Electrochemical performance of carbon-encapsulated Fe₃O₄ nanoparticles in lithium-ion batteries: morphology and particle size effects

Carbon-encapsulated Fe₃O₄ nanoparticles (Fe₃O₄@C) with varied microstructures were produced by controlling the relative concentrations of glucose and iron nitrate hydrate in a hydrothermal process, followed by heat treatment in Ar atmosphere. Three Fe₃O₄@C nanocomposites with different particle sizes (mean diameter 31.2, 45.1 and 55.3 nm) and Fe₃O₄ core size (26.8, 15.4 and 10.3 nm) were investigated for lithium storage performance. The Fe₃O₄@C nanoparticles with 15.4 nm Fe₃O₄ core exhibit excellent initial specific capacity (1215 mAh g⁻¹) and significantly improved cycling performance (806 mAh g⁻¹ after 100 cycles) and rate capability (573 mAh g⁻¹ at current density of 1500 mA g⁻¹), in comparison to the other Fe₃O₄@C composites. This superior performance is attributed to microstructural effects spawned from the pomegranate-like carbon coating architecture of the composite, the appropriate carbon content, and the optimized particle size of Fe₃O₄@C nanoparticles, which combined suppress the agglomeration and pulverization of Fe₃O₄ nanoparticle upon cycling and enhance the electrical conductivity of the Fe₃O₄ anode.