A supercapacitor or ionistor is a device for storing energy masses; charge accumulation occurs at the boundary between the electrode and the electrolyte. The useful energy volume is stored as a static type charge. The accumulation process comes down to interaction with a constant voltage when the ionistor receives a potential difference across its plates. Technological implementation, as well as the very idea of creating such devices, appeared relatively recently, but they managed to receive experimental use to solve a certain number of problems. The part can replace current sources of chemical origin, being a backup or the main means of power supply in watches, calculators, and various microcircuits.
The elementary design of a capacitor consists of a plate, the material for which is foil, delimited by a dry separating substance. The ionistor consists of a number of capacitors with an electrochemical type charger. Special electrolytes are used for its production. Coverings can be of several varieties. Activated carbon is used for the manufacture of large-scale linings. Metal oxides and polymer materials with high conductivity can also be used. To achieve the required capacitive density, it is recommended to use highly porous carbon materials. In addition, this approach allows you to make an ionistor at an impressively low cost. Such parts belong to the category of DLC capacitors, which accumulate charge in a double compartment formed on the plate.
The design solution, when the ionistor is combined with a water electrolyte base, is characterized by low resistance of the internal elements, while the charge voltage is limited to 1 V. The use of organic conductors guarantees voltage levels of about 2...3 V and increased resistance.
Electronic circuits operate with higher energy demands. The solution to this problem is to increase the number of power points used. The ionistor is installed not just one, but in an amount of 3-4 pieces, giving the required amount of charge.
Compared to a nickel-metal hydride battery, the ionistor is capable of containing a tenth of the energy reserve, while its voltage drops linearly, excluding zones of planar discharge. These factors affect the ability to fully retain charge in the ionistor. The charge level directly depends on the technological purpose of the element.
Quite often, an ionistor is used to power memory chips and is included in filter circuits and smoothing filters. They can also be combined with batteries of various types to combat the consequences of sudden surges in current: when a low current is supplied, the ionistor is recharged, otherwise it releases part of the energy, thereby reducing the overall load.
A tablespoon of activated carbon from a pharmacy, a few drops of salted water, a tin plate and a plastic jar of photographic film. It's enough to do DIY ionistor, an electrical capacitor whose capacitance is approximately equal to the electrical capacitance ... of the globe. Leyden jar.
It is possible that one of the American newspapers wrote about just such a device in 1777: “... Dr. Franklin has invented a machine the size of a toothpick case, capable of turning London’s St. Paul’s Cathedral into a handful of ashes.” However, first things first.
Humanity has been using electricity for a little over two centuries, but electrical phenomena have been known to people for thousands of years and have not had practical significance for a long time. Only at the beginning of the 18th century, when science became a fashionable entertainment, did the German scientist Otto von Guericke create an “electrophoric” machine specifically for conducting public experiments, with the help of which he received electricity in previously unheard of quantities.
The machine consisted of a glass ball, against which a piece of leather rubbed as it rotated. The effect of her work was great: sparks crackled, invisible electrical forces tore off ladies' shawls and made hair stand on end. The public was especially surprised by the ability of bodies to accumulate electrical charges.
In 1745, the Dutch physicist from Leiden Pieter van Musschenbroek (1692 - 1761) poured water into a glass jar, put a piece of wire inside, like a flower in a vase, and, carefully clasping it with his palms, brought it to the electrophore machine. The bottle collected so much electricity that a bright spark flew out of the piece of wire with a “deafening roar.” The next time the scientist touched the wire with his finger, he received a blow from which he lost consciousness; If it weren’t for assistant Kuneus, who arrived in time, the matter could have ended sadly.
Thus, a device was created that could accumulate millions of times more charge than any body known at that time. It was called the "Leyden jar". It was a kind of capacitor, one of the plates of which was the experimenter’s palms, the dielectric was glass walls, and the second plate was water.
The news of the invention spread throughout enlightened Europe. The Leyden jar was immediately used to educate the French king Louis XV. The performances began. In one of the experiments that went down in history, an electric current was passed through a chain of guards holding hands. When the electric discharge hit, everyone jumped up as one, as if they were about to march in the air. In another experiment, current was passed through a chain of 700 monks...
Experiments with the Leyden jar in America took a more practical direction. In 1747, they were started by one of the founders of the United States, the already mentioned Benjamin Franklin. He came up with the idea of wrapping the jar in tin foil, and its capacity increased many times, and the work became safer. In experiments with it, Franklin proved that an electric discharge can generate heat and raise the mercury column in a thermometer. And by replacing the jar with a glass plate covered with tin foil, Franklin received a flat capacitor, many times lighter than even the Leyden jar he improved.
History is silent about a device capable of storing so much energy that, as the newspaper wrote, it could be used to “turn St. Paul’s Cathedral into a pile of ashes,” but this does not mean that B. Franklin could not create it.
And here is the time to return to how to do DIY ionistor. If you have stocked up on everything you need, lower the tin plate to the bottom of the film can, after soldering a piece of insulated wire to it. Place a filter paper pad on top, pour a layer of activated carbon on it and, after pouring salted water, cover your “sandwich” with another electrode.
Diagram of the ionistor operation.
You have got an electrochemical capacitor - ionistor. It is interesting because in the pores of activated carbon particles a so-called double electrical layer appears - two layers of electrical charges of different signs located close to each other, that is, a kind of electrochemical capacitor. The distance between layers is calculated in angstroms (1 angstrom - 10-9 m). And the capacitance of a capacitor, as is known, the greater the smaller the distance between the plates.
Due to this, the energy reserve per unit volume in the double layer is greater than that of the most powerful explosive. This Leyden jar!
The ionistor works as follows. In the absence of external voltage, its capacity is negligible. But under the influence of voltage applied to the poles of the capacitor, the adjacent layers of coal are charged. Ions of the opposite sign in the solution rush to the coal particles and form a double electrical layer on their surface.
Industrial electrochemical capacitor (ionistor). The button-sized metal casing houses two layers of activated carbon, separated by a porous gasket.
Scheme how to do it DIY ionistor.
Diagram of a homemade ionistor made from a plastic jar and activated carbon:
1 - upper electrode;
2 - connecting wires;
3.5 - layers of wet activated carbon;
4 - porous separating gasket;
6 - bottom electrode;
7 - body.
If a load is connected to the poles of the capacitor, then opposite charges from the inner surface of the coal particles will run along the wires towards each other, and the ions located in their pores will come out.
That's all. now you understand how to do it DIY ionistor.
Modern ionistors have a capacity of tens and hundreds of farads. When discharged, they are capable of developing great power and are very durable. In terms of energy reserve per unit mass and unit volume, ionistors are still inferior to batteries. But if you replace activated carbon with the thinnest carbon nanotubes or other electrically conductive substance, the energy intensity of the ionistor can become fantastically large.
Benjamin Franklin lived in a time when nanotechnology was not even thought about, but this does not mean that it was not used. As Nobel Prize winner in chemistry Robert Curie reported, when making blades from Damascus steel, ancient craftsmen, without knowing it, used nanotechnology methods. Ancient damask steel always remained sharp and durable thanks to the special composition of carbon in the metal structure.
Some kind of nanomaterials, such as charred plant stems containing nanotubes, could be used by Franklin to create a supercapacitor. How many of you understand what it is? Leyden jar, and who will try to do it?
The requirement to reduce the size of radio components while increasing their technical characteristics led to the emergence of a large number of devices that are used everywhere today. This fully affected capacitors. The so-called ionistors or supercapacitors are elements with a high capacity (the range of this indicator is quite wide from 0.01 to 30 farads) with a charging voltage of 3 to 30 volts. Moreover, their sizes are very small. And since the subject of our conversation is a do-it-yourself ionistor, it is necessary first of all to understand the element itself, that is, what it is.
Design features of the ionistor
In essence, this is an ordinary capacitor with a large capacity. But ionistors have a high resistance, because the element is based on an electrolyte. This is the first. The second is the low charging voltage. The thing is that in this supercapacitor the plates are located very close to each other. This is precisely the reason for the reduced voltage, but it is precisely for this reason that the capacitance of the capacitor increases.
Factory ionizers are made from different materials. The covers are usually made of foil, which is separated by a dry substance with a separating effect. For example, activated carbon (for large plates), metal oxides, polymer substances that have high electrical conductivity.
Assembling the ionizer with your own hands
Assembling an ionizer with your own hands is not the easiest thing, but you can still do it at home. There are several designs where different materials are present. We offer one of them. To do this you will need:
- metal coffee jar (50 g);
- activated carbon, which is sold in pharmacies, can be replaced with crushed carbon electrodes;
- two circles of copper plate;
- cotton wool
First of all, you need to prepare the electrolyte. To do this, you first need to crush the activated carbon into powder. Then make a saline solution, for which you need to add 25 g of salt to 100 g of water, and mix it all well. Next, activated carbon powder is gradually added to the solution. Its quantity is determined by the consistency of the electrolyte; it should be as thick as putty.
After which the finished electrolyte is applied to copper circles (on one side). Please note that the thicker the electrolyte layer, the greater the capacity of the ionistor. And one more thing, the thickness of the applied electrolyte on the two circles should be the same. So, the electrodes are ready, now they need to be separated by a material that would pass electric current, but would not allow carbon powder to pass through. For this, ordinary cotton wool is used, although there are many options here. The thickness of the cotton layer determines the diameter of the metal coffee jar, that is, this entire electrode structure should fit comfortably into it. Hence, in principle, you will have to select the dimensions of the electrodes themselves (copper circles).
All that remains is to connect the electrodes themselves to the terminals. That’s it, the ionistor, made with your own hands, and even at home, is ready. This design does not have a very large capacity - no higher than 0.3 farads, and the charging voltage is only one volt, but this is a real ionistor. 
Conclusion on the topic
What else can be said about this element in addition? If we compare it, for example, with a nickel-metal hydride battery, then the ionistor can easily hold a supply of electricity up to 10% of the battery power. In addition, its voltage drop occurs linearly, and not abruptly. But the level of charge of the element depends on its technological purpose.
People first used capacitors to store electricity. Then, when electrical engineering went beyond laboratory experiments, batteries were invented, which became the main means of storing electrical energy. But at the beginning of the 21st century, it is again proposed to use capacitors to power electrical equipment. How possible is this and will batteries finally become a thing of the past?
The reason why capacitors were replaced by batteries was due to the significantly greater amounts of electricity that they are capable of storing. Another reason is that during discharge the voltage at the battery output changes very little, so that a voltage stabilizer is either not required or can be of a very simple design.
The main difference between capacitors and batteries is that capacitors directly store electrical charge, while batteries convert electrical energy into chemical energy, store it, and then convert the chemical energy back into electrical energy.
During energy transformations, part of it is lost. Therefore, even the best batteries have an efficiency of no more than 90%, while for capacitors it can reach 99%. The intensity of chemical reactions depends on temperature, so batteries perform noticeably worse in cold weather than at room temperature. In addition, chemical reactions in batteries are not completely reversible. Hence the small number of charge-discharge cycles (on the order of thousands, most often the battery life is about 1000 charge-discharge cycles), as well as the “memory effect”. Let us recall that the “memory effect” is that the battery must always be discharged to a certain amount of accumulated energy, then its capacity will be maximum. If, after discharging, more energy remains in it, then the battery capacity will gradually decrease. The “memory effect” is characteristic of almost all commercially produced types of batteries, except acid ones (including their varieties - gel and AGM). Although it is generally accepted that lithium-ion and lithium-polymer batteries do not have it, in fact they also have it, it just manifests itself to a lesser extent than in other types. As for acid batteries, they exhibit the effect of plate sulfation, which causes irreversible damage to the power source. One of the reasons is that the battery remains in a state of charge of less than 50% for a long time.
With regard to alternative energy, the “memory effect” and plate sulfation are serious problems. The fact is that the supply of energy from sources such as solar panels and wind turbines is difficult to predict. As a result, the charging and discharging of batteries occurs chaotically, in a non-optimal mode.
For the modern rhythm of life, it turns out to be absolutely unacceptable that batteries have to be charged for several hours. For example, how do you imagine driving a long distance in an electric vehicle if a dead battery keeps you stuck at the charging point for several hours? The charging speed of a battery is limited by the speed of the chemical processes occurring in it. You can reduce the charging time to 1 hour, but not to a few minutes. At the same time, the charging rate of the capacitor is limited only by the maximum current provided by the charger.
The listed disadvantages of batteries have made it urgent to use capacitors instead.
Using an electrical double layer
For many decades, electrolytic capacitors had the highest capacity. In them, one of the plates was metal foil, the other was an electrolyte, and the insulation between the plates was metal oxide, which coated the foil. For electrolytic capacitors, the capacity can reach hundredths of a farad, which is not enough to fully replace the battery.
Large capacitance, measured in thousands of farads, can be obtained by capacitors based on the so-called electrical double layer. The principle of their operation is as follows. An electric double layer appears under certain conditions at the interface of substances in the solid and liquid phases. Two layers of ions are formed with charges of opposite signs, but of the same magnitude. If we simplify the situation very much, then a capacitor is formed, the “plates” of which are the indicated layers of ions, the distance between which is equal to several atoms.
Capacitors based on this effect are sometimes called ionistors. In fact, this term not only refers to capacitors in which electrical charge is stored, but also to other devices for storing electricity - with partial conversion of electrical energy into chemical energy along with storing the electrical charge (hybrid ionistor), as well as for batteries based on double electrical layer (so-called pseudocapacitors). Therefore, the term “supercapacitors” is more appropriate. Sometimes the identical term “ultracapacitor” is used instead.
Technical implementation
The supercapacitor consists of two plates of activated carbon filled with electrolyte. Between them there is a membrane that allows the electrolyte to pass through, but prevents the physical movement of activated carbon particles between the plates.
It should be noted that supercapacitors themselves have no polarity. In this they fundamentally differ from electrolytic capacitors, which, as a rule, are characterized by polarity, failure to comply with which leads to failure of the capacitor. However, polarity is also applied to supercapacitors. This is due to the fact that supercapacitors leave the factory assembly line already charged, and the marking indicates the polarity of this charge.
Supercapacitor parameters
The maximum capacity of an individual supercapacitor, achieved at the time of writing, is 12,000 F. For mass-produced supercapacitors, it does not exceed 3,000 F. The maximum permissible voltage between the plates does not exceed 10 V. For commercially produced supercapacitors, this figure, as a rule, lies within 2. 3 – 2.7 V. Low operating voltage requires the use of a voltage converter with a stabilizer function. The fact is that during discharge, the voltage on the capacitor plates changes over a wide range. Building a voltage converter to connect the load and charger is a non-trivial task. Let's say you need to power a 60W load.
To simplify the consideration of the issue, we will neglect losses in the voltage converter and stabilizer. If you are working with a regular 12 V battery, then the control electronics must be able to withstand a current of 5 A. Such electronic devices are widespread and inexpensive. But a completely different situation arises when using a supercapacitor, the voltage of which is 2.5 V. Then the current flowing through the electronic components of the converter can reach 24 A, which requires new approaches to circuit technology and a modern element base. It is precisely the complexity of building a converter and stabilizer that can explain the fact that supercapacitors, the serial production of which began in the 70s of the 20th century, have only now begun to be widely used in a variety of fields.
Supercapacitors can be connected into batteries using series or parallel connections. In the first case, the maximum permissible voltage increases. In the second case - capacity. Increasing the maximum permissible voltage in this way is one way to solve the problem, but you will have to pay for it by reducing the capacitance.
The dimensions of supercapacitors naturally depend on their capacity. A typical supercapacitor with a capacity of 3000 F is a cylinder with a diameter of about 5 cm and a length of 14 cm. With a capacity of 10 F, a supercapacitor has dimensions comparable to a human fingernail.
Good supercapacitors can withstand hundreds of thousands of charge-discharge cycles, exceeding batteries by about 100 times in this parameter. But, like electrolytic capacitors, supercapacitors face the problem of aging due to the gradual leakage of electrolyte. So far, no complete statistics on the failure of supercapacitors for this reason have been accumulated, but according to indirect data, the service life of supercapacitors can be approximately estimated at 15 years.
Accumulated energy
The amount of energy stored in a capacitor, expressed in joules:
where C is the capacitance, expressed in farads, U is the voltage on the plates, expressed in volts.
The amount of energy stored in the capacitor, expressed in kWh, is:
Hence, a capacitor with a capacity of 3000 F with a voltage between the plates of 2.5 V is capable of storing only 0.0026 kWh. How does this compare to, for example, a lithium-ion battery? If we take its output voltage to be independent of the degree of discharge and equal to 3.6 V, then an amount of energy of 0.0026 kWh will be stored in a lithium-ion battery with a capacity of 0.72 Ah. Alas, a very modest result.
Application of supercapacitors
Emergency lighting systems are where using supercapacitors instead of batteries makes a real difference. In fact, it is precisely this application that is characterized by uneven discharge. In addition, it is desirable that the emergency lamp is charged quickly and that the backup power source used in it has greater reliability. A supercapacitor-based backup power supply can be integrated directly into the T8 LED lamp. Such lamps are already produced by a number of Chinese companies.
As already noted, the development of supercapacitors is largely due to interest in alternative energy sources. But practical application is still limited to LED lamps that receive energy from the sun.
The use of supercapacitors to start electrical equipment is actively developing.
Supercapacitors are capable of delivering large amounts of energy in a short period of time. By powering electrical equipment at startup from a supercapacitor, peak loads on the electrical grid can be reduced and, ultimately, the inrush current margin can be reduced, achieving huge cost savings.
By combining several supercapacitors into a battery, we can achieve a capacity comparable to the batteries used in electric vehicles. But this battery will weigh several times more than the battery, which is unacceptable for vehicles. The problem can be solved by using graphene-based supercapacitors, but they currently only exist as prototypes. However, a promising version of the famous Yo-mobile, powered only by electricity, will use new generation supercapacitors, which are being developed by Russian scientists, as a power source.
Supercapacitors will also benefit the replacement of batteries in conventional gasoline or diesel vehicles - their use in such vehicles is already a reality.
In the meantime, the most successful of the implemented projects for the introduction of supercapacitors can be considered the new Russian-made trolleybuses that recently appeared on the streets of Moscow. When the supply of voltage to the contact network is interrupted or when the current collectors “fly off”, the trolleybus can travel at a low speed (about 15 km/h) for several hundred meters to a place where it will not interfere with traffic on the road. The source of energy for such maneuvers is a battery of supercapacitors.
In general, for now supercapacitors can displace batteries only in certain “niches”. But technology is rapidly developing, which allows us to expect that in the near future the scope of application of supercapacitors will expand significantly.
Alexey Vasiliev
Supercapacitors can be called the brightest development of recent years. Compared to conventional capacitors, with the same dimensions, they differ in capacity by three orders of magnitude. For this, capacitors received their prefix - “super”. They can release enormous amounts of energy in a short period of time.
They are available in various sizes and shapes: from very small ones, which are mounted on the surface of devices, no larger than a coin in size, to very large cylindrical and prismatic ones. Their main purpose is to duplicate the main source (battery) in the event of a voltage drop.
Energy-intensive modern electronic and electrical systems place high demands on power supplies. Emerging equipment (from digital cameras to electronic handheld devices and electric vehicle transmissions) needs to store and supply the necessary energy.
Modern developers solve this problem in two ways:
- Using a battery capable of delivering a high current pulse
- By connecting in parallel to the battery as insurance for supercapacitors, i.e. "hybrid" solution.
In the latter case, the supercapacitor acts as a power source when the battery voltage drops. This is due to the fact that batteries have a high energy density and low power density, while supercapacitors, on the contrary, are characterized by low energy density but high power density, i.e. they provide discharge current to the load. By connecting a supercapacitor in parallel with the battery, you can use it more efficiently and, therefore, extend its service life.
Where are supercapacitors used?
Video: Test of a supercapacitor 116.6F 15V (6* 700F 2.5V), instead of a starter battery in a car
In automotive electronic systems they are used to start engines., thereby reducing the load on the battery. They also make it possible to reduce weight by reducing wiring diagrams. They are widely used in hybrid cars, where the generator is controlled by the internal combustion engine, and an electric motor (or motors) drive the car, i.e. The supercapacitor (energy cache) is used as a current source during acceleration and movement, and is “recharged” during braking. Their use is promising not only in passenger cars, but also in urban transport, since the new type of capacitors makes it possible to reduce fuel consumption by 50% and reduce the emission of harmful gases into the environment by 90%.
I can’t completely replace the supercapacitor battery yet, but it’s only a matter of time. Using a supercapacitor instead of a battery is not at all fantastic. If nanotechnologists from QUT University follow the right path, then in the near future this will become a reality. Body panels containing the latest generation of supercapacitors will be able to act as batteries. Employees of this university managed to combine the advantages of lithium-ion batteries and supercapacitors in a new device. The new thin, light and powerful supercapacitor consists of carbon electrodes with an electrolyte located between them. The new product, according to scientists, can be installed anywhere in the body.
Thanks to the high torque (starting torque), they can improve the starting characteristics at low temperatures and expand the capabilities of the power system now. The expediency of their use in the power system is explained by the fact that their charging/discharging time is 5-60 seconds. In addition, they can be used in the distribution system of some machine devices: solenoids, door lock adjustment systems and window glass positions.
DIY supercapacitor
You can make a supercapacitor with your own hands. Since its design consists of an electrolyte and electrodes, you need to decide on the material for them. Copper, stainless steel or brass are quite suitable for electrodes. You can take, for example, old five-kopeck coins. You will also need carbon powder (you can buy activated carbon at the pharmacy and grind it). Ordinary water will do as an electrolyte, in which you need to dissolve table salt (100:25). The solution is mixed with charcoal powder to form a putty consistency. Now it must be applied in a layer of several millimeters to both electrodes.
All that remains is to select a gasket that separates the electrodes, through the pores of which the electrolyte will freely pass, but the carbon powder will be retained. Fiberglass or foam rubber is suitable for these purposes.
Electrodes – 1.5; carbon-electrolyte coating – 2.4; gasket – 3.
You can use a plastic box as a casing, having previously drilled holes in it for the wires soldered to the electrodes. Having connected the wires to the battery, we wait for the “ionix” design to charge, so named because different concentrations of ions should form on the electrodes. It is easier to check the charge using a voltmeter.
There are other ways. For example, using tin paper (tin foil - chocolate wrapper), pieces of tin and waxed paper, which you can make yourself by cutting and immersing strips of tissue paper in melted, but not boiling, paraffin for a couple of minutes. The width of the strips should be fifty millimeters and the length from two hundred to three hundred millimeters. After removing the strips from the paraffin, you need to scrape off the paraffin with the blunt side of a knife.
Paraffin-soaked paper is folded into an accordion shape (as in the picture). On both sides, staniol sheets are inserted into the gaps, which correspond to a size of 45x30 millimeters. Having thus prepared the workpiece, it is folded and then ironed with a warm iron. The remaining staniol ends are connected to each other from the outside. For this, you can use cardboard plates and brass plates with tin clips, to which conductors are later soldered so that the capacitor can be soldered during installation.
The capacitance of the capacitor depends on the number of staniol leaves. It is equal, for example, to a thousand picofarads when using ten such sheets, and two thousand if their number is doubled. This technology is suitable for the manufacture of capacitors with a capacity of up to five thousand picofarads.
If a large capacity is needed, then you need to have an old microfarad paper capacitor, which is a roll of tape consisting of strips of waxed paper, between which a strip of staniol foil is laid.
To determine the length of the strips, use the formula:
l = 0.014 C/a, where the capacitance of the required capacitor in pF is C; width of stripes in cm – a: length in cm – 1.
After unwinding strips of the required length from the old capacitor, cut off 10 mm foil on all sides to prevent the capacitor plates from connecting to each other.
The tape needs to be rolled up again, but first by soldering stranded wires to each strip of foil. The structure is covered with thick paper on top, and two mounting wires (hard) are sealed onto the edges of the paper that protrude, to which the leads from the capacitor are soldered on the inside of the paper sleeve (see figure). The last step is to fill the structure with paraffin.
Advantages of carbon supercapacitors
Since the march of electric vehicles across the planet today cannot be ignored, scientists are working on the issue related to their fastest charging. Many ideas arise, but only a few are put into practice. In China, for example, an unusual urban transport route has been launched in the city of Ningbo. The bus running on it is powered by an electric motor, but it only takes ten seconds to charge. On it, he covers five kilometers and again, during disembarkation/pickup of passengers, manages to recharge.
This became possible thanks to the use of a new type of capacitors - carbon.
Carbon capacitors They can withstand about a million recharge cycles and work perfectly in the temperature range from minus forty to plus sixty-five degrees. They return up to 80% of energy through recovery.
They ushered in a new era in power management, reducing discharge and charging times to nanoseconds and reducing vehicle weight. To these advantages we can add low cost, since rare earth metals and environmental friendliness are not used in production.