The assembly of battery cells is the intermediate process of lithium batteries, which combines the processed positive and negative electrode plates and separators into the main body of the battery cell, and then completes the precision machining process of shell insertion, welding, liquid injection, and pre sealing. The mainstream routes are divided into two types: winding process and stacking process.
The winding process is commonly used for cylindrical batteries and square aluminum shell batteries. The equipment sequentially feeds the negative electrode sheet, separator, and positive electrode sheet, following the layout logic of negative electrode covering positive electrode, and continuously winding to form a core. The diaphragm isolates the positive and negative electrodes, allowing lithium ions to pass through while avoiding direct contact between the positive and negative electrodes. The winding process requires stable control of tension to prevent pole stretching, misalignment, and wrinkling.
The stacking process is commonly used for soft pack batteries and some square batteries, using a Z-shaped alternating stacking method, with a separator separating the positive and negative electrodes of a single piece back and forth. The laminated structure has better space utilization and lower internal resistance of the battery cells, making it suitable for high rate and high energy density products. However, the equipment speed is relatively slower than winding, and higher positioning accuracy is required.
After the core winding/stacking is formed, it enters the shell insertion process: square cells are inserted into aluminum shells, soft pack cells are encapsulated in aluminum-plastic films, and cylindrical cells are inserted into steel shells. Subsequently, perform pole ear welding to connect the pole ear to the shell cover or lead out terminal, ensuring stable conductive path. Welding virtual welding and explosion points can cause abnormal internal resistance.
After welding, the battery cell needs to be vacuum baked to reduce the internal moisture content. Afterwards, the electrolyte is quantitatively injected in a low dew point environment, and the electrolyte infiltrates the pores of the electrode and diaphragm to build a lithium-ion transport medium. After the injection is completed, the sealing is completed to form an inactive battery cell to be formed. The entire assembly workshop needs to strictly control moisture and dust, as excessive moisture can cause long-term performance degradation of the battery cells.
