Effects of 3,5-bis(trifluoromethyl)benzeneboronic acid as an additive on electrochemical performance of propylene carbonate-based electrolytes for lithium ion batteries

The effects of 3,5-bis(trifluoromethyl)benzeneboronic acid (BA) as a new film-forming additive have been theoretically and experimentally studied for a graphite (CMS) electrode in propylene carbonate-based (PC) electrolyte for lithium ion batteries. Calculation based on the density functional theory (DFT) method suggests that the energy of the LUMO (the lowest unoccupied molecular orbital) of BA is lower than that of PC, consistent with the results of cyclic voltammograms that BA is reduced before PC. SEM, FT-IR and XPS measurements show that the reduced products of BA contribute in part to the effective SEI film on the graphite electrode surface. Discharge-charge measurements indicate that the addition of BA can effectively prevent the decomposition and the co-intercalation of PC, and lithium ions can reversibly intercalate into and deintercalate from the graphite electrode. These results show that addition of BA improves the electrochemical performance of graphite in PC-based electrolyte. (C) 2008 Elsevier Ltd. All rights reserved.