Scientists report major breakthrough in lithium battery technology

May 19th, 2009 - 2:49 pm ICT by ANI  

Washington, May 19 (ANI): Scientists have laid the groundwork for a lithium battery that can store and deliver more than three times the power of conventional lithium ion batteries.

Research work into this technology is being done by an NSERC (Natural Sciences and Engineering Research Council of Canada) funded lab at the University Of Waterloo, In Ontario, Canada.

The prospect of lithium-sulphur batteries has tantalized chemists for two decades, and not just because successfully combining the two chemistries delivers much higher energy densities.

Sulphur is cheaper than many other materials currently used in lithium batteries.

It has always showed great promise as the ideal partner for a safe, low cost, long lasting rechargeable battery, exactly the kind of battery needed for energy storage and transportation in a low carbon emission energy economy.

“The difficult challenge was always the cathode, the part of the battery that stores and releases electrons in the charge and recharge cycles,” said professor Linda Nazar of the University of Waterloo.

“To enable a reversible electrochemical reaction at high current rates, the electrically-active sulphur needs to remain in the most intimate contact with a conductor, such as carbon,” she added.

The Canadian research team leap-frogged the performance of other carbon-sulphur combinations by tackling the contact issue at the nanoscale level.

Although they say the same approach could be used with other materials, for their proof of concept study they chose a member of a highly structured and porous carbon family called mesoporous carbon.

At the nanoscale level, this type of carbon has a very uniform pore diameter and pore volume.

Using a nanocasting method, the team assembled a structure of 6.5 nanometre thick carbon rods separated by empty three to four nanometre wide channels.

Carbon microfibres spanning the empty channels kept the voids open and prevented collapse of the architecture.

Filling the tiny voids proved simple.

Sulphur was heated and melted. Once in contact with the carbon, it was drawn or imbibed into the channels by capillary forces, where it solidified and shrunk to form sulphur nanofibres.

Scanning electron microscope sections revealed that all the spaces were uniformly filled with sulphur, exposing an enormous surface area of the active element to carbon and driving the exceptional test results of the new battery.

“This composite material can supply up to nearly 80 percent of the theoretical capacity of sulphur, which is three times the energy density of lithium transition metal oxide cathodes, at reasonable rates with good cycling stability,” said Dr. Nazar. (ANI)

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