Science! By Graham Templeton Nov. 21, 2013 8:30 am
Lithium-air (or Li-air) batteries have the capacity to more than triple the energy density of today’s lithium-ion batteries, mostly because they can outsource one of their two main reactants to the atmosphere itself. By using free oxygen in the air as the cathode oxidant, a Li-air battery’s whole volume can be used for the energy-storing lithium solution. Between that huge advantage and some basic chemical efficiency increases, Li-air batteries have enough potential that some researchers have even discussed their use for grid power storage.
A new study from MIT now claims that by using a specially engineered virus, the scientists at the university have figured out how to get around some of the biggest impediments to Li-air’s widespread adoption.
When you double the volume of the reactants, you introduce strains on the battery. Charge times go through the roof, and the chemical strain on the electrode means the lifetime number of charge-discharge cycles plummets as well. The anode simply have trouble dealing with the strain, and their overall surface area is too low to efficiently move the amount of energy a Li-air battery can store. Increasing the surface area of the anode isn’t easy, though; the nanowires used in many batteries already stretch the limits of chemical fabrication technologies. However, genetic engineering offers a possible solution, since with DNA we can try to program assembly robots that work at the nanometer scale.
In this case, the researchers used a virus called M13, which can pick up metal molecules in solution and lay them down in specific structures. By engineering the virus just so, the researches were able to get it to deposit metal ions onto a template wire in a complex, multi-branched structure that greatly increases the wire’s overall surface area. More surface area means more room to carry out the reaction, and thus faster throughput for energy in both directions; this should allow Li-air batteries to charge and discharge on more practical, everyday time-frames.
Another big advantage of the M13 nanowires is that the virus tends to build them in interwoven networks that greatly increase their durability. This means that one of Li-air’s biggest drawbacks — that they offered far fewer recharge cycles than competing techs like lithium-ion — could be at least partially solved. The researchers seem to see their bi0-manufacturing breakthrough as a precursor to actual bio-batteries which would maintain a viral population throughout their life, presumably to rebuild the wires as needed. More realistic in the short-term, though, is a place for M13 on the factory floor.
One particular side-advantage of this work is that the virus can be made to incorporate small amounts of expensive metals like palladium to significantly increase the conductivity, allowing it to catalyze reactions in the charge and discharge process. Past researchers have tried to achieve this by using large amounts of pure metal samples but the costs are prohibitive for large-scale manufacturing. This virus can achieve many of the same advantages, but do it with a much smaller amount of precious metals, bringing down the costs of overclocking Li-air batteries for specific, high-throughput applications.
There’s still a ways to go for Li-air technology though. This study did a 50-round charge-discharge test with positive results, but any practical technology would need to be resilient through thousands of such cycles. There’s no telling if the viral nanowires have been made that much more durable, but this is at least a strong step in that direction. A high-capacity battery like Li-air could unequivocally break the range advantage still enjoyed by combustion vehicles over electric, and it could allow batteries to similarly out-compete fossil fuels in all sorts of different areas.
Bacteria, fungi, and viruses have huge potential for manufacturing, especially as we learn how to more specifically control their behavior through DNA.
Now read: LG has a curved battery to complement its curved smartphone display
More...
A new study from MIT now claims that by using a specially engineered virus, the scientists at the university have figured out how to get around some of the biggest impediments to Li-air’s widespread adoption.
When you double the volume of the reactants, you introduce strains on the battery. Charge times go through the roof, and the chemical strain on the electrode means the lifetime number of charge-discharge cycles plummets as well. The anode simply have trouble dealing with the strain, and their overall surface area is too low to efficiently move the amount of energy a Li-air battery can store. Increasing the surface area of the anode isn’t easy, though; the nanowires used in many batteries already stretch the limits of chemical fabrication technologies. However, genetic engineering offers a possible solution, since with DNA we can try to program assembly robots that work at the nanometer scale.
In this case, the researchers used a virus called M13, which can pick up metal molecules in solution and lay them down in specific structures. By engineering the virus just so, the researches were able to get it to deposit metal ions onto a template wire in a complex, multi-branched structure that greatly increases the wire’s overall surface area. More surface area means more room to carry out the reaction, and thus faster throughput for energy in both directions; this should allow Li-air batteries to charge and discharge on more practical, everyday time-frames.
Another big advantage of the M13 nanowires is that the virus tends to build them in interwoven networks that greatly increase their durability. This means that one of Li-air’s biggest drawbacks — that they offered far fewer recharge cycles than competing techs like lithium-ion — could be at least partially solved. The researchers seem to see their bi0-manufacturing breakthrough as a precursor to actual bio-batteries which would maintain a viral population throughout their life, presumably to rebuild the wires as needed. More realistic in the short-term, though, is a place for M13 on the factory floor.
One particular side-advantage of this work is that the virus can be made to incorporate small amounts of expensive metals like palladium to significantly increase the conductivity, allowing it to catalyze reactions in the charge and discharge process. Past researchers have tried to achieve this by using large amounts of pure metal samples but the costs are prohibitive for large-scale manufacturing. This virus can achieve many of the same advantages, but do it with a much smaller amount of precious metals, bringing down the costs of overclocking Li-air batteries for specific, high-throughput applications.There’s still a ways to go for Li-air technology though. This study did a 50-round charge-discharge test with positive results, but any practical technology would need to be resilient through thousands of such cycles. There’s no telling if the viral nanowires have been made that much more durable, but this is at least a strong step in that direction. A high-capacity battery like Li-air could unequivocally break the range advantage still enjoyed by combustion vehicles over electric, and it could allow batteries to similarly out-compete fossil fuels in all sorts of different areas.
Bacteria, fungi, and viruses have huge potential for manufacturing, especially as we learn how to more specifically control their behavior through DNA.
Now read: LG has a curved battery to complement its curved smartphone display
More...
