These elements are characterized by the highest density of all modern technologies. The reason for this was the components used in these batteries. These cells use atmospheric oxygen as the cathode reagent, which is reflected in their name. In order for air to react with the zinc anode, small holes are made in the battery case. Potassium hydroxide, which is highly conductive, is used as the electrolyte in these cells.
Originally designed as a non-rechargeable power source, zinc air cells have a long and stable shelf life, at least when stored airtight and inactive. In this case, during the year of storage, such elements lose about 2 percent of their capacity. Once the air gets into the battery, these batteries don't last longer than a month, whether you use them or not.
Some manufacturers have started using the same technology in rechargeable cells. Best of all, such elements have proven themselves during long-term operation in low-power devices. The main disadvantage of these elements is the high internal resistance, which means that in order to achieve high power, they must be huge. And this means the need to create additional battery compartments in laptops, comparable in size to the computer itself.
But it should be noted that they began to receive such application quite recently. The first such product is a joint creation of Hewlett-Packard Co. and AER Energy Resources Inc. - PowerSlice XL - showed the imperfection of this technology when used in portable computers. This battery, designed for the HP OmniBook 600 laptop, weighed 3.3 kg - more than the computer itself. She provided only 12 hours of work. Energizer has also begun using this technology in their small button batteries used in hearing aids.
Recharging batteries is also not an easy task. Chemical processes are very sensitive to electric current supplied to the battery. If the applied voltage is too low, the battery will give current instead of receiving. If the voltage is too high, unwanted reactions can begin that can damage the element. For example, when the voltage is raised, the current strength will necessarily increase, as a result, the battery will overheat. And if you continue to charge the cell after it is fully charged, explosive gases may begin to be released in it and even an explosion may occur.
Charging technologies
Modern devices for recharging are quite complex electronic devices with various degrees of protection - both yours and your batteries. In most cases, each cell type has its own charger. If the charger is used incorrectly, not only the batteries, but also the device itself, or even systems powered by batteries, can be damaged.
There are two modes of operation chargers- with constant voltage and with direct current.
The simplest are devices with constant voltage. They always produce the same voltage, and supply a current that depends on the battery level (and other environmental factors). As the battery charges, its voltage increases, so the difference between the potentials of the charger and the battery decreases. As a result, less current flows through the circuit.
All that is needed for such a device is a transformer (to reduce the charging voltage to the level required by the battery) and a rectifier (to rectify alternating current to a constant, used to charge the battery). Such simple devices rechargers are used to charge car and ship batteries.
As a rule, lead batteries for power sources are charged by similar devices. uninterruptible power supply. In addition, constant voltage devices are also used to recharge lithium-ion cells. Only there are added circuits to protect the batteries and their owners.
The second type of charger provides a constant current and changes the voltage to provide the required amount of current. Once the voltage reaches the full charge level, charging stops. (Remember, the voltage created by the cell drops as it discharges.) Typically, such devices charge nickel-cadmium and nickel-metal hydride cells.
In addition to the desired voltage level, chargers need to know how long it takes to recharge the cell. The battery can be damaged if you charge it for too long. Depending on the type of battery and on the "intelligence" of the charger, several technologies are used to determine the recharge time.
In the most simple cases for this, the voltage generated by the battery is used. The charger monitors the battery voltage and turns off when the battery voltage reaches a threshold level. But this technology is not suitable for all elements. For example, for nickel-cadmium it is not acceptable. In these elements, the discharge curve is close to a straight line, and it can be very difficult to determine the threshold voltage level.
More "sophisticated" chargers determine the recharge time by temperature. That is, the device monitors the temperature of the cell, and turns off or reduces the charge current when the battery starts to heat up (which means overcharging). Usually, thermometers are built into such batteries, which monitor the temperature of the element and transmit the corresponding signal to the charger.
"Smart" devices use both of these methods. They can go from high charge current to low charge current, or they can support D.C. using special voltage and temperature sensors.
Standard chargers give less charge current than the cell's discharge current. And chargers with a large current value give more current than the rated discharge current of the battery. A trickle charge device uses a current so small that it almost does not allow the battery to self-discharge (by definition, such devices are used to compensate for self-discharge). Typically, the charge current in such devices is one-twentieth or one-thirtieth of the battery's rated discharge current. Modern chargers can often handle multiple charge currents. They use higher currents at first and gradually switch to lower currents as they approach fully charged. If you use a battery that can withstand trickle charging (nickel-cadmium, for example, do not), then at the end of the recharge cycle, the device will switch to this mode. Most laptop chargers and cell phones are designed so that they can be permanently connected to the elements and do not harm them.
The number of people using zinc-air batteries as a power source for hearing aids is increasing day by day. These batteries are environmentally friendly and, due to their increased capacity, last much longer than other types of batteries. However, it is difficult to name the exact service life of the element used, it depends on many factors. AT certain moments users have questions and complaints.<Радуга Звуков>will try to give an exhaustive answer to a very important question: so what does the battery life depend on?
ADVANTAGES...
For many years, mercury-oxide batteries have been the main source of power for hearing aids. However, in the mid 90s. it became clear that they were completely outdated. First, they contained mercury - an extremely harmful substance. Secondly, digital SA appeared and began to rapidly conquer the market, presenting fundamentally different requirements for the characteristics of batteries.
Mercury-oxide technology has been replaced by air-zinc technology. It is unique in that one of the components (cathode) of the chemical battery uses ambient air oxygen, which enters through special holes. By removing mercury or silver oxide, which until now served as the cathode, from the battery case, more space was freed up for zinc powder. Therefore, a zinc-air battery is more energy-intensive when compared with each other. different types batteries of the same size. With this ingenious solution, the zinc-air battery will remain unrivaled as long as its capacity is limited by the tiny volume of today's miniature SAs.
On the positive side of the battery, there are one or more holes (depending on its size) into which air enters. The chemical reaction during which the current is generated proceeds quite quickly and is completely completed within two to three months, even without loading the battery. Therefore, during the manufacturing process, these holes are covered with a protective film.
To prepare for work, it is necessary to remove the sticker and allow time for the active substance to saturate with oxygen (from 3 to 5 minutes). If you start using the battery immediately after opening, then activation will occur only in the surface layer of the substance, which will significantly affect the service life.
The size of the battery plays an important role. The larger it is, the more reserves of the active substance in it, and, therefore, the more accumulated energy. Therefore, a 675 size battery has the largest capacity, and a size 5 battery has the smallest. The battery capacity also depends on the manufacturer. For example, for batteries of size 675, it can vary from 440 mAh to 460 mAh.
AND FEATURES
First, the voltage supplied by a battery depends on how long it has been in use, or more specifically, on the degree to which it has been discharged. A new zinc-air battery can deliver up to 1.4 volts, but only for a short time. Then the voltage drops to 1.25 V, and holds for a long time. And at the end of the battery life, the voltage drops sharply to a value of less than 1 V.
Secondly, zinc-air batteries function better the warmer it is around. In this case, of course, you should not exceed the maximum temperature set for this type of battery. This applies to all batteries. But the peculiarity of zinc-air batteries is that their performance also depends on the humidity of the air. The chemical processes occurring in it depend on the presence of a certain amount of moisture. To put it simply, the hotter and more humid the better (this only applies to CA batteries!). And the fact that humidity has a negative effect on other components of the auditory system is another matter.
Thirdly, the internal resistance of the battery depends on a number of factors: temperature, humidity, operating time and the technology used by the manufacturer. The higher the temperature and humidity, the lower the impedance, which has a beneficial effect on the functioning of the auditory system. The new 675th battery has an internal resistance of 1-2 ohms. However, at the end of the service life, this value can increase to 10 ohms, and for the 13th battery - up to 20 ohms. Depending on the manufacturer, this value can vary significantly, which creates problems when the maximum power specified in the data sheet is required.
If the critical current draw is exceeded, the final stage or the entire hearing system is switched off so that the battery can recover. If after<дыхательной паузы>the battery again begins to give current in an amount sufficient for operation, the SA is turned on again. In many hearing systems, reactivation is accompanied by sound signal, the same one that notifies you of a voltage drop in the battery. That is, in a situation where the CA turns off due to high current consumption, an alarm sounds when it is turned on again, although the battery may be completely new. This situation usually occurs when the hearing aid is receiving a very high input SPL and the hearing aid is set to full power.
Factors affecting service life
One of the main tasks facing batteries is to provide a constant supply of current throughout the life of the battery.
Battery life is primarily determined by the type of CA you use. As a rule, analog devices consume more current than digital ones, and powerful devices consume more than low-power devices. Typical current consumption values for medium power devices are from 0.8 to 1.5 mA, and for high-power and heavy-duty devices - from 2 to 8 mA.
Digital HAs are generally more economical than analog HAs of the same power. However, they have one drawback - at the moment of switching programs or automatic operation of complex signal processing functions (noise suppression, speech recognition, etc.), these devices consume significantly more current than in normal mode. The energy demand can rise and fall depending on what signal processing function it performs. this moment digital circuitry, and even whether correction of a patient's hearing loss requires different amplification for different SPL inputs.
The ambient acoustic situation also affects battery life. In a quiet environment, the acoustic signal level is usually low - about 30-40 dB. In this case, the signal entering the SA is also small. In a noisy environment, such as in the subway, train, at work or in a noisy street, the acoustic signal level can reach 90 dB or more (a jackhammer is about 110 dB). This leads to an increase in the level of the output signal of the SA and, accordingly, an increased current of its consumption. At the same time, the settings of the device also begin to affect - with a greater gain, the current consumption is also greater. Typically, ambient noise is concentrated in the low-frequency range, therefore, with greater suppression of the low-frequency range by the tone control, the current consumption also decreases.
The current consumption of medium-power devices does not depend too much on the level of the incoming signal, but for high-power and super-power SA the difference is quite large. For example, with an incoming signal with an intensity of 60 dB (at which the current consumption of the SA is normalized), the current strength is 2-3 mA. With an input signal of 90 dB (and the same SA settings), the current increases to 15-20 mA.
Battery Life Estimation Method
Typically, the battery life is estimated taking into account its nominal capacity and the estimated current consumption of the device, specified in the technical data (passport) for the device. Let's take a typical case: a 675 zinc-air battery with a typical capacity of 460 mAh.
When used in a medium power device with a current consumption of 1.4mA, the theoretical service life will be 460/1.4=328 hours. When wearing the device for 10 hours a day, this means more than a month of device operation (328/10=32.8).
When a powerful device is powered in a quiet environment (current consumption 2 mA), the service life will be 230 hours, that is, about three weeks with a 10-hour wear. But, if the environment is noisy, then the current consumption can reach 15-20 mA (depending on the type of device). In this mode, the service life will be 460/20=23 hours, i.e. less than 3 days. Of course, no one walks in such an environment for 10 hours, and real mode will be mixed in current consumption. So that given example simply illustrates the calculation methodology by giving extreme life values. Usually the battery life in a powerful device is in the range of two to three weeks.
Use hearing aid batteries (labeled or labeled) from reputable power supply manufacturers (GP, Renata, Energizer, Varta, Panasonic, Duracell Activair, Rayovac).
Do not break the protective film of the battery (do not open) until it is installed in the hearing aid.
Store batteries in blisters at room temperature and normal humidity. A wish<сберечь>a longer battery in the refrigerator can lead to the exact opposite result - CA with new battery won't work at all.
Before installing the battery in the device, keep it without film for 3-5 minutes.
Turn off the SA when not in use. Remove the power sources from the device at night and leave the battery compartment open.
The entry of compact zinc-air batteries into the mass market can significantly change the situation in the market segment of small-sized autonomous power supplies for laptop computers and digital devices.
energy problem
a last years the fleet of portable computers and various digital devices has increased significantly, many of which have appeared on the market quite recently. This process has accelerated markedly due to the increasing popularity of mobile phones. In turn, the rapid growth in the number of portable electronic devices caused a serious increase in demand for autonomous sources of electricity, in particular for different kinds batteries and accumulators.
However, the need to ensure huge amount portable devices batteries is only one side of the problem. Thus, as portable electronic devices develop, the density of mounting elements and the power of microprocessors used in them increase in just three years, the clock frequency of PDA processors used has increased by an order of magnitude. Tiny monochrome screens are being replaced by color displays with high resolution and larger screen size. All this leads to an increase in energy consumption. In addition, in the field of portable electronics, there is a clear trend towards further miniaturization. Taking into account the above factors, it becomes quite obvious that an increase in energy intensity, power, durability and reliability of used batteries is one of the most important conditions for ensuring the further development of portable electronic devices.
The problem of renewable autonomous power sources is very acute in the segment of portable PCs. Modern technologies allow you to create laptops that are practically not inferior in terms of functionality and performance to full-fledged desktop systems. However, the lack of sufficiently efficient autonomous power sources deprives laptop users of one of the main advantages of this type of computer - mobility. A good indicator for a modern laptop equipped with a lithium-ion battery is a battery life of about 4 hours 1 , but this is clearly not enough for full-fledged work in mobile conditions (for example, a flight from Moscow to Tokyo takes about 10 hours, and from Moscow to Los Angeles). Angeles almost 15).
One of the solutions to the problem of increasing the time battery life portable PCs is the transition from the now common nickel-metal hydride and lithium-ion batteries to chemical fuel cells 2 . The most promising from the point of view of application in portable electronic devices and PCs are low operating temperature fuel cells such as PEM (Proton Exchange Membrane) and DMCF (Direct Methanol Fuel Cells). An aqueous solution of methyl alcohol (methanol) 3 is used as fuel for these elements.
However, at this stage, it would be too optimistic to describe the future of chemical fuel cells exclusively in pink colors. The fact is that at least two obstacles stand in the way of the mass distribution of fuel cells in portable electronic devices. Firstly, methanol is a rather toxic substance, which implies increased requirements for tightness and reliability of fuel cartridges. Secondly, to ensure an acceptable rate of chemical reactions in fuel cells with a low operating temperature, it is necessary to use catalysts. PEM and DMCF cells currently use catalysts made from platinum and its alloys, but the natural resources of this substance are small and its cost is high. It is theoretically possible to replace platinum with other catalysts, but so far none of the teams involved in research in this direction has been able to find an acceptable alternative. Today, the so-called platinum problem is perhaps the most serious obstacle to the widespread use of fuel cells in portable PCs and electronic devices.
1 This refers to the operating time from a regular battery.
2 More information about fuel cells can be found in the article “Fuel cells: a year of hope”, published in No. 1’2005.
3 Hydrogen gas PEM cells are equipped with a built-in converter to produce hydrogen from methanol.
Air-zinc elements
Although the authors of a number of publications consider zinc-air batteries and accumulators to be one of the subtypes of fuel cells, this is not entirely true. Familiarize yourself with the device and the principle of operation air-zinc elements even in general terms, one can make a quite unambiguous conclusion that it is more correct to consider them as a separate class autonomous sources nutrition.
The zinc air cell design includes a cathode and an anode separated by an alkaline electrolyte and mechanical separators. A gas diffusion electrode (GDE) is used as a cathode, the permeable membrane of which makes it possible to obtain oxygen from atmospheric air circulating through it. The “fuel” is the zinc anode, which is oxidized during the operation of the element, and the oxidizing agent is oxygen obtained from atmospheric air entering through the “breathing holes”.
At the cathode, an oxygen electroreduction reaction occurs, the products of which are negatively charged hydroxide ions:
O 2 + 2H 2 O + 4e 4OH -.
Hydroxide ions move in the electrolyte to the zinc anode, where the zinc oxidation reaction occurs with the release of electrons, which return to the cathode through an external circuit:
Zn + 4OH – Zn(OH) 4 2– + 2e.
Zn(OH) 4 2– ZnO + 2OH – + H 2 O.
It is clear that the air zinc elements do not fall under the classification of chemical fuel cells: firstly, they use a consumable electrode (anode), and secondly, the fuel is initially placed inside the cell, and is not supplied from the outside during operation.
The voltage between the electrodes of one cell of the zinc air cell is 1.45 V, which is very close to that of alkaline (alkaline) batteries. If necessary, to get more high voltage power supply, you can combine several series-connected cells into a battery.
Zinc is a fairly common and inexpensive material, so when mass production of zinc-air elements is deployed, manufacturers will not experience problems with raw materials. In addition, even at the initial stage, the cost of such power supplies will be quite competitive.
It is also important that air-zinc elements are very environmentally friendly products. The materials used for their production do not poison the environment and can be reused after processing. The reaction products of air-zinc elements (water and zinc oxide) are also absolutely safe for humans and environment Zinc oxide is even used as the main ingredient in baby powder.
Of the operational properties of air-zinc elements, it is worth noting such advantages as low speed self-discharge in the non-activated state and a small change in the magnitude of the voltage as the discharge progresses (flat discharge curve).
A certain disadvantage of air-zinc elements is the influence of the relative humidity of the incoming air on the characteristics of the element. For example, for a zinc-air element designed for operation in conditions of 60% relative air humidity, with an increase in humidity to 90%, the service life decreases by about 15%.
From batteries to accumulators
Disposable batteries are the easiest zinc-air cell to implement. When creating zinc-air cells of large size and power (for example, designed to power the power plants of vehicles), the zinc anode cassettes can be made replaceable. In this case, to renew the energy reserve, it is enough to remove the cassette with used electrodes and install a new one instead. Spent electrodes can be recovered for reuse by the electrochemical method at specialized enterprises.
If we talk about compact batteries suitable for use in portable PCs and electronic devices, then the practical implementation of the option with replaceable zinc anode cassettes is impossible due to the small size of the batteries. That is why most of the compact zinc air cells currently on the market are disposable. Single-use zinc-air batteries of small size are produced by Duracell, Eveready, Varta, Matsushita, GP, as well as the domestic enterprise Energia. The main scope of such power supplies hearing aids, portable radio stations, photographic equipment, etc.
Many companies are now producing disposable zinc air batteries.
Several years ago, AER produced Power Slice zinc-air flat batteries for portable computers. These items were designed for Hewlett-Packard's Omnibook 600 and Omnibook 800 series notebooks; their battery life ranged from 8 to 12 hours.
In principle, there is also the possibility of creating rechargeable zinc-air cells (accumulators), in which, when an external current source is connected, a zinc reduction reaction will occur at the anode. However, the practical implementation of such projects for a long time hampered by serious problems due to the chemical properties of zinc. Zinc oxide dissolves well in an alkaline electrolyte and, in dissolved form, is distributed throughout the volume of the electrolyte, moving away from the anode. Because of this, when charging from an external current source, the geometry of the anode changes to a large extent: the zinc reduced from oxide is deposited on the anode surface in the form of ribbon crystals (dendrites), similar in shape to long spikes. The dendrites pierce through the separators, causing a short circuit inside the battery.
This problem aggravated by the fact that to increase the power, the anodes of air-zinc cells are made from crushed zinc powder (this allows you to significantly increase the surface area of the electrode). Thus, as the number of charge-discharge cycles increases, the surface area of the anode will gradually decrease, having a negative impact on cell performance.
To date, Zinc Matrix Power (ZMP) has achieved the greatest success in the field of compact zinc-air batteries. ZMP experts have developed a unique technology Zinc Matrix, which allowed to solve the main problems that arise in the process of charging batteries. The essence of this technology is the use of a polymeric binder, which provides unhindered penetration of hydroxide ions, but at the same time blocks the movement of zinc oxide that dissolves in the electrolyte. Thanks to the use of this solution, it is possible to avoid a noticeable change in the shape and surface area of the anode for at least 100 charge-discharge cycles.
The advantages of zinc-air batteries are a long operating time and a high specific energy intensity, at least twice that of the best lithium-ion batteries. The specific energy intensity of zinc-air batteries reaches 240 Wh per 1 kg of weight, and the maximum power is 5000 W/kg.
According to ZMP developers, today it is possible to create zinc-air batteries for portable electronic devices (mobile phones, digital players etc.) with an energy consumption of about 20 Wh. The minimum possible thickness of such power supplies is only 3 mm. Experimental prototypes of zinc-air batteries for laptops have an energy capacity of 100 to 200 Wh.
Zinc air battery prototype developed by Zinc Matrix Power
Another important advantage of zinc-air batteries complete absence the so-called memory effect. Unlike other types of batteries, zinc-air cells can be recharged at any charge level without compromising their energy capacity. Moreover, unlike lithium batteries air-zinc elements are much safer.
In conclusion, one cannot fail to mention one important event, which has become a symbolic Starting point on the way to the commercialization of zinc air cells: On June 9 last year, Zinc Matrix Power officially announced the signing of a strategic agreement with Intel Corporation. In accordance with the clauses of this agreement, ZMP and Intel will join forces in the development of new technology rechargeable batteries for laptops. Among the main goals of these works increase the battery life of laptops up to 10 hours. According to the existing plan, the first models of notebooks equipped with zinc-air batteries should appear on sale in 2006.
The entry of compact zinc-air batteries into the mass market can significantly change the situation in the market segment of small-sized autonomous power supplies for portable computers and digital devices.
energy problem
and in recent years, the fleet of portable computers and various digital devices has increased significantly, many of which have appeared on the market quite recently. This process has accelerated markedly due to the increasing popularity of mobile phones. In turn, the rapid growth in the number of portable electronic devices has caused a serious increase in demand for autonomous sources of electricity, in particular for various types of batteries and accumulators.
However, the need to provide a huge number of portable devices with batteries is only one side of the problem. Thus, as portable electronic devices develop, the density of mounting elements and the power of microprocessors used in them increase in just three years, the clock frequency of PDA processors used has increased by an order of magnitude. Tiny monochrome screens are being replaced by high-resolution color displays with larger screen sizes. All this leads to an increase in energy consumption. In addition, in the field of portable electronics, there is a clear trend towards further miniaturization. Taking into account the above factors, it becomes quite obvious that an increase in energy intensity, power, durability and reliability of used batteries is one of the most important conditions for ensuring the further development of portable electronic devices.
The problem of renewable autonomous power sources is very acute in the segment of portable PCs. Modern technologies make it possible to create laptops that are practically not inferior in terms of functionality and performance to full-fledged desktop systems. However, the lack of sufficiently efficient autonomous power sources deprives laptop users of one of the main advantages of this type of computer - mobility. A good indicator for a modern laptop equipped with a lithium-ion battery is a battery life of about 4 hours 1 , but this is clearly not enough for full-fledged work in mobile conditions (for example, a flight from Moscow to Tokyo takes about 10 hours, and from Moscow to Los Angeles). Angeles almost 15).
One solution to the problem of longer battery life for portable PCs is to move from the now common nickel-metal hydride and lithium-ion batteries to chemical fuel cells 2 . The most promising from the point of view of application in portable electronic devices and PCs are low operating temperature fuel cells such as PEM (Proton Exchange Membrane) and DMCF (Direct Methanol Fuel Cells). An aqueous solution of methyl alcohol (methanol) 3 is used as fuel for these elements.
However, at this stage, it would be too optimistic to describe the future of chemical fuel cells exclusively in pink colors. The fact is that at least two obstacles stand in the way of the mass distribution of fuel cells in portable electronic devices. Firstly, methanol is a rather toxic substance, which implies increased requirements for tightness and reliability of fuel cartridges. Secondly, to ensure an acceptable rate of chemical reactions in fuel cells with a low operating temperature, it is necessary to use catalysts. PEM and DMCF cells currently use catalysts made from platinum and its alloys, but the natural resources of this substance are small and its cost is high. It is theoretically possible to replace platinum with other catalysts, but so far none of the teams involved in research in this direction has been able to find an acceptable alternative. Today, the so-called platinum problem is perhaps the most serious obstacle to the widespread use of fuel cells in portable PCs and electronic devices.
1 This refers to the operating time from a regular battery.
2 More information about fuel cells can be found in the article “Fuel cells: a year of hope”, published in No. 1’2005.
3 Hydrogen gas PEM cells are equipped with a built-in converter to produce hydrogen from methanol.
Air-zinc elements
Although the authors of a number of publications consider zinc-air batteries and accumulators to be one of the subtypes of fuel cells, this is not entirely true. Having become acquainted with the device and the principle of operation of zinc-air cells, even in general terms, we can make a completely unambiguous conclusion that it is more correct to consider them as a separate class of autonomous power sources.
The zinc air cell design includes a cathode and an anode separated by an alkaline electrolyte and mechanical separators. A gas diffusion electrode (GDE) is used as a cathode, the permeable membrane of which makes it possible to obtain oxygen from atmospheric air circulating through it. The “fuel” is the zinc anode, which is oxidized during the operation of the element, and the oxidizing agent is oxygen obtained from atmospheric air entering through the “breathing holes”.
At the cathode, an oxygen electroreduction reaction occurs, the products of which are negatively charged hydroxide ions:
O 2 + 2H 2 O + 4e 4OH -.
Hydroxide ions move in the electrolyte to the zinc anode, where the zinc oxidation reaction occurs with the release of electrons, which return to the cathode through an external circuit:
Zn + 4OH – Zn(OH) 4 2– + 2e.
Zn(OH) 4 2– ZnO + 2OH – + H 2 O.
It is quite obvious that zinc-air cells do not fall under the classification of chemical fuel cells: firstly, they use a consumable electrode (anode), and secondly, the fuel is initially placed inside the cell, and is not supplied from the outside during operation.
The voltage between the electrodes of one cell of the zinc air cell is 1.45 V, which is very close to that of alkaline (alkaline) batteries. If necessary, to obtain a higher supply voltage, several series-connected cells can be combined into a battery.
Zinc is a fairly common and inexpensive material, so when mass production of zinc-air elements is deployed, manufacturers will not experience problems with raw materials. In addition, even at the initial stage, the cost of such power supplies will be quite competitive.
It is also important that air-zinc elements are very environmentally friendly products. The materials used for their production do not poison the environment and can be reused after processing. The reaction products of air-zinc elements (water and zinc oxide) are also absolutely safe for humans and the environment - zinc oxide is even used as the main component of baby powder.
Of the operational properties of zinc-air cells, it is worth noting such advantages as a low self-discharge rate in the non-activated state and a small change in the voltage value during the discharge (flat discharge curve).
A certain disadvantage of air-zinc elements is the influence of the relative humidity of the incoming air on the characteristics of the element. For example, for a zinc-air element designed for operation in conditions of 60% relative air humidity, with an increase in humidity to 90%, the service life decreases by about 15%.
From batteries to accumulators
Disposable batteries are the easiest zinc-air cell to implement. When creating zinc-air cells of large size and power (for example, designed to power the power plants of vehicles), the zinc anode cassettes can be made replaceable. In this case, to renew the energy reserve, it is enough to remove the cassette with used electrodes and install a new one instead. Spent electrodes can be recovered for reuse by the electrochemical method at specialized enterprises.
If we talk about compact batteries suitable for use in portable PCs and electronic devices, then the practical implementation of the option with replaceable zinc anode cassettes is impossible due to the small size of the batteries. That is why most of the compact zinc air cells currently on the market are disposable. Single-use zinc-air batteries of small size are produced by Duracell, Eveready, Varta, Matsushita, GP, as well as the domestic enterprise Energia. The main scope of such power supplies hearing aids, portable radio stations, photographic equipment, etc.
Many companies are now producing disposable zinc air batteries.
Several years ago, AER produced Power Slice zinc-air flat batteries for portable computers. These items were designed for Hewlett-Packard's Omnibook 600 and Omnibook 800 series notebooks; their battery life ranged from 8 to 12 hours.
In principle, there is also the possibility of creating rechargeable zinc-air cells (accumulators), in which, when an external current source is connected, a zinc reduction reaction will occur at the anode. However, the practical implementation of such projects has long been hampered by serious problems caused by the chemical properties of zinc. Zinc oxide dissolves well in an alkaline electrolyte and, in dissolved form, is distributed throughout the volume of the electrolyte, moving away from the anode. Because of this, when charging from an external current source, the geometry of the anode changes to a large extent: the zinc reduced from oxide is deposited on the anode surface in the form of ribbon crystals (dendrites), similar in shape to long spikes. The dendrites pierce through the separators, causing a short circuit inside the battery.
This problem is exacerbated by the fact that to increase the power, the anodes of air-zinc cells are made from crushed zinc powder (this allows a significant increase in the surface area of the electrode). Thus, as the number of charge-discharge cycles increases, the surface area of the anode will gradually decrease, having a negative impact on cell performance.
To date, Zinc Matrix Power (ZMP) has achieved the greatest success in the field of compact zinc-air batteries. ZMP experts have developed a unique technology Zinc Matrix, which allowed to solve the main problems that arise in the process of charging batteries. The essence of this technology is the use of a polymeric binder, which provides unhindered penetration of hydroxide ions, but at the same time blocks the movement of zinc oxide that dissolves in the electrolyte. Thanks to the use of this solution, it is possible to avoid a noticeable change in the shape and surface area of the anode for at least 100 charge-discharge cycles.
The advantages of zinc-air batteries are a long operating time and a high specific energy intensity, at least twice that of the best lithium-ion batteries. The specific energy intensity of zinc-air batteries reaches 240 Wh per 1 kg of weight, and the maximum power is 5000 W/kg.
According to ZMP developers, today it is possible to create zinc-air batteries for portable electronic devices (mobile phones, digital players, etc.) with an energy capacity of about 20 Wh. The minimum possible thickness of such power supplies is only 3 mm. Experimental prototypes of zinc-air batteries for laptops have an energy capacity of 100 to 200 Wh.
Zinc air battery prototype developed by Zinc Matrix Power
Another important advantage of zinc-air batteries is the complete absence of the so-called memory effect. Unlike other types of batteries, zinc-air cells can be recharged at any charge level without compromising their energy capacity. In addition, unlike lithium batteries, zinc air cells are much safer.
In conclusion, it is impossible not to mention one important event, which became a symbolic starting point for the commercialization of zinc air cells: on June 9 last year, Zinc Matrix Power officially announced the signing of a strategic agreement with Intel Corporation. Under the terms of this agreement, ZMP and Intel will join forces to develop new laptop battery technology. Among the main goals of these works increase the battery life of laptops up to 10 hours. According to the existing plan, the first models of notebooks equipped with zinc-air batteries should appear on sale in 2006.
Manganese zinc element. (1) metal cap, (2) graphite electrode ("+"), (3) zinc cup (" "), (4) manganese oxide, (5) electrolyte, (6) metal contact. Manganese zinc element, ... ... Wikipedia
RC 53M (1989) Mercury-zinc cell ("RC type") is a galvanic cell in which zinc is the anode ... Wikipedia
Oxyride Battery Oxyride™ batteries are the brand name for disposable (non-rechargeable) batteries designed by Panasonic. They are designed specifically for devices with high power consumption ... Wikipedia
The normal Weston cell, the mercury-cadmium cell is a galvanic cell whose EMF is very stable over time and reproducible from instance to instance. It is used as a reference voltage source (ION) or a voltage standard ... ... Wikipedia
STs 25 Silver-zinc battery is a secondary chemical current source, a battery in which the anode is silver oxide, in the form of a compressed powder, the cathode is a mixture ... Wikipedia
Miniature batteries of various sizes wrist watch, therefore also called ... Wikipedia
Mercury-zinc cell (“RC type”) is 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. Disadvantages: ... ... Wikipedia
A manganese-zinc electrochemical cell that uses manganese dioxide as the cathode, powdered zinc as the anode, and an alkali solution, usually potassium hydroxide, as the electrolyte. Contents 1 History of invention ... Wikipedia
Nickel-zinc battery is a chemical current source in which zinc is an anode, potassium hydroxide with lithium hydroxide as an electrolyte, and nickel oxide as a cathode. Often abbreviated as NiZn. Advantages: ... ... Wikipedia