nCocktail Therapy towards High Temperature/High Voltage Lithium Metal Battery via Solvation Sheath Structure Tuning

Abstract Lithium metal battery has attracted tremendous attention because of its superior energy density. However, it suffers poor cyclic stability and serious safety risk due to severe side reactions between lithium and electrolyte solution, and excessive growth of lithium dendrite, which can be even worse at high temperatures and high voltage. To tackle this issue, solvation structure manipulation is carried out in the ADFN electrolyte solution, containing co-solvents of dimethoxy ethane (DME), Fluoroethylene carbonate (FEC), adiponitrile (ADN), and Lithium bis(fluorosulfonyl)imide (LiFSI, 1.0 M), and lithium nitrate (LiNO3, 0.1 M). A large-sized solvation sheath with a more inorganic component is constructed as indicated by both the molecular dynamic simulation and Raman characterization. The unique solvation structure generates a stable SEI layer rich in inorganic species, which suppresses continuous consumption of electrolyte solvent and inhibits lithium dendrite growth as confirmed by both SEM and XPS analysis. The electrochemical performance is boosted with respect to the Li||Cu, Li||Li, Li||LFP and Li||NCM523 cells via the solvation structure tuning in the ADFN electrolyte solution. Improved cyclic stability, reversible capacities, and rate performance are demonstrated by both the Li||LFP and Li||NCM523 cells, where the Li||LFP cells exhibit outstanding performance at both room temperature and high temperatures of 80 °C and 90 °C. This work provides fundamental insights about the ADN solvation and innovative strategy to manipulate the solvation of lithium ions, which delivers a simple way to further optimize Li-ion electrolyte for wide-temperature and high voltage applications.