Formation and grading machines are key equipment in the lithium battery production process. They are mainly used to perform formation and capacity grading operations on lithium-ion cells.
1. Definition of Formation and Grading
Formation: After assembly, a lithium-ion battery has no electrical charge. It must undergo an initial charge to activate the active materials inside the cell. This process is called formation or activation. During formation, a solid electrolyte interphase (SEI) film forms at the interface between the carbon anode and the electrolyte. This film allows only lithium ions to pass through and does not dissolve in organic solvents, effectively protecting the electrode from electrolyte erosion and improving cycle performance and service life.
Grading: Grading is the process of charging and discharging the battery to determine its actual capacity by measuring the discharge capacity at full charge. Only cells whose tested capacity meets or exceeds the design capacity are considered qualified. Grading can be understood as capacity sorting and performance classification, and it is an essential step in screening qualified cells.
2. Working Principle of Formation and Grading Machines
A formation and grading machine mainly consists of a charging power unit, a needle bed unit, a temperature control unit for formation equipment or an electrical control unit for grading equipment, and background monitoring software.
Charging power unit: Provides the charging energy required for formation or grading. For formation equipment, the power unit typically includes AC-DC and DC-DC modules that convert AC power into DC power suitable for battery charging. For grading equipment, the power unit provides stable charging current and voltage according to grading process requirements.
Needle bed unit: Used to hold and connect the cells, ensuring stable charging and discharging during formation or grading. The needle bed design must consider cell size, tab position, and other factors to ensure good contact and conductivity. For non-standard needle bed fixtures, custom contact probes, or precision structural components used in these machines, Hansheng Automation provides custom machining services based on customer drawings and required tolerances, helping maintain reliable electrical contact and stable positioning during high-volume cell processing.
Temperature control unit (for formation equipment): Controls the temperature environment during formation. A high-temperature negative-pressure environment supports SEI film formation and stable cell performance. The temperature control unit uses heating and insulation functions to maintain the formation process within the set temperature range.
Electrical control unit (for grading equipment): Controls charge and discharge parameters during grading, such as current, voltage, and time. It uses precise control algorithms to ensure grading accuracy and stability.
Background monitoring software: Provides real-time monitoring and data management for formation and grading processes. Functions include process editing, real-time data display and control, data file management, and remote monitoring, enabling operators to precisely control the process and analyze data.
3. Selection of Formation and Grading Machines
When selecting a specific formation and grading machine, the following factors should be considered:
Capacity requirements: Determine the required throughput based on the customer's production scale.
Formation and grading specifications: Voltage, current, and other parameters should be selected according to battery type and process requirements.
Product specifications: Cell dimensions, tab conditions, and other physical characteristics must be compatible with the equipment.
Technical requirements: Voltage and current accuracy, charge-discharge efficiency, temperature precision, and contact impedance should meet process and product quality standards.
In summary, formation and grading machines are indispensable in lithium battery manufacturing. Their performance and quality directly affect battery performance and final product quality. When selecting such equipment, capacity requirements, process specifications, product compatibility, and technical requirements should be considered together to ensure equipment suitability and reliability.
