Topological transformation construction of a CoSe2/N-doped carbon heterojunction with a three-dimensional porous structure for high-performance sodium-ion half/full batteries

Abstract

Transition metal selenides have been widely used as anode materials for sodium-ion batteries (SIBs) because of their considerable theoretical capacity and good conductivity. Nevertheless, volume expansion is a serious problem that restricts their performance. Herein, a CoSe₂/N-doped carbon heterojunction with a 3D porous structure (CoSe₂@NC) is synthesized using a topological transformation process. The generated heterojunction structure and 3D porous structure endow CoSe₂@NC with accelerated electron/ion transfer ratio and excellent structural stability. As the anode, the CoSe₂@NC based half-cell shows superior rate properties (476.4 mA h g⁻¹ at 0.5 A g⁻¹, 372.2 mA h g⁻¹ at 10.0 A g⁻¹) and good cycling stability (354.1 mA h g⁻¹ at 5.0 A g⁻¹ after 800 cycles). Moreover, the CoSe₂@NC||NVPOF full cell, assembled by coupling with Na₃V₂(PO₄)₂O₂F (NVPOF), exhibits a high energy density (136.6 W h kg⁻¹) under a power density of 185.8 W kg⁻¹. This reflects the great potential of the use of CoSe₂@NC in the direction of energy storage.