What is the difference between lithium polymer and lithium ion batteries? Batteries: Li-ion, Li-Pol, Li-ion-pol and rules of their operation

Progress is moving forward, and to replace the traditionally used NiCd (nickel-cadmium) and NiMh (nickel-metal hydride) we have the opportunity to use lithium batteries. With a comparable weight of one element, they have a higher capacity compared to NiCd and NiMH, in addition, their element voltage is three times higher - 3.6V/element instead of 1.2V. So for most models, a battery of two or three cells is sufficient.

Among lithium batteries, there are two main types - lithium-ion (Li-Ion) and lithium polymer (LiPo, Li-Po or Li-Pol). The difference between them is the type of electrolyte used. In the case of LiIon, this is a gel electrolyte; in the case of LiPo, it is a special polymer saturated with a lithium-containing solution. But for use in power plants of models, lithium-polymer batteries are most widely used, so in the future we will talk about them. However, the strict division here is very arbitrary, since both types differ mainly in the electrolyte used, and everything that will be said about lithium-polymer batteries almost fully applies to lithium-ion batteries (charge, discharge, operating features, safety precautions ). From a practical point of view, our only concern is that lithium polymer batteries currently provide higher discharge currents. Therefore, on the model market they are mainly offered as a source of energy for power plants.

Main characteristics

Lithium-polymer batteries with the same weight exceed the energy intensity of NiCd by 4-5 times, NiMH by 3-4 times. The number of operating cycles is 500-600, with discharge currents of 2C until a loss of capacity of 20% (for comparison - for NiCd - 1000 cycles, for NiMH - 500). Generally speaking, there is still very little data on the number of operating cycles, and their characteristics given in this case must be taken critically. In addition, their manufacturing technology is improving, and it is possible that at the moment the figures for this type of battery are already different. Just like all batteries, lithium batteries are subject to aging. After 2 years, the battery loses about 20% of its capacity.

Of the variety of power lithium-polymer batteries available for sale, two main groups can be distinguished - high-discharge (Hi discharge) and conventional. 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”. For example, if the discharge current is 3C and the battery capacity is 1 Ah, then the current will be 3 A.

The maximum discharge current of conventional batteries, as a rule, does not exceed 3C; some manufacturers indicate 5C. Fast-discharge batteries allow a discharge current of up to 8-10C. Such batteries are somewhat heavier than their low-current counterparts (by about 20%), and their names contain the letters HD or HC after the capacity numbers, for example, KKM1500 is a regular battery with a capacity of 1500 mAh, and KKM1500HD is a fast-discharge battery. I would like to immediately make a small note for those who like to experiment. Fast-discharge batteries are not used in household appliances. Therefore, if you get the idea of getting a battery from a cell phone or video camera on the cheap, it’s difficult to count on a good result. Most likely, such a battery will die very quickly due to violation of the intended operating modes.

Applications and cost

The use of lithium-polymer batteries allows you to solve two important problems - increase the operating time of the motor and reduce the weight of the battery.

When replacing an 8.4 V NiMH 650 mAh battery with two regular, non-fast-discharging lithium batteries with a capacity of 2 Ah, we get a battery with 3 times the capacity, 11 g lighter and with a slightly lower voltage (7.2 volts)! And if you use fast-discharging batteries, then large aircraft can fly without being inferior in power to an internal combustion engine. To confirm this, the 7th place in the F3A World Aerobatic Championship was taken by an American in an electric aircraft. Moreover, it was not a small buzzer, but a normal two-meter plane, like the other participants who had models with internal combustion engines!

Lithium polymer batteries have proven themselves very well in small helicopters such as Piccolo or Hummingbird - for example, even when using a standard brushed motor, the flight time on two 1 Ah banks is more than 25 minutes! And when replacing the motor with a brushless one - more than 45 minutes!

And, of course, lithium batteries are simply irreplaceable when it comes to indoor aircraft weighing 4-20 g. In this area, NiCd cannot compare with them - there are simply no such batteries (for example, a 45 mAh can weighs 1 g, 150 mAh - 3.2 d), which with such a small weight would provide the necessary power - even for 1 minute!

The only area where lithium-polymer batteries are still inferior to Ni-Cd is the area of super-high (40-50C) discharge currents. But progress is moving forward, and maybe in a couple of years we will hear about new successes in this area - after all, 2 years ago no one had heard of fast-discharge lithium batteries either...

Here, for example, are the main characteristics of Kokam LiPo batteries:

Name	Capacity, mAh	Dimensions, mm	Weight, g	Maximum current
Kokam 145	145	27.5x20.4x4.3	3.5	0.7A, 5C
Kokam 340SHC	340	52x33x2.8	9	7A, 20C
Kokam 1020	1020	61x33x5.5	20.5	3A, 3C
Kokam 1500HC	1500	76x40x6.5	35	12A, 8C
Kokam 1575	1575	74x41x5.5	32	7A, 5C

In terms of price per capacity, lithium polymer batteries cost about the same as NiMH.

Manufacturers

Currently, there are several manufacturers of lithium polymer batteries. The leader in the number of batteries produced and one of the first in quality is Kokam. Also known are Thunder Power, I-Rate, E-Tec, and Tanic (presumably this is a second name for Thunder Power or is one of the Thunder Power sellers under its own name). You can view Kokam types on the website www.fmadirect.com, batteries from different manufacturers are offered on the website www.b-p-p.com and www.lightflightrc.com.

There is also Platinum Polymer, offered on the website www.batteriesamerica.com, presumably another name for I-Rate.

The range of battery capacities is very wide – from 50 to 3000 mAh. To obtain large capacities, parallel connection of batteries is used.

All batteries are flat in shape. As a rule, their thickness is more than 3 times less than the shortest side, and the conclusions are made on the short side in the form of flat plates.

I-Rate, as far as I know, does not yet make fast-discharge batteries, and their batteries have one feature: one of the electrodes is aluminum, and soldering it is problematic. This makes them inconvenient to assemble the battery yourself.

E-Tec batteries are something in between, they are not declared as fast-discharging, but their discharge current is higher than that of conventional ones - 5-7C.

The leaders in popularity are Kokam and Thunder Power, with Kokam mainly used in light and medium models, and Thunder Power in medium, large and giant (more than 10 kg!). Obviously, this is due to the price and the availability of powerful assemblies in the range - up to 30 volts and 8Ah capacity. Next come Tanic and E-tec, but there is little mention of I-rate. For some reason, Platinum Polymer is popular only in America, and it is used almost exclusively on slow slow flyers.

Charging Lithium Polymer Batteries

The batteries are charged according to a fairly simple algorithm - charge from a constant voltage source of 4.20 volts/cell with a current limit of 1C. The charge is considered complete when the current drops to 0.1-0.2C. After switching to voltage stabilization mode at a current of 1C, the battery gains approximately 70-80% of its capacity. It takes about 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, we can distinguish the main types - simple, non-“computer” chargers, in the price category of $10-40, intended only for lithium batteries, and universal ones - in the price category of $120-400, intended for various types of batteries, including for LiPo and Li-Ion.

The first ones, as a rule, have only LED charge indication; the number of cans and the current in them are set by jumpers. The advantage of such chargers is their low price. The main drawback is that some of them do not know how to correctly indicate the end of the charge. They show only the moment of transition from current stabilization mode to voltage stabilization mode, which is approximately 70-80% of the capacity. To complete the charge, you need to wait another 30-40 minutes.

The second group of chargers has much wider capabilities; as a rule, they all show the voltage, current and capacity (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 charging current on the charger. The charge current is usually 1C.

Operation and Precautions

It is safe to say that lithium-polymer batteries are the most “delicate” batteries in existence, that is, they require mandatory compliance with several simple but mandatory rules, due to non-compliance with which either a fire occurs or the battery “dies”.

We list them in descending order of danger:

Charge to a voltage greater than 4.20 volts/cell.
Battery short circuit.
Discharge with currents exceeding the load capacity or heating the battery above 60°C.
Discharge below 3.00 volts/cell.
Battery heating above 60°C.
Battery depressurization.
Storage 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 eliminate the possibility of short-circuiting the battery (because of this, my friend had a table on which batteries were charged and a curtain burned) and to control the current consumed by the motor at “full throttle”. In addition, it is not recommended to cover the batteries on all sides from the air flow on the model, and if this is not possible, then special channels for cooling should be provided.

In cases where the current consumed by the engine is more than 2C, and the battery on the model is closed on all sides, after 5-6 minutes of running the motor, you should stop it, and then pull it out and touch the battery to see if it is too hot. The fact is that after heating above a certain temperature (about 70 degrees), a “chain reaction” begins to occur 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 die quietly and peacefully due to overdischarge... This leads to the second important rule: monitor the voltage at the end of the battery discharge and be sure to disconnect the battery after use!

Some speed controllers (Jeti is especially guilty of this) do not stop consuming current after turning off the standard switch. I don’t know what made the Czechs make such a strange decision. But the fact remains that almost all models of controllers for Jetti brushless motors (including the new “Advanced” series), which have a BEC, that is, a power supply stabilizer for the receiver and machines from the power supply, do not provide complete de-energization of the circuit with a standard switch. Only the receiver and servos are turned off, and the controller continues to consume a current of about 20 mA. This is especially dangerous, since you can’t see that the power is on, the cars are standing still, the motor is silent... And if you forget about the connected battery for a day or two, it turns out that you can say goodbye to it - it doesn’t like deep-discharge lithium.

Of course, you should remember that the engine controller must be able to work with lithium batteries, that is, have an adjustable engine shutdown voltage. And we must not forget to program the controller for the required number of cans. However, now a new generation of controllers has appeared that automatically determine the number of connected cans.

Depressurization is another reason for lithium batteries to fail, since air should not get inside the cell. This can happen if the outer protective package is damaged (the battery is sealed in a package like heat-shrink tubing), as a result of impact or damage with a sharp object, or if the battery terminal is 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 temperatures no higher than 20°C. Storing in a discharged state negatively affects service life - like all batteries, lithium-polymer batteries have a small self-discharge.

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 from 3 pairs of batteries, and each pair is formed by 2 batteries connected in parallel with a capacity of 1500 mAh, that is, the battery capacity will be 3000 mAh (when connected in parallel, the capacity increases), and the voltage – 3.7*3 = 11.1V..

If you buy batteries separately, then before connecting them into a battery you need to equalize their potentials. This is especially true 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 cans to 3 volts with a current of 0.1C - 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 must be careful; you must not allow the terminals to overheat, as this can break the seal and permanently kill the battery that has not yet had time to fly. Some types of Kokam batteries come with pieces of the circuit board already soldered to the terminals for easy wiring. This adds extra weight - about 1g per element, but it takes much longer to heat the places for soldering wires - fiberglass does not conduct heat well. The wires with connectors should be secured to the battery case, at least with tape, so as not to accidentally tear off the terminal at the root.

Application nuances

So, let us emphasize once again the most important points related to the use of lithium-polymer batteries.

Use a normal charger.
Use connectors that prevent short-circuiting the battery.
Do not exceed permissible discharge currents.
Monitor the battery temperature when there is no cooling.
Do not discharge the battery below a voltage of 3 V/cell (remember to disconnect the battery after the flight!).
Do not subject the battery to shock.

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

When using commutator motors, it is necessary to avoid situations where the motor is stopped (for example, the model is lying on the ground) and the transmitter is given full throttle. The current is too high, and we risk exploding the battery (if the motor or regulator does not burn out first). This issue has been discussed numerous times in the RC Groups forums. Most regulators for brushed motors turn off the motor when the signal from the transmitter is lost, and if your regulator can do this, I would advise turning off the transmitter if the model fell, for example, into the grass far from you - there is less risk of touching the dangling throttle when searching for a model on the transmitter belt and not notice it.

Over the course of a long battery life, 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 - sometimes it is necessary to control the capacity of each battery element separately. To do this, you can measure its voltage at the end of the charge. How often? It is still difficult to establish exactly this - too little operating experience has been accumulated. As a rule, it is recommended that approximately 40-50 cycles after the start of operation, every 10-20 cycles, check the voltage of the battery cells during charging to identify “bad cells”.

It is not recommended to “zero” the battery by driving the motor until it stops rotating altogether. Such treatment will not harm a new battery, but for a slightly unbalanced one, this is an extra risk of discharging the “badest bank” below 3 volts, due to which it will lose capacity even more.

When the capacities differ by more than 20%, such a battery cannot be charged entirely without special measures!

To automatically balance battery cells when charging, so-called balancers are used. This is a small board connected to each bank, containing load resistors, a control circuit and an LED indicating that the voltage on this bank has reached the level of 4.17 - 4.19 volts. When the voltage on an individual element exceeds the threshold of 4.17 volts, the balancer closes part of the current “to itself,” preventing the voltage from exceeding the critical threshold. By the simultaneous lighting of the LEDs, you can see which banks have a lower capacity - the LED on their balancer will light up first. Balancers have one important additional requirement: the current they consume from the battery in “standby” mode must be small, usually 5-10 µA.

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 cells during charging and as a means of indicating “bad” cells in the battery. The above applies to batteries made up of 3 or more elements; balancers, as a rule, are not used for 2-can batteries.

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 capacity is retained). But nevertheless, you can fly them at temperatures around –10...-15 °C. The point is that you don’t need to freeze the battery before the flight - put it in your pocket where it’s warm. And during flight, 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 belongs to lithium-polymer batteries - if fuel cells do not catch up with them. As demand for batteries increases and production volume increases, the price will inevitably fall, and then lithium will finally become as common as NiMH. In the West, this time has already arrived for six months, at least in America. The popularity of electric aircraft with lithium-polymer batteries is growing. I would like to hope that brushless motors and controllers for them will also become cheaper, but in this area the progress of price reductions is moving less rapidly. After all, just two years ago the question was asked on the forum: “Does anyone really fly a brushless?” And there was no mention of lithium batteries at all then...

In general, we'll wait and see.

Portable chargers have become an integral element of modern everyday life. The quality of batteries is the main condition for their performance, efficiency and safety. Manufacturers of chargers use two types of batteries in their designs - lithium-ion and lithium-polymer. For the average consumer, unfamiliar with the features of different types, it often becomes a problem to choose one or another type of battery.

What is the difference between these varieties, which one would be more correct to choose - all these questions require detailed knowledge about each type. In this article we will reveal the features of lithium-ion and lithium-polymer batteries, introduce them to their technical properties, charging methods, and service life.

Differences between lithium-ion and lithium-polymer batteries

Battery models produced using different technologies perform the same energy supply function. The design features of each type affect the reported power, service life, and degree of explosion protection. It cannot be stated unequivocally that a more modern type of battery is better than an outdated one. There are practical advantages and disadvantages to both technologies. The Li-pol and Li-ion models have similar operating schemes, but differ in configuration and technical parameters.

To understand which is better - Li-polymer or Li-ion, let’s take a closer look at each type separately. You should compare battery types and make a choice in favor of one type or another based on the following indicators:

price;
weight to capacity ratio;
safety;
intended use in a device for a specific purpose;
temperature operating conditions.

When choosing one of the two types, consider the scope of application and financial capabilities.

Lithium-ion batteries: features and specifications

Initially, lithium-based models were produced using manganese and cobalt as the main element (active electrolyte). Modern lithium-ion batteries have undergone design changes. Their productivity depends not on the substance used, but on the order in which the elements are placed in the block. The components of a modern Li-Ion battery are electrodes and a separator. Materials – aluminum and copper (copper anodes and aluminum foil as a cathode base).

Special current collector terminals provide internal connection between the anode and cathode, and the electrolyte impregnation of the separator mass creates a favorable environment for charge maintenance. The positive charges of lithium ions trigger chemical reactions, form bonds, and provide energy output. The principle of operation of a lithium-ion based power supply is reminiscent of the operation of a full-size gel battery.

Lithium polymer batteries

Since lithium-ion models cannot cope with many modern tasks, they are gradually being replaced by polymer elements. Li-ion batteries did not have a high level of safety and were quite expensive. To eliminate these shortcomings and operational problems, and make the batteries more efficient, the developers decided to change the electrolyte. Instead of impregnating the porous separator, polymer electrolytes were used in the battery design.

The lithium polymer cell has a thickness of 1 mm, which allows the battery to be compact in size. Replacing liquid electrolytes with polymer films eliminated the high risk of battery ignition and made it safe. The comparison table below will help you clearly determine how Li-ion differs from Li-Pol.

Specifications	Li-ion	Li-Pol
Energy intensity		low, the number of charge and discharge cycles is less
Standard size	small selection	high choice, independence from standard cell format
	slightly heavier
		almost twice as high for the same size
Life time	approximately the same	approximately the same
Risk of explosion and fire	taller	built-in protection against electrolyte leakage and overcharging
Charging time
	up to 0.1% monthly	less active

The design of polymer lithium battery devices completely eliminates the presence of electrolyte in the form of liquid or gel. You can clearly imagine the difference in technology when considering the operating principle of modern automotive power supply devices. Safety concerns have led to the exclusion of liquid electrolytes from everyday practice. But until recently, impregnated porous structures were used in car batteries.

The introduction of polymer-lithium elements presupposed a solid-state basis. A characteristic difference from lithium-ion batteries is the process of contact action of the active substance plate with lithium and the prevention of the formation of dendrites during cycling. It is this feature that protects the battery cells from fire or explosion.

Life time

Both lithium-ion and lithium-polymer batteries are subject to intensive aging. They provide about nine hundred full charge cycles before they become unusable. It does not matter how active the device was used. If the battery has not been used at all for a long time, a reduction in service life will nevertheless occur.

After just a year, the capacity becomes significantly reduced in service life, and after two or three years it can be stated that the battery has completely failed. This is a common drawback of lithium batteries, and you should choose a more durable model only depending on the reputation of the manufacturer and reviews of specific models.

Additional protection

If we consider the question of what is the difference between Li-ion and Li-Pol batteries, it is worth paying attention to the built-in protective systems. Lithium polymer models require additional internal protection features. They are characterized by cases of burnout due to overheating of the elements. Such consequences are caused by the internal stress of various work areas.

In order to protect the device from unauthorized overcharging, overheating of parts and burnout, the design uses a special stabilizing system and a current limiting mechanism. This increases the safety of lithium-polymer models, but significantly increases the cost of the battery due to the use of protective elements.

Part of the design involves electrolytic components in the gel formation. Composite batteries are used in many portable devices. They are extremely sensitive to temperature changes and require strict adherence to operating rules. The polymer-based battery can be used in devices with heating in the range of 60-100 degrees.

Manufacturers enclose the internal part in a housing with heat-insulating properties - it is convenient to use such batteries in hot climates. In conditions where the temperature regime does not meet operating requirements, elements with a polymer component are used as backup.

Features of battery charging

The lithium polymer battery will require at least three hours of charging to recharge. In this case, the block does not heat up. There are two stages of filling. The first occurs until peak mode is established, which is maintained until charging reaches 70%. Under normal voltage conditions, a residual charge of 30% is accumulated. Recharging must be performed according to a strict schedule, waiting for complete discharge and carrying out the procedure every 500 hours of use of the device. This mode maintains a constant filling volume.

The battery must only be connected to a stable power supply, without voltage surges or interference. You should only use appropriate chargers that match the characteristics stated in the description. An important point: during the charging process, all connectors must be connected correctly; disconnection must not be allowed. Li-Pol elements are extremely sensitive to all kinds of overloads, excessive current levels, mechanical shock and hypothermia. The tightness of solid elements should be ensured.

Li-ion cells charge using much the same principles as polymer cells, but are more sensitive and less reliable in terms of safety. The charging time for both types is approximately the same, but the polymer element is more capricious in terms of the quality of the power supply point.

The better lithium-ion battery

Lithium-ion batteries are more familiar to consumers; they have a number of operational advantages:

the price is lower than a lithium polymer battery;
standardized standard sizes allow you not to make mistakes when choosing a model;
widespread scope of application.

Powerful lithium batteries are effectively used for devices that require short-term high current consumption. The temperature regime, as with polymer-based devices, is of key importance during operation.

The average user does not feel a noticeable difference, but, from the point of view of the rationality of the scope of application, this type of battery is convenient in chargers for the following equipment:

cordless tools (screwdrivers, saws, grinders);
laptops;
Cell phones;
electric cars;
home robots;
wheelchairs.

Before choosing the optimal type of charging, you need to know exactly what device it will be used for. This is especially important if you plan to universally use and service several portable devices at once.

It is rational to use lithium polymer batteries where weight and temperature are important factors. They are “afraid” of frost and are not very convenient for portable tools and gadgets. Therefore the main area of use:

quadcopters;
airsoft guns;
toys;
CCTV Cameras.

When choosing the appropriate type of charger, pay attention to the scope of use, cost and level of safety. Read user reviews about products from different manufacturers and make a choice.

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 varieties 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;

Electrolyte in the form of a microporous polymer matrix in which non-aqueous solutions of lithium salts are sorbed.

If we compare polymer and liquid 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.

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

Explosion, electrolyte leakage, temperature increase by 100°C

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.

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.

For example, 3C. For conventional batteries, the maximum discharge current is no more than 3-5C. Fast-discharge models have a maximum discharge current of 8─10C. The weight of fast-discharge batteries is approximately 20 percent higher than that of standard models. The marking of such batteries contains the symbols HC or HD.

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.

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.

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

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.

The principle of operation of batteries is based on the reversibility of the chemical reactions occurring in them. The accumulation of battery charge is carried out by charging it, that is, by passing an electric current in the opposite direction relative to the movement of the current when the battery is discharged.

A battery is several batteries connected together into one electrical circuit.

The main characteristic of a battery is its capacity. Battery capacity is the maximum possible usable charge of the battery. Or in other words, battery capacity is the amount of energy that a fully charged battery delivers when discharged to the lowest permissible voltage. In the SI system, battery capacity is measured in coulombs, but a non-system unit is usually used - ampere-hour. 1 A/h = 3600 C. Battery capacity can also be indicated in watt-hours. Another main characteristic of electric batteries is the output voltage of the battery. Knowing the output voltage of the battery, you can easily convert the battery capacity indicated in watt-hours to the more common ampere-hour.

The electrical characteristics of batteries depend on the material of the electrodes and the composition of the electrolyte. The table below shows the most commonly used types of electric batteries.

Battery type	Output voltage (V)	Application area
Lead Acid		trolleybuses, trams, cars, motorcycles, electric forklifts, stackers, electric tractors, emergency power supply, uninterruptible power supplies
nickel-cadmium (NiCd)		construction power tools, trolleybuses, household electrical appliances
nickel metal hydride (NiMH)		household electrical appliances, electric cars
lithium-ion (Li‑ion)	3,7 (3.6)	mobile devices, construction power tools, electric vehicles
lithium polymer (Li‑pol)	3,7 (3.6)	mobile devices, electric vehicles
nickel-zinc (NiZn)		household electrical appliances

As the battery is used, its output voltage and current drop. When all the charge is used, the battery stops working. Charge batteries from any DC source with a higher voltage while limiting the current. Typically, the charging current, measured in amperes, is 1/10 of the battery's rated capacity (in ampere hours). Some battery types have different limitations that must be taken into account when charging the battery and when using it. For example, NiMH batteries are sensitive to overcharge, while lithium batteries are sensitive to overdischarge, voltage and ambient temperature. NiCd and NiMH batteries have a “memory effect”. It is expressed in a decrease in battery capacity when charging an incompletely discharged battery. Also, these types of batteries have significant self-discharge, that is, they gradually lose charge even when they are not connected to a load. Drip charging helps combat this effect.

Lithium-ion battery (Li-ion)- a type of electric battery that is most widely used in modern consumer electronic devices. Now such batteries are used in mobile phones, laptops, tablets, electric cars, digital cameras, video cameras, etc.

For the first time, G.N. took up the development of lithium batteries. Lewis in 1912. But it wasn't until the 1970s that the first commercial examples of primary lithium cells began to appear.

In the 80s of the last century, a large number of experiments were carried out, during which it was found that when cycling a current source with a metal lithium electrode, dendrites are formed on the lithium surface. As a result, dendrites grow to the positive electrode and a short circuit occurs inside the lithium cell. This put such power supplies out of action. The temperature inside the battery reaches the melting point of lithium. This causes the battery to explode.

In an effort to develop a safe lithium power source, engineers have led to the replacement of cycle-unstable lithium metal in the battery with lithium interstitial compounds in carbon and transition metal oxides. The most commonly used materials for creating lithium batteries are graphite and lithium cobalt oxide (LiCoO2). In such a battery, during charge-discharge, lithium ions move from one implantation electrode to another and back. Although such electrode materials have a specific electrical energy that is several times lower than that of lithium, batteries based on them are much safer. The first lithium-ion batteries were developed by Sony in 1991. Currently, Sony is the largest manufacturer of lithium-based batteries.

Characteristics:

Energy density: from 110 to 200 W*h/kg

Internal resistance: 150 to 250 mOhm (for 7.2V battery)

Number of charge/discharge cycles until 20% capacity is lost: from 500 to 1000

Fast charge time: 2-4 hours

Allowable overcharge: very low

Self-discharge at room temperature: about 7% per year

Maximum cell voltage: about 4.2 V (battery fully charged)

Minimum voltage: about 2.5 V (battery completely discharged)

Load current relative to capacity (C):

Peak: more than 2C

Most acceptable: no more than 1C

Operating temperature range: −20 °C to +60 °C

Device .

Initially, coke was used as anodes, but later graphite was used. Lithium oxides with cobalt or manganese are used as a cathode.

When lithium-ion batteries are charged, the following chemical reaction occurs:

on cathodes: LiCoO 2 → Li 1-x CoO 2 + xLi + + xe −

on anodes: С + xLi + + xe − → CLi x

While charging the battery, a reverse reaction occurs.

Advantages of lithium batteries.

1. High energy density.

2. Low self-discharge.

3. No “memory effect”.

4. Ease of use.

Disadvantages of lithium batteries.

1. Lithium-ion batteries are susceptible to explosive destruction when overcharged or overheated. To avoid this effect, all household lithium batteries are equipped with a built-in electronic circuit that controls the battery charge, preventing it from overcharging and overheating.

2. If not used carefully, batteries may have a shorter life cycle than other types of batteries. A deep discharge of the battery completely destroys the lithium-ion cells.

3. Optimal storage conditions for lithium-ion batteries are achieved at 40-50% charge of the battery capacity and at an ambient temperature of about 5 °C. Low temperature is a more important factor for low capacity loss during long-term storage.

4. Strict charging conditions for lithium-ion batteries make their use in alternative energy extremely inconvenient. This happens because wind turbines and solar panels cannot provide constant current throughout the charge cycle.

Aging.

Even if a lithium battery is not used, it begins to age immediately after production.

Lithium polymer and lithium ion batteries lose their capacity when charged, unlike nickel and nickel metal hydride batteries. The higher the battery charge and the temperature during its storage, the shorter its service life. It is better to store lithium batteries charged at 40-50% and at a temperature of 0 to 10 °C. Overcharging, as well as overdischarging, reduces the capacity of such batteries.

Lithium polymer battery (Li-pol or Li-polymer)- This is the most advanced design of a lithium-ion battery. It uses a polymer material with inclusions of a gel-like lithium-conducting filler as an electrolyte. They are widely used in smartphones, mobile phones and other digital equipment.

Ordinary household lithium-polymer batteries cannot deliver high current, but special power lithium-polymer batteries have been developed that can deliver a current of 10 or more times the numerical value of the capacity. Such batteries are widely used in radio-controlled models, as well as in power tools and in some modern electric vehicles. Similar batteries are used in the new braking energy conversion technology - KERS.

Advantages of lithium polymer batteries.

1. High energy density per unit volume and mass.

2. Low self-discharge.

3. Small thickness of elements - from 1 mm.

4. The ability to obtain very flexible forms;

5. Not a large voltage drop as the discharge progresses.

6. The number of operating cycles is from 300 to 500, with discharge currents of 2C up to a capacity loss of 20%.

Disadvantages of lithium polymer batteries.

1. Batteries are a fire hazard if overcharged or overheated. To avoid this effect, all household lithium batteries are equipped with a built-in electronic circuit that controls the battery charge, preventing it from overcharging and overheating. Special charger algorithms are also required.

2. The operating temperature range of lithium polymer batteries is limited. These elements do not work well in the cold.

Just like lithium-ion batteries, lithium polymer batteries are subject to aging.

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Lithium polymer batteries represent an improved design of the world famous lithium-ion batteries. It is planned that these devices will soon completely displace nickel-metal hydride and nickel-cadmium devices from the market. batteries. Lithium polymer cells are increasingly used in a wide variety of electronic devices as a power source. With the same weight, their energy capacity is several times higher than nickel-metal hydride and nickel-cadmium structures.

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

Kinds

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

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

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

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

There are developments of polymer batteries that use a metal anode. Some companies have managed to significantly expand the operating temperature range and current density. These types of batteries can be used in various household appliances and electronics.

At the same time, different manufacturers use different electrode materials, electrolyte structure and assembly technology. As a result, manufactured batteries may have completely different parameters. But all companies producing such batteries note that the stable operation of lithium-polymer batteries is ensured by the homogeneity of the polymer electrolyte. This in turn depends on the number of components, as well as the polymerization temperature.

Battery options are already being produced with a thickness of only 1 millimeter. Thanks to this, manufacturers can produce very compact mobile devices.

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

Regular.
Fast-discharge.

Device

Lithium polymer batteries work on the principle of moving a number of polymer elements into semiconductor substances, provided that electrolyte ions are included in them. As a result, a significant increase in conductivity occurs. According to the design, these batteries are distinguished by their electrolytic composition.

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

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

Operating principle

Lithium polymer batteries operate on a principle similar to lithium-ion cells, meaning they operate on a reversible chemical reaction. Here, the anode is a carbon material into which lithium ions are introduced. The cathode uses vanadium, manganese or cobalt oxides. The operation of such a battery is based on the ability of polymers to transform into a semiconductor state due to the inclusion of electrolytic ions in them.

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

Application

Lithium polymer batteries are increasingly used. Such batteries can significantly increase the operating time of the device with a reduced battery weight. Thanks to this, it is possible to obtain an energy carrier that will have several times greater capacity. Using fast-discharging batteries will provide even greater performance. Therefore, such batteries become an excellent option for radio-controlled models of airplanes and helicopters, including other radio-controlled devices.

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

Typical lithium polymer batteries are used as power sources, which are required for electronic devices that consume relatively little current. These could be laptops, smartphones, and so on. Fast-discharging batteries are used in devices where high current consumption is required. Similar batteries are used in modern, portable electric tools and radio-controlled devices.

Limitations of use

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

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

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

Benefits of Lithium Polymer Batteries

Quite high energy density.
Small self-discharge parameter.
There is no memory effect.
Lithium polymer batteries are slightly superior to their lithium counterparts in terms of battery capacity and duration of use.
Manufacturing batteries only one millimeter thick.
Applications in a fairly wide temperature range: from minus 20 to plus 40 degrees Celsius.
Possibility of giving the battery different shapes.
Slight voltage drop during discharge.