Preparation of BF3 Carbonates and their Electrochemical Investigation as Additives in Lithium Ion Batteries
Date of Original Version
This study reports the behavior of the compounds BF3•D (with D = dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, propylene carbonate) as electrolyte additives in Li[Ni0.33Co0.33Mn0.33O2]/graphite cells with LiPF6 (1 M) in EC:EMC (3:7 wt%) as electrolyte. The adducts were prepared from gaseous BF3 with the corresponding carbonates in a simple Lewis acid base reaction and fully characterized (FT-IR and NMR spectroscopy, single crystal X-ray diffraction). The electrochemical behavior of the additives was examined at concentrations of 1 wt% and 0.25 wt% added to the electrolyte. Electrochemical impedance spectroscopy of cells with 1 wt% additive, display a significantly lower cell impedance than cells without additive, but also a slightly decreased capacity. To combine the high capacity retention with a low cell impedance the concentration of the additive was reduced. Thus, cell testing with 0.25 wt% additive incorporated with the electrolyte showed no difference in capacity retention after 55 cycles at 25 °C, but had lower cell impedance. The rate-performance test shows a higher capacity retention for cells with additive at high C-rates. The surface chemistry of the electrodes was studied by X-ray photoelectron spectroscopy and suggests that the additives react on both electrodes (Li[Ni0.33Co0.33Mn0.33O2] and graphite) and improve the electrode interphases.
Journal of the Electrochemical Society
Eisele, Lea, Nina Laszczynski, Marius Schneider, Brett Lucht, and Ingo Krossing. "Preparation of BF3 Carbonates and their Electrochemical Investigation as Additives in Lithium Ion Batteries." Journal of the Electrochemical Society 167, 6 (2020). doi:10.1149/1945-7111/ab80ad.