# Tab-to-Busbar Interconnections in EV Battery Packs: An Introductory Review of Typical Welding Methods

## TL;DR

This paper reviews different welding methods used to connect battery tabs to busbars in electric vehicle battery packs, comparing their advantages and limitations.

## Contribution

The paper introduces a comparative overview of resistance, laser beam, and ultrasonic welding methods for tab-to-busbar interconnections in EV batteries.

## Key findings

- Ultrasonic welding suppresses porosity and limits Al-Cu intermetallic growth but is sensitive to thickness and tool wear.
- Laser beam welding allows high-speed production but requires careful control to avoid spatter and brittle intermetallic compounds.
- Resistance welding is cost-effective but suffers from electrode wear and variability in highly conductive stacks.

## Abstract

This paper reviews tab-to-busbar interconnections in lithium-ion battery packs, focusing on resistance welding (RW), laser beam welding (LBW), and ultrasonic welding (USW). The functional roles of tabs and busbars and typical material choices (Al-, Cu-, and Ni-plated Cu) are outlined. Subsequently, the processes are compared in terms of heat input, interfacial metallurgy, electrical resistance, mechanical robustness, and manufacturability. USW, as a solid-state method, suppresses porosity and limits Al-Cu intermetallic growth, but is sensitive to thickness, stack geometry, and tool wear. LBW enables high-speed, automated production with precise energy delivery, yet requires careful control to mitigate spatter, porosity, and brittle IMCs in dissimilar joints. RW remains cost-effective and flexible but can suffer from electrode wear and variability with highly conductive stacks. This review also summarizes the effect of the busbar material (Al versus Cu) and thickness on the connection resistance and temperature increase under a high current. No single process is universally superior, and the selection should match the stack-up, reliability targets, and production constraints. This paper aims to provide an overview of recent and conventional research trends for each welding method and to introduce selected non-traditional approaches, thereby presenting a range of viable options for future applications.