Electrically Rechargeable Zinc-Air Batteries

For the development of a long-lived, electrically rechargeable zinc-air battery, the structure and wettability of pasted zinc electrodes (with 1-10% cellulose) were optimized [330]. It was found that the addition of 10 wt % cellulose to the pasted zinc electrode, improved the life cycle and peak power drain capacity of the battery substantially. 

Fig. 13.45. Schematic view of the Zn-air battery consisting of a single cell with a central Zn anode facing two bifunctional air electrodes. (Reprinted from K. Muller, R. Holze, and O. Haas, Progress Towards a 20 Ah/12V Electrically Rechargeable Zinc/Air Battery, in Batteries for Portable Applications and Electric Vehicles, C. F. Holmes and A. R.

Fig. 13.46. Zinc-oxygen cell voltages and available capacity for different rates of discharge measured for two 25-cm2 cells with pasted zinc electrodes containing 10 wt.% cellulose fibers with a fiber length of 1 mm. Discharge currents are x, 0.064 A o, 0.3 A a, 0.6 A a, 0.9 A , 1.2 A. (Reprinted from K. Muller, R. Holze, and O. Haas, Progress Towards a 20 Ah/12V Electrically Rechargeable Zinc/Air Battery in Batteries for Portable Applications and Electric Vehicles, C. F. Holmes and A. R. Landgrebe, eds., Electrochemical Society Proc. PV 97-18, pp. 859-868, Fig. 3,1997. Reproduced by permission of The Electrochemical Society, Inc.)...

Electrically rechargeable zinc/air batteries use a bifiinctional oxygen electrode so that both the charge process and the discharge process take plaee within the battery structure. 

FIGURE 38.22 Electrically rechargeable zinc/air battery, (a) Representative discharge profile, 1-A discharge, (b) Representative charge profile, 1.25-A charge followed by 0.5-A charge. Courtesy of AER... 

FIGURE 38.23 Prototype electrically rechargeable zinc/air battery for notebook computer. (Courtesy of AER Energy Resources, Inc.)... 

TABLE 38.9 Physical and Electrical Characteristics of Electrically Rechargeable Zinc/Air Battery... 

A. Karpinski, and W. HaUiop, Development of Electrically Rechargeable Zinc/Air Batteries, Proc. 38th Power Sources Corf., Cherry Hill, NJ, 1998. 

A. Karpinski, W. Halliop, Development of electrically rechargeable zinc/air batteries, in Proc. 38th Power Sources Conf., Cherry HUl, NJ, 1998. 

Fig. 9.19 Schematic diagram of a filling station for electric vehicles powered by mechanically rechargeable zinc-air batteries. (By permission of Edison.)...

Zinc is the most electropositive element that can be electrochemically deposited in aqueous solution. Consequently, the zinc/air cell has the highest voltage among electrically rechargeable metal/air batteries. It is the combination of this fact with zinc low equivalent weight, large terrestrial abundance and low cost, that has stimulated significant research and development activity on zinc/air batteries for electric vehicle applications [14]. 

Zinc is also attractive for electrically rechargeable metal/air systems because of its relative stability in alkaline electrolytes and also because it is the most active metal that can be electrodeposited from an aqueous electrolyte. The development of a practical rechargeable zinc/air battery with an extended cycle life would provide a promising high-capacity power source for many portable applications (computers, communications equipment) as well as, in larger sizes, for electric vehicles. Problems of dendrite formation, nonuniform zinc dissolution and deposition, limited solubility of the reaction product, and unsatisfactory air electrode performance have slowed progress toward the development of a commercial rechargeable battery. However, there is a continued search for a practical system because of the potential of the zinc/air battery. 

Rechargeable zinc-air batteries have been investigated for both portable and electric-vehicle applications, but their commercial applications are still hindered by various technical problems, including zinc re-plating during the charge process and the development of an efficient high-rate, bi-functional air electrode. More details of these batteries are discussed below. 

A variety of primary zinc-air cell and batteries are designed with capacity ranging from 100 Ah to 3300 Ah, operating at nominal currents from 2 to 40A at temperatures in the range +40 -t- -40°C. Mechanically rechargeable zinc-air cell are also developed and tested in experimental electric cars and scooters. 

Other battery technologies include sodium-sulfur which was used in early Ford EVs, and zinc-air. Zinc appeared in GM s failed Electrovette EV in the late 1970s. Zinc-air batteries have been promoted by a number of companies, including Israel s Electric Fuel, Ltd. Zinc is inexpensive and these batteries have six times the energy density of lead-acid. A car with zinc-air batteries could deliver a 400 mile range, but the German postal service found that these batteries cannot be conventionally recharged. 

Most of the batteries being considered for electric cars take several hours to recharge, a major drawback in comparison to the ease of refilling a gas tank. It is possible that the use of zinc-air batteries will avoid this problem. The reactions are not directly reversible in the zinc-air batteries, so the... 

The zinc-air battery shows much promise for electric cars because it is lightweight and rechargeable ... 

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