Rational design of MoS₂-reduced graphene oxide sponges as free-standing anodes for sodium-ion batteries

Currently, the search for high capacity, low cost and free-standing electrodes for sodium-ion batteries (SIBs) is one of the major challenges in energy storage field. In this work, we rationally design MoS₂-reduced graphene oxide (MS-RGO) sponges via a simple freeze-drying of ammonium tetrathiomolybdate-graphene oxide mixed solution and a subsequent thermal treatment in N₂/H₂ atmosphere, and employ these sponges as free-standing anodes for SIBs. The MS-RGO sponges exhibit a porous conducive structure that can facilitate the charge transport and thus show an excellent electrochemical performance. The free-standing sponge electrodes display a maximal reversible specific capacity of 372.0 mAh g⁻¹ (0.49 mAh cm⁻²) at a current density of 100 mA g⁻¹ after 50 cycles. Even at a high current density of 1 A g⁻¹, a capacity of 192.2 mAh g⁻¹ (0.25 mAh cm⁻²) is maintained after 345 cycles. The results show that MS-RGO sponges are promising free-standing electrode materials for rechargeable SIBs.