Ionothermal synthesis of three-dimensional hierarchical Ni3Se2 mesoporous nanosheet networks with enhanced performance for asymmetric supercapacitors

Abstract

The development of three-dimensional (3D) hierarchical mesoporous architectures comprising two-dimensional (2D) thin nanosheets to improve the electrochemical performance of asymmetric supercapacitors (ASCs) is of great significance. Herein, we report a simple ionothermal strategy that uses an ionic liquid (1-butyl-3-methylimidazolium chloride) as the solvent to synthesize a Ni₃Se₂ 3D hierarchical mesoporous nanosheet network (HMNN) in two stages: the formation a one-dimensional (1D) NiSe-nanorod framework and its subsequent transformation to the Ni₃Se₂ 3D HMNN. The as-synthesized Ni₃Se₂ 3D HMNN with a large specific surface area and a well-developed mesoporous structure can provide more active sites for redox reactions and promote electrolytic penetration and charge transfer, thereby achieving excellent electrochemical performance. The Ni₃Se₂ 3D HMNN exhibits a high specific capacitance of 801 F g⁻¹ at 3 A g⁻¹ and superior cycling stability (retaining 80.2% of its specific capacitance after 10 000 cycles at 10 A g⁻¹). Furthermore, the Ni₃Se₂ 3D HMNN-based ASC exhibits a high energy density of 38.4 W h kg⁻¹ at a power density of 794.5 W kg⁻¹ and outstanding cycling stability (retaining 71.4% of its specific capacitance after 10 000 cycles at 2 A g⁻¹). Impressively, two such ASC devices connected in series can light up an LED for ∼50 min, suggesting their great potential in high-performance ASCs.