Biomedical Engineering Reference
In-Depth Information
absence of a cheap and reliable energy storage option constitutes a
major inconvenience and an obstacle for the further development of
renewable energy sources. In the past, this type of energy sources
have been discriminated, but new technology makes alternative
energy more attractive, practical, and price competitive than fossil
fuels. It is expected that future generations will usher in a long-
expected transition away from oil and gasoline as our primary
fuel. High performance of such technologies is mainly achieved
by designing sophisticated device structures with multiple
materials; for example, tandem cells in photovoltaic devices. For
example, inorganic/polymer semiconductors with poor charge
carrier mobility limit the energy conversion efficiency of organic
photovoltaic cells to less than 6%. Thermoelectric devices typically
possess an energy conversion efficiency of less than 3%. Portable
electric power sources have lower energy and power density largely
resulting from poor charge and mass transport properties.
The demand for advanced energy storage devices is
continuously increasing. It comes from many different directions
having in common the potentially high social and technological
benefits of each target application. The lithium-ion battery is a
representative system for such electrochemical energy storage and
conversion. Nowadays, the effectiveness of lithium-ion batteries is
palpable as — having the advantage of light weight and a reduced
size —it is used for consumer electronics such as cellular phones,
digital cameras, and laptop computers [1]. Other potential uses
of renewable energy are in (i) miniaturized portable electronics
(battery on a chip, thin-film microbatteries), (ii) rural electricity,
(iii) aerospace applications, and (iv) electric and hybrid vehicles
(EVs, HEVs), among others. Application (iv) requires high energy
and power densities. However, it is a challenge for scientific
community to develop a high power density because of a large
polarization at high discharge-charge rates of the battery. This
polarization is caused by slow lithium diffusion in the active
material and increases in the resistance of the electrolyte when
the discharging-charging rate is increased. The characteristics
of the energy storage device may vary notably depending of the
potential application. Safety issues, environmental protection,
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