As the current mainstream energy storage device, the fine control of its manufacturing process directly affects the performance, service life and safety of the battery. In the manufacturing process of lithium battery, the process control technology of key processes such as coating, lamination, slitting, formation and volume separation is particularly important. This article will focus on these processes and analyze the key points of process control and technical requirements in detail, aiming to provide reference for lithium battery production.

I. Coating process control technology

the coating process is the first step in the manufacture of lithium batteries, mainly by evenly coating the electrode slurry on the collecting fluid (such as copper foil or aluminum foil) to form electrode plate. The quality of coating process directly affects the battery capacity and consistency.

1. Control of coating uniformity

uniformity of coating is the basis to ensure stable battery performance. High-precision coating equipment such as Groove roller coating machine and Blade coater coating machine are adopted to realize uniform distribution of slurry thickness by adjusting coating speed, knife gap and slurry viscosity. The coating thickness is generally controlled within ± 3cm to avoid capacity differences caused by uneven thickness.

2. Slurry formulation and viscosity control

the component proportion and viscosity of the slurry have significant influence on the coating quality. Reasonable proportion of active materials, conductive agents and adhesionBinder to ensure good fluidity and adhesion of slurry. The viscosity is controlled within a certain range (usually 1000-5000 mPa · s), which not only ensures the leveling effect during coating, but also prevents the slurry from flowing.

3. Drying process parameters

the coated electrode plate needs to be dried remove solvent. The control of drying temperature and time is very important. If the temperature is too high, the binder may decompose. If the temperature is too low, the drying is not complete. Generally, the drying temperature is controlled at 80-120 ℃, and the drying time is adjusted according to the coating thickness to ensure that there is no solvent residue on the surface of electrode plate.

II. Lamination process control technology

lamination is the process of accurately superimposing positive and negative electrode pieces and diaphragm according to the design sequence to form cell. Lamination the process is related to the integrity and safety of the internal structure of the battery.

1. Lamination accuracy and alignment

during the lamination process, ensure that the alignment error of each layer of material is controlled within ± 0.1mm to avoid electrode edge exposure or poor overlap, and prevent the risk of short circuit. Automatic lamination equipment and visual positioning technology are adopted to improve the accuracy and consistency of lamination.

2. Pressure and tension controlLamination the pressure and tension in the process need to be adjusted reasonably. Excessive pressure may damage the electrode material, causing the active substance to fall off; If it is too small, the lamination is not tight, which affects the internal resistance of the battery. Tension control helps keep the material flat and prevents wrinkles and offset.

3. Environmental cleanliness

lamination the environment should be kept clean to prevent dust and foreign matters from entering the interior of the cell, otherwise the battery performance will decline or even safety accidents will occur. Generally, lamination workshop is required to meet ISO Level 7 or higher cleaning standards.

III. Slitting process control technology

slitting is the process of cutting the coated electrode plate into a size suitable for lamination according to specifications. Process control has higher requirements on electrode size accuracy and edge quality.

1. Tool selection and maintenance

high-precision slitting tools, such as circular knife or straight knives, are adopted to ensure smooth cutting edges without burrs. Cutting tools need to be replaced or sharpened regularly to avoid poor cutting caused by blade passivation.

2. Fine cutting sizeDegree

the size error of slitting shall be controlled within ± 0.1mm to ensure that the materials of each layer are well matched during the subsequent lamination, so as to avoid assembly difficulties and performance problems caused by too large or too small electrode plate.

3. Process stability monitoring

through the online detection system, the cutting size and edge quality are monitored in real time, and the equipment parameters are adjusted in time to ensure the continuous and stable cutting process.

IV. Formation Process Control Technology

formation is a key link in the manufacture of lithium batteries. Through charging and discharging, the electrochemical reaction inside the battery is activated to form a stable solid electrolyte interface (SEI) film.

1. Current and voltage control

the formation process usually adopts constant current and constant voltage charging mode, and the charging current and cut-off voltage need to be accurately controlled. Excessive current may cause excessive battery heating, and if it is too low, the production cycle will be prolonged. The cut-off voltage is generally controlled at about 4.2V to prevent overcharging.

2. TemperatureManagement

the temperature of the battery changes significantly during the formation process. It is necessary to cooperate with the cooling system to keep the temperature in the range of 20-40℃ to avoid potential safety hazards caused by too high temperature or SEI film formation caused by too low temperature.

3. Formation curve monitoring

by monitoring voltage, current and temperature curves, abnormal batteries can be found in time, such as excessive internal resistance or abnormal capacity, to ensure the quality control of the formation process.

V. Separation process control technology

capacity separation is an important link in capacity detection and classification of completed batteries, which directly affects battery Assembly consistency and performance.

1. Capacity test standard

constant current discharge or constant power discharge method is adopted to measure the battery capacity, and the discharge cut-off voltage is generally set to 2.5-3.0V to ensure accurate capacity measurement. The capacity distribution equipment must have high precision current and voltage collection capability.

2. Consistency sorting

according to the test results, the battery is divided into multiple levels to ensure that the difference between the capacity and internal resistance of the battery of the same level is as small as possible, and the overall performance and service life of the battery pack are improved.

3. Data management and traceability

A large amount of data is generated during the separation process. A complete data collection and management system needs to be established to realize the tracing and quality analysis of battery performance and support subsequent production optimization.

Each link of the lithium battery manufacturing process is of great importance. The process control technology of key processes such as coating, lamination, slitting, formation and volume separation is the basis for ensuring stable performance, safety and reliability of lithium batteries. By strictly controlling process parameters, adopting advanced equipment and real-time monitoring technology, the product quality can be effectively improved to meet the market demand for high-performance lithium batteries.