What does hermeticity mean, how is it defined and tested, and what is the difference between hermetic and quasi-hermetic packaging?
There is not yet a single energy storage system that can fulfill all the dreams of practical and at the same time cost-effective electromobility. In the race for technology, promising new candidates are on the way, such as solid-state batteries (see p.30) and supercapacitors, which are increasingly competing with battery technology. However, experts assure us that the rechargeable lithium-ion battery (LIB) is and will remain the top performer, at least for the next five to ten years. For example, the LIB market for electric cars, (plug-in) hybrids and electric buses, is expected to grow from $15 billion in 2016 to $38 billion 2025, according to a study by the Parisian market researchers at Avicenne Energy in 2017. The collective term LIB refers to many cell variants, depending on the materials used in cell chemistry.
This already gives us an idea of the dilemma in which most developers of storage technologies find themselves. Every material has its strengths and weaknesses. Lithium systems are preferred for e-vehicles because the metal is very light, yet can store large amounts of energy and thus enable relatively long ranges. LIB can withstand many charging cycles, operate with low energy losses and have a very long service life.
Compared to combustion technologies, however, LIB must catch up in key areas such as range and cost in order to make the production of and transition to e-cars more attractive. In addition, the LIB system is not perfect either; the battery is exposed to many stresses during operation that can adversely affect its performance, capacity and service life. These include extreme temperatures, humidity, vibrations, salt spray and harmful gases. In addition, LIB cells usually contain liquid, combustible electrolyte that is not allowed to overheat or leak.
For these reasons, battery manufacturers must ensure the tightness of the system at all times and develop appropriate housing and cooling technology. This is where a new type of battery cell cover comes into play. The electrical contacts are hermetically sealed into the aluminum covers. With this unique glass-aluminum sealing technology and more than 75 years of experience with glass-to-metal melting, the SCHOTT technology group is the first company in the world to have succeeded in creating a permanently tight connection be- tween the materials glass and aluminum. The advantage: chemically and thermally resistant special glass replaces the plastic sealing material that is commonly used for cells and ages quickly under harsh operating conditions. If the organic material leaks as a result, moisture can penetrate or liquid electrolyte can escape. Possible consequences include short circuits, fi re hazards, damage or reduced battery performance.