A novel dimethyl sulfoxide/1,3-dioxolane (DMSO/1,3-DO) based electrolyte is proposed for lithium/carbon fluorides (Li/CFx) batteries to enhance the discharge voltage plateau and energy density. Conductivities of the electrolyte of 1molL−1 LiBF4/DMSO+1,3-DO with different volume ratios are not identical, which have a maximum of 14.85mScm−1. From the tests of galvanostatic discharge, the discharge voltage plateau of the Li/CFx battery with an electrolyte of 1molL−1 LiBF4/DMSO+1,3-DO (5:5, v:v) can reach 2.69V at 0.1C, delivering a maximum discharge capacity of 831mAhg−1 and the highest energy density of 2196Whkg−1. Compared to Li/CFx batteries with an electrolyte of 1molL−1 LiBF4/PC+DME (5:5, v:v), the energy density of Li/CFx batteries with an electrolyte of 1molL−1 LiBF4/DMSO+1,3-DO (5:5, v:v) has been improved more than 12%. With the help of XRD, SEM, TEM, EIS, FT-IR and GC-MS analysis, the results of this work suggest that DMSO/1,3-DO based electrolyte can significantly improve the discharge performance of Li/CFx batteries and keep a good electrochemical stability during discharge. The main reason for improvement of discharge performance is decreasing of both the overpotential of electrochemical polarization of CFx cathodes during discharge and the overpotential of ohmic polarization by increasing the ion conductivity of electrolyte.