Laser Displacement Sensor for Step Detection at Electrode Tab Joints in Lithium Battery Production

Measurement Solution

Industry Background In the manufacturing process of new energy lithium batteries, the coating, rolling, slitting, and winding processes of electrode sheets (positive and negative electrodes) require extremely high dimensional accuracy. The height difference at the electrode joint (i.e., the electrode connector) directly affects the yield of subsequent winding or stacking processes. Excessive height difference can lead to stress concentration within the cell and an increased risk of short circuits. Therefore, online, non-contact, high-precision height difference detection at the joint has become a critical quality control step in the lithium battery industry. Detection Requirements Detection Object: The height difference at the electrode joint (electrode connector) of lithium electrode sheets, including positive electrode sheets (aluminum foil + active material) and negative electrode sheets (copper foil + active material). Detection Purpose: To measure the height difference between the upper and lower electrode layers at the joint in real time, ensuring that the height difference is within the allowable range of the process (usually required to be <50μm), and avoiding defects in subsequent processes due to excessive height difference. Detection Environment: Production line speeds are typically 10-60 m/min. Electrode surfaces may exhibit reflectivity (copper foil, aluminum foil), color differences (black negative electrode, light-colored positive electrode), and slight vibrations. Measurement Challenges: Highly Reflective Surfaces: Copper and aluminum foils strongly reflect laser light, easily causing sensor saturation or measurement deviations. High-Speed ​​Movement: High production line speeds require sensors with high-speed sampling capabilities (≥10 kHz) to capture instantaneous step differences. Small Step Differences: Step differences are typically on the order of tens of micrometers, requiring sensor repeatability better than 1 μm. Material Color Differences: The positive electrode (light-colored) and negative electrode (dark-colored) have different laser absorption rates, requiring sensors with good surface adaptability. Recommended Sensor Solution: The ST-P series laser displacement sensor uses laser triangulation for non-contact measurement and is suitable for lithium electrode step difference detection. Based on the required detection distance and accuracy, the following models are recommended: Model | Reference Distance | Measurement Range | Repeatability | Linearity Error ST-P30 | Detection range 30mm±5mm, Repeatability 0.15μm, Linearity error <±3μm ST-P50 | Detection range 50mm±10mm, Repeatability 0.25μm, Linearity error <±4μm ST-P80 | Detection range 80mm±15mm, Repeatability 0.5μm, Linearity error <±6μm For electrode joint step difference detection, ST-P30 or ST-P50 is typically selected, as its repeatability can reach sub-micron level, meeting high precision requirements. The sensor's maximum sampling frequency is 160kHz, suitable for high-speed production lines. Implementation Method: Use a dual-probe through-beam thickness measurement method or a reference surface height difference measurement method: Dual-probe through-beam: Install one ST-P series sensor on each of the upper and lower sides of the electrode, simultaneously measuring the distance between the upper and lower surfaces of the electrode, and calculating the electrode thickness using the difference. The step difference at the splice location can be indirectly obtained by comparing the thickness change at the splice point with that of the normal area. Reference plane height difference: A single sensor is installed on one side of the electrode, using the roller or platform as the reference plane to measure the surface height of the electrode. The step difference at the splice location manifests as a sudden change in height. The sensor outputs signals via Ethernet, RS485, or analog signals to a PLC or host computer for real-time data acquisition and alarm. Selection considerations: Measurement range and distance: Select a model with appropriate reference distance and measurement range based on the installation space and electrode vibration amplitude. Surface adaptability: For highly reflective materials such as copper foil and aluminum foil, sensor performance needs to be verified through on-site testing. Adjusting the installation angle or using a polarizer may be necessary. Sampling frequency: The faster the production line speed, the higher the required sampling frequency. It is recommended that the sampling frequency not be lower than the spatial resolution requirement corresponding to the production line speed (m/min). Environmental factors: Dust and temperature variations may exist on-site; the sensor's protection level and temperature stability must be confirmed. Application Value Using the ST-P series laser displacement sensor for electrode splice step difference detection enables: * Non-contact measurement, avoiding damage to the electrode surface; * High-precision, high-speed online detection, providing real-time feedback of step difference data; * Data integration into the MES system, enabling quality traceability; * Reduced frequency of manual sampling inspections, improving production line automation. Precautions * During installation, ensure the sensor spot is aligned with the electrode splice area to avoid edge interference. For highly reflective materials, on-site sample testing is recommended to confirm sensor stability. Regularly clean the sensor lens to prevent dust from affecting measurement accuracy. Signal cables must be shielded to avoid electromagnetic interference.