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

Abstract

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 framework. 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.