Capacitor instead of battery: technical solution. How are supercapacitors used in hybrid cars Do-it-yourself high-capacity graphene capacitor

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

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 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.

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 power 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.

The buzz surrounding Elon Musk's construction of a “Battery Gigafactory” for the production of lithium-ion batteries has not yet died down, when a message appeared about an event that could significantly adjust the plans of the “billionaire revolutionary”.
This is a recent press release from the company. Sunvault Energy Inc., which together with Edison Power Company managed to create the world's largest graphene supercapacitor with a capacity of 10 thousand (!) Farads.
This figure is so phenomenal that it raises doubts among domestic experts - in electrical engineering even 20 Microfarads (that is, 0.02 Millifarads), this is a lot. There is no doubt, however, that the director of Sunvault Energy is Bill Richardson, the former governor of New Mexico and former US Secretary of Energy. Bill Richardson is a well-known and respected man: he served as the US ambassador to the UN, worked for several years at the Kissinger and McLarty think tank, and was even nominated for a Nobel Prize for his successes in freeing Americans captured by militants in various “hot spots” peace. In 2008, he was one of the Democratic Party candidates for the presidency of the United States, but lost to Barack Obama.

Today, Sunvault is growing rapidly, having created a joint venture with the Edison Power Company called Supersunvault, and the board of directors of the new company includes not only scientists (one of the directors is a biochemist, another is an enterprising oncologist), but also famous people with good business acumen. I note that in just the last two months the company has increased the capacity of its supercapacitors tenfold - from a thousand to 10,000 Farads, and promises to increase it even more so that the energy accumulated in the capacitor is enough to power an entire house, that is, Sunvault is ready to act directly competitor of Elon Musk, who plans to produce Powerwall-type superbatteries with a capacity of about 10 kWh.

The benefits of graphene technology and the end of the Gigafactory.

Here we need to recall the main difference between capacitors and batteries - if the former quickly charge and discharge, but accumulate little energy, then batteries - on the contrary. Note main advantages of graphene supercapacitorsV.

1. Fast charging— capacitors charge approximately 100-1000 times faster than batteries.

2. Cheapness: if conventional lithium-ion batteries cost about $500 per 1 kWh of accumulated energy, then a supercapacitor costs only $100, and by the end of the year the creators promise to reduce the cost to $40. In terms of its composition, it is ordinary carbon - one of the most common chemical elements on Earth.

3. Compactness and energy density and. The new graphene supercapacitor amazes not only with its fantastic capacity, which exceeds known samples by about a thousand times, but also with its compactness - it is the size of a small book, that is, one hundred times more compact than the 1 Farad capacitors currently used.

4. Safety and environmental friendliness. They are much safer than batteries, which heat up, contain dangerous chemicals, and sometimes even explode. Graphene itself is a biodegradable substance, that is, in the sun it simply disintegrates and does not spoil the environment. It is chemically inactive and does not harm the environment.

5. The simplicity of the new technology for producing graphene. The vast territory and capital investment, the mass of workers, the toxic and dangerous substances used in the technological process of lithium-ion batteries - all this contrasts sharply with the amazing simplicity of the new technology. The fact is that graphene (that is, the thinnest, monatomic carbon film) is produced at Sunvault... using an ordinary CD disk onto which a portion of a graphite suspension is poured. Then the disc is inserted into a regular DVD drive and burned with a laser using a special program - and the graphene layer is ready! It is reported that this discovery was made by accident - by student Maher El-Kadi, who worked in the laboratory of chemist Richard Kaner. He then burned the disk using LightScribe software to produce a layer of graphene.
Moreover, as Sunvault CEO Gary Monahan said at a Wall Street conference, the firm is working to graphene energy storage devices could be produced by conventional printing on a 3D printer- and this will make their production not only cheap, but also practically universal. And in combination with inexpensive solar panels (today their cost has dropped to $1.3 per W), graphene supercapacitors will give millions of people the chance to gain energy independence by completely disconnecting from the power grid, and even more so - to become their own electricity suppliers and, by destroying “ natural" monopolies.
Thus, there is no doubt: graphene supercapacitors are revolutionary breakthrough in the field of energy storage and . And this is bad news for Elon Musk - the construction of a plant in Nevada will cost him about $5 billion, which would be difficult to recoup even without such competitors. It seems that while construction of the Nevada plant is already underway and is likely to be completed, then the other three that Musk has planned are unlikely to be completed.

Access to the market? Not as soon as we would like.

The revolutionary nature of such technology is obvious. Another thing is unclear - when will it hit the market? Already today, Elon Musk’s bulky and expensive lithium-ion Gigafactory project looks like a dinosaur of industrialism. However, no matter how revolutionary, necessary and environmentally friendly a new technology may be, this does not mean that it will come to us in a year or two. The world of capital cannot avoid financial shocks, but it has been quite successful in avoiding technological ones. In such cases, behind-the-scenes agreements between large investors and political players come into play. It is worth recalling that Sunvault is a company located in Canada, and the board of directors includes people who, although they have extensive connections in the political elite of the United States, are still not part of its petrodollar core, a more or less obvious struggle against which, apparently it has already begun.
What is most important to us is Opportunities offered by emerging energy technologies: energy independence for the country, and in the future - for each of its citizens. Of course, graphene supercapacitors are more of a “hybrid”, transitional technology; it does not allow direct generation of energy, unlike magneto-gravitational technologies, which promise to completely change the scientific paradigm itself and the appearance of the whole world. Finally there is revolutionary financial technologies, which are actually taboo by the global petrodollar mafia. Still, this is a very impressive breakthrough, all the more interesting because it is happening in the “lair of the petrodollar Beast” - in the United States.
Just six months ago I wrote about the successes of the Italians in cold fusion technology, but during this time we learned about the impressive LENR technology of the American company SolarTrends, and about the breakthrough of the German Gaya-Rosch, and now about the truly revolutionary technology of graphene storage devices. Even this short list shows that the problem is not that our or any other government does not have the ability to reduce the bills we receive for gas and electricity, and not even in the non-transparent calculation of tariffs.
The root of evil is the ignorance of those who pay the bills and the reluctance of those who issue them to change anything . Only for ordinary people, energy is electricity. In reality, the energy of the self is power.

The scientific publication Science reported on a technological breakthrough made by Australian scientists in the field of creating supercapacitors.

Employees of Monash University, located in Melbourne, managed to change the production technology of supercapacitors made from graphene in such a way that the resulting products are more commercially attractive than previously existing analogues.

Experts have long been talking about the magical qualities of graphene-based supercapacitors, and laboratory tests have more than once convincingly proven the fact that they are better than conventional ones. Such capacitors with the prefix “super” are expected by the creators of modern electronics, automobile companies and even builders of alternative sources of electricity, etc.

The extremely long life cycle, as well as the ability of a supercapacitor to charge in the shortest possible period of time, allow designers to use them to solve complex problems when designing various devices. But until that time, the triumphal march of graphene capacitors was blocked by their low specific energy and... On average, an ionistor or supercapacitor had a specific energy indicator of the order of 5–8 Wh/kg, which, against the background of rapid discharge, made the graphene product dependent on the need to very often provide recharging.

Australian employees of the Department of Materials Manufacturing Research from Melbourne, led by Professor Dan Lee, managed to increase the specific energy density of a graphene capacitor by 12 times. Now this figure for the new capacitor is 60 W*h/kg, and this is already a reason to talk about a technical revolution in this area. The inventors managed to overcome the problem of fast discharge of the graphene supercapacitor, ensuring that it now discharges more slowly than even a standard battery.

A technological discovery helped the scientists achieve such an impressive result: they took an adaptive graphene-gel film and created a very small electrode from it. The inventors filled the space between the graphene sheets with liquid electrolyte so that a subnanometer distance was formed between them. This electrolyte is also present in conventional capacitors, where it acts as a conductor of electricity. Here it became not only a conductor, but also an obstacle to the contact of graphene sheets with each other. It was this move that made it possible to achieve a higher density of the capacitor while maintaining the porous structure.

The compact electrode itself was created using technology that is familiar to manufacturers of the paper we are all familiar with. This method is quite cheap and simple, which allows us to be optimistic about the possibility of commercial production of new supercapacitors.

Journalists hastened to assure the world that humanity has received an incentive to develop completely new electronic devices. The inventors themselves, through the mouth of Professor Lee, promised to help the graphene supercapacitor very quickly cover the path from the laboratory to the factory.

Like it or not, the era of electric cars is steadily approaching. And currently, only one technology is holding back the breakthrough and takeover of the market by electric vehicles, electric energy storage technology, etc. Despite all the achievements of scientists in this direction, most electric and hybrid cars have lithium-ion batteries in their design, which have their positive and negative sides, and can only provide a vehicle mileage on one charge for a short distance, sufficient only to travel in city ​​limits. All the world's leading automakers understand this problem and are looking for ways to increase the efficiency of electric vehicles, which will increase the driving range on a single battery charge.

One of the ways to improve the efficiency of electric cars is to collect and reuse energy that turns into heat when the car brakes and when the car moves over uneven road surfaces. Methods for returning such energy have already been developed, but the efficiency of its collection and reuse is extremely low due to the low operating speed of batteries. Braking times are typically measured in seconds, which is too fast for batteries that take hours to charge. Therefore, to accumulate “fast” energy, other approaches and storage devices are required, the role of which is most likely to be high-capacity capacitors, the so-called supercapacitors.

Unfortunately, supercapacitors are not yet ready to hit the big road; despite the fact that they can charge and discharge quickly, their capacity is still relatively low. In addition, the reliability of supercapacitors also leaves much to be desired; the materials used in the electrodes of supercapacitors are constantly destroyed as a result of repeated charge-discharge cycles. And this is hardly acceptable given the fact that over the entire life of an electric car, the number of operating cycles of supercapacitors should be many millions of times.

Santhakumar Kannappan and a group of his colleagues from the Institute of Science and Technology, Gwangju, Korea, have a solution to the above problem, the basis of which is one of the most amazing materials of our time - graphene. Korean researchers have developed and manufactured prototypes of highly efficient graphene-based supercapacitors, the capacitive parameters of which are not inferior to those of lithium-ion batteries, but which are capable of very quickly accumulating and releasing their electrical charge. In addition, even prototypes of graphene supercapacitors can withstand many tens of thousands of operating cycles without losing their characteristics.
The trick to achieving such impressive results is to obtain a special form of graphene, which has a huge effective surface area. The researchers made this form of graphene by mixing graphene oxide particles with hydrazine in water and crushing it all using ultrasound. The resulting graphene powder was packaged into disc-shaped pellets and dried at a temperature of 140 degrees Celsius and a pressure of 300 kg/cm for five hours.

The resulting material turned out to be very porous; one gram of such graphene material has an effective area equal to the area of ​​a basketball court. In addition, the porous nature of this material allows the ionic electrolytic liquid EBIMF 1 M to completely fill the entire volume of the material, which leads to an increase in the electrical capacity of the supercapacitor.

Measurements of the characteristics of experimental supercapacitors showed that their electrical capacity is about 150 Farads per gram, the energy storage density is 64 watts per kilogram, and the electric current density is 5 amperes per gram. All these characteristics are comparable to those of lithium-ion batteries, whose energy storage density ranges from 100 to 200 watts per kilogram. But these supercapacitors have one huge advantage: they can fully charge or release all their stored charge in just 16 seconds. And this time is the fastest charge-discharge time to date.

This impressive set of characteristics, plus the simple manufacturing technology of graphene supercapacitors, may justify the claim of the researchers, who wrote that their “graphene supercapacitor energy storage devices are now ready for mass production and could appear in the coming generations of electric cars.”

A group of scientists from Rice University have adapted a method they developed to produce graphene using a laser to make supercapacitor electrodes.

Since its discovery, graphene, a form of carbon whose crystal lattice is monatomically thick, has, among other things, been considered as an alternative to activated carbon electrodes used in supercapacitors, capacitors with high capacitance and low leakage currents. But time and research have shown that graphene electrodes do not work much better than microporous activated carbon electrodes, and this caused a decrease in enthusiasm and the curtailment of a number of studies.

Nevertheless, graphene electrodes have some undeniable advantages compared to porous carbon electrodes.

Graphene supercapacitors can operate at higher frequencies, and the flexibility of graphene makes it possible to create extremely thin and flexible energy storage devices based on it, which are ideally suited for use in wearable and flexible electronics.

The two aforementioned advantages of graphene supercapacitors prompted further research by a group of scientists from Rice University. They adapted the laser-assisted graphene production method they developed to make supercapacitor electrodes.

“What we have achieved is comparable to the performance of microsupercapacitors that are available in the electronics market,” says James Tour, the scientist who led the research team. “With our method, we can produce supercapacitors that have any spatial form. When we need to pack graphene electrodes into a small enough area, we simply fold them like a sheet of paper.”

To produce graphene electrodes, scientists used laser method(laser-induced grapheme, LIG), in which a powerful laser beam is aimed at a target made of an inexpensive polymer material.

The parameters of the laser light are selected in such a way that it burns out all elements from the polymer except carbon, which is formed in the form of a porous graphene film. This porous graphene has been shown to have a sufficiently large effective surface area, making it an ideal material for supercapacitor electrodes.

What makes the Rice University team's findings so compelling is the ease of producing porous graphene.

“Graphene electrodes are very simple to make. This does not require a clean room and the process uses conventional industrial lasers, which work successfully on factory floors and even outdoors,” says James Tour.

In addition to ease of production, graphene supercapacitors have shown very impressive characteristics. These energy storage devices have withstood thousands of charge-discharge cycles without loss of electrical capacity. Moreover, the electrical capacitance of such supercapacitors remained virtually unchanged after the flexible supercapacitor was deformed 8 thousand times in a row.

“We have demonstrated that the technology we have developed can produce thin and flexible supercapacitors that can become components of flexible electronics or power sources for wearable electronics that can be built directly into clothing or everyday items,” said James Tour.

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.