A 150-year-old technology looks to the future
LEAD-ACID batteries seem to have been around for ever. They were invented in 1859 by Gaston Planté, a French physicist, and have done sterling work over the decades starting car engines and powering slow-moving vehicles such as fork-lift trucks and milk floats. Compared with the newer energy technologies that are now sweeping the world, however, it has to be admitted that they look old-fashioned and a bit frumpy. These days the catwalk is crowded with nickel-metal hydride and lithium-ion batteries, showing off their ability to pack a lot of energy into a small space and deliver a steady current over a long period. The fact that these modern batteries are also lighter (lead is, after all, one of the densest elements in the periodic table) has made them the first choices for powering truly serious electric vehicles, as opposed to the ones that potter about warehouses and suburban streets.
It is, nevertheless, a mistake to dismiss something just because it is old. Another way of looking at things is that lead-acid batteries are tried and trusted. They may just need a bit of pepping up. And that is what is now happening. Axion Power, a firm based near Pittsburgh, Pennsylvania, has found that the ideal tonic is carbon.
A conventional lead-acid battery is a simple affair, made up of a series of cells each containing a positive electrode made of lead dioxide and a negative electrode of metallic lead. These are immersed in an electrolyte of dilute sulphuric acid. Car batteries tend to have thin electrode plates, which allows a lot of energy to be discharged quickly, but only for a short period of time. That is fine for turning a starter motor, but it is not so good for turning an electric motor intended to move a car any distance. Moreover, a lead-acid battery can be ruined if it is discharged completely, as many motorists discover to their cost when trying to start their car on an icy morning. Lead-acid batteries with thicker electrodes can tolerate such "deep" discharges better than those with thin ones, but only at the expense of making a heavy battery even heavier.
In Axion's battery the negative electrode is replaced with one made from activated carbon, a material used in supercapacitors. Normal capacitors—those that power the flashguns in cameras for instance—can be charged and discharged rapidly, but cannot store much energy. Supercapacitors are meatier versions that are able to hold a reasonable amount of energy as well as taking it in and releasing it quickly. Some, indeed, are already used in tandem with the lithium-ion batteries in electric cars to boost acceleration and recapture energy during so-called "regenerative" braking. Axion's plan, therefore, is to have the best of both worlds by building a lead-acid/carbon hybrid, or PbC.
http://www.economist.com/science/tm/displayStory.cfm?story_id=12924031&source=hptextfeature
http://www.axionpower.com/profiles/...1&BzID=1933&to=cp&Nav=0&LangID=1&s=0&ID=10299
LEAD-ACID batteries seem to have been around for ever. They were invented in 1859 by Gaston Planté, a French physicist, and have done sterling work over the decades starting car engines and powering slow-moving vehicles such as fork-lift trucks and milk floats. Compared with the newer energy technologies that are now sweeping the world, however, it has to be admitted that they look old-fashioned and a bit frumpy. These days the catwalk is crowded with nickel-metal hydride and lithium-ion batteries, showing off their ability to pack a lot of energy into a small space and deliver a steady current over a long period. The fact that these modern batteries are also lighter (lead is, after all, one of the densest elements in the periodic table) has made them the first choices for powering truly serious electric vehicles, as opposed to the ones that potter about warehouses and suburban streets.
It is, nevertheless, a mistake to dismiss something just because it is old. Another way of looking at things is that lead-acid batteries are tried and trusted. They may just need a bit of pepping up. And that is what is now happening. Axion Power, a firm based near Pittsburgh, Pennsylvania, has found that the ideal tonic is carbon.
A conventional lead-acid battery is a simple affair, made up of a series of cells each containing a positive electrode made of lead dioxide and a negative electrode of metallic lead. These are immersed in an electrolyte of dilute sulphuric acid. Car batteries tend to have thin electrode plates, which allows a lot of energy to be discharged quickly, but only for a short period of time. That is fine for turning a starter motor, but it is not so good for turning an electric motor intended to move a car any distance. Moreover, a lead-acid battery can be ruined if it is discharged completely, as many motorists discover to their cost when trying to start their car on an icy morning. Lead-acid batteries with thicker electrodes can tolerate such "deep" discharges better than those with thin ones, but only at the expense of making a heavy battery even heavier.
In Axion's battery the negative electrode is replaced with one made from activated carbon, a material used in supercapacitors. Normal capacitors—those that power the flashguns in cameras for instance—can be charged and discharged rapidly, but cannot store much energy. Supercapacitors are meatier versions that are able to hold a reasonable amount of energy as well as taking it in and releasing it quickly. Some, indeed, are already used in tandem with the lithium-ion batteries in electric cars to boost acceleration and recapture energy during so-called "regenerative" braking. Axion's plan, therefore, is to have the best of both worlds by building a lead-acid/carbon hybrid, or PbC.
http://www.economist.com/science/tm/displayStory.cfm?story_id=12924031&source=hptextfeature
http://www.axionpower.com/profiles/...1&BzID=1933&to=cp&Nav=0&LangID=1&s=0&ID=10299
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