Welding is an important process in lithium-ion battery pack assembly, where battery tabs, cell interconnects, and busbars must meet electrical, mechanical, and manufacturing requirements. The selected method affects joint strength, electrical resistance, production cycle time, and equipment configuration.
This guide introduces six welding processes and explains their applications in manufacturing, with a focus on resistance spot welding and laser welding for lithium battery pack assembly. It also compares resistance spot welding, laser welding, and ultrasonic metal welding, and examines equipment selection using the ACEY-S200B automatic spot welding machine and ACEY-HLW handheld galvo laser welding machine as examples.
1.FAQ
Q: What welding methods are commonly used for lithium battery tabs?
A: Resistance spot welding and laser welding are common options for lithium battery tab connections. Ultrasonic metal welding may also be suitable for certain multilayer tabs and thin metal foils. The choice depends on material type, thickness, and joint geometry.
Q: What is the difference between resistance spot welding and laser welding?
A: Resistance spot welding generates heat through electrical resistance while electrodes apply pressure to the workpieces. Laser welding uses a focused beam to heat the joint area without contact electrodes. These differences affect material compatibility, joint design, and equipment configuration.
Q: How do you choose the right battery welding equipment?
A: Choose battery welding equipment based on material compatibility, workpiece thickness, joint geometry, required weld quality, positioning accuracy, and production volume. Validate the selected setup through sample welding and joint testing before production.
2.Six Common Welding Processes and Their Applications
Welding processes differ in their heat sources, bonding mechanisms, and equipment configurations. Selection depends on the base metals, component design, quality requirements, and production needs.
2.1 Arc Welding
Arc welding uses an electric arc to generate heat and fuse metals. Common variants include gas metal arc welding (MIG/MAG) and gas tungsten arc welding (TIG).
These methods are widely used in metal fabrication, structural manufacturing, and mechanical assembly. In battery production, they are generally more relevant to supporting frames and enclosures than to small cell interconnections.
2.2 Resistance Welding
Resistance welding generates heat through electrical resistance as current flows across contacting workpieces. Its main variants include spot welding, seam welding, and projection welding.
Resistance spot welding is commonly used to connect cylindrical battery cells with compatible nickel strips or other conductive tabs. Key variables include welding current, pulse duration, electrode force, and electrode condition. Proper adjustment helps produce consistent welds for the specified materials and thicknesses.
2.3 Laser Welding
Laser welding directs a focused beam onto a localized area, typically forming a metallurgical bond through melting and solidification.
In battery manufacturing, it can join cell terminals, conductive tabs, busbars, and other electrical components when the materials and joint design are compatible. Important parameters include laser power, travel speed, focal position, beam characteristics, and the gap between mating surfaces.
2.4 Plasma Arc Welding
Plasma arc welding uses a constricted arc to concentrate thermal energy in a localized area. It is used in specialized metalworking where precise arc control and concentrated heat input are required.
Its suitability depends on the metal type, component dimensions, and joint configuration. Compared with resistance spot welding for cylindrical cell-to-tab connections, plasma arc welding has a more specialized role in battery assembly.
2.5 Ultrasonic Metal Welding
Ultrasonic metal welding combines high-frequency mechanical vibrations with pressure to form a solid-state bond, typically without bulk melting of the base metals.
It can be used for certain multilayer battery tabs, thin metal foils, and compatible dissimilar-metal combinations. Selection depends on the metal pairing, stack thickness, surface condition, and required bonding quality.
2.6 Friction Welding
Friction welding generates heat through relative motion between contacting surfaces. Applied pressure then forms a bond, with the mechanism depending on the specific friction-welding process.
Typical applications include shafts, rods, and other metal components. Conventional friction welding is uncommon for battery cell-to-tab connections, although selected friction-based techniques may suit specialized components with compatible geometries.
3. Welding Methods for Lithium Battery Pack Assembly
Resistance spot welding and laser welding are two common options for battery pack assembly. Their suitability depends on the materials, joint design, and production requirements.
3.1 Resistance Spot Welding for Cylindrical Battery Packs
Working Principle
Resistance spot welding applies electrode pressure while electric current passes through the contact area, generating heat that forms a weld nugget. Weld quality depends on current, weld time, electrode pressure, and surface condition.
Applications
This method is commonly used to join compatible cylindrical cells with nickel strips, nickel-plated steel strips, and other suitable metal connectors. Weld locations and quantities depend on cell terminal design, connector geometry, and electrical requirements.
For multi-series and multi-parallel battery packs, accurate positioning and programmable weld patterns accommodate different cell layouts.
Key Selection Criteria
- Material Compatibility: Check material type, thickness, and surface condition to ensure compatibility with the electrodes.
- Welding Parameters: Optimize current, weld time, and electrode pressure to minimize weak joints, excessive heating, and potential cell damage.
- Positioning and Weld Layout: Set electrode positions and welding sequences according to the pack design.
- Automation and Monitoring: Consider automatic positioning, programmable controls, real-time current monitoring, and fault alarms based on production needs.
Maximum current alone is not a reliable selection criterion. Trial welding should verify joint strength, electrical resistance, weld consistency, and cell condition.
Equipment Example: ACEY-S200B Single-Sided Automatic Spot Welding Machine
ACEY-S200B Spot Welding Machine supports multi-point welding of cylindrical battery packs using 14500, 18650, 21700, 26650, and 32700 cells. Applications include power tool batteries, electric scooter batteries, and energy storage packs.
Key features include:
- Programmable Controls: Supports matrix, array, and point-position programming, with storage for up to 100 welding programs.
- Repeat Positioning Accuracy: ±0.02 mm.
- Current Monitoring: Supports real-time welding current monitoring, with a rated maximum welding current of 10,000 A for the transistor welding power supply.
- Fault Alarms: Includes alarms for cold solder joints, weld point detachment, and welding needle wear.
These features support positioning control and process monitoring. Actual weld quality and production throughput depend on the cell layout, connector design, welding parameters, and machine configuration.
Before production, conduct trial welding with the intended cells and connectors to verify joint quality, electrical performance, and process stability.
3.2 Laser Welding for Battery Connection Plates and Busbars
Working Principle
Laser welding uses a focused beam to heat and melt material locally, forming a joint without contact electrodes. Its suitability depends on the material combination, joint geometry, and welding conditions.
Applications
In lithium battery manufacturing, laser welding can join compatible connection plates, busbars, and other conductive components, including selected busbar-to-terminal joints.
Copper, aluminum, and other metals can be laser-welded under appropriate conditions. Differences in laser absorption and melting behavior require careful parameter selection. For copper-aluminum joints, joint design, intermetallic compound formation, and mechanical and electrical performance also need evaluation.
Key Selection Criteria
- Material Properties: Check material type, thickness, and laser absorption characteristics, especially for copper, aluminum, and dissimilar-metal combinations.
- Joint Design: Evaluate joint gaps, overlap configuration, positioning accuracy, and welding paths.
- Laser Parameters: Determine suitable power, welding speed, focal position, and scanning pattern through testing.
- Heat Control: Assess thermal effects on nearby cells, insulation, and surrounding components.
- Equipment Configuration: Choose a handheld, fixed-position, or automated system according to workpiece geometry, accessibility, and production volume.
Trial welding should confirm that the joint meets product specifications for strength, electrical resistance, consistency, and thermal performance.
Equipment Example: ACEY-HLW Handheld Galvo Laser Welding Machine
ACEY-HLW Series is designed for selected battery-related metal joining applications where handheld operation provides access to the workpiece.
Key features include:
- Power Options: 1500 W, 2000 W, and 3000 W.
- Dual-Axis Galvo Scanner: Controls the laser scanning path through the handheld welding head.
- Programmable Scanning Patterns: Supports circular, square, and other customizable shapes.
- Cooling System: Water-cooled design.
- Connection Cable: 8 m, with the practical working range depending on the installation layout.
According to the equipment specifications, listed applications include aluminum-to-aluminum sheet welding, copper-to-copper sheet welding, and selected copper-aluminum composite material joints. Suitability for other battery pack components depends on the material combination, thickness, joint geometry, and laser configuration.
Laser power alone does not determine weld quality. Trial welding should verify joint strength, electrical resistance, weld consistency, and thermal effects on nearby cells and components.
4. Resistance Spot Welding vs. Laser Welding
These tow welding methods differ in their energy sources, bonding mechanisms, and application requirements. The appropriate choice depends on material properties, joint design, and production needs.
Comparison of Tow Welding Methods
|
Comparison Factor |
Resistance Spot Welding |
Laser Welding |
|
Energy Source |
Electrical resistance heat |
Focused laser beam |
|
Joining Mechanism |
Localized heating, typically involving melting and solidification |
Localized melting and solidification |
|
Battery Applications |
Compatible cylindrical cell terminals and metal interconnects |
Suitable connection plates, busbars, and other conductive components |
|
Key Parameters |
Welding current, weld time, electrode force |
Laser power, welding speed, focal position, scanning path |
|
Process Considerations |
Electrode compatibility, contact quality, weld consistency |
Material absorption, joint gap, heat input, thermal effects |
|
Equipment Factors |
Electrode configuration, positioning, parameter control, automation |
Laser configuration, scanning system, positioning, cooling |
Products Description
Select a welding process based on material compatibility, joint design, connection requirements, and production conditions.
5.1 Evaluate Materials and Joint Design
Identify the material, thickness, and joint configuration of the cell terminals, battery tabs, or busbars. Confirm that the selected process is suitable for the materials and joint geometry.
5.2 Select the Appropriate Equipment
Resistance Spot Welding: Consider welding current, electrode design, positioning accuracy, and parameter control.
Laser Welding: Consider laser power, welding head configuration, scanning path, positioning system, and cooling requirements.
5.3 Test Welding Quality
Conduct sample welding using the actual materials and workpiece geometry. Evaluate joint strength, electrical resistance, and weld consistency, while checking for thermal or mechanical damage to cells, insulation, and surrounding components.
6. Conclusion
Resistance spot welding and laser welding serve different battery interconnection requirements. Resistance spot welding is commonly used for compatible cylindrical cell-to-tab connections, while laser welding is suitable for selected tabs, busbars, and other conductive components.
The final choice depends on material compatibility, joint design, required weld quality, and production conditions. Trial welding with actual workpieces helps verify process suitability and determine the appropriate equipment configuration.