Sustainable PAN–lignin/CoFe₂O₄ composite nanofibers as high-performance anode materials for lithium-ion batteries: synthesis, characterization, and electrochemical evaluation

This study presents the development of sustainable composite electrodes combining polyacrylonitrile (PAN)–lignin carbon nanofibers with cobalt ferrite (CoFe₂O₄) nanoparticles for advanced lithium-ion battery anodes. The composite materials were fabricated via centrifugal spinning followed by controlled carbonization at 800 °C under argon atmosphere. Comprehensive characterization using X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy (FTIR) confirmed the formation of amorphous carbon structures with localized graphitic ordering and well-crystallized CoFe₂O₄ spinel phase. The carbonized fibers exhibited uniform morphology (582 nm–1.09 μm diameter) with interconnected porous structures favorable for electrochemical applications. Electrochemical performance was systematically evaluated for composite electrodes containing 0%, 25%, 50%, and 75% CoFe₂O₄ loadings through galvanostatic charge–discharge testing, cyclic voltammetry, and electrochemical impedance spectroscopy. The optimal composition (25% CoFe₂O₄) demonstrated exceptional performance with an initial discharge capacity of 800 mAh g⁻¹ at 0.05 A g⁻¹, maintaining 250 mAh g⁻¹ after 6 cycles. At higher current density (0.5 A g⁻¹), this electrode delivered 400–450 mAh g⁻¹ initially and retained 100 mAh g⁻¹ after 50 cycles, significantly outperforming pure PAN–lignin electrodes (100–150 mAh g⁻¹ initial, degrading to 25 mAh g⁻¹). The superior performance stems from synergistic effects between the lignin-derived carbon matrix providing structural stability and the electrochemically active CoFe₂O₄ enhancing lithium storage capacity through conversion reactions. This work successfully demonstrates an environmentally sustainable, high-performance anode material that addresses critical limitations of conventional graphite electrodes while maintaining competitive electrochemical characteristics for practical lithium-ion battery applications.