How to properly charge Li-ion batteries: tips. Using lithium-ion batteries

Lithium-ion and lithium-polymer batteries

Engineering thought is constantly evolving: it is stimulated by constantly emerging problems that require the development of new technologies to be solved. At one time, nickel-cadmium (NiCd) batteries were replaced by nickel-metal hydride (NiMH), and now lithium-ion (Li-ion) batteries are trying to take the place of lithium-ion (Li-ion) batteries. NiMH batteries have to some extent supplanted NiCd, but due to such undeniable advantages of the latter as the ability to deliver high current, low cost and long service life, they could not provide their full replacement. But what about lithium batteries? What are their features and how do Li-pol batteries differ from Li-ion? Let's try to understand this issue.

As a rule, when buying a mobile phone or laptop computer, all of us do not think about what kind of battery is inside and how these devices differ in general. And only then, having encountered in practice the consumer qualities of certain batteries, do we begin to analyze and choose. For those who are in a hurry and want to immediately get an answer to the question of which battery is optimal for a cell phone, I will answer briefly - Li-ion. The following information is intended for the curious.

First, a short excursion into history.

The first experiments on creating lithium batteries began in 1912, but it was only six decades later, in the early 70s, that they were first introduced into household devices. Moreover, let me emphasize, these were just batteries. Subsequent attempts to develop lithium batteries (rechargeable batteries) failed due to safety concerns. Lithium, the lightest of all metals, has the greatest electrochemical potential and provides the greatest energy density. Batteries using lithium metal electrodes offer both high voltage and excellent capacity. But as a result of numerous studies in the 80s, it was found that cyclic operation (charge - discharge) of lithium batteries leads to changes in the lithium electrode, as a result of which thermal stability decreases and there is a threat of the thermal state getting out of control. When this happens, the temperature of the element quickly approaches the melting point of lithium - and a violent reaction begins, igniting the gases released. For example, a large number of lithium mobile phone batteries shipped to Japan in 1991 were recalled after several fire incidents.

Because of lithium's inherent instability, researchers have turned their attention to non-metallic lithium batteries based on lithium ions. Having lost a little in energy density and taking some precautions when charging and discharging, they received safer so-called Li-ion batteries.

The energy density of Li-ion batteries is usually twice that of standard NiCd, and in the future, thanks to the use of new active materials, it is expected to increase it even further and achieve three times superiority over NiCd. In addition to the large capacity, Li-ion batteries behave similarly to NiCds when discharged (their discharge characteristics are similar in shape and differ only in voltage).

Today there are many varieties of Li-ion batteries, and you can talk for a long time about the advantages and disadvantages of one type or another, but it is impossible to distinguish them by appearance. Therefore, we will note only those advantages and disadvantages that are characteristic of all types of these devices, and consider the reasons that led to the birth of lithium-polymer batteries.

Main advantages.

• High energy density and, as a result, high capacity with the same dimensions compared to nickel-based batteries.
• Low self-discharge.
• High voltage per cell (3.6 V versus 1.2 V for NiCd and NiMH), which simplifies the design - often the battery consists of only one cell. Many manufacturers today use just such a single-cell battery in cell phones (remember Nokia). However, to provide the same power, a higher current must be supplied. And this requires ensuring low internal resistance of the element.
• Low maintenance (operating) costs result from the absence of memory effect, requiring periodic discharge cycles to restore capacity.

Flaws.

Li-ion battery manufacturing technology is constantly improving. It is updated approximately every six months, and it is difficult to understand how new batteries “behave” after long-term storage.

In a word, a Li-ion battery would be good for everyone if it were not for the problems with ensuring the safety of its operation and the high cost. Attempts to solve these problems led to the emergence of lithium-polymer (Li-pol or Li-polymer) batteries.

Their main difference from Li-ion is reflected in the name and lies in the type of electrolyte used. Initially, in the 70s, a dry solid polymer electrolyte was used, similar to plastic film and not conducting electricity, but allowing the exchange of ions (electrically charged atoms or groups of atoms). The polymer electrolyte effectively replaces the traditional porous separator impregnated with electrolyte.

This design simplifies the production process, is safer, and allows the production of thin, free-form batteries. In addition, the absence of liquid or gel electrolyte eliminates the possibility of ignition. The thickness of the element is about one millimeter, so equipment developers are free to choose the shape, shape and size, even including its implementation in fragments of clothing.

But so far, unfortunately, dry Li-polymer batteries have insufficient electrical conductivity at room temperature. Their internal resistance is too high and cannot provide the amount of current required for modern communications and power supply to the hard drives of laptop computers. At the same time, when heated to 60 °C or more, the electrical conductivity of Li-polymer increases to an acceptable level, but this is not suitable for mass use.

Researchers are continuing to develop Li-polymer batteries with a dry solid electrolyte that operates at room temperature. Such batteries are expected to become commercially available by 2005. They will be stable, allow 1000 full charge-discharge cycles and have a higher energy density than today's Li-ion batteries

Meanwhile, some types of Li-polymer batteries are now used as backup power supplies in hot climates. For example, some manufacturers specifically install heating elements that maintain a favorable temperature for the battery.

You may ask: how can this be? Li-polymer batteries are widely sold on the market, manufacturers equip phones and computers with them, but here we are saying that they are not yet ready for commercial use. It's very simple. In this case, we are talking about batteries not with dry solid electrolyte. In order to increase the electrical conductivity of small Li-polymer batteries, a certain amount of gel-like electrolyte is added to them. And most Li-polymer batteries used for cell phones today are actually hybrids because they contain a gel-like electrolyte. It would be more correct to call them lithium-ion polymer. But most manufacturers simply label them as Li-polymer for advertising purposes. Let us dwell in more detail on this type of lithium-polymer batteries, since at the moment they are of the greatest interest.

So, what is the difference between a Li-ion and a Li-polymer battery with gel electrolyte added? Although the characteristics and efficiency of both systems are largely similar, the uniqueness of the Li-ion polymer (you can call it that) battery is that it still uses a solid electrolyte, replacing a porous separator. Gel electrolyte is added only to increase ionic conductivity.

Technical difficulties and delays in ramping up production have delayed the introduction of Li-ion polymer batteries. This is caused, according to some experts, by the desire of investors who have invested a lot of money in the development and mass production of Li-ion batteries to get their investments back. Therefore, they are in no hurry to switch to new technologies, although with mass production of Li-ion polymer batteries will be cheaper than lithium-ion ones.

And now about the features of operating Li-ion and Li-polymer batteries.

Their main characteristics are very similar. The charging of Li-ion batteries is described in sufficient detail in the article. In addition, I will only give a graph (Fig. 1) from, illustrating the stages of charge, and small explanations to it.

The charging time for all Li-ion batteries with an initial charging current of 1C (numerically equal to the nominal value of the battery capacity) averages 3 hours. Full charge is achieved when the battery voltage is equal to the upper threshold and when the charging current is reduced to a level approximately equal to 3% of the initial value. The battery remains cold during charging. As can be seen from the graph, the charging process consists of two stages. In the first (a little over an hour), the voltage increases at an almost constant initial charge current of 1C until the upper voltage threshold is first reached. At this point, the battery is charged to approximately 70% of its capacity. At the beginning of the second stage, the voltage remains almost constant and the current decreases until it reaches the above 3%. After this, the charge stops completely.

If you need to keep the battery charged all the time, it is recommended to recharge after 500 hours, or 20 days. Usually it is carried out when the voltage at the battery terminals decreases to 4.05 V and stops when it reaches 4.2 V

A few words about the temperature range during charging. Most types of Li-ion batteries can be charged with a current of 1C at temperatures from 5 to 45 °C. At temperatures from 0 to 5 °C, it is recommended to charge with a current of 0.1 C. Charging at sub-zero temperatures is prohibited. The optimal temperature for charging is 15 to 25 °C.

The charging processes in Li-polymer batteries are almost identical to those described above, so the consumer has absolutely no need to know which of the two types of batteries he has in his hands. And all those chargers that he used for Li-ion batteries are suitable for Li-polymer.

And now about the discharge conditions. Typically, Li-ion batteries discharge to a value of 3.0 V per cell, although for some varieties the lower threshold is 2.5 V. Manufacturers of battery-powered equipment typically design devices with a shutdown threshold of 3.0 V (for all occasions). What does this mean? The voltage on the battery gradually decreases when the phone is turned on, and as soon as it reaches 3.0 V, the device will warn you and turn off. However, this does not mean that it has stopped consuming energy from the battery. Energy, albeit small, is required to detect when the phone's power key is pressed and some other functions. In addition, energy is consumed by its own internal control and protection circuit, and self-discharge, although small, is still typical even for lithium-based batteries. As a result, if lithium batteries are left for a long period of time without recharging, the voltage on them will drop below 2.5 V, which is very bad. In this case, the internal control and protection circuit may be disabled, and not all chargers will be able to charge such batteries. In addition, deep discharge negatively affects the internal structure of the battery itself. A completely discharged battery must be charged at the first stage with a current of only 0.1C. In short, batteries like to be in a charged state rather than in a discharged state.

A few words about temperature conditions during discharge (read during operation).

In general, Li-ion batteries perform best at room temperature. Operating in warmer conditions will seriously reduce their lifespan. Although, for example, a lead-acid battery has the highest capacity at temperatures above 30 °C, long-term operation in such conditions shortens the life of the battery. Likewise, Li-ion performs better at high temperatures, which initially counteract the increase in battery internal resistance that results from aging. But the increased energy output is short-lived, since increasing temperature, in turn, promotes accelerated aging, accompanied by a further increase in internal resistance.

The only exceptions at the moment are lithium polymer batteries with dry solid polymer electrolyte. They require a vital temperature of 60 °C to 100 °C. And such batteries have found their niche in the market for backup sources in hot climates. They are placed in a thermally insulated housing with built-in heating elements powered from an external network. Li-ion polymer batteries as a backup are considered to be superior in capacity and durability to VRLA batteries, especially in field conditions where temperature control is not possible. But their high price remains a limiting factor.

At low temperatures, the efficiency of batteries in all electrochemical systems drops sharply. While NiMH, SLA and Li-ion batteries stop functioning at -20°C, NiCd batteries continue to function down to -40°C. Let me just note that again we are talking only about batteries of wide use.

It is important to remember that although a battery can operate in low temperatures, this does not mean that it can also be charged in these conditions. The charge susceptibility of most batteries at very low temperatures is extremely limited, and the charge current in these cases should be reduced to 0.1C.

In conclusion, I would like to note that you can ask questions and discuss problems related to Li-ion, Li-polymer, as well as other types of batteries, on the forum in the accessories subforum.

When writing this article, materials were used [—Batteries for mobile devices and laptop computers. Battery analyzers.

Today, lithium-ion batteries are most often used in various fields. They are especially widely used in mobile electronics (PDAs, mobile phones, laptops and much more), electric vehicles and so on. This is due to their advantages over the previously widely used nickel-cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH) batteries. And if the latter have come close to their theoretical limit, then lithium-ion battery technology is at the beginning of its journey.

Device

In lithium-ion batteries, aluminum serves as the negative electrode (cathode), and copper acts as the positive electrode (anode). Electrodes can be made in different shapes, however, as a rule, they are foil in the shape of an oblong package or a cylinder.

• The anode material on the copper foil and the cathode material on the aluminum foil are separated by a porous separator, which is impregnated with an electrolyte.
• The electrode package is installed in a sealed housing, and the anodes and cathodes are connected to current collector terminals
• There may be special devices under the battery cover. One device responds by increasing resistance to a positive temperature coefficient. The second device breaks the electrical connection between the positive terminal and the cathode when the gas pressure in the battery increases above the permissible limit. In some cases, the housing is equipped with a safety valve that relieves internal pressure in the event of violations of operating conditions or emergency situations.
• To increase operating safety, a number of batteries also use external electronic protection. It prevents the possibility of excessive heating, short circuiting and overcharging of the battery.
• Structurally, batteries are produced in prismatic and cylindrical versions. A rolled-up package of separator and electrodes in cylindrical batteries is placed in an aluminum or steel case, to which the negative electrode is connected. The positive pole of the battery is brought out through the insulator to the cover. Prismatic batteries are created by stacking rectangular plates on top of each other.

These types of lithium-ion batteries allow for tighter packaging, but they are more difficult to maintain compressive forces on the electrodes than cylindrical batteries. A number of prismatic batteries use a roll assembly of a package of electrodes twisted into an elliptical spiral.

Most batteries are produced in prismatic versions, since their main purpose is to ensure the operation of laptops and mobile phones. The design of Li-ion batteries is completely sealed. This requirement is dictated by the inadmissibility of leakage of liquid electrolyte. If water vapor or oxygen gets inside, a reaction occurs with the electrolyte and electrode materials, which leads to complete failure of the battery.

Operating principle

• Lithium-ion batteries have two electrodes in the form of an anode and a cathode, with an electrolyte between them. At the anode, when a battery is connected in a closed circuit, a chemical reaction is formed, which leads to the formation of free electrons.
• These electrons tend to get to the cathode, where their concentration is lower. However, what keeps them from going directly to the cathode from the anode is the electrolyte, which is located between the electrodes. The only way left is through the circuit where the battery is closed. In this case, electrons, moving along the specified circuit, supply the device with energy.
• The positively charged lithium ions, which were left behind by the runaway electrons, are at the same time directed through the electrolyte to the cathode in order to satisfy the demand for electrons on the cathode side.
• After all the electrons move to the cathode, the “death” of the battery occurs. But the lithium-ion battery is rechargeable, meaning the process can be reversed.

Using a charger, you can introduce energy into the circuit, thereby starting the reaction in the opposite direction. The result will be an accumulation of electrons on the anode. Once a battery has been recharged, it will remain so for the most part until it is activated. However, over time, the battery will lose some of its charge even in standby mode.

• Battery capacity refers to the number of lithium ions that can embed themselves in the craters and tiny pores of the anode or cathode. Over time, after numerous recharges, the cathode and anode degrade. As a result, the number of ions they can accommodate decreases. In this case, the battery can no longer hold the same amount of charge. Eventually, it completely loses its functions.

Lithium-ion batteries are designed in such a way that their charging must be constantly monitored. For this purpose, a special board is installed in the case, it is called a charge controller. The chip on the board controls the battery charging process.

Standard battery charging looks like this:

• At the beginning of the charging process, the controller supplies a current of 10% of the rated current. At the moment the voltage rises to 2.8 V.
• Then the charge current increases to the nominal one. During this period, the DC voltage rises to 4.2 V.
• At the end of the charging process, the current drops at a constant voltage of 4.2 V until the battery is 100% charged.

The staging may differ due to the use of different controllers, which leads to different charging speeds and, accordingly, the total cost of the battery. Lithium-ion batteries can be without protection, that is, the controller is located in the charger, or with built-in protection, that is, the controller is located inside the battery. There may be devices where the protection board is built directly into the battery.

Varieties and applications

There are two form factors of lithium-ion batteries:

1. Cylindrical lithium-ion batteries.
2. Tablet lithium-ion batteries.

The different subtypes of the electrochemical lithium-ion system are named according to the type of active substance used. What all of these lithium-ion batteries have in common is that they are all sealed, maintenance-free batteries.

There are 6 most common types of lithium-ion batteries:

1. Lithium cobalt battery . It is a popular solution for digital cameras, laptops and mobile phones due to its high specific energy consumption. The battery consists of a cobalt oxide cathode and a graphite anode. Disadvantages of lithium-cobalt batteries: limited load capacity, poor thermal stability and relatively short service life.

Applications ; mobile electronics.

1. Lithium manganese battery . The crystalline lithium manganese spinel cathode features a three-dimensional framework structure. Spinel provides low resistance, but has a more moderate energy density than cobalt.

Areas of application; electric power units, medical equipment, power tools.

1. Lithium Nickel Manganese Cobalt Oxide Battery . The battery cathode combines cobalt, manganese and nickel. Nickel is famous for its high specific energy intensity, but low stability. Manganese provides low internal resistance but results in low energy density. The combination of metals allows you to compensate for their disadvantages and use their strengths.

Areas of application; for private and industrial use (security systems, solar power plants, emergency lighting, telecommunications, electric vehicles, electric bicycles and so on).

1. Lithium iron phosphate battery . Its main advantages are: long service life, high current ratings, resistance to misuse, increased safety and good thermal stability. However, this battery has a small capacity.

Areas of application: stationary and portable specialized devices where endurance and high load currents are required.

1. Lithium Nickel Cobalt Aluminum Oxide Battery . Its main advantages: high energy density and energy intensity, durability. However, its safety record and high cost limit its use.

Areas of application; electric powertrains, industrial and medical equipment.

1. Lithium titanate battery . Its main advantages: fast charging, long service life, wide temperature range, excellent performance and safety. This is the safest lithium-ion battery available.

However, it has a high cost and low specific energy intensity. Currently, developments are underway to reduce the cost of production and increase specific energy intensity.

Areas of application; street, electric power units of cars (Honda Fit-EV, Mitsubishi i-MiEV), UPS.

Typical characteristics

In general, lithium-ion batteries have the following typical characteristics:

• The minimum voltage is not lower than 2.2-2.5V.
• The maximum voltage is not higher than 4.25-4.35V.
• Charging time: 2-4 hours.
• Self-discharge at room temperature is about 7% per year.
• Operating temperature range from −20 °C to +60 °C.
• The number of charge/discharge cycles until a loss of 20% of capacity is achieved is 500-1000.

Advantages and disadvantages

The advantages include:

• High energy density compared to alkaline batteries using nickel.
• The voltage of one battery cell is quite high.
• There is no “memory effect”, which ensures simple operation.
• A significant number of charge-discharge cycles.
• Long service life.
• Wide temperature range for consistent performance.
• Relative environmental safety.

Among the disadvantages are:

• Moderate discharge current.
• Relatively fast aging.
• Relatively high cost.
• Impossibility of working without a built-in controller.
• Possibility of spontaneous combustion under high loads and too deep discharge.
• The design requires significant improvements, because it is not perfected.

Greetings, my dear friends and admirers, readers of this blog. Instead of another lesson, it would be more correct to say articles in photo school piggy bank, I decided to write an article about a topic that is sore and important to everyone.

I think many, including you, my dear readers, will find it both interesting and useful to know what such fundamental things are lithium ion batteries, what are their limiting characteristics, how should they be used, what can be obtained with proper use, and of course, what should be the care for long battery life. So go ahead.

Why? - you ask me, I actually started writing on this topic. Well, a battery and a battery and what about it. So? But no. Li-ion battery, this is essentially a fuel tank for many of our favorite devices, or devices in common parlance. So what? - you tell me, - what difference does it make to us? And the difference is big and important for you. The idea to write this article came after the photography school students and I attended. The weather conditions are quite ordinary, about -7 -10 Celsius, sunny, light breeze, clear. Generally pleasant weather for the inquisitive eye of an amateur photographer. However, many students became worried: Isn’t this dangerous for the camera? Won't she freeze? What happens if it freezes? (I will write a separate note about the temperature conditions of the camera) What will happen to the camera battery? We heard that the camera battery is very sensitive to the cold and can fail, is this true? True, but not all and not entirely. Let's figure it out.

Our cameras contain lithium-ion batteries. What would that mean? Here's what. Li-ion batteries have significantly better usage parameters compared to other types of batteries. I won’t go into details, but nowadays, most manufacturers of consumer electronics are trying to equip their products with Li-ion batteries, since they are simpler and cheaper to produce and are less harmful to the environment.

Primary cells (“batteries”) with a lithium anode appeared in the early 70s of the 20th century and quickly found application due to their high specific energy and other advantages. Thus, a long-standing desire was realized to create a chemical current source with the most active reducing agent - an alkali metal, which made it possible to sharply increase both the operating voltage of the battery and its specific energy. While the development of primary cells with a lithium anode was crowned with relatively quick success and such elements firmly took their place as power sources for portable equipment, the creation of lithium batteries encountered fundamental difficulties, which took more than 20 years to overcome.

After many tests during the 1980s, it turned out that the problem with lithium batteries revolved around the lithium electrodes. More precisely, around the activity of lithium: the processes that occurred during operation ultimately led to a violent reaction, called “ventilation with flame emission.” In 1991, a large number of lithium batteries, which were first used as a power source for mobile phones, were recalled by manufacturers. The reason was that during a conversation, when the current consumption was at its maximum, a flame erupted from the battery, burning the face of the mobile phone user.

Due to the inherent instability of lithium metal, especially during charging, research has moved towards creating a battery without the use of Li, but using its ions. Although lithium-ion batteries provide slightly lower energy density than lithium batteries, Li-ion batteries are safe when properly charged and discharged.

If further, someone is interested in the part about what chemical processes were and are in lithium-ion batteries, and how these same processes were tamed, then go to Google. I’m not strong enough in chemistry and physics to write an article that would make me fall asleep while reading it.

Modern Li-ion batteries have high specific characteristics: 100-180 Wh/kg and 250-400 Wh/l. Operating voltage: 3.5-3.7 V.

If just a few years ago, manufacturing developers considered the maximum achievable capacity of Li-ion batteries to be no more than several ampere-hours (remember the school physics course), now most of the reasons limiting the increase in capacity have been overcome and many manufacturers began to produce batteries with a capacity of hundreds of amperes -hours, or even thousands.

Modern small-sized batteries are operational at discharge currents of up to 2 C, powerful ones - up to 10-20 C. Operating temperature range: from -20 to +60 °C. However, many manufacturers have already developed batteries that operate at -40 °C. It is possible to expand the temperature range to higher temperatures.

The self-discharge of Li-ion batteries is 4-6% in the first month, then it is significantly less: in 12 months the batteries lose 10-20% of their stored capacity. The capacity loss of Li-ion batteries is several times less than that of nickel-cadmium (Ni-Cd) batteries, both at 20 °C and at 40 °C. Resource of lithium-ion batteries: 500-1000 charge-discharge cycles.

And here many will say: -Ahhh. This is why you can shoot with your camera in moderately cold temperatures. Yes, I will answer you. Plus, when the battery works, releasing energy, chemical reactions occur in it, the side effect of which is the release of thermal energy, which allows the battery to maintain its operating temperature range longer. In addition, when we take the camera out of the case on the street, it (the camera, the camera) also has a positive temperature, that is, we further increase the time resource during which we can shoot on the street at -7 ..-15 °C. Add to this the thermal heating of the camera processor during shooting, the heating of the matrix, even the warmth of the hands with which we hold the camera and transfer it to it, extends the thermal and time life of the camera at moderately low temperatures.

This concerns the use of batteries in work. Now let's look a little at the charge and storage side. Lithium-ion batteries do not require any special care. The basic rules for their operation can be found in the instructions for the phone/laptop/camera, and everything else is taken care of by the BMS circuit and the charge controller in the powered device. However, when buying, you can often hear the following statements from a salesperson or a fellow “guru”:

“...first charge - 12–15 hours...” or, alternatively, “...just leave the device connected all night...”;

“...you need to do 3-5 full cycles for the battery to gain capacity...”;

“...it is advisable to charge and discharge the battery completely...”;

“... so what if the battery is already a year old, it hasn’t been used; its service life depends solely on the number of charge-discharge cycles...”

Let's see how true the above is.

The first statement is simply meaningless - the control electronics will not allow the battery to be charged more than it should be.

Tip #2 is also untenable. After the first charge, lithium-ion batteries work with full efficiency, and at first they discharge faster simply because the owner of the device sets up and studies it, shows it to friends and acquaintances, etc. After a week or two, the gadget enters normal mode, which is natural , has a positive effect on autonomy. But one full charge before use is still advisable. This is not necessary for the battery, but so that the device can determine its real capacity and subsequently correctly display the remaining charge.

Recommendation No. 3 has “legs growing” even from the rules for operating nickel-cadmium batteries, which had to be completely discharged first, otherwise part of the capacity would be irreversibly lost. Their lithium-ion counterparts do not have a similar “memory effect”; moreover, deep discharge is contraindicated for them. With frequent use, this is not relevant, since the BMS system does not allow the battery to discharge completely, but if it remains in a discharged state for a month or more, the remaining charge will “leak away”, the protection circuit will block the charging process and turn off, after which charging will no longer be possible. Overcharging is also harmful, but most devices have already taken this into account and do not charge the battery to 100%.

There is also advice like “charge as you wish, but at least once a week (month) carry out a complete cycle.” This operating scheme is optimal for nickel-metal hydride batteries - they also have a memory effect, but much less than Ni-Cd, and restore capacity after 1-2 full cycles. For lithium-ion batteries this is only partially true; for example, it is recommended to do this after long-term storage.

From statement number 4, a seemingly logical conclusion follows: since the battery life is measured by the number of cycles, it means that it is better to use it to the maximum. This is a mistake. Full charge and discharge wear it out faster, while incomplete cycles, on the contrary, prolong life. In addition, lithium-ion batteries lose capacity even without use. Already after a year “on the shelf” their resource decreases by 5–10%, after 2 years – by 20–30%. Therefore, when purchasing a new portable device, pay attention to the release date of the power supply. It is also obvious that buying a battery for future use, even if it is difficult to find on sale, is useless.

It is very important to observe the operating temperature conditions of lithium-ion batteries. In frost below -20 °C they simply stop delivering current, and in heat above +45 °C although they function, such climatic conditions activate the aging process, significantly reducing the life of the battery. But you can charge it only at positive (Celsius) temperatures, otherwise there is a high risk of device failure. In general, the optimal operating temperature of lithium-ion batteries is +20 °C.

Lithium-ion batteries are constantly being improved, and manufacturers are actively experimenting with electrode and electrolyte materials. In 1994, batteries with lithium-manganese cathodes appeared, and in 1996 - with lithium-iron-phosphate cathodes. They are much more stable and can easily withstand high discharge currents, so they are used in power tools and electric vehicles. Since 2003, batteries have been produced that use a complex cathode composition (LiNiMnCoO2) and have the best combination of characteristics among all listed. But no one has yet been able to surpass lithium-cobalt specimens in terms of specific capacity and price, and the advantages of the new types are not in demand in mobile phones and laptops that consume relatively little current.

If you have temporarily put your device aside, but want to keep its battery in working condition, know that lithium-ion batteries are best stored at a temperature of about +5 ° C. The higher it is and the closer the charge level is to 100%, the faster the battery ages and loses capacity. It is best to charge it to 40–50%, remove it from the device, pack it in a sealed plastic bag, put it in the refrigerator (but not in the freezer!) and recharge it periodically.

That's all I wanted to say about batteries, our friends, electronic pets. Be it a phone, a player or a camera.

This article was prepared based on materials found on the Internet and collected here in a pile for convenience and understanding of the essence of the process.

Any questions? Write in the comments and I will definitely answer.

P.S. Friends, if you liked the article or found it useful. Do me a favor too. Share a link to the article on your VKontakte, Odnoklassniki, Facebook, Twitter and other pages. To do this, you just need to click the buttons at the bottom of the page and follow the simple steps of the instructions. I also invite you to subscribe to my newsletter, then you will definitely not miss the next, hopefully interesting and useful, article. The subscription form is located in the upper right corner of the page.

• Translation

Death of the Battery: We've all seen it happen. In phones, laptops, cameras, and now electric cars, the process is painful and - if you're lucky - slow. Over the years, the lithium-ion battery that once powered your devices for hours (and even days!) gradually loses its ability to hold a charge. In the end, you will come to terms with it, maybe curse Steve Jobs, and then buy a new battery, or even a new gadget altogether.

But why is this happening? What happens in a battery that causes it to die? The short answer is that due to the damage from prolonged exposure to high temperatures and a large number of charge and discharge cycles, the movement of lithium ions between the electrodes eventually begins to break down.

A more detailed answer that takes us through unwanted chemical reactions, corrosion, the threat of high temperatures and other factors that affect performance starts with an explanation of what happens in lithium-ion batteries when everything is working well.

Introduction to Lithium Ion Batteries

During charging, an electric current moves lithium ions from the cathode to the anode. During discharge (in other words, when the battery is used), the ions move back towards the cathode.

Daniel Abraham, a scientist at Argonne National Laboratory who conducts research into the degradation of lithium-ion cells, compared the process to water in a hydropower system. Water moving up requires energy, but it flows down very easily. In fact, it supplies kinetic energy, Abraham says, in a similar way that the lithium cobalt oxide in the cathode "doesn't want to give up its lithium." Like upward moving water, energy is required to move the lithium atoms out of the oxide and into the anode.

During charging, ions are placed between sheets of graphite that make up the anode. But, as Abraham puts it, "they don't want to be there; the first chance they get they'll move back," like water flowing down a hill. This is detente. A long-life battery will withstand several thousand such charge-discharge cycles.

When is a dead battery really dead?

In cell phones, on the other hand, high power is less important than capacity, or the amount of energy the battery can hold. High capacity batteries last longer on a single charge.

Over time, a battery degrades in several ways that can affect both capacity and power, until eventually it simply cannot perform basic functions.

Think of it in another water analogy: charging a battery is like filling a bucket with tap water. The volume of the bucket represents the battery's capacity, or capacity. The speed at which you can fill it - by turning the tap on full or in a trickle - is the power. But time, high temperatures, multiple cycles and other factors eventually create a hole in the bucket.

In the bucket analogy, water leaks out. In a battery, the lithium ions are removed, or "tied," Abraham says. As a result, they are deprived of the ability to move between the electrodes. So after a few months, a mobile phone that originally required charging once every couple of days now needs to be charged every 24 hours. Then twice a day. Eventually, too many lithium ions will become “bound” and the battery will not hold any useful charge. The bucket will stop holding water.

What breaks and why

The problem is that the crystal structure can change with each charge and discharge. Ions from apartment A will not necessarily return home, but they may move into apartment B next door. Then ion from apartment B finds his place occupied by this tramp and, without entering into confrontation, decides to move in further down the corridor. And so on.

Gradually, these “phase transitions” in the substance transform the cathode into a new crystalline crystal structure with different electrochemical properties. The exact arrangement of atoms that initially produces the required performance changes.

In hybrid car batteries, which are needed only to supply power when the vehicle accelerates or brakes, Abraham notes, these structural changes occur much more slowly than in electric vehicles. This is due to the fact that in each cycle only a small portion of the lithium ions moves through the system. As a result, it is easier for them to return to their original positions.

Corrosion problem

If the bonding material breaks down, it will cause the surface of the current collector to “peele.” If a metal corrodes, it cannot move electrons efficiently.

Corrosion in a battery can result from the interaction of the electrolyte and the electrodes. The graphite anode is “easily released”, i.e. it easily “donates” electrons to the electrolyte. This can result in an unwanted coating on the surface of the graphite. The cathode, meanwhile, is highly "oxidizable," meaning it readily accepts electrons from the electrolyte, which in some cases can corrode the aluminum of the current collector or form a coating on parts of the cathode, Abraham says.

Too much of a good thing

In reality, however, TEI is a very unstable defender. It protects graphite well at room temperature, Abraham says, but at high temperatures or when the battery charge drops to zero (“deep discharge”), TEI can partially dissolve in the electrolyte. At high temperatures, electrolytes also tend to decompose and side reactions are accelerated.

When favorable conditions return, another protective layer will form, but this will eat up some of the lithium, causing the same problems as a leaky bucket. We will have to charge our cell phone more often.

So, we need TEI to protect the graphite anode, and in this case, there really can be too much of a good thing. If the protective layer becomes too thick, it becomes a barrier to lithium ions, which are required to move back and forth freely. This affects power, which Abraham emphasizes is “extremely important” for electric vehicles.

Creating Better Batteries

Meanwhile, engineers at battery and electric vehicle companies are working on housings and thermal management systems in an attempt to keep lithium-ion batteries within a constant, healthy temperature range. We, as consumers, are left to avoid extreme temperatures and deep discharges, and continue to grumble about batteries that always seem to die too quickly.

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 the other 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 changed 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 good 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 the 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.