Wheat Straw-Derived N-, O-, and S-Tri-doped Porous Carbon with Ultrahigh Specific Surface Area for Lithium-Sulfur Batteries.

Feng Chen,Mou Zhang,Jiangang Ren,Zhiming Song,Xinyu Luo,Bing Li,Xiangyang Zhou,Lulu Ma

doi:10.3390/ma11060989

Abstract

Recently, lithium-sulfur (Li-S) batteries have been greeted by a huge ovation owing to their very high theoretical specific capacity (1675 mAh·g−1) and theoretical energy density (2600 Wh·kg−1). However, the full commercialization of Li-S batteries is still hindered by dramatic capacity fading resulting from the notorious “shuttle effect” of polysulfides. Herein, we first describe the development of a facile, inexpensive, and high-producing strategy for the fabrication of N-, O-, and S-tri-doped porous carbon (NOSPC) via pyrolysis of natural wheat straw, followed by KOH activation. The as-obtained NOSPC shows characteristic features of a highly porous carbon frame, ultrahigh specific surface area (3101.8 m2·g−1), large pore volume (1.92 cm3·g−1), good electrical conductivity, and in situ nitrogen (1.36 at %), oxygen (7.43 at %), and sulfur (0.7 at %) tri-doping. The NOSPC is afterwards selected to fabricate the NOSPC-sulfur (NOSPC/S) composite for the Li-S batteries cathode material. The as-prepared NOSPC/S cathode delivers a large initial discharge capacity (1049.2 mAh·g−1 at 0.2 C), good cycling stability (retains a reversible capacity of 454.7 mAh·g−1 over 500 cycles at 1 C with a low capacity decay of 0.088% per cycle), and superior rate performance (619.2 mAh·g−1 at 2 C). The excellent electrochemical performance is mainly attributed to the synergistic effects of structural restriction and multidimensional chemical adsorptions for cooperatively repressing the polysulfides shuttle.

Highlights

Lithium-sulfur (Li-S) batteries have attracted a lot of fashionable attention in various technology applications, ranging from portable electronic apparatuses to electric automobiles, because of their very high theoretical specific capacity (1675 mAh·g−1 ), large nominal energy density (2600 Wh·kg−1 ), low material cost, natural abundance, and environmental benignity [1,2]
A porous carbon matrix is considered one of the most promising candidates because not merely can they markedly improve the utilization of sulfur by maintaining the electrical connection, but they can restrain the dissolution of lithium polysulfides by their abundant narrow pores and large internal surfaces [7,15]
A subsidiary product of mature wheat, has a natural multilayer structure composed of three different kinds of polymers, namely, cellulose, hemicellulose, and lignin

Summary

Introduction

Lithium-sulfur (Li-S) batteries have attracted a lot of fashionable attention in various technology applications, ranging from portable electronic apparatuses to electric automobiles, because of their very high theoretical specific capacity (1675 mAh·g−1 ), large nominal energy density (2600 Wh·kg−1 ), low material cost, natural abundance, and environmental benignity [1,2]. Intense efforts have been advanced to circumvent the hurdles outlined above, such as the fabrication of various carbon-based substrate materials [3,6,7,8,9], lithium anode modification [10], developing new electrolytes or additives [11,12], and the design of novel cell configurations [13,14] Among these procedures, a porous carbon matrix is considered one of the most promising candidates because not merely can they markedly improve the utilization of sulfur by maintaining the electrical connection, but they can restrain the dissolution of lithium polysulfides by their abundant narrow pores and large internal surfaces [7,15]. The weak physical adsorption through van der Waals’ force between the nonpolar hydrophobic carbon-based substrates and highly polar hydrophilic Li2 Sx (4 ≤ x ≤ 8) obstructs the efficient trapping of dissolved polysulfides, and leads to rapid capacity degradation in the long term [3,14,15]

Methods

Results

Conclusion