Homemade galvanic cell for autonomous power supply. Features of some types of galvanic cells and their brief characteristics Galvanic cells used in work

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Prerequisites for the emergence of galvanic cells. A little history. In 1786, the Italian professor of medicine, physiologist Luigi Aloisio Galvani discovered an interesting phenomenon: the muscles of the hind legs of a freshly opened frog corpse, suspended on copper hooks, contracted when the scientist touched them with a steel scalpel. Galvani immediately concluded that this was a manifestation of “animal electricity.”

After Galvani's death, his contemporary Alessandro Volta, being a chemist and physicist, would describe and publicly demonstrate a more realistic mechanism for the generation of electric current when different metals come into contact.

Volta, after a series of experiments, will come to the unequivocal conclusion that current appears in the circuit due to the presence in it of two conductors of different metals placed in a liquid, and this is not “animal electricity” at all, as Galvani thought. The twitching of the frog's legs was a consequence of the action of current generated by the contact of different metals (copper hooks and a steel scalpel).

Volta will show the same phenomena that Galvani demonstrated on a dead frog, but on a completely inanimate homemade electrometer, and will give in 1800 a precise explanation for the occurrence of current: “a conductor of the second class (liquid) is in the middle and is in contact with two conductors of the first class from two different metals... As a result, an electric current arises in one direction or another.”

In one of his first experiments, Volta dipped two plates - zinc and copper - into a jar of acid and connected them with wire. After this, the zinc plate began to dissolve, and gas bubbles appeared on the copper steel. Volta suggested and proved that an electric current flows through a wire.

This is how the “Volta element” was invented - the first galvanic cell. For convenience, Volta gave it the shape of a vertical cylinder (column), consisting of interconnected rings of zinc, copper and cloth, soaked in acid. A voltaic column half a meter high created a voltage that was sensitive to humans.

Since the research was started by Luigi Galvani, the name retained the memory of him in its name.

Galvanic cell is a chemical source of electric current based on the interaction of two metals and/or their oxides in an electrolyte, leading to the appearance of electric current in a closed circuit. Thus, in galvanic cells, chemical energy is converted into electrical energy.

Galvanic cells today

Galvanic cells today are called batteries. Three types of batteries are widely used: salt (dry), alkaline (they are also called alkaline, “alkaline” translated from English as “alkaline”) and lithium. The principle of their operation is the same as described by Volta in 1800: two metals, and an electric current arises in an external closed circuit.

The voltage of the battery depends both on the metals used and on the number of elements in the “battery”. Batteries, unlike accumulators, are not capable of restoring their properties, since they directly convert chemical energy, that is, the energy of the reagents that make up the battery (reducing agent and oxidizing agent), into electrical energy.

The reagents included in the battery are consumed during its operation, and the current gradually decreases, so the effect of the source ends after the reagents have reacted completely.

Alkaline and salt cells (batteries) are widely used to power a variety of electronic devices, radio equipment, toys, and lithium ones can most often be found in portable medical devices such as glucometers or in digital equipment such as cameras.

Manganese-zinc cells, which are called salt batteries, are “dry” galvanic cells that do not contain a liquid electrolyte solution.

The zinc electrode (+) is a glass-shaped cathode, and the anode is a powdered mixture of manganese dioxide and graphite. Current flows through the graphite rod. The electrolyte is a paste of ammonium chloride solution with the addition of starch or flour to thicken it so that nothing flows.

Typically, battery manufacturers do not indicate the exact composition of salt cells, however, salt batteries are the cheapest, they are usually used in devices where power consumption is extremely low: in watches, in remote controls remote control, in electronic thermometers, etc.

The concept of “nominal capacity” is rarely used to characterize zinc-manganese batteries, since their capacity greatly depends on operating modes and conditions. The main disadvantages of these elements are the significant rate of voltage decrease throughout the discharge and a significant decrease in the delivered capacity with increasing discharge current. The final discharge voltage is set depending on the load in the range of 0.7-1.0 V.

Not only the magnitude of the discharge current is important, but also the time schedule of the load. With intermittent discharge at high and medium currents, the performance of the batteries increases noticeably compared to continuous operation. However, at low discharge currents and months-long breaks in operation, their capacity may decrease as a result of self-discharge.

The graph above shows the discharge curves for an average salt battery for 4, 10, 20 and 40 hours for comparison with the alkaline battery, which will be discussed later.

An alkaline battery is a manganese-zinc voltaic battery that uses manganese dioxide as the cathode, powdered zinc as the anode, and an alkali solution, usually in the form of potassium hydroxide paste, as the electrolyte.

These batteries have a number of advantages (in particular, significantly higher capacity, best job at low temperatures and at high load currents).

Alkaline batteries, compared to salt batteries, can provide more current for a longer period of time. A higher current becomes possible because zinc is used here not in the form of a glass, but in the form of a powder that has a larger area of contact with the electrolyte. Potassium hydroxide in the form of a paste is used as an electrolyte.

It is thanks to the ability of this type of galvanic cells to deliver significant current (up to 1 A) for a long time that alkaline batteries are most common today.

In electric toys, in portable medical equipment, in electronic devices, in cameras - alkaline batteries are used everywhere. They last 1.5 times longer than salt ones if the discharge is low current. The graph shows discharge curves at various currents for comparison with a salt battery (the graph was shown above) for 4, 10, 20 and 40 hours.

Lithium batteries

Another fairly common type of voltaic cell is lithium batteries - single non-rechargeable voltaic cells that use lithium or its compounds as the anode. Thanks to the use alkali metal they have a high potential difference.

The cathode and electrolyte of a lithium cell can be very different, so the term "lithium cell" combines a group of cells with the same anode material. For example, manganese dioxide, carbon monofluoride, pyrite, thionyl chloride, etc. can be used as a cathode.

Lithium batteries differ from other batteries in their long service life and high cost. Depending on the size chosen and the chemistries used, a lithium battery can produce voltages from 1.5 V (compatible with alkaline batteries) to 3.7 V.

These batteries have the highest capacity per unit weight and a long shelf life. Lithium cells are widely used in modern portable electronic technology: to power the clock motherboards computers, for powering portable medical devices, wristwatches, calculators, photographic equipment, etc.

The graph above shows the discharge curves for two lithium batteries from two popular manufacturers. The initial current was 120 mA (per resistor of about 24 Ohms).

Different types of galvanic cells convert their chemical energy into electrical current. They received their name in honor of the Italian scientist Galvani, who conducted the first such experiments and research. Electricity is generated by the chemical reaction of two metals (usually zinc and copper) in an electrolyte.

Operating principle

Scientists placed a copper and zinc plate in containers with acid. They were connected by a conductor, gas bubbles formed on the first, and the second began to dissolve. This proved that electric current flows through the conductor. After Galvani, Volt took up experiments. He created a cylindrical element, similar to a vertical column. It consisted of zinc, copper and cloth rings, pre-impregnated with acid. The first element had a height of 50 cm, and the voltage generated by it was felt by a person.

The principle of operation is that two types of metal in an electrolytic medium interact, as a result of which current begins to flow through the external circuit. Modern galvanic cells and batteries are called batteries. Their voltage depends on the metal used. The device is placed in a cylinder made of soft sheet metal. The electrodes are meshes with oxidative and reduction sputtering.

Converting chemical energy into electricity eliminates the possibility of restoring the properties of batteries. After all, when the element operates, reagents are consumed, which causes the current to decrease. The reducing agent is usually the negative lead from lithium or zinc. During operation, it loses electrons. The positive part is made of metal salts or magnesium oxide, it performs the work of an oxidizing agent.

Under normal conditions, the electrolyte does not allow current to pass through; it disintegrates into ions only when the circuit is closed. This is what causes conductivity to appear. An acid solution, sodium or potassium salts are used as an electrolyte.

Varieties of elements

Batteries are used to power devices, devices, equipment, and toys. According to the scheme, all galvanic elements are divided into several types:

saline;
alkaline;
lithium

The most popular are salt batteries made of zinc and manganese. The element combines reliability, quality and reasonable price. But in lately Manufacturers are reducing or completely stopping their production, as companies that produce household appliances are gradually increasing their requirements for them. The main advantages of galvanic batteries of this type:

universal parameters allowing their use in different areas;
easy operation;
low cost;
simple conditions production;
accessible and inexpensive raw materials.

Among the disadvantages are a short service life (no more than two years), a decrease in properties due to low temperatures, a decrease in capacity with increasing current, and a decrease in voltage during operation. When salt batteries are discharged, they can leak as the positive volume of the electrode pushes out the electrolyte. Conductivity is increased by graphite and carbon black, the active mixture consists of manganese dioxide. The service life directly depends on the volume of electrolyte.

In the last century, the first alkaline elements appeared. The role of the oxidizing agent in them is played by manganese, and the reducing agent is zinc powder. The battery body is amalgamated to prevent corrosion. But the use of mercury was banned, so they were coated with mixtures of zinc powder and rust inhibitors.

The active substance in the device of a galvanic cell is these are zinc, indium, lead and aluminum. The active mass includes soot, manganese and graphite. The electrolyte is made from potassium and sodium. Dry powder significantly improves battery performance. With the same dimensions as salt types, alkaline ones have a larger capacity. They continue to work well even in severe frost.

Lithium cells are used to power modern technology. They are produced in the form of batteries and accumulators of different sizes. The former contain a solid electrolyte, while other devices contain a liquid electrolyte. This option is suitable for devices that require stable voltage and medium current charges. Lithium batteries can be charged several times, batteries are used only once, they are not opened.

Scope of application

There are a number of requirements for the production of galvanic cells. The battery case must be reliable and sealed. The electrolyte must not leak out, and foreign substances must not be allowed to enter the device. In some cases, when liquid leaks out, it will catch fire. A damaged item cannot be used. The dimensions of all batteries are almost the same, only the sizes of the batteries differ. The elements can have different shapes: cylindrical, prismatic or disk.

All types of devices have common advantages: they are compact and light in weight, adapted to different operating temperature ranges, have a large capacity and operate stably under different conditions. There are also some disadvantages, but they relate to certain types of elements. Salt ones do not last long, lithium ones are designed in such a way that they can ignite if depressurized.

The applications of batteries are numerous:

digital technology;
children's toys;
medical devices;
defense and aviation industry;
space production.

Galvanic cells are easy to use and affordable. But some types need to be handled carefully and not used if damaged. Before purchasing batteries, you should carefully study the instructions for the device that they will power.

Kyzyl, TSU

ABSTRACT

Topic: "Galvanic cells. Batteries."

Compiled by: Spiridonova V.A.

I year, IV gr., FMF

Checked by: Kendivan O.D.

2001

I. Introduction

II. Galvanic current sources

1. Types of galvanic cells

III. Batteries

1. Acidic

2. Alkaline

3. Sealed nickel-cadmium

4. Sealed

5. “DRYFIT” technology batteries

INTRODUCTION

Chemical current sources (CHS) for many years

firmly entered into our lives. In everyday life, the consumer rarely pays attention to

attention to the differences between the HIT used. For him it's batteries and

batteries. They are typically used in devices such as

flashlights, toys, radios or cars.

In the case where the power consumption is relatively

is large (10Ah), batteries are used, mainly acid ones,

as well as nickel-iron and nickel-cadmium. They are used in

portable computers (Laptop, Notebook, Palmtop), wearable devices

communications, emergency lighting etc.

In recent years, such batteries have been widely used in

backup power supplies for computers and electromechanical

systems that store energy for possible peak loads

and emergency power supply of vital systems.

GALVANIC CURRENT SOURCES

Disposable galvanic current sources

represent a unified container in which

contains an electrolyte absorbed by the active material

separator, and electrodes (anode and cathode), which is why they are called

dry elements. This term is used in relation to

all cells that do not contain liquid electrolyte. To ordinary

Dry elements include carbon-zinc elements.

Dry cells are used for low currents and intermittent

operating modes. Therefore, such elements are widely used in

telephone sets, toys, alarm systems, etc.

The action of any galvanic cell is based on the occurrence of a redox reaction in it. In its simplest form, a galvanic cell consists of two plates or rods made of different metals and immersed in an electrolyte solution. Such a system makes it possible to spatially separate the redox reaction: oxidation occurs on one metal, and reduction occurs on another. Thus, electrons are transferred from the reducing agent to the oxidizing agent through the external circuit.

Consider, as an example, a copper-zinc galvanic cell, powered by the energy of the above reaction between zinc and copper sulfate. This cell (Jacobi-Daniel cell) consists of a copper plate immersed in a copper sulfate solution (copper electrode) and a zinc plate immersed in a zinc sulfate solution (zinc electrode). Both solutions are in contact with each other, but to prevent mixing they are separated by a partition made of porous material.

When the element is operating, i.e. when the chain is closed, zinc is oxidized: on the surface of its contact with the solution, zinc atoms turn into ions and, when hydrated, pass into the solution. The electrons released in this case move along the external circuit to the copper electrode. The entire set of these processes is schematically represented by the half-reaction equation, or electrochemical equation:

Reduction of copper ions occurs at the copper electrode. The electrons coming here from the zinc electrode combine with the dehydrating copper ions coming out of the solution; copper atoms are formed and released as metal. The corresponding electrochemical equation is:

The total equation of the reaction occurring in the element is obtained by adding the equations of both half-reactions. Thus, during the operation of a galvanic cell, electrons from the reducing agent pass to the oxidizing agent through the external circuit, electrochemical processes take place at the electrodes, and directional movement of ions is observed in the solution.

The electrode at which oxidation occurs is called anode (zinc). The electrode at which reduction occurs is called the cathode (copper).

In principle, any redox reaction can produce electrical energy. However, the number of reactions

practically used in chemical sources of electrical energy is small. This is due to the fact that not every redox reaction makes it possible to create a galvanic cell with technically valuable properties. In addition, many redox reactions require the consumption of expensive substances.

Unlike the copper-zinc cell, all modern galvanic cells and batteries use not two, but one electrolyte; Such current sources are much more convenient to use.

TYPES OF GALVANIC CELLS

Carbon-zinc elements

Coal-zinc elements (manganese-zinc) are

the most common dry elements. In coal-zinc

elements use a passive (carbon) current collector in

contact with an anode made of manganese dioxide (MnO2), electrolyte made of

ammonium chloride and a zinc cathode. The electrolyte is in

paste form or impregnates a porous diaphragm.

Such an electrolyte is not very mobile and does not spread, so

the elements are called dry.

Coal-zinc elements are “restored” during

break from work. This phenomenon is due to the gradual

alignment of local inhomogeneities in the composition

electrolyte arising during the discharge process. As a result

periodic "rest" the service life of the element is extended.

The advantage of carbon-zinc elements is their

relatively low cost. To significant disadvantages

should include a significant decrease in voltage during discharge,

low specific power (5...10 W/kg) and short service life

storage

Low temperatures reduce efficiency of use

galvanic cells, and the internal heating of the battery

increases. An increase in temperature causes chemical corrosion of the zinc electrode by the water contained in the electrolyte and drying out of the electrolyte. These factors can be somewhat compensated for by keeping the battery at elevated temperatures and introducing a saline solution into the cell through a pre-made hole.

Alkaline elements

Like carbon-zinc cells, alkaline cells use a MnO2 anode and a zinc cathode with a separated electrolyte.

The difference between alkaline elements and carbon-zinc elements is

in the use of an alkaline electrolyte, as a result of which

There is virtually no gas evolution during discharge, and they can be

be sealed, which is very important for a number of them

applications.

Mercury elements

Mercury elements are very similar to alkaline elements. In them

Mercury oxide (HgO) is used. The cathode consists of a mixture of powder

zinc and mercury. The anode and cathode are separated by a separator and a diaphragm,

soaked in 40% alkali solution.

Since mercury is scarce and toxic, mercury elements are not

should be thrown away after they have been completely used. They should

go for recycling.

Silver elements

They have "silver" cathodes made of Ag2O and AgO.

Lithium cells

They use lithium anodes, an organic electrolyte

and cathodes made of various materials. They have very large

shelf life, high energy densities and efficient

over a wide temperature range because they do not contain water.

Since lithium has the highest negative potential

in relation to all metals, lithium elements

characterized by the highest rated voltage at

minimum dimensions.

Ionic conductivity is ensured by introducing into

Solvents of salts having large anions.

The disadvantages of lithium cells include their

relatively high cost due to high price

lithium, special requirements for their production (the need

inert atmosphere, purification of non-aqueous solvents). Should

Also take into account that some lithium cells when they

are explosive if opened.

Lithium cells are widely used in backup power supplies for memory circuits, measuring instruments and other high-tech systems.

BATTERIES

Batteries are chemical sources

reusable electrical energy. They consist of

two electrodes (positive and negative), electrolyte

and hulls. The accumulation of energy in the battery occurs when

the occurrence of a chemical oxidation-reduction reaction

electrodes. When the battery is discharged, the reverse occurs

processes. Battery voltage is the potential difference

between the battery poles at a fixed load.

To obtain sufficiently large voltage values or

charging, individual batteries are connected to each other

series or parallel to batteries. There are a number

generally accepted voltages for batteries: 2; 4; 6;

We will limit ourselves to considering the following batteries:

acid batteries made according to traditional

technologies;

stationary lead and drive (automotive and

tractor);

sealed maintenance-free batteries, sealed

nickel-cadmium and acid "dryfit" A400 and A500 (jelly-like

electrolyte).

ACID BATTERIES

As an example, consider a ready-to-use lead-acid battery. It consists of lattice lead plates, some of which are filled with lead dioxide and others with metal sponge lead. The plates are immersed in a 35-40% H2SO4 solution; at this concentration, the specific electrical conductivity of the sulfuric acid solution is maximum.

When the battery is operating - when it is discharged - an oxidation-reduction reaction occurs in it, during which the metal lead is oxidized:

Pb + SO4= PbSO4 + 2e-

And lead dioxide is reduced:

Pb + SO4 + 4H+ + 2e- = PbSO4 + 2H2O

Electrons given up by metallic lead atoms during oxidation are accepted by lead atoms PbO2 during reduction; electrons are transferred from one electrode to another through an external circuit.

Thus, lead metal serves as the anode in a lead battery and is negatively charged, and PbO2 serves as the cathode and is positively charged.

In the internal circuit (in the H2SO4 solution), ion transfer occurs during battery operation. SO42 ions move towards the anode, and H+ ions move towards the cathode. The direction of this movement is determined by the electric field resulting from the occurrence of electrode processes: anions are consumed at the anode, and cations are consumed at the cathode. As a result, the solution remains electrically neutral.

If we add up the equations corresponding to the oxidation of lead and the reduction of PbO2, we obtain the total reaction equation,

leaking in a lead-acid battery during its operation (discharge):

Pb + PbO2 + 4H+ + 2SO4 = 2PbSO4 + 2H2O

E.m.f. of a charged lead-acid battery is approximately 2V. As a battery discharges, its cathode (PbO2) and anode (Pb) materials are consumed. Sulfuric acid is also consumed. At the same time, the voltage at the battery terminals drops. When it becomes less than the value allowed by operating conditions, the battery is charged again.

To charge (or charge), the battery is connected to an external current source (plus to plus and minus to minus). In this case, current flows through the battery in the direction opposite to that in which it passed when the battery was discharged. As a result of this, the electrochemical processes on the electrodes are “reversed”. The lead electrode now undergoes a reduction process

PbSO4 + 2e- = Pb + SO4

those. This electrode becomes the cathode. Oxidation process occurs on the PbO2 electrode

PbSO4 + 2H2O = PbO2 + 4H+ + 2e-

therefore this electrode is now the anode. The ions in the solution move in directions opposite to those in which they moved when the battery was operating.

Adding the last two equations, we obtain the equation for the reaction that occurs when charging the battery:

2PbSO4 + 2H2O = Pb + PbO2 + 4H+ + 2SO4

It is easy to see that this process is the opposite of the one that occurs during battery operation: when the battery is charged, the substances necessary for its operation are again obtained in it.

Lead-acid batteries are usually connected into a battery, which

placed in a monoblock made of ebonite, thermoplastic, polypropylene,

polystyrene, polyethylene, asphalt pitch composition, ceramics

or glass.

One of the most important characteristics of a battery is

service life or service life (number of cycles). Deterioration

battery parameters and failure are caused primarily

queue of lattice corrosion and sliding of the active mass

positive electrode. Battery life is determined

primarily by the type of positive plates and conditions

operation.

Improvements in lead-acid batteries are on track

researching new alloys for grilles (for example, lead-calcium), lightweight and durable housing materials

(for example, based on propylene-ethylene copolymer), improvements

quality of separators.

ALKALINE BATTERIES

Silver-zinc.

have good electrical characteristics, have low mass and volume. The electrodes in them are silver oxides Ag2O, AgO (cathode) and sponge zinc (anode); The electrolyte is a KOH solution.

During battery operation, zinc is oxidized, turning into ZnO and Zn(OH)2, and silver oxide is reduced to metal. The overall reaction that occurs when a battery is discharged can be approximately expressed by the equation:

AgO + Zn = Ag + ZnO

E.m.f. of a charged silver-zinc battery is approximately 1.85 V. When the voltage drops to 1.25 V, the battery is charged. In this case, the processes on the electrodes are “reversed”: zinc is reduced, silver is oxidized - the substances necessary for the operation of the battery are again obtained.

Cadmium-nickel and iron-nickel.

CN and ZHN are very similar to each other. Their main difference is the material of the negative electrode plates; in KN batteries they are cadmium, and in ZhN batteries they are iron. KN batteries are the most widely used.

Alkaline batteries are mainly produced with lamella electrodes. In them, the active masses are enclosed in lamellas - flat boxes with holes. The active mass of the positive plates of a charged battery mainly consists of hydrated nickel oxide (Ni) Ni2O3 x H2O or NiOOH. In addition, it contains graphite, which is added to increase electrical conductivity. The active mass of the negative plates of KN batteries consists of a mixture of sponge cadmium with iron powder, and of ZhN batteries - of reduced iron powder. The electrolyte is a solution of potassium hydroxide containing a small amount of LiOH.

Let us consider the processes occurring during the operation of a KN battery. When the battery is discharged, cadmium oxidizes.

Cd + 2OH- = Cd(OH)2 + 2e-

And NiOOH is restored:

2NiOOH + 2H2O + 2e- = 2Ni(OH)2 + 2OH-

In this case, electrons are transferred from the cadmium electrode to the nickel electrode along the external circuit. The cadmium electrode serves as the anode and is negatively charged, and the nickel electrode serves as the cathode and is positively charged.

The total reaction occurring in the KN battery during its operation can be expressed by the equation that is obtained by adding the last two electrochemical equations:

2NiOOH + 2H2O + Cd = 2NI(OH)2 + CD(OH)2

E.m.f. of a charged nickel-cadmium battery is approximately 1.4 V. As the battery operates (discharges), the voltage at its terminals drops. When it drops below 1V, the battery is charged.

When charging a battery, the electrochemical processes at its electrodes are “reversed.” Metal reduction occurs at the cadmium electrode

Cd(OH)2 + 2e- = CD + 2OH-

On nickel - oxidation of nickel hydroxide (P):

2Ni(OH)2 + 2OH- = 2NiOOH + 2H2O + 2e-

The total reaction during charging is the opposite of the reaction occurring during discharge:

2Ni(OH)2 + Cd(OH)2 = 2NiOOH + 2H2O + Cd

SEALED NICKEL-CADMIUM BATTERIES

A special group of nickel-cadmium batteries are sealed batteries. The oxygen released at the end of the charge oxidizes cadmium, so the pressure in the battery does not increase. The rate of oxygen formation should be low, so the battery is charged with a relatively low current.

Sealed batteries are divided into disk,

cylindrical and rectangular.

Sealed rectangular nickel-cadmium batteries

are produced with negative non-cermet cadmium oxide electrodes or with cermet cadmium electrodes.

SEALED BATTERIES

Widely used acid batteries,

carried out according to classical technology, cause a lot of trouble

and have a harmful effect on people and equipment. They are the most

cheap, but require additional costs for their maintenance,

special premises and personnel.

"DRYFIT" TECHNOLOGY BATTERIES

The most convenient and safest of acid batteries

are completely maintenance-free sealed batteries

VRLA (Valve Regulated Lead Acid) produced using technology

"dryfit". The electrolyte in these batteries is in a jelly-like state. This guarantees the reliability of the batteries and the safety of their operation.

REFERENCES:

1. Deordiev S.S.

Batteries and their care.

K.: Technology, 1985. 136 p.

2. Electrical reference book.

In 3 volumes. T.2. Electrical products and devices/under

total ed. professors of Moscow Power Engineering Institute (editor-in-chief I.N. Orlov) and others. 7th ed. 6corr. and additional

M.: Energoatomizdat, 1986. 712 p.

3. N.L.Glinka.

General chemistry.

Publishing house "Chemistry" 1977.

4. Bagotsky V.S., Skundin A.M.

Chemical current sources.

M.: Energoizdat, 1981. 360 p.

In order to draw up a diagram of a galvanic cell, it is necessary to understand the principle of its operation and structural features.

Consumers rarely pay attention to batteries and rechargeable batteries, although these are the most popular power sources.

Chemical current sources

What is a galvanic cell? Its circuit is based on an electrolyte. The device includes a small container containing the electrolyte, which is adsorbed by the separator material. In addition, the diagram of two galvanic cells assumes the presence of What is the name of such a galvanic cell? The scheme linking two metals together assumes the presence of an oxidation-reduction reaction.

The simplest galvanic cell

It involves the presence of two plates or rods made of different metals, which are immersed in a solution of a strong electrolyte. During the operation of this galvanic cell, an oxidation process occurs at the anode, associated with the release of electrons.

At the cathode - reduction, accompanied by the acceptance of negative particles. Electrons are transferred through the external circuit to the oxidizing agent from the reducing agent.

Example of a galvanic cell

In order to compose electronic circuits galvanic cells, it is necessary to know the value of their standard electrode potential. Let us analyze a variant of a copper-zinc galvanic cell that operates on the basis of the energy released during the interaction of copper sulfate with zinc.

This galvanic cell, the diagram of which will be given below, is called a Jacobi-Daniel element. It includes which is immersed in a solution of copper sulfate (copper electrode), and it also consists of a zinc plate located in a solution of its sulfate (zinc electrode). The solutions come into contact with each other, but in order to prevent them from mixing, the element uses a partition made of porous material.

Operating principle

How does a galvanic cell operate, the circuit of which is Zn ½ ZnSO4 ½½ CuSO4 ½ Cu? During its operation, when closed electrical circuit, the process of oxidation of metallic zinc occurs.

On its surface of contact with the salt solution, the transformation of atoms into Zn2+ cations is observed. The process is accompanied by the release of “free” electrons, which move along the external circuit.

The reaction occurring at the zinc electrode can be represented as follows:

The reduction of metal cations is carried out on a copper electrode. Negative particles that enter here from the zinc electrode combine with copper cations, precipitating them in the form of metal. This process has the following form:

If we add up the two reactions discussed above, we obtain a summary equation that describes the operation of a zinc-copper galvanic cell.

The zinc electrode serves as the anode, and copper serves as the cathode. Modern galvanic cells and batteries require the use of a single electrolyte solution, which expands the scope of their application and makes their operation more comfortable and convenient.

Types of galvanic cells

The most common are carbon-zinc elements. They use a passive carbon current collector in contact with the anode, which is manganese oxide (4). The electrolyte is ammonium chloride, used in paste form.

It does not spread, which is why the galvanic cell itself is called dry. Its feature is the ability to “recover” during operation, which has a positive effect on the duration of their operational period. Such galvanic cells have low cost, but low power. As the temperature drops, they reduce their efficiency, and as the temperature rises, the electrolyte gradually dries out.

Alkaline cells require the use of an alkali solution, so they have quite a few areas of application.

In lithium cells, the active metal acts as an anode, which has a positive effect on the service life. Lithium is negative; therefore, with small dimensions, such elements have a maximum rated voltage. Among the disadvantages of such systems is the high price. Opening lithium power sources is explosive.

Conclusion

The operating principle of any galvanic cell is based on redox processes occurring at the cathode and anode. Depending on the metal used and the selected electrolyte solution, the service life of the element changes, as well as the value of the rated voltage. Currently, lithium and cadmium galvanic cells that have a fairly long service life are in demand.

Kyzyl, TSU

ABSTRACT

Topic: "Galvanic cells. Batteries."

Compiled by: Spiridonova V.A.

I year, IV gr., FMF

Checked by: Kendivan O.D.

2001

I. Introduction

II. Galvanic current sources

1. Types of galvanic cells

III. Batteries

1. Acidic

2. Alkaline

3. Sealed nickel-cadmium

4. Sealed

5. “DRYFIT” technology batteries

INTRODUCTION

Chemical current sources (CHS) for many years

firmly entered into our lives. In everyday life, the consumer rarely pays attention to

attention to the differences between the HIT used. For him it's batteries and

batteries. They are typically used in devices such as

flashlights, toys, radios or cars.

In the case where the power consumption is relatively

is large (10Ah), batteries are used, mainly acid ones,

as well as nickel-iron and nickel-cadmium. They are used in

portable computers (Laptop, Notebook, Palmtop), wearable devices

communications, emergency lighting, etc.

In recent years, such batteries have been widely used in

backup power supplies for computers and electromechanical

systems that store energy for possible peak loads

and emergency power supply of vital systems.

GALVANIC CURRENT SOURCES

Disposable galvanic current sources

represent a unified container in which

contains an electrolyte absorbed by the active material

separator, and electrodes (anode and cathode), which is why they are called

dry elements. This term is used in relation to

all cells that do not contain liquid electrolyte. To ordinary

Dry elements include carbon-zinc elements.

Dry cells are used for low currents and intermittent

operating modes. Therefore, such elements are widely used in

telephones, toys, alarm systems, etc.

The electrode at which oxidation occurs is called anode (zinc). The electrode at which reduction occurs is called the cathode (copper).

In principle, any redox reaction can produce electrical energy. However, the number of reactions

Unlike the copper-zinc cell, all modern galvanic cells and batteries use not two, but one electrolyte; Such current sources are much more convenient to use.

TYPES OF GALVANIC CELLS

Carbon-zinc elements

Coal-zinc elements (manganese-zinc) are

the most common dry elements. In coal-zinc

elements use a passive (carbon) current collector in

contact with an anode made of manganese dioxide (MnO2), electrolyte made of

ammonium chloride and a zinc cathode. The electrolyte is in

paste form or impregnates a porous diaphragm.

Such an electrolyte is not very mobile and does not spread, so

the elements are called dry.

Coal-zinc elements are “restored” during

break from work. This phenomenon is due to the gradual

alignment of local inhomogeneities in the composition

electrolyte arising during the discharge process. As a result

periodic "rest" the service life of the element is extended.

The advantage of carbon-zinc elements is their

relatively low cost. To significant disadvantages

should include a significant decrease in voltage during discharge,

low specific power (5...10 W/kg) and short service life

storage

Low temperatures reduce efficiency of use

galvanic cells, and the internal heating of the battery

Alkaline elements

Like carbon-zinc cells, alkaline cells use a MnO2 anode and a zinc cathode with a separated electrolyte.

The difference between alkaline elements and carbon-zinc elements is

in the use of an alkaline electrolyte, as a result of which

There is virtually no gas evolution during discharge, and they can be

be sealed, which is very important for a number of them

applications.

Mercury elements

Mercury elements are very similar to alkaline elements. In them

Mercury oxide (HgO) is used. The cathode consists of a mixture of powder

zinc and mercury. The anode and cathode are separated by a separator and a diaphragm,

soaked in 40% alkali solution.

Since mercury is scarce and toxic, mercury elements are not

should be thrown away after they have been completely used. They should

go for recycling.

Silver elements

They have "silver" cathodes made of Ag2O and AgO.

Lithium cells

They use lithium anodes, an organic electrolyte

and cathodes made of various materials. They have very large

shelf life, high energy densities and efficient

over a wide temperature range because they do not contain water.

Since lithium has the highest negative potential

in relation to all metals, lithium elements

characterized by the highest rated voltage at

minimum dimensions.

Ionic conductivity is ensured by introducing into

Solvents of salts having large anions.

The disadvantages of lithium cells include their

relatively high cost due to high price

lithium, special requirements for their production (the need

inert atmosphere, purification of non-aqueous solvents). Should

Also take into account that some lithium cells when they

are explosive if opened.

Lithium cells are widely used in backup power supplies for memory circuits, measuring instruments and other high-tech systems.

BATTERIES

Batteries are chemical sources

reusable electrical energy. They consist of

two electrodes (positive and negative), electrolyte

and hulls. The accumulation of energy in the battery occurs when

the occurrence of a chemical oxidation-reduction reaction

electrodes. When the battery is discharged, the reverse occurs

processes. Battery voltage is the potential difference

between the battery poles at a fixed load.

To obtain sufficiently large voltage values or

charging, individual batteries are connected to each other

series or parallel to batteries. There are a number

generally accepted voltages for batteries: 2; 4; 6;

We will limit ourselves to considering the following batteries:

acid batteries made according to traditional

technologies;

stationary lead and drive (automotive and

tractor);

sealed maintenance-free batteries, sealed

nickel-cadmium and acid "dryfit" A400 and A500 (jelly-like

electrolyte).

ACID BATTERIES

Operating principle

Varieties of elements

Scope of application

Chemical current sources

The simplest galvanic cell

Example of a galvanic cell

Operating principle

Types of galvanic cells

Conclusion

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