MOF-Derived CoSe Nanoparticles/Carbonized Melamine Foam as Catalytic Cathode Enabling Flexible Li-CO Batteries with High Energy Efficiency and Stable Cycling.

Rechargeable aprotic Li-CO batteries have aroused worldwide interest owing to their environmentally friendly CO fixation ability and ultra-high specific energy density. However, its practical applications are impeded by the sluggish reaction kinetics and discharge product accumulation during cycling. Herein, a flexible composite electrode comprising CoSe nanoparticles embedded in 3D carbonized melamine foam (CoSe/CMF) for Li-CO batteries is reported. The abundant CoSe clusters can not only facilitate CO reduction/evolution kinetics but also serve as LiCO nucleation sites for homogeneous discharge product growth. The CoSe/CMF-based Li-CO battery exhibits a large initial discharge capacity as high as 5.62 mAh cm at 0.05 mA cm, a remarkably small voltage gap of 0.72 V, and an ultrahigh energy efficiency of 85.9% at 0.01 mA cm, surpassing most of the noble metal-based catalysts. Meanwhile, the battery demonstrates excellent cycling stability of 1620 h (162 cycles) at 0.02 mA cm with an average overpotential of 0.98 V and energy efficiency of 85.4%. Theoretical investigations suggest that this outstanding performance is attributed to the suitable CO/Li adsorption and low LiCO decomposition energy. Moreover, flexible Li-CO pouch cell with CoSe/CMF cathode displays stable power output under different bending deformations, showing promising potential in wearable electronic devices.