Experimental study on the formability of aluminum pouch for lithium polymer battery by manufacturing processes

Abstract

Lithium polymer batteries are an improvement from the existing lithium ion batteries in terms of the risks of electrolyte leakage and explosion. Demand for lithium polymer batteries is rapidly increasing because of their advantages such as stability, light, and higher degree of freedom of shape. Accordingly, the demand for aluminum pouches, which are the exterior material of lithium polymer batteries, is increasing and research and development of aluminum pouches are actively being conducted. In the case of aluminum pouches, the forming area and depth that can accommodate the battery cell are increased according to the capacity of the battery, and stable formability is essential for aluminum pouches. In this study, manufacturing processes were changed to examine ways to improve formability. First, by changing the process order so that the surface treatment coatings on both sides of the aluminum foil were carried out simultaneously, the number of times when there was contact of the nylon film with the work roll was reduced. As a result, formability was improved because damage to the surface of the nylon film was reduced and the slipperiness was maintained. In addition, with regard to the drying temperature of the adhesive that constitutes the innermost layer, as the drying temperature increased (120 °C), solvent volatility increased, leading to stronger adhesion between the interfaces and resulting in improved formability.