The storage systems that are currently used to store renewable energies could be made more efficient and sustainable in terms of service life and material recovery. To this end, a team at the HZDR Institute of Fluid Dynamics in Dresden (leaders in the field of liquid metal batteries) has got together with the Massachusetts Institute of Technology (MIT) to develop a new type of lithium-lead liquid metal battery.

By focusing on the electrolyte formulation and developing a special separator membrane, the team was able to increase the electrical current efficiency from 92 to almost 100 percent and to improve energy density by 45 percent.

When in operation, the batteries are exposed to temperatures of more than 400 degrees Celsius (so that the metals are liquified). The lithium element is contained in the upper part of the battery, the molten salt electrolyte in the middle, and heavier lead at the bottom. The novel membrane acts as an additional, second partition between the metals and improves the density of the molten salt, as well as preventing chemical damage to the battery.

“The high current densities, the completely liquid structure and the thus very simple recycling make these batteries an ideal stationary energy storage system for balancing highly fluctuating solar and wind energy," project director Norbert Weber told the Journal of Energy Chemistry, which first reported the innovation.

In the next phase of investigations, the HZDR scientists will research more environmentally-friendly raw materials than lithium in combination with lead. Sodium and zinc are thought to be promising alternatives and their potential is being looked at in the SOLSTICE project, which is coordinated by the HZDR and funded by the European Union.