Application of Laser Displacement Sensor in Height Runout Detection of Lithium Battery Electrode Sheet Conveying

Measurement Solution

Industry Background In the manufacturing process of new energy lithium batteries, the coating, rolling, slitting, and stacking/winding processes of electrode sheets (positive and negative electrodes) require extremely high dimensional accuracy. Parameters such as electrode thickness, height runout, edge warping, and step difference directly affect cell capacity, internal resistance, safety, and consistency. Traditional contact-based measurements easily damage the electrode surface and are unsuitable for high-speed production lines. Laser displacement sensors, with their advantages of non-contact operation, high precision, and high-speed response, have become key components for online lithium battery testing. Testing Requirements During the lithium electrode sheet transport process, the following parameters need to be monitored in real time: * **Electrode Height Runout:** As the electrode sheets move on the conveyor rollers, roller runout, electrode tension fluctuations, and uneven coating cause the electrodes to fluctuate up and down. The amount of runout needs to be measured to determine coating uniformity and rolling quality. * **Electrode Thickness:** The consistency of electrode thickness after coating and rolling is typically measured using a dual-probe beam or a reference surface height difference method. * **Coating Step Difference:** The height difference between the coated edge and the uncoated area of ​​the electrode sheet reflects the coating edge effect. Edge warping: Warping of the electrode edges due to stress or uneven drying. Cell bulging: The height of bulges on the cell surface after encapsulation, affecting battery assembly. Measurement challenges: Highly reflective materials: Copper and aluminum foil surfaces are highly reflective, easily causing sensor signal saturation or loss. High-speed production lines: Electrode conveying speeds can reach tens of meters per minute, requiring high sensor sampling frequency and fast response. Miniature dimensions: Electrode thickness is typically tens to hundreds of micrometers, with fluctuations possibly only a few micrometers, requiring sub-micrometer repeatability from the sensor. Environmental interference: Production line vibration, dust, and temperature changes affect measurement stability. Recommended sensor solution: The ST-P series laser displacement sensor uses laser triangulation for non-contact measurement, suitable for lithium electrode sheet and cell detection. 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... Measurement range 150mm±40mm, repeatability 1.2μm, linear error <±16μm ST-P400, measurement range 400mm±100mm, repeatability 3μm, linear error <±600μm ST-P450, measurement range 450mm±250mm, repeatability 8μm, linear error <±250μm. Maximum sampling frequency up to 160kHz, supports Ethernet, RS485, analog and IO signal outputs, and can be connected to PLCs, host computers, etc. Implementation Methods: For electrode height runout detection, the following installation methods are commonly used: Single Probe Measurement: The sensor is vertically aligned with the electrode surface, measuring the distance change of the electrode relative to a fixed reference. Suitable for runout detection. Dual Probe Thickness Measurement: Two sensors are used opposite each other, measuring the distance from the upper and lower surfaces of the electrode to their respective sensors. The thickness is calculated by the difference, eliminating reference plane error. Reference Plane Height Difference: One sensor measures the electrode surface, and the other measures a reference plane. The height difference is calculated. The sensor is fixed above the conveyor roller by a bracket. During installation, ensure the laser spot is perpendicular to the incident light to avoid measurement errors caused by excessive tilt angle. For highly reflective materials (copper foil, aluminum foil), it is recommended to adjust the sensor installation angle or use a polarizing filter, and conduct on-site testing and verification. Selection Considerations: * Measurement Range and Accuracy: Select the appropriate model based on the electrode thickness and runout. For example, if the electrode thickness is ≤200μm and the runout is ±50μm, ST-P30 or ST-P50 can be selected. Sampling Frequency: The higher the production line speed, the higher the required sampling frequency. The ST-P series has a maximum frequency of 160kHz, which can meet the needs of high-speed production lines. Output Interface: Select Ethernet, RS485, or analog output according to the control system for easy integration. Environmental Adaptability: Consider factors such as on-site temperature, humidity, and dust. If necessary, install a protective cover or air blowing device. Application Value: * Non-contact Measurement: Avoids scratching the electrode, suitable for soft and fragile materials. High Precision: Repeatability up to 0.15μm, meeting the micron-level detection requirements of the lithium battery industry. High-Speed ​​Response: 160kHz sampling frequency supports online real-time detection, improving production line efficiency. Multi-Interface Compatibility: Facilitates integration with PLCs, host computers, and MES systems for data traceability. Precautions: For highly reflective materials such as copper and aluminum foil, on-site testing and verification are required based on surface reflectivity, color, speed, and installation angle. Adjusting sensor parameters or adding accessories may be necessary. When using dual-probe thickness measurement, ensure the upper and lower sensor optical axes are coaxial to avoid angular deviations. The sensor installation location should avoid direct sunlight and vibration sources. Clean the lens regularly. Specific model parameters should be confirmed based on the actual application scenario. It is recommended to contact the manufacturer for detailed technical solutions.