Iron Selenide-Based Heterojunction Construction and Defect Engineering for Fast Potassium/Sodium-Ion Storage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Development of potassium ion batteries (PIBs) and sodium ion batteries (SIBs) is hindered by the lack of suitable anode materials with high capacity and long cycling stability.
• Existing anode materials often struggle with performance at high current densities, limiting their practical application.

Purpose of the Study:

• To design and synthesize a novel porous Ni-doped FeSe2/Fe3Se4 heterojunction encapsulated in Se-doped carbon (NF11S/C) as an advanced anode material.
• To investigate the electrochemical performance and cycling stability of the NF11S/C composite for PIBs and SIBs.
• To elucidate the ion storage mechanism in the developed electrode material.

Main Methods:

• Metal-organic framework (MOF) precursor selenization to create the porous Ni-doped FeSe2/Fe3Se4 heterojunction encapsulated in Se-doped carbon (NF11S/C).
• Electrochemical testing including galvanostatic cycling, rate capability tests, and long-term cycling stability assessments for PIBs and SIBs.
• Ex-situ characterization techniques such as X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy to analyze the material's structure and mechanism.

Main Results:

• The NF11S/C composite exhibited excellent rate performance and ultra-long cycling stability, delivering 177.3 mA h g-1 after 3050 cycles at 2 A g-1 for PIBs and 208.8 mA h g-1 after 2000 cycles at 8 A g-1 for SIBs.
• The porous structure, Ni-doping, and carbon encapsulation effectively enhanced active sites, facilitated ion/electron transport, and prevented nanoparticle aggregation.
• A PTCDA//NF11S/C full cell demonstrated stable cycling for 1200 cycles at 200 mA g-1 with a capacity of 103.7 mA h g-1.

Conclusions:

• The designed porous Ni-doped FeSe2/Fe3Se4 heterojunction encapsulated in Se-doped carbon is a highly promising anode material for advanced potassium and sodium ion batteries.
• The material's unique structure and composition contribute to its exceptional electrochemical performance, including high capacity, rate capability, and long-term stability.
• The findings highlight the potential of this composite for developing next-generation, high-performance rechargeable batteries.