Built-in electric field and selenium vacancies synergistically enhance NiSe2@Co0.85Se high-performance supercapacitors

Sluggish kinetics and poor cycling stability are two major obstacles limiting large-scale energy storage in battery-type supercapacitors. Herein, a novel strategy has been proposed to address these issues, which is to use a simple two-step electrodeposition technology to prepare the NiSe2@Co0.85Se/NF(denoted as NS@CS/NF) core-shell heterostructure, generate built-in electric field, and subsequently introduced anionic vacancies to successfully construct unique Se vacancies-rich composites (denoted as Sev-NS@CS/NF). Systematic characterisation analysis and density functional theory (DFT) calculations confirm that Se vacancies and heterogeneous interfaces can modulate electronic structure and promote fast reaction kinetics to achieve excellent supercapacitor performance, with a specific capacitance of 1530 C g−1 at 1 A g−1, and a capacity retention of 86.35% even after undergoing 10,000 charge-discharge cycles. Furthermore, a hybrid supercapacitor (HSC) was constructed using Sev-NS@CS/NF as the cathode and activated carbon (AC) as the anode, exhibiting an energy density of 80 Wh kg−1 at 812 W kg−1 and maintained impressive performance metrics. Notably, when two HSC units were connected in series, they successfully illuminated an LED diode for a duration of 15 min, showcasing the considerable potential of this HSC device for various energy storage applications.