Ni–Co sulfide nanoboxes with tunable compositions for high-performance electrochemical pseudocapacitors

Abstract

Ni–Co sulfides are considered as promising electrode materials for electrochemical pseudocapacitors because of their rich redox chemistry and great structural flexibility with low cost. However, traditional Ni–Co sulfides still suffer from poor electrochemical performance due to relatively low electronic conductivity and structural instability. Herein, we present facile syntheses of hollow Ni–Co sulfide nanoboxes with tunable compositions, i.e., NiCo₂S₄ and Ni₂CoS₄, by using a low-temperature wet-chemical method. The resultant Ni–Co sulfides demonstrate high specific capacitances with enhanced cycling stability and rate capability. The NiCo₂S₄ electrode exhibits a capacitance of 1588 F g⁻¹ at 2 A g⁻¹ and a capacitance retention of 88.2% at 5 A g⁻¹ after 4000 cycles, while the Ni₂CoS₄ electrode exhibits a capacitance of 1200 F g⁻¹ at 2 A g⁻¹ and a capacitance retention of 90.5% at 5 A g⁻¹ after 4000 cycles. All the experimental results illustrate nanostructured Ni–Co sulfides to be promising electrode materials for high-performance supercapacitors.