Structure-designed synthesis of yolk–shell hollow ZnFe2O4/C@N-doped carbon sub-microspheres as a competitive anode for high-performance Li-ion batteries

Abstract

Spinel ZnFe₂O₄ (ZFO) has recently gained prominence as a fascinating anode for lithium-ion batteries (LIBs) owing to its intrinsic merits. However, serious electrode pulverization and modest electrical conductivity hugely hinder its commercial application. Herein, we describe the deliberate fabrication of a multi-functional yolk–shell hollow architecture, designated as H-ZFO–C@void@C, where hollow ZFO sub-microspheres with an internal well-distributed carbon network were prepared in a template-free manner as a yolk, along with a conductive N-doped carbon nanoshell and functional void interspace. Structural/geometric simulations and experiments confirm that the well-defined internal void and hollow interior of the yolk can efficiently accommodate volumetric expansion over lithiation without breaking the outer nanoshell while ensuring good yolk–shell electronic contact and a thin yet stable solid–electrolyte-interphase film on the outer surface. The conducting nano-carbon shell and continuous internal carbon network prevent the serious aggregation of nano-ZFO subunits, and facilitate convenient charge transfer during repeated lithiation/delithiation processes. Benefiting from the synergetic contributions of these appealing design rationales, our integrated H-ZFO–C@void@C anode delivers a high initial coulombic efficiency of ∼76.8%, a remarkable reversible capacity of ∼775 mA h g⁻¹ at 2000 mA g⁻¹, and long-term cyclability after 500 cycles at a high rate of 1000 mA g⁻¹. More promisingly, our design here offers a competitive metal oxide-based anode structure for advanced LIBs.