At the moment, a Tesla Roadster can manage 245 miles on a single charge while taking four hours for the battery to completely recharge from empty. That’s pretty much the pick of the bunch though, and would set you back a cool £86,950. The more affordable Nissan Leaf (£25,990) will charge to its maximum range of just over 70 miles in just under four hours. Which is fine for short commutes, but pretty much rules out the Leaf and its rivals as a full-time permanent replacement for your petrol-guzzler.
So, if electric cars really are to be the future of motoring, it’s clear that their batteries need to shape up and fast. Fortunately, there are some exciting new technologies around the corner that might be able to help.
Carbon Nanotube Cathodes
Carbon nanotubes are tiny but super-strong hollow threads with a relatively large surface area compared to their size. In 2010, scientists from MIT demonstrated that these nanotubes could be used to make cathodes (which form one half of a conventional battery) capable of storing far more electrons than their current equivalents. What does that mean? The potential to create batteries with a capacity around ten times what’s currently available.
The carbon nanotubes used in the technology are already commercially available, making this a very real prospect. However, there’s a fair bit more testing and development needed to turn this into a commercially viable product, meaning it could be 5-10 years before we see these batteries on the market.
Lithium-Air Battery
Lithium-ion batteries are the best batteries currently in wide usage, but technology titans IBM think they can do one better with their concept for a lithium-air battery. The big selling point here is the ability to achieve a much higher energy density than with a lithium-ion battery. This is achieved by using carbon electrodes that react with oxygen without depleting the electrolyte medium, thus allowing the battery to hold much more charge.
IBM is being pretty cagey about exactly how they’ve achieved this improved performance but they are aiming to deliver a range of at least 500 miles which, if they can do it, would be truly game-changing. Sadly the technology is still a little way off, with most predicting it’ll be 2020 before we see it in commercially available vehicles.
Lithium Sulphur Carbon Nanofibre
Scientists at Stanford University believe that silicon could be the future of batteries, thanks to its ability to store greater numbers of lithium ions than most current electrode materials. Sulphur also has the advantage of being readily available and non-toxic, making it more environmentally friendly and, crucially, cheaper than the current standard materials.
So why hasn’t sulphur been used in batteries before? Because of the unfortunate fact that sulphur expands when absorbing ions, thus tending to cause the conductivity pathway to break, stopping the battery from working. However, the boys and girls at Stanford think they have an answer: nanofibres. But forming the cathode out of sulphur nanofibres, instead of using a more conventional form, they are able to significantly reduce the expansion effect delivering a useable lithium-sulphur battery with up to ten times the carry capacity of a conventional lithium-ion battery.
Carbon Foam Battery-Capacitor Hybrid
Although batteries are the standard energy storage device of choice for current electric vehicles, there is a potential alternative − capacitors. Capacitors store energy physically, can be charged very rapidly and can be charged and discharged almost indefinitely without losing any of their carrying capacity. On the downside, they also tend to lose their charge quickly and, in practice, only deliver about half of their charge for actual use.
Batteries, on the other hand, store energy chemically, are slow to charge and tend to lose capacity over time as they are repeatedly charged and discharged. However, they are good at storing energy effectively for long periods of time and deliver nearly all of their capacity.
The answer: build a hybrid. And that’s exactly what researchers at Michigan Technology University are doing. Using a sort of “carbon foam” permeated with nickel oxyhydroxide as a cathode, paired with a capacitor style anode, the researchers have been able to produce a lightweight hybrid cell with the rapid charging ability of a capacitor but the ability to effectively store and deliver much more charge. It will also retain the capacitor’s ability to be charged over and over without losing a significant percentage of its carrying capacity.
So, with the potential for batteries that are lighter and green with much higher carrying capacities and lower charge times, it looks like the future’s bright for electric cars.
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