What is the difference between a lithium polymer battery and an ion battery? Li-Ion or Li-Po: What is the difference and what to choose

Technical progress is a machine that rolls without stopping! The fuel for this machine is more and more new problems of our modern world. Remember, not so long ago nickel-cadmium (NiCd) batteries were in use, they were replaced by nickel-metal hydride (NiMH). But today lithium-ion (Li-ion) batteries are trying to take the place of lithium-polymer (Li-pol) batteries. What is the difference between Li-pol and Li-ion? What are the advantages of lithium polymer over lithium ion batteries? Let's try to figure it out.

When we buy a phone or tablet, few people ask themselves the question - what kind of battery is inside? Only later, when faced with the problem of quickly discharging the gadget, do we begin to take a more detailed look at the “inside” of our device.

Lithium batteries became known in 1912, when the first experiments began, but they were not widely used. And only in the 70s, six decades later, these charging elements took their place in almost all household devices. Let us emphasize that for now we are talking only about batteries, not rechargeable batteries.

Lithium is the lightest metal, it also provides the highest energy density and has significant electrochemical potential. Batteries, which are based on lithium metal electrodes, have a large capacity and high voltage. In the 80s, as a result of numerous studies, it turned out that the cyclic operation of lithium batteries (charge/discharge process) leads to the ignition of chargers, and after them, the gadgets themselves. So, in 1991, several thousand phones were recalled in Japan due to a fire hazard. Because of these dangerous properties of lithium, scientists have turned all their efforts to non-metallic lithium batteries based on lithium ions. And after some time, a safer version of the charger was created, which was called lithium-ion (Li-ion).

Today, the lithium-ion battery is found in almost all mobile devices, it has a large number of varieties, has a lot of positive qualities, but also disadvantages, which we will talk about in more detail.

Advantages of lithium-ion batteries:

High energy density and, as a result, high capacity

Low self-discharge

High voltage of a single element. This simplifies the design - often the battery consists of only one element. Many manufacturers today use just such a single-cell battery in cell phones (remember Nokia)

Low cost of maintenance (operating costs)

No memory effect requiring periodic discharge cycles to restore capacity.

Flaws:

The battery requires a built-in protection circuit (which further increases its cost) that limits the maximum voltage across each battery cell during charging and prevents the cell voltage from dropping too low when discharging

The battery is subject to aging, even if not used and just sitting on a shelf. The aging process is typical for most Li-ion batteries. For obvious reasons, manufacturers are silent about this problem. A slight decrease in capacity becomes noticeable after just a year, regardless of whether the battery has been in use or not. After two or three years it often becomes unusable

Higher cost compared to NiCd batteries.

Lithium-ion batteries are constantly being improved, technology is improving. And this battery would be good for everyone if it were not for the safety problems associated with its use and the high price. All these reasons became the basis for the creation lithium polymer batteries (Li-pol or Li-polymer). The most obvious and most basic difference between Li-pol and Li-ion is the type of electrolyte used. The use of solid polymer electrolyte significantly reduces the cost of creating a battery and makes it safer, and also allows you to create thinner chargers. Why hasn't the lithium-polymer battery completely replaced its predecessor? One of the possible versions expressed by experts is that investors who have invested large sums in the development and mass introduction of Li-ion batteries are trying to return the investment.

Let's summarize. Generally speaking, a lithium polymer battery is a more advanced version of a lithium-ion battery. Judge for yourself:

Advantages of Li-pol and Li-ion batteries

To summarize, we can say that, thanks to modern technology, we have two types of reliable external batteries. With the development of mobile technologies, with the advent of smartphones, tablets and many other digital gadgets, with the creation of energy-intensive applications, users are faced with the problem of a “dead battery”. Of course, both Li-ion and Li-Pol batteries immediately found their use in external chargers.

This is an excellent solution for modern life. The most important thing when choosing a powerbank is not to run into scammers (we wrote more about how to distinguish a fake from an original , but about how to understand with 100% certainty from a store’s website that they will sell you a fake -

Growing consumer interest in mobile gadgets and technologically advanced portable equipment in general is forcing manufacturers to improve their products in a variety of directions. At the same time, there are a number of general parameters, work on which is carried out in the same direction. These include the method of energy supply. Just a few years ago, active market participants could observe the process of displacement by more advanced elements of nickel-metal hydride origin (NiMH). Today, new generations of batteries are competing with each other. The widespread use of lithium-ion technology in some segments is being successfully replaced by the lithium-polymer battery. The difference from the ionic one in the new unit is not so noticeable for the average user, but in some aspects it is significant. At the same time, as in the case of competition between NiCd and NiMH elements, the replacement technology is far from flawless and in some respects is inferior to its analogue.

Li-ion battery device

The first models of serial lithium-based batteries began to appear in the early 1990s. However, cobalt and manganese were then used as the active electrolyte. In modern ones, it is not so much the substance that is important, but the configuration of its placement in the block. Such batteries consist of electrodes that are separated by a separator with pores. The mass of the separator, in turn, is impregnated with electrolyte. As for the electrodes, they are represented by a cathode base on aluminum foil and a copper anode. Inside the block they are connected to each other by current collector terminals. Charge maintenance is performed by the positive charge of the lithium ion. This material is advantageous in that it has the ability to easily penetrate the crystal lattices of other substances, forming chemical bonds. However, the positive qualities of such batteries are increasingly turning out to be insufficient for modern tasks, which led to the emergence of Li-pol cells, which have many features. In general, it is worth noting the similarity of lithium-ion power supplies with full-size helium batteries for cars. In both cases, the batteries are designed to be physically practical to use. In part, this direction of development was continued by polymer elements.

Lithium polymer battery design

The impetus for improving lithium batteries was the need to combat two shortcomings of existing Li-ion batteries. Firstly, they are unsafe to use, and secondly, they are quite expensive. Technologists decided to get rid of these disadvantages by changing the electrolyte. As a result, the impregnated porous separator was replaced by a polymer electrolyte. It should be noted that the polymer has previously been used for electrical needs as a plastic film that conducts current. In a modern battery, the thickness of the Li-pol element reaches 1 mm, which also removes restrictions on the use of various shapes and sizes from developers. But the main thing is the absence of liquid electrolyte, which eliminates the risk of ignition. Now it’s worth taking a closer look at the differences from lithium-ion cells.

What is the main difference from an ion battery?

The fundamental difference is the abandonment of helium and liquid electrolytes. For a more complete understanding of this difference, it is worth turning to modern models of car batteries. The need to replace the liquid electrolyte was, again, due to safety interests. But if in the case of car batteries progress stopped at the same porous electrolytes with impregnation, then lithium models received a full-fledged solid base. What is so good about a solid-state lithium polymer battery? The difference from the ionic one is that the active substance in the form of a plate in the contact zone with lithium prevents the formation of dendrites during cycling. This factor eliminates the possibility of explosions and fires of such batteries. This is only about the advantages, but there are also weaknesses in the new batteries.

Lithium polymer battery life

On average, such batteries can withstand about 800-900 charging cycles. This indicator is modest compared to modern analogues, but not even this factor can be considered as determining the resource of an element. The fact is that such batteries are subject to intensive aging, regardless of the nature of use. That is, even if the battery is not used at all, its life will be reduced. It does not matter whether it is a lithium-ion battery or a lithium-polymer cell. All lithium based power supplies are characterized by this process. A significant loss in volume can be noticed within a year after acquisition. After 2-3 years, some batteries completely fail. But a lot depends on the manufacturer, since within the segment there are also differences in the quality of the battery. Similar problems occur with NiMH cells, which are subject to aging due to sudden temperature fluctuations.

Flaws

In addition to problems with rapid aging, such batteries require an additional protection system. This is due to the fact that internal tension in different areas can lead to burnout. Therefore, a special stabilization circuit is used to prevent overheating and overcharging. This same system also entails other disadvantages. The main one is current limitation. But, on the other hand, additional protective circuits make the lithium polymer battery safer. There is also a difference from ionic in terms of cost. Polymer batteries are cheaper, but not by much. Their price tag also increases due to the introduction of electronic protection circuits.

Operational features of gel-like modifications

In order to increase electrical conductivity, technologists still add a gel-like electrolyte to polymer elements. There is no talk of a complete transition to such substances, since this contradicts the concept of this technology. But in portable technology, hybrid batteries are often used. Their peculiarity is sensitivity to temperature. Manufacturers recommend using these battery models in conditions ranging from 60 °C to 100 °C. This requirement also determined a special niche of application. Gel-type models can only be used in places with a hot climate, not to mention the need to be immersed in a heat-insulated case. Nevertheless, the question of which battery to choose - Li-pol or Li-ion - is not so pressing in enterprises. Where temperature has a particular influence, combined solutions are often used. In such cases, polymer elements are usually used as reserve elements.

Optimal charging method

The usual recharge time for lithium batteries is on average 3 hours. Moreover, during the charging process the unit remains cold. Filling occurs in two stages. At the first, the voltage reaches peak values, and this mode is maintained until it reaches 70%. The remaining 30% is gained under normal stress conditions. Another interesting question is how to charge a lithium-polymer battery if you need to constantly maintain its full capacity? In this case, you should follow the recharging schedule. It is recommended to carry out this procedure approximately every 500 hours of operation with a full discharge.

Precautionary measures

During operation, you should only use a charger that meets the specifications, connecting it to a network with a stable voltage. It is also necessary to check the condition of the connectors so that the battery does not open. It is important to consider that, despite the high degree of safety, this is still an overload-sensitive type of battery. The lithium-polymer cell does not tolerate excessive current, excessive cooling of the external environment and mechanical shock. However, according to all these indicators, polymer blocks are still more reliable than lithium-ion ones. Still, the main aspect of safety lies in the harmlessness of solid-state power supplies - of course, provided that they are kept sealed.

Which battery is better - Li-pol or Li-ion?

This issue is largely determined by the operating conditions and the target energy supply facility. The main benefits of polymer devices are more likely to be felt by manufacturers themselves, who can more freely use new technologies. For the user, the difference will be barely noticeable. For example, in the question of how to charge a lithium polymer battery, the owner will have to pay more attention to the quality of the power supply. In terms of charging time, these are identical elements. As for durability, the situation in this parameter is also ambiguous. The aging effect characterizes polymer elements to a greater extent, but practice shows different examples. For example, there are reviews about lithium-ion cells that become unusable after just a year of use. And polymer ones in some devices are used for 6-7 years.

Conclusion

There are still many myths and false opinions around batteries that relate to various nuances of operation. On the contrary, some battery features are hushed up by manufacturers. As for the myths, one of them is refuted by the lithium polymer battery. The difference from the ionic analogue is that polymer models experience less internal stress. For this reason, charging sessions for batteries that have not yet run out do not have a harmful effect on the characteristics of the electrodes. If we talk about the facts hidden by manufacturers, then one of them concerns durability. As already mentioned, battery life is characterized not only by a modest rate of charging cycles, but also by the inevitable loss of the useful volume of the battery.

Lithium-ion and lithium-polymer batteries

Engineering thought is constantly evolving: it is stimulated by constantly emerging problems that require the development of new technologies to be solved. At one time, nickel-cadmium (NiCd) batteries were replaced by nickel-metal hydride (NiMH), and now lithium-ion (Li-ion) batteries are trying to take the place of lithium-ion (Li-ion) batteries. NiMH batteries have to some extent supplanted NiCd, but due to such undeniable advantages of the latter as the ability to deliver high current, low cost and long service life, they could not provide their full replacement. But what about lithium batteries? What are their features and how do Li-pol batteries differ from Li-ion? Let's try to understand this issue.

As a rule, when buying a mobile phone or laptop computer, we all don’t think about what kind of battery is inside and how these devices differ in general. And only then, having encountered in practice the consumer qualities of certain batteries, do we begin to analyze and choose. For those who are in a hurry and want to immediately get an answer to the question of which battery is optimal for a cell phone, I will answer briefly - Li-ion. The following information is intended for the curious.

First, a short excursion into history.

The first experiments on creating lithium batteries began in 1912, but it was only six decades later, in the early 70s, that they were first introduced into household devices. Moreover, let me emphasize, these were just batteries. Subsequent attempts to develop lithium batteries (rechargeable batteries) failed due to safety concerns. Lithium, the lightest of all metals, has the greatest electrochemical potential and provides the greatest energy density. Batteries using lithium metal electrodes offer both high voltage and excellent capacity. But as a result of numerous studies in the 80s, it was found that cyclic operation (charge - discharge) of lithium batteries leads to changes in the lithium electrode, as a result of which thermal stability decreases and there is a threat of the thermal state getting out of control. When this happens, the temperature of the element quickly approaches the melting point of lithium - and a violent reaction begins, igniting the gases released. For example, a large number of lithium mobile phone batteries shipped to Japan in 1991 were recalled after several fire incidents.

Because of lithium's inherent instability, researchers have turned their attention to non-metallic lithium batteries based on lithium ions. Having lost a little in energy density and taking some precautions when charging and discharging, they received safer so-called Li-ion batteries.

The energy density of Li-ion batteries is usually twice that of standard NiCd, and in the future, thanks to the use of new active materials, it is expected to increase it even further and achieve three times superiority over NiCd. In addition to the large capacity, Li-ion batteries behave similarly to NiCds when discharged (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 it is impossible to distinguish them by appearance. Therefore, we will note only those advantages and disadvantages that are characteristic of all types of these devices, and consider the reasons that led to the birth of lithium-polymer batteries.

Main advantages.

High energy density and, as a result, large capacity with the same dimensions compared to nickel-based batteries.
Low self-discharge.
High voltage of a single cell (3.6 V versus 1.2 V for NiCd and NiMH), which simplifies the design - often the battery consists of only one cell. Many manufacturers today use just such a single-cell battery in cell phones (remember Nokia). However, to provide the same power, a higher current must be supplied. And this requires ensuring low internal resistance of the element.
Low maintenance (operating) costs result from the absence of memory effect, requiring periodic discharge cycles to restore capacity.

Flaws.

Li-ion battery manufacturing technology is constantly improving. It is updated approximately every six months, and it is difficult to understand how new batteries “behave” after long-term storage.

In a word, a Li-ion battery would be good for everyone if it were not for the problems with ensuring the safety of its operation and the 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 is reflected in the name and lies in the type of electrolyte used. Initially, in the 70s, a dry solid polymer electrolyte was used, similar to plastic film and not conducting electricity, but allowing the exchange of ions (electrically charged atoms or groups of atoms). The polymer electrolyte effectively replaces the traditional porous separator impregnated with electrolyte.

This design simplifies the production process, is safer, and allows the production of thin, free-form batteries. In addition, the absence of liquid or gel electrolyte eliminates the possibility of ignition. The thickness of the element is about one millimeter, so equipment developers are free to choose the shape, shape and size, even including its implementation in fragments of clothing.

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 communications and power supply to the hard drives of laptop computers. At the same time, when heated to 60 °C or more, the electrical conductivity of Li-polymer increases to an acceptable level, but this is not suitable for mass use.

Researchers are continuing to develop Li-polymer batteries with a dry solid electrolyte that operates at room temperature. Such batteries are expected to become commercially available by 2005. They will be stable, allow 1000 full charge-discharge cycles and have a higher energy density than today's Li-ion batteries

Meanwhile, some types of Li-polymer batteries are now used as backup power supplies in hot climates. For example, some manufacturers specifically install heating elements that maintain a favorable temperature for the battery.

You may ask: how can this be? Li-polymer batteries are widely sold on the market, manufacturers equip phones and computers with them, but here we are saying that they are not yet ready for commercial use. Everything is very simple. In this case, we are talking about batteries not with dry solid electrolyte. In order to increase the electrical conductivity of small Li-polymer batteries, a certain amount of gel-like electrolyte is added to them. And most Li-polymer batteries used for cell phones today are actually hybrids because they contain a gel-like electrolyte. It would be more correct to call them lithium-ion polymer. But most manufacturers simply label them as Li-polymer for advertising purposes. Let us dwell in more detail on this type of lithium-polymer batteries, since at the moment they are of the greatest interest.

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

Technical difficulties and delays in ramping up production have delayed the introduction of Li-ion polymer batteries. This is caused, according to some experts, by the desire of investors who have invested a lot of money in the development and mass production of Li-ion batteries to get their investments back. Therefore, they are in no hurry to switch to new technologies, although with mass production of Li-ion polymer batteries will be cheaper than lithium-ion ones.

And now about the features of operating Li-ion and Li-polymer batteries.

Their main characteristics are very similar. The charging of Li-ion batteries is described in sufficient detail in the article. In addition, I will only give a graph (Fig. 1) from, illustrating the stages of charge, and small explanations to it.

The charging time for all Li-ion batteries with an initial charging current of 1C (numerically equal to the nominal value of the battery capacity) averages 3 hours. Full charge is achieved when the battery voltage is equal to the upper threshold and when the charging current is reduced to a level approximately equal to 3% of the initial value. The battery remains cold during charging. As can be seen from the graph, the charging process consists of two stages. In the first (a little over an hour), the voltage increases at an almost constant initial charge current of 1C until the upper voltage threshold is first reached. At this point, the battery is charged to approximately 70% of its capacity. At the beginning of the second stage, the voltage remains almost constant and the current decreases until it reaches the above 3%. After this, the charge stops completely.

If you need to keep the battery charged all the time, it is recommended to recharge after 500 hours, or 20 days. Usually it is carried out when the voltage at the battery terminals decreases to 4.05 V and stops when it reaches 4.2 V

A few words about the temperature range during charging. Most types of Li-ion batteries can be charged with a current of 1C at temperatures from 5 to 45 °C. At temperatures from 0 to 5 °C, it is recommended to charge with a current of 0.1 C. Charging at sub-zero temperatures is prohibited. The optimal temperature for charging is 15 to 25 °C.

The charging processes in Li-polymer batteries are almost identical to those described above, so the consumer has absolutely no need to know which of the two types of batteries he has in his hands. And all those chargers that he used for Li-ion batteries are suitable for Li-polymer.

And now about the discharge conditions. Typically, Li-ion batteries discharge to a value of 3.0 V per cell, although for some varieties the lower threshold is 2.5 V. Manufacturers of battery-powered equipment typically design devices with a shutdown threshold of 3.0 V (for all occasions). What does this mean? The voltage on the battery gradually decreases when the phone is turned on, and as soon as it reaches 3.0 V, the device will warn you and turn off. However, this does not mean that it has stopped consuming energy from the battery. Energy, albeit small, is required to detect when the phone's power key is pressed and some other functions. In addition, energy is consumed by its own internal control and protection circuit, and self-discharge, although small, is still typical even for lithium-based batteries. As a result, if lithium batteries are left for a long period of time without recharging, the voltage on them will drop below 2.5 V, which is very bad. In this case, the internal control and protection circuit may be disabled, and not all chargers will be able to charge such batteries. In addition, deep discharge negatively affects the internal structure of the battery itself. A completely discharged battery must be charged at the first stage with a current of only 0.1C. In short, batteries like to be in a charged state rather than in a discharged state.

A few words about temperature conditions during discharge (read during operation).

In general, Li-ion batteries perform best at room temperature. Operating in warmer conditions will seriously reduce their lifespan. Although, for example, a lead-acid battery has the highest capacity at temperatures above 30 °C, long-term operation in such conditions shortens the life of the battery. Likewise, Li-ion performs better at high temperatures, which initially counteracts the increase in battery internal resistance that results from aging. But the increased energy output is short-lived, since increasing temperature, in turn, promotes accelerated aging, accompanied by a further increase in internal resistance.

The only exceptions at the moment are lithium-polymer batteries with dry solid polymer electrolyte. They require a vital temperature of 60 °C to 100 °C. And such batteries have found their niche in the market for backup sources in hot climates. They are placed in a thermally insulated housing with built-in heating elements powered from an external network. Li-ion polymer batteries as a backup are considered to be superior in capacity and durability to VRLA batteries, especially in field conditions where temperature control is not possible. But their high price remains a limiting factor.

At low temperatures, the efficiency of batteries of all electrochemical systems drops sharply. While NiMH, SLA and Li-ion batteries stop functioning at -20°C, NiCd batteries continue to function down to -40°C. Let me just note that again we are talking only about batteries of wide use.

It is important to remember that although a battery can operate in low temperatures, this does not mean that it can also be charged in these conditions. The charge responsiveness of most batteries at very low temperatures is extremely limited, and the charge current in these cases should be reduced to 0.1C.

In conclusion, I would like to note that you can ask questions and discuss problems related to Li-ion, Li-polymer, as well as other types of batteries, on the forum in the accessories subforum.

When writing this article, materials were used [—Batteries for mobile devices and laptop computers. Battery analyzers.

Features of lithium polymer batteries and rules of their operation

A lithium polymer battery is a modified version of lithium ion batteries. The main difference is 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. Although lithium batteries are not capable of delivering high discharge currents, some special types of polymer batteries can deliver currents that significantly exceed their capacity. Since lithium polymer batteries are rapidly spreading on the market, you need to have an understanding of their design, operating rules and safety precautions when handling them. This will be discussed in our material today.

The advantage of replacing a liquid organic electrolyte with a polymer one is to increase the safety of battery operation. This is very important for lithium batteries. It was the safe use for commercial purposes that held back their development from the very beginning. In addition, the polymer electrolyte gives much more freedom when choosing the shape of the battery.

The design of Li─Pol batteries was based on the process of transition of a number of polymers into a semiconductor state when electrolyte ions are introduced into them. In this case, the conductivity increases several times.

Researchers were mainly busy selecting a polymer electrolyte for batteries with metallic lithium and Li─Ion models. In theory, the energy density of polymer batteries can be increased several times compared to lithium-ion ones. Today, several groups of Li─Pol batteries can be distinguished, differing in the composition of the electrolyte:
With gel-like homogeneous electrolyte. It is obtained as a result of the introduction of lithium salts into the polymer structure;
With dry polymer electrolyte. This type is made on the basis of polyethylene oxide with different lithium salts;

If we compare polymer and liquid electrolytes, it is worth noting the lower ionic conductivity of the former. It decreases significantly at subzero temperatures. So, one problem was to select a composition for an electrolyte with high conductivity. 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.

The containers of some models, which contain the jar itself, are made of metallized polymer. Due to crystallization of the polymer electrolyte, the parameters of these batteries are significantly reduced at low temperatures.

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

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

Now there are many experiments that have been carried out that prove the higher level of safety of polymer batteries compared to ionic ones. This applies to overcharging, accelerated discharge, vibration, compression, short circuit, puncture 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.
So, this type of battery has the best development prospects. Below are the results of tests for the safe operation of Li─Pol batteries.	Type of test	Battery with gel polymer electrolyte
Battery with liquid electrolyte	Puncture with a needle	There were no changes
Explosion, smoke, electrolyte leakage, temperature increase up to 250°C	Puncture with a needle	Heating up to 200°C
Explosion, electrolyte leakage	Puncture with a needle	Short circuit current
Electrolyte leakage, temperature increase by 100°C	Recharge (600%)	Bloating

There are examples of lithium polymer batteries that are 1 millimeter thick. Such models allow mobile device designers to create very compact equipment. 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. The batteries used in mobile phones use this type of electrolyte. They combine the features of polymer and ion batteries.

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

In terms of their energy intensity, lithium polymer batteries have a specific energy intensity that is 4-5 times higher and 3-4 times higher. Both of these types belong to . The comparison is made with them, since lithium batteries have largely replaced alkaline batteries in mobile electronics.

Li-Pol batteries have a resource 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.

Production technology and design are constantly being improved and in the future, perhaps, the characteristics will improve. It is also worth noting that in 1-2 years a polymer battery loses approximately 20% of its capacity. In this parameter they correspond to ion batteries.

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

KKM2500 denotes a regular model with a capacity of 2500 mAh, and the marking KKM2000HD stands for a fast-discharge battery with a capacity of 2000 mAh. Fast-discharge models are not used in household 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 arise from the tasks that were posed during their development. This increases the operating time of the device and reduces its weight. Standard Li─Pol models work in various electronics with low current consumption. These are laptops, smartphones, e-readers, tablets.

Models that provide quick discharge are also called “power”. They are used in devices where high current consumption is required. The most well-known area of application for “power” batteries is radio-controlled models.

This market is the most attractive for manufacturers of polymer batteries. In the field of operation 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 are approximately the same as nickel-metal hydride.

Operation of lithium polymer batteries

Safety

Lithium batteries in general, and polymer batteries 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);
Short circuits must not be allowed;
It is unacceptable to discharge with currents that lead to heating of the battery by more than 60 degrees Celsius;
The battery cannot be depressurized;
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 result in a fire at worst, and significant loss of capacity at best.

It is also worth noting that you need to observe the temperature regime and prevent overheating of the polymer battery. This is the weak point of all lithium 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 battery voltage, then it should be monitored especially closely at the end of the discharge.

Another reason for lithium batteries to fail is depressurization. Under no circumstances should air penetrate inside the polymer battery can. Initially, the case is sealed and should not be subjected to impacts or dropped. If you are soldering leads, then you need to do this extremely carefully.

Before storing a polymer battery, it is recommended to charge it halfway. The battery should be stored in a cool place away from direct sunlight.

Like all batteries, lithium polymer batteries have self-discharge, but it is less than that of lead or alkaline batteries.

Almost all modern electronic gadgets are equipped with lithium polymer batteries. They are widely used on flying radio-controlled models, quadcopters, helicopters and airplanes. Lithium-polymer batteries have many advantages, including high energy density, low self-discharge and the absence of the so-called “memory effect”.

As a result, for models with Li Pol power units, there is practically no worthy alternative to the battery. It is expected that they will be used more and more widely, especially in areas such as unmanned aerial vehicles, electric vehicles, etc.

Despite all the advantages, LiPol batteries have a reputation as capricious, dangerous and short-lived power sources. In fact, these shortcomings are somewhat exaggerated. If used correctly, problems will be kept to a minimum.

Charging rules

To ensure that there are no problems in operating the power source, it is necessary to properly charge LiPo batteries. Otherwise, there is a high risk of damage and even spontaneous combustion. Let's look at how to properly charge a lithium polymer battery to avoid possible problems:

Charging of Li Pol batteries takes place in two phases (CC-CV method). At the first stage, the voltage on all battery banks increases. By the end of the phase it reaches 4.2 Volts. In fact, at this point the charge of Li Pol batteries reaches 95%. Then the second phase begins. To prevent overcharging, which is detrimental to a lithium-polymer battery, the current is reduced. If the voltage exceeds 4.25 Volts, the risk of spontaneous combustion increases.
It is not recommended to allow the power supply to completely discharge; before recharging, there should be about 10-20% left in it, otherwise it will quickly fail.
It is important to ensure that the voltage does not drop below 3 Volts on each bank. With such a decrease in voltage, there is a high risk that the battery may swell. In this case, a swollen LiPo battery will lose more than 50% of its capacity. If a LiPo battery is swollen, all you have to do is throw it away - the loss of capacity is irreversible.

The fact that lithium polymer power supplies swell is one of the serious problems in their operation. All banks should be charged and discharged evenly. In this case, the charger for lithium polymer batteries monitors only the total voltage, but with a large scatter of indicators, the likelihood that the LiPo battery is swollen increases significantly. This also leads to overcharging of individual cans, increasing the risk of spontaneous combustion.

To solve this problem, charging Li Pol batteries must be done using a balancer that is capable of monitoring the voltage on each bank, or a charger with a built-in balancer. Do not charge the power supply of a timer charger. If the current is insufficient, the charger will turn off without fully charging it. The charge current should not exceed 1C and be less than 0.5C. You also need to remember that the greater the capacity of the LiPo battery, the longer it will take to charge.

Exploitation

In order to extend the service life of Li Pol devices, or at least not to shorten it, proper use of batteries is also important. When we charge the power source, we must not allow it to heat above 60 degrees. If heating does occur, the battery must be allowed to cool before using. You should also not charge an overheated drive.

A completely discharged battery should not be left for storage. Be sure to charge it. The most optimal indicators are 60%. In general, if these simple rules are followed, there are no problems using lithium-polymer batteries.