Aluminum-air batteries

Research the aluminum-air battery, and the sodium-sulfur battery. Both are rechargeable batteries that have been used to power electric cars. In each case, describe the design of the battery, the half-reactions that occur at the electrodes, and the overall cell reaction. Also, describe the advantages and disadvantages of using the battery as a power source for a car. 

Aluminum—air battery. A second potential application of this available energy is based on electrochemical oxidation of aluminum in air to produce electricity. In an aluminum—air battery, for example, thin coils of aluminum strip may be used as the fuel. No elech ic battery recharging would be required since the aluminum is consumed to generate the electricity directly. This fuel would not give off fumes or pollute and could be stored in solid form indefinitely. If this concept materializes into commercial viability, it will provide the energy needed for electric vehicles. 

The aluminum-air battery produces electricity by means of a 3e dissolution of A1 in an alkaline medium. The Al(OH)3 produced is to be recycled to Al. Consider the volume of the gas tank of a car to be that equivalent to 18 gallons of gasoline and that half of this space is occupied by Al in foil form which... 

Aluminum-air battery — A metal-air battery operating with an aluminum anode in a neutral or alkaline electrolyte solution. At the anode aluminum is oxidized according to... 

This phenomenon degrades the Coulombic efficiency of the anode, then it has to be minimized for practical applications where high capacity is required. This could be overcome by particular aluminum alloys more resistant to corrosion, but the competing requirement of fast anodic dissolution makes very difficult the research of the suitable material [36, 37]. Another possibility to improve the anode performance is to modify the electrolyte composition by adding corrosion inhibitors [38]. The difficulties met up today in this field leave the possibility to use the aluminum-air batteries only as mechanically rechargeable systems, with practical performance (300-500 Wh/kg) very far from the theoretical values (Table 1.8 Fig. 5.14). 

The design of aluminum-air cell allows assembling such cells in block from 10 pieces. Aluminum-air batteries have been developed, made and tested. The cells assembled in blocks have side slots across which air (oxygen) is fed in compulsory regime. Working area of electrode is 350 cm. Feeding electrolyte in each cell is carried out across system of pipe-wire from circulate pump stirring compensation of electrolyte. 

Electrochemical tests of aluminum-air battery consisting of 24 cells are made in solution of KOH (20 %). The voltage of battery was 18-20 V, working voltage was 10 V at load current 100-105 A. Aluminum-air battery with power 1 kW was elaborated for electrocar by Rotor (Cherkasy, Ukraine). 

The aluminum-air battery has recently received some attention as a result of work done by the Lawrence Livermore National Laboratory. It was estimated that a 60-cell system with 230 kg of aluminum can power a VW for 5,000 km before requiring mechanical recharging. Periodic refill with water and removal of Al(OH)3 would be required after 400 km. The conversion of the Al(OH)3 back to Al at an electrolytic refinery completes the recycling process. In 1986, an Al-air battery producing 1,680 W was shown to power an electric golf cart for 8 h. 

The above described principle of the zinc/air battery is not limited to zinc as negative electrode material. Under the name metal/air fuel cell the aluminum/air battery is claimed as a superior solution with an output of 320 to 400 Wh/kg (75). This means a considerable increase compared to the rechargeable zinc/air system (Line 3b in Table 1.11). 

Figure 7.1 Discharge characteristics of a modular aluminum-air battery.

The overall anodic reaction of the aluminum-air battery is the corrosion of aluminum into a soluble form stable in a caustic environment, AlO in Eq. (4.15), that can subsequently precipitate as Al O H O, as shown in Eq. (4.16), depending on the concentration of ions in solution, pH, and temperature. 

Aluminum active primary batteries were never produced commercially. While the experimental aluminum batteries delivered a higher energy output than conventional zinc batteries, anode corrosion, causing problems on intermittent and long-term discharges and irregularities in shelf Ufe, and the voltage-delay problem restrained commercial acceptance. Aluminum/ air batteries are covered in Chap. 38. 

E. J. Rudd and S. Lott, The Development of Aluminum-Air Batteries for Application in Electric Vehicles Final Report, Sandia National Laboratories, SAND91-7066, Dec., 1990. 

Aluminum is attractive for use because of its geological abundance (third most abundant element in the earth s crust), its potentially low cost, and its relative ease of handling. - However, the aluminum/air battery has too high a charging potential to be electrically recharged in an aqueous system (water is preferentially electrolyzed). Therefore the effort has been directed to reserve and mechanically rechargeable designs. 

Portable Aluminum/Air Batteries. A number of batteries using saline electrolytes have been designed. In general, they are built as reserve batteries and activated by adding the electrolyte to the battery. 

FIGURE 3832 Polarization curves of particulate-feed aluminum/air battery.----------------, positive... 

Applications of Alkaline Aluminum/Air Batteries. The alkaline aluminum/air batteries being developed cover a wide range of applications from emergency power supplies to field-portable batteries for remote power applications and underwater vehicles. Most of these are designed as reserve batteries, which are activated before use, or mechanically recharged by replacing the exhausted aluminum anodes. 

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