Contact

Dr. Tom Weier

Head Liquid metal battery
t.weierAthzdr.de
Phone: +49 351 260 2226

Liquid Metal Batteries

Foto: Forschungsgruppe Flüssigmetallbatterien ©Copyright: Dr. Michael Nimtz

Research Group Liquid Metal Batteries

Source: Dr. Nimtz, Michael

With the growing role of solar and wind power in the German energy landscape, large scale storage becomes a key enabler for a functional power grid. In this setting, cost per unit stored energy and high number of charge and discharge cycles (low capacity fading) are the main criteria for a successful technology.

Liquid metal batteries, i.e. batteries in which both electrodes as well as the electrolyte are in the liquid state, are a very promising concept for economic storage. If abundant and cheap active materials can be used in large cells, the predicted total costs per unit stored energy are low and quite competitive.

A battery with fully liquid active interior has a number of advantages: when densities are chosen properly, the battery is self-assembling due to stable stratification. Liquid-liquid interfaces possess fast kinetics, thereby allowing for rapid charging and discharging, i.e., high rate capacity. Structureless (liquid) electrodes are insusceptible to aging providing nearly unlimited cyclability.

High current densities together with the large electrode areas of big cells imply a large total cell current and here electromagnetics together with fluid mechanics – i.e. magnetohydrodynamics – comes into play. In very large cells, the Lorentz force produced by the interaction of the cell current with it's own magnetic field may excite the Tayler instability (TI) that was demonstrated in our group by Seilmayer et al. (2012). Even in smaller cells, electromagnetic forces can drive so-called electro-vortex flows and excite interfacial waves. These waves typically arise at both interfaces of the three-layer system. Their interaction is determined by the ratio of the density jumps at the interfaces and, like the two cases mentioned above, can lead to a short circuit under extreme conditions. For safe operation of the batteries, such a situation must of course be ruled out. On the flip side, mild flows, particularly in the cathode and in the electrolyte, are beneficial to improve mass transport and thus to increase the efficiency of the cells. 

We study flow phenomena and instabilities experimentally and numerically in connection with electrochemical processes in order to optimize the operating characteristics of LMBs. 

At our battery laboratory we are able to perform electrochemical testing of electrodes, molten salt electrolytes and operation of small scale cells. For scale-up and efficiency improvement, testing of different container and isolator materials is essential to enable long term operation of cells. 

2017, the first international workshop on liquid metal battery fluid dynamics (LMBFD 2017) was organized by our group and took place on May 16th and 17th 2017 in Dresden. The focus was on fluid dynamics and other aspects of liquid metal batteries and related devices (e.g., aluminum reduction cells). A second workshop on the fluid dynamics of liquid metal batteries was organized in November 2022 together with the Isaac Newton Institute (INI) in Cambridge frame of SOLSTICE. The talks are vailable on Youtube.

Research Topics and Exeriments

Foto: Battery Laboratory with Glovebox ©Copyright: Dr. Michael Nimtz

Battery Laboratory

Our battery lab enables the electrochemical investigation of liquid metal electrodes and molten salt electrolytes.
For experiments, small cells are build and tested under argon atmosphere in the glove box.
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Foto: TI aspect ratio ©Copyright: Dr. Norbert Weber

Instabilities in Liquid Metal Batteries

Fluid flows in liquid metal batteries influence their efficiency, but also their safe operation crucially.
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Foto: Glove box battery laboratory ©Copyright: ©Michael Nimtz

Experiments with Liquid Metal Battery Cells

In the battery laboratory, different types of cells and different chemistries are tested. Activities, efficiencies and corrosive properties are examined.
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Foto: Lithium liquid metal electrode ©Copyright: ©Steffen Landgraf, Michael Nimtz

Energy Storage and Energy Con­version with Liquid Metals

Liquid metals offer a range of benefits when used for energy storage and energy con­version: cost-effective production, high cycle numbers and high scalability
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Foto: Liquid metal battery ©Copyright: Dr. Norbert Weber

Mass transfer in liquid metal batteries

Mass transfer substantially determines the cell voltage of liquid metal batteries.
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Foto: Na-Bi liquid metal battery ©Copyright: Steffen Landgraf

Modelling of molten salt electrolytes

Mass transfer in molten salt electrolytes determines the efficiency of liquid metal batteries.
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Foto: Cell designs for liquid metal batteries ©Copyright: Dr. Martins Sarma

Battery engineering

An optimized cell design is fundamental for a long lifetime of a liquid metal battery.
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Foto: liquid metal battery casing at operating temperature (detail) ©Copyright: Dr. Martins Sarma

Collection of thermophysical properties for liquid metals and molten salts salts

The determination of material properties for liquid metals and molten salts typically entails a substantial investment of time and effort. An up-to-date and freely available database facilitates the retrival of thermophysical properties.
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Foto: corroded cell housing ©Copyright: Dr. Martins Sarma

Corrosion

Corrosion is investigated especially in molten salts. Electrochemical approaches are used together with ICP-MS, REM-EDX and others.
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Foto: X-ray image of a liquid metal battery ©Copyright: Dr. Martins Sarma

Radiography of liquid metal batteries

Neutrons and X-rays are used to visualize processes in liquid metal batteries. Cells imaging is performed in operando at temperatures exceeding 600°C.
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Foto: Battery module ©Copyright: Martin Herzberg

Battery system engineering

Large batteries need to be well insulated in order to reach a high efficiency. At the same time, the insulation should not be too thick because otherwise the cells need to be cooled during operation.
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Foto: EVF lateral ©Copyright: Dr. Norbert Weber

Numerical Simulation of Liquid Metal Batteries

Numerical simulation allows a fast and easy study of the operating performance of liquid metal batteries.
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Foto: Logo SOLSTICE ©Copyright: HZDR / Blaurock

Projects of the research group on liquid metal batteries

The research group on liquid metal batteries carries out a number of third party funded projects related to high-temperature electrochemistry and battery fluid dynamics.
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