Understanding the Dual-Phase Synergy Mechanism in MnO-MnO Catalyst for Efficient Li-CO Batteries.

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