Aluminium–air batteries or Al–air batteries produce electricity from the reaction of oxygen in the air with aluminium. They have one of the highest energy densities of all batteries, but they are not widely used because of previous problems with cost, shelf-life, start-up time, and byproduct removal.
Metal/Air batteries using aqueous electrolytes are well known with iron/air, zinc/air and aluminum/air being the most studied. In particular the zinc/air battery has been commercialized, primarily for hearing aid devices and pagers.
ELTECH Systems Corporation has operated research programs on aluminum-air or -oxygen batteries and components since 1980. The ultimate goal of this endeavor is the development of a battery for electric vehicles which will overcome these limitations. The high specific energy density of aluminum-air (300+ W h lb^-1 Al) and power density (26 - 30 W lb^-1 peak), as well as the feature of mechanical rechargeability, have made its application to an electric automobile viable and attractive. The battery is returned to its fully charged state by replacement of aluminum into the cell stack, replenishment of the oxygen supply (if necessary), addition of water, and removal of the aluminate discharge product.
Aluminum-air batteries obtain their energy from the interaction of aluminum with air. The incoming air must be filtered, scrubbed of CO2, and dehumidified; the water and electrolyte must be pumped and maintained within a narrow temperature range - hence the complexity of the battery. The batteries are not electrically recharged but are "refueled" by replacing the aluminum anodes and the water supply.
With its low cost, low environmental impact and safety aspects, the Al-air system has potential to serve as a near-term power source for electric vehicles, according to a research team from The University of Hong Kong and Hong Kong Polytechnic University.
However, they note, parasitic hydrogen evolution caused by anode corrosion during the discharge process is a well-known obstacle to commercialization of the system, because it not only causes additional consumption of the anode material but also increases the ohmic loss in the cell.
Metal-air batteries are the most compact and, potentially, the least expensive batteries available. They are also environmentally benign. The main disadvantage, however, is that electrical recharging of these batteries is very difficult and inefficient. Although many manufacturers offer refuelable units where the consumed metal is mechanically replaced and processed separately, not many developers offer an electrically rechargeable battery.
The BCC report states "Because of the long shelf life, stability, safety, drain time, energy density, power and environmentally benign character of aluminum-air fuel cells, they are positioned to take a significant market position in the world of premium power sources." The report elaborates on Trimol Group's technology stating that its "aluminum-air fuel cells offer realistic market opportunities.
The technology extends the range of a vehicle powered by lead-acid batteries - currently about 75 kilometres - to at least 300 kilometres without being recharged.
Mr. Jackson said the aluminum-air fuel cell is energy dense, light, non-polluting, safe and recyclable. A centimetre-thick sheet of aluminum alloy is immersed in an alkaline solution and then interacts with oxygen to free its stored energy as electricity. The aluminum must periodically be replaced.
Alupower Canada was formed last year as a spin-off company of Alcan with the express purpose of designing and developing an aluminum battery for application in transportation, marine or standby power supply systems.
The battery generates power through a simple reaction between the aluminum, once immersed in an elctrolytic solution, and oxygen from the air. Electricity is produced as the aluminum oxidizes.
This was an aluminum-air battery, which uses common materials, keeps nothing under pressure, develops little or no heat, runs an amazingly long time, and can be recharged in minutes with no need to plug it in anywhere.
This is one of those ideas that sounds too good to be true, yet it's proving out. And the people developing it are not obscure theorists with no credentials. The giant Lawrence Livermore National Laboratory in California, working for the U.S. Department of Energy, co-ordinated early research, subcontracting a lot of it to the Alcoa and Reynolds aluminum companies and to Lockheed. But Canadian-based Alcan International seems to have taken the lead in this field now, through a subsidiary named Alupower.
When Nikola Tesla first proposed using aluminum air batteries as a way to deliver power to households in America the idea was ridiculed as another of his wild ideas. In reality the power companies that he had helped create with his alternating current (AC) delivery system were the power behind the discrediting of this idea. Again Tesla was a hundred years before his time.