The proper usage of lithium batteries

Types of lithium batteries The

Secondary batteries currently used on the market mainly include nickel-hydrogen (Ni-MH) and lithium-ion (Li-ion). Lithium ion batteries have been mass-produced with a liquid lithium ion battery (LiB) and lithium-ion polymer battery (of LiP) two kinds. 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 a highly active metal (remember its position in the periodic table?), it is not safe to use, it often burns and bursts when charging. In the situation, there was a modified lithium-ion battery, which added components that inhibit lithium activity (such as cobalt, manganese, etc.), so that lithium battery is truly 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, while 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, and also limits 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 area 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 and cause fire in the case of overcharging. This is very dangerous, so it is necessary to install a protective IC circuit to ensure that the battery does not over expose for 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 Current-Constant Voltage) charging method used in the lithium ion secondary battery.

Mobile phone manufacturers' application to lithium batteries

Although almost all manufacturers have tended to adopt lithium-ion batteries in recent years, the world's major mobile phone manufacturers still have their own characteristics and habits, such as once in the same paragraph. In the historical period:

Nokia: Ni-MH (NiMH) batteries, LiB (Liquid Lithium Ion) batteries, and LiP (Polymer Lithium Ion) batteries are not used.

Ericsson: Ni-MH battery, LiB battery, LiP battery.

Motorola: Ni-MH battery, LiB battery, and LiP battery are not used.

It is not difficult to find that Ericsson reflects the true nature of its mobile phone technology pioneer from the earliest use of LiP polymer lithium-ion batteries for mobile phones. According to the information I found, the main manufacturers of polymer lithium-ion batteries are Japanese companies such as SONY, Panasonic, GS, etc. In 2000, the production volume reached 21 million, of which 50% were Ericsson mobile phones. Today, in 2002, lithium-ion batteries have been widely used and popularized on other mobile phone manufacturers. However, in the use of polymer lithium-ion batteries, it is still far from being popularized among all mobile phone manufacturers' products, and it will take time to widely use them.

On the other hand, although lithium-ion batteries have many advantages, they are also defective, such as high price and low number of charge and discharge cycles. 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.

From this point of view, there is currently no perfect battery.

The correct 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 a lithium battery, 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 3-5 normal charge and discharge cycles, 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 in practice, it is best to use standard methods to charge this "natural activation" method from the beginning.

For the "activation" problem of lithium batteries, there are many sayings: 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 over discharge 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 in normal use?

We can often see this statement because the number of times of charging and discharging 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): >1000 cycles

Cycle life (100% DOD): >200 times

DOD is the abbreviation for 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 to the relative total capacity of the actual charge: 10% * 1000 = 100, 100% * 200 = 200, the latter's full charge and discharge is still better, but the former netizen's statement to do some correction: in normal In this case, you should reserve the charge according to the principle that the remaining battery power is used up and recharge, but if your battery is not likely to stick to the whole day on the 2nd day, you should start charging in time. Of course, if you are willing to carry it back It’s a different matter to get the charger to the office.

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. Someone has used the example of automatic shutdown since the warning of the low battery level of the mobile phone is still not used. 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 correct approach to lithium batteries cell phones

sum up, I phone lithium battery charging and discharging, in use of the most important tips are:

① in accordance with standard procedures and charging time, even the first three have to do so;

② when When the mobile phone low battery is prompted, you should start charging as soon as possible;

The activation of the 3 lithium battery does not require a special method, and the lithium battery will naturally activate during normal use of the mobile phone. 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 good quality of the mobile phone and charger protection and control circuit, the protection of the lithium battery 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.