Lead-acid battery position

The excellent corrosion-resistant lead dioxide, Pb02, film formed on anodes and lead—acid battery positive grids in sulfuric acid has enabled lead insoluble anodes and lead—acid batteries to maintain the dominant positions in their respective fields. 

Glass fibres coated with Sn02 have been developed and used in lead-acid battery positive plates with the aim to improve the process of plate formation and the performance of the plate. 

Chemical and Electrochemical Reactions during Formation of Lead—Acid Battery Positive Plates... 

In fabricating a lead-acid battery positive electrode, using more sulfuric acid in the positive paste can improve the battery capacity. This is because more sulfuric acid can increase the quantity of lead sulfate in the positive paste, leading to more production of P-Pb02 due to the oxidation of lead sulfate in the formation process. The additional benefit is that the plate porosity can be increased with increasing lead sulfate in the paste. The increased lead sulfate can go into the internal active materials, improving the use ratio of lead dioxide. 

D. Pavlov, Mechanism of the Processes of Formation of Lead-Acid Batteries Positive and Negative Plates, in Proc. Symp. on Batteries for Traction and Propulsion, 1972, Columbus Section of the Electrochemical Society, 135. 

Automobile battery grids employ about 1—3 wt % antimony—lead alloys. Hybrid batteries use low (1.6—2.5 wt %) alloys for the positive grids and nonantimony alloys for the negative grids to give reduced or no water loss. The posts and straps of virtually all lead—acid batteries are made of alloys containing about 3 wt % antimony. 

Silver reduces the oxygen evolution potential at the anode, which reduces the rate of corrosion and decreases lead contamination of the cathode. Lead—antimony—silver alloy anodes are used for the production of thin copper foil for use in electronics. Lead—silver (2 wt %), lead—silver (1 wt %)—tin (1 wt %), and lead—antimony (6 wt %)—silver (1—2 wt %) alloys ate used as anodes in cathodic protection of steel pipes and stmctures in fresh, brackish, or seawater. The lead dioxide layer is not only conductive, but also resists decomposition in chloride environments. Silver-free alloys rapidly become passivated and scale badly in seawater. Silver is also added to the positive grids of lead—acid batteries in small amounts (0.005—0.05 wt %) to reduce the rate of corrosion. 

In Figure 1, the cutaway view of the automotive battery shows the components used in its constmction. An industrial motive power battery, shown in Figure 2 (2), is the type used for lift tmcks, trains, and mine haulage. Both types of batteries have the standard free electrolyte systems and operate only in the vertical position. Although a tubular positive lead—acid battery is shown for industrial appHcations, the dat plate battery constmction (Fig. 1) is also used in a comparable size. 

Fig. 2. Cutaway view of a tubular positive lead—acid battery, (1) Positive tubular plate (2) iiegatwe plate (3) separator (4) connecting strap (5) ceU cover (6)...

The mercurous sulfate [7783-36-OJ, Hg2S04, mercury reference electrode, (Pt)H2 H2S04(y ) Hg2S04(Hg), is used to accurately measure the half-ceU potentials of the lead—acid battery. The standard potential of the mercury reference electrode is 0.6125 V (14). The potentials of the lead dioxide, lead sulfate, and mercurous sulfate, mercury electrodes versus a hydrogen electrode have been measured (24,25). These data may be used to calculate accurate half-ceU potentials for the lead dioxide, lead sulfate positive electrode from temperatures of 0 to 55°C and acid concentrations of from 0.1 to Sm. 

Some battery designs have a one-way valve for pressure rehef and operate on an oxygen cycle. In these systems the oxygen gas formed at the positive electrode is transported to the negative electrode where it reacts to reform water. Hydrogen evolution at the negative electrode is normally suppressed by this reaction. The extent to which this process occurs in these valve regulated lead —acid batteries is called the recombination-efficiency. These processes are reviewed in the Hterature (50—52). 

The lead—acid battery is comprised of three primary components the element, the container, and the electrolyte. The element consists of positive and negative plates connected in parallel and electrically insulating separators between them. The container is the package which holds the electrochemically active ingredients and houses the external connections or terminals of the battery. The electrolyte, which is the Hquid active material and ionic conductor, is an aqueous solution of sulfuric acid. 

The tubular positive plate uses rigid, porous fiber glass tubes covered with a perforated plastic foil as the active material retainer (Fig. 2). Dry lead oxide, PbO, and red lead, Pb O, are typically shaken into the tubes which are threaded over the grid spines. The open end is then sealed by a polyethylene bar. Patents describe a procedure for making a type of tube for the tubular positive plate (90) and a method for filling tubular plates of lead—acid batteries (91). Tubular positive plates are pickled by soaking in a sulfate solution and are then cured. Some proceed directiy to formation and do not requite the curing procedure. 

In the lead-acid battery, sulfuric acid has to be considered as an additional component of the charge-discharge reactions. Its equilibrium constant influences the solubility of Pb2+ and so the potential of the positive and negative electrodes. Furthermore, basic sulfates exist as intermediate products in the pH range where Fig. 1 shows only PbO (cf. corresponding Pour-baix diagrams in Ref. [5], p. 37, or in Ref. [11] the latter is cited in Ref. [8]). Table 2 shows the various compounds. 

Finally, one development results from returning to a basic idea from the dawn of the lead-acid battery, wherein the functions of support for the positive active material and of the separator are combined into one component the gauntlet separator [84] consisting of a coarsely porous, flexible support structure coated with micropo-rous polyethylene material for separation. The future has to show whether this approach will be able to meet all demands. 

Let us note finally, that tellurium has been considered as an appropriate component for the lead grid alloy in lead-acid batteries, as improving its durability, mechanical strength, and anti-corrosive ability. In investigating Pb-Te binary alloys with different contents of Te (0.01-1.0 wt%) in sulfuric acid solution it was shown recently [104] that the introduction of Te can inhibit the growth of Pb02 and increase corrosion resistance of the positive grid alloy of a lead-acid battery. By the... 

As a lead-acid battery discharges, lead sulfate builds up at both terminals, and water builds up in the electrolyte. The reactions in a lead-acid battery, however, are reversible. When electrical power is applied to the battery, the flow of electrons is reversed. They now flow from the positive terminal to the negative terminal. 

---