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 recently, manufacturers have been reducing or completely stopping their production, as the demands on them from companies producing household appliances are gradually increasing. The main advantages of galvanic batteries of this type:

• universal parameters allowing their use in different areas;
• easy operation;
• low cost;
• simple production conditions;
• 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;
• Kids 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.

Regeneration of galvanic cells and batteries

The idea of ​​restoring discharged galvanic cells like batteries is not new. Cells are restored using special chargers. It has been practically established that the most common cup-type manganese-zinc cells and batteries, such as 3336L (KBS-L-0.5), 3336X (KBS-X-0.7), 373, 336, can be regenerated better than others. manganese-zinc batteries "Krona VTs", BASG and others.

The best way to regenerate chemical power sources is to pass through them an asymmetrical alternating current having a positive direct component. The simplest source of asymmetric current is a half-wave rectifier using a diode shunted by a resistor. The rectifier is connected to the secondary low-voltage (5-10 V) winding of a step-down transformer powered by an alternating current network. However, such a charger has a low efficiency - about 10% and, in addition, the battery being charged can be discharged if the voltage supplying the transformer is accidentally turned off.

Better results can be achieved if you use a charger made according to the diagram shown in rice. 1. In this device, the secondary winding II powers two separate rectifiers on diodes D1 and D2, to the outputs of which two rechargeable batteries B1 and B2 are connected.

rice. 1

Features of some types of galvanic cells and their brief characteristics

Bismuth-magnesium element

The anode is magnesium, the cathode is bismuth oxide, and the electrolyte is an aqueous solution of magnesium bromide. It has a very high energy intensity and increased voltage (1.97-2.1 Volts).

Options

Theoretical energy intensity:

Specific energy intensity: about 103--160 Wh/kg.

Specific energy density: about 205--248 Wh/dm3.

EMF: 2.1 Volts.

Operating temperature: -20 +55 C°.

Dioxysulfate-mercury element

A mercury dioxysulfate cell is a primary chemical current source in which the anode is zinc, the anode is a mixture of mercuric oxide and mercuric sulfate with graphite (5%), and the electrolyte is an aqueous solution of zinc sulfate. It is characterized by high power and energy density.

Characteristics

Theoretical energy intensity:

Specific energy intensity: 110-140 W/hour/kg.

Specific energy density: 623-645 W/hour/dm3.

EMF: 1.358 Volts.

Operating temperature: -14 + 60°C.

Disposal

This element is disposed of in accordance with the general rules for the disposal of equipment, preparations, alloys and compounds containing mercury.

Lithium ion battery (Li-ion)

A type of electric battery widely used in modern consumer electronics. Currently, this is the most popular type of battery in devices such as cell phones, laptops, and digital cameras.

A more advanced design of lithium-ion battery is called a lithium polymer battery.

The first lithium-ion battery was developed by Sony in 1991.

Characteristics

Energy density: 110 ... 160 W*h/kg

Internal resistance: 150 ... 250 mOhm (for 7.2 V battery)

Number of charge/discharge cycles until capacity is lost by 80%: 500-1000

Fast charge time: 2-4 hours

Allowable overcharge: very low

Self-discharge at room temperature: 10% per month

Cell voltage: 3.6 V

Load current relative to capacity:

Peak: more than 2C

Most acceptable: up to 1C

Operating temperature range: -20 - +60 °C

Device

At the beginning, coke (a product of coal processing) was used as negative plates, later graphite was used. Lithium alloys with cobalt or manganese are used as positive plates. Lithium-cobalt wafers last longer, while lithium-manganese wafers are much safer and usually have a built-in thermal fuse and temperature sensor.

When charging lithium-ion batteries, the following reactions occur:

on positive plates: LiCoO2 > Li1-xCoO2 + xLi+ + xe-

on negative plates: C + xLi+ + xe- > CLix

During discharge, reverse reactions occur.

Advantage

High energy density.

Low self-discharge.

There is no memory effect.

Easy to maintain.

Flaws

Li-ion batteries can be dangerous if the battery case ruptures, and if not handled carefully can have a shorter life cycle than other types of batteries. A deep discharge completely destroys a lithium-ion battery. Attempting to charge such batteries may result in an explosion. Optimal storage conditions for Li-ion batteries are achieved at 70% charge of the battery capacity. In addition, a Li-ion battery is subject to aging, even if it is not used: after just two years, the battery loses most of its capacity.

Lithium polymer battery(Li-pol or Li-polymer)

This is a more advanced design of the lithium-ion battery. Used in mobile phones and digital technology.

Conventional, household lithium-polymer batteries are not capable of delivering high current, but there are special power lithium-polymer batteries that can deliver a current 10 and even 20 times higher than the numerical value of the capacity (10-20C). They are widely used in portable power tools and radio-controlled models.

Advantages: low price per unit of capacity; high energy density per unit volume and mass; low self-discharge; thickness of elements up to 1 mm; the ability to obtain very flexible forms; environmentally friendly; slight voltage drop as the discharge progresses.

Flaw: Operating temperature range is limited: cells do not perform well in cold conditions and may explode if overheated above 70 degrees Celsius. They require special charging algorithms (chargers) and pose an increased fire hazard if handled incorrectly.

Magnesium-m-DNB element

This is a primary chemical current source in which the anode is magnesium, the cathode is meta-Dinitrobenzene, and the electrolyte is an aqueous solution of magnesium perchlorate.

Options

Theoretical energy intensity: 1915 W/hour/kg.

Specific energy intensity: 121 W/hour/kg.

Specific energy density: 137-154 W/hour/dm3.

EMF: 2 Volts.

Manufacturers

The leader in the production of this element and improvement of its design is Marathon.

Magnesium perchlorate element

This is a primary backup chemical current source in which magnesium serves as the anode, manganese dioxide mixed with graphite (up to 12%) as the cathode, and an aqueous solution of magnesium perchlorate as the electrolyte.

Options

Theoretical energy intensity: 242W/hour/kg.

Specific energy intensity: 118 W/hour/kg.

Specific energy density: 130-150 W/hour/dm3.

EMF: 2 Volts.

Manganese-zinc element

This is a primary chemical current source in which the anode is zinc Zn, the electrolyte is an aqueous solution of potassium hydroxide KOH, and the cathode is manganese oxide MnO2 (pyrolusite) in a mixture of graphite (about 9.5%).

Options

Theoretical energy intensity:

Specific energy intensity: 67-99 W/hour/kg

Specific energy density: 122--263 W/hour/dmі.

EMF: 1.51 Volts.

Operating temperature:?40 +55 °C.

Copper oxide galvanic cell

A chemical current source in which the anode is zinc (less commonly tin), the electrolyte is potassium hydroxide, and the cathode is copper oxide (sometimes with the addition of barium oxide to increase capacity or bismuth oxide).

History of invention

The history of the invention of the copper-oxide galvanic cell dates back to 1882.

The inventor of this element is Lalande. Sometimes the copper oxide element is also called the Edison and Wedekind element, but it is Lalande who holds the honor of the invention.

Options

Theoretical energy intensity: about 323.2W/hour/kg

Specific energy intensity (W/hour/kg): about - 84-127W/hour/kg

Specific energy density (W/hour/dm3): about - 550 W/hour/dm3)

EMF: 1.15 Volts.

Operating temperature: -30 +45 C.

Nickel-camdmium battery (NiCd)

A secondary chemical current source, the electrochemical system of which is arranged as follows: the anode is metal cadmium Cd (in powder form), the electrolyte is potassium hydroxide KOH with the addition of lithium hydroxide LiOH (to form lithium nickelates and increase the capacity by 21-25%), cathode -- nickel oxide hydrate NiOOH with graphite powder (about 5-8%).

The emf of a nickel-cadmium battery is about 1.45 V, the specific energy is about 45-65 Wh/kg. Depending on the design, operating mode (long or short discharges), and the purity of the materials used, the service life ranges from 100 to 3500 charge-discharge cycles.

Options

Theoretical energy content: 237 Wh/kg.

Specific energy intensity: 45--65 Wh/kg.

Specific energy density: 50--150 Wh/dm3.

Specific power: 150 W/kg.

EMF: 1.2--1.35 V.

Self-discharge: 10% per month.

Operating temperature: -15…+40 °C.

Unlike conventional, disposable batteries, a NiCd battery maintains voltage “until the last”, and then, when the battery’s energy is exhausted, the voltage quickly decreases.

The most favorable mode for a NiCd battery is discharge with medium currents (camera), charge for 14 hours with a current equal to 0.1 of the battery capacity, expressed in ampere-hours.

Batteries of this type are susceptible to memory effect and quickly fail if an incompletely discharged battery is frequently charged.

NiCd batteries should be stored discharged.

Areas of use

Small-sized nickel-cadmium batteries are used in various equipment as a replacement for a standard galvanic cell.

Nickel-cadmium batteries are used on electric cars, trams and trolleybuses (to power control circuits), river and sea vessels.

Manufacturers

Ni-Cd batteries are produced by many companies, including large international companies, such as: GP Batteries Int. Ltd., VARTA, KONNOC, METABO, EMM, Advanced Battery Factory, Panasonic/Matsushita Electric Industrial, ANSMANN and others.

Advantages: Safe disposal

Nickel metal hydride battery (Ni-MH)

A secondary chemical current source in which the anode is a hydrogen metal hydride electrode (usually nickel-lanthanum or nickel-lithium hydride), the electrolyte is potassium hydroxide, and the cathode is nickel oxide.

History of invention

Research into NiMH battery technology began in the seventies and was undertaken as an attempt to overcome the shortcomings of nickel-cadmium batteries.

However, the metal hydride compounds used at that time were unstable and the required characteristics were not achieved. As a result, the development of NiMH batteries has stalled.

New metal hydride compounds stable enough for battery use were developed in the 1980s.

Since the late eighties, NiMH batteries have been constantly improved, mainly in terms of energy density.

Their developers noted that NiMH technology has the potential to achieve even higher energy densities.

Options

Theoretical energy content (Wh/kg): 300 Wh/kg.

Specific energy intensity: about 60-72 Wh/kg.

Specific energy density (Wh/dm): about -- 150 Wh/dm.

Operating temperature: -40...+55 °C.

A battery discharged by weak currents (for example, in a TV remote control) quickly loses capacity and fails.

Storage

Batteries must be kept fully charged! During storage, it is necessary to check the voltage regularly (once every 1-2 months). It should not fall below 1 V. If the voltage drops, you need to charge the batteries again. The only type of battery that can be stored discharged is Ni-Cd batteries.

Areas of use

High power Ni-MH Battery of Toyota NHW20 Prius, Japan

Nickel-metal hydride battery made by Varta, “Museum Autovision”, AltluЯheim

Replacement of a standard galvanic cell, electric vehicles.

Manufacturers

Nickel-metal hydride batteries are manufactured by various companies, including: GP, Varta, Sanyo, TDK

Mercury-bismuth indium element

(an element of the “mercury oxide-indium-bismuth” system) is a chemical current source with a high specific energy intensity by mass and volume, and has a stable voltage. The anode is an alloy of bismuth with indium, the electrolyte is potassium hydroxide, the cathode is mercury oxide with graphite.

Options

Theoretical energy intensity:

Specific energy intensity (W/hour/kg): about - 77-109 W/hour/kg

Specific energy density (W/hour/dm3): about - 201--283 W/hour/dm3.

EMF: 1.17 volts

Application

It is considered a very reliable source of reference voltage and is used in military equipment and in particularly important cases (control equipment for nuclear reactors and high-temperature units, used in telemetry systems and other important areas). In recent years, this electrochemical system has been significantly improved and is used as an energy source for portable (mobile) satellite communication and navigation systems in the military field, and for powering portable computers.

Manufacturers

The leader in the production of mercury-bismuth-indium cells and batteries is Crompton Parkinson.

Mercury-zinc element (“RC type”)

A galvanic cell in which the anode is zinc, the cathode is mercury oxide, and the electrolyte is a solution of potassium hydroxide.

Advantages: constant voltage and huge energy intensity and energy density.

Flaws: high price, mercury toxicity if the seal is broken.

Options

Theoretical energy content: 228.72 Wh/kg

Specific energy intensity: up to 135 Wh/kg

Specific energy density: 550--750 Wh/dmі).

EMF: 1.36 V.

Operating temperature: -- 12…+80 C°.

It is characterized by low internal resistance, stable voltage, high energy intensity and energy density.

Application

Due to their enormous energy density, by the 1980s, mercury-zinc elements had found relatively widespread use as power sources in watches, pacemakers, hearing aids, photo exposure meters, military night vision devices, portable radio equipment for military purposes, and in spacecraft. Distribution is limited due to the toxicity of mercury and high cost, while at the same time the volume of production of mercury-zinc batteries and elements, remaining approximately at the same level, is about one to one and a half million per year worldwide.

Separately, it should be noted that the mercury-zinc element is reversible, that is, it can work as a battery. However, during cycling (charge-discharge), degradation of the element and a decrease in its capacity are observed.

This is mainly due to the flow and clumping of mercury into large droplets during discharge and the growth of zinc dendrites during charging. To reduce these phenomena, it is proposed to introduce magnesium hydroxide into the zinc electrode, introduce fine silver powder (up to 9%) into the mercury oxide electrode, and partially replace graphite with carbine.

Manufacturers

Firms are leaders in the production of mercury-zinc batteries: Union Carbide, VARTA, BEREC, Mallory.

Environmental features

toxicity of mercury when the seal is broken.

Elements of the RC type have recently been replaced by safer ones, since the problem of their separate collection and, especially, safe disposal is quite complex.

Lead - fluoride element

This is a primary, backup chemical current source in which the anode is lead, the cathode is lead dioxide mixed with graphite (about 3.5%), and the electrolyte is an aqueous solution of hydrofluorosilicic acid. It is distinguished by the ability to work well in the region of negative temperatures, and the ability to discharge currents of enormous power (up to 60 Amperes/dm3 of electrode area).

Options

Theoretical energy intensity:

Specific energy intensity: 34--50 Wh/kg

Specific energy density: 95--112 Wh/dm3.

EMF: 1.95 Volts.

Operating temperature: -50 +55°С.

Lead acid battery

The most common type of battery today was invented in 1859 by the French physicist Gaston Plante. Main areas of application: starter batteries in motor vehicles, emergency power sources.

Operating principle

The operating principle of lead-acid batteries is based on the electrochemical reactions of lead and lead dioxide in a sulfuric acid environment. During the discharge, lead dioxide is reduced at the cathode and lead oxidized at the anode. During charging, reverse reactions occur, to which at the end of the charge is added the reaction of electrolysis of water, accompanied by the release of oxygen on the positive electrode and hydrogen on the negative.

Device

A lead-acid battery cell consists of positive and negative electrodes, separators (separation grids) and electrolyte. The positive electrodes are a lead grid, and the active substance is lead oxide (PbO2). The negative electrodes are also lead grid, and the active substance is sponge lead (Pb). In practice, antimony is added to lead gratings in an amount of 1-2% to increase strength. The electrodes are immersed in an electrolyte consisting of dilute sulfuric acid (H2SO4). The highest conductivity of this solution at room temperature (which means the lowest internal resistance and lowest internal losses) is achieved at its density of 1.26 g/cm3. However, in practice, often in areas with cold climates, higher concentrations of sulfuric acid are used, up to 1.29–1.31 g/cm3. (This is done because when a lead-acid battery is discharged, the density of the electrolyte drops, and its freezing point, therefore, becomes higher; the discharged battery may not withstand the cold.)

In new versions, lead plates (grids) are replaced with carbon foam coated with a thin lead film *, and the liquid electrolyte can be gelled with silica gel to a paste-like state.

Options

Specific energy intensity (Wh/kg): about 30-40 Wh/kg.

Specific energy density (Wh/dm): about 60-75 Wh/dm.

Operating temperature: from minus 40 to plus 40

Storage

Lead-acid batteries must be stored in a charged state. At temperatures below?20 °C, batteries should be charged with a constant voltage of 2.275 V/ac, once a year, for 48 hours. At room temperature - once every 8 months with a constant voltage of 2.4 V/ac for 6-12 hours. Storing batteries at temperatures above 30°C is not recommended.

Silver-zinc battery

A secondary electrochemical current source in which zinc is the anode, potassium hydroxide is the electrolyte, and silver oxide is the cathode. It is characterized by very low internal resistance and high specific energy capacity (150 Wh/kg, 650 Wh/dm3). EMF 1.85 V (operating voltage 1.55 V). It is used in aviation, space, military equipment, watches, etc. One of the most important features of a silver-zinc battery is the ability (with proper design) to deliver colossal currents to the load (up to 50 Amperes per 1 Ampere hour of capacity).

Options

Theoretical energy intensity: up to 425 Wh/kg.

Specific energy intensity: up to 150 Wh/kg.

Specific energy density: up to 650 Wh/dm3.

EMF: 1.85 V.

Operating temperature: -40…+50 °C.

Application

Two silver-zinc batteries with a capacity of 120 Ah and a voltage of 366 V were used in the Lunokhod, which was used to transport astronauts on the Moon during the Apollo program. The maximum theoretical range on the moon was 92 km.

Manufacturers

The leader in the production of silver-zinc batteries of various capacities in Russia is the company "RIGEL", St. Petersburg.

16) Sulfur - magnesium element

This is a backup primary chemical current source in which the anode is magnesium, the cathode is sulfur mixed with graphite (up to 10%), and the electrolyte is a sodium chloride solution.

Options

Theoretical energy intensity:

Specific energy intensity: 103-128 W/hour/kg.

Specific energy density: 155-210 W/hour/dm3.

EMF: 1.65 Volts.

Chloride - copper - magnesium element

This is a primary backup chemical current source in which magnesium is the anode, copper monochloride is the cathode, and an aqueous solution of sodium chloride is the electrolyte.

Options

Specific energy intensity: 38-50 W/hour/kg.

Specific energy density: 63-90 W/hour/dm3.

EMF: 1.8 Volts.

Chloride - lead - magnesium element

This is a primary backup chemical current source in which magnesium is the anode, lead chloride mixed with graphite is the cathode, and sodium chloride solution is the electrolyte.

Options

Specific energy intensity: 45-50 W/hour/kg.

Specific energy density: 70-98 W/hour/dm3.

EMF: 1.1 Volts.

Chloro - silver element

This is a primary chemical source of current in which the anode is zinc, the cathode is silver chloride, and the electrolyte is an aqueous solution of ammonium chloride (ammonia) or sodium chloride.

This galvanic cell was introduced into practice by De La Rue in 1868 to conduct his experiments with electricity. De La Rue built the most powerful and high-voltage galvanic battery at that time; he used 14,000 (!) silver-chlorine elements in his famous experiments with an electric spark.

Options

Specific energy intensity: up to 127 W/hour/kg

Specific energy density: up to 500 W/hour/dm3.

EMF: 1.05 Volt.

Operating temperature: -15 +70°С.

Silver chloride - magnesium element

This is a primary backup chemical current source in which magnesium is the anode, silver chloride is the cathode, and an aqueous solution of sodium chloride is the electrolyte.

Theoretical energy intensity:

Specific energy intensity: 45-64 W/hour/kg.

Specific energy density: 83-125 W/hour/dm3.

Low-power sources of electrical energy

Galvanic cells and batteries are used to power portable electrical and radio equipment.

Galvanic cells- these are single action sources, batteries- reusable sources.

The simplest galvanic cell

The simplest element can be made from two strips: copper and zinc, immersed in water slightly acidified with sulfuric acid. If the zinc is pure enough to be free from local reactions, no noticeable change will occur until the copper and zinc are connected by wire.

However, the strips have different potentials relative to each other, and when they are connected by a wire, a will appear in it. As this action proceeds, the zinc strip will gradually dissolve, and gas bubbles will form near the copper electrode and collect on its surface. This gas is hydrogen, formed from the electrolyte. Electric current flows from the copper strip through the wire to the zinc strip, and from it through the electrolyte back to the copper.

Gradually, the sulfuric acid of the electrolyte is replaced by zinc sulfate, formed from the dissolved part of the zinc electrode. Due to this, the voltage of the element is reduced. However, an even greater voltage drop is caused by the formation of gas bubbles on the copper. Both of these actions produce "polarization." Such elements have almost no practical significance.

Important parameters of galvanic cells

The magnitude of the voltage provided by galvanic cells depends only on their type and design, i.e., on the material of the electrodes and the chemical composition of the electrolyte, but does not depend on the shape and size of the elements.

The amount of current that a galvanic cell can produce is limited by its internal resistance.

A very important characteristic of a galvanic cell is. Electrical capacity means the amount of electricity that a galvanic or battery cell is capable of delivering during the entire time of its operation, i.e., until the final discharge occurs.

The capacity given by the element is determined by multiplying the strength of the discharge current, expressed in amperes, by the time in hours during which the element was discharged until the onset of complete discharge. Therefore, electrical capacity is always expressed in ampere-hours (A x h).

Based on the capacity of the element, you can also determine in advance how many hours it will work before it is completely discharged. To do this, you need to divide the capacity by the discharge current permissible for this element.

However, electrical capacitance is not a strictly constant value. It varies within fairly wide limits depending on the operating conditions (mode) of the element and the final discharge voltage.

If the element is discharged with maximum current and without interruption, then it will give off significantly less capacity. On the contrary, when the same element is discharged with a lower current and with frequent and relatively long breaks, the element will give up its full capacity.

As for the effect of the final discharge voltage on the capacitance of the element, it must be borne in mind that during the discharge of a galvanic cell, its operating voltage does not remain at the same level, but gradually decreases.

Common types of galvanic cells

The most common galvanic cells are manganese-zinc, manganese-air, zinc-air and mercury-zinc systems with salt and alkaline electrolytes. Dry manganese-zinc cells with a salt electrolyte have an initial voltage of 1.4 to 1.55 V, operating time at ambient temperatures from -20 to -60 o C from 7 hours to 340 hours.

Dry manganese-zinc and zinc-air cells with an alkaline electrolyte have a voltage from 0.75 to 0.9 V and an operating time from 6 hours to 45 hours.

Dry mercury-zinc cells have an initial voltage of 1.22 to 1.25 V and a run time of 24 hours to 55 hours.

Dry mercury-zinc elements have the longest guaranteed shelf life, reaching 30 months.

These are secondary galvanic cells.Unlike galvanic cells, no chemical processes occur in the battery immediately after assembly.

In order for chemical reactions associated with the movement of electric charges to begin in the battery, the chemical composition of its electrodes (and partly the electrolyte) must be changed accordingly. This change in the chemical composition of the electrodes occurs under the influence of electric current passed through the battery.

Therefore, in order for the battery to produce electric current, it must first be “charged” with direct electric current from some external current source.

Batteries also differ favorably from conventional galvanic cells in that after discharge they can be charged again. With good care and under normal operating conditions, batteries can withstand up to several thousand charges and discharges.
Battery device

Currently, lead and cadmium-nickel batteries are most often used in practice. For the former, the electrolyte is a solution of sulfuric acid, and for the latter, a solution of alkalis in water. Lead batteries are also called acid batteries, and nickel-cadmium batteries are called alkaline batteries.

The principle of operation of batteries is based on the polarization of electrodes. The simplest acid battery is designed as follows: these are two lead plates dipped into an electrolyte. As a result of the chemical substitution reaction, the plates are covered with a slight coating of lead sulfate PbSO4, as follows from the formula Pb + H 2 SO 4 = PbSO 4 + H 2.

Acid battery device

This state of the plates corresponds to a discharged battery. If the battery is now turned on for a charge, i.e., connected to a direct current generator, then due to electrolysis, polarization of the plates will begin in it. As a result of charging the battery, its plates are polarized, i.e., they change the substance of their surface, and from homogeneous (PbSO 4) turn into dissimilar (Pb and Pb O 2).

The battery becomes a source of current, and its positive electrode is a plate coated with lead dioxide, and the negative electrode is a clean lead plate.

Towards the end of the charge, the electrolyte concentration increases due to the appearance of additional sulfuric acid molecules in it.

This is one of the features of a lead-acid battery: its electrolyte does not remain neutral and itself participates in chemical reactions during battery operation.

Towards the end of the discharge, both battery plates are again covered with lead sulfate, as a result of which the battery ceases to be a source of current. The battery is never brought to this state. Due to the formation of lead sulfate on the plates, the electrolyte concentration at the end of the discharge decreases. If you put the battery on charge, you can again cause polarization in order to put it on discharge again, etc.

How to charge the battery

There are several ways to charge batteries. The simplest is normal battery charging, which occurs as follows. Initially, for 5 - 6 hours, the charge is carried out with double normal current until the voltage on each battery bank reaches 2.4 V.

Normal charging current is determined by the formula I charge = Q/16

Where Q - nominal battery capacity, Ah.

After this, the charging current is reduced to a normal value and the charge continues for 15 - 18 hours, until signs of the end of the charge appear.

Modern batteries

Cadmium-nickel, or alkaline batteries, appeared much later than lead batteries and, in comparison with them, are more advanced chemical current sources. The main advantage of alkaline batteries over lead batteries is the chemical neutrality of their electrolyte with respect to the active masses of the plates. Due to this, the self-discharge of alkaline batteries is much less than that of lead batteries. The operating principle of alkaline batteries is also based on the polarization of the electrodes during electrolysis.

To power radio equipment, sealed cadmium-nickel batteries are produced, which are operational at temperatures from -30 to +50 o C and can withstand 400 - 600 charge-discharge cycles. These batteries are made in the form of compact parallelepipeds and disks with a mass of several grams to kilograms.

They produce nickel-hydrogen batteries for power supply to autonomous facilities. The specific energy of a nickel-hydrogen battery is 50 - 60 Wh kg -1.

"Arzamas State Pedagogical Institute named after A.P. Gaidar"

Course work

in chemistry

Topic: Galvanic cells

Completed by: 5th year student

EHF 52 gr. B2 subgr. Shirshin N.V.

Accepted by: Kinderov A.P.

Plan

Introduction

I. History of the creation of chemical current sources

II. Operating principle

III. Classification, design and principle of operation of chemical current sources

1. Galvanic cell

2. Electric batteries

A) Alkaline batteries

3. Fuel cell

A) Operating principle

B) The principle of separation of fuel and fuel flows

B) Example of a hydrogen-oxygen fuel cell

D) History of research in Russia

D) Application of fuel cells

E) Fuel cell problems

IV. Operating Cells and Batteries

V. Regeneration of galvanic cells and batteries

VI. Features of some types of galvanic cells and their brief characteristics

Conclusion

List of used literature

Introduction

Chemical current sources have become a part of our lives for many years. In everyday life, consumers rarely pay attention to the differences between the chemical power sources used. For him, these are batteries and accumulators. They are typically used in devices such as flashlights, toys, radios or cars. In the case when the power consumption is relatively high (10Ah), batteries are used, mainly acid batteries, as well as nickel-iron and nickel-cadmium. They are used in portable electronic computers (Laptop, Notebook, Palmtop), wearable communications equipment, emergency lighting, etc.

Due to a number of circumstances, chemical generators of electrical energy are the most promising. Their advantages are manifested through parameters such as high energy yield; noiselessness and harmlessness; possibility of use in any conditions, including in space and under water, in stationary and portable devices, in transport, etc.

In recent years, such batteries have been widely used in backup power supplies for computers and electromechanical systems that accumulate energy for possible peak loads and emergency power supply of vital systems.

Goals and objectives. In this work, I need to analyze the principle of operation of galvanic cells, get acquainted with the history of their creation, the classification features and structure of various types of galvanic cells, as well as the use of certain types of chemical current sources in everyday life and various areas of production.

I. History of the creation of chemical current sources

Chemical current sources(abbr. HIT) - devices in which the energy of the chemical reactions occurring in them is directly converted into electrical energy.

History of creation

Voltaic pole

The first chemical current source was invented by the Italian scientist Alessandro Volta in 1800. It was Volta's element - a vessel with salt water with zinc and copper plates lowered into it, connected by wire. The scientist then assembled a battery from these elements, which was later called the Voltaic Column. This invention was subsequently used by other scientists in their research. For example, in 1802, Russian academician V.V. Petrov constructed a Voltaic column of 2100 elements to produce an electric arc. In 1836, English chemist John Daniel improved the Voltaic element by placing zinc and copper electrodes in a solution of sulfuric acid. This design became known as the "Daniel element". In 1859, French physicist Gaston Plante invented the lead-acid battery. This type of cell is still used in car batteries today. In 1865, the French chemist J. Leclanchet proposed his galvanic cell (Leclanchet element), which consisted of a zinc cup filled with an aqueous solution of ammonium chloride or other chloride salt, into which was placed an agglomerate of manganese(IV) oxide MnO2 with a carbon conductor. A modification of this design is still used in salt batteries for various household devices. In 1890, in New York, Conrad Hubert, an immigrant from Russia, creates the first pocket electric flashlight. And already in 1896, the National Carbon company began mass production of the world's first dry cells, Leclanche "Columbia".

II. Operating principle

The device of the “Baghdad batteries” (200 BC).

The basis of chemical current sources are two electrodes (a cathode containing an oxidizing agent and an anode containing a reducing agent) in contact with the electrolyte. A potential difference is established between the electrodes - an electromotive force corresponding to the free energy of the redox reaction. The action of chemical current sources is based on the occurrence of spatially separated processes in a closed external circuit: at the cathode, the reducing agent is oxidized, the resulting free electrons pass, creating a discharge current, along the external circuit to the anode, where they participate in the reduction reaction of the oxidizing agent.

Modern chemical current sources use:

as a reducing agent (at the anode) - lead Pb, cadmium Cd, zinc Zn and other metals;

as an oxidizing agent (at the cathode) - lead(IV) oxide PbO2, nickel hydroxide NiOOH, manganese(IV) oxide MnO2 and others;

as an electrolyte - solutions of alkalis, acids or salts.

III. Classification, device and principle of operation

Depending on the possibility or impossibility of reuse, chemical current sources are divided into:

1. Galvanic cell

Galvanic cell - a chemical source of electric current named after Luigi Galvani. The principle of operation of a galvanic cell is based on the interaction of two metals through an electrolyte, leading to the generation of electric current in a closed circuit. The emf of a galvanic cell depends on the material of the electrodes and the composition of the electrolyte. These are primary CITs, which, due to the irreversibility of the reactions occurring in them, cannot be recharged.

Galvanic cells are disposable sources of electrical energy. The reagents (oxidizing agent and reducing agent) are included directly in the composition of the galvanic cell and are consumed during its operation. A galvanic cell is characterized by emf, voltage, power, capacity and energy transferred to the external circuit, as well as storability and environmental safety.

The EMF is determined by the nature of the processes occurring in the galvanic element. The voltage of a galvanic cell U is always less than its EMF due to the polarization of the electrodes and resistance losses:

U = Eе – I(r1–r2) – ΔE,

where Ee is the EMF of the element; I – current strength in the operating mode of the element; r1 and r2 – resistance of conductors of the first and second kind inside the galvanic cell; ΔE is the polarization of a galvanic cell, consisting of the polarizations of its electrodes (anode and cathode). Polarization increases with increasing current density (i), determined by the formula i = I/S, where S is the cross-sectional area of ​​the electrode, and increasing system resistance.

During the operation of a galvanic cell, its EMF and, accordingly, voltage gradually decrease due to a decrease in the concentration of reagents and an increase in the concentration of products of redox processes on the electrodes (remember the Nernst equation). However, the slower the voltage decreases during the discharge of a galvanic cell, the greater the possibilities for its use in practice. The capacitance of an element is the total amount of electricity Q that a galvanic cell is capable of delivering during operation (during discharge). The capacity is determined by the mass of reagents stored in the galvanic cell and the degree of their conversion. With an increase in the discharge current and a decrease in the operating temperature of the element, especially below 00C, the degree of conversion of reagents and the capacity of the element decrease.

The energy of a galvanic cell is equal to the product of its capacitance and voltage: ΔН = Q.U. Elements with a high EMF value, low mass and a high degree of conversion of reagents have the highest energy.

Storability is the length of the storage period of an element during which its characteristics remain within the specified parameters. As the temperature of storage and operation of an element increases, its shelf life decreases.

Composition of the galvanic cell: reducing agents (anodes) in portable galvanic cells, as a rule, are zinc Zn, lithium Li, magnesium Mg; oxidizers (cathodes) - oxides of manganese MnO2, copper CuO, silver Ag2O, sulfur SO2, as well as salts CuCl2, PbCl2, FeS and oxygen O2.

The most massive in the world What remains is the production of manganese-zinc elements Mn-Zn, widely used to power radio equipment, communication devices, tape recorders, flashlights, etc. The design of such a galvanic cell is shown in the figure.

The current-generating reactions in this element are:

On anode(–): Zn – 2ē → Zn2+ (in practice, the zinc shell of the element body gradually dissolves);

On cathode(+): 2MnO2 + 2NH4+ + 2ē → Mn2O3 + 2NH3 + H2O.

The following processes also take place in the electrolytic space:

U anode Zn2+ + 2NH3 →2+;

U cathode Mn2O3 + H2O → or 2.

In molecular form, the chemical side of the operation of a galvanic cell can be represented by the total reaction:

Zn + 2MnO2 + 2NH4Cl → Cl2 + 2.

Galvanic cell diagram:

(–) Zn|Zn(NH3)2]2+|||MnO2 (C) (+).

The EMF of such a system is E = 1.25 ÷ 1.50V.

Text provided by the Scientific Research Center "Science and Technology"
The rights to the electronic version of the publication belong to N&T (www.n-t.org)

The book contains information about the design, principles of operation and characteristic features of chemical power sources (batteries and accumulators). You will learn from this book how to choose the batteries and accumulators you need, how to charge and restore them correctly.

• The anode is the positive terminal of the battery.
• Battery - two or more cells connected in series and/or parallel to provide the required voltage and current.
• Internal resistance is the resistance to current flow through an element, measured in ohms. Sometimes called internal impedance.
• Energy output is the capacity consumption multiplied by the average voltage during the discharge time of the batteries, expressed in Watt hours (Wh).
• Capacity is the amount of electrical energy that a battery releases under certain discharge conditions, expressed in ampere hours (Ah) or coulombs (1 Ah = 3600 C).
• Charge is electrical energy transferred to an element to be converted into stored chemical energy.
• The cathode is the negative terminal of the battery.
• Compensatory charging is a method that uses direct current to bring the battery to a fully charged state and maintain it in this state.
• Cut-off voltage is the minimum voltage at which the battery is capable of delivering useful energy under certain discharge conditions.
• Open circuit voltage is the voltage at the external terminals of the battery in the absence of current draw.
• Rated voltage is the voltage across a fully charged battery when it is discharged at a very low rate.
• Float charge is a method of maintaining a rechargeable battery in a fully charged state by applying a selected constant voltage to compensate for various losses in it.
• Energy density is the ratio of the energy of an element to its mass or volume, expressed in Watt hours per unit mass or volume.
• Polarization is a voltage drop caused by changes in the chemical compositions of the components of the elements (the difference between the open circuit voltage and the voltage at any time during the discharge).
• Discharge is the consumption of electrical energy from an element into an external circuit. A deep discharge is a state in which almost the entire capacity of the element is used up. A shallow discharge is a discharge in which a small portion of the total capacity is consumed.
• Separator - a material used to isolate electrodes from each other. It sometimes retains electrolyte in dry cells.
• Shelf life is the period of time during which an element stored under normal conditions (20oC) retains 90% of its original capacity.
• Stability is the uniformity of voltage at which the battery releases energy during the full discharge mode.
• An element is a basic unit capable of converting chemical energy into electrical energy. It consists of positive and negative electrodes immersed in a common electrolyte.
• An electrode is a conductive material capable of producing current carriers when reacting with an electrolyte.
• Electrolyte is a material that conducts charge carriers in a cell.
• A cycle is one sequence of charging and discharging an element.

English terms

• A battery - incandescent battery
• acid storage battery - battery of acid (lead) batteries
• air battery - air-metal element
• alkaline battery - (primary) alkaline cell
• alkaline battery - alkaline manganese-zinc cell
• alkaline dry battery - dry mercury-zinc cell
• alkaline dry battery - dry alkaline cell
• alkaline manganese battery - alkaline manganese-zinc cell
• alkaline storage battery - alkaline battery
• alkaline storage battery - alkaline battery
• anode battery - anode battery
• B battery - anode battery
• Bansen battery - (nitric acid-zinc) Bunsen cell
• bag-type battery - cup (primary) element with a pupa
• balancing battery - buffer battery
• battery - battery
• bias battery - bias battery element, grid battery element
• biasing battery - bias battery, grid battery
• bichromate battery - (primary) cell with dichromate solution
• buffer battery - buffer battery
• bypass battery - buffer battery
• C battery - bias battery, grid battery
• Clark battery - (mercury-zinc) Clark cell
• cadmium normal battery - (mercury-cadmium) Weston normal cell
• cadmium-silver-oxide battery - cadmium oxide galvanic cell
• carbon battery - (primary) cell with a carbon electrode
• carbon-zinc battery - (dry) cell with a zinc anode and a carbon cathode
• cell - element, cell, galvanic cell (primary cell, battery or fuel cell)
• chemical battery - battery of chemical current sources
• chargeable battery - rechargeable element
• cooper-zinc battery - copper-zinc cell
• counter (electromotive) battery - counteracting element
• Daniel battery - (copper-zinc) Daniel cell
• decomposition battery - a cell with a (side) reaction of electrolytic decomposition
• dichromate battery - (primary) cell with dichromate solution
• displacement battery - a cell with a (side) electrolytic replacement reaction
• divalent silver oxide battery - a cell with oxidation of silver to the divalent state
• double-fluid battery - two-fluid element
• drum storage - nickel-zinc battery
• dry battery - dry cell
• dry battery - dry battery
• dry-charged battery - battery of dry-charged batteries
• dry-charged battery - dry-charged battery
• Edison battery - nickel-iron battery
• electric battery - galvanic battery (battery of primary cells, accumulators or fuel cells)
• electric battery - galvanic cell (primary cell), battery or fuel cell
• emergency batteries - emergency batteries
• emergency battery - emergency battery
• end batteries - spare batteries
• Faradey battery - Faraday cell
• Faure storage battery - battery with pasted plates
• filament battery - filament battery
• floating battery - spare battery (connected in parallel to the main battery)
• Grenet battery - (zinc dichromate) Grenet cell
• galvanic battery - electrochemical cell in galvanic cell mode
• grid battery - grid battery, displacement battery
• grid-bias battery - bias battery, grid battery
• Lalande battery - (alkaline copper zinc oxide) Lalande cell
• Leclanche battery - (manganese-zinc) Leclanche cell
• lead (-acid) battery - acid (lead) battery
• lead-acid (lead-storage) battery - battery of lead (acid) batteries
• lead-calcium battery - lead-calcium cell
• lead-dioxide primary battery - lead dioxide primary cell
• line battery - buffer battery
• lithium battery - a cell with a lithium anode
• lithium-iron sulfide secondary battery - iron-lithium chloride battery
• lithium-silver chromate battery - silver-lithium chromate cell
• lithium-water battery - lithium-water cell
• long wet-stand life battery - a battery of batteries with a long shelf life in a flooded state
• magnesium battery - primary cell with magnesium anode
• magnesium mercuric oxide battery - magnesium-oxide-mercury battery
• magnesium-cuprous chloride battery - copper-magnesium chloride cell
• magnesium-silver chloride battery - silver-magnesium chloride cell
• magnesium-water battery - magnesium-water battery
• mercury battery - (dry) mercury-zinc cell
• mercury battery - battery of (dry) mercury-zinc cells
• metal-air storage battery - metal air battery
• nicad (nickel-cadmium) battery - nickel-cadmium battery
• nickel-cadmium battery - nickel-cadmium battery
• nickel-iron battery - nickel-iron battery
• nickel-iron battery - nickel-iron battery
• Plante battery - lead (acid) battery with linen separator
• pilot battery - control battery battery
• plate battery - anode battery
• plug-in battery - replaceable battery
• portable battery - portable battery
• primary battery - (primary) element
• primary battery - battery of (primary) cells
• quiet battery - microphone battery
• Ruben battery - (dry) mercury-zinc cell
• rechargeable battery - battery of batteries
• rechargeable battery - battery of rechargeable elements
• reserve battery - galvanic cell of a reserve battery
• ringing battery - ringing (telephone) battery
• sal-ammoniac battery - (primary) cell with solutions of ammonium salts
• saturated standard battery - saturated normal cell
• sealed battery - sealed battery
• sealed battery - sealed (primary) element
• secondary battery - battery of batteries
• signaling battery - calling (telephone) battery
• silver-cadmium storage battery - battery of silver-cadmium batteries
• silver-oxide battery - (primary) cell with a silver cathode
• silver-zinc primary battery - silver-zinc primary cell
• silver-zinc storage battery - battery of silver-zinc batteries
• solar battery - solar battery
• standard Daniel battery - (copper-zinc) normal Daniel cell
• standby battery - emergency battery
• stationary battery - stationary battery storage battery - battery of batteries
• talking battery - microphone battery
• Voltaic battery - Volta element; element with metal electrodes and liquid electrolyte
• Weston (standard) battery - (mercury-cadmium) normal Weston cell
• wet battery - cell with liquid electrolyte
• zinc-air battery - battery of zinc air cells
• zinc-chlorine battery - zinc chlorine battery
• zinc-coper-oxide battery - copper-zinc oxide cell
• zinc-iron battery - zinc iron cell
• zinc-manganese dioxide battery - battery of manganese-zinc cells
• zinc-mercury-oxide battery - zinc-mercury oxide cell
• zinc-nickel battery - nickel-zinc battery
• zinc-silver-chloride primary battery - silver-zinc chloride primary cell

Introduction

Chemical current sources (CHS) have become a part of our lives for many years. In everyday life, the consumer rarely pays attention to the differences between the HIT used. For him, these are batteries and accumulators. They are typically used in devices such as flashlights, toys, radios or cars.

Most often, batteries and accumulators are distinguished by their appearance. But there are batteries that are designed in the same way as batteries. For example, the appearance of the KNG-1D battery differs little from the classic R6C AA batteries. And vice versa. Rechargeable batteries and disk-type batteries are also indistinguishable in appearance. For example, a D-0.55 battery and a push-button mercury cell (battery) RC-82.

In order to distinguish between them, the consumer must pay attention to the markings on the HIT body. The markings applied to the housings of batteries and accumulators are described in Chapters 1 and 2 in the figures and tables. This is necessary to correctly select the power supply for your device.

The emergence of portable audio, video and other more energy-intensive equipment required an increase in the energy intensity of HIT, their reliability and durability.

This book describes the technical characteristics and methods for selecting the optimal HIT, methods for charging, restoring, operating and extending the life of batteries and accumulators.

The reader is cautioned to note caution regarding the safety and disposal of chemical waste products.

In the case where the power consumption is relatively high (10Ah), batteries are used, mainly acid, as well as nickel-iron and nickel-cadmium. They are used in portable computers (Laptop, Notebook, Palmtop), wearable communications equipment, emergency lighting, etc.

Car batteries have a special place in the book. Diagrams of devices for charging and restoring batteries are provided, and new sealed batteries created using the “dryfit” technology that do not require maintenance for 5...8 years of operation are described. They do not have a harmful effect on people or equipment.

In recent years, such batteries have been widely used in backup power supplies for computers and electromechanical systems that accumulate energy for possible peak loads and emergency power supply of vital systems.

At the beginning of each chapter there is a glossary of special English terms that are used in the descriptions and labeling of batteries and accumulators. At the end of the book there is a consolidated dictionary of terms.

The main characteristics of CCIs for a wide range of applications that are of practical interest are given in Table B.1.

CHAPTER 1
GALVANIC CURRENT SOURCES, SINGLE ACTION

Disposable galvanic current sources are a unified container that contains an electrolyte, absorbed by the active material of the separator, and electrodes (anode and cathode), which is why they are called dry cells. This term is used to refer to all cells that do not contain a liquid electrolyte. Common dry cells include zinc-carbon or Leclanche cells.

Dry cells are used at low currents and intermittent operating modes. Therefore, such elements are widely used in telephones, toys, alarm systems, etc.

Since the range of devices that use dry elements is very wide and, in addition, they require periodic replacement, there are standards for their dimensions. It should be emphasized that the dimensions of the elements given in tables 1.1 and 1.2 produced by different manufacturers may differ slightly in terms of the location of the pins and other features specified in their specifications.

During the discharge process, the voltage of dry cells drops from the nominal voltage to the cut-off voltage (cut-off voltage is the minimum voltage at which the battery is capable of delivering minimum energy), i.e. typically 1.2V to 0.8V/cell depending on application. In the event of a discharge, when connected to a constant resistance element after closing the circuit, the voltage at its terminals sharply decreases to a certain value, slightly less than the original voltage. The current flowing in this case is called the initial discharge current.

The functionality of a dry cell depends on current consumption, cut-off voltage and discharge conditions. The efficiency of the element increases as the discharge current decreases. For dry cells, continuous discharge for less than 24 hours can be classified as high rate discharge.

The electrical capacity of a dry cell is specified for discharge through a fixed resistance at a given final voltage in hours depending on the initial discharge and is presented in a graph or table. It is advisable to use the manufacturer's chart or table for a specific battery. This is due not only to the need to take into account the features of the product, but also to the fact that each manufacturer gives its own recommendations on the best use of its products. Table 1.3 and Table 1.5 present the technical characteristics of galvanic cells that have recently been most common on the shelves of our stores.

The internal resistance of the battery may limit the current required, for example when used in a flash camera. The initial stable current that a battery can supply for a short time is called flash current. The designation of the element type contains letter designations that correspond to the flash currents and internal resistance of the element, measured at direct and alternating current (table 1.4). Flash current and internal resistance are very difficult to measure, and cells may have a long shelf life, but the flash current may decrease.

1.1. TYPES OF GALVANIC CELLS

Carbon-zinc elements

Carbon-zinc elements (manganese-zinc) are the most common dry elements. Carbon-zinc cells use a passive (carbon) current collector in contact with a manganese dioxide (MnO2) anode, an ammonium chloride electrolyte and a zinc cathode. The electrolyte is in a paste form or impregnates the porous diaphragm. Such an electrolyte is slightly mobile and does not spread, which is why the elements are called dry.

The rated voltage of the carbon-zinc cell is 1.5 V.

Dry elements can have a cylindrical shape, Fig. 1.1, a disk shape, Fig. 1.2, and a rectangular shape. The design of rectangular elements is similar to disk ones. The zinc anode is made in the form of a cylindrical glass, which is also a container. Disc elements consist of a zinc plate, a cardboard diaphragm impregnated with an electrolyte solution, and a compressed layer of the positive electrode. The disk elements are connected in series with each other, the resulting battery is insulated and packaged in a case.

Coal-zinc elements are “restored” during a break in operation. This phenomenon is due to the gradual alignment of local inhomogeneities in the electrolyte composition that arise during the discharge process. As a result of periodic “rest”, the service life of the element is extended.

In Fig. Figure 1.3 presents a three-dimensional diagram showing the increase in the operating time of a D-element when using an intermittent operating mode compared to a constant one. This should be taken into account when using the elements intensively (and use several sets for operation so that one set has a sufficient period of time to restore functionality. For example, when using a player, it is not recommended to use one set of batteries for more than two hours in a row. When changing two sets, the operating time elements increases threefold.

The advantage of carbon-zinc elements is their relatively low cost. Significant disadvantages include a significant decrease in voltage during discharge, low power density (5...10 W/kg) and short shelf life.

Low temperatures reduce the efficiency of using galvanic cells, and internal heating of the battery increases it. The effect of temperature on the capacitance of a galvanic cell is shown in Fig. 1.4. 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 cells and carbon-zinc cells is the use of an alkaline electrolyte, as a result of which there is virtually no gas evolution during discharge, and they can be made hermetically sealed, which is very important for a number of their applications.

The voltage of alkaline cells is approximately 0.1 V less than that of carbon-zinc cells under the same conditions. Therefore, these elements are interchangeable.

The voltage of cells with an alkaline electrolyte changes significantly less than that of cells with a salt electrolyte. Cells with alkaline electrolyte also have higher specific energy (65...90 Wh/kg), specific power (100...150 kWh/m3) and a longer shelf life.

Charging of manganese-zinc cells and batteries is carried out by asymmetric alternating current. You can charge cells with a salt or alkaline electrolyte of any concentration, but not too discharged and without damaged zinc electrodes. Within the expiration date established for a given type of cell or battery, it is possible to restore functionality multiple times (6...8 times).

Charging of dry batteries and cells is carried out from a special device that allows you to obtain a charging current of the required form: with a ratio of charging and discharging components of 10:1 and a ratio of pulse durations of these components of 1:2. This device allows you to charge watch batteries and activate old small batteries. When charging watch batteries, the charging current should not exceed 2 mA. Charging time is no more than 5 hours. The diagram of such a device for charging batteries is shown in Fig. 1.5.

Here, the battery being charged is connected through two parallel-connected chains of diodes with resistors. The asymmetric charge current is obtained as a result of the difference in the resistances of the resistors. The end of the charge is determined by the cessation of voltage growth on the battery. The voltage of the secondary winding of the charger transformer is selected so that the output voltage exceeds the rated voltage of the element by 50...60%.

The battery charging time using the described device should be about 12...16 hours. The charging capacity should be approximately 50% greater than the rated battery capacity.

Mercury elements

Mercury elements are very similar to alkaline elements. They use mercury oxide (HgO). The cathode consists of a mixture of zinc powder and mercury. The anode and cathode are separated by a separator and a diaphragm impregnated with a 40% alkali solution.

These items have longer shelf life and higher capacities (for the same volume). The voltage of a mercury cell is approximately 0.15 V lower than that of an alkaline cell.

Mercury elements are characterized by high specific energy (90...120 Wh/kg, 300...400 kWh/m3), voltage stability and high mechanical strength.

For small-sized devices, modernized elements of the RC-31S, RC-33S and RC-55US types have been created. The specific energy of the RC-31S and RC-55US elements is 600 kWh/m3, the RC-33S elements are 700 kWh/m3. RC-31S and RC-33S elements are used to power watches and other equipment. RC-55US elements are intended for medical equipment, in particular for implantable medical devices.

The RC-31S and RC-33S elements operate for 1.5 years at currents of 10 and 18 µA, respectively, and the RC-55US element ensures the operation of implanted medical devices for 5 years. As follows from Table 1.6, the nominal capacity of these elements does not correspond to their designation.

Mercury elements are operational in the temperature range from 0 to +50oC; there are cold-resistant RC-83X and RC-85U and heat-resistant elements RC-82T and RC-84, which are capable of operating at temperatures up to +70oC. There are modifications of the elements in which indium and titanium alloys are used instead of zinc powder (negative electrode).

Because mercury is scarce and toxic, mercury cells should not be discarded after they are fully used. They must be recycled.

Silver elements

They have “silver” cathodes made of Ag2O and AgO. Their voltage is 0.2 V higher than that of carbon-zinc ones under comparable conditions.

Lithium cells

They use lithium anodes, an organic electrolyte and cathodes made of various materials. They have a very long shelf life, high energy densities and are operational in a wide temperature range, since they do not contain water.

Since lithium has the highest negative potential in relation to all metals, lithium cells are characterized by the highest rated voltage with minimal dimensions (Fig. 1.6). Technical characteristics of lithium galvanic cells are given in Table 1.7.

Organic compounds are usually used as solvents in such elements. Solvents can also be inorganic compounds, for example, SOCl2, which are also reactive substances.

Ionic conductivity is ensured by introducing salts with large anions into solvents, for example: LiAlCl4, LiClO4, LiBFO4. The specific electrical conductivity of non-aqueous electrolyte solutions is 1...2 orders of magnitude lower than the conductivity of aqueous solutions. In addition, cathodic processes in them usually proceed slowly, therefore, in cells with non-aqueous electrolytes, current densities are low.

The disadvantages of lithium cells include their relatively high cost, due to the high price of lithium and special requirements for their production (the need for an inert atmosphere, purification of non-aqueous solvents). It should also be taken into account that some lithium cells are explosive if opened.

Such elements are usually made in a push-button design with a voltage of 1.5 V and 3 V. They successfully provide power to circuits with a consumption of about 30 μA in constant mode or 100 μA in intermittent modes. Lithium cells are widely used in backup power supplies for memory circuits, measuring instruments and other high-tech systems.

CHAPTER 1.2 BATTERIES FROM LEADING COMPANIES OF THE WORLD

In recent decades, the production volume of alkaline analogues of Leclanche elements, including zinc air, has increased (see Table B1).

For example, in Europe, the production of alkali manganese-zinc elements began to develop in 1980, and in 1983 it already reached 15% of total output.

The use of free electrolyte limits the possibilities of using autonomous ones and is mainly used in stationary HIT. Therefore, numerous studies are aimed at creating so-called dry cells, or cells with thickened electrolyte, free from elements such as mercury and cadmium, which pose serious dangers to human health and the environment.

This trend is a consequence of the advantages of alkaline chemicals in comparison with classical salt elements:

a significant increase in discharge current densities due to the use of a pasted anode;

increasing the capacity of chemical heating equipment due to the possibility of increasing the loading of active masses;

creation of zinc air compositions (elements of type 6F22) due to the greater activity of existing cathode materials in the electroreduction reaction of dioxygen in an alkaline electrolyte.

Batteries from Duracell (USA)

Duracell is a recognized leader in the world in the production of disposable alkaline galvanic sources. The history of the company goes back more than 40 years.

The company itself is located in the United States of America. In Europe, its factories are located in Belgium. According to consumers both here and abroad, Duracell batteries occupy a leading position in popularity, duration of use and price-quality ratio.

The appearance of Duracell on the Ukrainian market attracted the attention of our consumers.

The discharge current densities in lithium sources are not high (compared to other HITs), on the order of 1 mA/cm2 (see page 14). With a guaranteed shelf life of 10 years and low current discharge, it is rational to use Duracell lithium cells in high-tech systems.

US-patented EXRA-POWER technology using titanium dioxide (TiO2) and other technological features helps increase the power and efficiency of Duracell manganese-zinc chemical reactors.

Inside the steel body of Duracell alkaline cells is a cylindrical graphite collector that holds a paste-like electrolyte in contact with a needle cathode.

The guaranteed shelf life of the elements is 5 years, and at the same time, the capacity of the element indicated on the packaging is guaranteed at the end of the shelf life.

Technical characteristics of Duracell HIT are given in Table 1.8.

Batteries from Varta concern (Germany)

The Varta concern is one of the world leaders in the production of HIT. The concern's 25 factories are located in more than 100 countries around the world and produce more than 1,000 types of batteries and accumulators.

The main production facilities are occupied by the Department of Stationary Industrial Batteries. However, about 600 types of voltaic cells from watch batteries to sealed batteries are produced at the concern's factories by the Instrument Batteries Department in the USA, Italy, Japan, the Czech Republic, etc., with a guarantee of constant quality regardless of the geographical location of the plant. The photographic camera of the first man to set foot on the Moon was powered by Varta batteries.

They are quite well known to our consumers and are in steady demand.

Technical characteristics of HIT of the Varta concern, indicating domestic analogues, are given in Table 1.9.

CHAPTER 2. BATTERIES

Batteries are reusable chemical sources of electrical energy. They consist of two electrodes (positive and negative), an electrolyte and a housing. Energy accumulation in the battery occurs during a chemical reaction of oxidation-reduction of the electrodes. When the battery is discharged, the reverse processes occur. Battery voltage is the potential difference between the poles of the battery at a fixed load.

Bibliography

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