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Lithium Battery Lab Machine
Pouch cell making line
August 2,2024.
A manufacturing line for lithium-ion pouch cells involves several detailed steps and equipment. Here is a more detailed production process:

1. Electrode Preparation

# 1.1 Mixing
Active materials, binders, conductive agents, and solvents are mixed to form a slurry. Common equipment includes high-speed mixers and vacuum mixers.
- **Active materials**: Cathode materials (e.g., nickel cobalt manganese oxide, lithium iron phosphate), anode materials (e.g., graphite, silicon-carbon).
- **Binders**: Such as polyvinylidene fluoride (PVDF).
- **Conductive agents**: Such as carbon black, conductive carbon nanotubes.
- **Solvents**: Such as NMP (N-methyl-2-pyrrolidone).

# 1.2 Coating
The slurry is uniformly coated onto current collectors (aluminum foil for cathodes, copper foil for anodes). Coating machines are usually double-sided or single-sided coaters.

# 1.3 Drying
The coated electrodes are dried in an oven to remove solvents.

# 1.4 Calendering
The dried electrodes are passed through a calender to achieve the desired thickness and density. Calendering aims to increase the energy density and conductivity of the electrodes.

# 1.5 Slitting
The calendered electrodes are slit into strips of the required width using a slitting machine.

2. Cell Assembly

# 2.1 Stacking or Winding
According to the design, electrodes and separators are stacked or wound into a cell structure.
- **Stacking**: Positive and negative electrodes and separators are stacked sequentially.
- **Winding**: Positive and negative electrodes and separators are wound into cylindrical or other shapes.

# 2.2 Tab Welding
The electrode tabs are welded to the electrode sheets, typically using ultrasonic welding machines.

# 2.3 Pouch Formation
The cell assembly is inserted into pre-made aluminum laminated film to form the pouch structure.

3. Electrolyte Filling and Sealing

# 3.1 Drying
The pouch cells are placed in a vacuum drying oven to remove moisture.

# 3.2 Electrolyte Filling
Electrolyte is injected into the cells in a dry room. The electrolyte mainly consists of organic solvents (e.g., ethylene carbonate, dimethyl carbonate) and lithium salts (e.g., lithium hexafluorophosphate).

# 3.3 Pre-Sealing
The pouch cells are partially sealed, leaving a small opening for electrolyte wetting.

# 3.4 Vacuum Sealing
The pouch cells are vacuum-sealed to ensure there is no air inside.

4. Formation and Aging

# 4.1 Formation
The cells undergo initial charge and discharge cycles to form the solid electrolyte interphase (SEI) layer. This process typically takes place in formation cabinets.

# 4.2 Aging
The cells are stored under controlled temperature and humidity conditions for a period to stabilize the SEI layer.

5. Final Sealing and Inspection

# 5.1 Final Sealing
The cells undergo final sealing to ensure complete sealing.

# 5.2 Inspection and Testing
The cells are subjected to a series of electrical performance tests, including capacity, internal resistance, leakage, and insulation. Testing equipment includes internal resistance testers, voltage testers, capacity testers, etc.

# 5.3 Quality Control
Cells undergo visual inspection and leak testing to ensure there are no defects and leaks.

Detailed Equipment Overview

- **High-Speed Mixer**: Used for mixing slurry to ensure uniformity.
- **Coating Machine**: Precision coating to control coating thickness and uniformity.
- **Drying Oven**: Removes solvents to ensure electrode drying.
- **Calendering Machine**: Adjusts electrode thickness and density, improving electrical performance.
- **Slitting Machine**: Cuts electrodes to the required width.
- **Stacking or Winding Machine**: Automated cell assembly.
- **Ultrasonic Welding Machine**: Welds tabs to electrodes to ensure solid connections.
- **Vacuum Drying Oven**: Removes moisture, preventing electrolyte decomposition.
- **Electrolyte Filling Machine**: Precisely injects electrolyte, controlling the filling volume.
- **Vacuum Sealing Machine**: Seals cells in a vacuum environment to prevent air entry.
- **Formation Cabinets**: Performs initial charge-discharge cycles to form the SEI layer.
- **Aging Room**: Stores cells under controlled conditions to stabilize the SEI layer.
- **Testing Equipment**: Comprehensive testing of cell performance to ensure quality.

The entire pouch cell manufacturing process needs to be carried out in a cleanroom environment with strict control of humidity and temperature to ensure the quality and performance of the cells. Additionally, extensive use of automated equipment can improve production efficiency and consistency.