Supercapacitor

VSAT 2022

What are Supercapacitors?

Electronic devices called supercapacitors are used to hold incredibly enormous amounts of electrical charges. They are also referred to as ultracapacitors or double-layer capacitors. Supercapacitors store electrical energy utilizing two methods, double-layer capacitance and pseudocapacitance, as opposed to a traditional dielectric. Double layer capacitance is electrostatic in origin, whereas pseudocapacitance is electrochemical, hence supercapacitors function as a hybrid of conventional capacitors and batteries. Utilizing this method, capacitors as high as 12000 F can be produced.


The capacitance of a supercapacitor is more than 15 million times more than the self-capacitance of the entire planet earth, which is only approximately 710 F. The maximum charge voltage of a supercapacitor is typically between 2.5 and 2.7 volts, in contrast to the high maximum working voltage that a conventional electrostatic capacitor may have.


Difference between Capacitor and Supercapacitor

Sl. No

Capacitor

Supercapacitor

1.

A capacitor is a passive electrical device with two terminals that retains charge as an electric field between its metal plates. It consists of two metal plates that serve as the anode and cathode of electrodes that are separated by a material known as the dielectric.

Supercapacitor is another name for a double-layer capacitor, ultracapacitor, or super cap. Active carbon is used as the electrode material for a supercapacitor's electrodes. In contrast to normal capacitors, which use dielectric materials as a separator between the anode and cathode, supercapacitors use a separator.

2.

The current seeks to travel through the insulating material when the source voltage is supplied between the two terminals of a capacitor, but the material resists the flow of electrons.

Either electrostatic double-layer capacitance (EDLC) or electrochemical pseudocapacitance or a combination of the two known as a hybrid capacitance is used by supercapacitors to store charge.

3.

The insulation material continues to obstruct the flow of electrons even though the voltage across the capacitor terminal is equal to the applied voltage. This resistance phenomenon causes a shift that has the effect of storing energy as an electrostatically charged field.

Metal foil (electrodes) with layers of activated carbon makes up supercapacitors. The separator is sandwiched between these foils. An ion-permeable membrance such as graphene (used in contemporary supercapacitors), serves as the separator and allows for the exchange of electrolyte ions between the electrodes.


Types of Supercapacitors

Supercapacitors are classified into three types:

  • Electrostatic Double Layer Capacitors

Two electrodes, a separator, and an electrolyte are components of these kinds of capacitors. The mixture of positive and negative ions dissolved in water is known as an electrolyte. A separator separates the two electrodes. The electrostatic double-layer capacitance of the carbon electrodes or their derivatives used in these supercapacitors is significantly higher. Electrostatic double-layer capacitors have a smaller charge separation than normal capacitors; it is between 0.3 and 0.8 nm.

  • Pseudo Capacitors

Electrochemical pseudo-capacitors are another name for pseudo-capacitors. These capacitors use conducting polymer electrodes or metal oxide electrodes with substantial electrochemical pseudocapacitance. By transferring electron charges between an electrode and an electrolyte, these components store electrical energy. A reduction-oxidation reaction, or redox reaction, can accomplish this.

  • Hybrid Capacitors

The double-layer capacitor and pseudo-capacitor techniques are used to create the hybrid capacitors. Different electrodes with various properties are utilized in these components. The ability of one electrode to display electrostatic capacitance and the ability of the other electrode to display electrochemical capacitance. A few instances of hybrid capacitors are lithium-ion battery capacitors.


Characteristics of Supercapacitors

1. Charge Time

Charge and discharge times for supercapacitors are equivalent to those of regular capacitors. Due to its low internal resistance, high charge and discharge currents are achievable. A mobile phone battery is a good example of a battery that often takes several hours to fully charge, but supercapacitors can reach the same charge state in less than two minutes.

2. Specific Power

The maximum power output divided by the total mass of the device is used to compare various technologies using the specific power of a battery or supercapacitor. The specific power of supercapacitors is five to ten times greater than that of batteries. For instance, a typical supercapacitor has a specific power of about 10 kW/kg, whereas Li-ion batteries have a specific power of 1 to 3 kW/kg.

3. Cycle Life of Supercapacitors

Batteries only have a cycle life of 500 times or more; however, supercapacitors can be charged and discharged millions of times and have a virtually limitless cycle life. As a result, supercapacitors are highly beneficial in applications that frequently need to store and release energy.

4. Safety of Supercapcitors

Supercapacitor batteries are safer than conventional batteries when mishandled. Supercapacitors do not heat up as much as batteries do because of their low internal resistance, but batteries have been known to explode owing to excessive heating when short circuited.


Working of Supercapacitor

  • The capacitors use electrostatics or static electricity to store energy. Between the two plates of the supercapacitor's electrolyte solution are ions that are both positively and negatively charged. One of the supercapacitor's plates typically develops a positive charge while the other plate acquires a negative charge when a voltage is placed across the plates.

  • As a result, the positively charged plate attracts the positively charged ions in the electrolyte solution, while the negatively charged metal plate attracts the negatively charged ions. On the inner surface of both plates, a thin coating of ions is deposited. As a result, an electrostatic double layer forms, which is like connecting two capacitors in series.

  • Each of the two resulting capacitors has a high capacitance value because the space between their charge layers is relatively small. Calculate the supercapacitor's total capacitance by dividing (C1 × C2) by (C1 + C1).


Application of Supercapacitor

  • Electric vehicles

  • Windmills

  • Flywheel in machines

  • MP3 players

  • Camera flash

  • Automotive industry regenerative braking

  • Industrial electrical motors and static memory (SRAM)s


Disadvantages of Supercapacitor

  • They discharge themselves more frequently. This is significantly higher than a battery.

  • Low voltages exist within individual cells. Because of this, series connections are necessary to attain greater voltages.

  • Compared to an electrochemical battery, there is a significantly lesser amount of energy stored per unit weight. For an ultracapacitor, this is equivalent to 3 to 5 W.h/Kg as opposed to 30 to 40 W.h/Kg for a battery.

  • In comparison to batteries, it delivers a poor energy density. This is equivalent to between one-fifth and a tenth of the battery's energy.

  • It cannot be utilized in circuits with AC or higher frequencies.


Interesting Facts

  • Electrochemical double-layer capacitors, supercapacitors, and ultracapacitors are distinct types of electronics.

  • It can function as an energy storage system that is plug-and-play.

  • Energy density and power density are calculated using electrode area and weight.

  • Voltage balancing is not necessary, unlike with a battery stack.


Summary

Supercapacitors are electronic devices that are used to store extremely large amounts of electrical charge. They are also known as double-layer capacitors or ultracapacitors. Instead of a conventional dielectric, supercapacitors store electrical energy using two techniques: double-layer capacitance and pseudocapacitance. Due to the electrochemical basis of pseudocapacitance and the electrostatic origin of double-layer capacitance, supercapacitors act as a combination of regular capacitors and batteries.

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FAQs on Supercapacitor

1. What is the difference between power and energy?

Although "power" and "energy" are sometimes used synonymously, there is a significant distinction between the two terms because power is appropriately defined as the rate at which the work is done, whereas the energy is the ability to do any work. The unit of power is Watt and the unit of energy is joules.

2. What is the purpose of a dielectric in a capacitor?

The area of the plates and their distance from one another determine a capacitor's capacity. Without affecting the size of the plates or their separation, the dielectric serves to enhance the capacitance, C = Q/V. Here's how it functions.

3. What is the difference between a battery and a supercapacitor?

While supercapacitors are lighter, have more robust working limitations, have a longer life expectancy, and have an unmatched power density, batteries provide a superior energy density and have a higher breakdown voltage.

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