Ultrasonic welding technology for lithium battery packs has been widely applied in the field of battery manufacturing due to its advantages such as high efficiency, reliability and low thermal impact. The following analyzes the application value of typical scenarios such as power battery modules, energy storage battery systems, pouch battery TAB connections, and battery PACK integration, in combination with their technical characteristics:

Welding of tabs for power battery modules

In the power battery module of new energy vehicles, multi-layer tabs (copper foil or aluminum foil) need to be connected to the Busbar. Traditional welding methods are prone to causing false soldering, oxidation or thermal damage, while ultrasonic welding achieves molecular-level bonding through high-frequency vibration, without the need to melt metals, avoiding heat-affected zones and ensuring stable electrical conductivity. For instance, in the production of cylindrical battery modules, a certain automotive manufacturer adopted ultrasonic welding technology to connect 200 layers of 0.03mm thick aluminum tabs with busbars. The welding strength met the requirements of vibration tests, the resistance value was less than 0.1mΩ, and the cycle life was increased by 15%.

2. Series and parallel connection of battery cells in energy storage battery systems

Large-scale energy storage systems (such as peak shaving in power grids and backup power sources for base stations) require a large number of battery cells to be connected in series and parallel. Ultrasonic welding can achieve rapid connection between the battery cell terminals and nickel sheets/aluminum sheets. The single-point welding time is only 0.1 to 0.3 seconds, and the efficiency is more than three times that of laser welding. A certain energy storage project adopted this technology to connect 1,000 battery cells, achieving a welding yield of 99.8%, increasing the consistency of the system's internal resistance by 20%, and significantly reducing the risk of thermal runaway.

3. Weld the tabs of the pouch battery to the FPC

The tabs of pouch lithium batteries need to be connected to the flexible circuit board (FPC), and traditional soldering is prone to damage the FPC substrate. Ultrasonic welding, by optimizing amplitude and pressure parameters, can achieve reliable connection between aluminum tabs and FPC copper foil at a pressure of 0.2MPa, with a welding strength of 15N/mm, and there is no delamination or burning phenomenon on the FPC. After a certain consumer electronics manufacturer applied this technology, the product return rate dropped from 3% to 0.5%.

4. Welding of copper-aluminum adapter pieces in battery PACK integration

In the battery PACK (PACK), the transition between copper bars and aluminum bars needs to avoid electrochemical corrosion. Ultrasonic welding forms a metallurgical bonding layer at the copper-aluminum interface through a solid-state connection mechanism, with a contact resistance of less than 0.5mΩ, which is 60% lower than mechanical crimping. A certain energy storage container project adopted this technology to connect copper-aluminum adapter plates. After two years of operation, the interface resistance increased by less than 10%, while the traditional riveting scheme increased by more than 50%.

5. Welding of the sampling line for the battery management system (BMS)

The BMS needs to collect the voltage of individual cells, and the connection between the sampling line and the terminal post requires high precision and low impedance. Ultrasonic welding can achieve tiny weld points between nickel wires with a diameter of 0.1mm and aluminum poles, with a weld point diameter of only 0.5mm and a resistance fluctuation range of ±0.05mΩ, meeting the requirements of high-precision sampling. After the application of a certain unmanned aerial vehicle battery project, the voltage acquisition error decreased from ±20mV to ±5mV.

Summary of Technical Advantages

Low heat effect: The welding temperature is much lower than the melting point of the metal, avoiding oxidation of the tabs or thermal shrinkage of the separator.

High efficiency: Single-point welding time is less than 0.5 seconds, suitable for large-scale production.

High reliability: Welding strength > 10N/mm, contact resistance < 0.1mΩ, cycle life increased by 10%-20%.

Compatibility: Suitable for the connection of metals such as copper, aluminum, nickel and dissimilar metals, with a thickness range of 0.01-2mm.

Ultrasonic welding technology has become a key process in the manufacturing of lithium battery packs, especially excelling in enhancing energy density, safety and production efficiency. With the development of batteries towards high integration and high power, the application scenarios of this technology will be further expanded.