Concentrated Electrolytes for Lithium Metal Negative Electrodes

Lithium metal is one of the most promising negative electrodes for high-energy-density rechargeable batteries, but its critical problem is low Coulombic efficiency resulting from the reductive decomposition of an electrolyte thereon, which has hampered its commercial applications. Various electrolytes and additives have been proposed to form a stable interphase between Li metal and electrolyte. Among them, salt-concentrated electrolytes have been most extensively studied, which create a unique anion-derived interphase that can highly stabilize the Li metal/electrolyte interface. The optimization of the salt–solvent combinations as well as the salt concentration enables us to achieve high Coulombic efficiency of over 99%. Herein the unique interphasial properties of concentrated electrolytes, as well as other beneficial interfacial/bulk properties such as extended potential windows, prevented metal corrosion, accelerated electrode reactions, increased transference number and decreased volatility/flammability, are discussed with a focus on their peculiar coordination structures.