Metal organic framework derived CoS₂@Ni(OH)₂ core-shell structure nanotube arrays for high-performance flexible hybrid supercapacitors

The rational design of hybrid structures which consist of multiple components with distinctive characteristics is an effective strategy for developing materials when energy storage applications. In this paper, a novel hierarchical CoS₂@Ni(OH)₂ core-shell nanotube array covered carbon cloth is successfully designed and synthesized for use in supercapacitors (SCs). The CoS₂ nanotube (NT) arrays are synthesized using the metal organic framework template method, and serve as the scaffold for the growth of ultrathin Ni(OH)₂ nanosheets via the electrodeposition process. The optimized CoS₂@Ni(OH)₂ hybrid electrode exhibits high specific capacity of 743 C g⁻¹ at current density of 1 A g⁻¹, which is nearly 5.9 times higher than that of a single CoS₂ electrode. In addition, a solid state hybrid supercapacitor device is fabricated with CoS₂@Ni(OH)₂ hybrid electrode as positive and activated carbon as negative. The as-prepared devices deliver high energy density (29.22 W h kg⁻¹ at 899.2 W kg⁻¹) and high power density (8.99 kW kg⁻¹ at 11.74 W h kg⁻¹), as well as good cycling stability (85.5% retention of specific capacitance after 3000 cycles). The devices also display excellent flexible properties under different bending conditions. The present work shows that electrode materials with hybrid structure have considerable application prospect for flexible energy storage and conversion.