Pure-lead positive grids

It has been shown [15] that the insulating a-PbO layer forms on lead-sheet electrodes at high positive potentials via an oxidation process which is the equivalent of overcharge. Furthermore, a-PbO can be produced at the grid interface during selfdischarge of an acid-starved battery at low states-of-charge [16]. There is evidence 

The passivation layer that forms on pure-lead grids in spiral-wound cells can lead to a premature drop in capacity during the first few cycles [21]. The passive film completely covers the surface of the pure-lead grid. 

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The basis for the performance of the alloy in VRLA batteries is corrosion of the lead-cadmium-antimony alloy to produce antimony in the corrosion layer of the positive grid, which thus eliminates the antimony-free eifect of pure lead or lead-calcium alloys. During corrosion, small amounts of antimony and cadmium present in the lead matrix are introduced into the corrosion product and thereby dope it with antimony and cadmium oxides. The antimony and cadmium give excellent conductivity through the corrosion product. The major component of the alloy, the CdSb intermetallic alloy, is not significantly oxidized upon float service, but may become oxidized in cycling service. 

The grids of both flat-plate and tubular batteries should not contain antimony or any other additive that may decrease the hydrogen overpotential of the negative electrode. Indeed, it is recommended that ultra-pure lead be used to manufacture both the grids and the active material in order to avoid the possibility of excessive self-discharge at either the positive or the negative plates. 

The same year, Ernest Volckmar replaced the lead sheet with lead grid [13] and Scudamore Sellon [7] used lead—antimony grids instead of pure lead grids. S.C. Curie devised tubular positive plates for lead—acid batteries. 

Pure lead is used for positive Plante plates and the grids in the Bell System vented round cell. Cylindrical cells of valve-regulated design (Gates, now Hawker) with punched grids employ lead for both grids with a small tin addition (44). 

Half formation type. This type is between the pasted type and formation type, in which the positive plate is a grid with small squares made by pure lead. Pure lead grid will act as a role of formation type plate when the active material is shedding. 

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