|Nanoneedles. Source: WSU. Click to enlarge.|
Researchers at Washington State University (WSU), led by Dr. Grant Norton, professor in the School of Mechanical and Materials Engineering, are developing a nanoneedle tin (Sn) anode material for Li-ion batteries. Elemental Sn is attractive as a high-performance anode material because of its high theoretical specific capacity (992 mAh g-1) and high operating voltage along with the absence of solvent intercalation.
However, similar to silicon, tin experiences huge volumetric expansion/shrinkage on cycling, causing severe mechanical disintegration (such as cracking and pulverization) and hence shortened cycle life. A number of research groups are working on methods to prevent such life-limiting mechanical problems, such as the use of tin nanopillars layered between graphene sheets. (Earlier post.)
Norton and postdoctoral researcher Uttara Sahaym developed their novel nanoneedle material a little over a year ago while working on a project to mitigate tin whiskers—a problem in microelectronics because of short-circuiting.
Norton and his group decided to see if they could control the growth of tin whiskers, instead of trying to get rid of them. They applied the work to developing a tin-based anode for batteries.
The researchers developed a method for growing tin nanoneedles directly onto copper foil using a standard electroplating process that is commonly used in industry.
With support from the WSU College of Engineering and Architecture’s Emerging Technology Fund, which is funded by private donations, the researchers have started building and testing the batteries.
According to Dr. Norton, capacity and performance information for the new material is not yet publicly available. For its battery development work, the team is currently using Li for the cathode and LiPF6 for the electrolyte. Norton adds that while it is unlikely that this will be the final device pairing, it is what the team is using for cell testing.