Lead-Acid Battery Technologies 3 Electrolyte

The valve regulated lead acid battery is an important development in lead acid battery technology. These batteries operate on the principle of oxygen recombination, using a starved or immobilized electrolyte. The oxygen generated at the... 

The classical scheme for the manufacture of flat pasted plates for automotive, traction and stationary lead-acid batteries is shown in Fig. 3.1. There is no difference between the technology of plate manufacture for conventional (flooded) and valve-regulated (VRLA) lead acid batteries. The two versions do differ, however, in the method of separation of the plates, the quantity and type (hquid or gel) of electrolyte, and in the design of the battery itself. 

Plante discovered the basic technology of the rechargeable lead-acid battery in 1859. Since then there have been many refinements to the materials used, but the operating principles remain the same. This battery is the widely used car battery in use to this day. The anode is lead (Pb), the cathode lead dioxide (Pb02) and the electrolyte is dilute sulphuric acid [H2S04(aq)l (Figure 9.9). As with all... 

Industry and Business. Because of the widespread need for electrochemical cells and batteries, companies manufacturing them have devoted extensive human and financial resources to the research, development, and production of a variety of batteries. Some companies, such as Exide Technologies, have emphasized lead-acid batteries, whereas General Electric, whose corporate interest in batteries goes back to its founder, Thomas Alva Edison, has made fuel cells a significant part of its diversified line of products. Some businesses, such as Alcoa, the world s leading producer of aluminum, were based on the discovery of a highly efficient electrolytic process, which led to a dramatic decrease in the cost of aluminum and, in turn, to its widespread use (it is second only to steel as a construction metal). 

About 40Z of the world s lead production goes into the manufacture of the lead acid battery, and it is by far the dominant technology in rechargeable battery systems with market size of about 12 billion. The earliest reference on this battery is from 1854 (5), while the real commercial breakthrough came with Plante s experiments in 1859(4). Gaston Plante had been investigating the effect of polarization on different metals and he noticed the unique behavior of lead plates in dilute sulphuric acid as the electrolyte, and the rest is history. 

The principle is well known from sealed lead acid batteries, which contain their electrolyte immobilized, by glass mats or silica gel. For lithium rechargeable batteries it is called SPE (solid polymer electrolyte) or gel technology. 

Axion Power International Inc. has developed a PbC capacitor battery, as shown in Figure 1.34. The full technical description of Axion s proprietary PbC technology is a multi-celled asymmetrically supercapacitive lead-acid-carbon hybrid battery. Like a lead-acid battery, the PbC battery consists of a series of cells. Within the individual cells, however, the construction is more complex. Whereas the negative electrodes in lead-acid batteries are simple sponge lead plates, the negative electrodes in a PbC battery are five-layer assemblies that consist of a carbon electrode, a corrosion barrier, a current collector, a second corrosion barrier, and a second carbon electrode. These electrode assemblies are then sandwiched together with conventional separators and positive electrodes to make the PbC battery, which is filled with an acid electrolyte, sealed and connected in series to the other cells [11]. 

The sealed gel technology was developed a number of years ago by the Sonnenschein Company in West Germany. Simply stated, a gel cell is a lead-acid battery that uses a thick chemotropic gelled electrolyte that is the consistency of candle wax once it sets up and is pressurized and sealed using special valves. It uses a recombination technique to replace the oxygen and hydrogen normally lost in a wet-cell battery, and it is maintenance free and nonspillable [7,28]. 

Figure 184 Recombination technology in lead-acid batteries. In a conventional cell, oxygen from the positive plate rises to the top of the electrolyte and is lost. In a cell utilizing recombination electrolyte (RE) technology, oxygen passes throughthe special separatorto the negative plate and, ultimately, back Into the electrolyte (Courtesy of Yuasa)...

At open circuit, electrode reactions that charge the electrodes lead to a slow oxidation of the electrolyte with H2 evolution at the anode and O2 evolution at the cathode. These reactions represent an irreversible self-discharge. Once the electrolyte is introduced, the battery has a poor shelf life. Under development are acidic aqueous electrolytes in which Pb(II) is soluble rather than condensing into the solid PbS04. This development of the lead-acid cell promises a flow battery not requiring a separation membrane. The separation membrane of redox-flow batteries (see last section) remains a challenging problem for the aqueous redox-flow technology. 

Significant effort has gone into the development of many advanced batteries for these applications. In recent years, decisions were made to focus on lead-acid, nickel-metal hydride, and lithium-ion. These technologies have become the most likely to be used in either EVs or HEVs due to a combination of performance capability, safety, life, and cost. Earlier development of high temperature and flowing electrolyte technologies for EVs or HEVs has been mostly redirected or discontinued due to these decisions. 

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