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Nickel Silicide Nanobelts and Sheets in Li-ion Anodes Boost Capacity
19 April 2008
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| Electrochemical performance of the Ni silicide nanosheets (comprising Ni3Si and Ni31Si12) grown on a Ni foil substrate and of the Ni silicide nanobelts (Ni3Si) grown on a Ni foam substrate. Click to enlarge. |
Using nickel silicide nanobelts and sheets as anode materials can boost the capacity of high energy density lithium-ion batteries, according to researchers from Shenyang National Laboratory for Materials Science in China. In a paper published in Nanotechnology, Hui-Ming Cheng and his colleagues report a reversible capacity of more than 540 mAh g-1 using the nickel silicide material.
While that electrochemical capacity is lower than that provided by some silicon nanotube composites (more than 720 mAh g-1), it is significantly higher than the 350 mAh g-1 average capacity of current graphite anodes. The researchers found that the capacity can be maintained even for the 20th cycle in a standard Li+ half-cell.
The nickel material is also extremely stable. The team dismantled a cell that had experienced 20 electrochemical charge and discharge cycles and took out the working electrode for ex situ characterization. They found almost no difference in the XRD patterns between the cycled nanosheets and pristine sheets, “indicating a very good structural stability&rdquo.
In an interview with nanotechweb.org, the community website produced by IOP Publishing, the publishers of Nanotechnology, Cheng said:
Each system has its own advantages and disadvantages. Silicon has a very high theoretical capacity, which contributes a lot to the capacity of the corresponding composite material, but there are practical difficulties in implementing the system due to the large volume change of silicon during charging and discharging of the cell.
Nickel silicide nanobelts and sheets are new promising materials for lithium-ion battery applications. Because they are grown in situ on the surface of the current collector they can be employed directly as a working electrode without the need for binders and conductive additives, which will make cell manufacturing more convenient.
Nanosized silicon or silicides (as a kind of intermetallic compound that can react with lithium reversibly) are of interest as anode materials for high energy density lithium ion batteries because of their potential to attain high capacity and good cyclability at the same time. So far, the only reported nanostructured silicide materials have been nanowires.
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| Top-view SEM image of the Ni silicide nanosheets. Click to enlarge. |
The China researchers believe they are the first to demonstrate a facile and controllable synthesis of nickel (Ni) silicides in the form of nanobelts and nanosheets. They synthesized the Ni silicides nanomaterials based on the chemical reaction of Ni substrate with SiHCl3 under H2 atmosphere at 900°C. The nanobelts, 120–180 nm in thickness and 1–5 µm in width, comprise a single Ni3Si phase and the nanosheets 20–80 nm in thickness consist of Ni3Si and Ni31Si12, which is influenced by the concentration ratio of SiHCl3 to H2.
The synthesis approach is general and can be applied applicable to other transition metal silicides.
Resources
Hong-Li Zhang, Feng Li, Chang Liu and Hui-Ming Cheng; The facile synthesis of nickel silicide nanobelts and nanosheets and their application in electrochemical energy storage; 2008 Nanotechnology 19 165606 (7pp) doi:10.1088/0957-4484/19/16/165606
April 19, 2008 in Batteries, China | Permalink | Comments (2) | TrackBack (0)
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Comments
It is nice to see a Chinese researcher manage to upstage the Stanford announcement in terms of a more stable structure.
Posted by: Lulu | Apr 21, 2008 5:55:09 PM
From what I have heard, China is a lot more advanced than most people think. They are developing new technology at a fast pace and may become part of the solution soon.
Posted by: sjc | Apr 22, 2008 8:26:11 AM
