Interlayer engineering and electronic regulation of MoSe2 nanosheets rolled hollow nanospheres for high-performance sodium-ion half/full batteries

Layered transition metal dichalcogenides are promising candidates for sodium storage but suffering from low intrinsic electronic conductivity and limited interlayer spacing for fast electron/ion transport, which restricts their high-rate capability and cycling stability. In this work, rGO@MoSe2/NAC hierarchical architectures, consisting of conductive reduced graphene oxide (rGO) supported by hollow nanospheres that are rolled from superlattices of alternatively overlapped MoSe2 and N-doped amorphous carbon (NAC) monolayers, are synthesized as a highperformance sodium storage anode. Theoretical calculations reveal the intercalation of NAC monolayer between two adjacent MoSe2 monolayers improving electronic conductivity of MoSe2 in both surface and internal bulk to fully accelerate electron transport and enhance Na+ adsorption. The interoverlapped MoSe2/NAC superlattice featuring a wide interlayer expansion (72.3 %) of MoSe2 dramatically decreases Na+ diffusion barriers for fast insertion/extraction. Moreover, the hollow nanospheres and the rGO conductive network contribute to a robust hiberarchy that can well release internal stress and buffer the volume expansion, thereby enabling outstanding structural stability. Consequently, the rGO@MoSe2/NAC anode exhibits excellent high-rate capability of 194 mAh g-1 and ultralong cyclability of 12 000 cycles with a low capacity fading rate of 0.0038 % per cycle at an ultra-high current of 50 A g-1, delivering the best high-rate cycling performance to date. Remarkably, the Na3V2(PO4)3IIrGO@MoSe2/NAC full cells also present outstanding cycling stability (600 cycles) at 10C rate, which proves the great potential in fast-charging applications.