DETROIT (AP) -- General Motors said Thursday that it has licensed technology from a government laboratory that promises to improve battery performance in its Volt electric car by 50 percent to 100 percent.

GM and LG Chem have agreed to license the technology, which consists of a mix of materials, from the Argonne National Laboratory. LG Chem, based in Seoul, South Korea, makes the Volt battery.

GM, based in Detroit, says several years of development and testing will be required before the new material is ready to be used.

The Volt went on sale late last year. Right now, only a handful of cars are available in a few cities around the country. The Volt's battery can be charged by plugging it into an electrical socket. The car is powered by electricity for up to 40 miles before a gasoline-powered motor kicks in.

Batteries for electric cars like the Volt and the new all-electric Nissan Leaf are heavy and expensive. The Volt's battery is estimated to cost $8,000 and the larger Leaf battery is estimated to cost $12,000. The cars sell for about $40,000 and $33,000, respectively. The federal government offers buyers a $7,500 tax credit per car to help promote sales.

The high cost and limited range of electric cars have slowed their development and adoption. Automakers, battery makers, and research institutions have been working for decades to make batteries cheaper, lighter, more durable and able to hold more energy.

Gasoline stores fifty times more energy per pound than the best lithium ion batteries.

Argonne says it has improved the part of the battery called the cathode, which is responsible for storing the charge. The lab created a mix of lithium and manganese-rich metal oxides that it says increases durability and safety and will allow the cathode to hold as much as double the energy as conventional cathodes.

Argonne, based in Argonne, Ill, is a U.S. Department of Energy lab.