How to extend the life cycle of lithium-ion (Li-ion) batteries. Lithium-ion batteries. Device and types. Operation and Application

The first experiments to create lithium galvanic cells were recorded back in 1012. A truly working model was created in 1940, the first production copies (non-rechargeable!) appeared in the 70s, and the triumphant march of this type of battery began in the early 90s, when the Japanese company Sony was able to master their commercial production.

Currently, it is believed that this is one of the most promising areas for creating autonomous electrical sources energy despite their rather high (at current level) cost.

The main advantage of this type of battery is high energy density(about 100 W/hour per 1 kg of weight) and the ability to perform a large charging/discharging cycle.

The newly created batteries are also characterized by such an excellent indicator as low speed self-discharge (only from 3 to 5% in the first month, with a subsequent decrease in this indicator). This allows for

And that's not all - compared to the widespread Ni-Cd, new scheme with the same dimensions, it provides three times greater performance with virtually no negative memory effect.

Negative characteristics

lithium ion batteries.

First of all, the high cost, the need to keep the battery in a charged state and the so-called “aging effect”, which manifests itself even when the galvanic cell has not been in use. The last unpleasant property manifests itself in a constant decrease in capacity, which after two years can lead to complete failure of the product.

Lithium-ion batteries not as “picky” as their nickel-metal hydride counterparts, but still require some care. Sticking to five simple rules , you can not only extend life cycle lithium-ion batteries, but also increase the operating time of mobile devices without recharging.

Do not allow complete discharge. Lithium-ion batteries do not have the so-called memory effect, so they can and, moreover, need to be charged without waiting for them to discharge to zero. Many manufacturers calculate the life of a lithium-ion battery by the number of full discharge cycles (up to 0%). For quality batteries This 400-600 cycles. To extend the life of your lithium-ion battery, charge your phone more often. Optimally, as soon as the battery charge drops below 10-20 percent, you can put the phone on charge. This will increase the number of discharge cycles to 1000-1100 .
Experts describe this process with such an indicator as Depth Of Discharge. If your phone is discharged to 20%, then the Depth of Discharge is 80%. The table below shows the dependence of the number of discharge cycles of a lithium-ion battery on the Depth of Discharge:

Discharge once every 3 months. Fully charging for a long time is just as harmful to lithium-ion batteries as constantly discharging to zero.
Due to the extremely unstable charging process (we often charge the phone as necessary, and wherever possible, from USB, from an outlet, from external battery etc.) experts recommend completely discharging the battery once every 3 months and then charging it to 100% and keeping it charged for 8-12 hours. This helps reset the so-called high and low battery flags. You can read more about this.

Store partially charged. The optimal condition for long-term storage of a lithium-ion battery is between 30 and 50 percent charge at 15°C. If you leave the battery fully charged, its capacity will decrease significantly over time. And here is the battery that for a long time it was collecting dust on the shelf, discharged to zero, most likely no longer alive - it’s time to send it for recycling.
The table below shows how much capacity remains in a lithium-ion battery depending on storage temperature and charge level when stored for 1 year.

Use original charger. Few people know that the charger in most cases is built directly inside mobile devices, and the external network adapter It only lowers the voltage and rectifies the current of the household electrical network, that is, it does not directly affect the battery. Some gadgets, such as digital cameras, do not have a built-in charger, and therefore their lithium-ion batteries are inserted into an external “charger”. This is where using an external charger of questionable quality instead of the original one can negatively affect the performance of the battery.

Avoid overheating. Well, the worst enemy of lithium-ion batteries is high temperature - they cannot tolerate overheating at all. Therefore, do not allow mobile devices direct sun rays, and do not leave them in close proximity to heat sources such as electric heaters. Maximum permissible temperatures, in which it is possible to use lithium-ion batteries: from –40°C to +50°C

Also, you can look

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 show 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 with 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 designs lithium ion batteries 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 take more high level voltage 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, they heat up by 4-5C when they reach full charge.

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 support mandatory fully charged, as is the case with acid-lead appliances. Moreover, this charging option is undesirable for Li-ion. In fact, it is better to not fully charge the battery, because high voltage“strains” 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's worth noting here: household chargers typically run on maximum power and do not support charging current (voltage) adjustment.

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 charge current, the brighter the effect rubber band. 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.

Tension for a while idle speed 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. 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.

Battery internal temperature threshold at fully loaded 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 benefits 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 devices Charging lithium-ion batteries generally do not provide voltage regulation at the end of the cycle.

Lithium batteries

Lithium or lithium-ion (Li-ion) batteries are mainly found in cell phones, laptops, and video cameras. The products are expensive, and so are the batteries, so you need to handle them even more competently than any other batteries. So what is the power of Li-Ion? There are probably even more rumors and myths here. Firstly, it begins to appear by itself, if only because sellers of equipment with Li- ion battery They don’t give us any special instructions, saying that the battery is “smart” and will do everything as it should. But not herself. After all, how many cases are there when owners of new laptops rendered the battery unusable within a month and then paid good prices for new battery. Of course, lithium batteries are expensive because they are packed with electronics, but, unfortunately, they do not save you from being a fool.

Overdischarge

As with nickel batteries, lithium batteries are also very susceptible to overcharging and overdischarging. But since these batteries are used in smart devices and come with their own chargers, their electronics do not allow overcharging - i.e. you don't have to be afraid of him. But overdischarge is more difficult to control, which is why it is the most typical cause premature failure of the battery. Of course, in expensive and complex devices, such as laptops, shutdown occurs before the voltage drops to a critical value. But precedents indicate that this emergency shutdown is better viewed as emergency measure, to which, if possible, it is better not to reach. This is the most important rule - avoid complete discharge, since low voltage may disable the emergency protection circuit. It happens that people “kill” their batteries when they get carried away by training. Training is a good thing, but for lithium batteries 2-3 full cycles are enough.

Lithium batteries have no memory effect, so they can be charged whenever you want, so it is better not to completely discharge the batteries after training. The recommended lower threshold is 5-10%. The critical lower threshold is 3%.

Many incomplete cycles or one complete

Lithium batteries have a service life of approximately 300 cycles. A full cycle is considered to be a cycle of full charge and complete (i.e. up to approximately 3% capacity) discharge, or vice versa. If you discharge the battery to 50% and then charge it, it will be 1/2 cycle, if to 75% and charge it will be 1/4 cycle, etc. So, for phones and laptops, the difference in benefits between full and incomplete cycles is different. It is persistently stated on the Internet that a lot of people charged their phones when they were not fully discharged (i.e., they recharged the phone every day) and eventually ruined them. At the same time, for laptops it is reliably known that full cycles wear out the battery faster than incomplete ones. The situation becomes clearer upon closer examination. Li-ion devices batteries (see additional materials). It turns out that a lot depends on the controller. It is he who controls the charge current, monitors the condition of the battery, etc. So, in laptops the controller is located in the battery itself and is adjusted system utilities, for example calibration. In cell phones, the controller is located in the phone itself and cannot be easily adjusted. Although there is no memory effect in lithium batteries, there is a so-called “digital memory” effect. The fact is that the charge-discharge control electronics located in the battery itself operate independently of the device using the battery. Internal electronics monitor the voltage level of the element, interrupt the charge when the set maximum value is reached (taking into account the change in voltage due to the charging current and battery temperature), interrupt the discharge when a critical value is reached and report this “upstream” (a large range of products are produced for these purposes specialized chips). The battery monitoring system “at the top” calculates the charge level based on information about the moments of switching off the charge and discharge from the battery and the readings of the current measurement system. But if the operating conditions are such that complete discharge before hardware shutdown or full charging does not occur, these calculations after several cycles may not be entirely correct - the battery capacity decreases over time, and the readings of the current meter may not always correspond to reality. Typically, deviations do not exceed one percent for each cycle, unless serious changes occur during operation, associated, for example, with the failure of one of the battery cells. The monitoring system has the ability to “learn”, that is, recalculate the value of the full capacity of the battery, but for this it is necessary to perform at least one full charge-discharge cycle before the hardware circuits of the battery itself are triggered. So it turns out that with very frequent cycles the controller gets lost, and, therefore, incorrectly calculates the battery charge and carries out incorrect charging, causing the battery to deteriorate. Unlike a laptop, a phone cannot be recalibrated. All that remains in in this case, this is to do a couple of full cycles to get the controller in order. I recommend, ideally, combining full and incomplete cycles, adhering to the “golden mean” principle. Personally, I did this with my cell phone - as a result, after 2 years of operation, the drop in capacity was no more than 40%, which is the norm. In part, time is also not kind to lithium batteries - they wear out over time, regardless of use; Their lifespan is short and it is reasonable to change batteries every 2-3 years.

Storage

When the battery is not in use, it is recommended to store it at 40% capacity in a cool place. The lower temperature limit for storage and operation is 00 C. In general, lithium batteries like to be charged, i.e. They are better to store and keep in a charged state, unlike nickel ones. But during long-term storage maximum charge still wears out the battery more, so the optimal state is considered to be 40% charge.

Battery resuscitation

In general, if the battery is dead, it is better to buy a new one; this is the most logical option, although it is expensive. I have not seen any reliable recipes for resuscitating batteries. There are real legends here, especially about laptops, that people have revived their ruined laptop battery and everything is fine with them. One of them sounds like this: “You need to completely discharge the battery, leave the laptop for a week; then fully charge the battery and also leave it for a week; in two months the capacity should be restored.”

For cell phones: combine complete and incomplete cycles (in the “XZ” proportion).
For laptops: as few complete cycles as possible (after training).
For everyone: it is recommended to do 80% cycles; do not allow complete discharge (below 3%).

IN given time Li-ion batteries and Li-pol (lithium polymer) batteries are widely used.

The difference between them is the electrolyte. In the first option, helium is used as it, in the second - a polymer saturated with a solution containing lithium. Today, thanks to the popularity of cars with electric motors, there is an urgent question of finding the ideal type of li ion battery that is optimal for such vehicles.

It consists, like other batteries, of an anode (porous carbon) and a cathode (lithium), a separator separating them and a conductor - electrolyte. The discharge process is accompanied by the transition of “anode” ions to the cathode through a separator and electrolyte. Their direction is reversed during charging (picture below).

Ions circulate during the process of discharging and charging the cell between oppositely charged electrodes.

Ion batteries have a cathode made of different metals, which is their main difference. Manufacturers using for electrodes different materials, improve battery performance.

But it happens that an improvement in some characteristics leads to a sharp deterioration in others. For example, by optimizing the capacity needed to increase travel time, you can increase power, safety, and reduce the negative impact on the environment. At the same time, you can reduce the load current, increase the cost or size of the battery.

Get acquainted with the main parameters different types lithium batteries (lithium-manganese, lithium-cobalt, lithium-phosphate and nickel-manganese-cobalt) can be found in the table:

Rules for electric transport users

The capacity of such batteries practically does not decrease during long-term storage. Li-ion batteries are discharged by only 23% if stored at a temperature of 60 degrees for 15 years. It is thanks to these properties that they are widely used in electric transport technologies.

Lithium-ion batteries with a full-fledged system controls built into the housing.

For this reason, during operation, users forget about the basic rules that can extend their service life:

• The battery must be fully charged immediately after purchasing it in the store, since the electrodes are charged by 50% during the production process. Therefore, the available capacity will decrease, i.e. operating time if there is no initial charge;
• the battery should not be allowed to completely discharge in order to preserve its resource;
• The battery must be charged after each trip, even if there is still some charge left;
• do not heat the batteries because high temperatures contribute to the aging process. In order to make maximum use of the resource, it is necessary to carry out operation at optimal temperature, which is 20-25 degrees. Therefore, the battery cannot be stored near a heat source;
• In cold weather, it is recommended to wrap the battery in a plastic bag with a vacuum seal to store it at 3-4 degrees, i.e. in an unheated room. The charge must be at least 50% of the full charge;
• after the battery has been used at subzero temperatures, it cannot be charged without keeping it at room temperature for some time, i.e. it needs to be warmed up;
• The battery must be charged using the charger supplied in the kit.

There are several subtypes of PU of these batteries - lithium - LiFePO4 (iron - phosphate), using an iron phosphate cathode. Their characteristics allow us to talk about batteries as the pinnacle of technology used for the production of batteries.

Their main advantages are:

• the number of charge-discharge cycles, which reaches 5000 until the capacity decreases by 20%;
• long service life;
• no “memory effect”;
• wide temperature range with unchanged performance characteristics (300-700 degrees Celsius);
• chemical and thermal stability, increasing safety.

Most widely used batteries

Among the many, the most common are li ion batteries of size 18650, produced by five companies: LG, Sony, Panasonic, Samsung, Sanyo, whose factories are located in Japan, China, Malaysia and South Korea. It was planned that 18650 li ion batteries would be used in laptops. However, thanks to their successful format, they are used in radio-controlled models, electric cars, flashlights, etc.

Like any quality product, such batteries have many counterfeits, therefore, in order to extend the life of the device, you need to purchase only batteries from well-known brands.

Protected and unprotected lithium-ion batteries

It is also important for lithium batteries whether they are protected or not. The operating range of the former is 4.2-2.5V (used in devices designed to work with lithium-ion sources): LED lights, low-power household appliances, etc.

Power tools, bicycles with electric motors, laptops, video and photographic equipment use unprotected batteries controlled by a controller.

What you need to know about lithium-ion batteries?

First of all, the restrictions that must be observed during operation:

• recharge voltage (maximum) cannot be higher than 4.35V;
• its minimum value cannot fall below 2.3 V;
• The discharge current should not exceed more than twice the capacitance value. If the value of the latter is 2200 mAh, the maximum current value is 4400 mA.

Functions performed by the controller

Why do you need a li ion battery charge controller? It performs several functions:

• supplies a current that compensates for self-discharge. Its value is less than the maximum charge current, but greater than the self-discharge current;
• implements an efficient charge/discharge cycle algorithm for a specific battery;
• compensates for the difference in energy flows while simultaneously charging and providing energy to the consumer. For example, when charging and powering a laptop;
• Measures the temperature when overheating or hypothermia, preventing damage to the battery.

A li ion battery charge controller is manufactured either in the form of a microcircuit built into the battery or as a separate device.

To charge the batteries, it is better to use the standard charger for 18650 li-ion batteries supplied in the kit. Charger for lithium batteries 18650 usually has a charge level indicator. Most often this is an LED that shows when charging and its ending.

On more advanced devices, you can track on the display the time remaining until the end of the charge and the current voltage. For an 18650 battery with a capacity of 2200mA, the charging time is 2 hours.

But, it is important to know what current to charge a li ion battery 18650. It should be half the nominal capacity, i.e., if it is 2000 mAh, then the optimal current is 1A. By charging the battery with high current, its degradation quickly occurs. When using low current it will take more time.

Video: How to charge a Li battery ion charger with your own hands

Diagram of a device for charging batteries

It looks like this:

The circuit is distinguished by its reliability and repeatability, and the included parts are inexpensive and easily accessible. To increase the service life of the battery, proper charging of li-ion batteries is required: towards the end of charging, the voltage should decrease.

After its completion, i.e. When the current reaches zero, charging of the li-ion battery should stop. The circuit given above satisfies these requirements: a discharged battery connected to the charger (VD3 lights up) uses a current of 300 mA.

The ongoing process is indicated by the burning LED VD1. The current gradually decreasing to 30 mA indicates that the battery is charging. The end of the process is signaled by the lit LED VD2.

Used in the circuit operational amplifier LM358N (you can replace it with an analogue of KR1040UD1 or KR574UD2, which differs in the location of the pins), as well as transistor VT1 S8550 9 LEDs of yellow, red and green colors (1.5V).

Is it possible to revive a battery?

After a couple of years of active use, batteries catastrophically lose capacity, creating problems when using your favorite device. Is it possible and how to restore a li ion battery while the user is looking for a replacement?

Restoring a li ion battery is possible temporarily in several ways.

If the battery is swollen, i.e. no longer holds a charge, which means gases have accumulated inside.

Then proceed as follows:

• the battery case is carefully disconnected from the sensor;
• separate the electronic sensor;
• they find a cap with control electronics underneath and carefully pierce it with a needle;
• then, find a heavy flat object, larger in area than the area of ​​the battery, which will be used as a press (do not use a vice or similar devices);
• Place the battery on a horizontal plane and press down with a press, remembering that the battery can be damaged by applying excessive force. If it is not enough, the result may not be achieved. This is the most crucial moment;
• All that remains is to drop epoxy resin onto the hole and solder the sensor.

There are other ways, which you can read about on the Internet.

You can select a charger on the website http://18650.in.ua/chargers/.

Video: Li-ion batteries, tips for li-ion operation batteries