Whether or not the ancestors who made this clay bottle knew about static electricity, what is certain is that the ancient Greeks definitely knew it. They knew that if they rubbed a piece of amber, it would attract light objects. Aristotle also knew of a magnet, an ore with a strong magnetic force that attracts iron and metals.
One day in 1780, when the Italian anatomist Galvani was dissecting a frog, he held different metal instruments in both hands and accidentally touched the frog's thigh at the same time. The muscles of the frog's leg immediately It twitched, as if it was stimulated by electric current, but only touching the frog with a metal instrument had no such reaction. Galvani believed that this phenomenon occurred because of a kind of electricity generated inside the animal's body, which he called "bioelectricity." Galvani wrote a paper on this experimental result in 1791 and published it in the academic world.
Gavani’s discovery aroused great interest among physicists. They rushed to repeat Galvani’s experiment in an attempt to find a way to generate electric current. After many experiments, Italian physicist Volta It is believed that Galvani's theory of "bioelectricity" is not correct. The reason why frog muscles can generate electric current is probably due to the action of some kind of liquid in the muscles. To prove his point, Volta tested two different metal pieces by immersing them in various solutions. It was found that as long as one of the two metal pieces reacts chemically with the solution, an electric current can be generated between the metal pieces.
In 1799, Volta immersed a zinc plate and a silver plate in salt water and found that there was an electric current flowing through the wires connecting the two metals. So he put flannel or paper soaked in salt water between many zinc and silver sheets and stacked them flat. When you touch both ends with your hands, you will feel strong current stimulation. Volta used this method to successfully create the world's first battery - the "Volt stack". This "volt stack" is actually a battery pack connected in series. It became the source of power for early electrical experiments and the telegraph machine.
The Italian physicist Volta repeated Galvani's experiment many times. As a physicist, his attention was mainly focused on the two metals, not on the frog's nerves. Regarding the twitching phenomenon of frog legs discovered by Galvani, he thought it might be related to electricity, but he believed that electricity did not exist in the muscles and nerves of frogs. He speculated that the flow of electricity might be caused by the contact of two different metals. occurs regardless of whether the metal comes into contact with live or dead animals. Experiments have shown that as long as the two metal pieces are separated by cardboard, linen, leather or other sponge-like things soaked in salt or alkaline water (even as long as they are wet) (he believes that this is necessary to make the experiment successful) ), and connect the two metal pieces with a metal wire. Regardless of whether there are frog muscles or not, current will flow through. This shows that electricity is not generated from the frog's tissues, and that the frog's legs function only as a very sensitive electroscope.
In 1836, Daniel of England improved the "voltaic pile". He used dilute sulfuric acid as the electrolyte to solve the battery polarization problem and created the first zinc-copper battery that was non-polarized and could maintain a balanced current, also known as the "Daniel battery." Since then, "Bunsen batteries" and "Grove batteries" with better depolarization effects have been introduced. However, these batteries have the problem that their voltage drops over time.
In 1860, Planté of France invented a battery using lead as the electrode. The unique feature of this kind of battery is that when the battery voltage drops after being used for a period of time, a reverse current can be passed through it to make the battery voltage rise again. Because this kind of battery can be recharged and can be used repeatedly, it is called a "storage battery".
However, no matter what kind of battery, a liquid needs to be filled between two metal plates, so it is very inconvenient to transport. Especially the liquid used in the battery is sulfuric acid, which is very dangerous when moving.
In 1887, Englishman Helleson invented the earliest dry battery. The electrolyte of dry batteries is in the form of paste, does not leak, and is easy to carry, so it is widely used.
A device that directly converts chemical energy, light energy, thermal energy, nuclear energy, etc. into electrical energy.
There are chemical batteries, solar cells, thermoelectric batteries, nuclear batteries, etc. The battery usually refers to a chemical battery.
The performance parameters of the battery mainly include electromotive force, capacity, specific energy and resistance. The electromotive force is equal to the work done by the non-electrostatic force (chemical force) of the battery when a unit positive charge moves from the negative electrode to the positive electrode through the interior of the battery. The electromotive force depends on the chemistry of the electrode material and has nothing to do with the size of the battery. The total amount of charge that a battery can output is the battery's capacity, usually measured in ampere hours. In a battery reaction, the electrical energy produced by 1 kilogram of reaction material is called the theoretical specific energy of the battery. The actual specific energy of the battery is smaller than the theoretical specific energy. Because the reactants in the battery do not all proceed according to the battery reaction, and the internal resistance of the battery also causes electromotive force drop, therefore batteries with high specific energy are often called high-energy batteries. The larger the battery area, the smaller its internal resistance.
There are many types of batteries. Commonly used batteries are mainly dry batteries, storage batteries, and small micro batteries. In addition, there are metal-air batteries, fuel cells and other energy conversion batteries such as solar cells, thermoelectric batteries, nuclear batteries, etc.
Dry cell battery is one of the most widely used chemical batteries. In 1865, the Frenchman Leclanché developed a wet battery of carbon/manganese dioxide/ammonium chloride solution/zinc system based on the voltaic battery. After development, there are more than 100 types of dry batteries. In addition to zinc-manganese dry batteries, there are also magnesium-manganese dry batteries, zinc-mercury oxide dry batteries, zinc-silver oxide dry batteries, etc. Since the reversibility of the oxidation and reduction reactions of dry batteries is very poor, charging methods generally cannot be used to restore the positive and negative active materials to their original states after use. Therefore, dry batteries are also called primary batteries. The most commonly used dry batteries are zinc-manganese dry batteries, which are available in paste type, cardboard type, alkaline type and laminated type.
Paste zinc-manganese dry battery consists of zinc cylinder, electric paste layer, manganese dioxide positive electrode, carbon rod, copper cap, etc. The outermost layer is a zinc cylinder, which is both the negative pole of the battery and also serves as a container. It will be gradually dissolved during the discharge process; in the center is a carbon rod that acts as a current collector; tightly Surrounding the carbon rod is a mixture of dark brown or black manganese dioxide powder and a conductive material (graphite or acetylene black). Together with the carbon rod, it forms the positive electrode of the battery and also It's called charcoal buns. To avoid evaporation of water, the upper part of the dry cell is sealed with paraffin or asphalt. The electrode reaction of the zinc-manganese dry battery when working is zinc electrode: Zn→Zn2 +2e
Carbon electrode:
Cardboard zinc-manganese dry battery is based on the paste zinc-manganese dry battery Improved. It is based on high-quality kraft paper with a thickness of 70 to 100 microns and does not contain metal impurities. The surface is coated with a prepared paste, and then dried to make cardboard to replace the paste in paste zinc-manganese dry batteries. electrolyte layer. The actual discharge capacity of cardboard zinc-manganese dry batteries is 2 to 3 times higher than that of ordinary paste zinc-manganese dry batteries. Most dry batteries labeled "high performance" are cardboard type.
The electrolyte of alkaline zinc-manganese dry battery is gelatinized from amalgamated zinc powder, 35% potassium hydroxide solution and some sodium carboxymethylcellulose. Since the potassium hydroxide solution has a low freezing point and small internal resistance, alkaline zinc-manganese dry batteries can operate at a temperature of -20°C and can discharge at high currents. Alkaline zinc-manganese dry batteries can be charged and discharged more than 40 times, but they cannot be deeply discharged before charging (retaining 60% to 70% of the capacity), and the charging current and voltage at the end of the charging period need to be strictly controlled.
Stacked zinc-manganese dry batteries are composed of several compact flat single cells stacked together. Each single cell is composed of a plastic casing, zinc skin, conductive film, separator paper, and carbon cake (positive electrode). The diaphragm paper is a pulp paper with a starch layer on the surface that absorbs the electrolyte. It is attached to the zinc skin; the top of the diaphragm paper is a carbon cake. The separator paper is like the electric paste layer of a paste dry battery, which serves to isolate the zinc skin negative electrode and the carbon cake positive electrode. The laminated zinc-manganese dry battery eliminates the trouble of series combination of cylindrical paste dry batteries. It has a compact structure, small size and large volume specific capacity. However, the storage life is short and the internal resistance is large, so the discharge current should not be too large.
A battery is a chemical battery that converts electrical energy into chemical energy through charging, stores it, and then converts chemical energy into electrical energy and releases it when used. The transformation process is reversible. When the battery is fully discharged or partially discharged, new compounds are formed on the surfaces of the two electrode plates. At this time, if an appropriate reverse current is passed into the battery, the compounds formed during the discharge process can be reduced to the original active substances to provide Discharge and reuse it next time. This process is called charging, that is, electrical energy is stored in the battery in the form of chemical energy. The process of connecting the battery to the load and supplying current to the external circuit is called discharge. The charging and discharging process of the battery can be repeated many times, so the battery is also called a secondary battery. Depending on the electrolyte solution used, batteries are divided into two categories: acidic and alkaline. According to the active material materials used in the positive and negative plates, there are lead-acid batteries, cadmium-nickel, iron-nickel, silver-zinc, and cadmium-silver batteries. Lead-acid batteries are acid batteries, and the last four are alkaline batteries.
Lead-acid batteries are composed of positive plate group, negative plate group, electrolyte and container. The charged positive plate is brown lead dioxide (PbO2), and the negative plate is gray velvety lead (Pb). When the two plates are placed in sulfuric acid with a concentration of 27% to 37% ( H2SO4) in the aqueous solution, the lead on the plate reacts with sulfuric acid, and the divalent lead ions (Pb2) are transferred to the electrolyte, leaving two electrons (2e-) on the negative plate. Due to the attraction of positive and negative charges, lead ions gather around the negative plate, and the positive plate has a small amount of lead dioxide (PbO2) seeping into the electrolyte under the action of water molecules in the electrolyte. The divalent oxygen ions combine with water to turn the lead dioxide molecule into a dissociable and unstable substance - lead hydroxide [Pb (OH4)]. Lead hydroxide is composed of tetravalent lead cations (Pb4) and It is composed of 4 hydroxyl radicals [4(OH)-]. The 4-valent lead ions (Pb4) remain on the positive plate, making the positive plate positively charged. Since the negative plate is negatively charged, a certain amount of electricity is generated between the two plates. The potential difference is the electromotive force of the battery. When the external circuit is connected, the current flows from the positive electrode to the negative electrode. During the discharge process, the electrons on the negative plate continue to flow to the positive plate through the external circuit. At this time, the sulfuric acid molecules inside the electrolyte Ionize into hydrogen ions (H) and sulfate anions (SO42-). Under the action of the ionic electric field force, the two ions move toward the positive and negative electrodes respectively. After reaching the negative plate, the sulfate anions combine with the lead ions to form lead sulfate ( PbSO2). On the positive plate, due to the inflow of electrons from the external circuit, they combine with the 4-valent lead cations (Pb4) to form divalent lead ions (Pb2), and immediately combine with the sulfate negative ions near the positive plate to form Lead sulfate is attached to the positive electrode. The chemical reaction between the positive and negative plates of the lead acid battery during the discharge process is:
As the battery discharges, both the positive and negative plates are sulfated, and the sulfuric acid in the electrolyte gradually decreases. , and the moisture increases, resulting in a decrease in the specific gravity of the electrolyte. In actual use, the discharge degree of the battery can be determined by measuring the specific gravity of the electrolyte. Under normal use, lead-acid batteries should not be over-discharged, otherwise they will be mixed with active substances. The small lead sulfate crystals formed together form a larger body, which not only increases the resistance of the plate, but also makes it difficult to restore it during charging, which directly affects the capacity and life of the battery. Charging of lead-acid batteries is the reverse process of discharging. . The total chemical reaction during charging is:
Lead-acid batteries have stable operating voltage, wide range of operating temperature and operating current, can charge and discharge for hundreds of cycles, and have good storage performance (especially suitable for dry charging storage)
The use of new lead alloys can improve the performance of lead-acid batteries. >Small float current, reduce the amount of water added and extend its service life; using lead-lithium alloy to cast the positive grid can reduce self-discharge and meet the need for sealing.
Open lead-acid batteries require. Gradually change to sealed type, and develop acid-proof, explosion-proof and hydrogen-eliminating lead-acid batteries.
Compared with lead-acid batteries of the same capacity, alkaline batteries are small in size, have a long life, and can discharge at high currents, but the cost is higher. Alkaline batteries are divided into iron-nickel, cadmium-nickel, zinc-silver battery series according to plate activity
materials. Taking the nickel-cadmium battery as an example, the working principle of the alkaline battery is: after the active material of the battery plate is charged, the positive plate is nickel hydroxide [Ni(OH)3], and the negative plate is Metal cadmium (Cd); when the discharge terminates, the positive plate is converted into nickel hydroxide [Ni(OH2)], the negative plate is converted into cadmium hydroxide [Cd (OH) 2], and potassium hydroxide (KOH) is mostly used as the electrolyte. ) solution. During the charge and discharge process, the total chemical reaction
It can be seen from the chemical reaction during the charge and discharge process that the electrolyte only serves as a carrier of current and the concentration does not change, so it can only be judged based on the change in voltage
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The degree of charge and discharge. During the charging process of the cadmium-nickel sealed battery, oxygen is released from the positive electrode and hydrogen is released from the negative electrode. Since the negative electrode material of the cadmium-nickel sealed battery is manufactured, the occurrence of hydrogen is avoided; and the oxygen generated on the positive electrode is absorbed by the negative electrode due to electrochemical action, thus preventing gas from accumulating inside the battery, thereby ensuring The battery works normally under sealed conditions. Cadmium-nickel batteries have a history of decades. They were originally used as traction, starting, lighting and signal power supplies, and are now used as starting and ignition power supplies for diesel locomotives and aircraft. Sealed batteries made in the 1960s are used as power sources for satellites, portable power tools, and emergency equipment. One of the directions for improving nickel-cadmium batteries is to adopt a bipolar structure. This structure has a small internal resistance and is suitable for pulsed high-current discharge, which can meet the power supply needs of high-power equipment. In addition, the electrodes are pressed or sintered. and foil style.
Metal-air battery is a high-energy battery that uses oxygen in the air as the positive active material and metal as the negative active material. The metals used are generally magnesium, aluminum, zinc, cadmium, iron, etc.; the electrolyte is an aqueous solution. Among them, zinc-air batteries have become mature products.
Metal-air batteries have a higher specific energy because the air is not counted in the weight of the battery. The specific energy of the zinc-air battery is the highest among currently produced batteries, reaching 400 watt·hour/kg (Wh/kg). It is a high-performance medium-power battery and has positive trends. The direction of development of high-power batteries. The metal-air batteries currently produced are mainly primary batteries; the secondary metal-air batteries under development are mechanical rechargeable batteries that use replacement metal electrodes. Because metal-air batteries require a constant supply of air when working, they cannot work in a sealed state or in an environment lacking air. In addition, the electrolyte solution in the battery
is easily affected by air humidity, which degrades battery performance; oxygen in the air will penetrate the air electrode and diffuse to the metal electrode, causing corrosion of the battery and causing self-discharge.
Fuel cells are electrolyte batteries that can undergo chemical reactions as long as they are continuously supplied with chemical raw materials and convert chemical energy into electrical energy. When these chemical raw materials react inside the battery (one raw material is at the positive electrode and the other is at the negative electrode), they must be prevented from reacting directly, otherwise a chemical short circuit will occur and electrical energy cannot be obtained from the reaction. The chemical reactions suitable for fuel cells are mainly combustion reactions, and only hydrogen-oxygen fuel cells have entered the practical stage. Since hydrogen-oxygen fuel cells use the precious metal platinum as electrode material, the cost is too high, so this type of battery is now only used as a power source for spacecraft. The fuel cell has high conversion efficiency, high specific energy, no noise and pollution during operation, and a simple structure.
Other energy conversion batteries mainly include: ① Solar cells. A device that converts sunlight energy into light energy, made of semiconductors. When sunlight hits the cell surface, a potential difference forms on both sides of the semiconductor PN junction. Its efficiency is above 10%. ② Thermoelectric battery. When two metals are connected into a closed loop and different temperatures are maintained at the two joints, a thermoelectric electromotive force will be generated in the loop. This device is called a thermocouple.
When thermocouples are connected in series to form a thermoelectric stack, a thermoelectric battery is formed. Semiconductor materials can also be used to make thermoelectric batteries, which have a strong temperature difference effect. ③Nuclear battery. A device that converts nuclear energy directly into electrical energy is called a nuclear battery. It usually consists of 3 parts: a radioactive source that emits beta rays (high-speed electron flow), a current collector that collects these electrons, and an insulator. One end of the radioactive source becomes a positive electrode due to loss of negative charge, and one end of the collector gains negative charge and becomes a negative electrode. A potential difference is formed between the two electrodes. This kind of nuclear battery has high voltage but low current.
●Today’s various batteries
1. Chemical battery
Chemical battery refers to the chemical energy of the positive and negative active materials through electrochemical reactions. , a type of device that converts into electrical energy. After long-term research and development, chemical batteries have ushered in a wide variety of applications. There are huge devices that can only be accommodated in a building, and devices that are as small as millimeters. Serving our better life all the time. The development of modern electronic technology has placed high demands on chemical batteries. Every breakthrough in chemical battery technology has brought about revolutionary developments in electronic equipment. People in modern society are increasingly inseparable from chemical batteries in their daily lives. Nowadays, many electrochemical scientists in the world are focusing their interests on the field of chemical batteries used as power sources for electric vehicles.
2. Dry batteries and liquid batteries
The distinction between dry batteries and liquid batteries is limited to the period of early battery development. The earliest batteries consisted of a glass container filled with electrolyte and two electrodes. Later, batteries based on paste electrolytes, also known as dry batteries, were introduced.
There are still "liquid" batteries. Generally, they are very large varieties. Such as those large stationary lead-acid batteries used as uninterruptible power supplies or lead-acid batteries used in conjunction with solar cells. For mobile devices, some use fully sealed, maintenance-free lead-acid batteries that have been used successfully for many years, in which the electrolyte sulfuric acid is fixed by silicone gel or absorbed by fiberglass separators.
3. Disposable batteries and rechargeable batteries
Disposable batteries are commonly known as "disposable" batteries, because after their power is exhausted, they cannot be recharged and can only be used. throw away. Common disposable batteries include alkaline manganese batteries, zinc-manganese batteries, lithium batteries, silver-zinc batteries, zinc-air batteries, zinc-mercury batteries and magnesium-manganese batteries.
Rechargeable batteries vary in materials and processes. Common ones include lead-acid batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-metal hydride batteries, and lithium-ion batteries. The advantage is that they have a long cycle life. They can be fully charged and discharged more than 200 times. Some rechargeable batteries have a higher load capacity than most disposable batteries. When ordinary nickel-cadmium and nickel-hydrogen batteries are used, the unique memory effect causes inconvenience in use and often causes premature failure.
4. Fuel cell
A fuel cell is a device that directly converts the chemical energy of fuel into electrical energy through electrochemical reactions
5. Dye sensitivity Chemical solar cells
●What are the battery safety test items?
Internal short circuit test
Continuous charging test
Overcharging
High current charging
Forced discharge
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Drop test
Fall test from a height
Penetration test
Plane crushing test
Cutting test
Low pressure storage test
Thermal abuse test
Water immersion test
Burning test
High pressure test
Baking experiment
Electronic stoves
Generally divided into: No. 1, 2, 3, 5, and 7, among which No. 5 and No. 7 are particularly commonly used. The so-called AA battery is the AA battery, and the AAA battery is the AA battery! AA and AAA both indicate the battery model.
For example:
AA is what we usually call AA battery, the general size is: diameter 14mm, height 49mm;
AAA is what we usually call AAA battery, the general size is: diameter 11mm, height 44mm.
The following is from this site: Ni-MH battery forum netizens’ additions
Attached is some battery knowledge:
Let’s talk about the common “AAAA, AAA, AA, A, SC, C, D, N, F” these models
AAAA models are rare, disposable AAAA Energizer alkaline batteries can occasionally be seen, usually used in computer pens. The standard AAAA (flat head) battery has a height of 41.5±0.5mm and a diameter of 8.1±0.2mm.
AAA type batteries are more common. Generally, MP3 players use AAA batteries. The standard AAA (flat head) battery has a height of 43.6±0.5mm and a diameter of 10.1±0.2mm.
Everyone knows that AA batteries are indispensable for digital cameras and electric toys. The standard AA (flat head) battery has a height of 48.0±0.5mm and a diameter of 14.1±0.2mm.
Battery with only one A indicating the model is not common. This series is usually used as the battery core in the battery pack. I often replace nickel-cadmium and nickel-metal hydride batteries for other people’s old cameras, almost all of which are 4/5A. , or 4/5SC battery cells. The standard A (flat head) battery has a height of 49.0±0.5mm and a diameter of 16.8±0.2mm.
SC models are also not common. They are usually the battery cells in the battery pack. They are mostly seen on power tools, cameras and imported equipment. The standard SC (flat head) battery has a height of 42.0±0.5mm and a diameter of 42.0±0.5mm. 22.1±0.2mm.
C model is the AA battery and has many uses. The standard C (flat head) battery has a height of 49.5±0.5mm and a diameter of 25.3±0.2mm.
D model is AA battery, which is widely used in civil, military and special DC power supplies. The standard D (flat head) battery has a height of 59.0±0.5mm and a diameter of 32.3±0.2mm. .
The N model is not common, and I don’t know what it is used in. The standard N (flat head) battery has a height of 28.5±0.5mm and a diameter of 11.7±0.2mm.
The F-type battery is now a new generation product of electric mopeds and power batteries. It has a tendency to replace lead-acid maintenance-free batteries. They are generally used as battery cells (personal opinion: In fact, they are too big and not suitable for use in batteries). Easy to use alone, haha). The standard N (flat head) battery has a height of 89.0±0.5mm and a diameter of 32.3±0.2mm.
Everyone noticed that the word (flat head) means that the positive electrode of the battery is flat with no protrusions. It uses battery cells used for spot welding of battery packs. Generally, the same model has a pointed head (can be used as a single battery-powered), the height is 0.5mm higher. By analogy, I will not explain them one by one. Also, when there are many batteries, they do not have the regular main models of "AAA, AA, A, SC, C, D, N, F". There are often fractions in front of them "1/3, 2/3, 1/ 2, 2/3, 4/5, 5/4, 7/5", these fractions represent the corresponding height of the pool body. For example, "2/3AA" means a rechargeable battery that is 2/3 as high as an ordinary AA battery. ; Another example is "4/5A" which means a rechargeable battery that is 4/5 of the average A battery.
There is also a way to represent the model, which is a five-digit number, for example, 14500, 17490, 26500. The first two digits refer to the diameter of the pool body, and the last three digits refer to the height of the pool body. For example, 14500 refers to AA battery, i.e. approximately 14mm diameter, 50mm high