| Abstract Scope |
Metallized polymer current collectors (MPCCs) 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. Additionally, due to the lightweight polymer layer, batteries which utilize MPCCs can have higher gravimetric energy densities. One drawback of MPCCs is that they are difficult to join to each other, and to a tab, by conventional methods. Through-hole ultrasonic assisted soldering (UAS) has shown to be a promising process for joining MPCCs to each other and to a tab, without the use of flux. In previous work we have shown that through-hole UAS can join 64 aluminum MPCCs to a tab with good consistency, strong mechanical bonding, and low electrical resistances. To explore the fundamental nature of through-hole UAS we have used high-speed video to record UAS of MPCCs by performing the soldering on a heated transparent glass slide and recording from below. High speed video revealed that intense cavitation occurs in the through-hole during UAS which facilitates oxide clearing and solder wetting. |