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Fe3O4/Fe1–x S@C@MoS2 nanosheets consisting of Fe3O4/Fe1–x S nanoparticles embedded in carbon nanosheets and coated by MoS2 were synthesized via a facile and scalable strategy with assistance of NaCl template. With Fe3O4/Fe1–x S@C@MoS2 nanosheets composite as an anode for LIBs and SIBs, the Fe3O4/Fe1–x S@C@MoS2 nanosheets composite shows outstanding electrochemical performance because of the synergistic effects of the Fe3O4/Fe1–x S nanoparticles, carbon nanosheets and MoS2. In this unique constructed architecture, on one hand, the carbon nanosheets can avoid the direct exposure of Fe3O4/Fe1–x SNPs to the electrolyte; on the other hand, the carbon nanosheets can buffer the volume change of Fe3O4/Fe1–x S NPs as well as suppress the aggregation of Fe3O4/Fe1–x S NPs during the cycling processes. Moreover, MoS2 can offer high interfacial contact areas between active materials/electrolyte, resulting in rapid charge transfer and higher capacity. As a consequence, Fe3O4/Fe1–x S@C@MoS2 nanosheets exhibit high reversible capacity of 1142 mAhg–1 after 700 cycles at 1.0 A g–1 and 640 mA h g–1 at 5.0 A g–1for LIBs, 402 mA h g–1 after 1000 cycles at 1.0 A g–1and 355 mA h g–1 at 2.0 A g–1 for SIBs, respectively. This outstanding electrochemical performance indicated that the Fe3O4/Fe1–x S@C@MoS2 nanosheets have potential as anode for high-performance LIBs and SIBs.

CoSe 2 with high theoretical capacity has drawn massive attention as an ideal anode material for sodium-ion batteries (SIBs). However, developing a CoSe 2 anode with high energy density to satisfy the practical application remains a very intractable challenge. Here, a carbon-free and compact submicron cobblestonelike CoSe 2 anode material was designed and synthesized, which can promote tap density via eliminating the introduction of carbon species, nanostructure, and hollow construction. Benefiting from the contribution of partial pseudocapacitive contributes, CoSe 2 displays high reversible capacity, outstanding rate property, and durable cycling stability (414.6 mAh g −1 after 700 loops at 0.2 A g −1 and 416.5 mAh g −1 after 1350 loops even at 2 A g −1 ). The enhanced tap density and remarkable sodium storage capability greatly improved volumetric energy density and gravimetric energy density and, subsequently, energy density. Meanwhile, ex situ XRD and Raman measurements were utilized to further understand the sodium storage mechanism of as-prepared CoSe 2 . This work opens up a new opportunity regarding the practical application of the CoSe 2 anode with high energy density in SIBs.