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

Abstract

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.