Three-dimensional tree-like NiCo2Se4@ZnNi layered double hydroxide core-shell heterojunctions for supercapacitors

Abstract

Heterojunction engineering has been proven to be an effective strategy to improve the electrochemical behaviors of electrode materials for supercapacitors, considering the superiority of combining the advantages of different components and achieving a synergistic effect. In addressing this, a rational three-dimensional (3D) tree-like heterojunction of NiCo2Se4@ZnNi-layered double hydroxide (LDH) was for the first time synthesized by a hydrothermal method to break the limitations of single component. By using the interface engineering strategy, one-dimensional (1D) NiCo2Se4 nanoneedles act as the internal conductive core for the orderly deposition of two-dimensional (2D) ZnNi-LDH nanosheets, forming a special core–shell heterojunction. This design realizes the exposure of numerous active sites and the creation of abundant heterointerfaces and mesopores, which contributes to the accelerated redox reaction dynamics and efficient utilization of active materials. As expected, the NiCo2Se4@ZnNi-LDH electrode achieves a capacity of 1187.4 C/g (1.54 C cm−2) at 1 A/g and wonderful rate capability. Additionally, a hybrid supercapacitor with NiCo2Se4@ZnNi-LDH as the cathode and lotus pollen-derived porous carbon as the anode delivers an energy density of 71.9 Wh kg−1 / 0.22 Wh cm−2 at a power density of 743.1 W kg−1 / 2.30 W cm−2 and a capacity retention of 94.2 % over 20,000 cycles.