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Nanowire Lithium-Ion Batteries asAdvanced Electrochemical Energy StorageYi CuiDepartment of Materials Science and Engineering& Geballe Laboratory for Advance MaterialsStanford University
Importance of Energy StoragePortable ElectronicsVehicle ElectrificationTesla RoadsterImplantable DevicesStorage for Renewable Energy and GridSolarWind
Energy Storage TechnologiesCapacitor Metal -Supercapacitor (Electrochemical capacitor)Metal - solution-Electrical double layerdielectrics1E CV 22
Batteries (Ag-Zn)Ag e Ag Zn 2e Zn2 Battery voltage2 Ag Zn Ag Zn 2 , ΔG 2 FVReaction free energyFaraday constant
Fuel Cellshttp://en.wikipedia.org/wiki/Fuel cell
Specific power (w/kg)Comparison of Energy Storage 02Batteries Fuel cells10110-210-1110102103Specific energy (wh/kg)Important parameters:- Energy density (Energy per weight or volume)- Power density (Power per weight or volume)- Cycle life and safety- Cost
Why Li Ion Batteries?Li-related batteries have larger energy density than other batteries.J.-M. Tarascon & M. Armand. Nature 414, 359 (2001).
Existing Li Ion Battery TechnologyGraphite: 370 mAh/gLiCoO2: 140 mAh/gThe energy density can not meetthe application needs.1.2.3.4.Energy density: - Anode and cathode Li storage capacity- VoltagePower density: - Li ion moving rate- Electron transportCycle, calendar life and safety: strain relaxation and chemical stability.Cost: Abundant and cheap materials
Electrode MaterialsAnode: low potentialCathode: high potentialJ.-M. Tarascon & M. Armand. Nature. 414, 359 (2001).
Two Types of Electrode MaterialsLiLiExisting Tech.Future Tech.New olume changeSmallLargeLi diffusion rateFastSlowSpecific capacityLowHigh
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 ElectrodesWhat 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 MaterialsC anode: the existing anode technology.C6LiC6Theoretical capacity: 372 mA h/gSi anodeSiLi4.4SiTheoretical capacity: 4200 mA h/gProblem for Si: 400% volume expansion.
Vapor-Liquid-Solid (VLS) Growth of Si NanowiresAu nanoparticlesSiH4 400-500 ºCchemical vapor depositionMetal substrateAu Nanoparticles:Scanning Electron MicrographSi NanowiresScanning Electron Micrograph5 μm
Structure of Si NanowiresHigh Resolution Transmission Electromicrograph10 nm10 nm- Single crystal- 1-3 nm amorphous SiO2
Nanowire Battery TestingBeaker CellFlat CellMeasured parameters: current, voltage, time.
Ultrahigh Capacity Si Nanowire AnodesAt 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)
Power Rate-Dependence
Diameter Change of Si Nanowire AnodesBeforeAfterThe diameter changes to 150% but nanowires don’t break.
Length Change of Si Nanowire AnodesEDX mapping Before Li-cyclingAfter Li-cycling
Structure Change of Si Nanowire AnodesX-ray diffractionLi insertion
Structure Change of Si Nanowire AnodesHRTEMPristineLi insertion progression100 mV50 mV10 mV
AcknowledgementCandace K. ChanProf Robert Huggins
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). . Microsoft PowerPoint - Cui-Nanowire Battery Author: Yi Cui Office Created Date:
