1.Process Flow
The main components of a lithium battery include a positive electrode with an active material typically being lithium cobalt oxide, a separator made of PP or PE composite membrane, a negative electrode with carbon as the active material, organic electrolyte, and a battery case made of aluminum-plastic composite film. The manufacturing process involves slurry preparation, film coating, assembly, and formation. In recent years, electronic products have become increasingly thinner and lighter, with faster charging speeds and reduced space, resulting in higher demands for the energy density of lithium batteries. Lithium batteries need to be continuously updated and improved to meet these demands, further trending towards smaller, lighter, and thinner batteries. The related topics of lithium batteries have always been a hot research focus. Adopting suitable materials and cell manufacturing processes can improve battery performance. For specific materials and processes, please consult Canrd!
2.Mixing
Mixing Process:
Equipment Used:Mixers (35L, 100L, 200L, 300L)
Function:
1.Grind the input materials and solvents into a suspended state solution.
Materials Used:
1.Cathode Materials: Lithium Cobalt Oxide, Ternary Materials, PVDF, NMP, Conductive Agent
2.Anode Materials: Graphite, CMC, SBR, Conductive Carbon Black
Control Points:
Solid content of the mixed slurry,slurry viscosity
Tools Used:
Viscosity Tester
3.Coating
coating Process:
Equipment Used: Coating Machine, comprises three parts; the machine head control area, the machine tail material collection area, and the middle drying oven area.
Function:
Apply the well-mixed and ground slurry onto the substrate (with aluminum foil thickness of 12µm and copper foil thickness of 8µm) and simultaneously dry the slurry coated on the substrate.
Control Points:
Density of the single or double side of the electrode, thickness of the electrode, consistency of the electrode thickness, temperature in the drying oven area.
Tools Used:
Sampler, thermometer, spiral micrometer, electronic scale, calculator, film caliper.
Safety Precautions:
When operators operating the machine, strictly prohibited to put their hands or fingers under any rollers of the coating machine to avoid any safety accidents,and forbidden to use hard objects or tools to hit or damage the rollers.
4.Rolling
Rolling Process:
Equipment Used: Roller Press Machine,comprises three parts:
material feeding station, roller pressing section, and material collection station.
Function:
To roller press the coated electrode sheets that meet the process requirements, ensuring that the thickness of the electrode sheets falls within the specified range of the process.
Control Points:
Thickness of the electrode after roller pressing, appearance of the electrode after roller pressing (no material shedding, cracks, or stripes are allowed).
Tools Used:
Spiral micrometer
Safety Precautions:
Strictly prohibited to put hands or fingers into the inlet of the roller press machine, and forbidden to use a blade to scrape the rollers.
5.Slitting
Automatic Slitting Process:
Equipment Used: Automatic Slitting Machine
Function:
To slice the large rolls of electrode that meet the process requirements after roller pressing into small rolls of electrode, and to complete the collection of these small rolls.
Control Points:
Width of the small roll of electrode, size of the burrs on the edge plane of the small roll of electrode, size of the burrs on the edge end face of the small roll of electrode, and neat winding.
Tools Used:
Stainless steel straightedge (precision of 0.5mm), projector
Safety Precautions:
Strictly prohibited to touch the blade holder and the blade of the slitting knife
6.Tabbing
Battery Tab Manufacturing with Automatic Tabbing Machine:
Equipment Used: Automatic Tabbing Machine
Function: To weld tabs and apply green adhesive tape to the small rolls of electrode that have been successfully slit from large rolls. At the end of the process, an automatic cutting blade is used to slice the small rolls into individual tabs.
Control Points:
Welding tension between the positive/negative tabs and the foil material, welding imprint appearance, spacing between the CPP glue on the tabs and the edge of the electrode sheet, the size of the electrode sheet exposed outside the green adhesive tape, and the size of the CPP tape applied.
Tools Used:
Welding tension tester, stainless steel straightedge
Safety Precautions:
Strictly prohibited to put fingers into the tab feeding area
7.Winding
Semi-automatic Winding Process:
Equipment Used: Semi-automatic Winding Machine
Function: To wind the welded tab and glued strip-applied electrodes that have been cut to specification with a separator film to form a bare cell
Control Points:
Width of the wound bare cell, thickness of the bare cell, overhang size,
Center distance between tabs, margin, overhang size in the length direction of the electrode (Note: The extreme difference between the overhang width of the negative electrode and the positive electrode)
Tools:
Vernier caliper, special fixture for checking the center distance between tabs
Safety Precautions:
Strictly forbidden to put fingers under the cutting knife of the separator
8.Hi-pot
Hi-pot Testing for Thermally Compressed Cores:
Equipment Used: Thermally Compressed Core Machine and Internal Resistance Tester
Function:
To conduct a double tab short-circuit test on the wound bare cells and select those that meet the process requirements.
Control Points:
Setting and calibration of internal resistance values
Tools:
Internal resistance calibration fixture
Safety Precautions:
Strictly forbidden to place hands or fingers between the upper and lower pressing plates.
9.X-ray
X-RAY Testing Machine:
Equipment Used: X-ray Testing Machine
Equipment Principle:
The X-ray tube emits X-rays that are projected onto the battery cell. These X-rays pass through an imaging device, which captures the image and displays it on a monitor for analysis using computer software. The image displayed shows the misalignment difference in the length of the positive and negative electrodes.
Function:
The wound bare cells undergo X-ray inspection to separate the overhang-qualified products from the unqualified ones.
Control Points:
The size of the cell's overhang
Safety Precautions:
Perform the testing with the machine's door closed to prevent exposure to X-ray radiation.
10.Aluminum-Plastic Film Punching and Shell Forming
Punching and Shell Forming Machine:
Equipment Used: Automatic Aluminum Foil Bag Forming Machine
Function:
To punch and form the aluminum-plastic film used for the outer packaging of the battery cell.
Control Points:
Appearance of the punched pocket bag, depth of the punched pocket bag, size of the four R angles of the punching mold, length dimension of the punched pocket bag, top edge dimension of the punched pocket bag.
Tools Used:
Height gauge, R angle gauge
Safety Precautions:
Strictly forbidden to put hands or fingers between the upper and lower punching molds
11.Top and Side Sealing
Top and Side Sealing Machine Process:
Equipment Used: Top and Side Sealing Integrated Machine
Function:
To thermally seal the top and sides of the pocket bag formed through punching and imaging, enclosing the bare cell within.
Control Points:
Thickness of the top and side seals, appearance of the seals, size of the external sealing area, size of the unsealed area inside the side seal, and the extent of the exposed CPP of the tab.
Tools Used:
Projector, spiral micrometer
Safety Requirements:
Prohibited to place hands or fingers under the heat sealing head to prevent crushing injuries. Before starting production in each shift, it is necessary to confirm that the light curtain is providing safety protection
12.Three-in-One
Three-in-One Test Process:
Equipment Used: Combined Three-in-One Testing and Yangzi Tester Unit
Function:
Conduct internal resistance testing on single and double tabs of packaged battery cells. (Note: Double tab testing is conducted on aluminum and nickel tabs, while single tab testing is performed on nickel tabs and aluminum-plastic film.)
Control Points:
Calibration of the internal resistance value set on the Yangzi tester.
Tools Used:
Internal resistance block
Safety Precautions:
Strictly prohibit placing fingers under the probes and lancets.
13.Baking
Pre-Injection Baking Process:
Equipment Used: Three-door Oven
Function:
To bake the packaged and flared battery cells to reduce the moisture content of the electrodes to within the specified process requirements.
Control Points:
Time of battery cell entry into the oven, baking time, baking temperature, vacuum level, cooling time of the battery cell, and water content of the electrodes.
Tools Used:
Temperature tester, electrode water content tester
Safety Precautions:
When removing the baked battery cells from the oven, gloves must be worn to prevent burns.
14.Electrolyte Injection
Electrolyte Injection Process:
Equipment Used: Manual Liquid Injection Machine and Fully Automatic Liquid Injection Machine
Function: Injecting a specified weight of electrolyte into the baked bare battery cell electrodes that have a water content within the process specifications.
Control Points:
Accuracy of the liquid injection pump.
Tools Used:
Electronic scale, hexagon wrench.
15.Vacuum Sealing
Vacuum Sealing Process:：
Equipment Used: Simple Vacuum Sealing Machine
Function:
Evacuate the internal gas from the battery cells after liquid injection and complete the heat sealing of the gas bag opening.
Control Points:
Seal thickness, vacuum level, and effectiveness of vacuum evacuation
Tools Used:
Screw micrometer, Teflon tape
Safety Precautions:
Strictly prohibit placing fingers under the heat sealing head. Do not place the gas bag opening of the unsealed battery cell facing downwards.
16.Hot and Cold Pressing
Hot and Cold Pressing Process:
Equipment Used: Hot and Cold Pressing Integrated Machine
Function:
To perform hot pressing followed by cold pressing on the settled battery cells to shape and adjust their appearance.
Control Points:
Hot pressing time, cold pressing time, air pressure for both hot and cold pressing, parallelism of the upper and lower press plates, cold pressing temperature.
Tools Used:
Temperature tester, carbon paper
Safety Precautions:
Check if the protective cover is installed and if the safety light curtain is effective. Strictly prohibit placing hands or fingers between the upper and lower press plates.
17.Formation
Formation Process:
Equipment Used: Hangzhou Reliability Instruments (Hangke Machine)
Function:
To perform a preset process of charging and discharging on the battery cells after liquid injection, in order to activate the lithium ions inside the cells and make them electrically charged.
Control Points:
Setting of the formation steps, precision calibration of the voltage points in the formation cabinet
Tools Used:
Multimeter
18.Secondary Sealing
Secondary Sealing Process:
Equipment Used: Degassing Machine
Function:
Extract internal gases and excess electrolyte from the battery cells and perform the final sealing of the edges
Control Points:
Effectiveness of extracting internal gases from the cells, seal thickness, thickness of the sealed and formed battery cells
Tools Used:
Screw micrometer
Safety Precautions:
The battery cells awaiting secondary sealing must be placed in the designated cell adjustment slots
19.Grading
Grading Process:
Equipment Used: Hangzhou Reliability Instruments (Hangke Machine)
Function:
Perform capacity sorting on the battery cells that have completed secondary sealing, selecting those that meet the process requirements.
Control Points:
Whether the settings of the capacity sorting steps meet the process requirements, whether the current and voltage accuracy of the sorting cabinet comply with the process specifications, and whether the cell capacity falls within the specified range.
Tools Used:
Multimeter
20.0CV Testing
Testing Process:
Equipment Used: OCV Testing Machine
Function:
To calculate the voltage drop of the battery cells based on the voltage at specific time points (Formula: K value = Voltage Difference / Time Difference), and select the cells that meet the process requirements.
Control Points:
The time period for testing the cell voltage must be within the specified process specifications.
The placement location of the cells must be in a constant temperature environment.
21.Canrd Brief Introduce
Canrd use high battery R&D technology(core members are from CATL) and strong Chinese supply chain to help many foreign companies with fast R&D. We provide lab materials, electrodes, custom dry cells, material evaluation, perfomance and test, coin/pouch/cylindrical cell equipment line, and other R&D services.
Email： contact@canrd.com Phone/Wechat/WhatsApp： +86 19867737979
Canrd Official Web Canrd Company Vedio Canrd Company profile
Website : www.canrud.com
22.
Q & A
During this Q&A session, Dr. Ke addressed each of the participants' questions one by one.
Heihei: "How is the thickness of the R-angle measured? How can the deformation of the R-angle be observed?"
Dr. Ke:
"The R-angle thickness can be measured using a specialized micrometer, and deformation can be observed by preparing samples with crystal resin and analyzing them under a metallographic microscope."
Angel Offline: "Why is baking still required after roll pressing the electrode sheets?"
Dr. Ke:
"Some manufacturers prefer pre-baking to ensure the coating is fully dried, as incomplete drying during the cold pressing process could lead to sticking on the rollers."
Heihei: "For testing the seal between the aluminum tab and the aluminum-plastic film, is voltage measurement sufficient? Or should resistance be measured?"
Dr. Ke:
"In the three-in-one testing process, internal resistance is tested for both tabs and the aluminum-plastic film."
Angel Offline: "Cell deformation after formation and aging is said to be caused by winding tension. What steps can be taken to control it?"
Dr. Ke:
"The most effective method is to treat the separator with PVDF to bond the positive and negative electrodes into a single structure. You can also control tension formation by reducing winding tension and lowering the compaction density. External force control measures, like using PVDF-treated separators or implementing jig formation processes, can also help improve the situation."
Angel Offline: "Do you mean using separators coated with PVDF?"
Dr. Ke:
"Yes, that's correct."
Heihei: "What is the mechanism behind hot pressing? What does it primarily heat? How does residual electrolyte in the secondary sealing area affect sealing strength, and how can this be resolved?"
Dr. Ke:
"You’re referring to the hot and cold pressing processes, which were used in earlier methods. With the introduction of jig formation machines, these processes are no longer separately required. Residual electrolyte in the secondary sealing area indeed affects sealing strength, so it's essential to control the electrolyte injection volume."
Angel Offline: "The cells I've been working on lately often exceed the thickness specification. What areas should I address to improve this?"
Dr. Ke:
"Focus on compaction, select materials with minimal rebound, and avoid side compression during production. For example, when applying side adhesive, ensure that excessive force is not applied, which could increase cell thickness."
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