384
P. Kumar
layer reduces and the pore tip current density increases results in smaller pores and
thicker walls. On the other hand, polishing of silicon in aqueous HF solution is
known to be preceded by silicon oxide formation. The oxide is then dissolved by
HF through formation of a fluoride complex in the solution. With increasing HF
concentration in etching electrolyte the dissolution rate of silicon oxide increases
that in turn increases the critical current density at which the surface is covered by
oxide. As a result, walls become thicker and the pores become smaller with increasing
HF concentration (Kumar 2009; Michler et al. 2000; Zhang 2004).
3 Energy Storage Devices
An energy storage device is a device that is used to store electric energy when
needed and releasing it when required. High-power and high-energy storage devices
is a long-standing goal of material scientist that is source of portable energy for
transportation to reduce the reliance on fossil fuels. To encounter the problem of
global warming due to the use of fossil fuels, the energy storage device technology
in fields such as renewable energy generation and hybrid automobile systems is
an emerging field of research. Energy can be stored in a range of ways depending
upon the intentional use with each method having its advantages and disadvantages.
Batteries, fuel cells, and supercapacitors have been used and studied since long to
store electrical energy. The need to develop energy storage devices to store energy
from sustainable and renewable energy sources is leading society to develop energy
from sources that are not continuously available, such as the wind and sun. Several
types of energy storage devices are available with different properties given in Table 1.
Energy generated from renewable sources has to be converted and stored by highly
efficient and eco-friendly ways for sustainable economic growth and environment
protection. Rechargeable batteries and supercapacitor storage devices are the most
common means of storing energy.
However, there are a number of tasks that need to be addressed in order to improve
their performance and to make them economically viable. Therefore, electrochemical
devices that can deliver high energy density are increasingly important. As renewable
energy sources become increasingly predominant the need for high-power storage
and high energy-density devices with long durability is greater than ever. The development of suitable materials for these devices originates with a complete understanding of the complex processes that govern energy storage and conversion spanning
several orders of magnitude in time and length scales. Figure 4 shows the Ragone
plot of the energy storage and power handling capacity of some different storage
techniques.
P. Kumar
layer reduces and the pore tip current density increases results in smaller pores and
thicker walls. On the other hand, polishing of silicon in aqueous HF solution is
known to be preceded by silicon oxide formation. The oxide is then dissolved by
HF through formation of a fluoride complex in the solution. With increasing HF
concentration in etching electrolyte the dissolution rate of silicon oxide increases
that in turn increases the critical current density at which the surface is covered by
oxide. As a result, walls become thicker and the pores become smaller with increasing
HF concentration (Kumar 2009; Michler et al. 2000; Zhang 2004).
3 Energy Storage Devices
An energy storage device is a device that is used to store electric energy when
needed and releasing it when required. High-power and high-energy storage devices
is a long-standing goal of material scientist that is source of portable energy for
transportation to reduce the reliance on fossil fuels. To encounter the problem of
global warming due to the use of fossil fuels, the energy storage device technology
in fields such as renewable energy generation and hybrid automobile systems is
an emerging field of research. Energy can be stored in a range of ways depending
upon the intentional use with each method having its advantages and disadvantages.
Batteries, fuel cells, and supercapacitors have been used and studied since long to
store electrical energy. The need to develop energy storage devices to store energy
from sustainable and renewable energy sources is leading society to develop energy
from sources that are not continuously available, such as the wind and sun. Several
types of energy storage devices are available with different properties given in Table 1.
Energy generated from renewable sources has to be converted and stored by highly
efficient and eco-friendly ways for sustainable economic growth and environment
protection. Rechargeable batteries and supercapacitor storage devices are the most
common means of storing energy.
However, there are a number of tasks that need to be addressed in order to improve
their performance and to make them economically viable. Therefore, electrochemical
devices that can deliver high energy density are increasingly important. As renewable
energy sources become increasingly predominant the need for high-power storage
and high energy-density devices with long durability is greater than ever. The development of suitable materials for these devices originates with a complete understanding of the complex processes that govern energy storage and conversion spanning
several orders of magnitude in time and length scales. Figure 4 shows the Ragone
plot of the energy storage and power handling capacity of some different storage
techniques.