Mechanical recharge

The second and the third papers of this chapter were contributed by Bulgaria s National Academy of Sciences distinguished developers, Dr. A. Kaisheva and Professor I. Iliev. The two papers address magnesium-air and zinc-air chemistries, respectively. Concepts of mechanical recharging, new non-KOH based electrolytes, and the role of carbon materials in cell design have been thoroughly studied. Authors have reduced to practice their many developments. Systems created work(ed) in many specialty applications. 

MECHANICALLY RECHARGEABLE MAGNESIUM-AIR CELLS WITH N aCl-ELECTROLYTE... 

Zinc is commonly used as an anode in metal-air batteries. Zinc-air batteries are commercially available and used as power supply for navigation buoys, communication systems, hearing aids, and etc. [2], Mechanically rechargeable Zn-air batteries are developed recently for traction [3],... 

Mechanically rechargeable magnesium-air cells were designed and investigated. The most important feature of these cells is that the cell-case with the air electrodes can be used many times. 

Figure 7. Current-voltage characteristics of one and the same Mg-air cell initial and after 12th mechanical recharge.

The initial current-voltage curve and the current-voltage curve after 12th mechanical recharge of one and the same Mg-air cell are presented in Fig. 7. The results show that the Mg-air cell can be recharged mechanically several times without any significant loose in its performance. 

Two types of mechanically rechargeable Mg-air cells for operation at high nominal currents are designed. The air electrodes in these cells are with pyrolyied CoTMPP catalyst. Mg anodes from the alloy MA8M06 were used in this design. 

Figure 10. Current-voltage and power characteristics of the mechanically rechargeable Mg-air cell (S = 660 cm2).

Mechanically rechargeable Mg-air cells for operation in middle and high nominal current were designed. 

The main advantage of the magnesium-air cells is the use of NaCl-electrolyte. This makes the magnesium-air cells environmentally friendly. They are clean, no toxic emission are produced in a way that is safe for user, even for children because the NaCl-electrolyte is not chemically aggressive and magnesium is not toxic. The mechanical recharging of these cells can be accomplished without any chemical danger. 

From the presented results it can be concluded that the magnesium-air cells feature substantially increased power output. They can be used as primary, mechanically rechargeable and emergency energy sources for the residential, commercial and industrial markets. 

Iliev I., Kaisheva A., Stoynov Z. Pauling H.J, Mechanically rechargeable Zinc-air cells, Proceedings of the 3th International Battery Recycling Congress, July 2 - 4, 1997, Noordwijk Aan Zee, the Netherlands. 

Kaisheva A., Iliev I., Milusheva J. Mechanically rechargeable magnesium-air cells with non-aggressive electrolyte. International Congress for Battery Recycling, July 3-5, 2002, Vienna, Austria. 

In Fig. 17 we have presented the current-voltage and the power characteristics of 12-cells battery from the cells type ZV300. It must be reminded that, when the zinc anode in the primary zinc-air cells is discharged, the cell is out of operation. By this, the air electrodes, which in principle can operate for a long time, are lost. In order to avoid this inconvenience, mechanically rechargeable zinc-air cells were developed [14]. The essential feature of the mechanically rechargeable zinc-air cell is that the air electrodes are used many times. 

Once the mechanically rechargeable zinc-air cell is discharged, the spend (oxidized) zinc electrode is removed from the cell together with the electrolyte and new zinc electrode and fresh electrolyte are introduced by which the cell is operational again. 

Several types of mechanically rechargeable zinc-air cells are developed in this laboratory, operating at nominal current 20A + 40 A with capacity ca.300 Ah. 

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. 

Problems of the metal-air batteries and air electrode are considered. Results of research, design work and development of the air - Zn primary and air-Al mechanically rechargeable batteries, as well as electrically rechargeable electrodes are presented. 

Anode Primary Batteries Mechanically Rechargeable Batteries Electrically rechargeable batteries... 

AIR-ALUMINIUM MECHANICALLY RECHARGEABLE BATTERIES WITH SALINE ELECTROLYTE... 

Air-Zn primary and air A1 mechanically rechargeable batteries with carbonaceous air electrodes were designed and tested. Air Zn batteries are mostly used in the hearing aids, while air-Al batteries find wider range of applications in the portable devices. Electrically rechargeable air electrodes with pyropolymer catalyst have been developed. 

Mechanically rechargeable batteries, 3 518 Mechanical needling, 17 475 Mechanical properties. See also Physical properties... 

The cell uses a replaceable anode cassette made up of a slurry of elec-trochemically generated zinc particles in a potassium hydroxide solution with a collection frame and a separator envelope with two sides of oxygen reduction cathodes that extract oxygen from the air for the zinc-oxidation reaction. The discharged zinc-air module is refueled or mechanically recharged by exchanging spent cassettes with fresh cassettes. 

Mechanically Rechargeable Zinc—Air Battery , ECOM 3086 (1969) 11) C.L. Mantell, Bat-... 

Fig. 3.30 Cross-section of the electrode assembly of an early 500 Ah mechanically rechargeable zinc-air wet cell used for railway signalling applications...

Aluminium-air cells are attractive in principle because of the high thermodynamic electrode potential and theoretical capacity of aluminium. Because of corrosion, however, the only commercial power sources based on this couple are either reserve systems or are mechanically rechargeable, i.e. the anodes are replaced after discharge. A typical cell may be written as... 

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

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. 

A mechanically rechargeable battery can be seen as a primary, for it is not electrically rechargeable as a unit. The metal fed into it becomes a fuel and the battery is then like a fuel cell. 

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