01net wrote:Smaller, more powerful and more enduring, the batteries of tomorrow will owe their performance to their electrodes, designed with materials to say the least original ...
Many scientists believe that today's rechargeable batteries have reached their limits. In terms of power, manufacturing cost, lifespan, but also comfort of use: they must be recharged frequently and for several hours ... And they are not the owners of laptops, mobiles, PDAs or players that will contradict them!
Almost instant charging
The fuel cell should make it possible to push these limits, which has earned it the status of the battery of the future. But researchers continue to bet on traditional batteries and, for some, bet on electric accumulators like capacitors (or supercapacitors), the principle of which is to store electricity between two electrodes. It is moreover these electrodes which are the subject of all their attention, because they influence the storage capacity of an accumulator. Without giving themselves the word, French and American researchers thus had the same idea: to use new materials to manufacture these electrodes, while following different tracks: algae at CNRS, nanotubes at MIT, plastic at Brown University ...
Their first prototypes, very promising, make it possible to envisage the production of accumulators smaller than the current rechargeable batteries, up to a hundred times more powerful, capable of recharging in a few moments, and with much greater autonomy. Accumulators which will prove, moreover, more economical and more ecological because without heavy metals dangerous to handle - and harmful to the environment - like lithium.
Fortified to plastics
Incredible, but true: a battery that charges as quickly as a capacitor ... and uses plastic as an electrical conductor! This is the result of research carried out by Brown University in Rhode Island. To achieve this feat, American scientists mixed two different plastics - polymers discovered by the three Nobel Prize winners in chemistry awarded in 2000 - with a substance that corrects their properties. A strip of plastic film covered with gold was coated with one of the modified polymers; and a second, on the other. The two strips were pressed against each other, simply separated by a thin insulating membrane. Result: not only does this prototype battery charge in a few minutes, but it is also smaller than a standard alkaline battery, for a power hundred times greater!
Thanks to its plastic electrodes, the Brown University battery recharges in just a few minutes.
Seaweed fed
A supercapacitor which would keep 85% of its nominal capacity after being recharged 10 times, ie a lifespan at least ten times longer than that of a lithium battery! This is the result of the Center for Research on Divided Matter (CRMD), a joint unit of the CNRS and the University of Orléans. To achieve this, the research team, led by François Béguin, turned to the sea, and more particularly to brown algae. Because alginic acid, a fibrous substance located in their cell wall, offers an interesting property: it is naturally rich in oxygen, and remains so after being reduced by cooking in the state of carbon. Even richer than activated carbon, the main component of the two electrodes of a traditional supercapacitor! However, the oxygen trapped in these electrodes allows them to absorb the current more easily.
Researchers tested their theories using charred alginic acid (sodium alginate) salts to make electrodes. Knowing that the extraction of sodium alginate is an activity that is already in full swing (the food and pharmaceutical industries gobble up more than 20 tonnes each year), that its transformation into coal costs less than the production of activated carbon , and that it is more ecological, the use of algae may well be widespread ...
It is a brown alga of the same family as this one (the variety is kept secret) which makes it possible to manufacture the indestructible electrodes of the CNRS.
Swollen with nanotubes
The Massachusetts Institute of Technology (MIT) capacitor would be more powerful than a battery of the same size! When we know that the most efficient current capacitors store 25 times less energy than a chemical battery of equivalent size, we measure the scope of the project on which MIT is working. The idea of American researchers? Cover the electrodes of the capacitors with millions of small carbon tubes, thirty thousand times thinner than a hair: nanotubes.
A process that overcomes the main handicap of the capacitor: its capacity to store energy is proportional to the area of its electrodes, which, in other words, means that the smaller its electrodes, the less it can store electricity. By covering its electrodes with nanotubes, we increase, in a certain way, their surface; a bit like a terry towel which, thanks to its honeycomb fibers, manages to contain much more water than a simple piece of fabric ... With the result of considerably increasing the storage capacity of the condenser.
The millions of carbon nanotubes lining each electrode of the MIT capacitor transform it into a real electric sponge.
source: 01net