Modern application status of supercapacitor
- The principle and classification of supercapacitor
- The application status of supercapacitor in the world
- Problems existing in the application of supercapacitor
Supercapacitor is mainly composed of cathode and anode electrodes, electrolyte solution, separator and current collector, in which the separator immersed in the lithium ion battery electrolyte keeps the anode and cathode electrodes separated. Supercapacitor stores energy based on the charge-discharge process at the electrode or electrolyte interface.
The principle and classification of supercapacitor
Compared with traditional capacitors, supercapacitor has a larger effective surface area, which can increase their capacitance by 10,000 times compared to traditional capacitors, while maintaining low equivalent series internal resistance and high specific power.
According to the different charge storage principles, supercapacitor can be divided into three categories: electric double layer capacitors (EDLC), pseudocapacitors (PC), and hybrid supercapacitor (HSC).
Electric double-layer capacitors use the electric double-layer interface formed between the electrodes and the electrolyte to store electric charge. The separator separates the two electrodes. When charging, positive and negative charges accumulate on the surfaces of the two electrodes to form a capacitor.
When discharging, the accumulated charges return to the electrolyte, and a discharge current is generated in the external circuit. At present, the electrode materials of electric double layer capacitors mainly include activated carbon, carbon nanotubes, graphene, etc., which have the characteristics of high conductivity, high strength, corrosion resistance, and high temperature resistance.
The capacitance of pseudocapacitors originates from the redox reaction between electrode materials and electrolytes, and the electrode materials are mainly metal oxides, metal-doped carbons, and conductive polymers. Electron transfer occurs during capacitance generation in pseudocapacitors, and while this electrochemical behavior differs from pure electrostatic double-layer capacitors, it also differs from batteries.
The capacitance of the pseudocapacitor is highly kinetically reversible, and its cyclic voltammogram curve exhibits an approximately rectangular shape, which is a typical capacitive feature.
Hybrid supercapacitor is hybrid systems composed of EDLC electrodes such as graphene or graphite, activated carbon, and pseudocapacitive electrodes such as metal oxides and conductive polymers. Hybrid supercapacitor composed of two different electrodes of different materials break the limitations of the respective characteristics of the constituent elements, and therefore, can exhibit better electrochemical performance than a single supercapacitor.
Hybrid supercapacitor has higher working potentials and larger capacitances, which are 2–3 times higher than conventional capacitors and EDLC and pseudocapacitor, and can maintain cycle stability and high tolerance.
Due to its energy storage mechanism and its own characteristics, supercapacitor batteries can fill the gap between traditional capacitors and batteries, and have both the advantages of high specific energy of batteries and high specific power of traditional capacitors.
The main advantages of supercapacitor batteries include an ultra-long charge-discharge cycle life of more than 1 million times, a wide operating temperature range (-40~70°C), fast charging speed, high power density, and low maintenance requirements. In addition, no harmful chemicals or toxic metals are used in the production, use, storage and dismantling of supercapacitor, so they are green and environmentally friendly energy storage devices.
The application status of supercapacitor in the world
In the 1980s, Japan’s NEC Company produced supercapacitor for the starting system of electric vehicles. At the same time, Panasonic developed a supercapacitor with activated carbon as the electrode material and organic solvent as the electrolyte, which opened the large-scale application of supercapacitor.
Today, Japan’s Panasonic, Elna, Nec-Tokin, South Korea’s Ness, Korchip, Nuintek, Russia’s Econd and Elit, and the United States’ Maxwell and Tecate occupy a large share of the international supercapacitor market. The development of supercapacitor batteries in China started late, but it has achieved rapid development and the market size has also grown rapidly.
At present, the main manufacturers of supercapacitor in China are Beijing Hezhong Huineng, Beijing Jixing, Shanghai Aowei, Dongguang Technology, CRRC Zhuzhou Electric Locomotive, Jinzhou Kaimei Energy and so on. Supercapacitor is widely used in many fields such as transportation and transportation, national defense and military, computer and memory, industry, power energy, and daily applications.
Supercapacitor have been widely used in the automotive industry due to their fast charging and discharging speed, high power density, and long cycle life. For conventional gasoline vehicles, supercapacitor connected to the internal combustion engine can provide an instant burst of energy that allows the car to start quickly.
The supercapacitor has a wide operating temperature range and good low temperature performance. The application of supercapacitor as an emergency starting power device can solve the problem that the battery is difficult to start the car in a low temperature environment.
The power system has a wide distribution range and a complex environment. Most of the renewable energy sources are greatly restricted by the environment, and the output power has obvious randomness and volatility. Supercapacitor batteries have the advantages of fast charging and discharging speed, high power density, and less influence by ambient temperature, so they are very suitable for energy storage devices in power systems.
In order to improve the power quality provided by the power system, a supercapacitor energy storage device and energy storage BMS are required to be used in power supply network. Energy storage BMS is widely used in energy storage battery nowadays, and we can have a clear look of the top 10 energy storage BMS manufacturers in China to know get the relevant knowledge deeply.
When the DC bus current is disturbed and fluctuates, the super capacitor can absorb the peak power of the bus ripple to adjust the output of active and reactive power, and improve the stability and reliability of the system.
Due to the influence of the environment during the working process of solar cells, the output has obvious nonlinear characteristics. According to the working characteristics of solar cells, the maximum power point tracking technology (MPPT) is usually used to keep the output power at the maximum value.
The energy storage system in traditional MPPT is mainly lead-acid battery, but the energy storage system designed with supercapacitor can obtain better dynamic characteristics, higher energy conversion efficiency and system service life.
The hybrid energy storage photovoltaic power generation system composed of supercapacitor and batteries uses the supercapacitor with high power density to quickly smooth the high-frequency fluctuation components of the DC bus power, prolonging the service life of the batteries, and at the same time taking advantage of the large capacity of lead-acid batteries.
With the accelerating process of industrial modernization, the volume of industrial production is getting larger and larger, which brings a lot of energy waste. In order to improve economic efficiency and save energy, these energy needs to be recovered and reused. At present, the technology of feeding back the power grid is not mature, and it will pollute the power grid. Therefore, the use of supercapacitor as energy storage devices is a more common method.
Daily application areas
Supercapacitor batteries can be used as backup energy storage devices for short-term power outages in portable electronic devices, and can meet the functions of hot swapping, data storage and transmission. Tecate Group’s supercapacitor power portable audio players, setup boxes, remote controls, rechargeable flashlights, and also provide short-term power for GPS devices, allowing devices to be hot-swapped.
Problems existing in the application of supercapacitor
With its own unique advantages, supercapacitor have been widely used in all walks of life. However, as an emerging energy storage element, supercapacitor still have problems that need to be solved and improved in their applications.
Low energy density limits the scope of application
Due to the low rated voltage and low energy density of supercapacitor batteries, the energy that they can store is relatively limited. With the continuous development of supercapacitor, improvements in the manufacturing process and technology of supercapacitor has gradually reduced their energy storage capacity.
A more effective method is to iteratively update the core constituent materials of supercapacitor, continuously develop new electrode materials, electrolyte materials, or use a hybrid supercapacitor composed of two different electrode materials. In addition, integrated systems consisting of batteries and supercapacitor have also achieved great success.
Inconsistent cell voltages in supercapacitor
Another big problem faced by supercapacitor batteries is inconsistent cell voltage. The energy density and rated voltage of the supercapacitor are low, and the cell voltage cannot meet the system voltage requirements.
Therefore, it is usually necessary to connect the supercapacitor in series and parallel to form a supercapacitor group. However, there are differences in the performance of supercapacitor, which will lead to inconsistencies in the terminal voltage of supercapacitor during series use.
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