Covalent Fixing of MoS₂ Nanosheets with SnS Nanoparticles Anchored on g-C₃N₄/Graphene Boosting Fast Charge/Ion Transport for Sodium-Ion Hybrid Capacitors

The sluggish layered structural sodium reaction kinetics and the easy restacking property are major obstacles hindering the practical application of MoS2-based electrodes for sodium storage. Herein, covalently assembled two-phase MoS2–SnS supported by a hierarchical graphitic carbon nitride/graphene (MoS2–SnS@g-C3N4/G) composite is constructed to improve cycling cyclability and rate performances for Na storage. The multiphase MoS2–SnS@g-C3N4/G is featured with a covalent assembly strategy and an interconnected network architecture. This unique structural design can not only enhance the conductivity and facilitate fast interfacial electron transport, which is confirmed by experiments and density functional theory, but also buffer the volumetric changes of MoS2–SnS. As a result, the as-obtained MoS2–SnS@g-C3N4/G anode delivers a high reversible capacity of 834 mA h g–1 at 0.1 A g–1, a high rate capability of 452 mA h g–1 at 5 A g–1, and a long-term cycling stability (320 mA h g–1 at 2 A g–1 with 54.7% retention after 500 cycles) for the Na half-cell. Coupling with activated carbon (AC), our MoS2–SnS@g-C3N4/G||AC sodium-ion hybrid capacitor delivers high energy/power densities (193.1 W h kg–1/90 W kg–1 and 41.5 W h kg–1/18,000 W kg–1) and a stable cycle life in the potential range of 0–4.0 V.