"Foam is relatively easy to manufacture," says Prieto. It also has a 3D structure that increases the surface area of the electrodes and brings them closer together, which in turn increases the power density of the battery. In terms of energy density, the foam should also get more bang for the buck. The intricate 3D structures utilize the electrode material more efficiently than a flat surface.
On top of the copper foam, the researchers electroplate the anode, made from a material called copper antimonide. In a kind of bootstrap battery building, the anode then serves as an electrode for an electrochemical polymerization reaction that deposits the battery's solid electrolyte. Finally, the team fills the space within the foam with a slurry that is dried to form the cathode. An aluminum mesh structure collects the current on the cathode side.
The electroplating equipment the team uses is inexpensive compared to the equipment needed to make other types of batteries. Prieto estimates the cost to manufacture the copper foam batteries will be about half that of conventional lithium ion batteries made in China. The team also calculates that the foam battery should store the same amount of energy as conventional batteries in two-thirds the volume, charge five to ten times faster, and last up to ten times longer.
The research team's new battery also promises a number of safety and environmental benefits. The solid electrolyte the team chose reduces the risk of fire posed by conventional liquid electrolytes. In addition, the team relied only on water-based, non-toxic chemistry to manufacture the battery. "This was my personal dream," says Prieto. "I didn't think it would actually work, but it now looks like it will."
Throughout the design process the team had to develop new ways to make known materials, such as th
|Contact: Catherine Meyers|
American Institute of Physics