Lithium-ion battery manufacturing processes and the latest technologies
Lithium-ion batteries are a top-priority technology for both achieving automobile electrification and making renewable energy a core power source. We are also focusing on facilitating the spread of lithium-ion batteries to respond to the rapidly expanding market. As the production capacity expands, there is ongoing technological innovation aimed at increasing the energy density, boosting the charging speed, extending the life, and ensuring the safety of lithium-ion batteries, and battery manufacturers are continuing to evolve as they strive to simultaneously achieve technological innovation and adapt to the market.
This article explains the lithium-ion battery manufacturing process, quality control, and the latest technologies.
Overall flow of the lithium-ion battery manufacturing process
The lithium-ion battery manufacturing process involves multiple important steps. The first step is to prepare and select raw materials so as to secure high-quality materials. Next, the electrode sheet is completed during a series of processes that include cathode and anode material mixing, uniform application of this material to aluminum and copper foil, drying, and compression.
It is important to do this work in a dry room. This work must be done in a humidity-controlled environment to prevent both degradation due to water and contamination by impurities, thereby ensuring safety and improving performance.
Electrode sheets are formed into a roll shape, separators are sandwiched between them, and each is sealed as one cell.
The final step is to conduct a charging and discharging test, inspect the quality, remove any defective products, and confirm that the performance is optimal.
The manufacturing process is used to produce lithium-ion batteries that offer high performance and safety, but there are still issues related to products lighting on fire or emitting smoke, so efforts are also underway to develop technologies to respond to this.
Lithium-ion battery manufacturing-process procedures and details
Lithium-ion battery manufacturing can be broadly divided into the three processes below.
・ Electrode manufacturing process: creating sheet-shaped cathode and anode materials from raw materials and then winding it into a roll shape
・ Cell assembly process: stacking cathode and anode materials with a separator and then packaging the result
・ Inspection process: testing the charging and discharging of completed batteries and identifying defective products
Discover more about each process.
Electrode manufacturing processes
Creating sheet-shaped cathode and anode materials from raw materials and then winding it into a roll shape
| # | Process | Description |
|---|---|---|
| (1) | Mixing (kneading) | Battery materials (cathode and anode materials) are mixed and stirred so that they can be used to apply an even coat. |
| (2) | Coating and drying | The battery materials mixed in (1) are used to evenly coat the cathode material (aluminum foil) and anode material (copper foil), and then the result is dried. The cathode and anode materials are then wound into a roll shape. |
| (3) | Pressing | The cathode and anode materials are compressed using a roller to the desired density (thickness). After compression, the result is once again wound into a roll shape. |
| (4) | Slitter | After the pressing in (3), the roll-shaped cathode and anode materials are individually cut to a certain roll width using a cutter. |
Cell assembly processes
Stacking cathode material, anode material, and separators and then packaging them
| # | Process | Description |
|---|---|---|
| (5) | Electrode cutting and stacking | Sheets of cathode material and anode material cut out of the rolls are stacked with separators sandwiched between them. |
| (6) | Tab welding | Current collector tabs are attached to the stacked electrodes. |
| (7) | Sealing | The stacked electrodes (stacked elements) manufactured up through step (6) are sealed to laminated film that consists of aluminum foil and resin held together with a coat of adhesive. |
| (8) | Injection | The electrolyte is injected into the injection port of the sealed laminated film. |
| (9) | Final degassing and sealing | Depending on the materials in the battery, post-injection charging sometimes results in swelling. In this case, the battery is degassed, resealed, and then charged again. |
Inspection processes
Testing the charging and discharging of completed batteries and identifying defective products
| # | Process | Description |
|---|---|---|
| (10) | Charging and discharging | The main charge is performed (normally up to the charging limit voltage) to check the initial discharge capacity. |
| (11) | Aging | To remove defective products, the initial degradation of each battery is examined to determine whether it is fit for shipment. The general approach for this determination is based on the battery’s initial voltage drop (due to self-discharge). |
Quality control during the lithium-ion battery manufacturing process
Key points related to quality control
Quality control is crucial during the lithium-ion battery manufacturing process. Selecting appropriate manufacturing equipment for each stage is essential to ensure safe structure creation. Precision is necessary for both individual parts and modules, which are combinations of parts.
Implementing suitable inspection and analytical systems at each stage helps identify contamination and other causes of heat and fire, ensuring battery quality. Due to the risk of fires and explosions from manufacturing defects, regulatory authorities worldwide are tightening regulations related to the production, transportation, and use of lithium-ion batteries. Companies are responding by enhancing quality control and developing technologies to ensure safety.
Choosing the right manufacturing equipment, along with effective inspection and analytical systems, not only enhances safety but also improves productivity and reduces CO2 emissions.
Latest technologies for the lithium-ion battery manufacturing process
Eliminating the risk of metal particle contamination, electrode deformation
To safely achieve the high energy density unique to lithium-ion batteries, it is important to eliminate the risk of metal particle and other contamination like electrode deformation.
Given that contamination of lithium-ion batteries is directly linked to reduced battery performance, safety, and yield, it is important to introduce a high-performance X-ray particle contaminant analyzer to detect contaminants at earlier stage of manufacturing process.
Our X-ray particle contaminant analyzer quickly detects and identifies the elements in 20 μm-class microscopic metal particle contaminants, which might cause problems in lithium-ion batteries. Just selecting inspection conditions and starting measurement automatically executes the process from capturing X-ray transmission images to detecting metal particle contaminants and identifying their elements.
Increased efficiency through dry room technologies
Dry room technologies play an important role in the lithium-ion battery manufacturing process. Contamination by water must be prevented during lithium-ion battery manufacturing. It is also necessary to pay attention to moisture in the air, and even a small amount of moisture can decrease the performance, so manufacturing must be done in an environment with almost 0% humidity. In addition, dry rooms contribute to reduced CO₂ emissions, so they are also attracting attention as part of the sustainable manufacturing process. The dry rooms provided by Hitachi High-Tech take advantage of competitively advantageous core technologies that include our moisture control technologies and CO₂ elimination technologies, and we also offer high-performance dry room designs—including the selection of highly airtight plumbing and building materials—to contribute to the achievement of high-efficiency, energy-saving lithium-ion battery manufacturing.
This article introduces the manufacturing process in detail and explains the latest technologies for quality control.
To manufacture high-quality lithium-ion batteries, it is necessary for each related process to be highly precise. Advancements are also being made in terms of improving productivity and considering the environment by introducing new technologies.
Going forward, our transition to sustainable manufacturing processes will be accelerated by the enhancement of waste management as well as recycling and reuse programs for production lines in general.