How do we care for the lithium battery of our machine? This problem has been plaguing many loyal users of mobile phones, including me. After consulting some materials, I had the opportunity to consult a Ph.D. in electrochemistry and a deputy director of a well-known battery research institute in China. I will write some relevant knowledge and experience recently obtained to readers.
The positive electrode material of a lithium ion battery usually consists of an active compound of lithium, and the negative electrode is a carbon of a special molecular structure. The main component of the common positive electrode material is LiCoO2. When charging, the potential applied to the two poles of the battery forces the compound of the positive electrode to release lithium ions, and is embedded in the carbon in which the negative electrode molecules are arranged in a sheet structure. At the time of discharge, lithium ions are precipitated from the carbon of the sheet structure and recombined with the compound of the positive electrode. The movement of lithium ions produces a current.
Although the principle of chemical reaction is very simple, in actual industrial production, there are many practical problems to be considered: the material of the positive electrode needs additives to maintain the activity of multiple charge and discharge, and the material of the negative electrode needs to be designed at the molecular structure level. It contains more lithium ions; the electrolyte filled between the positive and negative electrodes needs to have good conductivity and reduce the internal resistance of the battery, in addition to being stable.

Although lithium-ion batteries have little memory effect of nickel-cadmium batteries, the principle of memory effect is crystallization, and this reaction is hardly produced in lithium batteries. However, lithium-ion batteries still have a reduced capacity after multiple charge and discharge cycles, which are complicated and diverse. Mainly the change of the positive and negative materials themselves. From the molecular point of view, the hole structure containing lithium ions on the positive and negative electrodes will gradually collapse and block; from the chemical point of view, the positive and negative materials are reactively passivated, and the side reaction is stable. Other compounds. Physically, the positive electrode material gradually peels off, and finally, the number of lithium ions in the battery that can freely move during charge and discharge is finally reduced.

Overcharging and over-discharging will cause permanent damage to the positive and negative electrodes of lithium-ion batteries. From a molecular perspective, it can be intuitively understood that excessive discharge will cause the anode carbon to release lithium ions excessively, causing the sheet structure to collapse. Overcharging will hardly plug too much lithium into the negative carbon structure, and some of the lithium ions will no longer be released. This is why lithium-ion batteries are usually equipped with a charge and discharge control circuit.

Unsuitable temperatures will cause other chemical reactions inside the lithium-ion battery to form compounds that we do not want to see, so there are protective temperature-controlled separators or electrolyte additives between the positive and negative electrodes of many lithium-ion batteries. When the temperature of the battery is raised to a certain extent, the pores of the composite membrane are closed or the electrolyte is denatured, and the internal resistance of the battery is increased until the circuit is broken, and the battery is no longer heated to ensure that the charging temperature of the battery is normal.

Can deep charge and discharge increase the actual capacity of lithium-ion batteries? The experts told me clearly that this is meaningless. They even said that the so-called "activation" of the first three full charge and discharge, in the knowledge of their two doctors, can not figure out what is necessary. However, why do many people change the capacity indicated in Battery Information after deep charging? It will be mentioned later.
Lithium-ion batteries generally have a management chip and a charge control chip. The management chip has a series of registers, which have values such as capacity, temperature, ID, state of charge, and number of discharges. These values will gradually change during use. I personally think that the main function of the "use should be fully charged and discharged once a month" in the instructions for use should be to correct the improper values in these registers, so that the battery's charge control and nominal capacity match the actual situation of the battery.

The charging control chip mainly controls the charging process of the battery. The charging process of lithium-ion battery is divided into two stages, the constant current fast charging phase (when the battery indicator is yellow) and the constant voltage current decreasing phase (the battery indicator light flashes green. During the constant current fast charging phase, the battery voltage is gradually increased. The standard voltage to the battery is then transferred to the constant voltage stage under the control chip, the voltage is no longer raised to ensure that it will not overcharge, and the current gradually decreases to zero as the battery power rises, and the charging is finally completed.

The electricity statistic chip can calculate the battery's power by recording the discharge curve (voltage, current, time), which is the wh. value we read in Battery Information. The lithium-ion battery will change its discharge curve after repeated use. If the chip has no chance to read the complete discharge curve again, the calculated power is not accurate. So we need to deep charge the chip that calibrates the battery. Finally, my opinion on the maintenance of the battery is:
1. Do not deliberately ensure that each time you have finished charging and refilling;
2. You can do a deep charge and discharge under the control of the protection circuit for a period of time to correct the battery's power statistics, but this will not increase the actual capacity of your battery.
3. Long-term unused batteries should be placed in a cool place to reduce the speed of their internal passivation reaction.
4. The protection circuit is also unable to monitor the self-discharge of the battery. The battery that has not been used for a long time should be charged with a certain amount of power to prevent the battery from being over-discharged due to excessive discharge during storage.
In fact, there is not much use in the battery to pay attention to, in other words, it is not too much to consider. How many times a battery can be used, perhaps more different from the individual differences in the manufacture of the battery itself, rather than the method of use. Choosing a mobile phone brand with good reputation is undoubtedly one of the guarantees for the long life of battery use.