M o d u L e 2 : a p p L i c a t I o n s a n d I m p L i c a t I o n s

Figure 12). Nanostructured lithium batteries are becoming a commercial 
reality, such as the Altairano NanoSafe™ and 123 Systems Batteries.
Figure 12:
Cross-sectional views of 
Cu-nanostructured current collector 
before (left) and after (right) Fe
3
O
4
deposits
Image: P. L. Taberna et al., ‘High rate 
capabilities Fe
3
O
4
-based Cu nano-architectured 
electrodes for lithium-ion battery applications’, 
Nature Materials, 2006, 5:567–573, reprinted 
with the permission of Macmillan Publishers 
Ltd, © 2006

---

218
N A N O T E C H N O L O G I E S : P R I N C I P L E S , A P P L I C A T I O N S , I M P L I C A T I O N S A N D H A N D S - O N A C T I V I T I E S
Supercapacitors
Supercapacitors are another way of storing electricity that can benefit from nanotechnology. They are 
needed in devices that require rapid storage and release of energy, for instance hybrid-electric and 
fuel cell-powered vehicles. They are constructed of two electrodes immersed in an electrolyte, with an 
ion permeable separator between them. Each electrode-electrolyte interface represents a capacitor, 
so the complete cell can be considered as two capacitors in series. The focus in the development of 
these devices has been on achieving high surface area with low matrix resistivity. The most remarkable 
property of a supercapacitor is its high power density, about 10 times that of a secondary battery. The 
maximum power density of a supercapacitor is proportional to the reciprocal of its internal resistance. 
A number of sources contribute to the internal resistance and are collectively referred to as Equiva-
lent Series Resistance (ESR). Contributors to the ESR include the electronic resistance of the electrode 
material and the interfacial resistance between the electrode and the current-collector. Carbon, in its 
various forms, is currently the most extensively used electrode material in supercapacitors. A typical 
commercial supercapacitor can produce a power density of approximately 4 kW/kg. Nanotubes can 
be used to increase the power density of supercapacitors, since the nanoscale tubular morphology of 
these materials offers a unique combination of low electrical resistivity and high porosity in a read-
ily accessible structure. Single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs) are 
under investigation. Research has shown that the use of thin-film electrodes with multi-walled aligned 
nanotubes increases the specific power density (laboratory results of 30 kW/kg have been reported), 
as a result of the reduction inESR.
Energy 
savings
Energy savings can be achieved in numerous ways, such as improving insulation of residential homes 
and offices; more efficient lighting; and using lighter and stronger materials to build devices which 
would then require less energy to operate. Moreover, a large portion of energy is lost during its trans-
port, so there is a need for a more efficient electric grid to transport energy. Nanotechnologies can 
potentially be applied to all of these energy-saving materials and technologies.
Catalysis
Catalysis is of vital importance in our society and constitutes a cornerstone of life from biological 
processes to the large-scale production of bulk chemicals. The availability of plentiful and inexpen-
sive chemicals relies on industrial catalytic processes and, without them, it would be impossible to 
maintain the current living standard of the present human population. Other technologies also depend 
on catalysis, including the production of pharmaceuticals, means of environmental protection, and 
the production and distribution of sustainable energy. As already discussed in some of the previous 
sections, many technological advances required to