Understanding the Dual-Phase Synergy Mechanism in Mn 2 O 3 –Mn 3 O 4 Catalyst for Efficient Li–CO 2 Batteries

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Rechargeable Li–CO 2 batteries have been receiving intense interest because of their high theoretical energy density and environmentally friendly CO 2 fixation ability. However, due to the sluggish CO 2 reduction/evolution reaction (CRR/CER) kinetics, the current Li–CO 2 batteries still suffer from severe polarization and poor cycling stability. Herein, we designed and in situ synthesized sea urchinlike Mn 2 O 3 –Mn 3 O 4 nanocomposite and explored the synergistic effect between Mn 2 O 3 and Mn 3 O 4 during charge–discharge process in Li–CO 2 batteries. It is found that Mn 3 O 4 can effectively promote the kinetics of CRR process, and Mn 2 O 3 can induce the nucleation of Li 2 CO 3 and promote its decomposition (CER). Benefiting from the dual-phase synergy, the Mn 2 O 3 –Mn 3 O 4 cathode combines the respective catalytic advantages of the both and delivers a high full discharge capacity of 19 024 mAh g –1, a low potential gap of 1.24 V, and durable cycling stability (1380 h) at a current density of 100 mA g –1 . Moreover, based on experimental results and density functional theory (DFT) calculations, a charge–discharge process model of the Mn 2 O 3 –Mn 3 O 4 cathode was established to display the electrochemical reaction mechanism. We hope that this design strategy can encourage further studies for efficient cathode catalysts to accelerate the practical application of Li–CO 2 batteries and even the metal–air batteries.