Phinergy, an Israeli startup, has demonstrated an aluminium-air battery that is capable of powering an electric vehicle for up to 1,000 miles (1,609km). Unlike other metal-air batteries that we’ve written about in the past, such as IBM’s lithium-air battery, Phinergy’s Al-air battery actually consumes aluminium as a fuel, allowing for an energy density that far surpasses conventional battery technologies and even begins to rival gas and diesel. Phinergy says it has signed a contract with a global automaker for “production volumes” of the battery, starting in 2017.
Metal-air batteries aren’t a new idea. Zinc-air is a very well understood battery chemistry that is used in hearing aids, and potentially in other biological implants. IBM is busy working on a lithium-air battery that, like Phinergy’s battery, is also targeted at long-range electric vehicles. In recent months, it has emerged that sodium-air might also be a viable battery chemistry. In all three cases, it is the air component that makes these batteries so desirable. In a conventional battery, the chemical reaction is entirely internal, which is why batteries tend to be very dense and heavy. In a metal-air battery, energy is produced by the oxidization of a metal — lithium, zinc, aluminium — with the oxygen coming from the air around us, rather than being stored in the battery, resulting in a much lighter battery.
Phinergy’s Al-air battery is novel for two reasons: First, the company seems to have found a way of preventing carbon dioxide causing corrosion damage to the aluminium. Second, the battery actually consumes the aluminium as a fuel, slowly turning the aluminium into aluminium oxide. Phinergy’s prototype Al-air battery has 50 aluminium plates, with each plate providing enough fuel for 20 miles. After 1,000 miles, the plates must be mechanically recharged — a euphemistic way of saying that the plates must be physically switched out. The Al-air battery must also be refilled with water every 200 miles, to replenish the electrolyte.
Depending on your point of view, mechanical recharging is both awesome and awful. On the one hand, you can give your car another 1,000 miles of range just by slotting in a new battery; on the other hand, buying a new battery every 1,000 miles sounds like very poor overall economy. Ultimately, it will probably come down to the price of the battery. At today’s market rate, a kilo of aluminium costs $2, and one pack of 50 plates weighs 25kg — so, ignoring labor costs, it would cost $50 to refill your Al-air battery. $50 to travel 1,000 miles is really rather good — at $4 per gallon of gas, that’s an equivalent of around 90 mpg. The aluminium oxide can be recycled back into aluminium, too, though it isn’t a particularly cheap or easy process.
For now, though, it seems like Phinergy is using its Al-air battery as a range extender, with a standard lithium battery as the primary energy source. In the video below, a Citroen C1 has been outfitted with a small lithium-ion battery that can power the car for a few dozen miles — and then an Al-air battery in the trunk that acts a range extender, feeding power to the Li-ion battery. Phinergy tells Green Car Reports that it has signed a contract with a global automaker to bring its Al-air battery to production cars in 2017, though it isn’t clear if the batteries will be used as a range extender, or as the primary power source. Presumably, though, the automaker will bundle the car with a monthly supply of aluminium plates, shipped to your doorstep.
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