Li poly battery. Features of lithium polymer batteries and rules of their operation


Difference betweenlithium-ion Andlithium polymer battery types significant, if the polymer material acts as an electrolyte. Here you will learn the features of each type of battery and be able to make the right choice..



Looking ahead, we will hasten to reassure you - when buying a smartphone, tablet or laptopyou will find the same type of battery inside. And no matter what is stated there -Li-Ion or Li-Po , this will have the least impact on the operating time and characteristics of the device as a whole..


For example, the processor model or firmware version for the overall autonomy of a mobile gadget (keep in mind that we are not talking about tools) is much more important than the type of battery. Choose the most capacious battery and read reviews from real users.


Differences between lithium-ion and lithium-polymer batteries

In all known smartphones, tablets, laptops, smart watches and other portable gadgets, the most suitable battery is calculated during the design phase of the engineering design. In recent years, manufacturers have been particularly diligent in their efforts to introduce the latest energy-saving technologies.


Sometimes developers manage to achieve longest battery life cycle. But for the sake of the conceptual features of the future product (for example, a thin body or a huge camera without increasing dimensions), even the coolest battery saving systems can be “strangled”.


Therefore, we buyers are left to compromise and choose characteristics that are suitable for specific purposes. If you go hiking or travel a lot, choose long battery life over size and graceful appearance. Do you like to put your phone on the table in an expensive restaurant? Then treat it as an accessory - let it work less, but once again emphasize the status of the owner.



Battery type (lithium-ion and lithium-polymer) does not affect the evaluation of the gadget in any way - this is part of the engineering calculation for the chosen concept, where the choice is between, relatively speaking, a “simpler and cheaper” design or a “more complex but more expensive” design. If you want to independently determine the most durable device among competitors, then it is better to turn to professional reviews or at least reviews from real users. This information will tell you much more about the quality of the battery than whether it is a lithium-ion or lithium-polymer technology.


It doesn't matter what type is hosted on the mobile device, just don't worry about it!


Here's a fact from the experts at "Battery University" - they are practically not found in modern gadgets polymer based lithium batteries, they offer us lithium ion polymer batteries, in which it is used laminated shell instead of rigid housings like conventional lithium-ion batteries.


Most often, a lithium-polymer battery is called a lithium-ion battery in an elastic polymer shell with compact dimensions.


Have you ever wondered why manufacturers Li-Ion Polymer on some batteries (for example, on iPhone and other smartphones)? Now you know what's really going on here - due to the abbreviated names, the difference between lithium-ion and lithium-polymer batteries when it comes to portable electronics is actually minimal. Let's take a closer look at this.



Pros of lithium-ion (Li-Ion) battery

+ high density
+ no memory effect
+ low cost

Battery production technologies do not stand still and gradually Ni-Cd (nickel-cadmium) and Ni-MH (nickel-metal hydride) batteries are being replaced on the market by batteries based on lithium technology. Lithium polymer (Li-Po) and lithium-ion (Li-ion) batteries are increasingly used as a power source in various electronic devices

Lithium- silver-white, soft and ductile metal, harder than sodium, but softer than lead. Lithium is the lightest metal in the world! Its density is 0.543 g/cm3. It can be processed by pressing and rolling. Lithium deposits are found in Russia, Argentina, Mexico, Afghanistan, Chile, USA, Canada, Brazil, Spain, Sweden, China, Australia, Zimbabwe and Congo

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 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. By playing around a little with energy density and taking some precautions when charging and discharging, they came up with safer so-called lithium-ion (Li-ion) batteries.

The energy density of Li-ion batteries is usually several times higher than that of standard NiCd and NiMH batteries. Thanks to the use of new active materials, this superiority is increasing every year. In addition to its large capacity, Li-ion batteries behave similarly to nickel batteries when discharged (their discharge characteristics are similar 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 (Li-Po) batteries.

The Li-ion battery was good for everyone, but problems with ensuring the safety of its operation and high cost led scientists to create a lithium-polymer battery (Li-pol or Li-po).

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, so they have a flexible plastic shell, are lighter in weight, have higher current output and can be used as power batteries for devices with powerful electric motors.

This design simplifies the production process, is characterized by higher safety and allows the production of thin batteries of any shape. The minimum 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 clothing fragments.

Main advantages

  • Lithium-ion and lithium-polymer batteries with the same weight are superior in energy intensity to nickel (NiCd and Ni-MH) batteries
  • Low self-discharge
  • High voltage per cell (3.6-3.7V versus 1.2V-1.4 for NiCd and NiMH), which simplifies the design - often the battery consists of only one cell. Many manufacturers use just such a single-cell battery in various compact electronic devices (cell phones, communicators, navigators, etc.)
  • Element thickness from 1 mm
  • Possibility of obtaining very flexible forms

Flaws

  • The battery is subject to aging, even if it is not used and just sitting on a shelf. For obvious reasons, manufacturers are silent about this problem. The clock starts ticking from the moment the batteries are produced at the factory, and the decrease in capacity is the result of an increase in internal resistance, which in turn is generated by oxidation of the electrolyte. Eventually, the internal resistance will reach a level where the battery can no longer supply the stored energy, even though there is enough energy in the battery. After two or three years, it often becomes unusable.
  • Higher cost compared to NiCd and Ni-MH batteries
  • When using lithium polymer batteries, there is always a risk of ignition, which can occur due to shorted contacts, improper charging, or mechanical damage to the battery. Since the combustion temperature of lithium is very high (several thousand degrees), it can ignite nearby objects and cause a fire.

Main characteristics of Li-Po batteries

As mentioned above, lithium-polymer batteries with the same weight are several times higher in energy intensity than NiCd and Ni-MH batteries. The service life of modern Li-Po batteries, as a rule, does not exceed 400-500 charge-discharge cycles. For comparison, the service life of modern Ni-MH batteries with low self-discharge is 1000-1500 cycles.

Technologies for the production of lithium batteries do not stand still and the above figures may lose relevance at any time, because Battery manufacturers are increasing their characteristics every month through the introduction of new technological processes for their production.

Of the variety of lithium-polymer batteries available for sale, two main groups can be distinguished: fast-discharge(Hi Discharge) and ordinary. They differ from each other in the maximum discharge current - it is indicated either in amperes or in units of battery capacity, designated by the letter “C”.

Application areas of Li-Po batteries

The use of Li-Po batteries allows you to solve two important problems - increase the operating time of devices and reduce battery weight

Regular Li-Po batteries are used as power sources in electronic devices with relatively low current consumption (mobile phones, communicators, laptops, etc.).

Fast-discharge Lithium polymer batteries are often called " by force"- such batteries are used to power devices with high current consumption. A striking example of the use of “power” Li-Po batteries are radio-controlled models with electric motors and modern hybrid cars. It is in this market segment that the main competition between various manufacturers of Li-Po batteries takes place.

The only area where lithium-polymer batteries are still inferior to nickel ones is the area of ​​super-high (40-50C) discharge currents. In terms of price, in terms of capacity, lithium polymer batteries cost about the same as NiMH. But competitors have already appeared in this market segment - (Li-Fe), the production technology of which is developing every day.

Charging Li-Po batteries

Most Li-Po batteries are charged using a fairly simple algorithm - from a constant voltage source of 4.20V/cell with a current limit of 1C (some models of modern power Li-Po batteries allow them to be charged with a current of 5C). The charge is considered complete when the current drops to 0.1-0.2C. Before switching to voltage stabilization mode at a current of 1C, the battery gains approximately 70-80% of its capacity. It takes about 1-2 hours to fully charge. The charger is subject to fairly stringent requirements for the accuracy of maintaining voltage at the end of the charge - no worse than 0.01 V/cell.
Of the chargers on the market, two main types can be distinguished - simple, non-“computer” chargers in the price category of $10-40, designed only for lithium batteries, and universal chargers in the price category of $80-400, designed to serve various types batteries.

The first ones, as a rule, have only an LED charge indication; the number of cans and the current in them are set using jumpers or by connecting the battery to various connectors on the charger. The advantage of such chargers is their low price. The main drawback is that some of these devices cannot correctly detect the end of the charge. They determine only the moment of transition from the current stabilization mode to the voltage stabilization mode, which is approximately 70-80% of the capacity.

The second group of chargers has much wider capabilities; as a rule, they all show the voltage, current, and capacity in mAh that the battery “accepted” during the charging process, which allows you to more accurately determine how charged the battery is. When using a charger, the most important thing is to correctly set the required number of cans in the battery and the charge current on the charger, which is usually 1C.

Li-Po Battery Operation and Precautions

It’s safe to say that lithium polymer batteries are the most “delicate” that exist, i.e. require mandatory compliance with several simple rules. We list them in descending order of danger:

  1. Battery recharge - charge to a voltage exceeding 4.20V per cell
  2. Battery short circuit
  3. Discharge with currents exceeding the load capacity or leading to heating of the Li-Po battery above 60°C
  4. Discharge below 3V voltage per jar
  5. Battery heating above 60ºС
  6. Battery depressurization
  7. Storing in a discharged state

Failure to comply with the first three points leads to a fire, all others - to complete or partial loss of capacity

From all that has been said, the following conclusions can be drawn:

  • To avoid a fire, you must have a normal charger and correctly set the number of cans to be charged on it.
  • It is also necessary to use connectors that exclude the possibility of short-circuiting the battery and control the current consumed by the device in which the Li-Po battery is installed
  • You need to be sure that your electronic device in which the battery is installed does not overheat. At +70ºС, a “chain reaction” begins in the battery, turning the energy stored in it into heat, the battery literally spreads, setting fire to everything that can burn
  • If you short-circuit an almost discharged battery, there will be no fire; it will quietly and peacefully “die” due to overdischarge
  • Monitor the voltage at the end of the battery discharge and be sure to turn it off after use
  • Depressurization is also the reason for failure of lithium batteries. No air should get inside the element. This can happen if the outer protective package (the battery is sealed in a package like heat-shrink tubing) is damaged due to an impact, or damage with a sharp object, or if the battery terminal is severely overheated during soldering. Conclusion - do not drop from a great height and solder carefully
  • Based on the manufacturers' recommendations, batteries should be stored in a 50-70% charged state, preferably in a cool place, at a temperature not exceeding 30°C. Storing in a discharged state has a negative impact on service life. Like all batteries, lithium polymer batteries have a slight self-discharge.

Li-Po battery assembly

To obtain batteries with high current output or high capacity, parallel connection of batteries is used. If you buy a ready-made battery, then by the marking you can find out how many cans it contains and how they are connected. The letter P (parallel) after the number indicates the number of cans connected in parallel, and S (serial) - in series. For example, "Kokam 1500 3S2P" means a battery connected in series with three pairs of batteries, and each pair is formed by two batteries connected in parallel with a capacity of 1500 mAh, i.e. The battery capacity will be 3000 mAh (when connected in parallel, the capacity increases), and the voltage will be 3.7V x 3 = 11.1V.

If you buy batteries separately, then before connecting them into a battery you need to equalize their potentials, especially for the parallel connection option, since in this case one bank will begin to charge the other and the charging current may exceed 1C. It is advisable to discharge all purchased banks to 3V with a current of about 0.1-0.2C before connecting. The voltage must be monitored with a digital voltmeter with an accuracy of at least 0.5%. This will ensure reliable battery performance in the future.

It is also advisable to perform potential equalization (balancing) even on already assembled branded batteries before their first charge, since many companies that assemble cells into a battery do not balance them before assembly.

Due to the decrease in capacity as a result of operation, in no case should you add new banks in series with the old ones - the battery will be unbalanced.

Of course, you also cannot combine batteries of different, even similar capacities into a battery - for example, 1800 and 2000 mAh, and also use batteries from different manufacturers in one battery, since different internal resistance will lead to unbalance of the battery.

When soldering, you should be careful; you should not allow the terminals to overheat - this can break the seal and permanently “kill” a battery that has not yet been used. Some Li-Po batteries come with pieces of a textolite printed circuit board already soldered to the terminals for easy wiring. This adds extra weight - about 1 g per element, but it takes much longer to heat the places for soldering wires - fiberglass does not conduct heat well. Wires with connectors should be secured to the battery case, at least with tape, so as not to accidentally tear them off when connecting to the charger multiple times

The nuances of using Li-Po batteries

I will give a few more useful examples that follow from what was said earlier, but are not obvious at first glance...

Over the long life of a battery, its elements, due to the initial small dispersion of capacities, become unbalanced - some banks “age” earlier than others and lose their capacity faster. With a larger number of cans in the battery, the process goes faster. This leads to the following rule: it is necessary to monitor the capacity of each battery element.

If a battery is found in an assembly whose capacity differs from other elements by more than 15-20%, it is recommended to refuse to use the entire assembly, or to solder a battery with fewer elements from the remaining batteries.

Modern chargers have built-in balancers, which allow you to charge all elements in the battery separately under strict control. If the charger is not equipped with a balancer, then it must be purchased separately and it is advisable to charge the batteries using it.

An external balancer is a small board connected to each bank, containing load resistors, a control circuit and an LED indicating that the voltage on a given bank has reached the level of 4.17-4.19V. When the voltage on a separate element exceeds the threshold of 4.17V, the balancer closes part of the current “to itself,” preventing the voltage from exceeding the critical threshold.

It should be added that the balancer does not prevent the overdischarge of some cells in an unbalanced battery; it only serves to protect against damage to the elements during charging and as a means of identifying “bad” elements in the battery.

The above applies to batteries composed of three or more elements; for two-can batteries, balancers, as a rule, are not used

According to numerous reviews, discharging lithium batteries to a voltage of 2.7-2.8V has a more detrimental effect on capacity than, for example, recharging to a voltage of 4.4V. It is especially harmful to store the battery in an over-discharged state.

There is an opinion that lithium-polymer batteries cannot be used at subzero temperatures. Indeed, the technical specifications for the batteries indicate an operating range of 0-50°C (at 0°C 80% of the battery capacity is retained). But nevertheless, it is possible to use Li-Po batteries at subzero temperatures, about -10...-15°C. The point is that you don’t need to freeze the battery before use - put it in your pocket where it’s warm. And during use, the internal heat generation in the battery turns out to be a useful property at the moment, preventing the battery from freezing. Of course, the battery performance will be slightly lower than at normal temperatures.

Conclusion

Considering the pace at which technical progress in the field of electrochemistry is moving, it can be assumed that the future lies with lithium energy storage technologies if fuel cells do not catch up with them. Wait and see…

The article uses materials from articles by Sergei Potupchik and Vladimir Vasiliev

Lithium polymer batteries appeared on the market not so long ago, but they already serve as a power source for many gadgets. These batteries are used in smartphones, tablets, laptops, children's toys and other equipment.

Batteries are gradually being improved, old errors and shortcomings are being corrected. But still, lithium-polymer batteries fail and sometimes can explode. Below we will discuss how to avoid premature breakdowns, where to buy, as well as the features of this type of battery.

Li-Po batteries are one of the types of lithium batteries. The development of polymer batteries was based on lithium-ion batteries. They use a liquid electrolyte, which causes some problems during operation.

The main goal of the specialists was to get rid of the old electrolyte, since it caused many difficulties.

In addition, several changes have been made to the operating principle of the battery.

To understand how lithium polymer batteries differ from others, you need to understand two main concepts:

  1. An electrolyte is an acid solution that conducts electric current. Unlike ordinary conductors, positively charged ions conduct current here.
  2. A polymer is a substance that consists of a chain of repeating monomers (a group of molecules).

So what have scientists changed about lithium-ion batteries? First, the electrolyte became solid. Secondly, polymer began to be used as an electrolyte. Hence the name of these batteries.

At the same time, the polymer is very thin, looks like a film. The polymer no longer conducts current, but it still has the ability to conduct ions.

Thus, the scientists obtained an electrolyte and a separator in one piece of polymer.

Electrochemistry today is developing rapidly, with new changes being constantly made to Li-Po designs. For example, rake-shaped electrolytes that contain lithium ions have recently been added to batteries.

Characteristics of Li-Po

The data written below is constantly changing, as progress in electrochemistry does not stand still.

All characteristics are relevant only in 2019. Additionally, may vary depending on the battery and manufacturer.

Main characteristics:

  1. Energy capacity - measured in mAh (milliamps per hour). If you remember your school physics course, ampere is current strength. The clock, in this case, characterizes the time during which this battery maintains the required current. To understand the essence of the characteristics, let’s take a regular 4000 mAh smartphone battery as an example. For one hour, such a battery produces a current of 4000 mA. If we take 4 hours, then the current will be approximately equal to 1000 mA and so on.
  2. The next characteristic is the number of discharges and charges, pay attention to it. This number determines how long the battery will last. Li-Pos don't have many cycles. The norm for these batteries is 400–500 cycles. When the battery has completed its 500 cycles, it can be thrown away. Ni-MH batteries have a minimum of 1000 cycles.
  3. Input and output voltage. Input is the voltage that should be in the outlet. The output is the voltage that the battery produces. Most often these two characteristics are equal, but there are exceptions.

Correct operation

Lithium polymer batteries are very delicate. There are many reasons why batteries fail.

Failure to comply with operating instructions leads to fire and complete malfunction.

Let's figure out how to use lithium polymer batteries so that they last a long time.

Operating rules:

  1. The battery must not be overcharged, that is, the voltage should not exceed 4.2 volts. Overcharging may cause bloating.
  2. Short circuit.
  3. Apply current to the battery that exceeds the permissible limit.
  4. Severe overheating (above 60 degrees).
  5. Damage to the housing and depressurization.
  6. Store lithium polymer batteries in a discharged state.

Due to the first three reasons, fire often occurs. To prevent this, use only working chargers. The correct connector, which has short circuit protection, will save you from a short circuit.

It is also necessary to control the current consumed by the device containing the lithium-polymer battery.

Overheating of the battery occurs due to the fact that the device itself, when heated, also heats the Li-Po battery.

If the battery temperature reaches 70 degrees, the energy stored in the battery begins to turn into heat, thereby increasing the already high temperature. At the same time, the battery begins to set fire to everything around it. Smartphones with lithium-polymer batteries and laptops especially suffer from this.

There is an opinion that Li-Po cannot be used at subzero temperatures. Despite the fact that the range in which the battery operates normally is set from 0 to 50 degrees, it can still be used at sub-zero temperatures.

The main thing is not to freeze the battery.

Keep it warm, for example in your pocket. The internal heat of the battery will not allow the battery to cool down. Of course, in cold weather the output will be slightly lower than when using the battery in warm conditions.

What are the advantages and disadvantages of lithium polymer batteries

  1. Polymer batteries have a large electrical capacity.
  2. The thickness of the batteries reaches one millimeter.
  3. The body shape can be any.
  4. If the battery is discharged, the voltage does not drop as much as in other batteries.
  5. Li-Po has no memory effect. In short, the memory effect is the loss of significant battery capacity.
  6. The battery can operate in a fairly wide temperature range (from -20 to 40 degrees).
  • if the ambient temperature is below -20 degrees, the battery discharges quickly;
  • high cost.

DIY battery assembly

To assemble the battery yourself, you need to buy batteries, or in common parlance - banks. To assemble, you need to be able to solder and understand basic electronics concepts.

To assemble the battery, all purchased banks must be connected in parallel. In order to determine the number of cans in a purchased battery, you need to look at the label. Not only the number of cans is written on it, but also the number of cans connected in series and in parallel.

Typically, the letter P indicates the number of cans connected in parallel, and the letter S indicates those connected in series. For example, the packaging says 3S2P. It is deciphered like this: under the case there are 3 rows of batteries connected in series, each row has 2 banks.

If you are using batteries that you purchased separately, then before connecting them to each other, you should equalize the potentials on the marks.

If this is not done, the banks will begin to charge each other, which will result in a current greater than 1C.

Also, before connecting, it is necessary to discharge all banks so that the voltage is 3V, with a current of 0.1-0.2C. Especially all of the above concerns parallel connections. The voltage is measured with a digital voltmeter, otherwise inaccuracies may occur.

Many manufacturers do not balance banks to speed up and save on battery production, so it is best to do the balancing yourself.

To avoid unbalancing the battery in the future, under no circumstances should you add new elements to the battery in succession with old ones.

The use of cans with different capacities can lead to imbalance, even if the difference between the values ​​is small. For example, 1800 mAh and 2000 mAh. Different manufacturers have batteries with different voltages, and this leads to imbalance.

When all the batteries have been purchased, you can start soldering the cells. Of course, you can come up with a layout of the elements on your own, but it’s best to take a ready-made one.

In order not to overheat the outputs and the seal of the can, we solder carefully, otherwise the battery will fail without even working.

You can purchase a special textolite printed circuit board on which it will be more convenient to solder the wires. It is soldered to each can. This adds a little weight to the jar (about 1 gram), but soldering becomes much more convenient, since fiberglass does not conduct heat well and can be heated for longer.

For balancing, a special board is used, which contains load resistors, a control circuit, and an LED that will light up if the voltage is above 4.2V.

If the voltage exceeds this value, the board closes part of the current, which prevents it from increasing further. Such a board must be soldered to each can.

Correct charging of Li-Pol

Charging the battery is a simple matter. Only a DC source with a voltage of 4.2V is enough. The current should be 1C, although many modern models can withstand as much as 5C.

A full battery charge takes 1–3 hours, depending on the model and its characteristics.

You can also stop charging the battery when the current drops to 0.1C. Before the batteries go into voltage stabilization mode, they gain 60–80% of the energy from the entire capacity, at a constant current of 1C.

To ensure proper charging, you must carefully select your charger. The voltage supplied by the charger should be 0.01 per cell.

There are two types of charges on the market. The first is budget devices, costing from 10 to 50 dollars, intended only for. The second is universal chargers that are suitable for different equipment. Of course, they cost much more, starting from $80.

Cheap chargers do not have an indicator showing current, voltage, and charging time. The number of cans and the required current are set using jumpers or by connecting the charger to different connectors on the device.

Plus a cheap option at a low price. The disadvantage of such charges is that they cannot accurately determine when to stop charging. All they can do is determine the moment of transition from current stabilization to voltage stabilization. But, as a rule, the battery is only 80% charged at this moment.

The second type of charger has more advantages than the first. They allow you to immediately find out the voltage, current, charge that was “transferred” to the battery in the process.

Conclusion

Lithium polymer batteries have changed a lot over the past few years. Many people suggest that they are the future of electrochemistry. Although fuel energy carriers are actively appearing on the market.

The constant development of technology has a beneficial effect on many aspects of people's lives. The need to have high-performance power supplies with a good balance between safety, cost and performance has led to the creation of lithium polymer cells.

Contents

What is a lithium polymer battery

Li polymer batteries are galvanic power sources that use polymer materials saturated with lithium as the electrolyte.

Lithium polymer technology has become a new stage in the development of lithium-ion power supplies, which has reduced the cost of their production process and made it possible to create miniature and flexible batteries.

When purchasing and using such batteries, you must understand the markings on them, which have the following features:

  • The battery capacity is indicated in mAh;
  • the number next to the English letter S in the marking indicates the number of individual cells (cans) in the battery, each of which has a nominal voltage of 3.7 volts and a maximum voltage of 4.2 volts;
  • the number next to the letter C means the maximum current output in units of C. The maximum discharge current in milliamps per hour is equal to the battery capacity multiplied by this value;
  • the number next to the letter P indicates the number of parallel-connected cans. When using one can, this value is usually not indicated.

Thus, the designation 2600 mAh 3S 20C indicates a Li-polymer battery with a capacity of 2600 mAh with a nominal voltage of 11.1 volts (maximum 12.6 volts), with three series-connected banks and a permissible discharge current of 52 amperes (2600x20 = 52000 mA).

How lithium polymer batteries are produced

The following technology is used in the production of Li-polymer power supplies:

  1. A controlled application of a suspension of cathode and anode active materials (two different processes) is carried out on the surface of aluminum or copper foil, which acts as a current collector.
  2. The foil with the applied material is dried and cut into elements of the required size and shape.
  3. A polymer electrolyte separator is prepared, which is then placed between layers of foil with the active materials of the cathode and anode.
  4. The multilayer battery is assembled, sealed and dried.
  5. When using a polymer separator that requires inclusions of gel electrolyte, it is filled with the required amount of electrolyte liquid.
  6. The contact pads are installed, packaged in a protective shell and its protruding parts are trimmed.
  7. External battery terminals are installed.
  8. A control charge/discharge cycle and testing are carried out.
  9. Rejection, sorting by container and application of appropriate markings are carried out.
  10. If necessary, wires are soldered to the battery terminals.
  11. Quality control is carried out, battery cells are packaged in a case, on which the necessary markings and packaging are applied.

Operating principle and design of a lithium polymer battery

The operating principle of Li pol batteries is based on the use of the semiconductor effect in polymer substances with inclusions of electrolyte ions. Adding an electrolyte to polymers causes an increase in their ionic conductivity while maintaining the insulating properties of the plastic with respect to electrons.

The electromotive force for lithium ions results from a reversible chemical reaction between an anode (plus) of carbon (usually graphite) and a cathode (minus) of cobalt, vanadium or manganese oxide placed in a polymer electrolyte with lithium salts.

There are three types of polymer electrolytes:

  1. Completely dry polymer electrolytes, which are plastic with the addition of lithium salts, produce low current at room temperatures, insufficient for most modern devices and are more expensive than conventional lithium-ion batteries.
  2. Gel-like polymer electrolytes, which are dry polymer electrolytes interspersed with plasticizer-solvents, have acceptable capacity, current and cost and are most often used in practice.
  3. Non-aqueous solutions of lithium salts distributed in a microporous polymer matrix by absorption.

Massively sold Li Po batteries are actually hybrids, combining not only pure dry polymer electrolyte, but also a small amount of gel electrolyte, which also contains lithium-ion sources.

Adding gel electrolyte inclusions to a solid polymer electrolyte increases its ionic conductivity and electrical characteristics, in particular, the operating current increases to the value required for most modern small-sized devices.

Lithium polymer battery: pros and cons

Li-polymer power supplies have the following advantages:

  • high energy density in relation to their mass, 4-5 times greater than that of nickel-cadmium batteries, and 3-4 times greater than that of nickel-metal hydride power supplies;
  • low self-discharge current and high current efficiency;
  • the ability to create flexible and very thin products;
  • no memory effect;
  • maintaining voltage within acceptable limits during operating discharge;
  • wide range of permissible temperatures during operation (from -20 to +40 degrees).

Lithium polymer batteries have some disadvantages:

  • fire hazard in case of overcharging/overheating. These batteries require the use of protective electronics that monitor charging current and temperature, as well as a special charging algorithm;
  • the aging effect, leading to a decrease in capacity during long-term storage and operation (it is believed that the battery loses up to 20% of capacity every year);
  • failure due to deep discharge (below 3 volts);
  • fear of overheating above 60 degrees and overcharging above 4.2 volts (at a voltage above 4.5 volts an explosion is possible);
  • The use of a thin shell (usually foil) in some of these batteries reduces the cost of Li Pol cells, but at the same time reduces their strength.

Where are Li Pol batteries used?

Due to its light weight and high power, this type of power supply is widely used to provide power to small and large devices, including:

  • mobile phones and smartphones;
  • radio-controlled models, quadcopters, microplanes;
  • power tools;
  • digital technology, ultrabooks;
  • electric cars.

Rules for using Li Pol batteries

To ensure the required level of safety and extend the life of healthy batteries, you must adhere to the following rules:

  1. if the batteries are damaged or swollen, they cannot be used and must be disposed of;
  2. Batteries must be charged using a high-quality charger under supervision, preventing the battery from overheating. If during charging there is a burning smell, swelling, or inflammation, you must stop it immediately and disconnect the battery from the charger;
  3. It is better to charge on a non-flammable surface, for example on a ceramic tile or porcelain plate; after fully charging the power source, it is better to let it cool and only then start using it;
  4. Do not allow a discharge below 3 volts, overheating or hypothermia, which reduce the capacity and the total number of charge-discharge cycles;
  5. the longest service life of LiPo cells is achieved by maintaining their charge level at 45%;
  6. The best charging mode for LiPo batteries is carried out by chargers from Sony for about three hours. It takes place in three stages:
    • First, for about one hour, charging is carried out to 70% with a direct current of 0.5-1 from the current output of the battery to a voltage of 4.2 volts;
    • Recharging for 1 hour to 90% with a voltage of no more than 4.2 volts with a gradually decreasing current (up to approximately 0.2 of the current output);
    • At the third stage, recharging is carried out over an hour to 100% with a small, constantly decreasing current.

Cheap chargers finish charging at the first stage, when the voltage reaches 4.2 v, so the battery does not reach its full capacity.

  • do not allow shock to the battery, short circuits or discharge with very high currents, overcharging above 4.2 volts per element of a composite battery - all these reasons can cause a fire;
  • if composite batteries of several Li Pol elements are used, then it is better to charge them separately, or use a special equalizing charge with balancing for each element. The principle of operation of such a device is to stop the charge of individual elements when they reach a voltage of about 4.17 volts;
  • Before putting new batteries into operation, it is better to calibrate them by fully charging and discharging them twice.

In some Li Pol batteries, when discharged below 2.5 volts, lithium metallization is possible, which leads to the creation of conductive bridges inside the battery and a short circuit. When charging such a battery, uncontrolled heating occurs, which can lead to the explosion of such a power source. Therefore, it is better not to use batteries in which the voltage has dropped below the critical level of 3 volts, and when the voltage drops to 2.5 volts or lower, they must be disposed of.

How to store lithium polymer batteries

It is advisable to store charged LiPo batteries in protective cases at room temperature when charging at a level of 3.6-3.8 volts.

Before storing LiPo cells, it is recommended to charge them to 40-50%, disconnect them from the devices they power, and check the charge level periodically, at least once every six months.

Recycling lithium polymer batteries

Disposal of LiPo power supplies is of particular relevance due to their high fire hazard. They are less toxic than nickel-cadmium batteries, but still contain substances harmful to the environment.

In order to completely and safely dispose of Li-polymer batteries, the following requirements must be observed:

  • Disposal of discharged batteries is carried out in plastic containers with a water-salt solution (about half a glass of salt per 1 liter of water) for about 2 weeks (until gas formation stops) in a non-residential area. After this, they can be thrown away with regular trash;
  • Before disposal, the batteries must be discharged to at least one volt (this can be done with a light bulb as a load);
  • if the battery case is damaged, then it does not need to be discharged, but must be disposed of in a water-salt solution;
  • if the discharge is carried out with a current more than permissible, associated with the value of the maximum current output C, then the battery must be placed in a bucket of sand or in another place protected from fire;
  • Mechanical destruction of batteries not treated in a saline solution is not allowed, which could cause a fire. Batteries with a cobalt cathode are especially dangerous in this regard.

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-ion (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 -


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