A novel configuration compose of CoSe 2 nanocrystals and interlayer expanded graphitized carbon was designed, the interlayer distance was enlarged by Se-doping for the first time. Tested as anode for SIBs, CoSe 2 @3DSNC delivers superior rate capability and excellent cycling stability. Rational electrode structure design is of great significance for realizing superior Na + storage performance. Herein, a metal salt-induced polymer blowing-bubble approach followed by selenization procedure is developed to in-situ generate abundant sub-10 nm CoSe 2 nanocrystals on 3D Se/N co-doped carbon networks (CoSe 2 @3DSNC). The phase transition from Co to CoSe 2 and the incorporation of Se into the carbon layer are realized simultaneously to establish above configuration, in which the CoSe 2 nanocrystals are anchored on interlayer expanded carbon networks. Such unique configuration endows electrode with lower Na + diffusion energy barrier, higher Na + storage capability and better structural durability. Reflected in SIBs, the optimized CoSe 2 @3DSNC delivers superior rate capability (310 mAh g −1 at 10 A g −1 ) and excellent long-term cycling stability (409 mAh g −1 after 1200 cycles at 5 A g −1 ). Moreover, this configuration can also be obtained in other metal selenides-carbon composite through a similar approach.