Lithium-ion battery uses carbon material as the negative electrode and uses a lithium-containing compound as the positive electrode. There is no metal lithium, only lithium ions. Lithium-ion battery refers to the general term of a battery that uses lithium ion intercalation compound as the positive electrode material. The charging and discharging process of a lithium ion battery is the process of intercalation and deintercalation of lithium ions.

　　In the process of intercalation and deintercalation of lithium ions, it is accompanied by intercalation and deintercalation of electrons equivalent to lithium ions (it is customary to indicate the insertion or deintercalation of the positive electrode and the insertion or deintercalation of the negative electrode). In the process of charging and discharging, lithium ions are intercalated / deintercalated and intercalated / deintercalated between the positive and negative electrodes, which is visually called "rocking chair battery".

　　When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the generated lithium ions move to the negative electrode through the electrolyte. The carbon used as the negative electrode has a layered structure, and it has many micropores. The lithium ions reaching the negative electrode are inserted into the micropores of the carbon layer. Similarly, when the battery is discharged (that is, the process we use the battery), the lithium ions embedded in the carbon layer of the negative electrode come out and move back to the positive electrode. The more lithium ions returned to the positive electrode, the higher the discharge capacity.

Generally, the charging current of a lithium battery is set between 0.2C and 1C. The larger the current, the faster the charging and the greater the battery heat. Moreover, if the current is too large to charge, the capacity is not full, because the electrochemical reaction inside the battery takes time. Just like pouring beer, if it is poured too quickly, it will produce foam, but it will not be full.

For batteries, normal use is the process of discharging. Lithium battery discharge needs to pay attention to several points：

First, the discharge current should not be too large. Excessive current will cause internal heating of the battery, which may cause permanent damage. On mobile phones, this is not a problem, you can ignore it.

　　Second, it must not be overdischarged! The internal storage of electrical energy in a lithium battery is achieved by a reversible chemical change in electrochemistry. Excessive discharge will cause an irreversible reaction to this chemical change. Therefore, lithium batteries are afraid of overdischarge. If the discharge voltage is lower than 2.7V, the battery may be scrapped. Fortunately, the protection circuit has been installed inside the battery of the mobile phone, and the voltage has not been lowered to the point of damaging the battery, the protection circuit will work and stop discharging.