German scientists developed one of the most efficient lithium-ion batteries which can retain 85% of their capacity for more than 27 years after being used daily. This super battery also displays a high power density which should translate into a fast charging time for electric cars and a superior acceleration capabilities.
Scientists from the Center for Solar Energy and Hydrogen Research Baden-Wurttemburg (ZSW) in German developed a highly advanced type of lithium-ion batteries that retain as much as 85% of their original capacity even after being used every day for 27.4 years. This present a huge leap in battery technology and can have a dramatic effect on the electric car industry as it means that a car's battery pack should probably not need to be replaced through the entire lifespan of the car (given the price of an electric car battery pack this is great news for both car manufacturers and potential costumes).
According to the research team, the batteries already shown incredible stability lasting more than 10,000 full cycles of recharge-discharge. In terms of power density the new cells have a power density of 1,100 W/kg. This number is especially important for electric cars since it means that cars using the new battery technology will have shorter charging times (currently fully charging an electric car's battery can take many hours - depending of the car and the exact charging system - much more than any gas powered car).
source - http://thefutureofthings.com/news/11603/an-electric-car-battery-that-can-last-27-years.html