First of all, we must understand the charging and discharging principle of Li-ion lithium battery. The battery has two poles: the positive electrode is a lithium compound, and the negative electrode is graphite. Li-ion lithium battery charging and discharging are the mutual conversion of electric energy and chemical energy. During the movement of positive and negative electrodes, lithium ions are also changing into different compounds. We can think of lithium-ion as a car with a charge: when charging, the electric field makes the car drive to the negative electrode to store a certain amount of energy; when discharging, these charged lithium-ion cars run to the positive pole after undergoing a chemical reaction. In this process, a current supply is formed. In an ideal state, as long as the chemical structure of the positive and negative materials basically does not change, the reversibility of the battery charge and discharge is very good, and the Li-ion lithium battery can guarantee a long-term cycle.
Fast charging is mainly to ensure that lithium ions are quickly inserted from the positive electrode and quickly inserted into the negative electrode, without causing the deposition of lithium ions. Li-ion lithium battery charging is divided into three parts: constant current precharging, high current constant current charging and constant voltage charging. After the mobile phone's power is exhausted, the voltage drops. When it is lower than a certain value, the charger will use a relatively low current to precharge the Li-ion lithium battery. After a period of time, after the voltage of the Li-ion lithium battery is higher than the predetermined value, it enters the second stage of high-current constant-current charging. At this time, appropriately increasing the current can speed up the charging. If you are using a non-fast-charge mobile phone, the fast-charge charging head will not output high voltage and burn your mobile phone. From the perspective of multiple protection measures, the charging voltage and current of fast charging are in a safe state, as long as the original mobile phone charging adapter is used, it will not bring safety hazards.