Lithium polymer battery. Lithium-polymer battery: difference from ion, service life, device. Li-pol or Li-ion: which is better

The most common types of batteries are lithium polymer and lithium ion. What are their features?

Facts about lithium polymer batteries

IN lithium polymer batteries a solid polymer electrolyte is used. In the very first samples of batteries of this type, created in the 70s, it was present mainly in a dry modification. This electrolyte did not actually conduct electric current, but it could exchange ions formed by lithium compounds. Modern devices - laptops, mobile phones, gadgets - use batteries that also contain a certain amount of electrolyte in the form of a gel.

Lithium polymer batteries are capable of delivering high levels of electrical energy density for their size and weight. They are characterized by a fairly low self-discharge, do not have the so-called memory effect - when a charged battery during use is sometimes discharged only to a level that corresponds to the moment the battery is charged (that is, not necessarily to zero), and can also operate over a wide range of temperatures.

However, lithium polymer batteries are not always safe - especially if they overheat or take too long to charge. Batteries of the type under consideration have about 800-900 operating cycles, at which the level of capacity loss does not exceed 20%. The battery loses the same 20% of performance after 2 years of operation, even if it is not used but is in storage.

Lithium-polymer batteries are often very small in size - it is theoretically possible to produce batteries with a thickness of about a millimeter. The use of a metal body in their design is optional.

Facts about lithium-ion batteries

Design lithium ion battery consists of electrodes and separators, usually impregnated with liquid electrolyte. The first are represented by aluminum cathodes and copper anodes. The electric charge in batteries of this type is transferred by a positively charged lithium ion, which has the ability to integrate into the crystal lattices of other substances and thus form new compounds. The cathodes in modern lithium-ion batteries are usually represented by compounds of lithium with cobalt, nickel, manganese, and iron phosphate.

Batteries of this type are characterized, like lithium-polymer products, by low self-discharge, but slightly exceed them in energy intensity. Lithium-ion batteries do not need to be charged and discharged periodically to maintain functionality.

Older models of lithium-ion batteries are considered unsafe to use, but those that include elements made from a lithium iron phosphate compound are considered quite reliable. Like lithium polymer devices, these types of batteries lose capacity over time - even when not in use.

Comparison

The main difference between a lithium-polymer battery and a lithium-ion battery is the use of a predominantly dry electrolyte (with a small percentage of gel) in the structure of the former, while the latter, as a rule, uses a liquid electrolyte. This predetermines the possibility, first of all, not to use a metal shell in the design of lithium-polymer batteries and to produce a battery of small size and thickness. In lithium-ion batteries, in turn, it is necessary - otherwise the electrolyte will leak out. The importance of using a metal shell can make it difficult for manufacturers to reduce the size of their batteries.

Having determined what the difference is between a lithium-polymer and a lithium-ion battery, we will reflect the conclusions in a small table.

Table

The lithium polymer battery is an improved version of the traditional lithium-ion battery. Its main difference is the use of a special polymer material, in which gel-like lithium-conducting inclusions are used as filling. This type of battery is used in many models of mobile devices, phones, digital devices, radio-controlled cars, and so on.

A traditional lithium polymer battery for household use cannot supply too much current. However, today there are special power varieties of such devices that can deliver a current that is many times higher than its capacity in ampere-hours.

Lithium polymer battery design

The difference between lithium polymer and lithium ion energy storage is the type of electrolyte used. Polymer batteries use a special polymer with a lithium-containing solution, while ion batteries use a regular gel electrolyte. The power systems of most modern models use a lithium polymer battery. This is due to the fact that it provides more powerful discharge currents. However, there is no too strict division between these types of batteries, since they differ only in the nature of the electrolyte. This applies to charging and discharging features, operating rules and safety precautions.

Main Features

A modern lithium-polymer battery with the same mass is significantly more energy-intensive than nickel-cadmium (NiCd) and nickel-metal hydride (NiMH) batteries. They have a number of operating cycles of approximately 500-600. Let us recall that for NiCd it is 1000 cycles, and for NiMH it is about 500. Like lithium-ion, polymer carriers also age over time. Therefore, after 2 years, such a battery will lose up to 20% of its capacity.

Types of power lithium polymer batteries

Today there are two main types of such batteries - standard and fast-discharge. They differ in the level of maximum discharge current. This indicator is indicated either in units of battery capacity or in amperes. In most cases, the maximum level of discharge current does not exceed 3C. However, some models can produce a current of 5C. In fast-discharge devices, a discharge current of up to 8-10C is allowed. However, fast-discharge models are not used for household appliances.

Features of application

The use of a lithium-polymer battery can significantly increase the operating time of the electric motor while reducing the weight of the battery itself. Therefore, if you replace a regular NiMH 650 mAh battery with two regular lithium-polymer batteries, you can get 3 times more energy-capacious energy. Moreover, such a battery will be more than 10 g lighter. If you take fast-discharging batteries, then you can achieve even higher performance. Such a system will be an excellent option not only for small models of airplanes or helicopters, but also for impressive radio-controlled devices.

Lithium polymer batteries, unlike lithium-ion batteries, have performed well in small helicopters such as the Hummingbird and Piccolo. Similar models with conventional commutator motors can fly on two polymer batteries for half an hour. When using a brushless motor, this time increases to 50 minutes. This type of battery is considered an ideal option for light-weight indoor aircraft. Their efficiency in this case is determined by their much lighter weight compared to NiCd batteries.

The only area in which a lithium-polymer battery is inferior to NiCd is its use in devices with ultra-high discharge currents of up to 50 C. However, it is quite possible that in a few years more powerful batteries of this type will appear. At the same time, prices for lithium-polymer, lithium-ion and NiCd batteries are approximately the same for the same mass of devices.

Features of operation

The operating rules for lithium-polymer and lithium-ion batteries are largely similar. When using a polymer battery, you must avoid certain dangerous situations that can cause irreparable harm to it:

• charging the device with a voltage of 4.2 volts per jar;
• discharge with currents with a load capacity exceeding the proper one;
• discharge with a voltage below 3 volts per cell;
• battery depressurization;
• heating the device above 60 degrees;
• long-term storage in a completely discharged state.

Lithium polymer and lithium ion batteries have a fire hazard when overheated and overdischarged. To combat this phenomenon, all modern batteries are equipped with a built-in electronic system that prevents overdischarge or overheating. This is why a lithium polymer battery requires special charging algorithms.

Charger

The process of charging lithium-polymer batteries is practically no different from charging lithium-ion batteries. Charging of most lithium-polymer batteries with a starting charging current of 1C is achieved in approximately 3 hours. To achieve a full charge, it is necessary to have the battery voltage corresponding to the upper threshold. In addition, a necessary condition is to reduce the charge current to 3% of the nominal value. Moreover, during such charging, such a battery always remains cold. If you want to keep the battery constantly charged, then it is advisable to recharge approximately once every 500 hours, which corresponds to 20 days. As a rule, charging is usually carried out when the voltage at the battery terminals drops to 4.05V. Charging is stopped after the voltage at the terminals reaches 4.2V.

Charge temperature

Most lithium-polymer batteries can be charged at a temperature of 5-45 degrees at a current of 1C. If the temperature is in the range from 0 to 5 degrees, then it is recommended to switch to a current of 0.1C. Charging at sub-zero temperatures is completely prohibited in this case. Traditionally, it is believed that the most favorable conditions for charging are 15-25 degrees. Since all charging processes in lithium-polymer and lithium-ion batteries are almost identical, the same chargers can be used for them.

Discharge conditions

Traditionally, this type of battery discharges at a voltage of 3.0V per battery. However, some types of devices must be discharged at a minimum threshold of 2.5V. Manufacturers of mobile devices provide a switch-off threshold of 3.0V, which will be suitable for any type of battery. That is, as the battery discharges while the mobile device is turned on, the voltage gradually drops and, when it reaches 3.0V, the device automatically warns you and turns off. However, the device still continues to consume some energy from the battery. This is required to detect when the power button is pressed or for other similar functions. Also, the energy here can be used for its own protection and control circuit. Moreover, a low level of self-discharge still remains characteristic of lithium-polymer carriers. Therefore, if you leave such batteries for a long time, the voltage in them may drop below 2.5V, which is very harmful. All internal protection and control systems may be disabled. As a result, such batteries can no longer be charged with conventional chargers. In addition, complete discharge is very harmful to the internal structure of the battery. Therefore, a completely discharged battery must be charged at the first stage with a minimum current of 0.1C.

Temperature during discharge

The lithium polymer battery performs best at room temperature. If you use your device in hotter environments, battery life may be significantly reduced. As for the lithium-ion battery, this battery works best at high temperatures. Initially, it prevents the internal resistance of the battery from increasing, which is considered a result of aging. However, subsequently the energy output is reduced and an increase in temperature accelerates the aging process due to an increase in internal resistance.

The lithium polymer battery has slightly different operating conditions, since it has a dry and solid electrolyte. The ideal temperature for its operation is 60-100 degrees. Therefore, such an energy carrier has become an ideal option for backup power sources in regions with hot climates. They are specially placed in a heat-insulating housing with built-in heating elements powered from an external network.

• The lithium polymer battery has superior capacity and durability to the lithium-ion battery.
• Ease of use in field conditions when there is no way to control the temperature.
• High energy density per unit weight and volume.
• Low self-discharge.
• Thin elements no more than 1 mm.
• Flexibility of form.
• No memory effect.
• Wide operating temperature range from −20 to +40 °C.
• Insignificant voltage drop during discharge.

Disadvantages of lithium polymer batteries:

• Low efficiency at temperatures of -20 degrees and below.
• High price.

What is the difference between a lithium polymer battery and an ion battery?

The vast majority of residents of developed countries have mobile phones, tablets, and laptops. When you purchase a gadget in a store, most likely, you don’t even think about the type of battery it contains. And this is not surprising. Technologies are developing rapidly, including in the field of batteries. Not so long ago, Ni─Cd batteries were used in mobile electronics, which were later replaced by Ni─MH. Then lithium-ion appeared, which quickly conquered the market for portable gadgets. And now they are being squeezed out by lithium polymer batteries. At some point, the user begins to think about what kind of battery he has. What are its advantages and disadvantages? In this article we will try to understand what is the difference between a lithium polymer battery and a lithium ion battery.

Work on creating batteries using lithium has been going on for quite some time. But the first workable copies for household appliances appeared only in the 70s of the last century. But then these were imperfect models with electrodes made of metal lithium. And the operation of such batteries is problematic in terms of safety. There were many unresolved problems with the process of charging and discharging such batteries.

This leads to the fact that the stability of operation is disrupted and there is a risk of ignition due to the uncontrolled reaction in the battery. The battery cell heats up quickly and, when the temperature rises to the point where lithium melts, a violent reaction occurs with ignition. This was associated with recalls of the first lithium batteries in consumer electronics in the early 90s.

As a result, scientists began to develop batteries based on Li ions. Due to the fact that we had to abandon the use of lithium metal, the energy density decreased somewhat. But on the other hand, safety problems during battery operation were resolved. These new batteries are called lithium-ion batteries.

The energy density of lithium-ion batteries is 2-3 times (depending on the materials used) higher than that of . When discharged, Li─Ion batteries show characteristics similar to Ni─Cd. The only thing in which they are inferior to them is operation at ultra-high discharge currents (more than 10C). To date, many different modifications of lithium-ion batteries have already been released.

They differ in the material used as the cathode, form factor and some other parameters. They are uniquely characterized by a design that includes electrodes immersed in a liquid electrolyte containing lithium ions. This battery cell is placed in a sealed metal shell (steel, aluminum). To control the charging and discharging processes in lithium-ion batteries, there is a printed circuit board called a controller.

To make the picture of Li─Ion batteries complete, let’s consider their advantages and disadvantages.

Advantages of Li─Ion

• Slight self-discharge;
• High energy density and capacity compared to alkaline ones;
• One battery cell has a voltage of about 3.7 volts. For cadmium and metal hydride, this value is 1.2 volts. This allows the design to be significantly simplified. Phones, for example, use batteries that contain only one cell;
• There is no memory effect, which means battery maintenance is simplified.

Disadvantages of Li─Ion

• A controller is required. This is a printed circuit board that controls the voltage of the battery cell or cells, if there are several of them. The board also controls the maximum discharge current and, in some cases, the temperature of the can. Without a controller, safe operation of a lithium-ion battery is impossible;
• Degradation of the Li─Ion system occurs even during storage. That is, after a year, the battery capacity decreases noticeably, even if it is not used. Batteries of other types (alkaline, lead-acid) also gradually degrade during storage, but this is less pronounced for them;
• The price of lithium ion is higher than cadmium or .

The capabilities of lithium-ion technology have not been fully developed. Therefore, new batteries are constantly appearing, where certain problems of this type of battery are solved. For more information about what it is, read the article at the link provided.

Li-Pol battery

Due to problems with ensuring safety when charging and discharging Li─Ion batteries, further development of modifications of these batteries began. As a result, lithium polymer batteries were developed. Their difference from ionic ones is in the electrolyte used. It is worth saying that the first developments in this direction were carried out simultaneously with Li─Ion technology. Back in the last century, a dry electrolyte made from a solid polymer was used for the first time. By appearance it looks like a film of plastic. This polymer does not conduct current, but does not interfere with ion exchange, which involves the movement of charged atoms or groups of atoms. In addition to containing electrolyte, the polymer also acts as a porous separator between the electrodes.

The new design has improved safety and simplified battery production. And even more important is that lithium polymer batteries can be produced in almost any shape and very small thickness (up to 1 millimeter). This makes it possible to make various devices powered by Li─Pol batteries thin, compact and elegant. Some lithium polymer batteries can even be sewn into clothing.

Naturally, there are also disadvantages. In particular, Li─Pol batteries with dry electrolyte have low electrical conductivity at room temperature. This is because at this temperature their internal resistance is high, which prevents them from delivering the discharge current needed to operate portable electronics.

If you heat a lithium polymer battery to 60 degrees Celsius, the conductivity increases. Obviously, this is not suitable for use on phones or tablets. However, dry polymer batteries have found their niche in the market. They are used as backup power sources in conditions of elevated temperatures. There are options when heating elements are installed to provide the temperature necessary for normal battery operation.

Another important point is worth clarifying here. Surely everyone has seen that batteries labeled Li─Pol have been used in smartphones, tablets and laptops for a long time. These are lithium polymer hybrid batteries, so to speak. They are a cross between Li-Ion and dry polymer batteries. Manufacturers producing lithium polymer batteries use a gel-like substance with lithium ions as an electrolyte.

So, almost all lithium polymer batteries in modern mobile gadgets use a gel-like electrolyte. By design, they are a hybrid of ion and polymer batteries. What is the difference between ionic and polymer batteries with gel electrolyte? Their basic electrochemical parameters are approximately the same. The difference between such hybrid batteries is that they use a solid electrolyte instead of a porous separator. As mentioned above, it also acts as a porous separator. And the electrolyte in a gel state is used to increase the electrical conductivity of ions.

Lithium polymer batteries are becoming more widespread on the market and they are the future. At least in the segment of household appliances and consumer electronics. But so far their implementation is not very active. Some market experts explain this by saying that too much money has been invested in the development of Li-Ion batteries. And investors simply want to “recoup” their invested money. read the link.

Lithium polymer batteries (Li-po) differ from lithium-ion batteries in that they do not have separators and liquid electrolyte. Lithium polymers use a homogeneous electrolyte with lithium salts in the form of a gel, or a composite polymer with lithium salts in a dry state (often the base is polyethylene oxide). Lithium polymer batteries can also consist of a non-aqueous solution of lithium salts. Read more about the differences.

Advantages of lithium polymer batteries.

The main advantages of lithium polymers over batteries are that they have a fairly low self-discharge and have 4 and a half times more energy capacity than Ni-CD batteries of the same mass.

Lithium polymers usually have a service life of 300 - 600 charge/discharge cycles, but are sometimes found with 1000 recharge cycles.

Very common lithium polymer batteries are shaped like a button and only 1 mm thick. (tablet). Also, these batteries have the smallest weight relative to lithium-ion, nickel-cadmium batteries and non-rechargeable batteries, provided they have the same capacity.

Application

Small-sized button-shaped lithium-polymer batteries with a thickness of only 1 mm are widespread. In addition, these batteries have the least weight compared to the batteries and non-rechargeable batteries discussed above with the same energy capacity. This factor determined further niches for the use of lithium-polymer batteries:

• mobile phones
• DVRs and navigators
• radio controlled models
• various gadgets and devices.

Disadvantages of lithium polymer batteries:

■ Energy density is lower than that of ;

■ The high internal resistance of lithium polymers cannot provide high discharge currents. Therefore, lithium polymers cannot be used in screwdrivers and other highly powerful equipment.

■ Rapid degradation, so lithium polymer batteries lose most of their capacity after a couple of years, even during storage.

These batteries are very sensitive to the temperature conditions under which they operate. So Lithium polymers cannot work normally at negative ambient temperatures. Surely you have often noticed how quickly your mobile phone discharges in the cold. Lithium polymers can explode at temperatures above 70°C and cause a fire.

Lithium polymer batteries can deteriorate over time, even if not used. Therefore, you should not buy lithium polymers in reserve. Lithium polymers, like lithium-ion batteries, do not possess, but it is still recommended to adhere to some rules regarding these batteries:

• Fully charge the first time you use it
• Go through several full recharge cycles using a voltage stabilizer.
• It is recommended to store lithium-polymer batteries in a cool place, but not at sub-zero temperatures.
• Avoid full discharge
• Frequent short-term recharging should be avoided.
• The most optimal temperatures for the battery are from +10°C to plus 25°C.

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, all of us do not 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 are characterized by 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, high capacity with the same dimensions compared to nickel-based batteries.
• Low self-discharge.
• High voltage per 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. It's 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 the ones that are of greatest interest.

So, what is the difference between Li-ion and Li-polymer batteries 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 at all 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 rising temperatures in turn promote 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 susceptibility 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.