Nanowire Lithium-Ion Batteries as Advanced Electrochemical Energy
Transcript of Nanowire Lithium-Ion Batteries as Advanced Electrochemical Energy
Nanowire Lithium-Ion Batteries as Advanced Electrochemical Energy Storage
Yi CuiDepartment of Materials Science and Engineering
& Geballe Laboratory for Advance MaterialsStanford University
Importance of Energy Storage
Portable Electronics
Implantable Devices
Vehicle Electrification
Tesla Roadster
Storage for Renewable Energy and Grid
Solar Wind
Energy Storage Technologies
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Capacitor
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Supercapacitor (Electrochemical capacitor)
solution
Metal
dielectricsElectrical double layer
Metal
2
21 CVE =
Batteries (Ag-Zn)
FVGZnAgZnAgZneZnAgeAg
2,22
2
2
−=Δ+⎯→⎯+
⎯→⎯−
⎯→⎯+
++
+−
−+
Reaction free energy Faraday constant
Battery voltage
http://en.wikipedia.org/wiki/Fuel_cell
Fuel Cells
Specific energy (wh/kg)
Spec
ific
pow
er (w
/kg)
10-2 10-1 1 10 102 1031
10
102
103
104
105
106 Capacitors
Supercapacitors
Batteries Fuel cells
Comparison of Energy Storage Technologies
Important parameters:- Energy density (Energy per weight or volume)- Power density (Power per weight or volume)- Cycle life and safety- Cost
J.-M. Tarascon & M. Armand. Nature 414, 359 (2001).
Why Li Ion Batteries?
Li-related batteries have larger energy density than other batteries.
Existing Li Ion Battery Technology
1. Energy density: - Anode and cathode Li storage capacity- Voltage
2. Power density: - Li ion moving rate- Electron transport
3. Cycle, calendar life and safety: strain relaxation and chemical stability.4. Cost: Abundant and cheap materials
Graphite: 370 mAh/gLiCoO2: 140 mAh/g
The energy density can not meetthe application needs.
J.-M. Tarascon & M. Armand. Nature. 414, 359 (2001).
Electrode Materials
Anode: low potentialCathode: high potential
Two Types of Electrode Materials
Existing Tech. Future Tech.New Materials
Mechanism Intercalation Displacement/alloy
Volume change Small Large
Li diffusion rate Fast Slow
Specific capacity Low High
Li Li
We work on the future generation of battery materials.
C. K. Chan, Y. Cui and co-workers, Nano Letters 7, 490 (2007).C. K. Chan, Y. Cui and co-workers, Nano Letters 8, 307 (2007)C. K. Chan, R. Huggins, Y. Cui and co-workers Nature Nanotechnology 3, 31 (2008)
Nanowires as Li Battery Electrodes
What nanowires can offer: - Good strain relaxation: new materials possible- Large surface area and shorter distance for Li diffusion- Interface control: (better cycle life).- Continuous electron transport pathway.
Example: Si as Anode Materials
C anode: the existing anode technology.
C6 LiC6
Si anode
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 nanoparticles
Metal substrate
5 μm
SiH4 400-500 ºCchemical vapor deposition
Au Nanoparticles:Scanning Electron Micrograph
Si NanowiresScanning Electron Micrograph
10 nm10 nm
Structure of Si Nanowires
High Resolution Transmission Electromicrograph
- Single crystal- 1-3 nm amorphous SiO2
Nanowire Battery Testing
Measured parameters: current, voltage, time.
Beaker Cell Flat Cell
• 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.
Ultrahigh Capacity Si Nanowire AnodesAt C/20 rate
C. K. Chan, R. Huggins, Y. Cui and co-workers Nature Nanotechnology 3, 31 (2008)
Power Rate-Dependence
Diameter Change of Si Nanowire Anodes
Before
After
The diameter changes to 150% but nanowires don’t break.
Length Change of Si Nanowire Anodes
After Li-cyclingBefore Li-cyclingEDX mapping
Structure Change of Si Nanowire Anodes
X-ray diffraction
Li insertion
Structure Change of Si Nanowire Anodes
Li insertion progressionHRTEM100 mV 50 mV 10 mVPristine
Acknowledgement
Candace K. ChanProf Robert Huggins