Zinc air battery. Zinc air batteries. Use in hearing aids. Benefits of hearing aid batteries
The release 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 laptop computers and various digital devices has increased significantly, many of which have only recently appeared on the market. This process has accelerated noticeably due to the increase in popularity 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 provide a huge amount portable devices nutritional elements is only one side of the problem. Thus, as portable electronic devices develop, the density of the elements and the power of the microprocessors used in them increase; in just three years, the clock frequency of the PDA processors used has increased by an order of magnitude. Tiny monochrome screens are being replaced by color displays with high resolution and increased screen size. All this leads to an increase in energy consumption. In addition, there is a clear trend towards further miniaturization in the field of portable electronics. Taking into account these factors, it becomes quite obvious that increasing the energy intensity, power, durability and reliability of the batteries used 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 their functionality and performance to full-fledged ones 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 full-fledged work V mobile conditions 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 options for solving the problem of increasing time battery life portable PCs is a shift from the currently common nickel-metal hydride and lithium-ion batteries to chemical fuel cells 2 . The most promising fuel cells from the point of view of application in portable electronic devices and PCs are fuel cells with low operating temperatures such as PEM (Proton Exchange Membrane) and DMCF (Direct Methanol Fuel Cells). The fuel used for these elements is water solution methyl alcohol (methanol) 3.
However, at this stage, it would be too optimistic to describe the future of chemical fuel cells solely in rosy tones. The fact is that there are at least two obstacles to the mass distribution of fuel cells in portable electronic devices. Firstly, methanol is a rather toxic substance, which implies increased requirements for the tightness and reliability of fuel cartridges. Secondly, to ensure acceptable rates of chemical reactions in fuel cells with low operating temperatures, it is necessary to use catalysts. Currently, catalysts made of platinum and its alloys are used in PEM and DMCF cells, but natural reserves 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 engaged in research in this direction have been able to find an acceptable alternative. Today, the so-called platinum problem is perhaps the most serious obstacle to the widespread adoption 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 read in the article “Fuel cells: a year of hope”, published in No. 1’2005.
3 PEM cells operating on hydrogen gas are equipped with a built-in converter to produce hydrogen from methanol.
Zinc air 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 familiar with the design and principle of operation of zinc-air elements, 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 cell design includes a cathode and anode separated by an alkaline electrolyte and mechanical separators. A gas diffusion electrode (GDE) is used as a cathode, the water-permeable membrane of which allows oxygen to be obtained from atmospheric air circulating through it. The “fuel” is the zinc anode, which is oxidized in the process element operation, and the oxidizing agent is oxygen obtained from atmospheric air entering through the “breathing holes”.
At the cathode, the electroreduction reaction of oxygen 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, releasing electrons that 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 during operation from the outside.
The voltage between the electrodes of one cell of a 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 deploying mass production of zinc-air cells, 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 zinc air elements are very environmentally friendly products. The materials used for their production do not poison the environment and can be reused after recycling. The reaction products of zinc air 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.
Among the operational properties of zinc air elements, it is worth noting such advantages as low speed self-discharge in the non-activated state and a small change in the voltage value as the discharge progresses (flat discharge curve).
A certain disadvantage of zinc air elements is the influence of the relative humidity of the incoming air on the characteristics of the element. For example, for a zinc air cell designed for operation in conditions of relative air humidity of 60%, when the humidity increases to 90%, the service life decreases by approximately 15%.
From batteries to batteries
The easiest option for zinc-air cells to implement is disposable batteries. When creating zinc air elements big size and power (for example, intended 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 the used electrodes and install a new one in its place. Used electrodes can be restored for reuse using 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. This is why most compact zinc air cells currently on the market are disposable. Disposable small-sized zinc-air batteries are produced by Duracell, Eveready, Varta, Matsushita, GP, as well as the domestic enterprise Energia. The main areas of application for such power sources are hearing aids, portable radios, photographic equipment, etc.
Currently, many companies produce disposable zinc air batteries
A few years ago, AER produced Power Slice zinc air batteries designed for laptop computers. These items were designed for Hewlett-Packard's Omnibook 600 and Omnibook 800 series laptops; their battery life ranged from 8 to 12 hours.
In principle, there is also the possibility of creating rechargeable zinc-air cells (batteries), in which, when connected, external source current at the anode, a zinc reduction reaction will occur. 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 entire 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 significantly: the zinc recovered from zinc oxide is deposited on the surface of the anode in the form of ribbon crystals (dendrites), shaped like long spikes. The dendrites pierce through the separators, causing a short circuit inside the battery.
This problem is aggravated by the fact that to increase power, the anodes of zinc-air cells are made from crushed powdered zinc (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 the performance of the cell.
To date, the greatest success in the field of creating compact zinc-air batteries has been achieved by Zinc Matrix Power (ZMP). ZMP specialists have developed unique technology Zinc Matrix, which made it possible to solve the main problems that arise during battery charging. The essence of this technology is the use of a polymer binder, which ensures unhindered penetration of hydroxide ions, but at the same time blocks the movement of zinc oxide dissolving in the electrolyte. Thanks to the use of this solution, it is possible to avoid noticeable changes 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 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 maximum power 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.
A prototype of a zinc-air battery created by Zinc Matrix Power specialists
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 on the path 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. Under the terms of this agreement, ZMP and Intel will join forces to develop new battery technology for portable PCs. Among the main goals of this work is to increase the battery life of laptops to 10 hours. According to the current plan, the first models of laptops equipped with zinc-air batteries should appear on sale in 2006.
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Electrochemical energy storage technologies are advancing rapidly. NantEnergy company offers a budget zinc-air energy storage battery.
NantEnergy, led by Californian billionaire Patrick Soon-Shiong, has introduced a zinc-air energy battery (Zinc-Air Battery), the cost of which is significantly lower than its lithium-ion counterparts.
Zinc-air energy accumulator
The battery, “protected by hundreds of patents,” is intended for use in energy storage systems in the utility industry. According to NantEnergy, its cost is less than one hundred dollars per kilowatt-hour.
The design of a zinc-air battery is simple. When charging, electricity converts zinc oxide into zinc and oxygen. During the discharge phase in the cell, zinc is oxidized by air. One battery, enclosed in a plastic case, is not much larger in size than a briefcase.
Zinc is not a rare metal, and resource limitations discussed in connection with lithium-ion batteries, zinc-air batteries are not affected. In addition, the latter contain practically no elements harmful to the environment, and zinc is very easily recycled for secondary use.
It is important to note that the NantEnergy device is not a prototype, but production model, which has been tested over the past six years "in thousands of different places." These batteries provided energy to "more than 200 thousand people in Asia and Africa and were used in more than 1,000 towers cellular communication Worldwide".
Such a low cost energy storage system will “transform electrical network into a 24/7, completely carbon-free system,” that is, based entirely on renewable energy sources.
Zinc-air batteries are not new; they were invented back in the 19th century and have been widely used since the 30s of the last century. The main areas of application of these power sources are hearing aids, portable radios, photographic equipment... A certain scientific and technical problem caused by the chemical properties of zinc was the creation of rechargeable batteries. Apparently, this problem has now been largely overcome. NantEnergy has achieved that the battery can repeat the charge and discharge cycle more than 1000 times without degradation.
Among other parameters indicated by the company: 72 hours of autonomy and a 20-year service life of the system.
There are, of course, questions regarding the number of cycles and other characteristics that need to be clarified. However, some energy storage experts believe in the technology. In a GTM survey conducted last December, eight percent of respondents pointed to zinc batteries as a technology that could replace lithium-ion in energy storage systems.
Earlier, the head of Tesla, Elon Musk, reported that the cost of lithium-ion cells (cells) produced by his company could fall below $100/kWh this year.
We often hear that the spread of variable renewable energy sources, solar and wind energy, is supposedly slowing down (will slow down) due to the lack of cheap energy storage technologies.
This, of course, is not the case, since energy storage devices are only one of the tools for increasing the agility (flexibility) of the power system, but not the only tool. In addition, as we see, electrochemical energy storage technologies are developing at a rapid pace. published
If you have any questions on this topic, ask them to the experts and readers of our project.
The new product promises to exceed lithium-ion batteries in energy intensity by three times and at the same time cost half as much.
Note that now zinc-air batteries are produced only in the form of disposable cells or “rechargeable” manually, that is, by changing the cartridge. By the way, this type of battery is safer than lithium-ion batteries, since it does not contain volatile substances and, accordingly, cannot ignite.
The main obstacle to the creation of rechargeable options - that is, batteries - is the rapid degradation of the device: the electrolyte is deactivated, oxidation-reduction reactions slow down and stop altogether after just a few recharge cycles.
To understand why this happens, we must first describe the operating principle of zinc air cells. The battery consists of air and zinc electrodes and electrolyte. During discharge, air coming from outside, with the help of catalysts, forms hydroxyl ions (OH -) in the aqueous electrolyte solution.
They oxidize the zinc electrode. During this reaction, electrons are released, forming a current. While charging the battery, the process goes on reverse side: Oxygen is produced at the air electrode.
Previously, during the operation of a rechargeable battery, the aqueous electrolyte solution often simply dried out or penetrated too deeply into the pores of the air electrode. In addition, the deposited zinc was distributed unevenly, forming a branched structure, which caused short circuits to occur between the electrodes.
The new product is free of these shortcomings. Special gelling and astringent additives control the moisture and shape of the zinc electrode. In addition, scientists have proposed new catalysts, which also significantly improved the performance of elements.
So far, the best performance of prototypes does not exceed hundreds of recharge cycles (photo by ReVolt).
ReVolt chief executive James McDougall believes that the first products, unlike current prototypes, will recharge up to 200 times, and will soon be able to reach 300-500 cycles. This indicator will allow the element to be used, for example, in cell phones or laptops.
Prototype new battery was developed by the Norwegian research foundation SINTEF, and ReVolt is commercializing the product (illustration by ReVolt).
ReVolt is also developing zinc-air batteries for electric vehicles. Such products resemble fuel cells. The zinc suspension in them plays the role of a liquid electrode, while the air electrode consists of a system of tubes.
Electricity is generated by pumping the suspension through the tubes. The resulting zinc oxide is then stored in another compartment. When recharged, it continues along the same path, and the oxide turns back into zinc.
Such batteries can produce more electricity, since the volume of the liquid electrode can be much larger than the volume of the air electrode. McDougall believes that this type of cell will be able to recharge between two and ten thousand times.
Zinc-air batteries are much more reliable than their predecessors: they do not leak. This means that a suddenly deteriorated battery will not damage your 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, you should not remove the packaging from the battery. Before use, 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 charge, regardless of whether it was placed in the device or not.
Zinc-air batteries are a new generation of batteries that have serious advantages over their predecessors. Undoubtedly, they are much more energy efficient and durable due to their larger capacity. The battery cathode is not silver or mercury oxide, as in other batteries, but oxygen obtained from the air. The interaction between the cathode and anode occurs evenly throughout the entire operating life of the battery. The hearing aid will not need to be constantly reconfigured and the volume changed due to a weakened battery. Powdered zinc is used as an anode, which is contained in much larger quantities than the anode in batteries of the previous generation - this ensures its energy intensity.
You can notice a low battery by this characteristic “symptom”: a few minutes after turning on the hearing aid suddenly goes silent. This is a signal that it is time to change the batteries.
- It is recommended to use the battery to the end and then change it immediately. You should not store used batteries.
- Batteries should be selected according to the size specified in the description of the hearing aid.
- Keep batteries away from metal objects! Metal provokes contact closure, 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).
- Inserting new battery, wait a few minutes after tearing off protective film: the active substance must be saturated with oxygen as much as possible. This is necessary for full battery life. If you rush, the anode will become saturated with oxygen only on the surface, and the battery will run out prematurely.
- When you are not using your hearing aid, it should be turned off and the batteries removed.
8.Batteries should be stored in special blisters, at room temperature and out of the reach of children.
