Realization of Reliable Connection of Mg Anode and Al Tab by Ultrasonic Welding for Reachable Magnesium Batteries

Rechargeable magnesium batteries (RMBs) have garnered significant attention in recent years. However, the commercialization of RMBs has been severely hampered by the low-strength and high-resistance connections between the magnesium (Mg) anodes and aluminum (Al) tabs. To address this challenge, we perform orthogonal experiments on 0.2 mm-thick Al–Mg ultrasonic welded joints to establish an optimized parameter range. Analysis of variance revealed that ultrasonic amplitude exerted the most dominant influence on joint strength (52.03%), followed by welding time (25.59%) and welding pressure (22.37%), with a significant interaction effect observed between welding time and amplitude. Notably, at a welding pressure of 0.40 MPa, the Al–Mg joint achieved peak performance, including the maximum lap-shear load (59.20 N) and minimal electrical resistance (0.483 mΩ). RMB pouch cells assembled with good-welded tabs demonstrated superior electrochemical performance compared to under and overwelded counterparts, exhibiting reduced internal resistance (3.55 Ω in the first cycle), enhanced capacity retention (77.45% after 60 cycles), and raised Coulombic efficiency (99.88% after 440 cycles).