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Researchers Explore Improving Li-Ion Energy Capacity and Cycle Life with Silicon Nanowires for Anode Material

17 December 2007

Silicon is conceptually an attractive anode material for lithium-ion batteries because of its high theoretical charge capacity (4,200 mAh g-1—more than 10 times that of graphite anodes and much larger than various nitride and oxide materials) and low discharge potential. However, silicon anodes are problematic because the material’s volume changes by up to 400% upon the insertion and extraction of lithium ions during charge/discharge cycles. This results in pulverization and capacity fading.

Researchers at Stanford University are trying to circumvent this problem by using silicon nanowires as the anode material. In a letter published online in Nature Nanomaterials, the team reports achieving the theoretical charge capacity for silicon anodes and maintaining a discharge capacity of 75% of the maximum, with little fading under 10 charge/discharge cycles.

There have been many different approaches taken for developing a silicon-based anode material. A few include:

  • Amorphous silicon thin films deposited on copper foil have exhibited the near theoretical capacity for a limited number of cycles. The films, however, eventually delaminate, leading to failure of the anode.

  • Multi-walled carbon nanotube (MWNT)/silicon composites. The highest Crev of the composite anode was measured to be 1,770 mAh/g.

  • Silicon quantum dots (n-Si), coated with an amorphous carbon layer. The n-Si that annealed at 900 °C possessed a first charge capacity of 1,257 mAh/g with an coulombic efficiency of 71%.

The Stanford work represents some of the best results to date, although the cycle testing has been very limited.

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December 17, 2007 in Batteries | Permalink | Comments (3) | TrackBack (0)

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Comments

While noted in the text, the title is a bit misleading. 10 cycles to 75% capacity isn't exactly a revolution in cycle life, even for Silicon.

Stanford's website news service for this
(http://news-service.stanford.edu/news/2008/january9/nanowire-010908.html)

touts that the charge density of batteries that would be developed may be as high as ten times carbon anode Li-ion batteries.

dear,
i am a Bangladeshi and my research work was on physical chemistry (electrochemistry studies of speciation
and complexation of cadmium(ii) in ppb level with ethylene diamine and natural ligand in aqueous media. i need a chance to develops my knowledge. please, i would like to be grateful if u consider me to admit your institution.
Thankyou
Sincerely yours
Anshaya ramim

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