Laser Displacement Sensor for Online Thickness Measurement of Lithium Battery Electrodes After Roll Pressing

Measurement Solution

Industry Background In the manufacturing process of new energy lithium batteries, the consistency of electrode thickness directly affects battery capacity, internal resistance, and safety. The rolling process is a crucial step in electrode compaction; online thickness detection provides real-time feedback on the compaction effect, preventing defective products from entering subsequent processes. Traditional contact measurements easily damage the electrode surface and are unsuitable for high-speed production lines. Non-contact laser displacement sensors have become the mainstream solution. Detection Requirements Detection Object: The thickness of lithium battery positive and negative electrode sheets (coated with copper/aluminum foil) after rolling. Detection Purpose: To monitor in real-time whether the thickness is within the process tolerance range, providing feedback to adjust the rolling gap and improve yield. Accuracy Requirements: Typically, the thickness tolerance is ±2~5μm, and the sensor repeatability must be better than 1μm. Speed ​​Requirements: Production line speeds can reach 30~80m/min, and the sensor sampling frequency must be ≥10kHz. Measurement Challenges Highly Reflective Surfaces: Copper and aluminum foil surfaces have strong reflectivity, easily causing diffuse reflection interference. Sensors with strong anti-reflective capabilities or adjustments to the installation angle are required. High-speed motion: When the electrode moves at high speed, the sensor needs to have high-speed sampling capability to avoid measurement point misalignment. Environmental interference: Oil mist and vibration exist in the roller pressing workshop, so the sensor needs to have anti-interference capabilities. Limited installation space for double-sided laser beams: The internal space of the roller pressing machine is compact, so the sensor size needs to be small. Recommended sensor solution: We recommend using the ST-P series laser displacement sensor, which is based on laser triangulation for non-contact measurement and is suitable for high-reflectivity, high-speed scenarios. Based on the required detection distance and accuracy, the following models are available: 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 ST-P150 | Detection Range: 150mm ± 40mm | Repeatability: 1.2μm | Linearity Error: < ± 16μm For electrode thickness detection, a dual-probe, through-beam thickness measurement method is typically used: one sensor is installed at the top and one at the bottom, measuring the distance from the top and bottom surfaces of the electrode to the sensors respectively. The thickness is obtained by calculating the difference. Alternatively, a reference plane height difference measurement can be used: one sensor measures the electrode surface, and the other measures a fixed reference plane; the thickness is calculated by the height difference. Implementation Method Installation Location: The sensor is installed at the outlet of the roller press, in the stable operating area of ​​the electrode sheet, avoiding the influence of vibration. Installation Method: Use a dedicated bracket to fix the sensor, ensuring the optical axis is perpendicular to the electrode sheet surface. For dual-probe, opposite-beam installations, the optical axes of the upper and lower sensors must be coaxial. Signal Output: The ST-P series supports Ethernet, RS485, analog, and IO signal outputs, which can be connected to a PLC, host computer, or roller press control system to achieve real-time feedback and closed-loop control. Sampling Frequency: Up to 160kHz, meeting the needs of high-speed production lines. Selection Considerations Measurement Range: Must cover the electrode sheet thickness variation range (typically 50~200μm), with a margin of safety. Repeatability: Must be better than the process tolerance; it is recommended to choose a model with a repeatability of ≤0.5μm (such as ST-P30 or ST-P50). Anti-reflective Ability: Copper foil and aluminum foil surfaces have strong reflectivity; on-site testing and verification of the sensor's adaptability to highly reflective materials are required. Environmental Adaptability: The sensor should have an IP67 protection rating, suitable for environments with oil mist and dust. Application Value: Improved Yield: Real-time thickness monitoring allows for timely adjustment of rolling parameters, reducing defective products. Non-Contact and Non-Destructive: Avoids scratching the electrode sheet, suitable for fragile surfaces after coating. High-Speed ​​Online Inspection: Supports high-speed production lines without affecting production efficiency. Data Traceability: Data output via Ethernet can be integrated into an MES system for quality traceability. Precautions: For highly reflective materials such as copper foil and aluminum foil, on-site testing is recommended before installation to verify the sensor's measurement stability at different angles. When installing dual-probe, ensure that the upper and lower sensors trigger synchronously to avoid measurement errors due to time differences. Regularly clean the sensor lens to prevent oil and dust from affecting measurement accuracy. Sensor parameters (such as repeatability and linearity error) need to be confirmed according to the specific model, as different models have different performance characteristics.