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Abstract: Li‐CO2 batteries could skillfully combine the reduction of “greenhouse effect” with energy storage systems. However, Li‐CO2 batteries still suffer from unsatisfactory electrochemical performances and their rechargeability is challenged. Here, it is reported that a composite of Ni nanoparticles highly dispersed on N‐doped graphene (Ni‐NG) with 3D porous structure, exhibits a superior discharge capacity of 17 625 mA h g−1, as the air cathode for Li‐CO2 batteries. The batteries with these highly efficient cathodes could sustain 100 cycles at a cutoff capacity of 1000 mA h g−1 with low overpotentials at the current density of 100 mA g−1. Particularly, the Ni‐NG cathodes allow to observe the appearance/disappearance of agglomerated Li2CO3 particles and carbon thin films directly upon discharge/charge processes. In addition, the recycle of CO2 is detected through in situ differential electrochemical mass spectrometry. This is a critical step to verify the electrochemical rechargeability of Li‐CO2 batteries. Also, first‐principles computations further prove that Ni nanoparticles are active sites for the reaction of Li and CO2, which could guide to design more advantageous catalysts for rechargeable Li‐CO2 batteries. [ABSTRACT FROM AUTHOR]