Inorganic Nanowires as Advanced Energy Conversion and Storage...
Transcript of Inorganic Nanowires as Advanced Energy Conversion and Storage...
Inorganic Nanowires as Advanced Energy Conversion and Storage Materials
Yi CuiDepartment of Materials Science and Engineering
& Geballe Laboratory for Advance MaterialsStanford University
Science 293, 1289 (2001).
In the Past: NanowiresNanoelectronic devices
Science 291, 851 (2001).
Nanowire nanosensors
100 nm
Nano Lett. 5, 1519(2005) Nature 430, 190 (2004).
Quantum coupling devices
Inorganic Nanowires
Uniqueness of nanowires- Confinement effects- Large surface area- Transport carriers, photons, and ions- Facile strain relaxation- Well-defined nanoscale domain
NanowiresDiameter 1-200 nm, Length up to 100 μm
Nanowire-Based Research Program
Electrochem Bioprobe10 nm
R Oe
Phase-change memory
Crystalline Amorphous V+_
Ag
Metal bridge memory
Nonvolatile Memory
Nano Lett. 6, 1514 (2006). J. Am. Chem. Soc. 129, 34 (2007).
Solar Cells
CIGS
Nano Lett. 7, 199 (2007). J. Am. Chem. Soc. 129, 34 (2007). Nano Lett. 7, 1095 (2007).
MEG
Li Battery
Nano Lett. 7, 490 (2007). Nature Nanotech. (submitted).
TCE
With Peter Peumans
1. Nanowire Lithium Battery ElectrodesCandace K. Chan, Yuan YangCollaborator: Prof. Robert Huggins
Nano Lett. 7, 490 (2007).
Nature Nanotech. (submitted).
GCEP 3-yr project (Mar 2007 to Feb 2010): Yi Cui, Fritz Prinz
Battery parameters:- Energy density: cathode and anode- Power density: ion intercalation and electron transport- Cycle life: strain relaxation
Li Battery Technology
J.-M. Tarascon & M. Armand. Nature. 414, 359 (2001).
Nanowires as Li Battery Electrodes
What nano can offer: - New materials otherwise not possible: (high energy density).- Large surface area and shorter distance for Li diffusion (high power density).- Good strain release and interface control: (better cycle life).- Continuous electron transport pathway.
Example: Si as Anode Materials
C anodes: the existing anode technology.
C6 LiC6
Si anodes:
Theoretical capacity: 372 mA h/g
Si Li4.4Si
Theoretical capacity: 4200 mA h/g
Problem for Si: 400% volume expansion.
Vapor-Liquid-Solid (VLS) Growth of Si Nanowires
Au particles
Metal substrate
5 μm
10 nm10 nm
SiH4
Nanowire Battery Testing
Three electrode electrochemical measurements
Nanowire electrode(working)
Li foil(reference, counter)
Measured parameters: current, voltage, time.
• Si nanowires show 10 times higher capacity than the existing carbon anodes.• Si nanowires show much better cycle life than the bulk, particle and thin film.• The significance of Si anodes: abundant, mature infrastructure, no need of high purity.
Ultrahigh Capacity Si Nanowire Anodes
At C/20 rate
GCEP 1-yr exploratory project (Jan 2007 to Dec 2007): Yi Cui
2. Nanowires for Multiexciton Generation (MEG) Solar cells
Jia Zhu, Lifeng Cui
Zhu, Cui Nano Lett. 7, 199 ,2007
MEG Processes
(Klimov, Nozik etc.)
VB
CB
Nanocrystals
Increase coupling
Catalyst: In, Bi, Ga, Pb
In
Epitaxial Growth NaCl Substrate
Zhu, Cui Nano Lett. 7, 199 ,2007
3. CuInSe2 Nanowire Materials for Solar Cells
J. Am. Chem. Soc. 129, 34 (2007). Nano Lett. 7, 199 (2007).
Hailin Peng, David Schoen, Chong Xie
CIGS: 19.5% efficiency.
ZnO, ITO2500 Å
CdS700 Å
Mo0.5-1 µm
Glass,Metal Foil,
Plastics
CIGS1-2.5 µm
CIGS
CIGS Solar Cells
Issues- Grain boundary- Nanoscale phase inhomogeneity- CIGS-CdS Interface
(R. Noufi et. al.)
Cu-Rich CuInSe2 NWs
Chalcopyrite structure
26%:23%:51%
Cu:In:Se
Cu-Defficient CuInSe2 NWs
- Still Chalcopyrite structure, but with superlattices- Vacancy ordering
Cu:In:Se 15%:34%:51%
CuInSe2 NWs CdS Chemical Bath Deposition
CuInSe2-CdS Core-Shell NWs
5 min
e
Cu ions diffuse out
CuInSe2-CdS Core-Shell NWs
EDX mapping
CISOVC
CdS
OVC: ordered vacancy compound
CuInSe2-CdS Nanotubes
Increase CBD time up to 16min at 60C
12 min
16 min
Polycrystalline
Cu-In-Cd-Se-S Nanotubes
Nanoscale Kirkendal effect:Alivisatos Science 304, 711 (2004).