Air-zinc batteries. air-zinc element
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
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 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 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 make it possible to create laptops that are practically not inferior in terms of functionality and performance to full-fledged laptops. 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 for a full-fledged work in mobile environment this is clearly not enough (for example, a flight from Moscow to Tokyo takes about 10 hours, and from Moscow to Los 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 standard 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 batteries are one of the subspecies 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 in the process element work, 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 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 the environment - zinc oxide is even used as the main component of 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 elements of large size and power (for example, designed to power power plants Vehicle) 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 as high as those 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. Moreover, unlike lithium batteries air-zinc elements 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. 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.
Treat yourself to the joy of everyday communication
The international company WIDEX has been manufacturing and selling hearing aids since 1956. We are constantly improving devices to provide optimal audibility and comfort for our customers.
WIDEX offers hearing aids in five categories:
- PREMIUM; BUSINESS; COMFORT; BUDGET; ECONOMY.
Our advantages
If you have difficulty hearing, contact the WIDEX Hearing Center - we will help you solve the problem. Our experts will select the devices that best suit your individual needs. With our help, you will regain the ability to hear all the variety of sounds.
Stylish appearance
The range of our hearing centers includes a complete the lineup devices of modern shapes and colors: miniature in-ear, elegant with a receiver in the ear, classic behind the ear. Widex devices and accessories received international design awards - RED DOT Design, Good Design, IF Design Award
Natural sounding devices
Widex machines make sounds recognizable, speech intelligible, noise non-irritating through the operation of a number of patented Widex technologies - Widex amplification formula, speech enhancer, quiet suppression background noise, Inter Ear compression, a wide input range of sounds from 5dB to 113dB, HD locator, TruSound Softner and other technologies.
Quality assurance
We work according to Danish Widex standards. There is a complete set of international and Russian permits, they confirm the reliability and safety of the devices. We regularly monitor quality and user satisfaction.
All inclusive price
The cost of hearing aids includes all necessary consultations and maintenance during the life of the hearing aids. A personal specialist guides the user in the office, by phone or via online consultation Online.
Minimum service periods
Warranty periods repairs in a certified service center Widex Moscow is 2-3 business days. We deliver devices to Moscow and back on a weekly basis at the expense of our company through Widex regional hearing centers. You can monitor the status of service work.
Comfort of use and stable operation of devices
Individual housings for in-the-canal, in-the-ear devices and individual inserts are made using CAMISHA Widex 3D technology. They fit comfortably in the user's ears, as they fully correspond to the casts of the ear canals. Tight fit and optimal size of the products ensure the correct operation of the systems of the devices and an attractive appearance of the device.
In the fifth issue of our magazine, we told how to make a gas accumulator ourselves, and in the sixth issue, a lead-potash accumulator. We offer readers another type of current source - an air-zinc element. This element does not require charging during operation, which is a very important advantage over batteries.
The zinc-air element is now the most advanced current source, since it has a relatively high specific energy (110-180 Wh / kg), is easy to manufacture and operate, and is the most promising in terms of increasing its specific characteristics. The theoretically calculated power density of a zinc-air element can be up to 880 Wh/kg. If even half of this power is achieved, the element will become a very serious rival to the internal combustion engine.
A very important advantage of the air-zinc element is
small change in voltage under load as it is discharged. In addition, such an element has considerable strength, since its vessel can be made of steel.
The principle of operation of air-zinc elements is based on the use of an electrochemical system: zinc - a solution of caustic potassium - activated carbon that adsorbs oxygen from the air. By selecting the compositions of the electrolyte, the active mass of the electrodes and choosing the optimal design of the element, it is possible to significantly increase its specific power.
Zinc air batteries are much more reliable than their predecessors: they don't leak. This means that a suddenly depleted battery will not damage the hearing aid. However, new zinc-air batteries are quite reliable and rarely stop working prematurely. But they also have their own characteristics.
If you do not need to change the batteries in your hearing aid, do not remove the packaging from the battery. Prior to operation, such a battery is sealed with a special film that prevents the penetration of air. Once the film is removed, the cathode (oxygen) and anode (zinc powder) react. This should be remembered: if you remove the film, the battery loses its charge, regardless of whether it was placed in the device or not.
Zinc air batteries are a new generation of batteries that have significant advantages over their predecessors. Undoubtedly, they are much more energy-intensive and durable due to their greater capacity. The cathode of the battery is not silver or mercury oxide, as in other batteries, but oxygen obtained from the air. The interaction of the cathode and the anode occurs evenly throughout the entire life of the battery. The hearing aid will not need to constantly reconfigure and change the volume due to a weakened battery. Zinc powder is used as an anode, which is contained in much more than the anode in the batteries of the previous generation - this ensures its energy intensity.
You can notice the discharge of the battery by such a characteristic “symptom”: a few minutes after turning on the hearing aid, it suddenly stops. This is a signal that it is time to change the batteries.
- The battery is recommended to be used up to the end, and then immediately changed. Do not store used batteries.
- Batteries should be selected according to the size indicated in the description of the hearing aid.
- Keep batteries away from metal products! Metal provokes the closure of contacts, and this will lead to damage to the product.
- It is advisable to carry a spare battery with you, placed in a special protective bag.
- When installing a battery, it is very important to determine where its "plus" side is (it is more convex and has holes for air).
- When inserting a new battery, wait a few minutes after removing protective film: the active substance should be saturated with oxygen as much as possible. This is necessary for the full life of the battery. If you hurry, the anode will be saturated with oxygen only on the surface, and the battery will sit down ahead of time.
- When not in use, the hearing aid should be turned off and the batteries removed.
8. Store batteries in special blisters, at room temperature and out of the reach of children.
Battery technology has improved significantly over the past 10 years, increasing the value of hearing aids and improving their performance. Ever since the digital processor dominated the CA market, the battery industry has exploded.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, thanks to increased capacity They 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 points, 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 as one of the components (cathode) chemical element Power supply uses oxygen from the surrounding air, 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 happen 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.
Third, internal resistance batteries depends on a number of factors: temperature, humidity, operating time and 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 the real mode will be mixed in terms of current consumption. So 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. Wish<сберечь>a longer battery in the refrigerator can lead to the exact opposite result - the CA with a new battery will not 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.
