Lithium Bis(fluorosulfony)imide-Lithium Hexafluorophosphate Binary-Salt Electrolytes for Lithium-Ion Batteries: Aluminum Corrosion Behaviors and Electrochemical Properties

摘要

Aluminum corrosion behaviors and electrochemical properties of Lithium bis(fluorosulfony)imide (LiFSI)-lithium hexafluorophosphate (LiPF6) binary-salt electrolytes containing mixtures of LiFSI and LiPF6 (with a total salt content of 1.2 mol L~(-1)) with different molar ratios in EC/EMC (3:7, by vol.) solutions are systematically investigated. Our experimental results from cyclic voltammetry, scanning electron microscopy (SEM), chronoamperometry and the charge-discharge measurements of Li/LiNi_(1/3) Co_(1/3)Mn_(1/3)O2 half-cells demonstrate that the LiFSI-LiPF6 binarysalt electrolytes with the LiFSI concentrations lower than 0.3 mol L~(-1) exhibit not only passivating aluminum current collectors at 4.3 V vs. Li~+/Li, but also improved cycling performance. Meanwhile, Artificial Graphite/LiNi_(1/3)Co_(1/3)Mn_(1/3)O2 (AG/ NMC111) pouch cells made with the LiFSI(0.2)-LiPF6 (1.0) electrolyte with the LiFSI concentration of 0.2 mol L~(-1) display an excellent cycling stability with 93.9% capacity retention at 1℃ rate after 360 cycles, and enhanced capacity retention at -20 ℃, 60 ℃ and after 55 ℃ storage for 30 days compared to cells with 1.2 mol L~(-1) LiPF6/EC-EMC conventional electrolyte. This work confirms that binary-salt electrolytes system, such as LiFSI-LiPF6, may be a promising method to enhance the longevity and storage properties of Li-ion batteries.