New paper-like material can boost electric vehicle batteries

Researchers have developed a paper-like material that can be used to boost capacity of batteries in electric vehicles and personal electronics.
The material has the potential to boost by several times the specific energy, or amount of energy that can be delivered per unit weight of the battery.
The paper-like material, developed by researchers at the University of California, Riverside's Bourns College of Engineering, is composed of sponge-like silicon nanofibres more than 100 times thinner than human hair.
Mihri Ozkan, a professor of electrical and computer engineering, and Cengiz S Ozkan, a professor of mechanical engineering, used a technique known as electrospinning to produce the nanofibres, whereby 20,000 to 40,000 volts are applied between a rotating drum and a nozzle, which emits a solution composed mainly of tetraethyl orthosilicate (TEOS), a chemical compound frequently used in the semiconductor industry.

The nanofibres are then exposed to magnesium vapor to produce the sponge-like silicon fibre structure.
Conventionally produced lithium-ion battery anodes are made using copper foil coated with a mixture of graphite, a conductive additive, and a polymer binder.

Because the performance of graphite has been nearly tapped out, researchers are experimenting with other materials, such as silicon, which has a specific capacity, or electrical charge per unit weight of the battery, nearly 10 times higher than graphite.
The problem with silicon is that is suffers from significant volume expansion, which can quickly degrade the battery.
The silicon nanofibre structure created in the Ozkan's labs circumvents this issue and allows the battery to be cycled hundreds of times without significant degradation.

"Eliminating the need for metal current collectors and inactive polymer binders while switching to an energy dense material such as silicon will significantly boost the range capabilities of electric vehicles," said graduate student Zach Favors.
The findings were published in the journal Nature Scientific Reports.