Tube pocket
The tube pocket is a special form of a separator for electrochemical elements such as electrolytic and galvanic cells . They are used in industrial lead accumulators such as traction batteries and serve as a container for lead dioxide (PbO 2 ), which is the active base material for the positive electrodes .
construction
Tube pouches consist of a number of tangentially interconnected round tubes made of polyester fleece or polyester fabric, which are open on both sides. The number of tubes, the length and the diameter can vary depending on the type of battery in which they are used.
Manufacturing
The tube pouches are produced in two variants:
- made of woven polyester sheets impregnated with acrylic resin
- made of non-woven polyester fleece impregnated with acrylic resin
In the production of non-woven polyester fleece, two layers of the desired width are first placed on top of one another and connected to one another by multiple parallel seams. The tubular shape is obtained by pushing round metal rods between the two layers at elevated temperatures. The resin in the fleece maintains its round shape after cooling. The pockets are cut to the desired length using a filament.
For woven tubular bags, the two layers are woven together with the appropriate spacing in the weaving mill. The tubular shape then results in the same way as with the non-woven colleagues.
application
The positive electrodes made with tube pockets are also referred to as tube plates . The advantage of the tubular plates predominantly used today over the flat plates previously used is the larger surface area of the plates, which makes it possible to manufacture batteries with greater capacity .
Tube pockets can be provided with a protective layer on half of the two outer tubes to improve the positive tube plates against short circuits . This is done either by applying a hot melt adhesive or, in the case of woven bags, alternatively by increasing the weave density (larger number of threads per centimeter).