gamma-Butyrolactone (GBL) increases the irreversible capacity of lithium ion battery when it is employed as the solvent for the lithium bis(oxalate)borate (LiBOB)-based electrolyte. To solve this problem, four sulfites are introduced to the electrolyte. The effects of ethyl sulfite (ES), propylene sulfite (PS), dimethyl sulfite (DMS) and diethyl sulfite (DES) on the LiBOB/GBL-based electrolytes are studied. The ionic conductivity, electrochemical stability, cycle performance and thermal stability of the sulfite containing electrolytes are tested and compared with that of the common electrolyte and the 1 M LiBOB/GBL electrolyte. The results indicate that the cyclic sulfites ES and PS show little benefit to the performance of the electrolyte. However, the linear sulfites DMS and DES could increase the ionic conductivity of the electrolyte and form an effective SEI film on the anode surface. In particular, the 1 M LiBOB/GBL + DMS (3:1 wt.) electrolyte mitigates the irreversible capacity and enhances the first coulomb efficiency and the capacity retention. The thermal stability of the DMS containing electrolyte is also improved and is better than that of the common electrolyte. These beneficial effects make them possibly to be a promising cosolvent for the LiBOB/GBL electrolyte. (C) 2010 Elsevier B.V. All rights reserved.