How can the precise spacing between the positive and negative terminals be ensured in button battery manufacturing to reduce internal resistance loss?
Release Time : 2026-01-21
In the manufacturing process of button batteries, ensuring the precise spacing between the positive and negative electrodes is crucial for reducing internal resistance losses and improving battery performance. Even slight deviations in the electrode spacing directly increase the battery's internal resistance, thus affecting energy efficiency, power output, and cycle life. Achieving this goal requires a comprehensive approach encompassing material selection, structural design, process control, and quality inspection.
First, material selection is fundamental. The physical properties of the positive and negative electrode materials, such as thickness, density, and surface smoothness, directly impact the precision of spacing control. For example, uneven thickness or particle agglomeration in the positive electrode active material layer can lead to localized protrusions, creating gaps when the negative electrode contacts it. Therefore, optimizing the slurry formulation and improving the coating process (such as using slot extrusion coating) are necessary to ensure consistent electrode thickness. Simultaneously, the surface treatment technology of the negative electrode material (such as lithium metal or graphite) also needs attention to avoid poor localized contact due to excessive roughness.
Structural design must balance functionality and precision. In the stacked or wound structure of button batteries, the lamination sequence and tension control of the positive and negative electrodes and the separator are critical. As an insulating layer, the thickness uniformity of the separator directly affects the spacing between the positive and negative electrodes. If the separator has wrinkles or thickness fluctuations, even if the electrodes themselves are flat, the final spacing will deviate from the design value. Therefore, high-precision separator materials must be selected, and wrinkles must be eliminated through hot pressing. Simultaneously, the tension control system of the winding or stacking equipment must be optimized to ensure that each layer is tightly bonded without stretching deformation.
Process control is crucial for precise spacing. During assembly, the coaxiality of the positive and negative electrode shells and the positioning accuracy of the electrodes and shells must be ensured through high-precision molds and automated equipment. For example, using a vision positioning system to guide a robotic arm to grasp the electrodes can reduce human error; the stamping process of the shells needs to control the burr height to avoid burrs piercing the separator and causing short circuits or abnormal spacing. Furthermore, the electrolyte injection amount also needs precise control; excessive electrolyte may cause the battery to expand, compressing the spacing between the positive and negative electrodes; insufficient electrolyte may increase internal resistance due to poor ion conduction.
Quality inspection must be carried out throughout the entire process. During electrode fabrication, laser profilometers or micrometers are used to check thickness uniformity. During assembly, X-ray imaging or ultrasonic scanning can be used to inspect the internal structure and verify that the spacing between the positive and negative electrodes meets design requirements. Finished batteries also require internal resistance testing to screen out products with excessive internal resistance and trace the issue back to specific processes for improvement. For example, if a batch of batteries generally has high internal resistance, it may be necessary to check whether the separator thickness or assembly pressure meets standards.
Environmental control is also crucial. Button battery manufacturing must be carried out in a dry room or glove box to prevent moisture or impurities from entering. Excessive humidity can cause the electrodes to absorb moisture and expand, altering the spacing between the positive and negative electrodes; while dust particles embedded between the electrodes can create localized short circuits or increase contact resistance. Therefore, a clean environment must be maintained through dehumidification equipment, air purification systems, and proper personnel attire (such as anti-static clothing and gloves).
Furthermore, simulation technology can assist in design optimization. By creating a three-dimensional battery model and simulating current distribution and internal resistance changes under different spacings, potential problems can be identified in advance. For example, simulations may show excessively high current density in the edge region of a design, possibly due to excessive spacing. In this case, adjusting the electrode shape or housing structure can improve uniformity.
Finally, continuous improvement relies on data-driven approaches. Key parameters from the production process (such as electrode thickness, assembly pressure, and internal resistance test values) should be collected and a database established. Statistical analysis can then identify the main factors affecting spacing accuracy, leading to optimization of process parameters or equipment settings. For instance, if data analysis indicates a high correlation between tension fluctuations and excessive internal resistance on a winding machine, the equipment can be calibrated or maintained.