Influencing Factors and Challenges on the Wettability of Electrode in Molten Salt

Abstract

Molten salts play an important role in the electrolysis of solid metal compounds, especially oxides and sulfides, and have an impressive storage capacity and power, so they are now the electrolyte for many new types of rechargeable batteries. Unfortunately, due to the high viscosity and high surface tension of molten salt, the unsatisfactory wettability of electrode and molten salt restricts the development of molten salt electrochemistry. In the past half century, research on interface phenomena has been devoted to establishing more accurate models for measuring surface tension and wetting angle, developing more scientific wetting angle measurement techniques, and exploring the influencing factors of wettability. Different from a water solution interface, molten salt experiment are performed in high temperature and pressure environments, making it difficult to test the wetting angle, and there has been little research on the interface phenomenon of molten salt. In this Review, on the basis of existing models and experimental data, the factors and mechanisms that lead to the difference of wettability between melt and solid matrix in molten salt systems are analyzed in detail. Finally, we put forward the prospects and suggestions for the study of the wettability of melt to solid substrate in molten salt.

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“…The appropriate wetting of the graphite anode by the molten salt electrolyte, characterised by a small contact angle, can promote the kinetic of the oxidation reaction and overall process. 32 It should be mentioned that the oxygen gas bubbles generated on the anode can be timely detached from the anode when the wettability between the anode and electrolyte is at a desirable level. 29 At lower values of wettability, the bubble film developed on the surface of anode can provide an electronically insulating layer, leading to an undesirable voltage loss within the electrolysis cell.…”