In lithium battery manufacturing, tab welding is the key step connecting cells to external circuits. Ultrasonic metal welding has become the mainstream tab welding process thanks to its minimal heat effect and no need for filler materials.
How it works
Ultrasonic metal welding is a solid-state process: the horn transmits high-frequency mechanical vibration into stacked metal foils, and under static pressure, high-frequency friction at the interface clears oxides away so metal atoms diffuse and bond. The metal never melts — interface temperature typically reaches only one-third to one-half of the melting point — so heat effect is minimal and tabs and separators stay undamaged.
Why it suits tab welding
Tabs are usually stacks of thin, soft copper or aluminum foils. Ultrasonic welding can join dozens of foil layers in one shot, producing low-resistance, highly conductive joints; there is no spark spatter to contaminate the cell interior, and weld times are short enough for high-speed cell lines.
Quality control points
Matching amplitude and pressure: too much amplitude burns through foils, too little gives weak bonds — validate the process for your foil count and thickness.
Horn knurl condition: the knurl pattern grips the foils and transmits vibration; worn knurls slip and cause weak welds, so inspect and replace horns regularly.
Dissimilar metal welding: copper-aluminum combinations differ greatly in hardness and thermal conductivity, demanding more stable power output and control accuracy — choose machines with energy monitoring to judge weld quality in real time.
As EV and energy storage markets grow, tab welding demands ever better consistency and traceability, making machines with weld data recording the mainstream choice.