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.

Leaking cells can thus significantly reduce the storage capacity and thus the range of an electric car in a short time and thus fall short of the desired standard for such traction batteries. After 10,000 charging cycles, these batteries should still have over 80 percent of their capacity. If the battery needs to be replaced prematurely, up to one third of the vehicle’s value is at stake. No manufacturer wants to expose itself to such risks, especially since confidence in electromobility is only just beginning to grow. This is why battery housings are designed for a high degree of safety and tightness and are often complex in design, sometimes at the expense of weight and space in the vehicle.

“In contrast, our SCHOTT GTAS® cover design creates more design freedom and enables battery developers to reduce the number of components,” says Claire Buckwar, Head of the Strategic Business Field Batteries at SCHOTT. Supercapacitors are similar in structure to LIB, but can store and release large amounts of energy in much less time, recharge electric cars in minutes, and support start-stop functions. Supercapacitors with polymer seals can also lose capacity, however. Because of this risk, they are sometimes “oversized.” With SCHOTT GTAS® covers, they can now gain room to minimize or in- crease capacity. And because batteries with this technology retain their capacity much longer, after eight to ten years in the car, they are ideally suited for a “second life” of another ten years, which is currently being intensively discussed, for applications such as feeding energy into the power grid.

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