Porous nanofibers comprising VN nanodots and densified N-doped CNTs as redox-active interlayers for Li-S batteries

A synthesis strategy to obtain hierarchically porous N-doped carbon (P-N-C) nanofibers (NFs) comprising VN nanodots and highly densified-entangled N-doped CNTs (N-CNTs) was visualized. The unique redox-active nanostructure was applied as a multifunctional interlayer for highly stable Li-S batteries (LSBs). The P-N-C skeleton obtained via selective removal of amorphous carbon (AC) and polystyrene (PS) not only guarantees efficient electrolyte percolation but also facilitates rapid diffusion of charged species during charge-discharge processes. Moreover, the N-CNTs constituting the fiber matrix increase the overall conductivity of the frame-work. Besides, highly conductive vanadium nitride (VN) nanodots act as chemisorption sites for efficient lithium polysulfide capturing and prohibit their diffusion towards the anode through efficient catalytic conversion, thus improving the elemental S utilization. The Li-S cells utilizing P-N-C@VN/N-CNT NF as a multifunctional barrier resulted in decent rate capabilities (559 mA h g-1 at 2.0 C) and long-term cycling stabilities at low and high C-rates (432 mA h g-1 after the 400th cycle at 0.1 C and 290 mA h g-1 at the end of 600th cycle at 1.0 C). This is attributed to the combined synergistic effects of the P-N-C framework, N-CNT matrix, and polar VN nanodots.