Lithium-air [LiO2] batteries have a theoretical energy density of some 3,460Wh/kg but in practice hasn’t been able to surpass that of a sodium-air battery at 1,600Wh/kg.
Development of the next-generation rechargeable battery is going to directly impact the performance and capabilities of electric vehicles. Current lithium-ion [Li-ion] battery technology has a maximum density of 250Wh/kg, while a 116Wh/kg Li-ion battery powers the Tesla Model S.
The 85kWh version gives the Model S a range of up to 300 miles. Imagine if LiO2 game-changing battery technology really could provide 3,460Wh/kg, which could theoretically increase the range of a Model S, with the same weight battery, nearly 9,000mi on a single charge. Current sodium-air battery technology could net a more modest 4,000mi.
Let’s get back to reality though, and we’ll note that sodium-air battery technology needs a lot of development. A sodium-air battery today may be able to increase an electric vehicle’s range 1,300%, reduce the battery weight to less than a tenth of its original weight, or some combination of the two.
Sodium-air battery technology is also much cheaper to produce than lithium-based batteries. Such a development could effectively eliminate all the concerns about electric vehicle recharging and range, but it could only do it eight times before the battery stops holding a charge. Research continues in battery construction and formulation as well as charge and discharge management.
For the record, current Tesla Model S batteries have a 240 Wh/kg capacity. They are also predicting 400 Wh/kg in their vehicles by 2015. These Sodium-Air batteries are a great prospect but even the Tesla Roadster’s original battery packs have generally maintained greater than 80% capacity after 100,000 miles of driving, so cycle life will have to be improved dramatically for them to be worthwhile.