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.