1. Basic concepts and differences

Double electric layer capacitor (EDC) is a new type of energy storage device based on the principle of electrochemical double electric layer. When the electrode material of a double-layer capacitor is immersed in the electrolyte and a voltage is applied, a very thin charge separation area, the double electric layer, is formed at the electrode/electrolyte interface, thus storing electrical energy. This capacitor has a very high specific power and a long cycle life, can be charged and discharged quickly in a short time, but its energy density is relatively low.

Supercapacitors are another expression used to describe electrochemical capacitors with high energy density. It is also often referred to as electrochemical capacitors, gold capacitors, farrah capacitors, etc. Supercapacitors combine the high power characteristics of conventional capacitors with the energy storage capabilities of batteries, without the chemical reactions that occur in conventional batteries, instead relying on the double-layer mechanism and, in some types, the pseudo-capacitance effect to store electrical energy. The characteristics of supercapacitors include rapid charge and discharge capability in a short time, long life, wide operating temperature range and environmental protection.

Are double layer capacitors the same as supercapacitors?

Double electric layer capacitor is actually a kind of supercapacitor, and the two are essentially the same thing. Supercapacitor is a general term, which includes double electric layer capacitors (EDLC) and pseudocapacitive supercapacitors. Double layer capacitors mainly store energy based on the electrochemical double layer principle, while the pseudo-capacitor type involves the rapid REDOX reaction of the surface. Therefore, when referring to "supercapacitors", we usually also cover the concept of double electric layer capacitors.

What are the main differences between supercapacitors and conventional capacitors?

Traditional capacitors store electrostatic energy through dielectric, with small capacity, which is suitable for high-frequency filtering, coupling and other applications. In contrast, supercapacitors use the double layer effect at the electrode/electrolyte interface and/or the pseudo-capacitance effect to store large amounts of energy, have ultra-high capacity, and can charge and discharge quickly, but the voltage is generally low. The fundamental differences in their energy storage mechanisms make supercapacitors far superior to traditional capacitors in energy density and power density.

What are the differences between lithium-ion supercapacitors and EDLC?

Lithium-ion supercapacitors combine the high energy density of lithium-ion batteries with the high power density of EDLCs. Unlike EDLC, which mainly rely on double layers for energy storage, lithium-ion supercapacitors store more energy through the insertion/removal process of lithium ions (pseudocapacitance mechanism). This means that although the charge and discharge speed of lithium-ion supercapacitors is slightly slower than that of EDLCs, their energy density is significantly improved, which is suitable for application scenarios requiring higher energy storage and longer battery life.

2. How it works

How do double layer capacitors store and release energy?

In double-layer capacitors, when a voltage is applied, the positive and negative ions in the electrolyte move towards the electrode respectively, forming a tightly arranged double-layer structure at the electrode/electrolyte interface, thus storing charge. When discharged, these ions return to their original position, releasing energy. There is almost no chemical reaction in the whole process, which ensures fast charge-discharge characteristics.

How does a supercapacitor work? Why can fast charge and discharge be achieved?

The working principle of supercapacitors is based on electrochemical double layers and/or pseudocapacitance effects. The double layer energy storage is fast and reversible, and does not involve chemical reactions, so it can achieve rapid charge and discharge within seconds to minutes. The pseudo-capacitance effect stores more energy through a rapid electrochemical reaction, and together, supercapacitors show excellent power performance.

3. Performance parameters

What is the capacity range of supercapacitors? What is the maximum number of farads?

Supercapacitors have a wide range of capacities, ranging from less than 1 farad to thousands of farads, with hundreds to thousands of farads common in industrial applications. With the advancement of technology, there have been studies reporting the capacity of supercapacitor cells in excess of millions of farads, although such high-capacity products have not yet been commercialized on a large scale.

What is the energy density and power density of supercapacitors?

The energy density of supercapacitors is usually 5-30 Wh/kg, while the power density can be as high as 10,000 W/kg, which is much higher than traditional batteries, but lower than the energy density of lithium batteries. This characteristic makes them ideal for applications that require fast charge and discharge and high power output.

What is the charge-discharge cycle and cycle life of supercapacitors?

Supercapacitors support hundreds of thousands or even millions of charge and discharge cycles, far more than the hundreds to thousands of traditional batteries. This is due to its non-destructive energy storage mechanism, which ensures long-term stability and long life.

4. Compare pros and cons

What are the advantages and disadvantages of supercapacitors compared to batteries?

The advantages of supercapacitors compared with batteries mainly include:

1. High power density: Supercapacitors are able to provide or absorb large amounts of electrical energy in a short period of time with a higher power density than traditional batteries, making them suitable for applications requiring instantaneous high power output.

2. Fast charge and discharge capability: The charge and discharge speed of supercapacitors is extremely fast, usually in a few minutes to complete the charge, far faster than the traditional battery charging time of several hours, suitable for frequent fast charge application scenarios.

3. Long cycle life: Supercapacitors can carry out hundreds of thousands or even millions of charge and discharge cycles, while traditional batteries usually can only carry out thousands to 10,000 times, which greatly reduces the replacement frequency and maintenance costs.

4. High reliability and durability: Because the charge and discharge process does not involve chemical reactions, the performance of supercapacitors is more stable at extreme temperatures, and the applicable operating temperature range is wider, ranging from -40 ° C to 70 ° C.

5. Environmentally friendly: It is usually made of non-harmful materials, and the production and use process has little impact on the environment, which is a green energy storage technology.

6. High safety: In the case of overheating, supercapacitors are more likely to behave as circuit disconnection rather than explosion, increasing the safety of use.

The main disadvantages of supercapacitors are:

1. Lower energy density: Compared to batteries, supercapacitors store less energy for the same volume or weight, which limits their use in applications that require high energy density, such as the main driving force source for electric vehicles.

2. Single low voltage: The voltage of a single supercapacitor is low, and in order to achieve the output voltage equivalent to the battery, multiple capacitors are often required to be used in series, which may lead to increased system design complexity and cost.

3. Higher cost: Currently, supercapacitors cost more per unit of energy storage than traditional batteries, although this gap is narrowing with technological advances and mass production.

What are the limitations or challenges of using supercapacitors?

Cost, energy density and voltage drop issues are currently the main challenges. In order to expand the application range, reducing production cost, increasing energy density and developing high-voltage supercapacitors have become research hotspots.

5. Selection and design

How to choose the right supercapacitor model for your specific needs?

The selection should take into account the power requirements of the application, operating voltage, amount of energy required, working environment and life expectancy. At the same time, cost budget is also an important factor.

How to calculate the capacity of the supercapacitor? What are the key parameters involved?

The capacity calculation of supercapacitors usually involves rated voltage, electrode area, electrolyte type and thickness. The formula is roughly C = ε·A/d, where C is the capacity, ε is the dielectric constant, A is the electrode area, and d is the thickness of the dielectric. In practical application, the technical parameters provided by the manufacturer should also be referred to.

6. Application field

In what fields are supercapacitors widely used?

Because of their unique performance, supercapacitors are widely used in automotive (especially hybrid and start-stop systems), wind power generation (energy buffering), public transportation (such as braking energy recovery for electric buses), and power grid energy storage (stabilizing power quality).

Specific application cases of double electric layer capacitor in consumer electronics and industrial equipment

In consumer electronics, double-layer capacitors are used to hold RAM data and provide temporary power supply during battery replacement. In industrial equipment, such as UPS systems, smart meters and automatic control devices, they provide instantaneous high power output to ensure smooth operation of equipment in the event of power failure.

7. Maintenance and security

What safety matters should be paid attention to during the use of supercapacitors?

In the process of using supercapacitors, the following safety matters need to be paid attention to to ensure the safety of operation and extend the life of capacitors:

1. Confirm polarity: Supercapacitors have fixed polarity, and the positive and negative poles must be confirmed before use, and wrong connections can lead to capacitor damage or even explosion.

2. Comply with the nominal voltage: ensure that the capacitor works within the nominal voltage range, overvoltage use will lead to electrolyte decomposition, heating, capacity reduction and internal resistance increase, serious will shorten the life or cause accidents.

3. Prevent over-charge and over-discharge: Implement appropriate management measures, such as using chargers with appropriate protection circuits to avoid over-charge and discharge of capacitors.

4. Balance when used in series: If supercapacitors need to be used in series to increase the voltage, a voltage balancing circuit must be added to prevent overvoltage damage to individual units.

5. Avoid high frequency charge and discharge: Supercapacitors are not suitable for use in circuits that require high frequency charge and discharge, so as to avoid internal heating, capacity attenuation and internal resistance increase.

6. Reasonable installation and fixing: When installing the supercapacitor, avoid forced tilt or twisting to prevent performance deterioration caused by loose leads, and ensure that the capacitor is firmly fixed.

7. Environmental requirements: Storage and working environment should be kept dry, ventilated, stable temperature, avoid extreme temperature and humidity conditions, to prevent damage to internal materials.

8. Safety isolation and insulation: Appropriate isolation and insulation measures should be used in the design of the system to prevent the risk of electric shock, especially in high voltage applications.

9. Regular maintenance and testing: Although called "maintenance-free", regular inspection of capacitor status, such as monitoring voltage, temperature and appearance, can detect potential faults in time.

10. Use appropriate tools and equipment: When installing, disassembling and testing capacitors, use appropriate insulation tools and protective equipment and follow safe operating procedures.

Following these safety and operation guidelines can effectively improve the safety of supercapacitors during use, ensure the safety of personnel and the stable operation of the system.

How to properly maintain supercapacitors to extend their service life?

Regularly check that the operating voltage and temperature are within the specified range, keep it clean, avoid long periods of full load operation, implement regular charge and discharge cycles to maintain optimal performance, and store it as recommended by the manufacturer when not in use for long periods of time. Through these measures, the service life of supercapacitors can be effectively extended.

8. Development trends and prospects

What are the latest developments and future trends in supercapacitor technology?

Current research focuses on the development of new materials (such as two-dimensional materials, nano-carbon materials), increasing energy density, widening the operating temperature range, and modular and intelligent design to meet the needs of more application scenarios.

Market Analysis: What is the current state and growth potential of the supercapacitor industry?

The global supercapacitor market continues to grow, benefiting from the rapid development of new energy vehicles, smart grid, Internet of Things and other fields. The market is expected to experience explosive growth in the next few years with technological breakthroughs and cost reductions.