Long time scope of application zinc air batteries did not go beyond medicine. Their high capacity and long service life (in an inactive state) allowed them to easily occupy the niche of disposable batteries for hearing aids. But in recent years there has been a large increase in interest in this technology among automakers. Some believe that an alternative to lithium has been found. Is it so?

A zinc-air battery for an electric vehicle can be designed as follows: electrodes are inserted into a container divided into compartments, on which air oxygen is adsorbed and reduced, as well as special removable cassettes filled with anode consumables, in this case zinc granules. A separator is placed between the negative and positive electrodes. An aqueous solution of potassium hydroxide or a solution of zinc chloride can be used as an electrolyte.

Air coming from outside with the help of catalysts forms hydroxyl ions in the aqueous electrolyte solution, which oxidize the zinc electrode. During this reaction, electrons are released, forming an electric current.

Advantages

World zinc reserves are estimated to be approximately 1.9 gigatons. If we start global production of zinc metal now, then in a couple of years it will be possible to assemble a billion zinc-air batteries with a capacity of 10 kWh each. For example, it would take more than 180 years to create the same amount under current lithium mining conditions. The availability of zinc will also reduce the price of batteries.

It is also very important that zinc air cells, having a transparent scheme for recycling waste zinc, are environmentally friendly products. The materials used here do not poison the environment and can be recycled. The reaction product of zinc air batteries (zinc oxide) is also absolutely safe for humans and their environment. It’s not for nothing that zinc oxide is used as the main component in baby powder.

The main advantage, thanks to which electric vehicle manufacturers look at this technology with hope, is the high energy density (2-3 times higher than that of li-ion). Already, the energy intensity of Zinc-Air reaches 450 Wh/kg, but the theoretical density can be 1350 Wh/kg!

Flaws

Since we don't drive electric vehicles with zinc-air batteries, there are disadvantages. Firstly, it is difficult to make such cells rechargeable with a sufficient number of discharge/charge cycles. During operation of a zinc-air battery, the electrolyte simply dries out or penetrates too deeply into the pores of the air electrode. And since the deposited zinc is distributed unevenly, forming a branched structure, short circuits often occur between the electrodes.

Scientists are trying to find a way out. The American company ZAI solved this problem by simply replacing the electrolyte and adding fresh zinc cartridges. Naturally, this will require a developed infrastructure of gas stations, where the oxidized active material in the anode cassette will be replaced with fresh zinc.

And although the economic component of the project has not yet been worked out, manufacturers claim that the cost of such “charging” will be significantly lower than refueling a car with an internal combustion engine. In addition, the process of changing the active material will require no more than 10 minutes. Even the super-fast ones will be able to replenish only 50% of their potential during the same time. Last year, the Korean company Leo Motors already demonstrated ZAI zinc-air batteries on its electric truck.

Swiss technology firm ReVolt is also working on improving the Zinc-Air battery. She proposed special gelling and astringent additives that control the moisture and shape of the zinc electrode, as well as new catalysts that significantly improve the performance of the cells.

However, engineers from both companies failed to overcome the mark of 200 Zinc-Air discharge/charge cycles. Therefore, it is too early to talk about zinc-air cells as electric vehicle batteries.

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”) galvanic cell in which zinc is the anode ... Wikipedia

Oxyride Battery Oxyride™ batteries are a brand name for disposable (non-rechargeable) batteries developed by Panasonic. They are designed specifically for devices with high power consumption... Wikipedia

The normal Weston element, the mercury-cadmium element, is a galvanic element, the emf of which is very stable over time and reproducible from instance to instance. Used as a reference voltage source (VR) or voltage standard... ... Wikipedia

SC 25 Silver-zinc battery is a secondary chemical current source, a battery in which the anode is silver oxide, in the form of a pressed powder, the cathode is a mixture ... Wikipedia

Miniature batteries of various sizes A miniature battery, a battery the size of a button, was first widely used in electronic wristwatches, therefore it is 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 galvanic cell in which manganese dioxide is used as the cathode, powdered zinc as the anode, and an alkali solution, usually potassium hydroxide, as the electrolyte. Contents 1 History of invention ... Wikipedia

A nickel-zinc battery is a chemical current source in which zinc is the anode, potassium hydroxide with the addition of lithium hydroxide is the electrolyte, and nickel oxide is the cathode. Often abbreviated NiZn. Advantages: ... ... Wikipedia

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 the resource constraints discussed in connection with lithium-ion batteries do not affect zinc-air batteries. In addition, the latter contain practically no elements harmful to the environment, and zinc is very easily recycled for secondary use.

It's important to note that the NantEnergy device is not a prototype, but a production model that has been tested over the past six years "in thousands of different locations." These batteries provided power to “more than 200,000 people in Asia and Africa and were used in more than 1,000 cell phone towers around the world.”

Such a low cost energy storage system will make it possible to “transform the electrical grid into a 24/7, 100% 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.

Of course, there are 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 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 increasing popularity of mobile phones. In turn, the rapid growth in the number of portable electronic devices has caused a significant 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 the elements and the power of the microprocessors used in them increases; 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 high-resolution color displays with larger screen sizes. 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 make it possible to create laptops that are practically not inferior in their 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 increasing the battery life of portable PCs is to switch 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). 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 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 during the operation of the cell, 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 obtain a higher supply voltage, several cells connected in series can be combined 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 the low self-discharge rate in the non-activated state and the small change in voltage during discharge (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 of large size and power (for example, intended to power vehicle power plants), 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 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 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 a unique Zinc Matrix technology, which has solved 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 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.

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.

In the fifth issue of our magazine, we told you how to make a gas battery yourself, and in the sixth, a lead-potash one. We offer readers another type of current source - a zinc-air 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 specific power of a zinc air cell can reach 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 zinc air element is

small change in voltage under load as it is discharged. In addition, such an element has significant strength, since its vessel can be made of steel.

The operating principle of zinc air elements is based on the use of an electrochemical system: zinc - caustic potassium solution - activated carbon, which adsorbs air oxygen. 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.