A Generalized Synthesis Strategy for Binderless, Free-Standing Anode for Lithium/Sodium Ion Battery Comprised of Metal Selenides@Carbon Nanofibers

The craving for lighter, smaller, and longer-lasting portable devices has driven researchers to explore next-generation materials for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Metal selenides are a notable material family that exhibits desirable conductivity, stability, and cost-effectiveness. Moreover, they can provide higher theoretical capacities than that of a commercial graphite anode. Herein, we report a generalized synthesis strategy to achieve free-standing metal selenides and carbon nanofibers composites (MSe@CNFs) as anodes for LIBs and SIBs by using facile electrospinning. The composites have active nanoparticles embedded in each carbon nanofiber, and the carbon nanofibers intertwine with each other to form a 3D nanofiber network. The structure–property–performance relationship of metal selenides (MSe, M = Sn, Fe, Ni, Cu) embedded in CNFs were thoroughly investigated in the LIBs system. The one-step prepared free-standing anodes show a high specific capacity as well as good rate capability and cycle stability. The good performance is ascribed to the high electron conductivity originating from the N-doped carbon nanofiber network, fast electrolyte penetration through interfiber voids, and accommodation of volume change enabled by the carbon encapsulation of nanoparticles. Additionally, the absence of the binder, additive carbon, and current collector not only reduces the weight of the anode but also eliminates the uncontrollable structure formation from the slurry coating method. Postmortem analysis further confirms the robust structural stability of these rationally designed composites. When the application is extended to SIBs, the composites also demonstrate great potential. In short, free-standing MSe@CNFs composites show great promise for the next generation of flexible and lightweight batteries that are crucial for various emerging applications.