Carbon-coated Fe₃O₄ nanospindles as solid electrolyte interface for improving graphite anodes in lithium ion batteries

Abstract: This paper reports surface modification of graphite anodes using carbon coated Fe₃O₄ nanospindles (C–Fe₃O₄ NSs) with the goal of improving graphite electrode capacity and decreasing graphite degradation and irreversible capacity. A unique novel coating method based on magnetic fields was developed for coating prefabricated graphite electrodes containing conductive additives and binder. A thin layer of synthesized C–Fe₃O₄ NSs was coated on the surface of graphite anodes to prevent direct contact of graphite’s surface and electrolyte. The results indicate that C–Fe₃O₄ coating decreases growth of solid electrolyte interface (SEI) film on the surface of graphite. The C–Fe₃O₄ coating increases the initial discharge capacity of graphite anodes from 325 to 414 mAh g⁻¹ and the initial Coulombic efficiency from 72 to 79%. Moreover, C–Fe₃O₄ coated electrodes deliver an improved reversible capacity of 240 mAh g⁻¹ and Columbic efficiency of 99% after 40 cycles, whereas these values were 148 mAh g⁻¹ and 97% for bare graphite. However, the impedance analysis indicates more resistance in case of C–Fe₃O₄ coated graphite, which is due to the low ionic conductivity of Fe₃O₄ compared to graphite. Graphic abstract: [Figure not available: see fulltext.].