Stephen Hampden
Male Stewart Ernest
Maples John S.
National Power PLC
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