Lith Corporation, founded in 1998 by a group of material science doctor from Tsinghua University, has now become the leading manufacturer of battery lab&production equipment. Lith Corporation have production factories in shenzhen and xiamen of China.This allows for the possibility of providing high quality and low-cost precision machines for lab&production equipment,including: roller press, film coater,mixer, high-temperature furnace, glove box,and complete set of equipment for research of rechargeable battery materials. Simple to operate, low cost and commitment to our customers is our priority.
Cylindrical Cell Fabrication: A Comprehensive Guide
Cylindrical cells are a type of lithiumion battery housed in a cylindrical metal can. They are widely used in applications such as electric vehicles (EVs), consumer electronics, energy storage systems, and portable devices due to their robust design, high reliability, and ease of manufacturing. Below is a detailed guide on the fabrication process for cylindrical cells.
●What Are Cylindrical Cells?
Cylindrical cells are rechargeable batteries with a cylindrical shape, typically made using a steel or aluminum casing. The most common format is the 18650 (18mm diameter, 65mm height) cell, but other sizes like 21700 and 4680 are also gaining popularity, especially in electric vehicles.
Key features:
Robust metal casing provides structural integrity.
High production efficiency due to standardized designs.
Suitable for applications requiring high power density and durability.
●Key Components of Cylindrical Cells
To fabricate cylindrical cells, the following components are required:
1. Anode: The negative electrode, typically made of graphite or siliconbased materials.
2. Cathode: The positive electrode, commonly composed of lithium cobalt oxide (LiCoO₂), lithium iron phosphate (LiFePO₄), nickelmanganesecobalt (NMC), or nickelcobaltaluminum (NCA) blends.
3. Electrolyte: A liquid medium containing lithium salts dissolved in organic solvents to facilitate ion transport.
4. Separator: A porous polymer film (e.g., polyethylene or polypropylene) that prevents direct contact between the anode and cathode while allowing ion flow.
5. Current Collectors: Thin metal foils (aluminum for the cathode and copper for the anode) that collect and transfer electrons.
6. Metal Can: A cylindrical metal casing (steel or aluminum) that houses the cell components.
7. Top Cap and Safety Features: Includes venting mechanisms, pressuresensitive fuses, and other safety features to prevent overheating or explosion.
●Steps in Cylindrical Cell Fabrication
1. Material Preparation
Slurry Mixing:
Combine active materials (e.g., LiCoO₂ for the cathode or graphite for the anode), conductive additives (e.g., carbon black), and binders (e.g., polyvinylidene fluoride [PVDF]) in a solvent (e.g., Nmethyl2pyrrolidone [NMP]) to create a homogeneous slurry.
Homogenization:
Use mixers or ultrasonic homogenizers to ensure uniform distribution of components.
2. Electrode Coating and Drying
Coating:
Apply the slurry onto current collector foils (aluminum for the cathode, copper for the anode) using techniques like doctor blade coating or slot die coating.
Drying:
Remove the solvent by drying the coated foils in a vacuum oven at elevated temperatures (e.g., 80–120°C).
3. Cutting and Tab Welding
Cutting:
Cut the coated electrodes into strips with predefined dimensions using a die cutter.
Tab Welding:
Attach metallic tabs (usually nickel or aluminum) to the electrodes for electrical connection.
4. Winding
Wind the cathode, separator, and anode together into a jellyroll structure. This step requires precision to ensure even winding without misalignment.
5. Insertion into Metal Can
Insert the wound jellyroll into a cylindrical metal can. The bottom of the can acts as the negative terminal.
6. Top Cap Assembly
Place the top cap assembly, which includes the positive terminal, safety features, and insulating gaskets, onto the open end of the can.
7. Electrolyte Injection
Inject the electrolyte solution into the can through a small opening in the top cap. The electrolyte wets the electrodes and separator.
8. Sealing
Seal the top cap to the metal can using laser welding or crimping to create a hermetic seal, ensuring no leakage occurs.
9. Formation and Testing
Formation Cycle:
Subject the assembled cylindrical cell to a formation cycle to activate the battery and form a stable solid electrolyte interphase (SEI) layer on the anode.
Performance Testing:
Evaluate the cell's capacity, voltage profile, cycling stability, internal resistance, and other key parameters using electrochemical testing equipment.
10. Quality Control and Packaging
Inspect finished cells for defects such as swelling, leaks, or short circuits.
Package the cells for shipment.
Cylindrical Battery Fabrication Line
●Equipment Used in Cylindrical Cell Fabrication
1. Mixers: For preparing electrode slurries.
2. Coaters: For applying slurries onto current collector foils.
3. Drying Ovens: For removing solvents from coated electrodes.
4. Die Cutters: For cutting electrode strips.
5. Tab Welders: For attaching metallic tabs to electrodes.
6. Winding Machines: For assembling the jellyroll structure.
7. Insertion Machines: For inserting the jellyroll into the metal can.
8. Top Cap Assemblers: For placing the top cap assembly onto the can.
9. Electrolyte Injection Systems: For injecting electrolytes into the can.
10. Sealing Equipment: For sealing the top cap to the can using laser welding or crimping.
11. Electrochemical Workstations: For testing the performance of fabricated cells.
●Applications of Cylindrical Cells
1. Electric Vehicles (EVs):
Battery packs for hybrid and fully electric vehicles, including Tesla's popular use of 18650 and 21700 cells.
2. Consumer Electronics:
Laptops, flashlights, power banks, and other portable devices.
3. Energy Storage Systems (ESS):
Gridscale energy storage and backup power solutions.
4. Medical Devices:
Portable diagnostic tools and certain implantable devices.
5. Industrial Applications:
Robotics, drones, and other highpowerdensity applications.
●Advantages of Cylindrical Cells
1. Robust Design:
Metal casing provides excellent structural integrity and protection against external damage.
2. High Production Efficiency:
Standardized designs allow for mass production at lower costs.
3. Excellent Thermal Management:
The cylindrical shape facilitates efficient heat dissipation.
4. Proven Reliability:
Widely used and tested in various industries, ensuring longterm reliability.
5. Safety Features:
Integrated safety mechanisms like pressure relief vents reduce the risk of thermal runaway.
●Challenges in Cylindrical Cell Fabrication
1. Internal Resistance:
Higher internal resistance compared to pouch or prismatic cells due to the cylindrical geometry.
2. Weight:
The metal casing adds weight, making them less suitable for weightsensitive applications.
3. Space Utilization:
Less efficient use of space compared to pouch cells, limiting their application in compact devices.
4. Swelling Risk:
Gas generation during operation can cause swelling, reducing performance and lifespan.
5. Cost:
Metal casing and additional safety features increase material costs.
●Safety Considerations
1. Handling Lithium Metal:
Lithium is highly reactive and must be handled in a dry, oxygenfree environment.
2. Electrolyte Exposure:
Avoid skin and eye contact with electrolyte solutions, as they may be toxic or corrosive.
3. Proper Disposal:
Dispose of waste materials, such as used electrodes and electrolytes, according to environmental regulations.
●Future Trends in Cylindrical Cell Fabrication
1. Larger Formats:
Development of larger formats like the 4680 cell for improved energy density and reduced cost per kWh in EVs.
2. Advanced Materials:
Incorporation of novel materials like silicon anodes, sulfur cathodes, or solidstate electrolytes for enhanced performance.
3. Automation:
Increased automation in production lines to improve throughput and reduce costs.
4. Sustainability:
Focus on environmentally friendly materials and recycling processes to minimize ecological impact.
5. Integration with Other Technologies:
Combining cylindrical cells with supercapacitors or fuel cells for hybrid energy storage systems.
●Conclusion
Cylindrical cell fabrication involves precise preparation of electrode materials, careful assembly of components, and rigorous testing to ensure reliability and performance. By understanding the components, steps, and challenges involved, manufacturers can optimize their designs for specific applications. As advancements in materials and fabrication techniques continue, cylindrical cells will remain a critical component of modern energy storage technology.
What aspect of cylindrical cell fabrication excites you most? Share your thoughts below! Together, let’s explore how these innovative batteries are shaping the future of energy storage.
Louis@lithmachine.com
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