Electrolyte additive to improve performance of MCMB/LiNi1/3Co1/3Mn1/3O2 Li-ion cell

The electrolyte additive, 3,9-divinyl-2,4,8,10-tetraoxaspiro[5,5] undecane (TOS), was investigated as a means to improve the life of mesocarbon microbead (MCMB)/Li-1.1 [Ni1/3Co1/3Mn1/3](0.9)O-2 (NCM) cells for high-power applications. With the addition of an appropriate amount of TOS (no more than 1 wt%) to MCMB/NCM cells, the capacity retention was significantly improved at 55 C compared with cells containing pristine electrolyte. Aging tests at 55 C indicated that the capacity retention of the negative electrode had benefited as a result of the formation of a stable passivation film at the surface of the carbon electrode due to TOS reduction. Electrochemical impedance spectroscopy showed that a TOS addition of more than 0.5 wt% increased the cell interfacial impedance. Differential scanning calorimetry showed that the thermal stability of lithiated MCMB was also improved with the TOS addition. (C) 2010 Elsevier B.V. All rights reserved.