Sulfur-Doped Reduced Graphene Oxide for Enhanced Sodium Ion Pseudocapacitance.

Yiting Wang,Zheng-Hong Huang,Mingxiang Hu,Hongwei Zhang,Feiyu Kang,Desheng Ai,Ruitao Lv

doi:10.3390/nano9050752

Abstract

Sodium-ion capacitors (NICs) are considered an important candidate for large-scale energy storage in virtue of their superior energy–power properties, as well as availability of rich Na+ reserves. To fabricate high-performance NIC electrode material, a hydrothermal method was proposed to synthesize sulfur-doped reduced graphene oxide (SG), which exhibited unique layered structures and showed excellent electrochemical properties with 116 F/g capacitance at 1 A/g as the cathode of NICs from 1.6 V to 4.2 V. At the power–energy density over 5000 W/kg, the SG demonstrated over 100 Wh/kg energy density after 3500 cycles, which indicated its efficient durability and superior power–energy properties. The addition of a sulfur source in the hydrothermal process led to the higher specific surface area and more abundant micropores of SG when compared with those of reduced graphene oxide (rGO), thus SG exhibited much better electrochemical properties than those shown by rGO. Partially substituting surface oxygen-containing groups of rGO with sulfur-containing groups also facilitated the enhanced sodium-ion storage ability of SG by introducing sufficient pseudocapacitance.

Highlights

Various clean energies have been widely explored to alleviate the environmental impact caused by combustions of fossil fuels
The strategy we proposed here may provide some new ideas for designing 2D electrode materials for NICs
After the hydrothermal treatments with TAA, the as-obtained sulfur-doped reduced graphene oxide (SG) displayed different XRD patterns with two peaks located at 23.74◦ and 42.78◦, which can be indexed to the (002) and (10) diffraction peaks of reduced graphene oxide (rGO), respectively [49]

Summary

Introduction

Various clean energies (e.g., solar energy, wind energy) have been widely explored to alleviate the environmental impact caused by combustions of fossil fuels. The consumption of lithium resources has surged upwards with the increasing need for energy storage devices on electric vehicles and portable electronics, which has led to even higher prices and a shortage of the very limited lithium reserves. The sodium-ion battery (NIB) and sodium-ion capacitor (NIC) have become favorable candidates for the next-generation large-scale energy storage devices in virtue of the similar properties of sodium and lithium, as well as the abundant Na+ resources. Metal oxides present good cycling stability, low specific capacity and poor conductivity limit their practical applications [5,6,7,8]. Two-dimensional (2D) MXenes [9] and metal organic frameworks (MOFs) [10] have been widely explored in this field, but the rate capacity is still not high enough to meet the increasing demand in practical applications

Methods

Results

Conclusion