Negative plate wrapped

With the preceding as background, a two-layered AGM separator was evaluated in a further ALABC project [19,20]. This separator consisted of a layer of 100% fine fibres (high surface area) and a second layer made of a mixture of 40% fine fibres with the addition of coarse fibres and chopped structural fibres (low surface area) [21]. Both the positive and negative plates were wrapped by this separator, with the 100% fine-fibre layer facing the electrodes the cell configuration is shown... 

One wraps a Lumiere photographic plate with a bromide emulsion in two sheets of very thick black paper, such that the plate does not become clouded upon being exposed to the Sun for a day. One places on the sheet of paper, on the outside, a slab of the phosphorescent substance, and one exposes the whole to the Sun for several hours. When one then develops the photographic plate, one recognizes that the silhouette of the phosphorescent substance appears in black on the negative. (Becquerel Comptes Rendus)... 

The purposes of the grid are to hold the active material mechanically and conduct electricity between the active material and the ceU terminals. The mechanical support can be provided by nonmetallic materials (polymer, ceramic, rabber, etc.) inside the plate, but these are not electrically conductive. Additional mechanical support is sometimes gained by the construction method or by various wrappings on the outside of the plate. Metals other than lead alloys have been investigated to provide electrieal conductivity, and some (copper, aluminum, silver) are more conductive than lead. These alternate conductors are not corrosion-resistant in the sulfuric acid electrolyte and are often more expensive than lead alloys. Titanium has been evaluated as a grid material it is not corroded after special surface treatments but is very expensive. Copper grids are used in the negatives of some submarine batteries. 

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