One of the disadvantages of electric cars is their limited range. Hybrid cars overcome that problem, but to do so they need to turn on their petrol or diesel engine, so they are not as efficient as they might be if the batteries that powered these vehicles had a longer range. For many years research has been carried out on improving battery lifetimes, and in the laboratory there have been significant breakthroughs, but to date they have not been translated to real life situations.
However a recent development promises to produce batteries that can power an electric car with a range of nearly 400 miles, about the same or even better than many conventional petrol and diesel powered cars. If this really does provide what it promises, the impact on electric car sales will be huge. No longer will car owners suffer from what is called range anxiety, which is the fear that they will run out of power before they complete their planned journey, and apparently the main reason for the currently low sales volumes.
In a standard electric car, the battery is based on lithium ion technology. These lithium ion batteries are large and heavy and their range is rarely more than 100 miles.
The recently announced innovation proposes to use a different type of battery called a lithium air cell. This battery has much more power than a lithium ion battery, and in terms of power density it is over 1,000 times higher. This means that in terms of the amount of power it delivers in proportion to its weight it is almost equivalent to petrol.
The difference between the lithium air cell and the lithium ion battery is that in the latter the positive electrode uses metal oxide, whist in the former carbon is used which is very much lighter. The carbon reacts with the surrounding air which completes the circuit and causes the electric current to flow.
Lithium air cells have been around for some time but the problem with them is that they have a very limited lifespan due to problems with charging caused by chemical instabilities, though the cause was not understood precisely until very recently. Now it has been demonstrated that the oxygen in the air reacts not only with the carbon, but also with the electrolyte, which is the medium through which the lithium ions are transported between the electrodes. This reaction depleted the electrolyte thus destroying the battery.
It was apparent that an alternative electrolyte was required, one that does not react with oxygen. In order to fine one, one of the world most powerful supercomputers was used to model possible alternatives, and it has been announced that one has been found that seems to be promising, though unsurprisingly the researchers are not revealing what it is.
A large consortium is now building a prototype which should be completed by 2013 and it is hoped to produce commercial batteries by 2020.
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