cui nanowirebattery

7/29/2019 Cui NanowireBattery

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Nanowire Lithium-Ion Batteries asAdvanced Electrochemical Energy Storage

Yi CuiDepartment of Materials Science and Engineering& Geballe Laboratory for Advance MaterialsStanford University


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Importance of Energy Storage

Portable Electronics Vehicle Electrification

Tesla RoadsterStorage for Renewable Energy and Grid

Implantable Devices

Solar Wind


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Energy Storage Technologies

Capacitor Supercapacitor (Electrochemical capacitor)

++

solution

++

Metal

Metal+++++----

+

Electrical double layer

dielectrics

1

E=CV 2

2


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Batteries (Ag-Zn)

Ag ++e-...Ag

Battery voltage

-2+

Zn-2e ...Zn

+2+

2Ag

+Zn ...Ag+Zn , .G =-2FV

Reaction free energy Faraday constant


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Fuel Cells

http://en.wikipedia.org/wiki/Fuel_cell


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Comparison of Energy Storage Technologies

Specific power (w/kg)

106

105

104

103

102101

CapacitorsSacitors upercapBatteries Fuel cells

10-2 10-1 1 10 102 103

Specific energy (wh/kg)

Important parameters:

-Energy density (Energy per weight or volume)-Power density (Power per weight or volume)-Cycle life and safety-Cost


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Why Li Ion Batteries?

Li-related batteries have larger energy density than other batteries.

J.-M. Tarascon & M. Armand. Nature 414, 359 (2001).


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Existing Li Ion Battery Technology

Graphite: 370 mAh/g

LiCoO2: 140 mAh/g

The energy density can not meetthe application needs.

1.Energy density: -Anode and cathode Li storage capacity-Voltage2.Power density: -Li ion moving rate-Electron transport3. Cycle, calendar life and safety: strain relaxation and chemical stability.4. Cost: Abundant and cheap materials


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Electrode Materials

Anode: low potentialCathode: high potential

J.-M. Tarascon & M. Armand. Nature. 414, 359 (2001)


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Two Types of Electrode Materials

LiLi

Existing Tech. Future Tech.New MaterialsMechanism Intercalation Displacement/alloyVolume change Small LargeLi diffusion rate Fast SlowSpecific capacity Low High


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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)


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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.


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Example: Si as Anode Materials

C anode: the existing anode technology.LiC6

C6Theoretical capacity: 372 mA h/g

Si anode

Si

Li4.4SiTheoretical capacity: 4200 mA h/gProblem for Si: 400% volume expansion.


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Vapor-Liquid-Solid (VLS) Growth of Si Nanowires

Au nanoparticles SiH4 400-500 Cchemical vapor deposition

Metal substrateAu Nanoparticles: Si NanowiresScanning Electron Micrograph Scanning Electron Micrograph

5 m


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Structure of Si Nanowires

High Resolution Transmission Electromicrograph

10 nm10 nm-Single crystal-1-3 nm amorphous SiO2


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Nanowire Battery Testing

Beaker Cell

Flat Cell

Measured parameters: current, voltage, time.


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Ultrahigh Capacity Si Nanowire Anodes

At C/20 rate 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.C. K. Chan, R. Huggins, Y. Cui and co-workers Nature Nanotechnology 3, 31 (2008)


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Power Rate-Dependence


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Diameter Change of Si Nanowire Anodes

BeforeAfterThe diameter changes to 150% but nanowires dont break.


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Length Change of Si Nanowire Anodes

EDX mapping Before Li-cycling After Li-cycling


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Structure Change of Si Nanowire Anodes

X-ray diffraction

Li insertion


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Structure Change of Si Nanowire Anodes

Li insertion progression

HRTEM

Pristine 100 mV

50 mV 10 mV


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Acknowledgement

Candace K. ChanProf Robert Huggins


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