Researchers Explore Improving Li-Ion Energy Capacity and Cycle Life with Silicon Nanowires for Anode Material
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.
Candace K. Chan, Hailin Peng, Gao Liu, Kevin McIlwrath, Xiao Feng Zhang, Robert A. Huggins & Yi Cui; “High-performance lithium battery anodes using silicon nanowires” Nature Nanotechnology, Published online: 16 December 2007 | doi:10.1038/nnano.2007.411
J. P. Maranchi, A. F. Hepp, A. G. Evans, N. T. Nuhfer, and P. N. Kumta1; “Interfacial Properties of the a-Si/Cu:Active–Inactive Thin-Film Anode System for Lithium-Ion Batteries” J. Electrochem. Soc., Volume 153, Issue 6, pp. A1246-A1253 (2006)
S J Kim et. al. “Nanocomposite electrode materials for high energy density rechargeable lithium batteries” 2007 Phys. Scr., T129 57-61 doi:10.1088/0031-8949/2007/T129/013
Yoojung Kwona, Gyeong-Su Parkb and Jaephil Cho; “Synthesis and electrochemical properties of lithium-electroactive surface-stabilized silicon quantum dots” Electrochimica Acta, Volume 52, Issue 14, 1 April 2007, Pages 4663-4668
Silicon nanowire boost for rechargeable batteries (Chemistry World)