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

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 (WO ₃ ) 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.