Research progress in anode protection of lithium metal batteries by electrolyte chemistry

Lithium metal batteries have been considered as one of the most promising high-energy-density energy storage devices, however, the low Coulombic efficiency and uncontrolled dendrite growth seriously hinder their commercialization. In lithium metal batteries, the electrolytes would directly participate in the formation of solid electrolyte interface (SEI) , which play important roles in affecting the lithium metal anode Coulombic efficiency and inhibiting the growth of lithium dendrites. In the traditional LiPF6 based ester electrolyte, lithium metal anode exhibits low Coulomb efficiency and serious lithium dendrites. In recent years, significant improvement has been achieved for the protection of lithium anode through manipulating the electrolyte additive, solvents, lithium salt and lithium salt concentration, etc. For examples, ether solvent presenting better compatibility with lithium metal was selected to reduce the side reactivity of electrolyte with lithium metal;varieties of additives were adopted to suppress the formation of lithium dendrites; high concentration electrolytes were employed to form stable SEI. In this paper, the growth principles of lithium dendrites, the research status of electrolytes chemistries for protection of lithium metal anode by means of solvents, lithium salts, additives and high concentration electrolytes strategies were reviewed and the advantages and limitations of various approaches were summarized. New insights on the development of electrolytes chemistries were also put forward to stimulate new strategies to face the subsequent challenges of lithium-metal batteries.