Opening accumulating effect is one of the most important and the most significant inventions in the field of electrical engineering. Often, there arises the need to feed the electricity appliances or equipment in a place where there are no sources of energy. For a long time for these purposes using galvanic battery, but it was weak, expensive and overly bulky power source. Creating an electric battery has greatly simplified this task.
Even in 1802, Ritter discovered that two copper plates dipped in acid and connected to the galvanic battery, charged and then can be used as a constant current source for a short time. This phenomenon later studied by many other scientists. In 1854, a German military doctor William Zinsteden observed following effect: when a current is passed through the lead electrodes that are immersed in dilute sulfuric acid, the positive electrode was covered with lead dioxide of PbO2, while the negative electrode is not subjected to any changes. If such an element and then closed the circuit, stopping current passing through it from the DC source, the constant current appeared in it, which was detected as long as the entire lead dioxide does not dissolve in acid. Thus, Zinsteden getting closer to the creation of the battery, but it made no practical conclusions from his observations.
Only five years later, in 1859, French engineer Gaston Plante accidentally made the same discovery and built a lead battery first in history. This was the beginning of the storage equipment.
Plante battery consisted of two identical lead plates wound on a wooden cylinder. From each other, they separated the tissue lining. Arranged in this way the device was placed in a vessel with acidic water, and connected to an electrical battery. A few hours later, remove the batteries, you can shoot with the battery sufficiently strong current that kept its constant value for some time.
What explains the processes occurring in the battery? As in the electrochemical cell, the electric current here - a consequence of a chemical reaction, which can occur several times in both directions. Imagine that we begin charging the battery discharge by connecting it to a DC power source. Usually not yet charged the mass of the positive lead plate comprises, on remnants of the previous cycle - lead oxide PbO and lead sulfate PbSO4, and the negative - only the lead oxide PbO. Under the influence of an electric current electrolyte - acidified water - it begins to decompose: on the positive electrode, oxygen, which immediately oxidizes lead oxide and lead sulphate to peroxide PbO2 (SO4 and the acidic residue goes into solution), and hydrogen is released on the negative plate. Last connected oxide with oxygen to form metallic lead and water. Then, gas begins to accumulate in the pores of the lead plate.
If a charged battery is included in the circuit, the current passes through the battery during charging, changes its direction. As a result, on the plate, where once stood the oxygen starts to release hydrogen, which reacts with oxygen peroxide lead. On the other plate is released oxygen. Sulfuric acid from the liquid moves to the positive electrode and the lead sulphate forms a back, whereas hydrogen and lead on the negative plate are oxidized, the first - the water, the second - in lead oxide. In a somewhat simplified form (without parallel processes) chemical discharge reaction is:
PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O.
When charging, the phenomenon goes in the opposite direction. This reaction is accompanied by the release of electric current continues as long as the amount of lead oxide on both plates is not balanced. The same reaction occurs in the open battery, but much slower. When charged (acidic due to the evolution of the residue in a solution), the specific weight of the liquid in the accumulator increases and when negative pressure - reduced (as sulfuric acid by suction is connected to the lead oxide to form lead sulphate at the electrodes). During discharge the energy of chemical reactions is converted into electrical energy, and during charging - on the contrary.
A major shortcoming of Plante battery was its small capacity - it is too quickly consumed. Plante soon remarked that the capacity can be increased special surface preparation of lead plates that must be possible to more porous. To achieve this, Plante discharged a charged battery, and then again passed through it current, but in the opposite direction. This process was repeated molding plates repeatedly for about 500 hours and was intended to enlarge both plates a layer of lead oxide.
Until then, it has not yet been invented dynamo, batteries for electrical engineers were of little interest, but when the opportunity to quickly and easily charge them with the help of a generator, batteries have received the widest dissemination. In 1882, Camille Faure greatly improved the technique of manufacture of battery plates. If the battery Plante started to work well only after repeated charge and discharge (until the plate is not made porous), the battery plates Fora formation occurred much faster. The essence of the improvements handicap was that he invented to cover each plate with red lead or other lead oxide. When charging the layer of this substance on one of the plates was converted to peroxide, whereas in the other plate was obtained due to the low degree of reaction of the oxide. During both of these processes on wafers formed with a porous layer of oxides of structure that promoted the accumulation of gases evolved at the electrodes. To the mass of oxides formed on the plates, not fell off, they were covered with a cloth. Faure battery is not only charge the battery faster Plante, but also had a significantly higher capacity and can give a very strong current. It consisted of parallel lead plates, placed close to one another and connected through one, so that each electrode is a plate placed between two opposite electrodes.
The invention Fora immediately drew the attention of electricians. German banker Volkmar, who took up the production of batteries Fora, soon even improved them. The previous layer of oxide batteries, as already mentioned, poorly kept on the grid and shake easily falls off. This was a serious flaw in the design, because the hurt used batteries in transport. To improve matters, suggested Volkmar lead plates do not continuous but in the form of grids, the holes of which stuffed spongy lead. In these gratings active mass is no longer simply adhere to the lead, and is firmly held in the cells.
At the beginning of the XX century the improvement of the battery was engaged Edison, who wanted to make it more suitable for the needs of transport. In connection with this problem needed to ease the weight of the batteries, to increase their capacity to get rid of poisonous lead and corrosive sulfuric acid, which rapidly corrode lead plates, after which they had to be replaced.
As usual, Edison went to work on a large scale: it has created a special laboratory with a large staff of chemists and instructed them to research on all these fronts. In fact, it was the creation of an entirely new type of battery in which the electrolyte is a caustic, and the negative electrode - milled iron with some impurities. For a long time it was not possible to select the material for the positive electrode. Since the chemical processes in the alkaline battery were very complex and not well understood, I had to walk literally groping. In experimental models, a positive electrode made of carbon, the pores of which are filled with various substances: have tried a lot of metals and their compounds, but they gave enough good result. Finally we settled on nickel, which proved to be the most appropriate. Since Edison came to the iron-nickel batteries with the electrolyte in the form of potassium hydroxide. (Chemical reactions occurring during the discharge in an alkaline battery, in a somewhat simplified form described by the equation:
2NiOOH + Fe + 2H2O = 2Ni (OH) 2 + Fe (OH) 2;
Charging process goes in the opposite direction; electrolyte is KOH, and even provides the necessary environment for the reaction is not involved.)
several of these batteries for extensive tests were made, and then the researchers were disappointed - the battery capacity is very small. Edison noticed that the purity of the material is of great importance to increase capacity. He ordered for the Canadian high-grade nickel samples, after which the battery capacity immediately tripled. a small factory for refining (cleaning) iron and nickel was built in West ORANGE. new battery capacity is 2, 5 times larger than that of the old lead. Edison claimed that the biggest progress in battery technology since its inception.
Further experiments were so successful that in 1903, Edison decided to start industrial production of their batteries on a specially built for this plant. However, the first alkaline batteries, available for sale, were very far from perfect: they do not hold a predetermined voltage value, often leak and had a lot of other small defects. From distributors began receiving numerous complaints. Edison had to stop the plant and re-engage in the improvement of his invention. Despite the setbacks, he continued to firmly believe in the success of business. Lapping was assigned to multiple groups, one working on the improvement of welding storage vessels, the other - on the refining of iron, nickel and the third dealt with additives to it. By 1905, it was carried out more than 10 thousand additional experiments, and in 1910 significantly improved the battery again went into production. In the first year of production it was released on $ 1 million, and all she found a good sale. Soon a new laptop battery is widely used in transport, power stations, ships and small submarines.