USC Researchers Invent Longer-Lasting Lithium-Ion Battery

Researchers at the University of Southern California (USC) have come up with a new design for lithium-ion batteries that can hold more energy and recharge within a mere 10 minutes.

A team led by Chongwu Zhou, professor at the USC Viterbi School of Engineering, replaced the graphite anodes that are typically used in the batteries with porous silicon nanoparticles to come up with the new design, which can be used in a range of applications, from mobile devices to hybrid cars.

Zhou said, in a press release, that the research "opens the door for the design of the next-generation lithium-ion batteries." He worked with a team of graduate students as well as researcher Yunhao Lu at the Zhejiang University in China on the invention. The batteries could be available in two to three years, according to Zhou. USC's Viterbi School funded the research.

The work is certainly not the first time researchers have tried to use silicon in anodes -- the place where the current flows into a battery -- because it's inexpensive and has a high potential capacity. However, previous designs could not stand up to the charging and discharging cycles in which the anodes swell and shrink repeatedly. The small plates of silicon that were part of earlier silicon anode designs broke down after repeated use, researchers said.

The trick of the design Zhou's team came up with are porous silicon nanowires that are less than 100 nanometers in diameter and a few microns long. Small pores on the wires allow silicon to expand and contract without breaking, researchers said. They also increase the surface area of the anode, which enables lithium ions to stream in and out of the battery more quickly.

All of this results in a stronger battery in a less expensive design, researchers said. However, there were a couple of drawbacks to the design. One is that the nanowires are difficult to manufacture in large quantities. To get around this problem, researchers took small silicon spheres, which are commercially available, and gave them the same pores as the nanowires.

Another weakness in the design is that the battery's lifespan isn't as long as traditional graphite-based design -- 200 recharge cycles for the silicon nanoparticle batteries versus 500 for traditional batteries. The team will continue to research ways to change the nanoparticle element of the battery to improve this metric, Zhou said: "The easy method we use may generate real impact on battery applications in the near future."

In future research, the team also will seek a new cathode material with a high capacity to use together with the porous silicon nanowires and/or porous silicon nanoparticles to completely overhaul the battery design, researchers said.

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