Local, small scale short-circuits in liquid metal batteries
When cycling liquid metal batteries, local short circuits have been observed several times. They manifest e.g. in the cell voltage. Fig. 1. shows one example: the sudden drop of the terminal voltage is a clear evidence of a short circuit of the battery. At the same time, a certain increase in cell temperature might be observed.
Fig. 1: Charge-discharge curve of a Li-Bi liquid metal battery with short-circuits during operation.
Picture: Norbert Weber
After dismantling used cells, the cathode metal can sometimes be found attached to the anode current collector. Fig. 2 shows one example: the small metallic deposits are in fact a mixture of Li and Bi. During normal operation, such effects should not occur. They can only be explained by small, localised short-circuits.
Fig. 2: Anode of a Li-Bi liquid metal battery after localised short circuits.
Picture: Steffen Landgraf
Such small-scale short-circuits can, amongst others, be explained by insufficient wetting of the current collector by the molten metal. Fig. 3 shows one example: as the molten Li does not wet the wire, large Li-droplets form. If these droplets grow too much, they might induce local short-circuits.
Fig. 3: Anode of a liquid metal battery with insufficient wetting of the current collector.
Picture: Steffen Landgraf
Publications
- Bénard, S.; Weber, N.; Horstmann, G.M.; Landgraf, S.; Weier, T.
Anode-metal drop formation and detachment mechanisms in liquid metal batteries
Journal of Power Sources 510(2021) 230339