Bottom-up gas phase construction of carbon coated Fe7Se8 nanosheet/carbon nanotube hybrid as ultrastable anode material for sodium-ion half/full batteries

Transition metal selenide/carbon nanotube (TMS/CNT) composites as one important category of anode material for rechargeable alkali metal ion batteries are always troubled by the high-quality combination between active matter and inert CNT matrices. Herein, a bottom-up gas phase pyrolysis strategy is introduced to avoid the tedious and time-consuming loading process of active nanostructures. With ferrocene and selenium powders as the raw materials, a carbon coated Fe7Se8 nanosheet/carbon nanotube (Fe7Se8@C/ CNT) hybrid is synthesized. The critical role of selenium in the mass growth of CNTs at low deposition temperature is demonstrated for the first time. Benefiting from the molecular-level synthesis process, the carbon coated Fe7Se8 nanosheets are uniformly anchored on CNTs, and a porous hybrid network architecture is constructed. When tested in sodium-ion batteries (SIBs), the Fe7Se8@C/CNT electrode exhibits high reversible capacity (485 mA h g-1 at 0.1 A g-1), high initial Coulombic efficiency (97.4 %), superior longterm cycling stability upon 1000 cycles and excellent rate capability (397 mA h g-1 at 10.0 A g-1). Moreover, the full cell that coupled with a Na3V2(PO4)3 cathode also retains an undiscounted long-term cycling ability and high rate performance, reflecting its great potential for practical SIBs. The detail kinetics analyses including capacitive contribution, EIS and GITT are carried out. This work provides a new avenue for developing high-performance TMS/CNT electrode materials in electrochemical energy storage applications.& COPY; 2023 Elsevier B.V. All rights reserved.