Ph.D defense Candace K. Chan, Monday June 8 @ 2pm, Braun Lec

Candace Chan candacec at
Fri Jun 5 08:36:37 PDT 2009

Reminder - Ph.D defense on Monday
> *One-dimensional nanostructured materials for Li-ion battery and 
> supercapacitor electrodes*
> Candace K. Chan (Dept. of Chemistry)
> Adviser: Yi Cui (Dept. of Materials Science & Engineering)
> Monday, June 8 @ 2 pm (Refreshments served at 1:45 pm)
> Braun Lecture Hall (Mudd Chemistry Building)
> Abstract 
> The need for improved electrochemical storage devices has necessitated 
> research on new and advanced electrode materials. One-dimensional 
> nanomaterials such as nanowires, nanotubes, and nanoribbons, can 
> provide a unique opportunity to engineer electrochemical devices to 
> have improved electronic and ionic conductivity as well as 
> electrochemical and structural transformations. Several properties of 
> nanomaterials, including 1) facile strain relaxation and phase 
> transformation, 2) good ionic diffusion, and 3) good electronic 
> conduction are important characteristics that allow for improvements 
> in performance over bulk materials. Several examples of how 
> nanomaterials are being used to improve problems in energy storage 
> will be given, with discussion on fundamental and applied studies at 
> the single nanowire and ensemble level all the way up to the 
> nanocomposite level.
> A study on the phase transformations in V2O5 nanoribbons during 
> reaction with lithium will be presented, with implications for Li-ion 
> cathodes. Transformation of the V2O5 nanoribbons into the fully 
> lithiated ?-Li3V2O5 phase was found to depend not only on the width 
> but also the thickness of the nanoribbons. For the first time, 
> complete delithiation of ?-Li3V2O5 back to the single-crystalline, 
> pristine V2O5 nanoribbon was observed, indicating a 30% higher energy 
> density.
> For Li-ion battery anodes, the use of Si and Ge nanowires (NWs) as 
> high capacity replacements for graphite will be discussed. By using a 
> SiNW electrode, a 10X higher specific capacity was achieved. Problems 
> plaguing bulk Si, such as pulverization and poor charge storage 
> retention, were not observed in the SiNWs due to the NWs having 
> improved accommodation of strain and volume expansion.
> Finally, an entirely printable supercapacitor device will be presented 
> based on high surface area carbons and a flexible, printable silver 
> nanowire-based current collector. These devices demonstrate how 
> nanomaterials can be integrated into a roll-to-roll manufacturing 
> process while still displaying good performance.
> -- 
> Candace K. Chan
> Ph.D. Student, Department of Chemistry
> Stanford University
> McCullough Building Room 209
> 476 Lomita Mall
> Stanford, CA 94305

Candace K. Chan
Ph.D. Student, Department of Chemistry
Stanford University
McCullough Building Room 209
476 Lomita Mall
Stanford, CA 94305

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