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

An ionistor is a double-layer electrochemical capacitor or supercapacitor. Their metal electrodes are coated with very 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 holds the electrodes away from each other, when wound around 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 an ionistor as a power source.

Principle of operation

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

Design Advantage:

1. Provides capacity in a small device, there is no need for special charging circuits for monitoring during discharge in devices where an ionistor is used.
2. Overcharging or overly frequent discharging does not adversely affect battery life, as with typical batteries.
3. The technology is extremely “clean” from an environmental point of view.
4. There are no problems with unstable contacts, so with ordinary batteries.

Design disadvantages:

1. Duration of operation is limited due to the use of electrolyte in devices where an ionistor is used.
2. Electrolyte may leak if the capacitor is not used correctly.
3. Compared to aluminum capacitors, these ionistors have high resistances and therefore cannot be used in AC circuits.

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

1. Memory backup 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 equipment using solar cells, such as clocks and indicators.
5. Starters for small and mobile engines.

Redox reactions

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

Due to the redox reaction occurring in this type, there is a potential with a lower power density than EDLC, since Faradaic systems are slower than non-parasitic systems. As a rule, pseudo-captors provide a higher specific capacitance and energy density than EDLC, due to the fact that they belong to the faradeite system. However, the proper choice of supercapacitor depends on the application and availability.

Graphene based materials

The ionistor is characterized by the ability to quickly charge, much faster than that of a traditional battery, but it is not able to store as much energy as a battery, since it has a lower energy density. They increase their efficiency through the use of graphene and carbon nanotubes. They will help in the future, ionistors completely displace electrochemical batteries. Nanotechnology today is the source of many innovations, especially in the e-mobile.

Graphene increases the capacity of ionistors. 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 various classifications of high-capacity ionistors:

1. Electrochemical two-layer capacitors (EDLCs), which for the most part use high-carbon carbon electrodes and retain their energy due to the rapid adsorption of ions at the electrode / electrolyte interface.
2. Psuedo capacitors are based on a phagadic charge transfer process on or near the surface of an electrode. In this case, conductive polymers and transition metal oxides remain electrochemical active materials, for example, as in electronic clocks on batteries.

Flexible polymer based devices

The ionistor gains and stores energy at a high speed, forming electrochemical double layers of charges or through surface redox reactions, which leads to a high power density with long cyclic stability, low cost and environmental protection. PDMS and PET are mainly used substrates in the implementation of flexible supercapacitors. In the case of a film, PDMS can create flexible and transparent thin-film ionistors in watches with high cyclic stability after 10,000 bending cycles.

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

Natural polymers, such as non-woven materials from wood fibers and paper, can also be used as substrates that are flexible and light. CNTs are applied to paper to produce a flexible CNT paper electrode. Due to the high flexibility of the paper substrate and the good distribution of CNTs, the specific capacity and density of power and energy change by less than 5% after bending for 100 cycles with a bending radius of 4.5 mm. In addition, due to their higher mechanical strength and better chemical stability, bacterial nanocellulose papers are also used to make flexible supercapacitors, for example, a walkman cassette player.

Super Capacitor Performance

It is determined from the point of view of electrochemical activity and chemical kinetic properties, namely: electronic and ionic kinetics (transportation) inside the electrodes and the efficiency of the charge transfer rate to the electrode / electrolyte. For high performance when using carbon-based materials with EDLC, specific surface area, electrical conductivity, pore size and differences are important. Graphene with its high electrical conductivity, large surface area and interlayer structure is attractive for use in EDLC.

In the case of pseudo-capacitors, although they provide superior capacitance over EDLC, they are still limited by the densities of the low-power kmop chip. This is due to poor electrical conductivity, limiting the rapid electronic motion. In addition, the redox process that drives the charge / discharge process can damage electroactive materials. The high electrical conductivity of graphene and its excellent mechanical strength make it suitable as a material in pseudo-capacitors.

Studies of adsorption on graphene have shown that it occurs mainly on the surface of graphene sheets with access to large pores (i.e., the interlayer structure is porous, providing easy access to electrolyte ions). Thus, for best performance, pore-free agglomeration should be avoided. Performance can be further improved by modifying the surface by attaching functional groups, hybridizing with electrically conductive polymers and by forming graphene / metal oxide composites.

Capacitor comparison

Ionistors are ideal when fast charging is required to meet short-term power needs. The hybrid battery satisfies both needs and reduces voltage, which ensures a longer battery life. The table below compares the characteristics and basic materials in capacitors.

Charge characteristic

Charge time 1-10 seconds. The initial charge can be performed very quickly, and the charge of the upper part will take additional time. It is necessary to provide for inrush current limitation when charging an empty supercapacitor, since it will draw out everything possible. The ionistor cannot be recharged and does not require detection of a full charge, the current simply stops flowing when it is full. Performance comparison between a car ionist and a Li-ion.

Benefits of Charging Devices

Vehicles need an extra energy spurt to accelerate, and this is exactly what ionistors are suitable for. They have a total charge limitation, but they are able to transfer it very quickly, which makes them ideal batteries. Their advantages in relation to traditional batteries:

1. Low impedance (ESR) increases surge current and load when connected in parallel with the battery.
2. Very high cycle - discharge takes milliseconds up to several minutes.
3. Voltage drop compared to a battery operated device without a supercapacitor.
4. High efficiency at 97-98%, and the efficiency of DC-DC in both directions is 80% -95% in most applications, for example, a DVR with ionistors.
5. In a hybrid electric vehicle, circular efficiency is 10% greater than that of a battery.
6. It works well in a very wide temperature range, usually from -40 C to + 70 C, but can be from -50 C to + 85 C, there are special versions reaching 125 C.
7. A small amount of heat generated during charging and discharging.
8. Long cycle life with high reliability, which reduces maintenance costs.
9. Slight degradation over hundreds of thousands of cycles and lasts 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. Not subject to wear and aging.
12. Does not affect deep discharges, unlike batteries.
13. Increased safety compared to batteries - there is no danger of overcharging or exploding.
14. At the end of operation does not contain hazardous materials for disposal, unlike many batteries.
15. It complies with environmental standards, so there is no complicated disposal or recycling.

Containment 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 period of time, but nevertheless, there are certain unresolved problems that hinder technical progress in this direction. Disadvantages of an ionistor before rechargeable batteries:

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

Hybrid storage system

The special design and embedded power electronics technologies have been developed to produce new structure ionistor modules. 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 loss and the size of energy balancing schemes in energy storage and device systems.

A series of related technologies have also been developed, such as charge and discharge control, as well as connections to other energy storage systems. An ionistor module with a nominal capacity of 150F, a rated voltage of 50 V can be placed on flat and curved surfaces with a surface area of ​​0.5 sq. m and a thickness of 4 cm. The application is applicable to electric vehicles and can be integrated with various parts of the vehicle and in other cases where energy storage systems are required.

Application and Prospects

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

Now it’s obvious that ionistors will bury lead-acid batteries over the next few years, but this is only part of the story, as their parameters improve faster than competition. Suppliers such as Elbit Systems, Graphene Energy, Nanotech Instruments, and Skeleton Technologies have stated that they exceed the energy density of lead-acid batteries with their supercapacitors and superbacteria, some of which theoretically correspond to the energy density of lithium ions.

Nevertheless, the ionistor in an electric car is one of the aspects of electronics and electrical engineering that is ignored by the press, investors, potential suppliers and many people living with old technologies, despite the rapidly growing multi-billion dollar market. For example, for ground, water, and airborne vehicles, there are about 200 major manufacturers of traction motors and 110 major suppliers of traction batteries compared to several manufacturers of supercapacitors. 66 , .