Improving wettability by constructing a chromium transition layer to enhance voltage efficiency of liquid metal batteries

Liquid metal batteries (LMBs) based on liquid metal electrodes and molten salt electrolytes, are deemed as one of the most promising technologies for large-scale energy storage, due to the advantages of long-lifespan, low-cost and high-safety. Nevertheless, the issue of inadequate wettability between the collectors and the liquid electrodes in LMBs hinders the electrode reaction kinetics, resulting in a considerable polarisation voltage and, consequently, a reduction in the voltage efficiency of the cell. This work proposes a novel strategy for the construction of a self-generated Cr-C transition layer at the graphite collector/electrode interface, utilising Cr as a cathode additive with the objective of enhancing interfacial wettability. It was demonstrated that the formation of a Cr-C transition layer resulted in an increase in the contact area at the collector/cathode interface, as well as the reaction area at the electrolyte/cathode interface. This led to an acceleration in the kinetics of the electrode reaction. As a consequence, the voltage efficiency of Li||Sb-Sn cells was enhanced from 86.10% to 89.91%. In particular, the improvement in energy efficiency is more pronounced with an increase in the charge/discharge rate, and a reasonable proportion of chromium addition does not have a detrimental impact on battery performance. Graphical