How do I charge and properly operate a lithium-polymer battery?

More and more lithium-polymer batteries are used in modern gadgets. This type of battery has been around recently. Their design and the materials used are gradually being improved. Li─Pol batteries can be found in tablets, some models of smartphones and laptops. They are also widely used in toys and radio controlled models. Quite a few questions come to us about how to charge such batteries. This has already been mentioned in some articles. Since this topic is in great demand, we decided to put it in a separate note.

How to properly charge and operate Li─Pol batteries?

Now directly about how to charge lithium-polymer batteries and their correct operation. First you need to understand that a lithium-polymer battery must have a voltage within certain limits for its entire service life. These limits are in most cases from 2.7 to 4.2 volts. These values ​​correspond to the minimum charge and the maximum.

It is also worth understanding that the capacity of a battery is the amount of stored energy that it gives up when it is completely discharged from a 100% charge. Often these batteries have an upper voltage threshold limited to 4.1 V. This decreases the capacity slightly, but increases the battery life. Indeed, for Li─Pol batteries, borderline states (full charge and discharge) are harmful. This is due to the fact that in this state, lithium ions are maximally incorporated into the crystal lattice of the cathode or anode. Being in such borderline states, even for a short time, negatively affects its service life.

So, you can achieve the maximum service life of a lithium-polymer battery by maintaining its charge level at 40-60 percent. Often rechargeable batteries on the market have approximately this charge level. These limits can be controlled by the user himself, and the minimum and maximum battery charge is controlled by a special board. It is called a charge-discharge controller.

Users can be advised to charge the battery without waiting for a full discharge. Also, do not charge it "to the eyeballs". At 80% charge, it is quite possible to disconnect it from the adapter. It only remains to add that in electronics (tablets, laptops, smartphones), the operation of the controller board is often supplemented by a power circuit in the device itself.

What do users need to keep in mind when charging a battery?

For the user, you can name a number of simple rules when using Li─Pol batteries:

• Don't let your battery run down to a minimum. It is especially not recommended to wait until the phone, tablet, etc. disconnect. If this happens, immediately put the battery on charge;
• Don't be afraid to do frequent recharges. That is, use the power outlet whenever you need it. If the lithium battery is not fully charged, frequent charging will not harm it. You can, for example, use a laptop to charge your phone. To do this, simply plug it into a USB port. You can also replenish the battery charge a little from the cigarette lighter in the car, if there is an appropriate adapter. And it's okay if you don't fully charge the battery. On the contrary, it is the best mode for Li─Pol batteries;
• Battery overcharging may occur even during normal controller operation. The reason for this may be a rise in temperature. For example, the battery is fully charged and the controller has disconnected the battery from charging. If you keep charging your device, it may become slightly warm. Accordingly, the battery will also heat up. Along with the temperature, the battery charge also rises. And this does not contribute to the increase in the service life of the lithium -polymer battery;
• Ideally, the Li─Pol battery should be charged at 50 percent. This is difficult in real life. But maintaining the charge in the range of 30-80 percent is quite realistic.

You ask the question: "What to choose: Li-Ion or Li-Po battery?" We will tell you in detail what is the difference between these two types of batteries.

As we all know, the power of a portable charger depends to a large extent on the quality of the batteries inside the device. On the modern market, there are two types of batteries that are used to produce portable chargers: Li-Ion and Li-Po battery cells.

Li-Ion or Li-Po: What is the Difference and What to Choose

For the information of users, one of the frequently asked questions regarding portable chargers is: what is the difference between Li-Ion and Li-Po batteries, and also which one is better. Let's figure it out.

What are Li-Ion and Li-Po?

Li-Ion is short for lithium ion and Li-Po is for lithium polymer. The endings "ionic" and "polymer" are indications of the cathode. A lithium polymer battery is made up of a polymer cathode and a solid electrolyte, while a lithium ion battery is made up of carbon and a liquid electrolyte. Both batteries are rechargeable, and then, in one sense or another, they both perform the same function. In general, lithium-ion batteries are older than lithium-polymer, but they are still widespread due to their low cost and low maintenance. Lithium-polymer batteries are considered to be more advanced, with improved characteristics, providing a higher level of safety, therefore, such batteries are more expensive than lithium-ion batteries.

There are many configurations for Li-Ion batteries. The most common lithium-ion batteries for portable chargers are 18650 batteries with a diameter of 18mm and a length of 65mm, where 0 means a cylindrical configuration. More than 60% of portable chargers are made from 18650 battery cells. The size and weight of such cells can be easily used in many electronic devices. Manufacturing technologies also do not stand still.

As the demand for lighter and more compact portable chargers grows more and more among buyers, the limitations that lithium-ion batteries entail are becoming increasingly apparent. Therefore, manufacturers are moving towards making lighter, flatter modular lithium polymer batteries for new portable chargers. What's more, lithium polymer batteries are less vulnerable to explosion and therefore no longer need to build a protective layer into portable chargers, while most lithium-ion 18650 batteries only need to be installed with a protective layer.

Let's summarize the differences between lithium ion and lithium polymer in the form of a table.

Key features	Li-Ion	Li-Po
Energy density	High	Low, with fewer cycles compared to Li-Ion
Versatility	Low	High, manufacturers are not tied to a standard cell format
Weight	Slightly heavier	Lungs
Capacity	Below	The same volume of Li-Po battery, almost twice as much in capacity as Li-Ion
Life cycle	Big	Big
Explosion hazard	Higher	Better safety design reduces the risk of overcharging as well as electrolyte leakage
Charge time	Slightly longer	shorter
Wear	Loses less than 0.1% of its effectiveness every month	Slower than Li-Ion batteries
Price	Cheaper	More expensive

After examining all the advantages, disadvantages and characteristics of the two types of batteries, you can make sure that there is no strong competition between them. Although lithium-ion batteries are thinner and sleeker, lithium-ion batteries have a higher energy density and are much cheaper to manufacture.

Therefore, do not pay too much attention to the type of battery, just choose a branded portable charger that suits your needs. After all, many chemicals are added to these batteries, so it remains to be seen which ones will last longer.

Batteries: Li-ion, Li-Pol, Li-ion-pol and the rules for their operation

A bit of history and theory:

The first experiments to create lithium batteries started in 1912 year, but only six decades later, in the early 70s, they first appeared in household devices. Moreover, I emphasize, these were exactly the batteries. Subsequent attempts to develop lithium batteries (rechargeable batteries) have been unsuccessful due to the problems encountered in ensuring their safe operation.

Lithium is the lightest of all metals, has the highest electrochemical potential and provides the highest energy density. Batteries using lithium metal electrodes are capable of providing both high voltage and superior capacity. But as a result of numerous studies in the 80s, it was found that cycling (charge-discharge) of lithium batteries leads to changes on the lithium electrode, reducing thermal stability and causing the potential for thermal state to go out of control. When this happens, the temperature of the cell quickly approaches the melting point of lithium and a violent reaction occurs with the ignition of the evolved gases. For example, a large number of lithium mobile phone batteries shipped to Japan in 1991 were recalled after several incidents of fire and burns.

Due to the instability inherent in lithium, the researchers turned their gaze towards non-metallic lithium batteries based on lithium ions. Having lost a little at the same time in energy density and taking some precautions during charging and discharging, they got safer so-called Li-ion batteries.

The energy density of Li-ion batteries is usually twice the density of standard NiCd, and in the future, with the use of new active materials, it is expected to increase it and achieve a threefold superiority over NiCd. In addition to the large capacity, Li-ion batteries, when discharged, behave similarly to NiCd (their discharge characteristics are similar in shape, and differ only in voltage).

Today there are many varieties of Li-ion batteries., and you can talk for a long time about the advantages and disadvantages of one type or another, but from the consumer point of view, it is not possible to distinguish them by their appearance. Therefore, we note only those advantages and disadvantages that are inherent in all types and consider the reasons that caused the birth of lithium-polymer batteries.

Main advantages:

• High energy density and, as a result, high capacity with the same dimensions compared to nickel-based batteries.
• Low self-discharge.
• High single cell voltage (3.6 V versus 1.2 V for NiCd and NiMH), which simplifies construction, and often the battery consists of only one cell. Many manufacturers today are guided by the use of such a single cell battery for cell phones (remember Nokia). However, to provide the same power, a higher current must be supplied. And this requires ensuring a low internal resistance of the element.
• Low maintenance (running) cost as there is no memory effect and no periodic discharge cycles are required to restore capacity.

And disadvantages:

• The battery requires a built-in protection circuit (which leads to an additional increase in its cost), which limits the maximum voltage on each battery cell during charging and prevents the cell voltage from dropping too low during discharge. In addition, it limits the maximum charge and discharge currents and controls the cell temperature. As a result, the possibility of metallization of lithium is practically excluded.
• The battery is susceptible to aging, even when not in use and just lying on the shelf. The aging process is common in most Li-ion batteries. For obvious reasons, manufacturers are silent about this problem. A slight decrease in capacity is noticeable after one year, regardless of whether the battery was in use or not. After two or three years, it often becomes unusable. However, batteries of other electrochemical systems also have age-related changes with deterioration of their parameters (this is especially true for NiMH exposed to high ambient temperatures). To reduce the aging process, store the battery, charged to about 40% of the nominal capacity, in a cool place, separate from the phone.
• Higher cost compared to NiCd batteries.

Li-ion battery technology is constantly improving. It is updated approximately every six months and it becomes difficult to assess how well new batteries perform after long-term storage.

In a word, everyone is good Li-ion battery, but there are some safety problems and high cost. Attempts to solve these problems led to the emergence of lithium-polymer (Li-pol or Li-polymer) batteries.

Their main difference from Li-ion lies in the name itself and consists in the type of electrolyte used. A dry solid polymer electrolyte was used, similar to a plastic film and not conducting electric current, but allowing the exchange of ions (electrically charged atoms or groups of atoms). The polymer electrolyte effectively replaces the traditional porous electrolyte-impregnated separator used in lithium-ion batteries.

This design simplifies the manufacturing process, is safer and allows the production of thin, freeform batteries. In addition, there is no danger of ignition as there is no liquid or gel electrolyte. With an element thickness of about one millimeter, equipment developers are free to choose a shape, shape and size, up to the point of introducing it into clothing fragments.

But so far, unfortunately, dry Li-polymer batteries have insufficient electrical conductivity at room temperature. Their internal resistance is too high and cannot provide the amount of current required for modern communication devices and power supply to hard drives of laptop computers. At the same time, when heated to 60 ° C or more, the electrical conductivity increases to an acceptable level, but this is not suitable for mass use.

You may ask how it is, Li-polymer batteries are sold on the market with might and main, manufacturers equip phones and computers with them, but we say here that they are not yet ready for commercial use. Everything is very simple. In this case, we are talking about batteries not with a dry solid electrolyte. In order to increase the electrical conductivity of small Li-polymer batteries, some gel electrolyte is added to them. And most of the Li-polymer batteries used for mobile phones today are actually hybrids because they contain a gel-like electrolyte. They are called lithium-ion polymer. But most manufacturers, for promotional and marketing purposes, simply label them as Li-polymer.

First of all, what is the difference between a Li-ion and a Li-polymer battery with the addition of a gel electrolyte? Although the characteristics and efficiency of both systems are very similar, the uniqueness of the Li-ion polymer (you can even call it that) battery is that it still uses a solid electrolyte, which replaces a porous separator. Gel electrolyte is added only to increase ionic conductivity.

All modern phones, smartphones and PDAs are equipped with lithium-based batteries: lithium-ion or lithium-polymer, so in the future we will talk about them. Such batteries have remarkable capacity and service life, but they require very strict adherence to certain operating rules.

These rules can be divided into two groups:

• User independent
• User dependent.

V the first The group includes the fundamental rules for charging and discharging batteries, which are controlled by a device (controller) built into the battery, and also sometimes by an additional controller located in the device itself. These rules are simple:

• The battery must be in a state for its entire life in which its voltage does not exceed 4.2 volts and does not fall below 2.7 volts. These voltages are indications of the maximum (100%) and minimum (0%) charge, respectively. The minimum voltage stated above applies to batteries with coke electrodes, however most modern batteries have graphite electrodes. For them, the minimum voltage is 3 volts.
• The amount of energy given off by the battery when its charge changes from 100% to 0% is its capacity. Some manufacturers limit the maximum voltage to 4.1 volts, while the battery lives longer, but its capacity is reduced by about 10%. Also, sometimes the lower threshold rises to 3.0-3.3 volts, depending on the material of the electrodes, with the same consequences.
• Battery life is greatest at approximately 45 percent charge, and as the charge level increases or decreases, battery life decreases. If the charge is within the limits provided by the battery controller (see above), the change in durability is not significant.
• If, due to circumstances, the voltage on the battery goes beyond the limits indicated above, even for a short time, its lifespan is dramatically reduced. These conditions are called overcharging and overdischarging and are very dangerous for the battery.

Battery controllers designed for different devices, if they (controllers) are made with proper quality, never allow the voltage on the battery during charging to exceed 4.2 volts, but, depending on the purpose of the battery, they can limit the minimum voltage during discharge in different ways. So, in a battery designed for, say, a screwdriver or a motor of a car model, the minimum voltage is likely to be really the minimum acceptable, and for a PDA or smartphone - higher, because the minimum voltage of 2.7-3.0 volts may simply not be enough for the electronics device. Therefore, in complex devices such as telephones, PDAs, etc. the operation of the controller built into the battery itself is complemented by the controller in the device itself.

Let's talk about the process of charging lithium batteries. The charger for any lithium battery is a 5 volt constant voltage source capable of delivering a current equal to approximately 0.5-1.0 battery capacity for charging. So, if the battery capacity is 1000 mA h, the charger must provide a charge current of at least 500 mA, and nominally - 1 ampere.

There are several charging modes for lithium batteries.

Let's start with the standard Sony mode. This mode requires a long charge time, complex controller, but provides the most complete battery charge.

In the first charging stage, lasting approximately 1 hour, the battery is charged with a constant current until the battery voltage reaches 4.2 volts. After that, the second stage begins, which also lasts about an hour, during which the controller, maintaining the voltage on the battery at exactly 4.2 volts, gradually decreases the charging current. When the charging current decreases to a certain value (about 0.2 of the battery capacity), the third stage of charging begins, during which the charging current continues to decrease, and the voltage at the battery terminals remains at the same level - 4.2 volts. The third stage, unlike the first two, has a strictly defined duration determined by the timer built into the controller - 1 hour. After the third stage, the controller completely disconnects the battery from the charger.

The state of charge of the battery at the end of the first stage is 70%, at the end of the second - 90%, and at the end of the third - 100%.

Many companies, seeking to reduce the cost of their devices, use simplified battery charging modes, for example, stopping charging when the voltage on the battery reaches 4.2 volts, that is, using only the first stage of charging. In this case, the battery charges quickly, but, alas, only up to 70% of its real capacity. It is not difficult to determine that your device has just such a simplified controller - it takes about 3 hours to fully charge, no less.

To the second group includes operating rules that we can influence, thereby significantly increasing or decreasing the battery life. These rules are as follows:

• you need to try not to bring the battery to a minimum charge and, moreover, to a state where the machine turns itself off, well, if this happens, then you need to charge the battery as soon as possible.
• there is no need to be afraid of frequent recharges, including partial ones, when the full charge is not reached - this does not harm the battery.

contrary to the opinion of many users, overcharging harms lithium batteries no less, but even more than a deep discharge. The controller, of course, limits the maximum charge level, but there is one subtlety. It is well known that battery capacity is temperature dependent. So, if, for example, we charged the battery at room temperature and received a 100% charge, then when we go out into the cold and the machine cools down, the state of charge of the battery can drop to 80% and below. But the opposite situation may also be. A battery charged at room temperature to 100%, being slightly heated, will become charged, say, up to 105%, and this is very, very unfavorable for it. Such situations occur when using a typewriter, long time located in the cradle. During operation, the temperature of the device and with it the battery rises, but the charge is already full ...

In this regard, the rule says: if you need to work in the cradle, first disconnect the machine from the charger, work on it, and when it reaches the “combat” temperature regime, connect the charger.

By the way, this rule also applies to owners of laptops and other gadgets.

Ideal conditions for long-term storage of the battery- this is being outside the device with a charge of about 50%. A working battery does not require taking care of itself for months (about six months).

And finally, some more information.

• - Contrary to popular belief, lithium batteries, unlike nickel ones, have almost no “memory effect”, therefore, the so-called “training” of a new lithium battery makes little sense. To calm yourself down, it is enough to fully charge and discharge a new battery once or twice. This is required to calibrate the optional controller.
• - Device owners know that the battery can be charged from both the charger and USB. At the same time, the impossibility of charging from USB is often perplexing. The fact is that according to the “law”, the USB controller must supply the peripheral devices connected to it with a current of about 500 mA. However, there are situations when either the controller itself cannot provide such a current, or the device is connected to a USB controller, on which some peripheral is already hanging that consumes part of the power. So there is not enough current for charging, especially if the battery is too discharged.
• - Lithium batteries DO NOT LIKE FREEZING. Always try to avoid using the clipper in extreme cold - you get carried away and the battery will have to be replaced. Of course, if you took the machine out of the warm inner pocket of your jacket and made a couple of notes or calls, and then put the animal back, there will be no problems.
• - Practice shows that lithium batteries (not only accumulators) decrease their capacity with a decrease in atmospheric pressure (in the highlands, in an airplane). This does not harm the batteries, but you should be aware of this.
• - It happens that after purchasing a battery of increased capacity (say, 2200 mA h instead of the standard 1100 mA h), after a couple of days of using a new battery, the machine starts behaving strangely: it hangs, turns off, the battery seems to be charging, but somehow strange, etc. It is possible that your charger, which successfully works on a “native” battery, is simply not able to provide sufficient charging current for a large-capacity battery. The way out is to purchase a charger with a large current output (say, 2 amperes instead of the previous 1 ampere).

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Features of lithium-polymer batteries and rules for their operation

The lithium-polymer battery is a modified version of the lithium-ion battery. The main difference lies in the use of a polymer material that acts as an electrolyte. Conductive inclusions with lithium compounds are added to this polymer. Such batteries have been actively developed in recent years and are used in mobile phones, tablets, laptops, radio-controlled models and other equipment. Despite the fact that lithium batteries are not capable of providing high discharge currents, some special types of polymer batteries can deliver a current that significantly exceeds their capacity. Since lithium polymer batteries are rapidly spreading in the market, you need to have an understanding of their design, rules of operation and safety when handling them. This will be discussed in our today's material.

The advantage of replacing the liquid organic electrolyte with a polymer one is the increased safety of battery operation. This is very important for lithium-type batteries. It was safe commercial use that held back their development from the outset. In addition, the polymer electrolyte gives you much more freedom in choosing the shape of the battery.

The Li-Pol storage battery device is based on the process of transition of a number of polymers into a semiconducting state when electrolyte ions are introduced into them. In this case, the conductivity increases several times. Researchers were mainly engaged in the selection of polymer electrolyte for batteries with metal lithium and Li─Ion models. In theory, an increase in the energy density of batteries with polymer is allowed by several times in comparison with lithium ion batteries. Today, there are several groups of Li-Pol batteries that differ in the composition of the electrolyte:

• With a gel-like homogeneous electrolyte. It is obtained as a result of the introduction of lithium salts into the structure of the polymer;
• With dry polymer electrolyte. This type is made on the basis of polyethylene oxide with various lithium salts;
• Electrolyte in the form of a microporous polymer matrix, in which non-aqueous solutions of lithium salts are sorbed.

If we compare polymer and liquid electrolyte, then it is worth noting the lower ionic conductivity of the former. It decreases significantly at negative temperatures. So, one problem was to find a composition for a high conductivity electrolyte. And the second important task was to expand the operating temperature range of polymer batteries. Models of lithium-polymer batteries used in modern technology are not inferior in their characteristics to Li-Ion.

Since there is no liquid electrolyte in a polymer battery, their operational safety is much higher. In addition, they can be made in almost any shape and configuration.

Containers of some models, in which the can itself is located, are made of metallized polymer. Due to the crystallization of the polymer electrolyte, the parameters of these batteries are significantly reduced at negative temperatures.

There are developments of polymer batteries with a metal anode. Scientists managed to achieve a high current density and a significant expansion of the operating temperature range. These types of rechargeable batteries can also be used in various portable electronics and home appliances. Many leading companies are already engaged in the production of such batteries.

Moreover, different manufacturers may differ in electrode materials, electrolyte composition and assembly technology itself. For this reason, the parameters of these batteries are also very different. However, all manufacturers agree that the stability of Li─Pol is strongly influenced by the homogeneity of the polymer electrolyte. And it depends on the polymerization temperature and the ratio of the components.

Now there are already many experiments that prove a higher level of safety of polymer batteries in comparison with ionic ones. This includes overcharging, overcharging, vibration, shrinking, short circuiting, and piercing of lithium ─ polymer batteries. So, this type of battery has the best development prospects. Below are the results of tests for the safe operation of Li─Pol batteries.

Test type
Test type	Gel polymer electrolyte battery	Liquid electrolyte battery
Needle puncture	There were no changes	Explosion, smoke, electrolyte leakage, temperature rise up to 250 ° С
Heating up to 200 ° С	There were no changes	Explosion, electrolyte leak
Short circuit current	There were no changes	Electrolyte leakage, temperature rise by 100 ° С
Reload (600%)	Bloating	Explosion, electrolyte leakage, temperature rise by 100 ° С

There are examples of lithium-polymer batteries that are 1 millimeter thick. Such models allow mobile designers to create very compact hardware. This opens up new possibilities for reducing the size of electronic devices. To reduce the internal resistance of Li-Pol batteries, a gel electrolyte is added. Batteries used in mobile phones use this type of electrolyte. They combine the features of polymer and ionic batteries.

What is the difference between Li─Ion and Li─Pol rechargeable batteries. They belong to and are close in their electrical characteristics. But polymer models use a solid electrolyte. The gel component is introduced into the electrolyte to reduce the internal resistance of the battery and stimulate ion exchange processes.

In terms of their energy capacity, lithium-polymer storage batteries have a specific energy content 4-5 times higher and 3-4 times higher. Both of these types belong to. Comparison is made with them, since basically lithium batteries have replaced alkaline batteries in mobile electronics.

Li-Pol batteries have a service life of 500-600 charge-discharge cycles (at a discharge current of 2C). According to this indicator, they are inferior to cadmium ones (1 thousand cycles) and approximately correspond to metal hydride ones. The production technology and design are constantly being improved and in the future, perhaps, the characteristics will improve. It is also worth noting that polymer battery loses about 20% of its capacity in 1-2 years. According to this parameter, they correspond to ionic batteries.

It should be noted that there are 2 broad categories among polymer batteries for commercial use. These are regular and fast-discharge ones. The latter are often called Hi discharge. The difference between these groups lies in the maximum permissible discharge current. It can be indicated in absolute value or in multiples of the nominal capacity.

For example, 3C. For conventional storage batteries, the maximum discharge current is no more than 3 - 5C. Fast-discharge models have a maximum discharge current of 8-10C. The weight of the fast-discharge batteries is approximately 20 percent higher than that of standard models. These batteries are labeled with HC or HD.

KKM2500 stands for a regular model with a capacity of 2500 mAh, and the KKM2000HD label stands for a 2000 mAh fast-discharge battery. Fast discharge models are not used in home appliances and consumer electronics. Batteries from cell phones and tablets cannot withstand high discharge currents, and therefore are equipped with protection against such operating modes.

The areas of application of lithium-polymer batteries stem from the tasks that were set during their development. This is an increase in the operating time of the device and a decrease in its weight. Standard Li─Pol models operate in various electronics with low consumption currents. These are laptops, smartphones, e-books, tablets.

Models that provide a fast discharge are also called "power" models. They are used in those devices where high current consumption is required. The most famous field of application for "power" batteries is radio-controlled models. This market is the most attractive for polymer battery manufacturers. In the field of devices with very high discharge currents (up to 50 C), lithium-polymer batteries are inferior to alkaline ones. Perhaps in the future, lithium models will overcome this limitation. In terms of price, they roughly correspond to nickel-metal hydride.

Handling lithium ─ polymer batteries

Safety

Lithium-type batteries in general, and polymer in particular, require rather delicate handling during operation. What you need to remember when using Li─Pol batteries:

• Excessive battery charge is harmful (above 4.2 volts per battery cell);
• A short circuit must not be allowed;
• Discharge by currents that lead to heating of the battery over 60 degrees Celsius is inadmissible;
• It is impossible to depressurize the battery;
• Do not discharge the battery below 3 volts;
• Heating above 60 degrees is unacceptable;
• Discharged storage is not allowed.

Failure to follow these rules can lead to a fire at worst, and a significant loss of capacity at best.

In this regard, you can give several recommendations for the safe use of lithium-polymer batteries. First you need to purchase a high-quality charger and set the correct settings on it. In addition, it is recommended to use connectors that do not allow short circuits. Be sure to control the current that is consumed by the device.

It is also worth noting that it is necessary to observe the temperature regime and prevent overheating of the polymer battery. This is the weak point of all lithium-type batteries. If the battery heats up to 70 degrees, then a spontaneous reaction begins in it, which converts energy into heat. The result is ignition and sometimes explosion. If it is possible to control the voltage of the battery, then it should be monitored especially closely at the end of the discharge.

Another reason for the failure of lithium batteries is depressurization. Under no circumstances should air enter the inside of the polymer battery can. The case is initially sealed and should not be subjected to shock or dropped. If you are soldering leads, then this must be done extremely carefully.

Before sending the polymer battery for storage, it is recommended to charge it halfway. Store the battery in a cool place out of direct sunlight. Like all rechargeable batteries, lithium-polymer batteries have a self-discharge rate, but it is less than that of lead or alkaline ones.

Lithium polymer batteries represent an improved design of the world renowned lithium-ion batteries. It is planned that these devices will soon completely displace nickel-metal-hydride and nickel-cadmium devices from the market. accumulators... Lithium polymer cells are increasingly being used in a wide variety of electronic devices as a power source. With the same weight in terms of energy capacity, they are several times superior to nickel-metal-hydride and nickel-cadmium designs.

Potentially, lithium-polymer cells will cost less than lithium-ion batteries. However, at the moment they are still quite expensive. At the moment, only a few large firms are engaged in their production. They are similar in design to lithium-ion cells, but they use a helium electrolyte. As a result, they are released by a low discharge current, significant energy density, and a significant number of charge and discharge cycles. Their shape can be very different, and they themselves are distinguished by their light weight and compactness.

Kinds

At the moment, lithium-polymer batteries can be of several types, which differ in the structure of the electrolyte:

• Elements having gel-like homogeneous electrolyte , which is created by the introduction into the composition of polymer lithium salts.
• Elements having dry polymer electrolyte ... This type is made on the basis of polyethylene oxide using a variety of lithium salts.
• Having polymer matrix electrolyte having a microporous structure. It contains non-aqueous components of lithium salts.

Due to the fact that a liquid electrolyte is used in a polymer cell, their operational safety is an order of magnitude higher. In addition, they can be manufactured in various shapes and configurations.

Some lithium polymer cells are made of metallic polymer. However, at low temperatures, the parameters of such batteries are significantly reduced due to polymer crystallization.

There are developments in polymer batteries where a metal anode is used. Some companies have managed to obtain a significant expansion of the operating temperature range and current density. These types of batteries can be used in various household appliances and electronics.

At the same time, different manufacturers use different electrode materials, electrolyte structure and assembly technology. As a result, the manufactured batteries can have completely different parameters. But all companies producing such batteries note that the stability of the functioning of lithium-polymer batteries ensures the uniformity of the electrolyte from the polymer. This, in turn, depends on the number of components, as well as the polymerization temperature.

There are already versions of batteries that are only 1 millimeter thick. This allows manufacturers to produce very compact mobile devices.

Also, lithium polymer batteries that are commercially available are divided into:

• Regular.
• Fast-discharge.

Device

Lithium polymer batteries work on the principle of moving a number of polymer elements into semiconducting substances, provided that electrolyte ions are included in them. As a result, there is a significant increase in conductivity. According to the device, these batteries are emitted by an electrolytic composition.

The essence of polymer technology is that the electrolyte is applied to a plastic film. It does not allow electricity to be conducted, but it makes it possible to exchange ions. In other words, the polymer electrolyte replaces the conventional porous separator impregnated with liquid electrolyte. Thanks to the dry polymer structure, it is possible to ensure a minimum cell thickness of about 1 mm, safety of use and ease of production. Thanks to this design, developers have the opportunity to integrate such batteries into shoes, clothing, miniature equipment and other devices.

But a dry polymer battery has disadvantages in the form of a decrease in the conductivity and internal resistance of polymers, which is unacceptable for a number of powerful mobile devices. To make the small polymer battery more advanced, a certain percentage of gel cells are added to the electrolyte. Most of the commercial batteries currently used in cell phones are polymer-gel hybrids. Hybrid batteries are by far the most popular.

Operating principle

Lithium-polymer batteries have a principle of action similar to lithium-ion cells, that is, they operate on the reversibility of a chemical reaction. Here, the anode is a material made of carbon, where lithium ions are embedded. Oxides of vanadium, manganese or cobalt are used in the cathode. The operation of such a battery is based on the ability of polymers to pass into a semiconducting state due to the inclusion of electrolytic ions in them.

Lithium salts are still used here as the chemical base of the electrolyte. However, they are located in a corresponding polymer spacer that is located between the cathode and anode. Thanks to this, lithium polymer batteries can be made in any arbitrary shape. They can be placed in various inaccessible places, which opens up new possibilities for electronics manufacturers.

Application

Lithium polymer batteries are increasingly being used. Such batteries can significantly increase the operating time of the device while reducing the weight of the battery. Thanks to this, it is possible to obtain an energy carrier that will be several times larger in capacity. Even better performance will be achieved with fast discharge batteries. Therefore, such batteries become an excellent option for radio-controlled models of airplanes and helicopters, including other radio-controlled devices.

Application Li-Pol rechargeable batteries makes it possible to reduce the weight of the battery and increase the period of operation of the devices. Lithium polymer batteries have proven their worth in small helicopters such as the Piccolo. Such devices are capable of flying on such batteries for 30 minutes or more. These elements are a good option for small flying structures.

Typical lithium polymer batteries are used as power supplies that are required for electronic devices that draw relatively little current. These can be laptops, smartphones, and so on. Fast-discharge batteries are used in devices where high current consumption is required. Similar batteries are used in modern, portable power tools and radio-controlled devices.

Limitations of use

These batteries will be widely used in the automotive industry in the future. Today they are used to create new technologies and test electric vehicles. However, there are certain limitations that prevent the use of these batteries everywhere.

• Lithium polymer batteries require a special charging mode. In principle, this is not difficult, but the usual cannot be used for this. This is due to the fact that they are distinguished by a fire hazard during the over-discharge period. To combat this phenomenon, all such batteries have an electronic system that prevents over-discharge and overheating.
• If the lithium polymer battery is misused, it may cause a fire.
• A lithium polymer battery should not be used immediately after charging. First, it should be cooled to ambient temperature. Otherwise, the battery may be damaged.
• Inadmissible short circuit.
• Depressurization of the battery is not allowed.
• Battery discharge below 3 volts.
• Do not heat above 60 degrees.
• Batteries should not be exposed to microwaves or pressure. This can lead to the appearance of smoke, fire and more serious consequences.
• It is necessary to protect the battery from damage and shock. Strong mechanical stress can lead to disruption of the internal structure.

However, these disadvantages do not prevent their use in a wide variety of areas. In the future, all these shortcomings will be leveled by the introduction of new technologies and developments.

The advantages of lithium polymer batteries

• Quite high energy density.
• Small self-discharge parameter.
• There is no memory effect.
• Lithium polymer batteries are somewhat superior to lithium counterparts in battery capacity and duration of use.
• Manufacturing batteries with a thickness of only one millimeter.
• Applications in a fairly wide temperature range: from minus 20 to plus 40 degrees Celsius.
• The ability to shape the battery into different shapes.
• Small voltage drop during discharge.