Enhanced Li-Ion Diffusion in LiFePO₄ Nanoparticle/Cyclized Polyacrylonitrile Core–Shell Composites

Improving both lithium-ion diffusion kinetics and electronic conductivity in LiFePO4 (LFP) cathodes remains a critical challenge for advancing lithium-ion battery technology. This study presents an LFP-10cPAN composite featuring an interconnected core–shell structure, fabricated via electrospinning followed by the conductive cyclization of polyacrylonitrile (cPAN). This engineered material exhibits significant improvements in both rate capability and cycling stability. The capacity retention rate of the LFP-10cPAN electrode at 20 C is 61.6% of that at 0.5 C, whereas the retention rate of the unmodified LFP electrode at 20 C is 55.1% of that at 0.5 C. The enhanced performance of the modified electrode is due to the point-to-shell contact between acetylene black (point) and the graphene-like cPAN (shell) coating on LFP nanoparticles, which facilitates high-speed electron transport and rapid Li+ equilibrium. The electrode achieves a discharge capacity retention rate of 90.1% after 500 cycles, significantly higher than that of the unmodified LFP electrode (69.5%). This improvement is due to the conductive cPAN coating forming a connected core–shell structure, which preserves the structural integrity of the LFP material and inhibits side reactions between the electrolyte and the LFP during cycling.