Loading ...
Global Do...
Technology & Engineering
Technology
207
0
Try Now
Log In
Pricing
Nanowire Lithium-Ion Batteries as Advanced Electrochemical Energy Storage Yi Cui Department of Materials Science and Engineering & Geballe Laboratory for Advance Materials Stanford University Importance of Energy Storage Portable Electronics Implantable Devices Vehicle Electrification Tesla Roadster Storage for Renewable Energy and Grid Solar Wind Energy Storage Technologies + + + + + - - - - - Capacitor + + + + + - - - - - Supercapacitor (Electrochemical capacitor) solution Metal dielectrics Electrical double layer Metal 2 2 1 CV E = Batteries (Ag-Zn) FV G Zn Ag Zn Ag Zn e Zn Ag e Ag 2 , 2 2 2 2 = + + + + + + + Reaction free energy Faraday constant Battery voltage http://en.wikipedia.org/wiki/Fuel_cell Fuel Cells Specific energy (wh/kg) Specific power (w/kg)10-2 10-1 1 10 102 103 1 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/g LiCoO2: 140 mAh/g The energy density can not meet the application needs. J.-M. Tarascon & M. Armand. Nature. 414, 359 (2001). Electrode Materials Anode: low potential Cathode: 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 m SiH4 400-500 C chemical vapor deposition Au Nanoparticles: Scanning Electron Micrograph Si Nanowires Scanning Electron Micrograph 10 nm 10 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 Anodes At 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-cycling Before Li-cycling EDX mapping Structure Change of Si Nanowire Anodes X-ray diffraction Li insertion Structure Change of Si Nanowire Anodes Li insertion progression HRTEM 100 mV 50 mV 10 mV Pristine Acknowledgement Candace K. Chan Prof Robert Huggins
