Multi-phase Fe3O4@C@MnO heterostructure for lithium-ion batteries: synergistic effects and electrochemical mechanisms

The practical application of Fe₃O₄ in lithium-ion batteries is limited by significant volume expansion (> 200%) and severe particle aggregation during lithiation/delithiation, which together lead to rapid capacity decay due to comminution-induced loss of electrical contact and slow lithium-ion diffusion kinetics. To address these challenges, we designed a three-phase Fe₃O₄@C/MnO nanocomposite using an integrated hydrothermal precipitation strategy followed by controlled thermal treatment. The initial discharge capacity of the Fe₃O₄@C/MnO negative electrode at 50 mA g⁻¹ was 1322.90 mAh g⁻¹, which exceeded the theoretical capacity obtained through the interfacial lithium storage mechanism. What's more, after 170 cycles at 200 mA g⁻¹, the capacity can still be maintained at 1042.26 mAh g⁻¹, which is a capacity retention rate of 125.37% compared with the first cycle capacity. This excellent performance stems from the heterogeneous interfacial engineering stabilization and enhanced reaction kinetics of the active materials. The carbon matrix limited the volume change of Fe₃O₄ while maintaining the structural integrity, and the compressive stress generated by MnO nanoparticles alleviated the aggregation of Fe₃O₄. Finally, the built-in electric field generated by the charge redistribution at the interface accelerates the ion/electron transport. Thus, Fe₃O₄@C/MnO demonstrates significant potential as an anode material for lithium-ion batteries.