15 November 2011

Advances in Lithium Ion Batteries: 1 Week Power on a 15 Minute Charge

A team of engineers at Northwestern University have created an electrode that allows a lithium ion (li ion) battery to carry a charge for one week on a single 15 minute recharge.

Energy in the battery is used when the lithium ions travel from the anode, through the electrolyte, to the cathode. When they travel in the opposite direction, the battery is recharged. The duration that the battery can maintain it's charge depends on how many lithium ions can be packed into the anode or cathode. The speed at which the li ions can move from the electrolyte to the anode dictates how fast the battery can recharge.

Currently, li ion batteries are charged when electrons move from the electrolyte into the anode. Anodes are now made of graphene which allows one lithium atom to pass per six carbon atoms. Before graphene, silicon was used as the material for anodes since it allows four lithium atoms to pass per one silicon atom. Although silicon, because of this, is considered superior, it contracts and expands during charging which results in fragmentation in the battery.

What Harold H. Kung did was sandwich clusters of silicon between the graphene sheets. The research team claimed it will make more ions to stay in the anode or cathode (increasing the duration of the charge) and would eliminate or minimize the fragmentation. Using nanotechnology, they also drilled 10 to 20 nano-meter holes in the sheets to speed up the recharging process by as much as ten times. Kung, lead author of the paper, is a professor of chemical and biological engineering at the McCormick School of Engineering and Applied Science. He is also a Dorothy Ann and Clarence L. Ver Steeg Distinguished Research Fellow.

Video: How Lithium Ion batteries are made

Kung says, "We have found a way to extend a new lithium-ion battery's charge life by 10 times. Even after 150 charges, which would be one year or more of operation, the battery is still five times more effective than lithium-ion batteries on the market today."

Lithium-ion batteries are common in most electronic devices as well as in hybrid and electric cars. They are popular because of their energy density and maintain a slow loss of charge when not in use.

Last year, Scientists at the Massachusetts Institute of Technology (MIT) also discovered a process using nanotechnology and carbon nanotubes to create a powerful wave of energy. This discovery may one day lead the way to create a new environmentally friendly battery.