Conductive Paper and Textile for Rational
Designs of Energy Storage Devices
Liangbing Hu, Yi Cui
Material Science, Stanford
Renewable Energy Landscape
Production
‐ Wind
‐ Heat ‐ Solar
Transparent Electrode
Transmission
‐ Electrical grid
Storage
‐ Electrochemical
‐ Chemical fuels
Usage
‐Light
‐Building Supercapacitors
Li-ion Batteries
2
Manipulating Electron, Ions, and Photons in Energy Devices
Electrons
Photons
Ions
Supercapacitors
Li-ion Batteries
Electrons
Transparent Electrodes
3
Supercapacitor
Specific power (w/kg)
Comparison of Energy Storage Technologies
106
Capacitors
105
CNT, MnO2 and Si Nano-Nets
104
Supercapacitors
103
102
Batteries Fuel cells
10
1
10-2
10-1
1
10
102
103
Specific energy (wh/kg)
Li-ion Battery
Important parameters:
- Energy density (Energy per weight or volume)
- Power density (Power per weight or volume)
- Cycle life and safety
- Cost
4
Energy Storage Mechanism
Capacitor
-
+
+
+
+
Metal
+
Supercapacitor (Electrochemical capacitor)
1
E = CV 2
2
1
C~
thickness
Dielectrics, thickness: >1000nm.
+
+
+
+
Metal
+
-
+
+
+
+
+
-
Electrolyte solution
Double layer thickness, <1nm
Battery
+++
+++
+++
+++
+++
-
-
-
Electrolyte solution
Capacitors and supercapacitor: surface storage.
Battery: bulk storage.
5
Supercapacitor Components
The metal current collectors account for 20 ~ 30%
of total weight
Electrode
Cu mesh
Al mesh
Step out
Conductive paper
Conductive textile
6
The Building Block: Single-Walled Carbon Nanotube
Dimensions:
•Diameter ~ 1nm
•Length up to 4 microns
Mechanical/Chemical Properties
•Mechanical flexible
•Chemically inert
Electrical Properties
•Conductivity ~ 3x105 S/cm
•Mobility ~ 105 cm2/V*sec
•Both metallic and semiconducting
7
Carbon Nanotube Ink for Conductive Coating
Surfactant
Carbon nanotube powder
Carbon nanotube ink
These are critical for obtaining uniform coating
•
Dispersion of carbon nanotubes in solvent
•
Ink viscosity
•
Surface tension match between ink and
substrate
•
Encapsulation for enough mechanical adhesion
Bad coating
on plastic substrate
Good coating
on plastic substrate
Coating on paper is
much easier! 8
Supercapacitor – Double Layer Capacitor
+
+
+
+
+
+
+
+
+
+
+
•Energy Storage by Charge Separation,
like regular capacitor
•C=Aε/d
•d is ~ 1 nm, 1000 time smaller than
regular capacitor
•A is much bigger than regular
capacitor.
•Nanomaterials with high surface area
(~ 1000m2 per gram) are with large
application potential.
9
Charges stored in Electrical Double Layer
Porosity at two different scales
Greatly enhance surface areaÆhigh A
X
100 μm
Microporous carbon nanotube film
Macroporous paper fiber network
10
Conductive Paper Fabrication-Scalable Process
Silver Nanowires
Carbon nanotubes
2 μm
11
Hu, Choi, Yang, Cui et al. PNAS, 2009
Conductive Paper is highly conductive,
mechanical flexible and stable
CNT/paper
12
Supercapacitor with Conductive Paper
Conductive paper
Separator paper
Conductive paper
•
IR voltage drop can be used
to calculate resistance
and device power
13
Performance of conductive paper for Supercapacitor
High capacitance
Stability
14
Energy Density and Power Density
15
Li ion Battery- An Excellent System to Store Energy
Cost breakdown
Nature Mater. 2004
16
Li-ion Batteries: Opportunities and Challenges
Disposable,
Consumer Electronics
Cost
Power Tools
Power Density
Energy Density
Electrical Vehicle
Large Scale Energy Storage
For grid applications
Energy Density
Cost
Size increases
~ 5000 batteries
Stanford paper battery
17
Light-Weight Current Collector Based on Conductive
Paper and Textile
•Supercapacitor and Li-ion battery share the similar device structure
•The metal current collectors account for ~ 20-30% of total weight
Cu mesh
Al mesh
Step out
Conductive paper
Conductive Textile
18
Conductive Paper Based Li-ion Batteries for Electrical
Vehicles
Use Carbon nanotube/paper
To replace Cu and Al current collector
19
Performance of conductive paper for Li-ion Battery
Good enough for electrical
vehicle applications
20
Weight Saving Using Conductive Paper
21
New Electrode-Current Collector Design
for Li-ion Batateries
(a)
Conductive, porous current collector
Fill in battery electrode materials
(b)
Flat metal current collector
Coat battery electrode materials on surface
22
L. Hu et al. Submit to Adv. Mater
Stretchable, Conductive Textile
- Simple process
Hu, Cui et al. Nano. Lett, 2010
23
Conductive Textile: Highly Conductive and
Stretchable
Conformal coating carbon
nanotubes on textile fibers
24
Light-weight, Porous Textile Conductor That
Allows Loading of Other Materials
(c)
200 μm
200 μm
25
Electrochemical Stability of Conductive Textile
Stability Window: 1 V to 3.8 V
Valid for Li4Ti5O12 (1.6 V) and LiFePO4 (3.6 V)
26
Extreme Simple Process for Battery Material Loading
1 μm
L. Hu et al. Submit to Adv. Mater
27
Voltage Profile Comparison
L. Hu et al. Submit to Adv. Mater
28
Impedance Comparison between our structure and
traditional structure
29
Full Cell Cycling Performance
30
Advantages of Using New Electrode-Current Collector
Design
5
Process
separator
100 mg/cm2
1
Process
separator
20 mg/cm2
Traditional
Ours
31
Conclusion
•
Conductive paper for double layer capacitor
•
Conductive textile for psuedocapacitor with high mass loading
•
Conductive paper based Li-Ion batteries for electrical vechile applications
•
A new design for electrode-current collector design which allows high mass
loading for grid applications
32
Acknowledgement
Cui Group
Funding
33
Questions?
34