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 CoSe2 nanocrystals on 3D Se/N co-doped carbon networks (CoSe2@3DSNC). The phase transition from Co to CoSe2 and the incorporation of Se into the carbon layer are realized simultaneously to establish above configuration, in which the CoSe2 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 CoSe2@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.
