Rechargeable Li-CO2 batteries are regarded as the ideal application for the superior energy storage technology. However, they still limited by the lack of high efficiency electrocatalyst and limited understanding for the electrochemical reaction mechanism. In this work, we prepared the Ir-CNT composite by a rotation hydrothermal method, which remarkably promoted the reaction kinetics and enhanced the electrocatalytic performance of Li-CO2 batteries. The incorporation of Ir nanoparticles shows high activity enhancement for the adsorption of Li2CO3 species, which was confirmed by density functional theory (DFT) calculations. The Ir-CNT cathode exhibited an excellent ability to catalyze the formation and decomposition of Li2CO3 during cycling. Therefore, a large specific capacity of 10325.9 mAh g−1 and an excellent high rate cyclability with stably over 100 cycles were achieved. The three-dimensional Ir-CNT cathode could spontaneously advance the electrocatalytic activity of CO2 oxidation and precipitation to increase specific capacities and cycle life, significantly boosting the practical application of Li-CO2 batteries.