Tuesday, December 14, 2010

Nanotech Leads to Battery Breakthrough

    Nanotech Leads to Battery Breakthrough
  • Researchers at Rice University have made crucial progress in the creation of 3D microbatteries, which hold many advantages over traditional lithium-ion batteries and could power the next generation of electronics.
  • Researchers at Rice University have made crucial progress in the creation of 3D microbatteries, which hold many advantages over traditional lithium-ion batteries and could power the next generation of electronics.The handheld electronic devices of the future could be powered by microbatteries, tiny but powerful energy sources that hold many advantages over today's lithium-ion batteries, including significantly faster charge times. Using innovative nanotechnology techniques, researchers at Rice University have moved closer than ever in creating these batteries of the future.
    The new batteries comprise nickel-tin nanowires encased in PMMA, a polymer more commonly known as Plexiglass. In a major breakthrough, researchers in the laboratory of Rice University professor Pulickel Ajayan discovered a method of coating single nanowires in a smooth layer PMMA gel. This coating insulates the wires from interfering electrodes, but allows ions to pass through.
    "In a battery, you have two electrodes separated by a thick barrier," explained Ajayan, professor of Chemistry and Mechanical Engineering and Materials Science, according to a press release. "The challenge is to bring everything into close proximity so this electrochemistry becomes much more efficient."

    The Rice researchers innovated a way of coating nanowires in PMMA. The process could lead to the next generation of powerful batteries (source: Ajayan Lab/Rice University).
    Ajayan and his team solved this problem by fitting millions of coated nanowires onto a single chip the size of a fingernail. The scientists spent over a year refining the process. "You can't simply scale the thickness of a thin-film battery because the lithium ion kinetics would become sluggish," Ajayan said.
    "We wanted to figure out how the proposed 3D designs of batteries can be built from the nanoscale up," said Sanketh Gowda, a graduate student at Rice University. "By increasing the height of the nanowires, we can increase the amount of energy stored while keeping the lithium ion diffusion distance constant."
    "To be fair, the 3D concept has been around for a while," said postdoctoral researcher Arava Leela Mohana Reddy. "The breakthrough here is the ability to put a conformal coat of PMMA on a nanowire over long distances. Even a small break in the coating would destroy it."

    Last year, the research team successfully built coaxial nanowire cables, a breakthrough on which the new coating processes is based. In the new study, the team employed electrodeposition to build 10-micron-long nanowires within the pores of an anodized alumina template. They then used an etching technique to widen and place PMMA into the array. This process created an even coating on the nanowires from top to bottom. The researchers then used a chemical wash to dissolve the alumina template.
    The new microbattery is three-dimensional, which allows it to hold more energy and charge more quickly than a flat battery of the same size.
    "By going to 3D, we're able to deliver more energy in the same footprint," Gowda said.
    According to the research team, 3D microbatteries could power "remote sensors, display screens, smart cards, flexible electronics and biomedical devices."
    In December, the team published its results in the journal Nano Letters. Co-authors are Rice graduate student Xiaobo Zhan, former Rice postdoctoral researcher Manikoth Shaijumon and former Rice research scientist Lijie Ci.

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