Confining Pyrrhotite Fe7 S8 in Carbon Nanotubes Covalently Bonded onto 3D Few-Layer Graphene Boosts Potassium-Ion Storage and Full-Cell Applications

Kun Han; Fuqiang An; Qi Wan; Lidong Xing; Lei Wang; Qiang Liu; Wei Alex Wang; Yongchang Liu; Ping Li; Xuanhui Qu

doi:10.1002/smll.202006719

Confining Pyrrhotite Fe₇ S₈ in Carbon Nanotubes Covalently Bonded onto 3D Few-Layer Graphene Boosts Potassium-Ion Storage and Full-Cell Applications

Small. 2021 Mar;17(12):e2006719. doi: 10.1002/smll.202006719. Epub 2021 Mar 3.

Authors

Kun Han¹, Fuqiang An¹, Qi Wan², Lidong Xing¹, Lei Wang³, Qiang Liu¹, Wei Alex Wang⁴, Yongchang Liu¹, Ping Li¹, Xuanhui Qu¹

Affiliations

¹ Beijing Advanced Innovation Center for Materials Genome Engineering, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing, 100083, P.R. China.
² School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, 621010, P.R. China.
³ Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041, P.R. China.
⁴ Beijing Key Laboratory of Bio-inspired Energy Materials and Devices, School of Space and Environment, Beihang University, Beijing, 100191, P.R. China.

PMID: 33656247
DOI: 10.1002/smll.202006719

Abstract

The pyrrhotite Fe₇ S₈ with mixed Fe-valence possesses high theoretical capacity, high conductivity, low discharge/charge voltage plateaus, and superior redox reversibility but suffers from structural degradation upon (de)potassiation process due to severe volume variations. Herein, to conquer this issue, a novel hierarchical architecture of confining nano-Fe₇ S₈ in carbon nanotubes covalently bonded onto 3D few-layer graphene (Fe₇ S₈ @CNT@3DFG) is designed for potassium storage. Notably, CNTs could successfully grow on the surface of 3DFG via a tip-growth model under the catalytic effect of Fe₃ C. Such structure enables the hierarchical confinement of 0D nano-Fe₇ S₈ to 1D CNTs and further 1D CNTs to 3DFG, effectively buffering the volume variations, prohibiting the agglomeration of Fe₇ S₈ nanograins, and boosting the ionic/electronic transportation through the stable and conductive CNTs-grafted 3DFG framework. The as-prepared Fe₇ S₈ @CNT@3DFG electrode delivers an exceptional rate capability (502 mAh g^-1 at 50 mA g^-1 with 277 mAh g^-1 at 1000 mA g^-1 ) and an excellent long-term cyclic stability up to 1300 cycles. Besides, the in-situ XRD and ex-situ XPS/HRTEM results first elucidate the highly reversible potassium-storage mechanism of Fe₇ S₈ . Furthermore, the designed potassium full-cell employing Fe₇ S₈ @CNT@3DFG anode and potassium Prussian blue (KPB) cathode delivers a promising energy density of ≈120 Wh kg^-1 , demonstrating great application prospects.

Keywords: Fe 7S 8 anodes; carbon nanotubes; graphene; hierarchical confinement effect; potassium-ion batteries.

Abstract

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