Boron nitride wrapped N-doped carbon nanosheet as a host for advanced lithium-sulfur battery

Abstract

Sandwich structure of boron nitride (BN) nanocrystals wrapped with uniform interconnected N-doped carbon nanosheets (N-CNs) is prepared as a lithium-sulfur battery cathode material to overcome the sluggish redox reaction and severe “shuttle effect” of lithium polysulfides (LiPSs). The BN@N-CNs-2/S presents outstanding rate capacity of 528 mAh g−1 at 2 A g−1, with extended cycle life and sluggish capacity decrease rate of 0.026% per cycle at 2 A g−1 for more than 1000 cycles. Such high performance is a result of the unique sandwich structure of BN nanocrystals evenly compounded on N-CNs, which leads to uniform distribution of active sulfur species and effectively alleviates volume expansion in the cycling process. The BN@N-CNs sandwich structure possesses the key advantages of high conductivity of N-CNs, strong chemisorption and catalytic effect for LiPSs, which is demonstrated by theoretical calculations and cyclic voltammetry curves of the symmetrical cells.