Impact of Solid Electrolyte Interphase lithium salts on cycling ability of Li-ion battery: Beneficial effect of glymes additives

International audienceThe Solid Electrolyte Interphase (SEI), formed during the first cycles of life in lithium-ion batteries, contains a variety of lithium salts, with direct effect on the aging performance of the battery. In this work, we investigate the impact of addition of SEI lithium salts (LiF, Li2CO3, LiOH, Li2O, LiOCH3 and LiOC2H5) in the electrolyte on the cycling ability of graphite and LiNi1/3Mn1/3Co1/3O2 (NMC) electrodes. Results show that NMC is more sensitive to salt addition than graphite material. Furthermore, results demonstrate that both LiOH and Li2O have a negative effect on the SEI formation. Conversely, Li2CO3, LiOCH3 and LiOC2H5 are beneficial and promote the formation of a polymeric coating on the SEI. Finally, the impact of the presence of LiF on the SEI depends mainly on its concentration. The effect of the presence of additives capable of complexing lithium salts such as the glyme series, CH3O[CH2CH2O]nCH3 (Gn, with n = 2, 3 or 4), is investigated by cyclic voltammetry, galvanostatic charge–discharge tests and electrochemical impedance spectroscopy (EIS). Results show that the glymes chain length is a determining factor in their complexation mechanism, which depends on both the nature and the concentration of the lithium salt