Design and Optimization of Iron-Based Superionic-Like Conductor Anode for High-Performance Lithium/Sodium-Ion...

Metal selenides have received extensive research attention as anode materials for batteries due to their high theoretical capacity. However, their significant volume expansion and slow ion migration rate result in poor cycling stability and suboptimal rate performance. To address these issues, the present work utilized multivalent iron ions to construct fast pathways similar to superionic conductors (Fe-SSC) and introduced corresponding selenium vacancies to enhance its performance. Based on first-principles calculations and molecular dynamics simulations, it is demonstrated that the addition of iron ions and the presence of selenium vacancies reduced the material's work function and adsorption energy, lowered migration barriers, and enhances the migration rate of Li⁺ and Na⁺. In Li-ion half batteries, this composite material exhibites reversible capacity of 1048.3 mAh g^-1 at 0.1 A g^-1 after 100 cycles and 483.6 mAh g^-1 at 5.0 A g^-1 after 1000 cycles. In Na-ion half batteries, it is 687.7 mAh g^-1 at 0.1 A g^-1 after 200 cycles and 325.9 mAh g^-1 at 5.0 A g^-1 after 1000 cycles. It is proven that materials based on Fe-SSC and selenium vacancies have great applications in both Li-ion batteries and Na-ion batteries.