Teach you how to buy a lithium battery

Lithium batteries are classified into lithium ion batteries and polymer lithium batteries. The electrolyte of the lithium ion battery is flowing, and the electrolyte of the polymer lithium battery is solid. Therefore, the lithium ion battery is more unstable than the polymer lithium battery, which can explode when struck by external forces or when using a substandard charger. Many batteries used in portable electronic products such as mobile phones, notebook computers, and digital cameras are lithium batteries. Buying a poor quality lithium battery is like putting a "time bomb" around you. Therefore, consumers must pay attention to the following points when purchasing lithium batteries:

Step / method

1. Is the capacity clearly indicated? A lithium battery without a clearly indicated capacity (2200mAh or 4400mAh) is likely to be a re-assembled garbage battery using a poor quality battery core or a recycled battery core. There are many cheap lithium batteries in the market, which are made by recycling battery cores or disassembling battery cores. Although the price is cheap, the life is short, the quality is unstable, and accidental use may damage the mobile phone or even explode.

2. Whether to guarantee the standby time. The standby time is the continuous use time after the lithium battery is loaded into the mobile phone until the next charge. Lithium batteries sold in the general market cannot guarantee the standby time for customers. This is because of the unstable battery quality. Many inexpensive batteries use short-quality batteries, so the standby time is short.

3. Whether with a safety circuit. The characteristics of the lithium battery determine that the lithium battery must be equipped with a protective plate to prevent the lithium battery from overcharging, over-discharging and short-circuiting. The lithium battery without the protective plate may be deformed, leaked or exploded. Under the fierce price competition, each battery packaging factory seeks a lower-cost protection circuit, or simply omits the device, making the market full of explosive lithium batteries. Consumers can't tell if they have a protective circuit board from the outside, so it's best to choose a reputable merchant to buy.

Lithium battery refers to a battery containing lithium (including metal lithium, lithium alloy, and lithium ion, lithium polymer) in an electrochemical system. Lithium batteries can be roughly divided into two categories: lithium metal batteries and lithium ion batteries. Lithium metal batteries are generally non-rechargeable and contain metallic lithium. Lithium-ion batteries do not contain metallic lithium and are rechargeable.

Folding battery chemical reaction principle

A lithium metal battery is a type of battery using a lithium metal or a lithium alloy as a negative electrode material and using a nonaqueous electrolyte solution. The earliest lithium battery used the following reaction: Li + MnO2 = LiMnO2, the reaction is a redox reaction, discharge.

It was first used in pacemakers. The self-discharge rate of the lithium battery is extremely low, and the discharge voltage is gentle. The device that is implanted in the human body can operate for a long time without recharging. Lithium batteries generally have a nominal voltage higher than 3.0 volts, making them more suitable for use as integrated circuit power supplies. Manganese dioxide batteries are widely used in calculators, digital cameras, and watches.

Various materials have been studied in order to develop more excellent varieties unprecedented product. For example, lithium sulfur dioxide batteries and lithium thionyl chloride batteries are very characteristic. Their positive active materials are also solvents for the electrolyte. This structure only occurs in electrochemical systems that are not aqueous solutions. Therefore, the research of lithium batteries has also promoted the development of electrochemical theory of non-aqueous systems. In addition to the use of various non-aqueous solvents, research on polymer thin film batteries has also been conducted.

In 1992, Sony successfully developed lithium-ion batteries. Its practicality makes people's mobile phones, notebooks, calculators and other portable electronic devices much smaller in weight and size. The use time is greatly extended. Since the lithium ion battery does not contain heavy metal cadmium, it greatly reduces environmental pollution compared with the nickel cadmium battery.

Lithium batteries are usually divided into two categories:

Lithium metal battery: A lithium metal battery is generally a battery using manganese dioxide as a positive electrode material, metallic lithium or an alloy metal thereof as a negative electrode material, and a nonaqueous electrolyte solution.

Lithium-ion battery: A lithium-ion battery is generally a battery using a lithium alloy metal oxide as a positive electrode material, graphite as a negative electrode material, and a non-aqueous electrolyte.

Although the lithium metal battery has a high energy density, it can theoretically reach 3,860 watts/kg. However, since it is not stable enough and cannot be charged, it cannot be used as a power battery for repeated use. Lithium-ion batteries have been developed as the main power battery due to their ability to be repeatedly charged. However, because of its combination with different elements, the composition of the cathode material varies greatly in various aspects, leading to an increase in the industry's disputes over the cathode material route.

Generally, the most commonly used power batteries are lithium iron phosphate batteries , lithium manganate batteries, lithium cobalt oxide batteries, and ternary lithium batteries (ternary nickel cobalt manganese).

Lithium battery anode materials are roughly divided into the following types:

The first type is carbon anode material:

At present, the anode materials actually used for lithium ion batteries are basically carbon materials, such as artificial graphite, natural graphite, mesocarbon microspheres, petroleum coke, carbon fiber, pyrolysis resin carbon and the like.

The second is tin-based anode material:

Tin-based anode materials can be classified into tin oxides and tin-based composite oxides. Oxide refers to oxides of various valence metal tins. There are currently no commercial products.

The third type is a lithium-containing transition metal nitride anode material, and there are currently no commercial products.

The fourth type is alloy anode material:

Including tin-based alloys, silicon-based alloys, bismuth-based alloys, aluminum-based alloys, bismuth-based alloys, magnesium-based alloys and other alloys, there are currently no commercial products.

The fifth type is a nano-scale anode material: carbon nanotubes, nano-alloy materials.

The sixth nanomaterial is nano-oxide material: At present, Hefei Xiangzheng Chemical Technology Co., Ltd. based on the latest development of the market development of lithium battery new energy industry in 2009, many companies have begun to use nano-titanium oxide and nano-silica to add to the traditional Graphite, tin oxide, and carbon nanotubes greatly increase the amount of charge and discharge and the number of charge and discharge cycles of lithium batteries.

Technical technology is an important indicator basis for measuring whether an enterprise is advanced, whether it has market competitiveness, and whether it can continuously lead the competitor. With the rapid development of China's lithium battery materials market, the related core production technology application and research and development will become the focus of attention in the industry. Understanding the R&D trends, process equipment, technology applications and trends of the core technology of lithium battery material production is crucial for enterprises to improve product specifications and improve market competitiveness.

The conductive coating is also called pre-coating. In the lithium battery industry, it is usually referred to as a conductive coating on the surface of the positive current collector-aluminum foil. The aluminum foil coated with the conductive coating is called pre-coated aluminum foil or simply coated. Layer aluminum foil, its earliest experiment in the battery can be traced back to the 70s, and in recent years, with the development of new energy industry, especially lithium iron phosphate battery, it has become a popular new technology or new material in the industry.

Performance

The conductive coating can effectively improve the adhesion of the pole piece in the lithium battery, reduce the amount of the binder used, and at the same time significantly improve the electrical properties of the battery.

1. Contact resistance drops by 40%

2. Reduce the amount of adhesive by 50%

3. Under the same rate, the battery voltage platform is increased by 20%.

4. The adhesion between material and current collector is increased by 30%, and there will be no delamination after long-term circulation.

Lithium battery coated carbon foil instructions

First, the material description

The carbon coated aluminum foil is composite slurry mainly composed of conductive carbon and a high-purity electronic aluminum foil, which is produced by a transfer coating process.

Second, the scope of application

1. Power type lithium battery with fine particle active material

2. The positive electrode is lithium iron phosphate

3. The positive electrode is fine granule ternary/lithium manganate

4. Used for super capacitor, lithium primary battery (lithium, lithium manganese, lithium iron, button, etc.) instead of etching aluminum foil

Third, the performance of the battery / capacitor

1. Suppress battery polarization, reduce thermal effects, and improve rate performance;

2. Reduce the internal resistance of the battery and significantly reduce the dynamic internal resistance increase of the cycle;

3. Improve consistency and increase battery cycle life;

4. Improve the adhesion between the active material and the current collector, and reduce the manufacturing cost of the pole piece;

5. Protect the current collector from corrosion by the electrolyte;

6. Improve the high and low temperature performance of lithium iron phosphate battery and improve the processing performance of lithium iron phosphate and lithium titanate materials.

Fourth, the recommended parameters

The corresponding coated active material D50 is preferably not more than 4 to 5 μm, the compaction density is not more than 2.25 g/cm, and the specific surface area is in the range of 13 to 18 m 2 /g.

Five, the precautions in use

1. Storage requirements: In the environment where the temperature is 25±5°C and the humidity is not more than 50%, the erosion of aluminum foil by air and water vapor should be avoided during transportation;

2. This product is divided into two types, A and B. The key characteristics of each product are: A is black in appearance, the thickness of conventional coating is 4~8μm on both sides, the conductivity is more prominent; the appearance of B is light gray, regular The coating thickness is 2~3μm on both sides, the coating area can be welded in less layers, and the coating machine can recognize the jump gap;

3.B (grey) coated carbon foil can be directly ultrasonically welded in the coating area, only suitable for coiled battery welding tabs (up to 2-3 layers of pole pieces), but the ultrasonic power and time need to be fine-tuned;

4. The heat dissipation of the carbon layer is worse than that of the aluminum foil, so it is necessary to finely adjust the belt speed and the baking temperature when coating;

5. This product has a considerable improvement on the comprehensive performance of lithium batteries and capacitors, but it cannot be used as a major factor to change the performance of some aspects of the battery, such as battery energy density, high and low temperature performance, high voltage and so on.

Folding lithium battery drum

First, lithium battery shell characteristics

Lithium, atomic number 3, atomic weight 6.941, is the lightest alkali metal element. In order to improve safety and voltage, scientists have invented materials such as graphite and lithium cobalt oxide to store lithium atoms. The molecular structure of these materials forms a nanoscale fine storage grid that can be used to store lithium atoms. In this way, even if the battery casing is broken and oxygen enters, the oxygen molecules are too large to enter these fine cells, so that the lithium atoms do not come into contact with oxygen to avoid explosion.

This principle of lithium-ion batteries allows people to achieve high-density density while achieving safety. When a lithium ion battery is charged, the lithium atom of the positive electrode loses electrons and oxidizes to lithium ions. Lithium ions swim through the electrolyte to the negative electrode, enter the cell of the negative electrode, and obtain an electron, which is reduced to a lithium atom. When discharging, the entire program is reversed. In order to prevent the battery from being short-circuited by direct contact between the positive and negative terminals, a separator paper with a large number of fine holes is added to the battery to prevent short circuit. Good diaphragm paper can also automatically close the pores when the battery temperature is too high, so that lithium ions cannot pass through, so as to prevent the danger from happening.

Safeguard

Lithium battery cells will begin to produce side effects when they are overcharged to a voltage higher than 4.2V. The higher the overcharge voltage, the higher is the risk. After the lithium battery voltage is higher than 4.2V, the amount of lithium atoms remaining in the positive electrode material is less than half. At this time, the storage cell often collapses, causing a permanent drop in battery capacity. If the charging continues, since the cell of the negative electrode is already filled with lithium atoms, the subsequent lithium metal will accumulate on the surface of the negative electrode material. These lithium atoms grow dendrites from the surface of the negative electrode toward the direction of lithium ions. These lithium metal crystals pass through the separator paper, shorting the positive and negative electrodes. Sometimes the battery explodes before the short circuit occurs. This is because during the overcharging process, the electrolyte and other materials will crack and generate gas, causing the battery casing or pressure valve to bulge and rupture, allowing oxygen to enter and react with the lithium atoms deposited on the surface of the negative electrode, then exploded. Therefore, when charging a lithium battery, you must set the upper voltage limit to take into account the battery life, capacity, and safety. The optimal charging voltage is limited to 4.2V. Lithium batteries should also have a lower voltage limit when discharging. When the cell voltage is lower than 2.4V, some materials will start to be destroyed. Since the battery will self-discharge, the voltage will be lower for a longer time. Therefore, it is best not to put it at 2.4V to stop. During the period from the discharge of 3.0V to 2.4V, the energy released by the lithium battery is only about 3% of the battery capacity. Therefore, 3.0V is an ideal discharge cutoff voltage. In charge and discharge, in addition to the voltage limit, current limitation is also necessary. When the current is too large, lithium ions cannot enter the cell and will accumulate on the surface of the material. When these lithium ions obtain electrons, crystals of lithium atoms are generated on the surface of the material, which is dangerous as overcharge. In the event of a broken battery case, it will explode. Therefore, the protection of the lithium ion battery must include at least three factors: the upper limit of the charging voltage, the lower limit of the discharging voltage, and the upper limit of the current. In the general lithium battery pack, in addition to the lithium battery core, there will be a protective board, which is mainly to provide these three protections. However, these three protections of the protection board are obviously not enough, and the global lithium battery explosion is still frequent. To ensure the safety of the battery system, a more careful analysis of the cause of the battery explosion must be performed.

Second, the cause of the explosion analysis

1, the internal polarization is larger

2, the pole piece absorbs water and reacts with the electrolyte

3, the quality of the electrolyte itself, performance issues

4, the amount of liquid injection does not meet the process requirements when injecting liquid

5, laser welding and welding sealing performance in the assembly process is poor, leaking, leak detection when leaking

6, dust, pole piece dust is easy to lead to micro short circuit

7, the positive and negative electrodes are thicker than the process range, and it is difficult to enter the shell.

8, the problem of liquid injection sealing, steel ball sealing performance is not good, resulting in air drum

9, the shell material has a thick shell wall and the shell deformation affects the thickness.

Third, the type of explosion analysis

Explosion type analysis type of battery core explosion can be summarized as external short circuit, internal short circuit, and overcharge. The external part here refers to the outside of the battery cell, and includes a short circuit caused by poor insulation design inside the battery pack. When a short circuit occurs outside the cell, and the electronic component fails to cut off the circuit, high heat is generated inside the cell, causing some of the electrolyte to vaporize and the battery case is enlarged. When the internal temperature of the battery is as high as 135 degrees Celsius, the good quality diaphragm paper will close the pores, the electrochemical reaction will terminate or nearly terminate, the current will drop suddenly, and the temperature will slowly drop, thus avoiding the explosion. However, the pore closing rate is too poor, or the separator paper, which does not close the pores at all, will cause the battery temperature to continue to rise, more electrolyte vaporizes, and finally the battery casing is broken, and the battery temperature is raised even to The material burns and explodes.

The internal short circuit is mainly caused by the burr of the copper foil and the aluminum foil piercing the diaphragm, or the dendrite of lithium atoms piercing the diaphragm. These tiny needle-like metals can cause micro short circuits. Since the needle is very thin and has a certain resistance value, the current is not necessarily large. Copper and aluminum foil burrs are caused during the production process. The observed phenomenon is that the battery leaks too quickly, and most of them can be screened by the battery factory or assembly plant. Moreover, since the burrs are small, they are sometimes blown off, so that the battery returns to normal. Therefore, the probability of an explosion caused by a burr micro-short circuit is not high. In this way, it is possible to get a bad battery with a low voltage shortly after charging in each battery factory, but there are few explosion events and statistical support. Therefore, the explosion caused by the internal short circuit is mainly caused by overcharge.

Because, after overcharging, the lenticular lithium metal crystals are everywhere on the pole piece, and the piercing point is everywhere, and micro short circuits occur everywhere. Therefore, the battery temperature will gradually increase, and finally the high temperature will be the electrolyte gas. In this case, whether the temperature is too high, the material burns and explodes, or the outer shell is broken first, so that the air enters and the lithium metal is violently oxidized, which is the end of the explosion. However, such an explosion caused by an internal short circuit caused by overcharging does not necessarily occur at the time of charging. It is possible that when the battery temperature is not high enough for the material to burn and the gas generated is not enough to break the battery casing. The consumer terminates charging and takes the mobile phone out. At this time, the heat generated by the numerous micro short circuits slowly increases the temperature of the battery, and after a period of time, the explosion occurs. The common description of consumers is that when the phone is picked up, the phone is found to be very hot, and it will explode after being thrown away. In combination with the above types of explosions, we can focus on the prevention of overcharge, the prevention of external short circuits, and the safety of three-party explosion protection. Among them, overcharge prevention and external short circuit prevention are electronic protection, which has a great relationship with battery system design and battery assembly. The focus of battery safety improvement is chemical and mechanical protection, which has a great relationship with battery manufacturing plants.

Fourth, the design specification

Since there are hundreds of millions of mobile phones worldwide, to achieve security, the failure rate of security protection must be less than one in 100 million. Because the board's failure rate is generally much higher than one billion, therefore when designing a battery system, there must be more than two safety lines. A common mistake is to use a charger (adaptor) to directly charge the battery pack. In this way, the overcharged protection is completely transferred to the protection board on the battery pack. Although the failure rate of the protection board is not high, even if the failure rate is as low as one in a million, there is an explosion accident every day in the world. If the battery system can provide two safety protections for overcharging, over-discharging and over current respectively, if the failure rate of each protection is one in ten thousand, the two protections can reduce the failure rate to one hundred thousandth. The block diagram of a common battery charging system is as follows, including the charger and the battery pack.

1 charger also contains adapter (Adaptor) and charging controller two parts. The adapter converts AC power to DC power, and the charge controller limits the maximum current and maximum voltage of the DC power.

2 The battery pack contains two parts of the protection board and the battery core, and a PTC to limit the maximum current. In the following figure, the adapter AC variable DC text box functions: the current controller current limit voltage limit. Charger text box function: protection board overcharge, over discharge, over current protection. Battery packs text box function: current limiter. The battery cell uses a mobile phone battery system as an example. The overcharge protection system uses the charger output voltage to be set at about 4.2V to achieve the first layer of protection, so that even if the protection plate on the battery pack fails, the battery will not be overcharged. The second protection is the overcharge protection function on the protection board, which is generally set to 4.3V. In this way, the protection board is usually not responsible for cutting off the charging current, and only when the charger voltage is abnormally high, the action is required. Over current protection is the responsibility of the protection plate and the current limiting plate. This is also two protections against over current and external short circuit. Since over-discharge only occurs during the process in which the electronic product is used. Therefore, the general design is to provide the first protection by the circuit board of the electronic product, and the protection board on the battery pack provides the second protection. When the electronic product detects that the power supply voltage is lower than 3.0V, it should automatically shut down. If the product was not designed with this feature in mind, the protection board will close the discharge loop when the voltage is as low as 2.4V.

General: When designing a battery system, it is necessary to provide two electronic protections for overcharging, over-discharging, and over current respectively. Charge the board after removing it. If the battery will explode, it means poor design. Charge the board after removing it. If the battery will explode, it means poor design. Although the above method provides two protections, since the consumer often buys a non-original charger to charge after the charger is broken, the charger manufacturer often removes the charging controller based on cost considerations to reduce the cost. . As a result, bad money drove out good money, and many inferior chargers appeared on the market. This makes overcharge protection lose the first and most important line of defense. Overcharge is the most important factor causing battery explosion. Therefore, poor quality charger can be regarded as the culprit of battery explosion. Of course, not all battery systems use the solution shown above. In some cases, there will also be a charge controller design within the battery pack.

For example, many notebook computers have a battery controller and a charging controller. This is because notebook computers typically have a charge controller in the computer and only give the consumer an adapter. Therefore, the external battery pack of the notebook computer must have a charge controller to ensure the safety of the external battery pack when charging with the adapter. In addition, products that are charged by a car cigarette lighter sometimes have a charge controller in the battery pack. The last line of defense: If the electronic protection measures fail, the last line of defense is provided by the battery. The safety level of the battery cell can be roughly graded according to whether the battery core can be externally short-circuited and over-charged. Before the battery explodes, if there are lithium atoms inside the surface of the material, the explosive power will be even greater. Moreover, the protection of overcharge is often left because the consumer uses a poor quality charger and only one line of defense is left. Therefore, the ability of the battery to resist overcharging is more important than the ability to resist external short circuits. Aluminum shell and steel shell battery safety comparison Aluminum shell has a high safety advantage compared to steel shell.

Is Lithium battery positive and negative carbon tubes? Why should VGCF carbon tubes be added to the positive and negative active materials of lithium ion batteries?

1. Regardless of whether the positive or negative active material has the problem of expansion and contraction, generally 20% (theoretical value: 10.5%) expansion shrinkage of the negative carbon material, and 6% (theoretical value: 2%) expansion like the LFP positive electrode material yield. When charging and discharging multiple times, the contact between the positive and negative active material particles and the particles is small, the gap is increased, and even some are separated from the collector, resulting in intermittent discontinuous phase between the electron and the ion transport path, becoming a dead active material, not Participate in the electrode reaction. Therefore, the cycle life is reduced. VGCF carbon tube has a large aspect ratio. Even if the positive and negative active materials expand and contract, the gap between the active material particles can be connected by VGCF carbon tube bridges, and the electron and ion transmission will not be interrupted.

Folded lithium primary battery

Lithium-manganese dioxide battery (CR)

The metal lithium is used as the negative electrode, the heat-treated manganese dioxide is used as the positive electrode, the separator is made of PP or PE film, the cylindrical battery is the same as the lithium ion battery separator, and the electrolyte is the organic solution of lithium perchlorate, cylindrical or button type. . The battery needs to be produced in a dry environment with a humidity of ≤ 1%.

Features: low self-discharge rate, annual self-discharge can be ≤ 1%, fully sealed (metal welding, lazerseal) battery can meet 10 years of life, semi-sealed battery is generally 5 years, if the work control is not good, it cannot reach this life. In the development of cylindrical lithium manganese battery, Yiwei has done a good job. At present, it has realized automatic production. The battery can be short-circuited, over-discharged, etc.

Generally, on the motherboard of a desktop computer, there is a button-type lithium battery that provides a weak current and can be used normally for about 3 years. Some hotel access cards, instrumentation, etc. also use lithium-manganese dioxide batteries, which have been used in recent years. The amount has decreased year by year.

Lithium-thionyl chloride battery

The metal lithium is used as the negative electrode, the positive electrode and the electrolyte are thionyl chloride (thionyl chloride), and the cylindrical battery is charged with a voltage of 3.6V, which is one of the most stable types of batteries, and is also the current unit volume. (mass) the highest capacity battery. It’s suitable for use on electronic equipment that cannot be maintained frequently, providing a fine current.

Other lithium batteries include lithium-sulfur ferrous batteries, lithium-sulfur dioxide batteries, and the like.

Folding lithium ion battery

Lithium-ion batteries are currently available in liquid lithium-ion batteries (LIB) and polymer lithium-ion batteries (PLB). Among them, the liquid lithium ion battery refers to a secondary battery in which the Li+ intercalation compound is a positive electrode or a negative electrode. The positive electrode is a lithium compound LiCoO or LiMnO? And the negative electrode is a lithium-carbon intercalation compound. Lithium-ion battery is an ideal energy source for the development of the 21st century due to its high operating voltage, small size, light weight, high energy, no memory effect, no pollution, low self-discharge and long cycle life.

With the development of microelectronics technology in the twentieth century, the number of miniaturized devices is increasing, and high requirements are placed on power supplies. Lithium batteries have entered a large-scale practical stage.

The earliest applied lithium primary battery was used in pacemakers. Since the self-discharge rate of the lithium sub-battery is extremely low, the discharge voltage is very gentle. It makes it possible to implant the pacemaker into the human body for a long time.

Lithium-manganese batteries generally have a nominal voltage higher than 3.0 volts, and are more suitable for integrated circuit power supply, and are widely used in computers, calculators, and watches.

Nowadays, lithium-ion batteries are widely used in mobile phones, notebook computers, power tools, electric vehicles, street lamp backup power supplies, navigation lights, household appliances, and can be said to be the largest application group.

Folding research and development prospects

Various materials have been studied in order to develop more excellent varieties and creating an unprecedented product. For example, lithium sulfur dioxide batteries and lithium thionyl chloride batteries are very characteristic. Their positive active materials are also solvents for the electrolyte. This structure only occurs in electrochemical systems that are not aqueous solutions. Therefore, the research of lithium batteries has also promoted the development of electrochemical theory of non-aqueous systems. In addition to the use of various non-aqueous solvents, research on polymer thin film batteries has also been conducted.

Lithium batteries are widely used in energy storage power systems such as hydropower, firepower, wind power and solar power stations, uninterruptible power supplies for post and telecommunications, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment,special and many other fields.

Lithium-ion batteries have been widely used in portable appliances such as laptops, camcorders, and mobile communications due to their unique performance advantages. The large-capacity lithium-ion battery currently developed has been tested in electric vehicles and is expected to become one of the main power sources for electric vehicles in the 21st century, and will be applied inspecial,special and energy storage. With the shortage of energy and the pressure on the world's environmental protection, lithium battery is now widely used in the electric vehicle industry, especially the emergence of lithium iron phosphate battery, which has promoted the development and application of the lithium battery industry.

In order to avoid over-discharge or over-charging of the battery due to improper use, a triple protection mechanism is provided in the single-cell lithium ion battery. First, the switching element is used. When the temperature inside the battery rises, its resistance value rises. When the temperature is too high, the power supply will be automatically stopped. Second, the appropriate separator material is selected. When the temperature rises to a certain value, the micron-sized micropores on the separator will be dissolved automatically, so that the lithium ions will not pass, and the internal reaction of the battery will stop. The third is to set the safety valve (that is, the venting hole at the top of the battery). When the internal pressure of the battery rises to a certain value, the safety valve automatically open to ensure the safety of the battery.

Sometimes, although the battery itself has safety control measures, if the control fails due to some reasons, and the safety valve or gas is not enough to be released through the safety valve, the internal pressure of the battery will rise sharply and cause an explosion.

Under normal circumstances, the total energy stored in a lithium-ion battery is inversely proportional to its safety. As the battery capacity increases, the battery volume also increases, and its heat dissipation performance deteriorates, and the possibility of an accident increases greatly. For lithium-ion batteries for mobile phones, the basic requirement is that the probability of a safety accident is less than one in a million, which is the minimum standard acceptable to the public. For large-capacity lithium-ion batteries, especially for large-capacity lithium-ion batteries such as automobiles, it is particularly important to use forced cooling.

Choosing a safer electrode material and selecting lithium manganate material ensure that the lithium ion of the positive electrode is completely embedded in the carbon hole of the negative electrode in the molecular structure, which fundamentally avoids the generation of dendrites. At the same time, the stable structure of lithium manganate makes its oxidation performance far lower than that of lithium cobaltate. The decomposition temperature exceeds 100 °C of lithium cobaltate. Even if internal short circuit (acupuncture) due to external force, external short circuit, overcharge, it is fully capable. The danger of burning and explosion due to precipitation of metallic lithium is avoided.

In addition, the use of lithium manganate materials can also significantly reduce costs.

To improve the performance of existing safety control technology, we must first improve the safety performance of lithium-ion battery cells, which is especially important for large-capacity batteries. The separator with good thermal shutdown performance is selected. The function of the separator is to allow the passage of lithium ions while isolating the positive and negative electrodes of the battery. When the temperature rises, it is closed before the separator melts, so that the internal resistance rises to 2000 ohms, and the internal reaction is stopped.

When the internal pressure or temperature reaches the preset standard, the explosion-proof valve will open and begin to relieve pressure to prevent excessive accumulation of internal gas, deformation, and eventually the housing burst.

Improve control sensitivity, select more sensitive control parameters, and combine control with multiple parameters (this is especially important for high-capacity batteries). For large-capacity lithium-ion battery packs, it is composed of multiple cells in series/parallel. For example, the voltage of a notebook computer is 10V or more, and the capacity is large. Generally, 3 to 4 single cells can be connected in series to meet the voltage requirement, and then 2 ~3 series battery packs are connected in parallel to ensure a large capacity.

The large-capacity battery pack itself must have a relatively complete protection function. Two circuit board modules should also be considered: the Protection Board Substrate (Protection Board PCB) module and the Smart Battery Gauge Board module. The complete battery protection design includes: level 1 protection IC (to prevent battery overcharge, over discharge, short circuit), level 2 protections IC (to prevent the second overvoltage), fuses, LED indications, temperature adjustment and other components.

Under the multi-level protection mechanism, even in the case of abnormal power chargers and laptops, the laptop battery can only be switched to the automatic protection state. If the situation is not serious, it will still work normally after re-plugging. An explosion will occur.

At present, the underlying technology used in lithium-ion batteries used in notebook computers and mobile phones is unsafe and requires a safer structure.

In short, with the advancement of materials technology and the growing understanding of the requirements for the design, manufacture, testing and use of lithium-ion batteries, future lithium-ion batteries will become safer.

The page contains the contents of the machine translation.