Monday, January 24, 2011

New Nanomaterial For Batteries

A nanomaterial has been developed at Rensselaer Polytechnic Institute for a new breed of high-power rechargeable lithium (Li)-ion batteries for electric automobiles, laptop computers, mobile phones, and other portable devices. The new batteries can withstand extremely high rates of charge and discharge which will cause electrodes used in conventional Li-ion batteries to rapidly deteriorate and fail. The greatest advantage of the new batteries is that charging laptop or cell phone in a few minutes, rather than an hour.
The new batteries are made from a carbon (C) nanorod base topped with a thin layer of nanoscale aluminum (Al) and a "scoop" of nanoscale silicon (Si), the structures are flexible and able to quickly accept and discharge Li ions at extremely fast rates without sustaining significant damage. The segmented structure of the nanoscoop allows the strain to be gradually transferred from the C base to the Al layer, and finally to the Si scoop. This natural strain gradation provides for a less abrupt transition in stress across the material interfaces, leading to improved structural integrity of the electrode.
Charging cycle
The anode structure of a Li-ion battery physically grows and shrinks as the battery charges or discharges. When charging, the addition of Li ions increases the volume of the anode, while discharging has the opposite effect. These volume changes result in a buildup of stress in the anode. Too great a stress that builds up too quickly, as in the case of a battery charging or discharging at high speeds, can cause the battery to fail prematurely. This is why most batteries in today's portable electronic devices like cell phones and laptops charge very slowly, the slow charge rate is intentional and designed to protect the battery from stress-induced damage. Due to their nanoscale size, our nanoscoops can soak and release Li at high rates far more effectively than the macroscale anodes used in today's Li-ion batteries,
A limitation of the nanoscoop architecture is the relatively low total mass of the electrode, according to the researchers and to solve this, the researchers are to trying to grow longer scoops with greater mass, or develop a method for stacking layers of nanoscoops on top of each other or to grow the nanoscoops on large flexible substrates that can be rolled or shaped to fit along the contours or chassis or chassis of the device.

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