Battery world - part 3
Content
The history of modern batteries begins in the nineteenth century, from this century most of the designs in use today originate. This situation testifies, on the one hand, to the excellent ideas of scientists of that time, and, on the other hand, to the difficulties that arise in the development of new models.
Few things are so good that they can't be improved upon. This rule also applies to batteries - XNUMXth century models were refined many times until they took on their current form. This also applies to Leclanche cells.
Link to improve
The design of the French chemist has been changed Carl Gasner into a really useful model: cheap to manufacture and safe to use. However, there were still problems - the zinc coating of the element corroded upon contact with the acidic electrolyte that filled the bowl, and splashing out aggressive contents could disable the powered device. The decision became amalgamation the inner surface of the zinc body (mercury coating).
Zinc amalgam practically does not react with acids, but retains all the electrochemical properties of pure metal. However, due to environmental regulations, this method of extending the life of the cells is used less and less (on mercury-free cells, you can find the inscription or) (1).
2. Alkaline cell layout: 1) case (cathode lead), 2) cathode containing manganese dioxide, 3) electrode separator, 4) anode containing KOH and zinc dust, 5) anode terminal, 6) cell sealing (electrode insulator) . .
Another way to increase cell longevity and life is to add zinc chloride ZnCl2 for cup filling paste. Cells of this design are often referred to as Heavy Duty and (as the name suggests) are designed to power more energy intensive devices.
A breakthrough in the field of disposable batteries was the construction in 1955 of alkaline cell. Canadian engineer's invention Lewis Urry, used by the current Energizer company, has a structure slightly different from that of the Leclanchet cell.
First, you won't find a graphite cathode or a zinc cup there. Both electrodes are made in the form of wet, separated pastes (thickeners plus reagents: the cathode consists of a mixture of manganese dioxide and graphite, the anode of zinc dust with an admixture of potassium hydroxide), and their terminals are made of metal (2). However, the reactions that occur during operation are very similar to those that occur in the Leclanchet cell.
Task. Perform a "chemical autopsy" on an alkaline cell to find out that the contents are indeed alkaline (3). Remember that the same precautions apply to the dismantling of the Leclanchet cell. See the Battery Code field for how to identify an alkaline cell.
3. "Section" of the alkaline cell confirms the alkali content.
Homemade batteries
4. Domestic Ni-MH and Ni-Cd batteries.
Cells that can be recharged after use have been the goal of designers from the very beginning of the development of the science of electricity, hence the many types of them.
Currently, one of the models used to power small household appliances are nickel-cadmium batteries. Their prototype appeared in 1899 when a Swedish inventor did it. Ernst Jungner applied for a patent for a nickel-cadmium battery that could compete with batteries already widely used in the automotive industry. lead acid battery.
The cell anode is cadmium, the cathode is a trivalent nickel compound, the electrolyte is a potassium hydroxide solution (in modern “dry” designs, a wet paste of thickeners saturated with a KOH solution). Ni-Cd batteries (this is their designation) have an operating voltage of approximately 1,2 V - this is less than that of disposable cells, which, however, is not a problem for most applications. The big advantage is the ability to consume significant current (even a few amperes) and a wide range of operating temperatures.
5. Check the requirements for different types of batteries before charging.
The disadvantage of nickel-cadmium batteries is a burdensome "memory effect". This occurs when frequently recharging partially discharged Ni-Cd batteries: the system behaves as if its capacity is only equal to the charge replenished by recharging. In some types of chargers, the "memory effect" can be reduced by charging the cells in a special mode.
Therefore, discharged nickel-cadmium batteries should be charged in a full cycle: first completely discharged (using the appropriate charger function) and then recharged. Frequent recharging also reduces the estimated life of 1000-1500 cycles (that many disposable cells will be replaced by a single battery during its lifespan, so the higher purchase cost will pay for itself many times over, not to mention much less strain on the battery). environment with the production and disposal of cells).
Ni-Cd elements containing toxic cadmium have been replaced nickel-metal hydride batteries (Ni-MH designation). Their structure is similar to Ni-Cd batteries, but instead of cadmium, a porous metal alloy (Ti, V, Cr, Fe, Ni, Zr, rare earth metals) with the ability to absorb hydrogen is used (4). The operating voltage of the Ni-MH cell is also about 1,2 V, which allows them to be used interchangeably with NiCd batteries. The capacity of Nickel Metal Hydride cells is greater than that of Nickel Cadmium cells of the same size. However, NiMH systems self-discharge faster. There are already modern designs that do not have this drawback, but they cost much more than standard models.
Nickel-metal hydride batteries do not exhibit a "memory effect" (partially discharged cells can be recharged). However, it is always necessary to check the charging requirements of each type in the instructions for the charger (5).
In the case of Ni-Cd and Ni-MH batteries, we do not recommend disassembling them. First, we will not find anything useful in them. Secondly, nickel and cadmium are not safe elements. Do not take risks unnecessarily and leave the disposal to trained professionals.
The king of accumulators, that is...
6. "King of batteries" at work.
… Lead-acid battery, built in 1859 by a French physicist Gaston Plantego (yes, yes, the device will turn 161 years old this year!). The battery electrolyte is about 37% sulfuric acid (VI) solution, and the electrodes are lead (anode) and lead coated with a layer of lead dioxide PbO.2 (cathode). During operation, a precipitate of lead(II)(II)PbSO sulfate forms on the electrodes4. When charging, one cell has a voltage of more than 2 volts.
lead battery it actually has all the disadvantages: significant weight, sensitivity to discharge and low temperatures, the need to store in a charged state, the risk of aggressive electrolyte leakage and the use of toxic metal. In addition, it requires careful handling: checking the density of the electrolyte, adding water to the chambers (use only distilled or deionized), voltage control (dropping below 1,8 V in one chamber may damage the electrodes) and a special charging mode.
So why is the ancient structure still in use? The “King of Accumulators” has what is an attribute of a real ruler - power. High current consumption and high energy efficiency up to 75% (this amount of energy used for charging can be recovered during operation), as well as simple design and low cost of production, mean that lead battery It is used not only to start internal combustion engines, but also as an element of emergency power supply. Despite 160 years of history, the lead battery is still doing well and has not been supplanted by other types of these devices (and with it, lead itself, which, thanks to the battery, is one of the metals produced in the largest quantities). As long as motorization based on internal combustion engines continues to develop, its position will probably not be threatened (6).
Inventors did not stop trying to create a replacement for the lead-acid battery. Some of the models became popular and are still used in the automotive industry today. At the turn of the nineteenth and twentieth centuries, designs were created in which H solution was not used.2SO4but alkaline electrolytes. An example is Ernst Jungner's nickel-cadmium battery shown above. In 1901 Thomas Alva Edison changed the design to use iron instead of cadmium. Compared to acid batteries, alkaline batteries are much lighter, can operate at low temperatures and are not as difficult to handle. However, their production is more expensive, and energy efficiency is lower.
So, what is next?
Of course, the articles on batteries do not exhaust the questions. They do not discuss, for example, lithium cells, also commonly used to power household appliances such as calculators or computer motherboards. You can learn more about them in the January article about last year's Nobel Prize in Chemistry, and on the practical part - in a month (including demolition and experience).
There are good prospects for cells, especially batteries. The world is becoming more and more mobile, which means the need to become independent of power cables. Ensuring efficient energy supply for electric vehicles is also a big problem. - so that they can compete with cars with an internal combustion engine also in terms of economy.
accumulator battery
To facilitate cell type identification, a special alphanumeric code has been introduced. For the types most commonly found in our homes for small appliances, it has the form number-letter-letter-number.
And yes:
- the first digit is the number of cells; ignored for single cells;
– the first letter indicates the cell type. When it is missing, you are dealing with the Leclanche link. Other cell types are labeled as follows:
C – lithium cell (the most common type),
H – Ni-MH battery,
K – nickel-cadmium battery,
L – alkaline cell;
- the following letter indicates the shape of the link:
F - plate,
R - cylindrical,
P - the general designation of links having a shape other than cylindrical;
– the final figure or figures indicate the size of the link (catalogue values or directly indicating dimensions) (7).
7. Dimensions of popular cells and batteries.
Examples of marking:
R03
- a zinc-graphite cell the size of a little finger. Another designation is AAA or.
LR6 - an alkaline cell the size of a finger. Another designation is AA or.
HR14 – Ni-MH battery; the letter C is also used to indicate size.
KR20 – Ni-Cd battery, the size of which is also marked with the letter D.
3LR12 – a flat battery with a voltage of 4,5 V, consisting of three cylindrical alkaline cells.
6F22 - 9-volt battery, consisting of six Leclanchet flat cells.
CR2032 – lithium cell with a diameter of 20 mm and a thickness of 3,2 mm.
See also:
