New article: Researchers made safer batteries with wood read more at here http://www.spinonews.com/index.php/science/item/3119-researchers-made-safer-batteries-with-wood

Engineers at the University of Maryland have used modified wood as a unique architecture for the negative electrode of a lithium (Li) metal battery, seeking to prevent some of the key factors that lead to battery failure.

In this new type of battery, instead of storing Li ions in a metal block, engineers store Li metal in the natural channels of wood, channels that were once used to carry water and nutrients.

The wood acts as a "hotel" to provide lots of rooms (channels) to accommodate many guests (Li metal). As the Li metal "guests" enter this wood hotel, it can accommodate them all, storing them comfortably and securely in each room while maintaining the wood's rigid exterior structure. The number of Li metal (guests) can increase and decrease within each room, but the overall structure will not be damaged or collapse.

The current density of a battery is a metric engineer use to describe how quickly the Li metal is deposited at the surface, a high current density is equivalent to having excessive guests flow into/out of the wood "hotel," which can cause issues when pile-ups occur at the door. 

These pile-ups can be avoided by simply increasing the number of doors available to the Li ions as they enter the wood "hotel," which is the approach used in this research. 

By using the large surface area provided by the walls of each channel in the wood host, the local current density can be minimized, facilitating the controlled movement of Li metal.

Batteries that use bulk Li metal foil, which is the conventional alternative, are like an unstable hotel with only one door for guests to go in and out. When the battery is put to the test under high current density conditions, its single door cannot manage the large flow of guests, so it can be easily cracked, leading to hazards within the battery.

On the other hand, the wood "hotel" design, with its many straight channels, provides plenty of doors for guests so the Li metal can be corralled into individual channels, behaving in an orderly, predictable manner even under high current density (3 mA/cm2) and avoiding branch-like structures of Li that can cause battery failure.

 

Liangbing Hu, an Associate Professor in the Department of Materials Science, said, this is part of our ongoing research to use natural materials to improve batteries. Using nature's bio-structure, we can find inspiration to create new ways of storing energy, and we can use renewable materials, too.

More information: [PNAS]