Power Polymers

Source: “Polymers with Tailored Electronic Structure for High Capacity Lithium Battery Electrodes”
Gao Liu et al.
Advanced Materials, published online September 23, 2011

Results: An electrode material that combines silicon with a new polymer developed by researchers at Lawrence Berkeley National Laboratory can store four times as much energy as conventional anodes, potentially increasing overall battery storage by 30 percent. The electrodes maintained these performance levels over 650 charging cycles.

Why it matters: Silicon electrodes have a high theoretical storage capacity, but they tend to break up after only a few charges, greatly reducing their actual capacity. Using silicon in the shape of nanowires and other nanostructures helps, but that makes it difficult to maintain electrical conductivity, and the manufacturing techniques required could prove expensive. The new polymer holds silicon particles together and maintains conductivity, and electrodes made with it could be produced on existing battery manufacturing equipment. The resulting higher-capacity batteries could improve personal electronics and extend the range of electric vehicles.

Methods: The researchers analyzed the voltage levels and other conditions that materials encounter in battery elec­trodes and worked with theoretical chemists to identify a list of conductive polymers that could withstand these conditions. They added molecules designed to tune the electrical properties of the polymer and to make it more flexible, which in turn improves its ­ability to bind particles of silicon together.

Next Steps: The researchers are collaborating with a major material-industry partner to scale up production of silicon-based electrodes that use the binders.