Formation

The composition, content and detection system are the most critical links in the back-end process. The composition and capacity of the lithium battery cell is to realize the initialization of the battery by charging and discharging, and activate the active material of the cell, which is a process of energy conversion. The composition and capacity principle of lithium batteries is relatively complicated, but it is also a very important process that affects battery performance, because when Li+ is charged for the first time, Li+ is inserted into graphite for the first time, and electrochemical reactions will occur in the battery. During the first charging process of the battery, it is inevitable to form a passivation film or SEI film (solid electrolyte interface, solid electrolyte interface (film)) covering the surface of the carbon electrode on the phase interface between the carbon negative electrode and the electrolyte. The performance of the SEI film directly determines the performance of the battery such as rate and self-discharge. In order to stabilize the state of the battery, it is usually necessary to charge and discharge multiple times, and to stand at a constant temperature below 60°C during the process of volume formation. Lithium battery composition and capacity system can charge single lithium battery with constant current. When the voltage reaches the charging upper limit voltage of lithium battery, it will switch to constant voltage charging until the charging current gradually drops to 0. Then discharge the battery at a constant current until the battery voltage reaches the discharge cut-off voltage.

Formation and grading are slightly different in principle, but both can be completed by charging and discharging motors. Formation is only a charging process, and there is no need to discharge the battery cells, so a separate charger can be used during formation, so the charger is often called a formation machine, because the appearance of the charger is often in the form of a square cabinet, Although the formation does not require discharge, the formation process of some cells requires more than one charge, followed by the capacity separation process after formation, which requires charging and then discharging the cells. After formating and charging, the cells must also be discharged. This technological need has also led many battery manufacturers to directly use a charge-discharge machine with charge and discharge functions for formation.