Free-standing FeCoNi/C hybrid nanowires electrode for high performance lithium ion batteries

FeCoNi/C hybrid nanowires serve as free-standing anodes for LIBs. • FeCoNi/C outperforms Fe/C and FeCoNiMn/C in LIB performance. • Diameter optimization of free-standing anodes can enhance the performance of LIB. Designing an integrated anode architecture that eliminates the need for binders and conductive agents is a promising approach to enhance both the energy density and rate capability of lithium-ion batteries (LIBs). Herein, we report the synthesis of free-standing Fe/C, FeCoNi/C and FeCoNiMn/C hybrid nanowire electrodes prepared by a facile electrospinning technique followed by a reduction treatment in Ar/H 2 atmosphere. The resulting C nanowire networks, embedded with uniformly distributed alloy nanoparticles, can be directly utilized as the anodes of LIBs. Electrochemical characterizations reveal that the FeCoNi/C-25 G electrode demonstrates superior cycling stability and rate capability compared with the Fe/C-25 G and FeCoNiMn/C-25 G counterparts, delivering a reversible capacity of 518.2 mAh/g after 100 cycles at 100 mA/g with a capacity retention of 84.5%. Furthermore, by varying the electrospinning needle gauge (19 G, 25 G and 30 G, the needle inner diameters are 0.75 mm, 0.26 mm and 0.16 mm, respectively), we optimized the nanowires diameter and found that the FeCoNi/C-30 G electrode exhibits the best performance, with a capacity of 564.4 mAh/g at 100 mA/g and 402.3 mAh/g at an ultrahigh current density of 4000 mA/g. The high performance of FeCoNi/C-30 G is attributed to the synergistic effects of the multi-component alloy system and the conductive C network. The reduced nanowire diameter also contributes to the excellent performance because it can facilitate ion/electron transport, increase active-site exposure and improve structural stability. This work offers a straightforward strategy for developing flexible, high performance binder-free anodes for next-generation LIBs.