Bimetallic Bi–Sn nanoparticles in-situ anchored in carbon nanofiber as flexible self-supporting anode toward advanced magnesium ion batteries

With the unprecedented rise of flexible electronic technology, it is imperative to develop the matched flexible power supply systems. Magnesium ion battery (MIB), as a promising next-generation battery system, shows significant potential as a power source for flexible electronic devices. However, the research on flexible MIB remains in its infancy, and the exploration of novel and reliable flexible electrodes is crucial. Herein, a binder-free and flexible self-supporting electrode with bimetallic Bi–Sn nanoparticles anchored in carbon nanofiber (CNF@Bi-Sn) was fabricated via electrospinning method combined with subsequent calcinations, and applied to MIBs for the first time. The CNF@Bi-Sn simultaneously integrated the advantages of hierarchical porous carbon nanofiber framework, the homodisperse nanosized Bi-Sn particles, and the increased phase/grain boundaries, which were beneficial for improving the structural stability and facilitating Mg 2+ diffusion kinetics. The CNF@Bi-Sn alloy anode demonstrated impressive performance with high initial specific capacity of 738mAh/g, exceptional rate capability and outstanding cycling stability of 150mAh/g at 40 mA g −1 after 100 cycles. Significantly, the quantitative kinetic analysis, ex-situ SEM, TEM and XRD were conducted to reveal the structural evolution during cycling and the magnesium storage mechanism based on reversible two-phase alloying/de-alloying transformation reactions. Furthermore, the full batteries were assembled, demonstrating its potential for practical applications. This protocol sheds light on exploring high-performance flexible self-supporting alloy anode for future flexible power systems.