1) The document describes research into fabricating 3D self-rolled thin-film structures for use in high density energy storage devices like lithium-ion batteries. 2) Using techniques like angled e-beam deposition and selective etching, the researchers were able to form rolled-up nanotube structures with diameters controlled down to the micrometer scale from thin films of materials like silicon, gold, and titanium. 3) Preliminary results show the 3D nanotube architecture allows for a small volume footprint with a large surface area, which could provide advantages for lithium-ion batteries by accommodating high volume expansion during charging and discharging over many cycles.

1. Fabrication of 3D Self-Rolled Thin-Films for High Density Energy Storage Devices
Cynthia Yu1,2, Griffin Godbey1,2, Chen Gong1,2, Clayton Blythe1,2, and Marina S. Leite1,2
1Department of Materials Science and Engineering, Univ. of Maryland, College Park, MD
2Institute for Research in Electronics and Applied Physics, Univ. of Maryland, College Park, MD
Introduction
Alternatives for 3D devices
Results
SEM images of 3D self-rolled structures for all-solid-state batteries.
(a) 10 nm Si/10 nm Au (calculated diameter = 4.1 µm), (b-c) 10 nm SiO2/10 nm Ag
(calculated diameter = 3.0 µm), and (d) 10 nm SiO2/10 nm Au (calculated diameter = 3.5 µm).
Optical microscope images of Ge/Ti experimental process of rolled-up structures.
(a) Photolithography on a SiO2 substrate 1’’x 1’’ (b) Angled E-beam deposition of 40 nm Ge(Layer1)
and 3 nm Ti(Layer2) (c,d) Rolled-up Ge/Ti tubes result after selective etching process (e) Ge/Ti
tubes magnified (measured inner diameter 19.22 µm) and (measured outer diameter 38.16 µm).
Lithium-Ion battery:
- Lightweight
- High electrochemical potential
- High energy density per weight
- Low maintenance
- Holds charge
- Handle many charge/discharge cycles
Goals:
- Fabricate an all-solid-state:
- Li-ion battery
- 3D geometry
- Small volume footprint
- Thin-film fabrication
- High storage and power capacity
Photolithography
Selective
Etching
- controlled
etching rate to
form tubes
Angled E-beam
Deposition
Process
Experimental Process
Substrate
Photoresist
Layer 2
Layer 1
GAP
Substrate
Substrate
Photoresist
removal
(a) Nat. Mater.,5(7), 567, 2006. (b) Nano Letters, 11(2), 377, 2011. (c) Nat Nano, 6(5), 277, 2011. (d) Nano Letters, 12(1), 505-511, 2012.
(e) Nat Mater., 9(4), 353, 2010. (f) Advanced Functional Materials, 18(7), 1057, 2008.
Rolled-up
Tubes!
sacrificial layer
SiO2 substrate
layer 1, thickness t1
layer 2, thickness t2
z
y
x
5 µm
Easy control of tube diameter:
The equation for finding the
curvature (K) for the self rolled
structure of a bilayer film.
Our 3D architecture approach - Tubes
The advantages of our 3D architecture tubular structure:
- Allow the hollow interior to accommodate the large volume expansion
suffered during lithiation
- Provide large surface area and small volume footprint
Future Work
- Advance our understanding
of how capacity fades in
high-density energy and
power all-solid-state
Lithium-ion
batteries
- Fabricate a quad-layer
Li-ion battery and identify
optimal stacking
- Fablab: Tom Loughran
- MSE: Allen Chang
Garrett Wessler
- Fablab and AIM Lab staff
and facilities
- NSF Grant number:
EEC 1263063
- REU Site: Summer
Engineering Research
Experiences in
Transportation Electrification
Acknowledgments
charge discharge many cycles
Substrate
Substrate
Photoresist
Substrate
(a) (b) (c)
(e) (f)
Anode
Electrolyte
Cathode
Current collector
Current collector
Barrier layer
Over 9
layers!
10 µm
38.16 µm
19.22 µm
100 µm
(a)
5 µm
(b)
5 µm 5 µm
(d)
5 µm
(c)
Strainedbilayer
sacrificiallayerremoval,self-rollingprocess
RollingdirectionRollingdirection
Photoresist
Substrate
Rolling
direction
GAP
Layer 2 / Layer 1
(a) (b) (c)
Tubes formed upon the strain relief between deposited thin-films
Rolled-up
Tubes!100 µm100 µm100 µm
where: K > 0 for a rolled-down tube
K < 0 for a rolled-up tube
ti is thickness of layer 1, layer 2
νi is the Poisson ratio
Ei
’ = Ei /(1- νi
2)
Ei is Young’s modulus
ηi = (1 + νi)
εi
o is the initial strain = CTEi*ΔT
G. P. Nikishkov, J. Appl. Phys. 94, 5333, 2003, Y. Nishidate and G. P. Nikishkov, J. Appl. Phys. 100, 113518, 2006.
Tube1
Tube2
Tube3
Tube4
Tube5
(d)
(e)