Metal-air batteries use the oxygen in the air around them, rather than storing it in liquid or solid chemicals. They can store far more energy than most competing technologies. Not needing to contain the oxygen can also cut the weight dramatically – Phinergy claim that 70% of the weight in a conventional car battery is in the cathode, mostly just to store the oxygen. With such benefits, metal-air batteries have been a topic of research for some time. Lithium-air batteries have theoretical energy per weight almost as high as petrol. However, a range of practical problems have prevented widespread commercialization. Aluminum-air batteries dont have the same potential energy per kilogram of lithium-air battery, but could theoretically reach energy densities many times better than the lithium-ion batteries that are currently the industry standard. One of the challenges for metal-air batteries is to capture enough oxygen to provide the power required. Phinergys porous electrodes have the surface area to allow this. A silver-based catalyst prevents carbon dioxide from permeating the electrodes, a common problem for other experimental versions of this technology that reduces their lifespan to the point of impracticality. Like anything based on aluminum, there is a lot of embodied energy in Phinergys batteries, but they are manufacturing their products in Quebec, where the electricity is almost entirely sourced from hydroelectric stations, keeping the carbon footprint small. The big disadvantage of aluminum-air batteries is that they dont last. The aluminum turns to aluminum-hydroxide. While this can be recycled, it cant be recharged by plugging the battery into a powerpoint. Instead the whole battery will need to be replaced when the aluminum has been used up. Advocates of this system claim that battery swaps can be done quickly and easily. However, any battery that needs to be replaced so frequently is not only expensive, but runs into the problem that has bedeviled many alternatives to gasoline-powered cars. People are reluctant to buy vehicles that depend on the availability of refueling or replacement stations if these are not available everywhere they might be needed. On the other hand, without a critical mass of owners of suitable vehicles, such stations are not viable. Read more at iflscience/technology/new-metal-air-battery-drives-car-1800km-without-recharge#0cKlUtmL5YBfv8ov.99
Posted on: Tue, 17 Jun 2014 10:52:59 +0000
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