Rechargeable Li–CO2 batteries recently have gained an increasing popularity because they can directly reduce fossil fuel consumption and convert chemical energy of greenhouse gas CO2 into electric energy. However, Li–CO2 batteries still suffer from great challenges to realize long-term cycling due to a high charging voltage to drive the electrochemical decomposition of discharge products Li2CO3. Herein, porous NiO nanofibers obtained by electrospining technique are firstly served as a high-efficient cathode catalyst in Li–CO2 batteries. The addition of NiO not only improves the catalytic performance of batteries but also tailors the cathode structure. Experimental results and theoretical calculation show the existence of NiO facilitates a conformal growth of Li2CO3 on the NiO surface with large contact areas, which promotes the decomposition of Li2CO3 among charging process. Owing to these synchronous advantages, enhanced electrochemical performances including high capacity, superior round-trip efficiency and especially the long cycling-life are achieved.