LiBF3Cl as an alternative salt for the electrolyte of Li-ion batteries

LiBF3Cl was synthesized by reacting BF3 etherate and LiCl in an organic media, and evaluated as a salt for the electrolyte of Li-ion batteries. XRD results showed that LiBF3Cl has the same crystallographic structure as LiBF4 except for little difference in the lattice parameter. With a 3:7 (w/w) solvent blend of ethylene carbonate and ethyl methyl carbonate, LiBF3Cl electrolyte was found to have lower liquidus temperature than LiBF4 analogue either due to its higher solubility or due to its higher tendency in forming a super-cooling solution, which was related to the less symmetry of BF3Cl- anion. Meanwhile, LiBF3Cl electrolyte displayed excellent ability in passivating Al at high potentials due to the similar chemical composition of LiBF3Cl and LiBF4. Most importantly, the LiBF3Cl electrolyte was superior to the LiBF4 electrolyte in facilitating the formation of solid electrolyte interphase (SEI) on graphite electrode, which not only increased Coulombic efficiencies of the SEI formation, but also prolonged cycle life of the Li-ion batteries. The merits above make LiBF3Cl very promising as an alternative lithium salt for the electrolyte of Li-ion batteries. Published by Elsevier B.V.