Batteries Built Like Pomegranates Hold More Juice

The Citizen's Guide to the Future
Feb. 18 2014 11:31 AM

Batteries Built Like Pomegranates Hold More Juice

pom1
Researchers at Stanford designed an electrode like a pomegranate to improve the performance of common lithium-ion batteries made with silicon.

Illustration by Greg Stewart/SLAC.

If your cellphone battery has ever died at the wrong moment, you know that battery technology is still evolving. Slowly. And one problem has been successfully integrating different materials, like silicon, to capitalize on their favorable properties.

Silicon anodes (the negative electrode in a battery) have the potential to store about 10 times more charge than the graphite ones currently used in lithium-ion batteries, but silicon gets brittle and breaks easily. It also reacts with some of the chemicals creating charge in batteries to produce a gunk that eventually makes everything break down.

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But researchers at Stanford and the Department of Energy's SLAC National Accelerator Lab are getting around some of these problems by designing their batteries like a pomegranate. Which just sounds delicious. The engineers create an electrode in which silicon nanoparticles are formed like seeds within carbon membranes. When charged, the seeds can swell within the membrane (like a pomegranate seed surrounded by juice). This creates less chance of breakage and also minimizes the silicon's exposure to other battery chemicals, thus reducing gunk.

“Experiments showed our pomegranate-inspired anode operates at 97 percent capacity even after 1,000 cycles of charging and discharging, which puts it well within the desired range for commercial operation,"  Yi Cui, an associate professor at Stanford and SLAC who led the research, said in a press release.

The process will need to be simpler and materials will need to be cheaper before this method can be viable for commercial use, but the design is a big step. Maybe pineapple light bulbs are next.

pom2
Silicon nanoparticles in membranes clustered like pomegranate seeds before and after charging.

Figure by Nian Liu, Zhenda Lu and Yi Cui/Stanford.

Future Tense is a partnership of SlateNew America, and Arizona State University.

Lily Hay Newman is lead blogger for Future Tense.

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