The thickness of positive and negative electrode sheets (electrode plates) for lithium-ion batteries is measured with high accuracy using a laser displacement sensor. By measuring the thickness of the running sheet in real time during each process after coating and pressing, this supports quality control for battery capacity and safety.
Inquiries regarding thickness measurement
Why Is Electrode Plate Thickness Measurement Important?
Compare welding inspection methods across detection targets, accuracy, speed, cost, and suitability for automation.
Uniform Battery Capacity
The coating amount of active materials on the positive and negative electrodes directly affects the thickness of the electrode plates. If the thickness is uneven, variations in capacity occur from cell to cell, and the performance of the entire module is limited by the weakest cell. By measuring the thickness of every electrode plate inline, the stability of the coating process can be determined immediately.
Ensuring Safety
If the coating thickness of the active material becomes locally excessive, lithium deposition is likely to occur during charging and discharging, causing internal short circuits. Electrode plate thickness control is particularly demanding for EV batteries, requiring quality assurance on the micrometer scale.
Improving Yield Rate and Reducing Costs
With offline sample extraction measurement, detection of defects is delayed, resulting in a large amount of waste loss. Real-time inline measurement of electrode plate thickness allows for immediate feedback when an abnormality occurs, minimizing material loss.
Battery Electrode Manufacturing Process and Thickness Measurement Points
Electrode plate thickness measurement is performed at multiple steps in the manufacturing process. The target to be measured and the required accuracy and speed differ for each step.
- 1 Mixing and blending – Mix active materials, binders, and conductive agents
- 2 Coating – Thickness measurement (1). Apply slurry onto the current collector (foil)
- 3 Rolling (pressing) – Thickness measurement (2). Compress to target density with a roll press
- 4 Slitting and winding – Cut to desired width and wind as an electrode roll
Comparing Electrode Plate Thickness Measurement Methods
There are multiple methods for measuring electrode plate thickness. The optimal method is selected by comprehensively comparing measurement accuracy, speed, cost, and maintainability.
Inline compatibility
Laser displacement sensor (non-contact optical type)
◎ Supported
Contact-type micrometers, etc.
△ Difficult (sample extraction)
Beta-ray method
◎ Supported
Effect on electrode plates
Laser displacement sensor (non-contact optical type)
◎ Non-contact
Contact-type micrometers, etc.
△ Risk of scratches from contact
Beta-ray method
◎ Non-contact
Regulations and safety management
Laser displacement sensor (non-contact optical type)
◎ Not required
Contact-type micrometers, etc.
◎ Not required
Beta-ray method
△ Radiation control required
Maintenance
Laser displacement sensor (non-contact optical type)
◎ Virtually no maintenance required
Contact-type micrometers, etc.
○ Regular calibration
Beta-ray method
△ Source replacement required
Initial cost
Laser displacement sensor (non-contact optical type)
○ Medium to high
Contact-type micrometers, etc.
◎ Low cost
Beta-ray method
△ High cost
Summary of Method Selection
Contact methods are highly accurate but unsuitable for inline use, posing a risk of scratching the electrode plates after pressing. Beta-ray methods have a proven track record in inline measurement, but the management costs of radiation sources and compliance with laws and regulations are burdensome. Laser displacement sensors combine non-contact, high-speed, and high-accuracy capabilities and are not subject to regulatory requirements, making them the most popular choice for building new lines or replacing existing ones.
Best Products for Electrode Plate Thickness Measurement
KEYENCE offers products that support electrode plate thickness measurement. We propose the optimal configuration according to the measurement target and process.
Most Commonly Used for Thickness Measurement — CL-3000 Series
Confocal Displacement Sensor
The white-light confocal method enables stable thickness measurement regardless of the surface condition (gloss/roughness) of the electrode plate. Two sensor heads sandwich the electrode sheet to measure the total thickness of the running electrode plate in real time. A dedicated jig that is highly resistant to temperature changes achieves stable measurement over long periods.
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Case Studies of Thickness Measurement in Battery Production Lines
Here are examples of thickness measurement using laser displacement sensors at various battery manufacturers.
Foil Thickness Measurement
Measures the thickness of aluminum foil and copper foil. To adjust the coating amount, the coating thickness alone is calculated from the thicknesses of the coated electrode and the foil itself. By preparing a dedicated jig for properly installing the upper and lower sensor heads and reducing errors caused by optical axis misalignment, simple and highly accurate measurement is possible.
Electrode Thickness Measurement After Coating
Measures the thickness of the electrode. To adjust the coating amount, the thickness of the coated electrode alone is calculated from the thicknesses of the coated electrode and the foil itself. By preparing a dedicated jig for properly installing the upper and lower sensor heads and reducing errors caused by optical axis misalignment, simple and highly accurate measurement is possible.
Monitoring Electrode Thickness During Drying
With the CL-V020, which has heat resistance up to 200°C, changes in electrode thickness inside the drying furnace can be captured. Analyzing these changes together with the drying furnace temperature and conveyance speed leads to energy savings.
Electrode Thickness Measurement After Drying
Measures the electrode thickness immediately after drying with high accuracy. By comparing the electrode thickness before and after pressing, optimal press control is possible. With the CL-S015, which features an athermal design, stable measurement is possible over a long period without being affected by heat generated from the drying furnace or electrodes.
Stacked Cell Thickness Measurement (Pouch Type)
Measures the thickness of cells. Previously, inspections were performed using contact-type measuring instruments, but switching to a laser displacement sensor has shortened measurement time and eliminated concerns about scratching the workpiece.
Thickness Measurement of Long-Side Seal (Pouch Type)
Measures the thickness of the sealed part of pouch-type cells. Stable measurement is possible without being affected by the material or color of the target object, or workpiece deflection.
Frequently Asked Questions About Electrode Plate Thickness Measurement
The main methods are contact methods (micrometers, thickness gauges), beta-ray methods (radiation type), and non-contact optical methods using laser displacement sensors. Laser displacement sensors are best suited for high-speed, high-accuracy inline electrode plate thickness measurement.
Measurement in both processes is recommended. After coating, the uniformity of the coating amount (film thickness) is checked, and after rolling (pressing), the final electrode plate thickness and achievement of the target density are checked. Managing both sets of data leads to stable operation of the entire process.
For lithium-ion battery electrode sheets, the electrode plate thickness tolerance after pressing is generally controlled to around ±2 to 5 μm. To stably guarantee this, a repeatability of 0.5 μm or less, preferably 0.1 μm or less, is required for the measuring instrument.
Yes. By installing two laser displacement sensors above and below to sandwich the electrode sheet, the thickness of the electrode plate can be measured in real time during conveyance. The CL-3000 Series supports sampling at a maximum speed of 10 kHz, enabling reliable data acquisition even on high-speed production lines.
Many customers have replaced beta-ray gauges with laser displacement sensors. Because radiation source management is no longer required, running costs and the burden of regulatory compliance are significantly reduced. Retrofitting to existing lines is also possible.
- Confocal Displacement Sensor CL-3000 series
Confocal Displacement Sensor
CL-3000 series
