Graphene bubbles improve lithium-air batteries

A team of scientists from the Pacific Northwest National Laboratory and Princeton  University used a new approach to buil a graphene membrane for use in lithium-air batteries, which could, one day, replace conventional batteries in electric vehicles. Resembling coral, this porous graphene material could replace the traditional smooth graphene sheets in lithium-air batteries, which become clogged with tiny particles during use.

Resembling broken eggshells, graphene structures built around bubbles produced a lithium-air battery with the highest energy capacity to date. As an added bonus, the team’s new material does not rely on platinum or other precious metals, reducing its potential cost and environmental impact.

Lithium-air batteries could allow for the creation of long-range electric vehicles, able to travel up to 300 miles between charges. Comparatively lightweight, lithium-air batteries still suffer from limited practical capacity and poor cycle life issues. However, this study showed how to maximize the capacity of the batteries.

The researchers found that the black porous structures store more than 15,000 milliamp hours per gram of graphene, making it far denser in term of energy capacity than other materials. "Many catalysts are studied now for this technology. In our process we chose not to use precious metal," said Dr. Ji-Guang Zhang, the group leader in PNNL's Li-air battery research. "This will greatly reduce production costs and increase the adoptability."

The battery is achieving the highest levels of energy capacity in an oxygen-only environment. When operated in ambient air, the capacity drops because the water in the air fouls the lithium metal in the batteries. The PNNL team is working to develop a membrane to block the water and still allow the necessary oxygen to flow

"We also want to make the battery rechargeable," said Zhang. "Right now, it is not. It is not fully rechargeable. We are working on a new electrolyte and a new catalyst so that the battery can be recharged multiple times, potentially for battery backup applications that require high energy densities."

(Adapted from PhysOrg)