The larger ionic radius of Na ion (1.06Å) compared with that of Li ion (0.76Å) is a fundamental reason for the inferior diffusion kinetics of Na ion in intercalation hosts. Here we report interlayer expansion of intercalation hosts as a general strategy to facilitate the solid-state diffusion of Na ions. Based on this strategy, poly(ethylene oxide)–intercalated MoS2 composites (PEO–MoS2) were synthesized via a facile exfoliation-restacking method and tested as anode materials for Na-ion batteries (NIBs). The interlayer spacing of MoS2 was increased from 0.615nm to 1.45nm by insertion of controlled amounts of PEO. The bilayer PEO–intercalated MoS2 composite (PEO2L–MoS2) exhibits a specific capacity of 225mAhg−1 under a current density of 50mAg−1, twice as high as that of commercial MoS2 (com-MoS2), and shows improved rate performance due to enhanced Na-ion diffusivity. The improvement in the electrochemical performance demonstrates that interlayer expansion is an effective strategy for the development of high performance electrode materials for battery technologies based on the storage of large ions.