1. Supercapacitors
as Energy Storage Devices

2. Capacitance
● A measure of ability to store electric charge
o Ratio of magnitude of charge on either conductor
to potential difference/voltage between
conductors
Capacitance
Charge on either
conductor
Potential difference

3. What is a capacitor?
Dielectric, K
Remember Physics 153?

4. Energy Storage in Capacitor
The more work you can put into the
capacitor…
That essentially becomes the energy the
capacitor stores.

5. Wait, what are dielectrics?
To refresh your memory:
● Store more energy than usual
o Polarization of dielectric molecules
o Charge separation between plates
● However, they put a limit on how much
voltage can be applied

6. Dielectric Breakdown
Dielectrics prevent current from flowing
between electrodes.
It basically acts as an insulator.
But if you apply too much voltage…
It conducts!

7. How can we increase the amount of
charge stored if we can’t apply too
much voltage?

8. Optimal Capacitor
Easiest way to increase capacitance
(hence, energy storage):
● Increase surface area
● Decrease plate separation
This is exactly what a supercapacitor does.

9. Also known as...
● Electric Double Layer Capacitor (EDLC)
● Electrochemical Double Layer Capacitor
● Double Layer Capacitor

10. Supercapacitor

11. Battery

12. Battery vs. Supercapacitor
• The cycle life of battery cells is restricted
to one thousand discharge/recharge
cycles
• Electron transfer occurs across the two
electrodes with the electrolyte as the
medium transfer
• The charge storage by REDOX reaction
occurs in the battery
• Lower power density
● 100 times shorter than the
conventional electrochemical cell
● REDOX reaction across the double
layers
● In the form of Helmholtz capacitance
and space-charge capacitance
● Higher power density
● Functions over a larger range of
temperature

13. Battery vs. Supercapacitor

15. Capacitance
Helmholtz Layer Capacitance
(Electrochemical)
• The charge transfer process at the electrode
depends on the work function, φ of the metal
electrode.
• Gs ≈ ½ (CV2)
the change in the Gibbs free energy
of
ion solvation
• Their behaviour depends on the dipole
moment that controls the current density and
dielectric constant
Space Charge Capacitance
(Electrostatic)
• Large area of porous carbon electrodes
facilitates the adsorptions of the solvation ions
from the electrolyte
• E (electric field) = ∆V/D and the space charge
capacitance value is determined by C = (∈A)/D
• It is measured that the double layer’s field
strength is about 5000kV/mm

16. Method of Processing
● Efficient
● Less time consumption
● Uses inexpensive materials
■LightScribe DVD burner
■DVD disc
■Graphite Oxide
● Can manufacture into different size for various purposes
● Easily integrated to modern electrical devices

17. Method of Processing
1. A layer of plastic is attached on the
surface of a DVD disk
2. Graphite Oxide is then coated on the
plastic
3. Laser in the LightScribe DVD optical
drive will etch the on the surface of
the graphite oxide
4. The graphite oxide will turn into
graphene once it has been etched by
the laser
5. The pattern on the graphene has
been already designed into different
structure for various purpose

18. Applications of Supercapacitors
● Reduced size and weight but without reducing
performance and durability
● Fully integrated with smaller and lightweight
systems
● Consumer, industry, military, medical and
transportation use
○ Laser power supply
○ Medical pacemaker
■Energy pulse released is able to charge up a
pacemaker to 500 Joules

19. Marketing and Commercial Logistics
● Large multinational firms (Maxwell Technologies Inc.)
○ Target the electronics industry
● Dedicated capacitor firms
○ Large energy storage applications
● Early stages of commercialization
● Began to move into more mainstream applications
● Transitioning from an emerging phase to a growth phase
● Hybrid electric vehicle and renewable energy markets

20. Benefits and Limitations
● Virtually unlimited cycle life
○ Can be cycled millions of time
● High specific power
○ Low resistance to high load currents
● Excellence on low temperature charge
and discharge performance
● Cost effective energy storage
● Charges in seconds
○ No end-of-charge termination required
● Can be easily disposed because it is made
out of carbon
● Low specific energy
○ Holds a fraction of a regular battery
● Linear discharge prevents using the
full energy spectrum
● High self-discharge
○ Higher than most batteries
● low cell voltage
● High cost per watts

21. Conclusion
Recently, Dr. Richard Kaner and his team at
UCLA created supercapacitor with energy
density comparable to batteries
Lightweight, flexible electronics… even
electric vehicles!