Constructions of various types of batteries (primary power sources)

Content

1 Cylindrical batteries
1.1 the Purpose of the structural elements
1.2 Positive electrode
1.3 Negative electrode
1.4 Electrolyte
2 Disk batteries
2.1 Manganese-zinc salt
2.2 Manganese-zinc alkaline
2.3 Zinc Mercury
2.4 Silver-zinc
2.5 Lithium
2.6 Air Zinc

CYLINDRICAL BATTERIES

As an example, take a manganese-zinc salt battery of medium capacity of a cylindrical shape. Such batteries are the simplest in design and manufacturing technology. The body is made of zinc and at the same time is the negative pole of the current source. Inside there is an agglomerate - a briquette of compressed mixture of reagents involved in the reduction reaction on the positive electrode. More on this reaction is described in the article “The difference of electrode potentials - the possibility of a battery”. In the center of the briquette is a graphite rod, which is the positive pole of the current source. The electrochemical reaction proceeds between zinc and the substance of the briquette, manganese oxide with additives. More about this process is described in the article “Chemical reaction - source of emf”. The briquette is separated from the bottom of the zinc cup by an insulator.

The main elements of the design of obsolete batteries.

In batteries, assembled by outdated technology, the sinter was wrapped in a thin fabric and tied with thread. The collected briquette is called a doll. Electrolyte is poured into the space between the glass and the pupa. After short-term heating of the electrolyte under the action of special additives turns into a paste. Now, batteries are made in this way for use in high current mode. Zinc glass, which is also the body, is inserted in a cardboard casing with printed markings.

The design of the battery in a steel case, made by printed technology.

1 - insulator;
2 - zinc cup, which is a negative electrode;
3 - the outer casing of thin steel;
4 - insulator;
5 - graphite rod (topootvot);
6 - agglomerate;
7 - electrolyte;
8 - empty space;
9 - gaskets;
10 - sealing substance;
11 - cover;
12 - insulator;
13 - positive pole contact;
14 - porous separating cup (diaphragm).

In the cylindrical elements of a later design, inside the zinc cup is a porous separating cup 14. Between the separating and zinc cups there is an electrolyte in the form of a paste. At the top of the battery there is a free space 8, between the gasket 9 and the agglomerate. Empty volume is used for the accumulation of gases released by the reaction. The top of the battery is covered with a layer of a gas impermeable substance 10 . On the protruding part of the graphite electrode is put on the metal contact 13 in the form of a cap. In modern batteries, instead of a cardboard shell, a zinc cup is enclosed in an outer case 3, made of thin steel. An insulator 4 is installed between the zinc cup and the outer metal housing . Gaskets 9 isolate the case from the cover and seal the battery. An agglomerate is freely inserted inside the porous separation cylinder 14. After assembly, the agglomerate is pressed a little on top. As a result of pressing, the diaphragm approaches the glass. Such battery assembly methods are called tamping technology. The electrolyte gap is reduced to fractions of a millimeter, which made it possible to increase the amount of manganese oxide to increase the battery capacity.

PURPOSE OF CONSTRUCTION ELEMENTS

When the load is connected to the battery inside the zinc cup, an electrochemical reaction begins. Zinc gradually dissolves in the electrolyte in the form of positive ions moving towards the graphite rod. In the process of battery operation, the wall thickness of the zinc cup is reduced. Holes may form, causing electrolyte to leak and battery-powered appliances to deteriorate. To prevent electrolyte leakage, starch and special additives are added to it, which convert the liquid electrolyte into a paste. Also, to prevent battery leakage, the zinc cup is enclosed in a steel case. When the reaction near the positive electrode produces hydrogen, this phenomenon is called polarization. To prevent the accumulation of hydrogen around the graphite rod are substances that prevent polarization. The fabric surrounding the agglomerate in the design of old batteries and the porous separating cup between the electrolyte and the agglomerate in modern batteries are impregnated with electrolytes, which allows ions to pass unhindered through the separating diaphragms. The positive electrode involved in the electrochemical reaction is manganese dioxide powder mixed with carbon particles. Zinc ions, moving through the electrolyte to the graphite electrode, react with manganese compounds, resulting in various chemical compounds with the participation of electrons entering the battery through a graphite electrode, which is both a current conductor and a reaction catalyst. The main advantages of such batteries are tightness and extended shelf life. The design with a separating porous glass and an additional external steel body has won the market, despite the complexity and increased cost.

POSITIVE ELECTRODE

The electric current is a consequence of the electrochemical reaction that takes place on the surface of the electrodes. The positive electrode is a mixture of manganese oxide and graphite or acetylene black. Manganese oxide is involved in the reaction, giving away electrons coming to the graphite rod located inside the mixture of manganese oxide and graphite, which reduces the resistance of the mixture. Graphite is also a catalyst for the reaction. In more modern models of batteries, the positive pole is made of brass.

The batteries use several varieties of manganese oxide occurring in the form of ore: cryptomelane, pyrolusite, ramsedelite, and others. The greatest value for the production of batteries have deposits of pyrolusite. The enriched ore provides an acceptable element storage time. Graphite additives increase the hygroscopicity of the active mixture and keep the electrolyte close to particles of manganese oxide. Up to 20% graphite is added to batteries designed to operate in high current mode. The minimum of additives is brought in the batteries intended for work in the mode of small currents and calculated for long storage.

NEGATIVE ELECTRODE

For the manufacture of a negative electrode of cylindrical batteries, which is also the main structural element, zinc is used, containing impurities of no more than 0.06%. High purity zinc reduces corrosion. Some zinc or lead is present in zinc to reduce the formation of hydrogen. Lead is added to the metal of the negative electrode cup to increase manufacturability.

Pasty electrolyte is poured between a zinc cup and a porous separating cup.

The electrolyte is a mixture of an aqueous solution of zinc chloride and ammonia. The mixture includes flour or starch to impart a thick paste. Ammonia and zinc chloride are involved in secondary reactions and thus largely determine the nature of the passing reaction. Increasing the content of ammonia increases conductivity, but zinc corrosion accelerates. Therefore, the safety of batteries with a high content of ammonia below. Zinc chloride strongly affects the properties of electrolytes, thickened with flour or starch - in the presence of zinc chloride, the electrolyte thickens much faster. In addition, zinc chloride prevents the development of microbes.

To reduce the operating temperature of the battery, calcium chloride or lithium chloride is added to the electrolyte. For the saturation of the agglomerates and diaphragms usually use different compositions. Mercury chloride is injected into electrolytes in contact with the zinc electrode to reduce self-discharge. Mercury is deposited on the surface of zinc. For the same purpose, small amounts of potassium compounds are sometimes added to the electrolyte, also preventing the destruction of zinc. Chromic alum or chromium sulphate is added to some electrolytes to prevent the thickened electrolyte from liquefying at elevated temperatures.

DISK BATTERIES

The most popular small-sized batteries, made in the body in the form of a disk. Due to their small size and weight, they are indispensable in wristwatches, hearing aids, various gadgets and other small-sized equipment.

Manganese-zinc salt

Manganese-zinc saline disk batteries are most often used as a group of several pieces, combined into a larger battery, where the elements are placed vertically one above the other with respect to the polarity of the installation. Batteries collected from disk elements have a large specific capacity and energy. They use less zinc compared to cylindrical batteries, in which zinc is used as an active and constructive material, and in disk batteries, zinc is only as an active material of the negative electrode. In the battery consisting of several elements - biscuit, the use of zinc per unit capacity is reduced three times, since zinc is not included in the design and can be completely dissolved during the reaction.

Disc battery design

1 - zinc plate, which is a negative electrode;
2 - agglomerate, positive electrode;
3 - aperture;
4 - insulator;
5 - waterproof conductive layer;
6 - sealing ring.

The battery consists of: negative 1 and positive 2 electrodes, insulated with thin paper 4 preventing the destruction of the active mass. The structure includes a diaphragm 3 with electrolyte paste pressed to the zinc electrode 1. Diaphragm 3 is saturated with electrolyte. A layer 5 is applied to the outer side of the zinc plate 1, which simultaneously has the properties of a current conductor and protection against moisture, consisting of a polymer with graphite. The structural elements are tightened by means of an insulating ring 6, which ensures the contact of parts and tightness.

MANGANESE-ZINC ALKALINE

Manganese-zinc alkaline batteries are used as a separate independent battery of devices. Weaknesses of manganese-zinc salt batteries were corrected in manganese-zinc alkaline. They have several times increased capacity, increased tightness, increased strength of sealing gaskets. Due to the decrease in the internal resistance of the battery, the discharge current is increased.

Mercury-zinc

The steel case covers the mixture of positive electrode substances. The zinc powder of the negative electrode is enclosed in a steel lid, covered from the inside with tin. Between the electrodes are several layers of the diaphragm saturated with electrolyte. The tightness of the battery is achieved through the use of a special gasket that lets in hydrogen that is formed due to zinc corrosion. Mercury oxide is added to the zinc powder to prevent hydrogen accumulation after discharge. Battery performance due to the amount of zinc contained in it.

SILVER-ZINC

The design resembles mercury-zinc batteries. The reliability of the tightness of the case has increased thanks to a special insulating ring. Zinc and mercury are components of the negative electrode. The mixture is laid in a gold-plated or tin-coated steel lid. The positive electrode reagents are silver oxide, a small amount of graphite and some additives pressed into a nickel-plated steel case. Between the electrodes there is a porous diaphragm saturated with electrolyte - a solution of potassium or sodium hydroxide with a small content of zinc oxide. Sodium hydroxide solution is used in batteries designed for small currents.

Lithium battery in standard case.

The design of lithium batteries differs from others in the highest airtightness. The slightest violation of the case leads to damage to the battery and may even lead to a fire or explosion. Therefore, the production technology contains complex operations of combining dissimilar materials. At the time of appearance on the market of lithium batteries, they were produced in standard cases. If you install a 3 volt lithium battery instead of a standard 1.5 volt battery if it is installed incorrectly, this will damage the powered device.

Lithium batteries for PCB mounting.

To eliminate errors in the installation of batteries, more and more manufacturers are moving to new design standards. The positive electrode of a lithium battery consists of a conductor, made in the form of a grid, grid, solid or porous plate. On the conductor conductor are the reagents of the positive electrode. As a binding agent for active substances in a lithium battery, fluorinated polymers are most often used. The electrodes of the battery are separated by a diaphragm.

AIR ZINC

The sealing sticker is removed before use.

Batteries with oxygen depolarization are easily recognizable by the sealing sticker removed before starting work. Their work is based on the interaction of zinc, air and potassium hydroxide, manganese oxide and hydroxide. The basis of the differences from the processes in other types of batteries is the oxidation of manganese hydroxide by oxygen in air, which is formed during the operation of the battery to manganese oxide, which is the substance of the positive electrode. The interaction with oxygen of the reaction products of the positive electrode allows them to be converted into a chemical compound, which is the main substance of the reduction reaction. Free air access to positive electrode chemicals increases the capacity of the cell. The soot and graphite used in the agglomerates is able to be saturated with oxygen and work as oxygen electrodes.

The design of the air-zinc disc batteries.

The battery has a complex structure. The positive electrode has a two-layer structure consisting of a nickel grid, a teflon film, a mixture of reagents with manganese oxide, carbon black and activated carbon. Air enters the battery through the hole in the contact of the positive pole and is evenly distributed using a special scattering layer. At the same time, air supply and protection of devices against electrolyte leakage from the battery is ensured thanks to the use of a special porous teflon film. Paraffin or polyethylene is introduced into the outer layer to protect against electrolyte leakage. The negative electrode is a mixture of high-purity powdered zinc, an electrolyte and a corrosion inhibitor. The electrodes are separated by a thickened electrolyte containing potassium hydroxide, zinc oxide, and a starch or flour thickener.

The protective sticker is a kind of accelerator that controls the battery. In the sealed state of the battery can be stored for several years. After removing the protective film in the battery, the reaction begins, as a result of which the active substances are consumed within a month and then the battery becomes unusable. To increase the battery life, you need to wait five minutes between removing the sealing sticker and turning on the battery as part of the device.

In the air-zinc batteries there are no mercury impurities, which made it possible to free up more volume for the zinc mixture and to increase the operation life several times as compared with batteries containing an alkaline electrolyte. In the mode of low currents, the batteries work predominantly as air, if the current consumption increases, the battery goes into recovery mode manganese oxide. The ability to evenly charge is an important feature of this type of battery.