Zinc electrically rechargeable

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. 

Mechanically Rechargeable Batteries. To avoid the time required for electric recharge, the problems of in silu electric recharge, or to utilize anodes that are not electrically rechargeable in aqueous electrolytes, mechanically rechargeable batteries have been studied. These systems arc metal-air couples. Ihe anodes that have received attention arc zinc, lithium, and aluminum. 

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.)...

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]. 

Another category of aqueous battery systems is the metal-air battery. These batteries are noted for their high specific energy as they utilize ambient air as the positive active material, and light metals, most commonly aluminum or zinc, as the negahve achve material. Except for the iron/air battery, on which earlier development work for EV applications has now been abandoned, metal-air batteries have either limited capability for recharge, as for zinc/ air, or they cannot be electrically recharged at all, as in the case of the aluminum/air system. 

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. 

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 38.19 Basic operation of electrically rechargeable zinc/air cell. (Courtesy of AER Energy Resources, Inc.)... 

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... 

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. 

The zinc-air system is rechargeable by two methods electrical and mechanical. For the electrical rechargeability method, electricity is applied to the cell to convert the zinc oxide species back to zinc metal (or the zinc metal alloy) and oxygen gas. The reactions involved in recharging the cells are below. 

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

Haas, O. and Van Wesemael, ). (2009) Secondary Batteries-Metal-Air Systems Zinc-Air Electrical Recharge,... 

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