Inhibition of solid electrolyte interface formation on cathode particles for lithium-ion batteries

Thermal reactions between cathode particles (LiNi0.8CO0.2O2, LiCoO2, LiMn2O4 and LiFePO4) and ternary electrolyte (1.0 M LiPF6 in 1: 1: 1 diethyl carbonate/dimethyl carbonate/ethylene carbonate) with or without the thermal stabilizing additive dimethyl acetamide (DMAc) have been investigated. Ternary electrolyte reacts with the surface of lithiated metal oxides (LiNi0.8Co0.2O2, LiCoO2 and LiMn2O4) upon storage to corrode the surface and generate a complex mixture of organic and inorganic surface species, but the bulk ternary electrolyte does not decompose. There is little evidence for reaction between the surface of carbon coated LiFePO4 and ternary electrolyte upon storage at elevated temperature (>60 degrees C), but the bulk ternary electrolyte decomposes. Addition of DMAc to ternary electrolyte reduces the surface corrosion of the lithiated metal oxides and stabilizes the electrolyte in the presence of LiFePO4. (C) 2007 Published by Elsevier B.V.