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

The operating time of modern smartphones without recharging is determined by their battery and its characteristics.

What types of batteries are there?

Nickel-cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH) batteries are no longer relevant - they worked properly for a long time, but had a number of disadvantages. Our gadgets in most cases use lithium-based batteries - lithium-ion (Li-Ion) and lithium polymer (Li-Pol).

One of the main characteristics of a battery is capacity. It determines how much electricity the battery can store and how long the device can operate autonomously. The most common batteries are those with a capacity of 2000 to 3000 mAh (milliampere/hour). The dimensions of lithium-ion sources remain very compact, unlike their predecessors.

Lithium-polymer batteries differ from lithium-ion batteries in a variety of geometric shapes and, which is especially important now, in their minimum thickness, which starts from 1 mm. This allows them to be used in very thin smartphones.

Lithium batteries have a long service life if used correctly. Manufacturers of many well-known smartphones have provided for battery replacement only at a service center, making the device body monolithic, and the back cover and battery non-removable. Without special equipment and knowledge, the user will not be able to carry out this operation on his own.

Temperature during operation. The battery capacity is directly affected. High temperatures promote faster energy storage; at low temperatures, the capacity drops significantly. If you use an insufficiently charged one, it will quickly run out. Moreover, there is a risk of the charge dropping to zero, which is extremely undesirable - lithium batteries suffer from complete discharge.

And the opposite situation. A 100% charged smartphone is used in direct sunlight. Figuratively speaking, in this case, 100% of the charge turns into 110%, and there is an excess of accumulated electricity, which can lead to a decrease in capacity.

Based on this, it is worth observing the temperature conditions of the gadget’s operation. Moreover, we are not talking about natural heating during active use - such an increase in temperature does not pose a danger to the battery

Charging time and charger. Each lithium source is equipped with a special controller, which should protect it from excess current. When a full charge is reached, the incoming current is switched off.

Errors and errors are possible in the operation of the controller, which lead to overcharging. Sometimes this is due to the use of non-original smartphone chargers. It is not recommended to leave a charging smartphone in the outlet for a long time after it has reached a full charge. You also need to use original chargers or those whose parameters are .

Lithium batteries need to be charged without waiting for the device to completely turn off, for example, to 10-15% of the remaining charge. They can be recharged whenever possible during the day, for example, from the USB port of a work computer or in a car. It is not necessary to achieve a full charge.

Storage. If the owner of a smartphone plans not to use the device for a long time, the recommended battery charge level in this case should be about 50%.

The number of charge cycles for lithium batteries is approximately 1200 times. Simple arithmetic suggests that the battery life will last for at least 3 years. By following the recommendations above, you can increase battery life.

In modern mobile phones, cameras and other devices, lithium-ion batteries are most often used, replacing alkaline and nickel-cadmium batteries, which they are superior to in many respects. Batteries with a lithium anode first appeared in the 70s of the previous century and immediately became very popular due to their high voltage and energy intensity.

History of appearance

The developments were short-lived, but at a practical level difficulties arose that were resolved only in the 90s of the last century. Due to the high activity of lithium, chemical processes occurred inside the element, which led to fire.

In the early 90s, a number of accidents occurred - telephone users, while talking, received severe burns as a result of spontaneous ignition of the elements, and then of the communication devices themselves. In this regard, the batteries were completely discontinued and previously released ones were returned from sale.

Modern lithium-ion batteries do not use pure metal, only its ionized compounds, as they are more stable. Unfortunately, scientists had to significantly reduce the battery's capabilities, but they managed to achieve the main thing - people no longer suffered from burns.

The crystal lattice of various carbon compounds was found to be suitable for the intercalation of lithium ions at the negative electrode. When charging, they move from the anode to the cathode, and when discharging, vice versa.

Operating principle and varieties

In every lithium-ion battery, the basis of the negative electrode is carbon-containing substances, the structure of which can be ordered or partially ordered. Depending on the material, the process of intercalation of Li into C varies. The positive electrode is mainly made of plated nickel or cobalt oxide.

Summarizing all reactions, they can be represented in the following equations:

1. LiCoO2 → Li1-xCoO2 + xLi+ + xe - for the cathode.
2. C + xLi+ + xe → CLix - for the anode.

The equations are presented for the case of discharge; during charging they flow in the opposite direction. Scientists are conducting research into new materials consisting of mixed phosphates and oxides. These materials are planned to be used for the cathode.

There are two types of Li-Ion batteries:

1. cylindrical;
2. prismatic.

The main difference is the location of the plates (in prismatic - on top of each other). The size of the lithium battery depends on this. As a rule, prismatic ones are denser and more compact.

In addition, there is a safety system inside - a mechanism that, when the temperature increases, increases the resistance, and when the pressure increases, it breaks the anode-cathode circuit. Thanks to the electronic board, a short circuit becomes impossible, since it controls the processes inside the battery.

Electrodes of opposite polarity are separated by a separator. The case must be sealed; leakage of electrolyte or ingress of water and oxygen will destroy both the battery and the electronic carrier device itself.

From different manufacturers, a lithium battery may look completely different; there is no uniform product shape. The ratio of the active masses of the anode to the cathode should be approximately 1:1, otherwise the formation of lithium metal is possible, which will lead to fire.

Advantages and disadvantages

Batteries have excellent parameters that vary among different manufacturers. The nominal voltage is 3.7−3.8 V with a maximum of 4.4 V. Energy density (one of the main indicators) is 110−230 Wh/kg.

Internal resistance ranges from 5 to 15 mOhm/1Ah. The service life by the number of cycles (discharge/charge) is 1000−5000 units. Fast charging time is 15−60 minutes. One of the most significant advantages is the slow self-discharge process (only 10-20% per year, of which 3-6% in the first month). The operating temperature range is 0 C - +65 C; at temperatures below zero, charging is impossible.

Charging occurs in several stages:

1. up to a certain point the maximum charging current flows;
2. when operating parameters are reached, the current gradually decreases to 3% of the maximum value.

During storage, periodic recharging is required approximately every 500 hours to compensate for self-discharge. When overcharging, lithium metal can be deposited, which, interacting with the electrolyte, forms oxygen. This increases the risk of depressurization due to increased internal pressure.

Frequent recharging greatly reduces battery life. In addition, the environment, temperature, current, etc. are affected.

The element has disadvantages, among which are the following:

terms of Use

It is best to store the battery under the following conditions: The charge should be at least 40%, and the temperature should not be very low or high. The best option is the range from 0C to +10C. Typically, about 4% of capacity is lost over 2 years, which is why it is not recommended to buy batteries from earlier manufacturing dates.

Scientists have invented a way to increase shelf life. An appropriate preservative is added to the electrolyte. However, such batteries should be “trained” in the form of 2-3 full discharge/charge cycles so that they can subsequently operate normally. Otherwise, a “memory effect” may occur and subsequent swelling of the entire structure. When used correctly and following all storage standards, the battery can last a long time, while its capacity will remain at a high level.

Reading “tips for operating” batteries on forums, you can’t help but think - either people skipped physics and chemistry at school, or they think that the rules for operating lead-acid and ion batteries are the same.
Let's start with the principles of operation of a Li-Ion battery. On the fingers, everything is extremely simple - there is a negative electrode (usually made of copper), there is a positive one (made of aluminum), between them there is a porous substance (separator) impregnated with electrolyte (it prevents the “unauthorized” transfer of lithium ions between the electrodes):

The principle of operation is based on the ability of lithium ions to be integrated into the crystal lattice of various materials - usually graphite or silicon oxide - with the formation of chemical bonds: accordingly, when charging, the ions are built into the crystal lattice, thereby accumulating a charge on one electrode, and when discharging, they respectively move back to another electrode , giving away the electron we need (who is interested in a more accurate explanation of the processes taking place - google intercalation). Water-containing solutions that do not contain a free proton and are stable over a wide voltage range are used as electrolytes. As you can see, in modern batteries everything is done quite safely - there is no lithium metal, there is nothing to explode, only ions run through the separator.
Now that everything has become more or less clear about the operating principle, let’s move on to the most common myths about Li-Ion batteries:

1. Myth one. The Li-Ion battery in the device cannot be discharged to zero percent.
   In fact, everything sounds correct and is consistent with physics - when discharged to ~2.5 V, the Li-Ion battery begins to degrade very quickly, and even one such discharge can significantly (up to 10%!) reduce its capacity. In addition, if the voltage is discharged to such a voltage with a standard charger, it will no longer be possible to charge it - if the battery cell voltage drops below ~3 V, the “smart” controller will turn it off as damaged, and if there are all such cells, the battery can be taken to the trash.
   But there is one very important thing that everyone forgets: in phones, tablets and other mobile devices, the operating voltage range on the battery is 3.5-4.2 V. When the voltage drops below 3.5 V, the indicator shows zero percent charge and the device turns off, but before " critical" 2.5 V is still very far away. This is confirmed by the fact that if you connect an LED to such a “discharged” battery, it can remain on for a long time (maybe someone remembers that they used to sell phones with flashlights that were turned on by a button regardless of the system. So the light there continued to burn even after discharge and turn off the phone). That is, as you can see, during normal use, discharge to 2.5 V does not occur, which means it is quite possible to discharge the battery to zero percent.
2. Myth two. If Li-Ion batteries are damaged, they explode.
   We all remember the “explosive” Samsung Galaxy Note 7. However, this is rather an exception to the rule - yes, lithium is a very active metal, and it is not difficult to explode it in the air (and it burns very brightly in water). However, modern batteries do not use lithium, but its ions, which are much less active. So for an explosion to occur, you need to try very hard - either physically damage the charging battery (cause a short circuit), or charge it with a very high voltage (then it will be damaged, but most likely the controller will simply burn out itself and will not allow the battery to charge). Therefore, if you suddenly have a damaged or smoking battery in your hands, don’t throw it on the table and run away from the room shouting “we’re all going to die” - just put it in a metal container and take it out to the balcony (so as not to breathe in the chemicals) - the battery will smolder for some time and then go out. The main thing is not to fill it with water, the ions are of course less active than lithium, but still some amount of hydrogen will also be released when reacting with water (and it likes to explode).
3. Myth three. When a Li-Ion battery reaches 300 (500/700/1000/100500) cycles, it becomes unsafe and needs to be replaced urgently.
   A myth, fortunately, that circulates less and less on forums and has no physical or chemical explanation at all. Yes, during operation, the electrodes oxidize and corrode, which reduces the battery capacity, but this does not threaten you with anything other than shorter battery life and unstable behavior at 10-20% charge.
4. Myth four. Li-Ion batteries cannot be used in the cold.
   This is more of a recommendation than a prohibition. Many manufacturers prohibit the use of phones at sub-zero temperatures, and many have experienced rapid discharge and even shutdown of phones in the cold. The explanation for this is very simple: the electrolyte is a water-containing gel, and everyone knows what happens to water at subzero temperatures (yes, it freezes, if anything), thereby rendering some area of ​​the battery unusable. This leads to a voltage drop, and the controller begins to consider this a discharge. This is not beneficial for the battery, but it is not fatal either (after heating, the capacity will return), so if you desperately need to use the phone in the cold (to use it - take it out of a warm pocket, check the time and put it back does not count) then it is better to charge it 100% and turn on any process that loads the processor - this will cool it down more slowly.
5. Myth fifth. A swollen Li-Ion battery is dangerous and should be thrown away immediately.
   This is not exactly a myth, but rather a precaution - a swollen battery can simply burst. From a chemical point of view, everything is simple: during the intercalation process, the electrodes and electrolyte decompose, resulting in the release of gas (it can also be released during recharging, but more on that below). But very little of it is released, and for the battery to appear swollen, several hundred (if not thousands) of recharge cycles must go through (unless, of course, it is defective). There are no problems getting rid of gas - just pierce the valve (in some batteries it opens itself when there is excess pressure) and bleed it off (I don’t recommend breathing with it), after which you can cover the hole with epoxy resin. Of course, this will not return the battery to its former capacity, but at least now it will definitely not burst.
6. Myth six. Overcharging is harmful to Li-Ion batteries.
   But this is no longer a myth, but a harsh reality - when recharging, there is a high chance that the battery will swell, burst and catch fire - believe me, there is little pleasure in being splashed with boiling electrolyte. Therefore, all batteries have controllers that simply prevent the battery from being charged above a certain voltage. But here you need to be extremely careful in choosing a battery - Chinese handicraft controllers can often malfunction, and I don’t think fireworks from your phone at 3 am will make you happy. Of course, the same problem exists in branded batteries, but firstly, this happens much less often there, and secondly, they will replace your entire phone under warranty. This myth usually gives rise to the following:
7. Myth seventh. When you reach 100%, you need to remove the phone from charging.
   From the sixth myth, this seems reasonable, but in reality there is no point in getting up in the middle of the night and unplugging the device: firstly, controller failures are extremely rare, and secondly, even when the indicator reaches 100%, the battery still charges for some time to the very, very maximum low currents, which adds another 1-3% capacity. So, in reality, you shouldn’t play it safe.
8. Myth eight. You can charge the device only with the original charger.
   The myth exists due to the poor quality of Chinese chargers - at a normal voltage of 5 +- 5% volts they can produce both 6 and 7 - the controller, of course, will smooth out this voltage for some time, but in the future it will, at best, lead to to the controller burning out, at worst - to an explosion and (or) failure of the motherboard. The opposite also happens - under load, the Chinese charger produces 3-4 volts: this will lead to the battery not being able to charge completely.

The charging and discharging processes of any battery occur in the form of a chemical reaction. However, charging lithium-ion batteries is an exception to the rule. Scientific research shows the energy of such batteries as the chaotic movement of ions. The statements of pundits deserve attention. If the science is to charge lithium-ion batteries correctly, then these devices should last forever.

Scientists see evidence of loss of useful battery capacity, confirmed by practice, in ions blocked by so-called traps.

Therefore, as is the case with other similar systems, lithium-ion devices are not immune to defects during their use in practice.

Chargers for Li-ion designs have some similarities to devices designed for lead-acid systems.

But the main differences between such chargers are seen in the supply of increased voltages to the cells. In addition, there are tighter current tolerances, plus the elimination of intermittent or floating charging when the battery is fully charged.

If there is some flexibility in terms of connecting/disconnecting voltage, manufacturers of lithium-ion systems categorically reject this approach.

Li-ion batteries and the operating rules for these devices do not allow for the possibility of unlimited overcharging.

Therefore, there is no so-called “miracle” charger for lithium-ion batteries that can extend their service life for a long time.

It is impossible to obtain additional Li-ion capacity through pulse charging or other known tricks. Lithium-ion energy is a kind of “clean” system that accepts a strictly limited amount of energy.

Charging cobalt-blended batteries

Classic lithium-ion battery designs are equipped with cathodes whose structure is made up of materials:

• cobalt,
• nickel,
• manganese,
• aluminum.

All of them are usually charged at a voltage of up to 4.20V/I. The permissible deviation is no more than +/- 50 mV/I. But there are also certain types of nickel-based lithium-ion batteries that allow a charge voltage of up to 4.10V/I.

There are also developments of lithium-ion batteries, where the percentage of lithium has been increased. For them, the charge voltage can reach 4.30V/I and higher.

Well, increasing the voltage increases the capacity, but if the voltage goes beyond the specification, it can lead to destruction of the battery structure.

Therefore, for the most part, lithium-ion batteries are equipped with protective circuits, the purpose of which is to maintain the established standard.

Full or partial charge

However, practice shows: most powerful lithium-ion batteries can accept a higher voltage level, provided that it is supplied for a short time.

With this option, the charging efficiency is about 99%, and the cell remains cool during the entire charging time. True, some lithium-ion batteries still heat up by 4-5C when fully charged.

This may be due to protection or due to high internal resistance. For such batteries, the charge should be stopped when the temperature rises above 10ºC at a moderate charge rate.

Full charging of cobalt-blended systems occurs at a threshold voltage. In this case, the current drops by up to 3-5% of the nominal value.

The battery will show a full charge even when it reaches a certain capacity level that remains unchanged for a long time. The reason for this may be increased self-discharge of the battery.

Increasing charge current and charge saturation

It should be noted that increasing the charge current does not speed up the achievement of a full charge state. Lithium will reach peak voltage faster, but charging until the capacity is completely saturated takes longer. However, charging the battery at high current quickly increases the battery capacity to approximately 70%.

Lithium-ion batteries do not require a full charge, as is the case with lead-acid devices. Moreover, this charging option is undesirable for Li-ion. In fact, it is better to not fully charge the battery, because high voltage “stresses” the battery.

Selecting a lower voltage threshold or completely removing the saturation charge helps extend the life of the lithium-ion battery. True, this approach is accompanied by a decrease in the battery energy release time.

It should be noted here: household chargers, as a rule, operate at maximum power and do not support adjustment of the charging current (voltage).

Manufacturers of consumer lithium-ion battery chargers consider long battery life to be less important than the cost of circuit complexity.

Li-ion battery chargers

Some cheap household chargers often work using a simplified method. Charge a lithium-ion battery in one hour or less, without going to saturation charge.

The ready indicator on such devices lights up when the battery reaches the voltage threshold in the first stage. The state of charge is about 85%, which often satisfies many users.

Professional chargers (expensive) are distinguished by the fact that they set the charging voltage threshold lower, thereby extending the life of the lithium-ion battery.

The table shows the calculated power when charging with such devices at different voltage thresholds, with and without saturation charge:

As soon as the lithium-ion battery begins to charge, there is a rapid increase in voltage. This behavior is comparable to lifting a load with a rubber band when there is a lag effect.

Capacity will eventually be gained when the battery is fully charged. This charge characteristic is typical for all batteries.

The higher the charging current, the brighter the rubber band effect. Low temperature or the presence of a cell with high internal resistance only enhances the effect.

Assessing the state of charge by reading the voltage of a charged battery is impractical. Measuring the open circuit (idle) voltage after the battery has been sitting for several hours is the best evaluation indicator.

As with other batteries, temperature affects idle speed in the same way it affects the active material of a lithium-ion battery. , laptops and other devices is estimated by counting coulombs.

Lithium-ion battery: saturation threshold

A lithium-ion battery cannot absorb excess charge. Therefore, when the battery is completely saturated, the charging current must be removed immediately.

A constant current charge can lead to metallization of lithium elements, which violates the principle of ensuring the safe operation of such batteries.

To minimize the formation of defects, you should disconnect the lithium-ion battery as quickly as possible when it reaches peak charge.

As soon as the charge stops, the voltage of the lithium-ion battery begins to drop. The effect of reducing physical stress appears.

For some time, the open circuit voltage will be distributed between unevenly charged cells with a voltage of 3.70 V and 3.90 V.

Here, the process also attracts attention when a lithium-ion battery, which has received a fully saturated charge, begins to charge the neighboring one (if one is included in the circuit), which has not received a saturation charge.

When lithium-ion batteries need to be constantly kept on the charger in order to ensure their readiness, you should rely on chargers that have a short-term compensation charge function.

The flash charger turns on when the open circuit voltage drops to 4.05 V/I and turns off when the voltage reaches 4.20 V/I.

Chargers designed for hot-ready or standby operation often allow the battery voltage to drop to 4.00V/I and will only charge Li-Ion batteries to 4.05V/I rather than reaching the full 4.20V/I level.

This technique reduces physical voltage, which is inherently associated with technical voltage, and helps extend battery life.

Charging cobalt-free batteries

Traditional batteries have a nominal cell voltage of 3.60 volts. However, for devices that do not contain cobalt, the rating is different.

Thus, lithium phosphate batteries have a nominal value of 3.20 volts (charging voltage 3.65V). And new lithium titanate batteries (made in Russia) have a nominal cell voltage of 2.40V (charger voltage 2.85).

Traditional chargers are not suitable for such batteries, as they overload the battery with the risk of explosion. Conversely, a charging system for cobalt-free batteries will not provide sufficient charge to a traditional 3.60V lithium-ion battery.

Exceeded charge of lithium-ion battery

The lithium-ion battery operates safely within specified operating voltages. However, battery performance becomes unstable if it is charged beyond operating limits.

Long-term charging of a lithium-ion battery with a voltage above 4.30V, designed for an operating rating of 4.20V, is fraught with lithium metalization of the anode.

The cathode material, in turn, acquires the properties of an oxidizing agent, loses its stability, and releases carbon dioxide.

The pressure of the battery cell increases and if charging continues, the internal protection device will operate at a pressure between 1000 kPa and 3180 kPa.

If the pressure rise continues after this, the protective membrane opens at a pressure level of 3.450 kPa. In this state, the lithium-ion battery cell is on the verge of exploding and eventually does just that.

Triggering of the protection inside a lithium-ion battery is associated with an increase in the temperature of the internal contents. A fully charged battery has a higher internal temperature than a partially charged one.

Therefore, lithium-ion batteries appear to be safer when charged at a low level. That is why the authorities of some countries require the use of Li-ion batteries in aircraft that are saturated with energy no more than 30% of their full capacity.

The internal battery temperature threshold at full load is:

• 130-150°C (for lithium-cobalt);
• 170-180°C (for nickel-manganese-cobalt);
• 230-250°C (for lithium manganese).

It should be noted: lithium phosphate batteries have better temperature stability than lithium manganese batteries. Lithium-ion batteries are not the only ones that pose a danger in energy overload conditions.

For example, lead-nickel batteries are also prone to melting with subsequent fire if energy saturation is carried out in violation of the passport regime.

Therefore, using chargers that are perfectly matched to the battery is of paramount importance for all lithium-ion batteries.

Some conclusions from the analysis

Charging lithium-ion batteries has a simplified procedure compared to nickel systems. The charging circuit is straightforward, with voltage and current limits.

This circuit is much simpler than a circuit that analyzes complex voltage signatures that change as the battery is used.

The energy saturation process of lithium-ion batteries allows for interruptions; these batteries do not need to be fully saturated, as is the case with lead-acid batteries.

The properties of lithium-ion batteries promise advantages in the operation of renewable energy sources (solar panels and wind turbines). As a rule, a wind generator rarely provides a full battery charge.

For lithium-ion, the lack of steady-state charging requirements simplifies the charge controller design. A lithium-ion battery does not require a controller to equalize voltage and current, as is required by lead-acid batteries.

All household and most industrial lithium-ion chargers fully charge the battery. However, existing lithium-ion battery charging devices generally do not provide voltage regulation at the end of the cycle.

Which is widely used in modern consumer electronics and finds its application as an energy source in electric vehicles and energy storage devices in energy systems. This is the most popular type of battery in devices such as cell phones, laptops, electric vehicles, digital cameras and camcorders. The first lithium-ion battery was released by Sony in 1991.

Characteristics

Depending on the electro-chemical circuit, lithium-ion batteries show the following characteristics:

• The voltage of a single element is 3.6 V.
• Maximum voltage 4.2 V, minimum 2.5–3.0 V. Charge devices support voltage in the range 4.05–4.2 V
• Energy density: 110 … 230 W*h/kg
• Internal resistance: 5 ... 15 mOhm/1Ah
• Number of charge/discharge cycles until 20% capacity is lost: 1000-5000
• Fast charge time: 15 min - 1 hour
• Self-discharge at room temperature: 3% per month
• Load current relative to capacity (C):
  • constant - up to 65C, pulsed - up to 500C
  • most acceptable: up to 1C
• Operating temperature range: −0 ... +60 °C (at subzero temperatures, charging batteries is not possible)

Device

A lithium-ion battery consists of electrodes (cathode material on aluminum foil and anode material on copper foil) separated by porous separators impregnated with electrolyte. The electrode package is placed in a sealed housing, the cathodes and anodes are connected to current collector terminals. The housing has a safety valve that relieves internal pressure in emergency situations and violation of operating conditions. Lithium-ion batteries vary in the type of cathode material used. The current carrier in a lithium-ion battery is a positively charged lithium ion, which has the ability to penetrate (intercalate) into the crystal lattice of other materials (for example, into graphite, metal oxides and salts) to form a chemical bond, for example: into graphite with the formation of LiC6, oxides (LiMO 2) and salts (LiM R O N) of metals. Initially, lithium metal was used as negative plates, then coal coke. Later, graphite began to be used. Until recently, lithium oxides with cobalt or manganese were used as positive plates, but they are increasingly being replaced by lithium ferrophosphate, which have proven to be safe, cheap and non-toxic and can be recycled in an environmentally friendly manner. Lithium-ion batteries are used in conjunction with a monitoring and control system - SKU or BMS (battery management system) and a special charge/discharge device. Currently, in the mass production of lithium-ion batteries, three classes of cathode materials are used: - lithium cobaltate LiCoO 2 and solid solutions based on its isostructural lithium nickelate - lithium manganese spinel LiMn 2 O 4 - lithium ferrophosphate LiFePO 4. Electrochemical circuits of lithium-ion batteries: lithium-cobalt LiCoO2 + 6xC → Li1-xCoO2 + xLi+C6 lithium-ferrophosphate LiFePO4 + 6xC → Li1-xFePO4 + xLi+C6

Due to low self-discharge and a large number of charge-discharge cycles, Li-ion batteries are most preferable for use in alternative energy. Moreover, in addition to the BMS system (SKU), they are equipped with inverters (voltage converters).

Advantages

• High energy density.
• Low self-discharge.
• No memory effect.
• No maintenance required.

Flaws

First generation Li-ion batteries were subject to explosive effects. This was explained by the fact that they used a lithium metal anode, on which, during multiple charge/discharge cycles, spatial formations (dendrites) arose, leading to the short circuit of the electrodes and, as a result, fire or explosion. This problem was finally solved by replacing the anode material with graphite. Similar processes occurred on the cathodes of lithium-ion batteries based on cobalt oxide when operating conditions were violated (overcharging). Lithium ferrophosphate batteries are completely free of these disadvantages. In addition, all modern lithium-ion batteries have built-in electronic circuitry that prevents overcharging and overheating due to overcharging.

Li-ion batteries may have a shorter life cycle when uncontrolledly discharged compared to other types of batteries. When fully discharged, lithium-ion batteries lose the ability to charge when the charging voltage is connected. This problem can be solved by applying a higher voltage pulse, but this negatively affects the further performance of lithium-ion batteries. The maximum “life” of a Li-ion battery is achieved by limiting the charge from above at 95% and the discharge at 15–20%. This operating mode is supported by the BMS monitoring and control system (SKU), which is included with any lithium-ion battery.

Optimal storage conditions for Li-ion batteries are achieved when charged at a level of 40–70% of the battery capacity and at a temperature of about 5 °C. At the same time, low temperature is a more important factor for small losses of capacity during long-term storage. The average shelf life (service) of a lithium-ion battery is on average 36 months, although it can range from 24 to 60 months.

Loss of capacity during storage:

According to all current regulations for the storage and operation of lithium-ion batteries, to ensure long-term storage it is necessary to recharge them to 70% capacity once every 6–9 months.

See also

Notes

Literature

• Khrustalev D. A. Batteries. M: Izumrud, 2003.
• Yuri Filippovsky Mobile food. Part 2. (RU). ComputerLab (May 26, 2009). - Detailed article about Li-ion batteries. Retrieved May 26, 2009.

Links

• GOST 15596-82 Terms and definitions.
• GOST 61960-2007 Rechargeable batteries and lithium batteries
• Lithium-ion and lithium-polymer batteries. iXBT (2001)
• Domestic lithium-ion batteries