In 2012 electric vehicles experienced their best sales year ever in the US, however they still only sold fewer than 10,000 (less than 0.1% of new car sales).
Hybrids, such as the Toyota Prius, on the other hand have become a popular choice.
The difference is the that hybrids can recharge their batteries whilst on the move, yet EV drivers suffer from suffer range anxiety, knowing that if their battery runs out before they arrive at a recharging station, then they will be stranded.
This inability to recharge themselves means that EVs are dependent on their battery capacity, and the most popular battery used at the moment is the lithium-ion battery. Now on paper the lithium ion cell can store just more than 400 watt-hours of energy per kilogram, but in reality the figure is around half of that.
In order to remove the range anxiety and entice more people to buy EVs, battery technology must improve to offer a density of around 800 watt-hours per kilogram, at least. Lithium-ion batteries are unlikely to ever produce this performance, especially at a reasonable price.
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That means that a new battery technology must be considered, and to be a perfect source of energy it would hold the same energy per kilogram as the petroleum that it is designed to replace. Petrol has an energy density of around 13 kilowatt-hours per kg, which after all of the energy wasted in the combustion process converts to around 1.7 kW-hours per kg.
There does actually exist one battery technology that can compete, and it is even older than lithium-ion technology.
Lithium-air batteries can theoretically deliver 12 kW-hours per kg. it was first proposed in the 1970’s, yet has never met with as much success as lithium-ion cells due to the difficulty of building a lithium-air cell which can be recharged thousands of times.
The typical motorist would expect to travel around 100,000 miles before they need to replace the batteries, and that means around 3,000 charges at least. At the moment lithium-ion batteries can handle that with relative ease, lithium-air batteries cannot. But with more focus on lithium-air technology, especially now that lithium-ion cells have been receiving such negative press, then maybe a breakthrough can be made.
By. Joao Peixe of Oilprice.com
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