A highly efficient and free-standing copper single atoms anchored nitrogen-doped carbon nanofiber cathode toward reliable Li–CO2 batteries

In recent years, lithium–carbon dioxide (Li–CO2) batteries have received extensive attention due to their high energy density and environmental friendliness. However, the high charging voltage makes it difficult to withstand a large current density, resulting in the low energy efficiency. Herein, nitrogen-doped carbon nanofibers with copper single atoms (Cu/NCNF) were developed as free-standing cathodes for Li–CO2 batteries. The Cu/NCNF sample was prepared by electrospinning and two-step heat treatment along with a meteorological deposition method. The electrochemical performances show that the Li–CO2 battery with Cu/NCNF possesses a high specific capacity (14084 mAh/g at a current density of 100 mAh/g), a low polarization of 1.29 V, and a long-life stability of 133 cycles. We believe that the highly spatialized structure of the Cu/NCNF sample can provide considerable storage space for discharge products. The X-ray absorption fine structure spectroscopy further proves the existence of a Cu–N4 catalytic active center, and the uniformly dispersed Cu–N4 sites had a positive effect on the adsorption and activation of CO2 and could also promote the decomposition of discharge products as the reactive active site.