High electrochemical sodium storage performance of ZnSe/CoSe@N-doped porous carbon synthesized by the in-situselenization of ZIF-8/67 polyhedron

Bimetallic selenide (ZnSe / CoSe) was embedded in N-doped carbon rhombic dodecahedron and used as a sodium ion battery (SIB) anode. Metal organic framework (MOF) precursors (ZIF-8 / 67) form hollow structures (denoted as ZnSe/CoSe@NPC)through in situ pyrolysis and selenization processes at specific temperatures. Our selenides have very good electrochemical sodium storage properties. After 200circulation, the capacity of the as-prepared ZnSe/CoSe@NPC nanocomposite electrode was maintained at 417.6 mAh g(-1) at 0.1 A g(-1). Regarding rate capacity, the capacities of ZnSe/CoSe@NPC nanocomposite electrode are of 460.8, 415.6, 359.9, 346.3, 318.0, 274.1 and 236.4 mAh g(-1) at different current densities of 0.1, 0.2, 0.5, 1, 2, 5 and 10 A g(-1), respectively. The stability of the ZnSe/CoSe@NPC nanocomposite electrode at high current density is also obtained, and after 900 cycles at a high current density of 1 A g(-1), the electrode can maintain a stable reversible capacity of 303.9 mAh g(-1). Besides, kinetic analysis of the electrochemical Na+ storage behaviour of the ZnSe/CoSe@NPC nanocomposite shows that the external pseudocapacitor results in excellent rate performance and excellent long-cycle stability. This study proposes a new strategy for synthesizing multi-component hollow structures for the manufacture of intended energy storage devices.