1. Cynthia Yu
Griffin Godbey, Chen Gong, Clayton Blythe, and Dr. Marina S. Leite
Department of Materials Science and Engineering, Univ. of Maryland, College Park, MD
Institute for Research in Electronics and Applied Physics, Univ. of Maryland, College Park, MD
Summer REU 2015: Transportation Electrification
cyu601@gmail.com100 µm
2. Advantages:
• Lightweight
• Promising battery
chemistry
• Low maintenance
• Environmental
friendly
• High energy
density per weight
Consumer Electronics Electric Transportation
HEV/Electric Vehicles Solar Charging
2Summer REU 2015: Transportation Electrification Cynthia Yu
Lithium-Ion Batteries
Li-ion
battery
3. • Poor life cycle
• Rising internal
resistance with
cycling and age
• Safety
concerns if
overheated or
overcharged
3
Summer REU 2015: Transportation Electrification Cynthia Yu 3
Current Limitations of Lithium-Ion Batteries
Result of
Liquid electrolyte
leakage!
4. Conventional Battery
25 µm
Liquid electrolyte
4
4
Anode
Cathode
SolidElectrolyte
Anode
Cathode
Solid electrolyte < 1µm
3D structure:
Self-rolled tube
Solid Electrolyte
Thin-film process
Solid Electrolyte
Large surface area and
small volume
footprint!
All-solid state battery
Solid Electrolyte
Summer REU 2015: Transportation Electrification Cynthia Yu
A 3D Architecture Approach
Advanced Functional
Materials,18(7), 1057.
6. 100 um
Resist removal
100 nm Au
100 nm Si
substrate
resist
Si/Au film
6
Tube 1
Tube 2
Tube 3
Tube 4
Tube 5
The final structure is
10x smaller!
7. 10 µm
Summer REU 2015: Transportation Electrification Cynthia Yu
Results: Tubular Structures
100 µm
Over 9 layers!Optical microscope images of Ge/Ti experimental
process of rolled-up structures.
40 nm Ge/3 nm Ti
SEM images of 3D self-rolled structures for all-solid-state batteries.
(a) 10 nm Si/10 nm Au, (b-c) 10 nm SiO2/10 nm Ag and (d) 40 nm Ge/3 nm Ti
77
(a)
5 µm
(b)
5 µm 5 µm
(d)
5 µm
(c)
10 µm
(d)
8. • Fabricate a bilayer self-rolling thin film using different materials
and thicknesses
• Reduce footprint area
• Method to be used in future battery application
8
Summer REU 2015: Transportation Electrification Cynthia Yu 8
Summary
Acknowledgements:
- Fablab: Tom Loughran
- MSE: Allen Chang
Garrett Wessler
- Fablab and AIM Lab staff & facilities
- NSF Grant number:
EEC 1263063
- REU Site: Summer Engineering
Research Experiences in
Transportation Electrification
5 µm 5 µm100 µm
cyu601@gmail.com
Our Summer Research Team
Editor's Notes
Cynthia Yu
Dr. Marina Leite
Department of Materials Science and Engineering
University of Maryland
My research project
fabrication of 3D self-rolled thin-films for high-density energy storage devices
Today I will be talking about how we fabricated self-rolling thin-films that result in a 3D tubular structure.
Li-batteries: small and light,
yet can hold an enormous amount of energy,
IDEAL in everyday consumer electronics,
HEV, EV, solar charging.
ALSO low maintenance and is environmentally friendly
BOUND to be limitations: poor cycle life,
the rise in internal resistance and many safety issues.
CLIP , a laptop Li-ion battery catches on fire and explodes due to overheating.
This is the result of a liquid electrolyte leakage and is a main issue to be addressed.
Typical rechargable battery: ANOD and CATHODE
Seperated by LIQUID ELECTROLYTE
25 microns
By creating ALL-SOLID STATE BATTERY
Uses SOLID ELECTROLYTE: able to shrink size
Able to minimize further by using a thin-film process
Electrolyte: < 1micron
Go even further by implementing 3D structure
To ROLL structure into a tube
RESULTS: LARGE SURFACE AREA AND SMALL VOLUME FOOTPRINT!!!
-Fabricate these self-rolled thin films
START: substrate…
…..photolithography to create the patterns of photoresist used to create tubes.
-NEXT…position sample at an angle in E-beam deposition.
KEY POINT to perform an angled deposition so that a GAP results,
where the substrate is exposed for next step.
-By using selective etching,
entire sample is placed in a solvent
-solvent enters through the GAP created and slowly etches away the photoresist.
As the layers are freed, the bilayers wind up to relieve the strain between the layers. Resulting in a tube.
Here is a short animation showing the self rolling process as the photoresist is removed.
The tubes formed upon the strain relief between the two layers.
footprint area of the final structure is 10x smaller than starting flat counterparts
Experimented with different bilayer materials
Ge/Ti, Si/Au, Si/Ag as well as their thicknesses
Able to measure inner/outer diameter and number of windings.
In summary, this summer I was able to successfully fabricate a bilayer self-rolling thin film
which can be implemented in future battery fabrication.
THANK YOU
Tom from the Fablab
Our summer research team
And REU and NSF for giving me this opportunity.
