In this paper, we propose a new electrolyte additive 3-Isocyanatopropyltriethoxysilane (IPTS) to improve the cycle stability and rate performance of Ni-Rich (LiNi0·6Co0·2Mn0·2O2) cathode half-cell. Density function theory calculations suggest that IPTS has higher HOMO energy than solvent, which can decompose preferentially. Moreover, we confirm the oxidative decomposition by the linear scanning cyclic voltammetry, which can achieve stable at a cutoff voltage of 2.5–4.5 Vs. (Li/Li+). The cyclic voltammetry curves at different scan rates indicate that the migration rate of lithium ions is higher in the cells with 0.5% additive than in the base electrolyte. After 150 cycles, the capacity retention rates in the base electrolyte and in the additive-containing electrolyte are 55.4% and 73.1%, respectively. X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy show that the additive is involved in film formation, and the obtained CEI film is very uniform and dense, which play a key role in stabilizing the electrolyte under high voltage.