Robust Solid State Battery

Scientists at Forschungszentrum Jülich have developed a sodium solid state battery that has over 90 percent of its initial capacity after 100 charging cycles. This is a very good value for solid state batteries that are currently still in the experimental stage. Comparable results could previously only be achieved with designs containing liquids or additional soft layers, such as a polymer.

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Solid state batteries have several advantages over current lithium-ion batteries with liquid electrolyte. They cannot leak or catch fire and are therefore naturally safe and robust. Also, less technology is needed to protect the cells from shocks and maintain stable temperatures, which also helps to reduce weight and costs.

Since solid state batteries can also achieve very high energy densities, intensive research is being conducted worldwide. But despite all efforts, pure solid-state batteries that do not contain any liquid or soft, polymer-like layers are still a long way from market maturity. In particular, the connection of electrode and electrolyte is considered problematic.

"In a battery, the transported ions are constantly stored in the electrode or pass from the electrode to the electrolyte - this is how a battery works," explains Dr. Frank Tietz of the Jülich Institute of Energy and Climate Research (IEK-1). "This constant growth and shrinkage of the electrodes tolerates solids much less than a liquid electrolyte, which always ensures good contact. The chemist from Jülich has been working on developing new materials for solid state batteries and fuel cells for years.

For the implementation, the researchers chose a battery based on sodium. Although the possible energy densities are clearly below those of lithium solid-state batteries, they are not as high as those of sodium batteries. However, sodium has several other advantages: it is easily available and less expensive than lithium, making it particularly interesting for stationary applications, such as intermediate storage for renewable energies. In addition, unlike lithium, sodium is less prone to the formation of metallic dendrites, which can lead to a short circuit that destroys the battery. Cobalt-free cathode materials are also possible.