A self-templating scheme for the synthesis of NiCo2Se4 and BiSe hollow microspheres for high-energy density asymmetric supercapacitors

Abstract

Porous hollow structures of electrode materials can enlarge the surface area in contact with electrolytes, accelerating the transport of ions and electrons during redox reactions to enhance the electrochemical performance of the electrode materials. Herein, this work presents a facile method to synthesize NiCo₂Se₄ hollow microspheres (NiCo₂Se₄ HMSs) and BiSe hollow microspheres (BiSe HMSs) based on a self-template and selenide strategy. NiCo₂Se₄ HMSs deliver a high specific capacitance of 262.0 mA h g⁻¹ (1874.6 F g⁻¹) at a current density of 1 A g⁻¹ and good rate capability (74.9% capacitance retention at 20 A g⁻¹), which is superior to many Ni/Co-based electrode materials. Meanwhile, BiSe HMSs show an amazing capacitance of 360 mA h g⁻¹ (1293 F g⁻¹) at 1 A g⁻¹ and excellent rate capability (62.6% capacitance retention at 40 A g⁻¹). On account of the unique chemical composition and structural features, the assembled NiCo₂Se₄ HMSs//BiSe HMSs asymmetric supercapacitors (ASCs) exhibit high energy density (76.73 W h kg⁻¹ at 1.79 kW kg⁻¹) and good capacitance retention (93.4%) after 3000 cycles. This study suggests that these unique selenide structures have potential applications in fabricating high-performance ASCs, which is expected to be one of highly prospective energy storage devices.