| Abstract Scope |
Metallized polymer current collectors (MPCC’s) are a composite current collector made by depositing a thin layer (1-micron thick) of metal on both sides of a polymer substrate (6-micron thick). When integrated in a lithium-ion battery, MPCC’s can act as a passive safety mechanism by electrically isolating internal short circuits. One drawback of MPCC’s is their poor weldability, primarily due to their composite nature and thin metallization layers. Ultrasonic metal welding (UMW) can be used to weld MPCC’s to each other and a tab, however the process can be inconsistent, and it becomes more difficult with larger stacks of MPCC’s. In this work, the effect of the three major UMW parameters (energy, amplitude, pressure) on the electrical resistances and mechanical strengths of MPCC welds was evaluated. This analysis was performed on MPCC stack sizes ranging from 1 film to a tab, to 32 films to a tab. Generally, the MPCC welds had the best electrical and mechanical performance with low energy, medium amplitude, and maximum weld pressure. However, as the MPCC stack size increases, the energy and amplitude need to be increased to penetrate the stack of films and create a bond with the tab. With stack sizes equal or larger than 16 films to a tab, the process window shrunk, and the electrical and mechanical performance decreased. Additionally, A maximum stack size of 32 films to a tab was found. Beyond 32 films, the ultrasonic metal welder was not capable of piercing the MPCC films, even at maximum pressure with higher amplitudes and energies. |