Capacitor instead of battery: technical solution. Homemade ionistor - we make a supercapacitor with our own hands How to make an ionistor supercapacitor at home

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 spacer.

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?

Ionistors are electrochemical devices designed to store electrical energy. They are characterized by a large charge-discharge rate (up to several tens of thousands of times), they have a very long service life unlike other batteries (rechargeable batteries and galvanic cells), low leakage current, and most importantly, ionistors can have a large capacity and very small sizes. Ionistors are widely used in personal computers, car radios, mobile devices, and so on. Designed to store memory when the main battery is removed or the device is turned off. Recently, ionistors have often been used in autonomous power systems using solar batteries.

Ionistors also store a charge for a very long time, regardless of weather conditions, they are resistant to frost and heat, and this will not affect the operation of the device in any way. In some electronic circuits, to store memory, you need to have a voltage that is higher than the voltage of the ionistor; to solve this issue, the ionistors are connected in series, and to increase the capacitance of the ionistor, they are connected in parallel. The latter type of connection is mainly used to increase the operating time of the ionistor, as well as to increase the current supplied to the load; to balance the current in a parallel connection, a resistor is connected to each ionistor.

Ionistors are often used with batteries and, unlike them, are not afraid of short circuits and sudden changes in ambient temperatures. Already today, special ionistors are being developed with a large capacity and a current of up to 1 ampere. As is known, the current of ionistors that are used today in technology for storing memory does not exceed 100 milliamps, this is one and the most important drawback of ionistors, but this cant is compensated by the above listed advantages of ionistors. On the Internet you can find many designs based on so-called supercapacitors - they are also ionistors. Ionistors appeared quite recently - 20 years ago.

According to scientists, the electrical capacity of our planet is 700 microfarads, compare with a simple capacitor... Ionistors are mainly made from charcoal, which, after activation and special treatment, becomes porous; two metal plates are pressed tightly against the compartment with the coal. Making an ionistor at home is very simple, but getting porous carbon is almost impossible; you need to process charcoal at home, and this is somewhat problematic, so it’s easier to buy an ionistor and conduct interesting experiments on it. For example, the parameters (power and voltage) of one ionistor are enough for the LED to light up brightly and for a long time or to work

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.

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.

Comparison of designs of different types of capacitors (Source: Wikipedia)

Large capacitance, measured in thousands of farads, can be achieved 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.

Supercapacitors of various capacities produced by Maxwell

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.

Schematic diagram of an uninterruptible power supply
voltage on supercapacitors, the main components are implemented
on one microcircuit produced by LinearTechnology

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:

E = CU 2 /2,
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:

W = CU 2 /7200000

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.

Powered LED ground light
from solar panels, energy storage
in which it is carried out in a supercapacitor

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.

An ionistor is a capacitor whose plates are a double electrical layer between the electrode and the electrolyte. Another name for this device is supercapacitor, ultracapacitor, double-layer electrochemical capacitor or ionix. It has a large capacity, which allows it to be used as a current source.

Supercapacitor device

The principle of operation of an ionistor is similar to a conventional capacitor, but these devices differ in the materials used. Porous materials are used as linings in such elements - activated carbon, which is a good conductor, or foamed metals. This makes it possible to increase their area many times over and, since the capacitance of the capacitor is directly proportional to the area of the electrodes, it increases to the same extent. In addition, an electrolyte is used as a dielectric, as in electrolytic capacitors, which reduces the distance between the plates and increases the capacitance. The most common parameters are several farads at a voltage of 5-10V.

Types of ionistors

There are several types of such devices:

With perfectly polarizable activated carbon electrodes. Electrochemical reactions do not occur in such elements. Aqueous solutions of sodium hydroxide (30% KOH), sulfuric acid (38% H2SO4) or organic electrolytes are used as an electrolyte;
A perfectly polarizable activated carbon electrode is used as one plate. The second electrode is weakly or non-polarizable (anode or cathode, depending on the design);
Pseudocapacitors. In these devices, reversible electrochemical reactions occur on the surface of the plates. They have a large capacity.

Advantages and disadvantages of ionistors

Such devices are used instead of batteries or accumulators. Compared to them, such elements have advantages and disadvantages.

Disadvantages of supercapacitors:

low discharge current in common elements, and designs without this drawback are highly expensive;
the voltage at the device output drops during discharge;
in the event of a short circuit in high-capacity elements with low internal resistance, the contacts burn out;
reduced permissible voltage and discharge rate compared to conventional capacitors;
higher self-discharge current than in batteries.

Advantages of ultracapacitors:

higher speed, charge and discharge current than in batteries;
durability - when tested after 100,000 charge/discharge cycles, no deterioration in parameters was noted;
high internal resistance in most designs, preventing self-discharge and failure during a short circuit;
long service life;
less volume and weight;
bipolarity - the manufacturer marks “+” and “-“, but this is the polarity of the charge applied during production tests;
wide range of operating temperatures and resistance to mechanical overloads.

Energy Density

The ability to store energy in supercapacitors is 8 times less than that of lead batteries, and 25 times less than that of lithium batteries. The energy density depends on the internal resistance: the lower it is, the higher the specific energy capacity of the device. Recent developments by scientists make it possible to create elements whose ability to store energy is comparable to lead batteries.

In 2008, an ionistor was created in India, in which the plates were made of graphene. The energy intensity of this element is 32 (Wh)/kg. For comparison, the energy capacity of car batteries is 30-40 (Wh)/kg. The accelerated charging of these devices allows them to be used in electric vehicles.

In 2011, Korean designers created a device in which, in addition to graphene, nitrogen was used. This element provided double the specific energy intensity.

Reference. Graphene is a layer of carbon, 1 atom thick.

Application of ionistors

The electrical properties of supercapacitors are used in various fields of technology.

Public transport

Electric buses, which use ionistors instead of batteries, are produced by Hyundai Motor, Trolza, Belkommunmash and some others.

These buses are structurally similar to trolleybuses without bars and do not require a contact network. They are recharged at stops while passengers are disembarking and boarding, or at the end points of the route in 5-10 minutes.

Trolleybuses equipped with ionistors are able to bypass broken contact lines and traffic jams and do not require wires in depots and parking lots at the end points of the route.

Electric cars

The main problem with electric vehicles is long charging times. An ultracapacitor with a high charging current and short charging time allows recharging during short stops.

In Russia, an Yo-mobile has been developed that uses a specially created ionistor as a battery.

In addition, installing a supercapacitor in parallel with the battery allows you to increase the current consumed by the electric motor during startup and acceleration. This system is used in KERS, in Formula 1 cars.

Consumer electronics

These devices are used in photo flashes and other devices in which the ability to quickly charge and discharge is more important than the size and weight of the device. For example, the cancer detector charges in 2.5 minutes and operates for 1 minute. This is enough to conduct research and prevent situations in which the device is inoperable due to discharged batteries.

In car stores you can purchase ionistors with a capacity of 1 farad for use in parallel with the car radio. They smooth out voltage fluctuations during engine starting.

DIY ionistor

If you wish, you can make a supercapacitor with your own hands. Such a device will have worse parameters and will not last long (until the electrolyte dries out), but will give an idea of the operation of such devices in general.

In order to make an ionistor with your own hands, you need:

copper or aluminum foil;
salt;
activated carbon from a pharmacy;
cotton wool;
flexible wires for leads;
plastic box for the case.

The manufacturing procedure for an ultracapacitor is as follows:

cut two pieces of foil so large that they fit on the bottom of the box;
solder the wires to the foil;
moisten the coal with water, grind into powder and dry;
prepare a 25% salt solution;
mix coal powder with saline solution to a paste;
moisten cotton wool with salt solution;
apply the paste in a thin, even layer on the foil;
make a “sandwich”: foil with charcoal up, a thin layer of cotton wool, foil with charcoal down;
place the structure in the box.

The permissible voltage of such a device is 0.5 V. When it is exceeded, the electrolysis process begins, and the ionistor turns into a gas battery.