Where is the ionistor used? Types of ionistors, their purpose, advantages and disadvantages

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Where is the ionistor used? Types of ionistors, their purpose, advantages and disadvantages
Where is the ionistor used? Types of ionistors, their purpose, advantages and disadvantages
Anonim

Ionistor are double layer electrochemical capacitors or supercapacitors. Their metal electrodes are coated with highly porous activated carbon, traditionally made from coconut shells, but most often from carbon airgel, other nanocarbon or graphene nanotubes. Between these electrodes is a porous separator that keeps the electrodes apart, when wound on a spiral, all this is impregnated with electrolyte. Some innovative forms of ionistor have a solid electrolyte. They replace traditional batteries in uninterruptible power supplies up to trucks, where they use a supercharger as a power source.

Working principle

Principle of operation
Principle of operation

The ionistor uses the action of a double layer formed at the interface between coal and electrolyte. Activated carbon is used as an electrode in solid form, and electrolyte in liquid form. When these materials are in contact with each other, the positive and negative poles are distributed relative to each other byvery short distance. When applying an electric field, the electrical double layer that forms near the surface of the carbon in the electrolytic liquid is used as the main structure.

Design advantage:

  1. Provides capacitance in a small device, no need for special charging circuits to control during discharging in supercharged devices.
  2. Recharging or over-discharging does not adversely affect battery life as with typical batteries.
  3. Technology is extremely "clean" in terms of ecology.
  4. No problems with unstable contacts like normal batteries.

Design flaws:

  1. The duration of operation is limited due to the use of electrolyte in devices that use a supercapacitor.
  2. Electrolyte may leak if the capacitor is not properly maintained.
  3. Compared to aluminum capacitors, these capacitors have high resistance and therefore cannot be used in AC circuits.

Using the advantages described above, electric capacitors are widely used in applications such as:

  1. Reserving memory for timers, programs, e-mobile power, etc.
  2. Video and audio equipment.
  3. Backup sources when replacing batteries for portable electronic equipment.
  4. Power supplies for solar powered equipment such as clocks and indicators.
  5. Starters for small and mobile engines.

Redox reactions

Redox reactions
Redox reactions

The charge accumulator is located at the interface between the electrode and the electrolyte. During the charging process, electrons move from the negative electrode to the positive electrode along the outer circuit. During discharge, electrons and ions move in the opposite direction. There is no charge transfer in an EDLC supercapacitor. In this type of supercapacitor, a redox reaction occurs at the electrode, which generates charges and carries the charge through the double layers of the construction, where an ionistor is used.

Due to the redox reaction that occurs in this type, there is a potential for lower power density than EDLC because Faradaic systems are slower than non-faradaic systems. As a general rule, pseudocapactors provide higher specific capacitance and energy density than EDLCs due to the fact that they are of the faraday system. However, the correct choice of supercapacitor depends on the application and availability.

Graphene-based materials

Graphene based materials
Graphene based materials

The supercapacitor is characterized by the ability to quickly charge, much faster than a traditional battery, but it is not able to store as much energy as a battery because it has a lower energy density. Their efficiency increase is achieved through the use of graphene and carbon nanotubes. In the future, they will help ionistors to completely replace electrochemical batteries. Nanotechnology today is the source of manyinnovations, especially in e-mobile.

Graphene increases the capacitance of supercapacitors. This revolutionary material consists of sheets whose thickness can be limited by the thickness of the carbon atom and whose atomic structure is ultra-dense. Such characteristics can replace silicon in electronics. A porous separator is placed between two electrodes. However, variations in the storage mechanism and the choice of electrode material lead to different classifications of high-capacity supercapacitors:

  1. Electrochemical Double Layer Capacitors (EDLC), which mostly use high carbon carbon electrodes and store their energy by rapidly adsorbing ions at the electrode/electrolyte interface.
  2. Psuedo-capacitors are based on the phagic process of charge transfer at or near the electrode surface. In this case, conductive polymers and transition metal oxides remain electrochemically active materials, such as those found in battery-operated electronic watches.

Flexible polymer devices

Flexible devices based on polymers
Flexible devices based on polymers

The supercapacitor gains and stores energy at a high rate by forming electrochemical charge double layers or through surface redox reactions, resulting in high power density with long-term cyclic stability, low cost and environmental protection. PDMS and PET are the most commonly used substrates in the implementation of flexible supercapacitors. In the case of film, PDMS can create flexible andtransparent thin film ionistors in watches with high cyclic stability after 10,000 flex cycles.

Single-walled carbon nanotubes can be further incorporated into the PDMS film to further improve mechanical, electronic and thermal stability. Similarly, conductive materials such as graphene and CNTs are also coated with PET film to achieve both high flexibility and electrical conductivity. In addition to PDMS and PET, other polymeric materials are also attracting growing interest and are synthesized by various methods. For example, localized pulsed laser irradiation has been used to quickly transform the primary surface into an electrically conductive porous carbon structure with specified graphics.

Natural polymers such as wood fiber and paper nonwovens can also be used as substrates, which are flexible and lightweight. The CNT is deposited on paper to form a flexible CNT paper electrode. Due to the high flexibility of the paper substrate and the good distribution of CNTs, the specific capacitance and power and energy density change by less than 5% after bending for 100 cycles at a bend radius of 4.5 mm. In addition, due to higher mechanical strength and better chemical stability, bacterial nanocellulose papers are also being used to make flexible supercapacitors such as the walkman cassette player.

Supercapacitor performance

Performance of supercapacitors
Performance of supercapacitors

It is defined in terms ofelectrochemical activity and chemical kinetic properties, namely: electron and ion kinetics (transportation) inside the electrodes and the efficiency of the rate of charge transfer to the electrode/electrolyte. Specific surface area, electrical conductivity, pore size and differences are important for high performance when using EDLC based carbon materials. Graphene, with its high electrical conductivity, large surface area and interlayer structure, is attractive for use in EDLC.

In the case of pseudocapacitors, although they provide superior capacitance compared to EDLCs, they are still limited in density by the low power of the CMOS chip. This is due to poor electrical conductivity, which limits fast electronic motion. In addition, the redox process that drives the charge/discharge process can damage electroactive materials. Graphene's high electrical conductivity and excellent mechanical strength make it suitable as a material in pseudocapacitors.

Studies of adsorption on graphene have shown that it occurs mainly on the surface of graphene sheets with access to large pores (ie, the interlayer structure is porous, allowing easy access to electrolyte ions). Thus, non-porous graphene agglomeration should be avoided for better performance. Performance can be further improved by surface modification by functional group addition, hybridization with electrically conductive polymers, and by formation of graphene/oxide compositesmetal.

Capacitor comparison

Comparison of capacitors
Comparison of capacitors

Supercaps are ideal when fast charging is required to meet short-term power needs. The hybrid battery satisfies both needs and lowers the voltage for longer life. The table below shows the comparison of characteristics and main materials in capacitors.

Electric double-layer capacitor, ionistor designation Aluminum electrolytic capacitor Ni-cd battery Lead sealed battery
Use temperature range -25 to 70°C -55 to 125 °C -20 to 60 °C -40 to 60 °C
Electrodes Activated carbon Aluminum (+) NiOOH (-) Cd

(+) PbO2 (-) Pb

Electrolytic liquid Organic solvent Organic solvent KOH

H2SO4

Electromotive force method Using natural electrical double layer effect as dielectric Using aluminum oxide as a dielectric Using a chemical reaction Using a chemical reaction
Pollution No No CD Pb
Number of charge/discharge cycles > 100,000 times > 100,000 times 500 times 200 to 1000 times
Capacity per volume unit 1 1/1000 100 100

Charge characteristic

Charge time 1-10 seconds. The initial charge can be completed very quickly and the top charge will take extra time. Consideration should be given to limiting the inrush current when charging an empty supercapacitor, as it will draw as much as possible. The supercapacitor is not rechargeable and does not require full charge detection, the current simply stops flowing when full. Performance comparison between supercharger for car and Li-ion.

Function Ionistor Li-Ion (general)
Charging time 1-10 seconds 10-60 minutes
Watch life cycle 1 million or 30,000 500 and up
Voltage From 2, 3 to 2, 75B 3, 6 B
Specific energy (W/kg) 5 (typical) 120-240
Specific power (W/kg) Up to 10000 1000-3000
Cost per kWh $10,000 250-1,000 $
Lifetime 10-15 years 5 to 10 years old
Charging temperature -40 to 65°C 0 to 45 °C
Discharge temperature -40 to 65°C -20 to 60°C

Benefits of charging devices

Vehicles need an extra energy boost to accelerate, and that's where superchargers come in. They have a limit on the total charge, but they are able to transfer it very quickly, making them ideal batteries. Their advantages over traditional batteries:

  1. Low impedance (ESR) increases surge current and load when connected in parallel with battery.
  2. Very high cycle - discharge takes milliseconds to minutes.
  3. Voltage drop compared to battery powered device without supercapacitor.
  4. High efficiency at 97-98%, and DC-DC efficiency in both directions is 80%-95% in most applications, such asvideo recorder with ionistors.
  5. In a hybrid electric vehicle, roundabout efficiency is 10% greater than that of a battery.
  6. Works well over a very wide temperature range, typically -40 C to +70 C, but can be from -50 C to +85 C, special versions available up to 125 C.
  7. Small amount of heat generated during charging and discharging.
  8. Long cycle life with high reliability, reducing maintenance costs.
  9. Slight degradation over hundreds of thousands of cycles and lasting up to 20 million cycles.
  10. They lose no more than 20% of their capacity after 10 years, and life expectancy is 20 years or more.
  11. Resistant to wear and tear.
  12. Does not affect deep discharges like batteries.
  13. Increased safety compared to batteries - no danger of overcharging or explosion.
  14. Contains no hazardous materials to dispose of at end-of-life unlike many batteries.
  15. Complies with environmental standards, so there is no complicated disposal or recycling.

Restraint Technology

The supercapacitor consists of two layers of graphene with an electrolyte layer in the middle. The film is strong, extremely thin and capable of releasing a large amount of energy in a short amount of time, but nevertheless, there are certain unresolved problems that are holding back technological progress in this direction. Disadvantages of Supercapacitor over Rechargeable Batteries:

  1. Low energy density - usuallytakes from 1/5 to 1/10 of the energy of an electrochemical battery.
  2. Line discharge - failure to use the full energy spectrum, depending on the application, not all energy is available.
  3. As with batteries, cells are low voltage, serial connections and voltage balancing are required.
  4. Self-discharge is often higher than batteries.
  5. Voltage varies with stored energy - efficient storage and recovery of energy requires sophisticated electronic control and switching equipment.
  6. Has the highest dielectric absorption of all types of capacitors.
  7. The upper use temperature is usually 70 C or less and rarely exceeds 85 C.
  8. Most contain a liquid electrolyte that reduces the size needed to prevent inadvertent rapid discharge.
  9. High cost of electricity per watt.

Hybrid Storage

Special design and embedded technology of power electronics have been developed to produce capacitor modules with new structure. Since their modules must be manufactured using new technologies, they can be integrated into car body panels such as the roof, doors and trunk lid. In addition, new energy balancing technologies have been invented that reduce energy losses and the size of energy balancing circuits in energy storage and device systems.

A series of related technologies have also been developed, such as charging control anddischarging, as well as connections to other energy storage systems. A supercapacitor module with a rated capacity of 150F, a rated voltage of 50V can be placed on flat and curved surfaces with a surface area of 0.5 square meters. m and 4 cm thick. Applications applicable to electric vehicles and can be integrated with various parts of the vehicle and other cases where energy storage systems are required.

Application and perspectives

Application and prospects
Application and prospects

In the USA, Russia and China there are buses without traction batteries, all work is done by ionistors. General Electric has developed a pickup truck with a supercapacitor to replace the battery, similar to what has happened in some rockets, toys and power tools. Tests have shown that supercapacitors outperform lead-acid batteries in wind turbines, which was achieved without supercapacitor energy density approaching that of lead-acid batteries.

It's now clear that supercapacitors will bury lead-acid batteries over the next few years, but that's only part of the story, as they're improving faster than the competition. Suppliers such as Elbit Systems, Graphene Energy, Nanotech Instruments and Skeleton Technologies have said they exceed the energy density of lead-acid batteries with their supercapacitors and superbugs, some of which theoretically match the energy density of lithium ions.

However, the ionistor in an electric vehicle is one of the aspects of electronics and electrical engineering thatignored by the press, investors, potential suppliers, and many people who live with old technology, despite the rapid growth of the multi-billion dollar market. For example, for land, water and air vehicles, there are about 200 major manufacturers of traction motors and 110 major suppliers of traction batteries compared to a few manufacturers of supercapacitors. In general, there are no more than 66 large manufacturers of ionistors in the world, most of which have focused their production on lighter models for consumer electronics.

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