Molecular Simulation and Performance Prediction of High-Temperature Molten-Salt Batteries

This research aims to enhance the discharging rate and to improve the overall performance of a high-temperature molten salt battery. We use molecular dynamics (MD) simulation techniques to develop some novel ternary and quaternary molten electrolytes to replace conventional binary LiCl–KCl ones [1]. These novel electrolytes are listed in Table I  and their molecular structures are shown in Figure 1. These molecular structure configurations are based on their minimal total energies and we use Hamiltonian dynamics to predict their trajectories and subsequent properties.

Our simulation results are consistent with the results of previous experimental studies regarding the LiCl-LiBr-based ternary (LiCl–LiBr–NaCl & LiCl–LiBr–NaBr) and quaternary (LiCl–LiBr–NaCl–KCl & LiCl–LiBr–NaBr–KBr) electrolytes. The simulation results with greater ionic conductivity and higher melting points are consistent with experimental results reported by previous literatures [2, 3]. The tendency is shown in Figure 2. In addition, the MD results have found that the lithium ion mole fraction in the molten-salt electrolytes affects the ionic conductivity significantly as shown in Figure 3.

This paper demonstrates that MD simulation technique is a useful tool to screen various design ideas on the multi-component electrolytes in a more efficient way. The molecular composition of each component of the molten-salt electrolytes can be optimized using this simulation technique instead of trial-and-error experiments. The target region shown in Figure 4 is easy to easy to achieve through this computational technique.

REFERENCES

1. P. Masset, and R. A. Guidotti, J. Power Sources, 164, 397 (2007).
2. S. Fujiwara, M. Inaba, and A. Tasaka, J. Power Sources, 196, 4012 (2011).
3. S. Fujiwara, U. S. Patent, US008221912B2 (2012).