Researchers Use Silicon Anodes to Improve EV Batteries

A team of graduate engineering students from the University of Waterloo in Ontario, Canada, says it has developed a silicon-based anode that can increase the energy density of lithium-ion batteries by 40%-60%. The improvement will enable battery-powered electric vehicles to travel more than 310 miles before needing to be recharged, according to the team.  

Current lithium-ion batteries use graphite anodes. But the limited amount of energy the material can store represents a performance bottleneck, the researchers note.

Silicon anode materials have a much higher lithium capacity that can yield nearly a tenfold increase in battery energy. However, much of the energy is lost when silicon contracts and expands—by as much as 300%—with each charge cycle. Such changes in volume produce cracks that reduce battery performance, create short circuits and eventually can cause a battery to stop operating.

To overcome the problem, the Waterloo team worked with General Motors Co. to develop a flash heat treatment for fabricated silicon-based lithium-ion electrodes. The new anode design involves wrapping silicon nanoparticles with doped graphene, then shielding the composite with cyclized polyacrylonitrile.

Developers say the new process minimizes volume expansion and enables the use of uniquely structured silicon anodes that boost the performance and cycle capability (to more than 2,000) of lithium-ion batteries.

The Waterloo team is led by Zhongwei Chen,  a chemical engineering professor and member of the university’s nanotechnology and sustainable energy institutes. Chen hopes to commercialize the technology by the end of 2016.

The program is detailed in the latest issue of the science journal Nature Communications. In addition to GM, the research was supported by the Natural Sciences and Engineering Research Council of Canada and the U.S. Dept. of Energy.