Overcharge and overdischarge will cause permanent damage to the positive and negative electrodes of lithium-ion batteries. From the molecular level, it can be intuitively understood that overdischarge will cause the negative electrode carbon to excessively release lithium ions and cause its sheet structure to collapse. Overcharging will force too much lithium ions into the carbon structure of the negative electrode, and some of them will no longer be able to be released.

　　How to maintain the lithium battery of our love phone to be considered correct? This problem has been plagued by many loyal mobile phone users, including me. After consulting some information, I recently had the opportunity to consult a PhD student in electrochemistry and the deputy director of a well-known domestic battery research institute. Now I will write down some relevant knowledge and experience gained recently for you readers.

　　The positive electrode material of lithium-ion batteries is usually composed of lithium active compounds, while the negative electrode is carbon with a special molecular structure. The main component of the common positive electrode material is LiCoO2. When charging, the electric potential applied to the two poles of the battery forces the compound of the positive electrode to release lithium ions, which are embedded in the carbon in which the molecules of the negative electrode are arranged in a sheet structure. During discharge, lithium ions are precipitated from the carbon of the sheet structure and recombine with the compound of the positive electrode. The movement of lithium ions generates an electric current.

　　Although the chemical reaction principle is very simple, in actual industrial production, there are many practical issues that need to be considered: the material of the positive electrode needs additives to maintain the activity of multiple charging and discharging, and the material of the negative electrode needs to be designed at the molecular structure level. To accommodate more lithium ions; the electrolyte filled between the positive and negative electrodes, in addition to maintaining stability, also needs to have good electrical conductivity to reduce the internal resistance of the battery.

　　Although lithium-ion batteries rarely have the memory effect of nickel-cadmium batteries, the principle of the memory effect is crystallization, and this reaction hardly occurs in lithium batteries. However, the capacity of a lithium-ion battery will still decrease after many times of charging and discharging, and the reasons are complex and diverse. It is mainly the change of the positive and negative materials themselves. From the molecular level, the hole structure of the positive and negative electrodes will gradually collapse and block; from a chemical point of view, it is the active passivation of the positive and negative materials, and side reactions appear to be stable. Other compounds. Physically, the positive electrode material will gradually peel off. In short, the number of lithium ions that can move freely during charging and discharging in the battery is ultimately reduced.

　　Overcharge and overdischarge will cause permanent damage to the positive and negative electrodes of lithium-ion batteries. From the molecular level, it can be intuitively understood that overdischarge will cause the negative electrode carbon to excessively release lithium ions and cause its sheet structure to collapse. Overcharging will force too much lithium ions into the carbon structure of the negative electrode, and some of them will no longer be able to be released. This is also the reason why lithium-ion batteries are usually equipped with charge and discharge control circuits.

　　Unsuitable temperature will trigger other chemical reactions inside the lithium-ion battery to generate undesirable compounds. Therefore, a protective temperature-controlled diaphragm or electrolyte additive is installed between the positive and negative electrodes of many lithium-ion batteries. When the battery heats up to a certain level, the pores of the composite membrane are closed or the electrolyte is denatured, the internal resistance of the battery increases until it is disconnected, and the battery no longer heats up to ensure that the battery charging temperature is normal.

　　And can deep charging and discharging increase the actual capacity of lithium-ion batteries? Experts clearly told me that this is meaningless. They even said that the so-called "activation" using the first three full charge and discharge, in the knowledge of their two doctors, can't figure out why this is necessary. But why do many people change the indicated capacity in BatteryInformation after deep charging and discharging? Will be mentioned later.

　　Lithium-ion batteries generally have a management chip and a charging control chip. Among them, there are a series of registers in the management chip, which store values such as capacity, temperature, ID, charging status, and discharge times. These values will gradually change during use. I personally think that the main effect of the “full charge and discharge once a month or so” in the instructions for use should be to correct the inappropriate values in these registers so that the battery 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 batteries is divided into two stages, the constant current fast charge stage (when the battery indicator is yellow) and the constant voltage current decrease stage (the battery indicator flashes green. The constant current fast charge stage, the battery voltage gradually increases When it reaches the standard voltage of the battery, it is then transferred to the constant voltage stage under the control chip. The voltage does not increase to ensure that it will not be overcharged. The current gradually decreases to 0 as the battery power increases, and the charging is finally completed.