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Complete magnesiothermic reduction reaction of vertically aligned mesoporous silica channels to form pure silicon nanoparticles.

Kim KH, Lee DJ, Cho KM, Kim SJ, Park JK, Jung HT - Sci Rep (2015)

Bottom Line: The procedure involves magnesium promoted reduction of vertically oriented mesoporous silica channels on reduced graphene oxides (rGO) sheets.The mesopores play a significant role in effectively enabling magnesium gas to interact with silica through a large number of reaction sites.The new method for complete magnesiothermic reduction of mesoporous silica approach provides a foundation for the rational design of silicon structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering (BK21+Program), Korea Advance Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea).

ABSTRACT
Owing to its simplicity and low temperature conditions, magnesiothermic reduction of silica is one of the most powerful methods for producing silicon nanostructures. However, incomplete reduction takes place in this process leaving unconverted silica under the silicon layer. This phenomenon limits the use of this method for the rational design of silicon structures. In this effort, a technique that enables complete magnesiothermic reduction of silica to form silicon has been developed. The procedure involves magnesium promoted reduction of vertically oriented mesoporous silica channels on reduced graphene oxides (rGO) sheets. The mesopores play a significant role in effectively enabling magnesium gas to interact with silica through a large number of reaction sites. Utilizing this approach, highly uniform, ca. 10 nm sized silicon nanoparticles are generated without contamination by unreacted silica. The new method for complete magnesiothermic reduction of mesoporous silica approach provides a foundation for the rational design of silicon structures.

No MeSH data available.


Electrochemical characteristics.(a) The cycling performances and coulombic efficiencies of unit cells fabricated using completely reduced silicon nanoparticles (red dot) and commercial silicon nanoparticles (black square) at 2 A/g, (b) rate capability of completely reduced silicon nanoparticle electrode measured at a series of current rates.
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f6: Electrochemical characteristics.(a) The cycling performances and coulombic efficiencies of unit cells fabricated using completely reduced silicon nanoparticles (red dot) and commercial silicon nanoparticles (black square) at 2 A/g, (b) rate capability of completely reduced silicon nanoparticle electrode measured at a series of current rates.

Mentions: To demonstrate the applicability of the ca. 10 nm scale silicon nanoparticles on rGO sheets produced by using the new approach, we explored their use as an anode for Li ion batteries in the coin-type half-cells. We anticipated that the silicon nanoparticles on the rGO sheets would enable Li+ ion access and electron transfer, and would accommodate the severe volume changes taking place during battery operation2930. For comparison purposes, two silicon anodes were generated, one containing commercially available silicon particles (Alfar Aesar, average particle size ≤50 nm) and the other completely reduced silicon nanoparticles. The cycling performances and coulombic efficiencies of half-cells containing both anodes were evaluated (Figures 6a and see Supplementary Fig. S6 online). The results show that the capacity of commercial silicon nanoparticle anode drops rapidly over time and reaches a value of 715 mAh/g after 100 cycles, with an initial capacity retention of 43.7%. The relatively poor cycling performance of this anode is attributed to the dramatic changes in volume of silicon particles occurring during Li ion insertion and the extraction process, which leads pulverization of the electrode materials and breakdown of the electrically conductive network. In contrast, the capacity of the anode fabricated using completely reduced silicon nanoparticles increases in the initial 24 cycles and retains 100% capacity until 40 cycles. Moreover, this anode retains 82.8% (956.7 mAh/g) of its capacity following 100 cycles. It should be noted that this level of capacity retention is achieved without the need to employ an additional carbon coating process. The superior cycling performance of the anode comprised of completely reduced silicon nanoparticles can be attributed to the small particle size (ca. 10 nm), which enables the anode to endure volume changes during the operation.


Complete magnesiothermic reduction reaction of vertically aligned mesoporous silica channels to form pure silicon nanoparticles.

Kim KH, Lee DJ, Cho KM, Kim SJ, Park JK, Jung HT - Sci Rep (2015)

Electrochemical characteristics.(a) The cycling performances and coulombic efficiencies of unit cells fabricated using completely reduced silicon nanoparticles (red dot) and commercial silicon nanoparticles (black square) at 2 A/g, (b) rate capability of completely reduced silicon nanoparticle electrode measured at a series of current rates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4355679&req=5

f6: Electrochemical characteristics.(a) The cycling performances and coulombic efficiencies of unit cells fabricated using completely reduced silicon nanoparticles (red dot) and commercial silicon nanoparticles (black square) at 2 A/g, (b) rate capability of completely reduced silicon nanoparticle electrode measured at a series of current rates.
Mentions: To demonstrate the applicability of the ca. 10 nm scale silicon nanoparticles on rGO sheets produced by using the new approach, we explored their use as an anode for Li ion batteries in the coin-type half-cells. We anticipated that the silicon nanoparticles on the rGO sheets would enable Li+ ion access and electron transfer, and would accommodate the severe volume changes taking place during battery operation2930. For comparison purposes, two silicon anodes were generated, one containing commercially available silicon particles (Alfar Aesar, average particle size ≤50 nm) and the other completely reduced silicon nanoparticles. The cycling performances and coulombic efficiencies of half-cells containing both anodes were evaluated (Figures 6a and see Supplementary Fig. S6 online). The results show that the capacity of commercial silicon nanoparticle anode drops rapidly over time and reaches a value of 715 mAh/g after 100 cycles, with an initial capacity retention of 43.7%. The relatively poor cycling performance of this anode is attributed to the dramatic changes in volume of silicon particles occurring during Li ion insertion and the extraction process, which leads pulverization of the electrode materials and breakdown of the electrically conductive network. In contrast, the capacity of the anode fabricated using completely reduced silicon nanoparticles increases in the initial 24 cycles and retains 100% capacity until 40 cycles. Moreover, this anode retains 82.8% (956.7 mAh/g) of its capacity following 100 cycles. It should be noted that this level of capacity retention is achieved without the need to employ an additional carbon coating process. The superior cycling performance of the anode comprised of completely reduced silicon nanoparticles can be attributed to the small particle size (ca. 10 nm), which enables the anode to endure volume changes during the operation.

Bottom Line: The procedure involves magnesium promoted reduction of vertically oriented mesoporous silica channels on reduced graphene oxides (rGO) sheets.The mesopores play a significant role in effectively enabling magnesium gas to interact with silica through a large number of reaction sites.The new method for complete magnesiothermic reduction of mesoporous silica approach provides a foundation for the rational design of silicon structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering (BK21+Program), Korea Advance Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea).

ABSTRACT
Owing to its simplicity and low temperature conditions, magnesiothermic reduction of silica is one of the most powerful methods for producing silicon nanostructures. However, incomplete reduction takes place in this process leaving unconverted silica under the silicon layer. This phenomenon limits the use of this method for the rational design of silicon structures. In this effort, a technique that enables complete magnesiothermic reduction of silica to form silicon has been developed. The procedure involves magnesium promoted reduction of vertically oriented mesoporous silica channels on reduced graphene oxides (rGO) sheets. The mesopores play a significant role in effectively enabling magnesium gas to interact with silica through a large number of reaction sites. Utilizing this approach, highly uniform, ca. 10 nm sized silicon nanoparticles are generated without contamination by unreacted silica. The new method for complete magnesiothermic reduction of mesoporous silica approach provides a foundation for the rational design of silicon structures.

No MeSH data available.