Lithium sulfonyl silica (LSS) was synthesized by replacing the surface -H group in fumed silica with (CH2)(3)SO3Li and adopted as electrolyte additive for lithium ion battery. 3 wt% of the synthesized particles in 1 M LiPF6 (EC/DMC = 1:1) showed improved ionic conductivity and better potential stability over the pristine electrolyte. The discharge capacity of the LiCoO2/graphite is particularly enhanced with the addition of LSS at higher C-rates due to the enhanced ionic conductivity at room temperature. The LiCoO2/graphite cells using 1.0 M LiPF6/EC/DMC (1:1) and 1.0 M LiTFSI/EC/DMC (1:1) with LSS also showed superior performance for the self-discharge test carried out at 45 degrees C for 200 days. These positive impacts of LSS on LiCoO2/graphite cells warrant its use in lithium ion batteries.