V. Focused Fundamental Research - EERE - U.S. Department of ...

V.C.12 Silicon Clathrates for Anode Applications in Lithium-Ion Batteries (SwRI)
Chan, Miller – SwRI
Current Density (mA/cm 2 )
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
2 3
1
Sample B1, Ba 8
Al 8
Si 38
Two-Electrode Split Cell
PP Separator
No Binder
200 mg Active
0.0 0.5 1.0 1.5 2.0 2.5
Applied Potential (V vs. Li|Li+)
6. Cyclic voltammetry performed on Ba 8 Al 8 Si 38
indicated extraction of Ba 2+ ions during oxidation
and Li ions were inserted into the anode during
reduction. Electrochemical characterization of
silicon clathrate anodes will be continued and
expanded to include materials synthesized by other
synthetic routes.
FY 2011 Publications/Presentations
1. 2011 DOE Annual Peer Review Meeting
Presentation.
Figure V - 124: Cyclic voltammetry of Ba8Al8Si38 for the reductive
intercalation and oxidative deintercalation of Li + after the formation of a
stable SEI.
Conclusions and Future Directions
1. Barium aluminum-silicon clathrate can be
fabricated by arc melting in small (12 gram)
quantities. First-principles computations indicated
that some of the barium guest atoms in the
aluminum-substituted Si framework can be
replaced by Li atoms. Encouraged by these
findings, part of the future efforts will be directed
toward making barium deficient aluminumsubstituted
silicon clathrates and lithium aluminumsilicon
clathrates.
2. Empty silicon clathrates can be synthesized by
plasma-enhanced magnetron sputtering of silicon
into an ionic liquid. Future work will be directed
toward refining the technique to improve the yield
of this process.
3. High-pressure, high-temperature synthesis has
produced about 100 mg of Ba 8 Si 46. This batch of
material will be made into half-cells for
electrochemical evaluation.
4. Ionic liquids with suitable thermal stability for soft
oxidation of BaSi 2 at 300ºC to 400ºC have been
identified and incorporated into a reactor set-up.
Synthesis of guest-free silicon clathrates via soft
oxidation has been initiated. This effort will be
continued to evaluate several reaction schemes
based on the Hoffman elimination reaction.
5. First-principles computational results showed that
the stabilization energy of the Si framework (cage
structure) by Li is smaller than that of Ba, meaning
that Li can be inserted and extracted more easily
from the Si framework than Ba. Future work will
directed toward predicting the kinetic barriers for
various lithiation pathways.
Energy Storage R &D 584 FY 2011 Annual Progress Report