Introduction to the use of lithium-ion batteries
In digital products, batteries are important in both technical and price considerations. Today, the digital products used in the market have basically completed the transition from nickel batteries to lithium batteries. Perhaps because the battery has just completed a revolution in nickel batteries to lithium batteries, people's understanding of lithium batteries is not uniform, and in many cases, incorrect statements and practices are quite popular. Therefore, knowing the knowledge of lithium batteries and mastering the correct use of lithium batteries is very necessary.
First, the type of lithium battery:
The secondary batteries currently used on the market mainly include nickel-hydrogen (Ni-MH) and lithium ion (Li-ion). Liquid lithium-ion batteries (LiB) and polymer lithium-ion batteries (LiP) have been mass-produced in lithium-ion batteries. So in many cases, the Li-ion on the battery must be a lithium-ion battery. But not necessarily a liquid lithium-ion battery, it may also be a polymer lithium-ion battery.
Lithium-ion batteries are an improved version of lithium batteries. Lithium batteries have been around for a long time, but lithium is highly active (remember its position in the periodic table? It will explode in water, which is more active than the chemical nature of sodium.) It is not safe, and it often burns and bursts when charging. Later, there is a modified lithium-ion battery, which incorporates components that can inhibit the active lithium (such as cobalt, manganese, etc.) so that the lithium battery can truly reach It is safe, efficient and convenient, and the old lithium battery is basically eliminated. As for how to distinguish them, it can be identified from the battery's logo, Li battery is Li, lithium battery is Li-ion. Nowadays, the so-called "lithium batteries" used in notebooks and mobile phones are actually lithium-ion batteries.
The basic structure of modern batteries includes three elements: positive electrode, negative electrode and electrolyte. As a kind of battery, a lithium ion battery also has these three elements. In general, lithium ion technology uses a liquid or inorganic colloidal electrolyte, so a strong outer casing is required to contain the flammable active ingredient, which increases the weight and cost of the battery, as well as the size and shape flexibility. In general, the minimum thickness of a liquid lithium ion secondary battery is 6 mm, which is more difficult to reduce.
The so-called polymer lithium ion battery uses at least one or more of these three main structures as a main battery system.
A new generation of polymer lithium-ion batteries is already highly polymerized, so the shape can be thinned (thinest 0.5 mm), arbitrarily aread and arbitrarily shaped, greatly improving the flexibility of battery design. Sex, so that it can be combined with the product requirements to make batteries of any shape and capacity. At the same time, the unit energy of the polymer lithium ion battery is 50% higher than the current general lithium ion battery, and its capacity, charge and discharge characteristics, safety, operating temperature range, cycle life and environmental performance are all larger than lithium ion batteries. Increase in range.
Liquid Lithium Ion (LiB) batteries currently on the market are prone to rupture of the safety valve due to overcharging, which is very dangerous. Therefore, it is necessary to install a protection IC circuit to ensure that the battery does not over-expose. The situation of charging. In the case of high-molecular-polymer lithium-ion batteries, this type of battery has better resistance to charge and discharge than liquid lithium-ion batteries, so the requirements for external protection IC lines can be appropriately relaxed. In addition, in terms of charging, the polymer lithium ion battery can be charged by the IC constant current, which can shorten the waiting time compared with the time required for the CCCV (Constant Currert-Constant Voltage) charging method used in the lithium ion secondary battery.
Second, although lithium-ion batteries have many advantages, they also have defects, such as high price and low charge and discharge times. Lithium batteries charge and discharge only 400-600 times, and special improvements have been made more than 800 times. Ni-MH batteries can be charged more than 700 times, and some good quality products can be charged and discharged up to 1200 times. In comparison, nickel-metal hydride batteries have longer life than lithium batteries. In addition, the price of nickel-metal hydride batteries is much lower than that of lithium batteries. And strictly speaking, lithium batteries also have a memory effect, but its memory effect is very low, basically negligible. Therefore, in some advertisements for lithium battery products, it can be seen that the manufacturer is branding "no memory effect, use with charge". Lithium battery, lithium ion battery, polymer lithium ion battery
From this point of view, there is currently no perfect battery (but lithium-ion batteries are inevitable to replace nickel-metal hydride batteries).
Third, the use of lithium-ion batteries
This part is the focus of this article. We will talk about it in three points.
1. How to charge a new battery
In the use of lithium batteries, it should be noted that after the battery is placed for a period of time, it enters a sleep state. At this time, the capacity is lower than the normal value, and the use time is also shortened. However, the lithium battery is easy to activate, as long as the battery is activated after 3 to 5 normal charge and discharge cycles, and the normal capacity is restored. Due to the characteristics of the lithium battery itself, it is determined that it has almost no memory effect. Therefore, the new lithium battery in the user's mobile phone does not require special methods and equipment during the activation process. Not only in theory, but from my own practice, it is best to use a standard method of charging this "natural activation" method from the beginning.
For the "activation" problem of lithium batteries, many claims are: charging time must be more than 12 hours, repeated three times in order to activate the battery. This statement that "the first three charges have to be charged for more than 12 hours" is obviously a continuation of nickel batteries (such as nickel cadmium and nickel hydride). So this kind of statement can be said to be misinformation at the beginning. The charge and discharge characteristics of lithium and nickel batteries are very different, and it is very clear to tell you that all the serious formal technical information I have reviewed emphasizes that overcharge and overdischarge will make lithium batteries, especially liquid lithium. Ion batteries cause great damage. Therefore, charging is preferably done in accordance with standard time and standard methods, especially for ultra-long charging of more than 12 hours. Usually, the charging method described in the mobile phone manual is a standard charging method suitable for the mobile phone.
In addition, the lithium battery phone or charger will automatically stop charging after the battery is fully charged, there is no so-called “turbulent†charging that the nickel battery charger has for 10 hours. In other words, if your lithium battery is full, it will be white charger on the charger. And none of us can guarantee that the characteristics of the battery's charge and discharge protection circuit will never change and the quality will be foolproof, so your battery will be on the edge of danger for a long time. This is another reason why we oppose long charging.
In addition, on some mobile phones, after charging for more than a certain period of time, if you do not remove the charger, then the system will not stop charging, and will start the discharge-charge cycle. Perhaps the manufacturer of this approach has its own purpose, but it is clearly unfavorable for the life of the battery and the phone/charger. At the same time, long charging takes a long time and often needs to be carried out at night. In the case of China's power grid, the voltage at night is high in many places and fluctuates greatly. As mentioned earlier, lithium batteries are very delicate, and they are much less resistant to fluctuations in charge and discharge than nickel, which in turn poses additional risks.
In addition, another aspect that cannot be ignored is that lithium batteries are also not suitable for over-discharge, and over-discharge is also disadvantageous for lithium batteries. This leads to the following problem.
2. When should I start charging during normal use?
In our forum, we can often see this statement, because the number of charge and discharge is limited, so the battery of the mobile phone should be recharged as much as possible. But I found an experimental table on the charge and discharge cycle of lithium-ion batteries. The data on cycle life are listed below:
Cycle life (10%DOD) vbscript:>1000 times
Cycle life (100% DOD) vbscript: >200 times
Among them, DOD is the abbreviation of depth of discharge. As can be seen from the table, the number of chargeables is related to the depth of discharge, and the cycle life at 10% DOD is much longer than that of 100% DOD. Of course, if you convert the relative total capacity to the actual charge: 10% * 1000 = 100, 100% * 200 = 200, the latter's full charge and discharge is still better, under normal circumstances, you should have the reserve to follow the battery remaining Charge the battery with the principle of recharging, but if your battery is not likely to last for the entire day on the second day, you should start charging in time. Of course, if you are willing to carry the charger to the office, it is a different matter.
And you need to charge to cope with the expected important events that will cause the communication to be busy, even if the battery still has a lot of power, then you only charge in advance, because you have not really lost "1" charge cycle life. That is, "0.x" times, and often this x will be small.
The principle of recharging the remaining battery power is not to go to extremes. One of the more widely spread sayings like long charging is that "try to run out of battery power, it is best to use automatic shutdown." This practice is actually only a nickel battery, the purpose is to avoid the memory effect, unfortunately it is also circulating on the lithium battery. Some people have used the example of automatic shutdown after they have not been charged because of the low battery warning. As a result, the mobile phone in this example did not respond during the subsequent charging and booting, and had to be sent to the customer service for repair. This is actually caused by the battery being over-discharged and the voltage is too low, so that it does not have normal charging and power-on conditions.
3. The time spent on lithium batteries will be shorter and shorter. What is going on? In fact, the material used for lithium batteries is an active substance, and the active substances will age. The materials used to make lithium batteries are sensitive to the degree of use and the environment, temperature and the like. Generally, the service life of a lithium battery is 300 to 500 times of charging and discharging, and the natural loss of the battery can significantly shorten the continuous use time of the battery. For excessive charging and excessive discharge, the battery activity is rapidly reduced, which directly leads to rapid aging of the lithium battery. Many mobile phone users may have this experience. It is clear that there is still a grid of power. After half an hour, it will display “low battery†and sometimes it will automatically shut down.
Therefore, when we use it in peacetime, we do not have to follow the basic principle of “exhaustion and fullnessâ€. If the basic principle of "exhaustion, fullness" is also observed in the case where the detection circuit does not detect the battery, the battery life is not long.
4, the correct practice for lithium battery mobile phones
To sum up, my most important tips on the charging and discharging problems of lithium battery mobile phones in use are:
1. Charge according to standard time and procedures, even if it is the first three times;
2. When there is a low battery power prompt, you should start charging as soon as possible;
3. The activation of the lithium battery does not require a special method, and the lithium battery will naturally activate during normal use. If you insist on using the "first three 12-hour long charge activation" method, it will not actually work.
Therefore, all the pursuit of 12 hours of ultra-long charging and the use of lithium battery mobile phones to automatically shut down are wrong. If you have done it in the wrong way, please correct it in time, maybe it is not too late.
Of course, in the case of digital products and chargers with good protection and control circuit quality, the protection of lithium batteries is quite guaranteed. So the understanding of the charging rules is the focus, and in some cases it is also possible to make some concessions. For example, if you find that the phone must be charged before you go to sleep at night, you can also start charging before going to bed. The point is that you should know what the right approach is and don't deliberately follow the wrong way.
Taking into account the error of the phone's power display and other factors, when the charger displays a green light, you can charge another 1.5 hours. Another point to note is that the lithium battery will be in a dormant state when it is not used for a long time, and needs to be activated before normal use. Generally, it can be activated after 3 to 5 charge and discharge cycles. According to the first two reasons, it is meaningless for the lithium battery in hibernation to be activated by long-term charging. Because the battery is fully charged (about 2 to 4 hours), the lithium battery protection circuit has been activated, cutting off the external power supply. Due to the function of the protection circuit, long-term charging has no harm to the lithium battery, but the startup of the protection circuit consumes the energy of the battery core. In case the protection circuit loses its function, the battery is damaged, and the mobile phone is damaged, and the result is not dare. Imagine. Therefore, considering the individual differences in mobile phones, lithium batteries and chargers, the first three charges and the subsequent charges are the same, only three to four hours.
Nickel-cadmium batteries are generally stored in discharge, because this involves dendritic problems, which means that the blunt part of the battery may dissolve and crystallize to a sharp point, causing a short circuit. For nickel-metal hydride batteries, generally 40-50% of the charge can be charged, the purpose is to prevent hydrogen and water from reacting. But you can't overcharge and prevent danger.
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