WO3 nanolayer coated 3D-graphene/sulfur composites for high performance lithium/sulfur batteries

Abstract

The lithium–sulfur (Li–S) system is one of the most promising rechargeable battery systems for portable electronics and electrification of vehicles due to a high theoretical capacity and energy density, as well as the low cost and availability of non-toxic sulfur. Polysulfide dissolution however hinders cycling performance and is the main limitation to the stability of the Li–S system. Here, we tackle this challenge by synthesizing 3D-graphene foam from soybean oil through a thermal chemical vapor deposition (CVD) process, which is subsequently loaded with sulfur to form a 3D-graphene–sulfur composite (denoted as S@G composite). The synthesized S@G composite shows high initial discharge capacity (∼1300 mA h g⁻¹ at 0.8 A g⁻¹) and capacity retention (∼80% after 200 cycles). Furthermore, a thin layer (∼100 nm) of tungsten oxide (WO₃) on the S@G composite dramatically improves the cycling performance of the Li–S system with an initial capacity of 1425 mA h g⁻¹ and approximately 95% capacity retention after 500 cycles. The analysis and theoretical calculation results prove that the novel material and approach can enhance the electrochemical performance of rechargeable Li–S batteries and shed light on developing high-performance energy storage devices for a variety of applications.