Selenium-Doped Znse-Cose/Carbon Nanofiber Composites with Encapsulated Structure for High-Performance Electrochemical Energy Storage

Abstract

Zn-ZIF-8 offers chemical stability and porous structure, aiding ion diffusion and active site access, but its conductivity and energy density limit high-power performance. Co-ZIF-8, with higher conductivity and redox activity, boosts energy storage yet faces long-term stability issues. To overcome these, this study uses electrospinning and high-temperature selenization to create selenium-doped ZnSe-CoSe/carbon nanofiber (Se-ZCCNFs) composites with an encapsule structure. When utilized as an electrode in supercapacitors, the Se-ZCCNFs nanocomposite demonstrate high specific capacitance (823.2 F g-1 at 2 A g-1). The Se-ZCCNFs//Se-ZCCNFs device displays remarkable cycling stability (90.2% of its initial capacitance after 5000 cycles at 2 A g-1). In sodium-ion batteries, the Se-ZCCNFs anode also exhibits excellent electrochemical properties. At 100 mA g-1, the Se-ZCCNFs anode displays a remarkable specific capacity of 461.7 mAh g-1, maintaining a high level of 423.9 mAh g-1 after 200 cycles. First-principles density functional theory (DFT) calculations have shown that the exceptional electrochemical performance of the Se-ZCCNFs heterostructure is due to its distinctive electronic band configuration, an elevated Fermi level in CoSe, and substantial charge transfer occurring from CoSe to CNFs. The Se-ZCCNFs, along with its innovative production method, offers considerable potential for application in electrochemical energy storage systems.

Keywords: Electrochemical performance, CoZn-ZIF-67, Zn-ZIF-8, Co-ZIF-8, DFT calculations