A MOF-derived carbon host associated with Fe and Co single atoms for Li-Se batteries

Lithium-selenium (Li-Se) batteries are considered a promising energy storage material due to their high electronic conductivity and volume capacity. However, the performance of Li-Se batteries is far away from commercial application, and few previous research studies achieved excellent performance of Li-Se batteries when the current density is higher than 5C (1C = 675 mA h g(-1)) to date. Recently non-noble metal single-atom catalysts have attracted extensive interest because of their low cost and maximum utilization, while introducing binuclear single atoms into Li-Se batteries is still a challenge. Herein, for the first time, a hierarchical porous carbon host with binuclear single-atom-sites FeN4 and Co2N3 with a PDA shell (APPC/Se@PDA) is prepared as the cathode for Li-Se batteries. The uniformly dispersed single-atom sites exhibit a synergistic effect by not only strengthening the binding force between C and Se species but also enhancing the transfer rate of electrons and Li+, which is demonstrated by electrochemical performance, ex situ X-ray photoelectron spectroscopy measurements and density functional theory (DFT) calculations. Moreover, the hierarchical pores and PDA shells provide physical confinement. As a result, APPC/Se@PDA exhibits a high specific capacity of 536 mA h g(-1) at 0.2C after 220 cycles at a Se loading of 4 mg cm(-2), and maintains a high reversible capacity of 645 mA h g(-1) after 700 cycles at 2C with a low capacity attenuation of 0.0079% per cycle. Even at 10C and 23C, 420 mA h g(-1) and 274 mA h g(-1) are achieved after 1500 cycles and 2500 cycles, respectively. To the best of our knowledge, such an excellent performance at high current densities of Li-Se batteries has not been reported. Combining experiments and theoretical calculations, such a novel strategy broadens the future research of Li-Se batteries and further applications of non-noble metal single atoms.

Automated summary

In this study, a hierarchical porous carbon cathode with binuclear single-atom sites FeN4 and Co2N3 with a PDA shell (APPC/Se@PDA) was prepared for Li-Se batteries, showing excellent performance at high current densities. This novel strategy broadens the future research of Li-Se batteries and further applications of non-noble metal single atoms.