Li and ~19F diffusion coefficients and thermal properties of non-aqueous electrolyte solutions for rechargeable lithium batteries

摘要

In this paper, electrolyte solutions of ethylene carbonate (EC) and ethylene methylene carbonate (EMC) with different salts as LiPF_6, LiBF_4 and LiN(SO_2C_2F_5)_2 were prepared and characterized using Pulsed Field Gradient (PFG) NMR and DSC. Cation transport numbers, T~+, ranging between 0.37 and 0.49 were obtained. The maximum value of 0.49 was obtained in the case of a 0.5 M solution of LiBF_4 in 2:8 EC:EMC. The DSC data suggest that the increase of EMC stabilizes the electrolyte solution towards low temperature, and that a 2:8 EC:EMC ratio assures good stabi1ity at low temperature to the electrolyte solution. While LiN(SO_2C_2F_5)_2 seems to score the best in terms of low temperature stability, LiPF_6 may offer the best cost/performances compromise.