Since the early 1990s Lithium ion batteries have entered industrial markets as energy storage technology for mobile consumer electronics and battery-operated tools. More recently, Li ion batteries have broken into new markets like battery energy storage systems (BESS) where they are used for load leveling, peak shaving and power demand management in grid-connected and autonomous power networks. Most promising seems to be their use in the market of electric vehicles ranging from electrical bicycles to high-performance passenger cars.
For applications in e-mobility, individual batteries are assembled in a module. Several of these modules are then combined in a so-called battery pack, which among others also comprises systems for cooling and battery management. All these components are integrated in a housing which protects the components inside. In the entire assembly, water ingress may lead to short circuits. In individual batteries, water ingress may lead to capacity loss and generation of hazardous substances due to chemical reactions with battery materials. So leak tightness is a major criterion for stable performance of a battery pack over the expected lifetime of an electrical vehicle.