Molten salts and energy related materials

Abstract

Molten salts have been known for centuries and have been used for the extraction of aluminium for over one hundred years and as high temperature fluxes in metal processing. This and other molten salt routes have gradually become more energy efficient and less polluting, but there have been few major breakthroughs. This paper will explore some recent innovations that could lead to substantial reductions in the energy consumed in metal production and in carbon dioxide production. Another way that molten salts can contribute to an energy efficient world is by creating better high temperature fuel cells and novel high temperature batteries, or by acting as the medium that can create novel materials that can find applications in high energy batteries and other energy saving devices, such as capacitors. Carbonate melts can be used to absorb carbon dioxide, which can be converted into C, CO and carbon nanoparticles. Molten salts can also be used to create black silicon that can absorb more sunlight over a wider range of wavelengths. Overall, there are many opportunities to explore for molten salts to play in an efficient, low carbon world.

Electrolytes for electrochemical energy storage

“…For example, there are more than 50 MCFC based stationary power stations being commissioned around the world producing over 300 MW of clean electric powder. 338 Fig. 39 shows the schematic drawing of an MCFC.…”

Molten Salt Electrometallurgy

“…The current efficiency ξe for Ti extraction using this process is low (< 2000 ppm oxygen, ξe = 32.3 %) but relatively high for Cr extraction (< 2000 ppm oxygen, ξe > 70 %) [41]. Although oxygenevolving inert anodes could improve ξe, the several 100 patents describing such anodes in Hall-Héroult cells are not totally satisfactory [6]. Thus, utilising liquid metal anodes [42] may lead to less polluting and more energy efficient electro-deoxidation relative to using carbon-based anodes.…”

Solid electrolyte membrane-containing rechargeable high-temperature molten salt electrolyte-based batteries

“…Furthermore, these molten salt electrolytes have exceptional electrochemical properties such as ultrahigh ion conductivities and wide electrochemical windows, allowing for more affordable electrode materials and electrochemical redox processes for HT-MSBs. 16–18 On the other side, HT-MSBs are specific high-temperature electrochemical energy storage devices that involve heat and electricity, capable of collaborating with other high-temperature energy conversion technologies such as molten salt thermal energy storage (MS-TES) and high-temperature steam electrolysis (HTSE) to construct a multi-energy complementary utilization system. 19–21…”

“…Furthermore, these molten salt electrolytes have exceptional electrochemical properties such as ultrahigh ion conductivities and wide electrochemical windows, allowing for more affordable electrode materials and electrochemical redox processes for HT-MSBs. [16][17][18] On the other side, HT-MSBs are specic hightemperature electrochemical energy storage devices that involve heat and electricity, capable of collaborating with other hightemperature energy conversion technologies such as molten salt thermal energy storage (MS-TES) and high-temperature steam electrolysis (HTSE) to construct a multi-energy complementary utilization system. [19][20][21] Various HT-MSB devices for large-scale electricity storage are currently being developed, including sodium sulfur (NAS) batteries, [22][23][24] Na-NiCl 2 (ZEBRA, ZEolite Battery Research Africa) and sodium metal-halide (Na-MH) batteries, [25][26][27][28][29] liquid metal batteries (LMBs), [30][31][32] solid electrolyte-based liquid lithium (SELL) batteries, [33][34][35] and molten air batteries (MABs).…”