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What is an EDLC capacitor and how does it work?

2023-12-04 10:58:58

There are many types of electrical energy storage devices, and among them, there are many types of batteries, which are categorized in various ways. Primary and Secondary Batteries Batteries are categorized into primary and secondary batteries based on whether they are rechargeable or not, with primary batteries being non-reusable and secondary batteries being reusable. For energy storage applications, secondary batteries should be used.


Physical batteries are devices that utilize physical phenomena to store energy, and no chemical reaction occurs during the energy storage process. For example, a pumped storage plant that uses electricity to pump water into a reservoir at night, converting the electricity into potential energy for storage; a flywheel that uses a motor to drive a flywheel to rotate at high speed, converting the electricity into mechanical energy for storage. All of the above devices are physical batteries, but the form of storage is not electrical energy, so they cannot be called electronic components.

But have you heard about EDLC capacitor? 

But the EDLC capacitor is a secondary battery in the physical battery, it is a kind of electric energy in the form of charge storage components. There is no energy conversion in this type of energy storage, which has many advantages, for example, no chemical reaction occurs in the process of energy storage, and the performance will not be greatly reduced after hundreds of thousands of times of charging and discharging; the loss in the process of energy conversion is small, and it can be charged and discharged quickly and efficiently. However, the DLC capacitor is not without disadvantages. Compared with chemical secondary batteries, it is difficult to realize miniaturization and large capacity. In addition, all capacitors are rarely categorized as secondary batteries. This is because the capacitor voltage varies from 0V to the rated voltage depending on the charge, unlike chemical batteries that provide a constant voltage. However, when capacitors are combined with a DC-DC circuit (to obtain a stable output voltage), they can be used in the same way as secondary batteries. In this paper, we will examine the EDLC capacitor in terms of the performance of a secondary battery.


Energy density and power density of batteries and capacitors Energy density and power density are two important indicators of battery performance. Energy density indicates the amount of energy stored per kilogram of battery, while power density refers to the maximum output power per kilogram of battery, with the higher the output power the greater. The higher the energy density, the longer the range of an EV, and the higher the power density, the higher the instantaneous power.

   -Example: - Maximum output power at startup: 10kW - Output power at constant speed: 100W Compare a 1kg Li-ion battery and a capacitor on an EV. A lithium-ion battery with an energy density of 100W-h/kg can run for 1h at a constant speed, while a capacitor with an energy density of 8W-h/kg can run for t = 8W-h/100W = 0.08h, less than 5min. However, a lithium-ion battery, with a maximum output power of about 1kW, does not provide a large instantaneous power at startup, which affects the acceleration performance of the vehicle. Capacitors, on the other hand, can provide several tens of kilowatts of output power and can provide greater start-up acceleration.


Why EDLC capacitor is an ultracapacitor?

EDLC capacitor "super" energy storage of the key secrets, mainly in its electrode surface coated with a very large surface area of activated carbon, so that the ions in the electrolyte as much as possible to fill the porous surface of activated carbon, to obtain the largest possible surface area of contact, and due to the size of the capacitor capacity and the two electrodes of the EDLC electric double layer area Since the capacitance of a capacitor is directly proportional to the area of the electrical double layer of the two electrodes of the EDLC, this allows the EDLC capacitor to provide a very high capacitance per unit volume, much higher than other types of capacitors.


How does an EDLC capacitor work?

When a voltage is applied to the electrodes of an EDLC capacitor, ions in the electrolyte are attracted to the electrodes and form a capacitive structure capable of storing charge on the surface of each of the positive and negative electrodes - like two capacitors connected in series - creating what is known as the "double layer effect". The so-called "double layer effect (Electric Double Layer Effect)", with the electrolyte ions on the electrode surface of the adsorption and detachment, the EDLC capacitor also completed the capacitance of the charging and discharging.


What is the difference between a traditional capacitor and a EDLC capacitor ?

  • Energy Storage Mechanism:       

   Traditional capacitors store energy by accumulating and holding an electrical charge between two conductive plates, separated by an insulating material (dielectric). When voltage is applied, electrons accumulate on one plate while an equal number of electrons are repelled from the other plate, storing energy in an electric field. But use a different mechanism to store energy. They have a high surface area, often utilizing activated carbon or other porous materials coated with an electrolyte.

  • Energy Density: 

   Traditional capacitors<EDLC capacitors(<batteries)

  • Application

   EDLC capacitors are used in applications requiring quick bursts of power, such as regenerative braking in vehicles, energy recovery systems, and some renewable energy applications. The traditional capacitors are ideal for rapid charge and discharge applications, such as smoothing power supply voltages or filtering signals.

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