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With the verification of the existence of the dissolution-electrodeposition mechanism during the electro-reduction of solid silica in molten CaCl 2 , the present study not only provides direct scientific support for the controllable electrolytic extraction of nanostructured silicon in molten salts but it also opens an avenue to a continuous silicon extraction process via the electro-deposition of dissolved silicates in molten CaCl 2 . In addition, the present study increases the general understanding of the versatile material extraction route via the electro-deoxidization process of solid oxides in molten salts, which also provokes reconsiderations on the electrochemistry of insulating compounds.

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h i g h l i g h t s g r a p h i c a l a b s t r a c t Electrochemical behavior of the LieBi system was investigated for liquid metal cells. Lithium insertion kinetics in liquid bismuth were studied in a threeelectrode cell. LijLiCleLiBrjBi cells showed long life, high efficiency, and low fade rate. System scalability demonstrated in prototypes with 10 and 100 times original capacity. Robustness shown by cooling to solidify cell, followed by heating and recycling. a b s t r a c tIn an assessment of the performance of a LijLiCleLiFjBi liquid metal battery, increasing the current density from 200 to 1250 mA cm À2 results in a less than 30% loss in specific discharge capacity at 550 C. The charge and discharge voltage profiles exhibit two distinct regions: one corresponding to a LieBi liquid alloy and one corresponding to the two-phase mixture of LieBi liquid alloy and the intermetallic solid compound, Li 3 Bi. Full cell prototypes of 0.1 Ah nameplate capacity have been assembled and cycled at 3 C rate for over a 1000 cycles with only 0.004% capacity fade per cycle. This is tantamount to retention of over 85% of original capacity after 10 years of daily cycling. With minimal changes in design, cells of 44.8 Ah and 134 Ah capacity have been fabricated and cycled at C/3 rate. After a hundred cycles and over a month of testing, no capacity fade is observed. The coulombic efficiency of 99% and energy efficiency of 70% validate the ease of scalability of this battery chemistry. Post mortem cross sections of the cells in various states of charge demonstrate the total reversibility of the Li 3 Bi solid phase formed at high degrees of lithiation.

The increasing demands for integration of renewable energy into the grid and urgently needed devices for peak shaving and power rating of the grid both call for low‐cost and large‐scale energy storage technologies. The use of secondary batteries is considered one of the most effective approaches to solving the intermittency of renewables and smoothing the power fluctuations of the grid. In these batteries, the states of the electrode highly affect the performance and manufacturing process of the battery, and therefore leverage the price of the battery. A battery with liquid metal electrodes is easy to scale up and has a low cost and long cycle life. In this progress report, the state‐of‐the‐art overview of liquid metal electrodes (LMEs) in batteries is reviewed, including the LMEs in liquid metal batteries (LMBs) and the liquid sodium electrode in sodium‐sulfur (Na–S) and ZEBRA (Na–NiCl2) batteries. Besides the LMEs, the development of electrolytes for LMEs and the challenge of using LMEs in the batteries, and the future prospects of using LMEs are also discussed.