Shaogang Wang

A Graphene–Pure‐Sulfur Sandwich Structure for Ultrafast, Long‐Life Lithium–Sulfur Batteries

Lithium-sulfur (Li–S) batteries have high specific capacities and are considered as next-generation batteries for large-scale energy storage and electric vehicles. However, rapid capacity fade and low sulfur utilisation inhibit their use. We designed a unique sandwich structure with pure sulfur between two graphene membranes, which are continuously produced over a large area, as a very simple but effective approach for the fabrication of Li–S batteries with ultrafast charge/discharge rates and long-life. One membrane was used as a graphene current collector (GCC) to replace the conventional aluminium foil current collector, and sulfur was coated onto this membrane as the active material. The other membrane was coated onto a conventional polymer separator (G-separator). This electrode showed a high specific capacity of 1340 mA h g−1 at 300 mA g−1, a Coulombic efficiency approaching 100%, excellent high-rate performance and long cyclic stability. The GCC and G-separator not only effectively reduce the internal resistance of the sulfur cathode but also function as buffer layers to trap/immobilise and reuse the dissolved lithium polysulfides. Furthermore, for the first time, three-dimensional X-ray microtomography was used to investigate sulfur diffusion during electrochemical charge/discharge.

3D Interconnected Electrode Materials with Ultrahigh Areal Sulfur Loading for Li–S Batteries

Sulfur electrodes based on a 3D integrated hollow carbon fiber foam (HCFF) are synthesized with high sulfur loadings of 6.2-21.2 mg cm(-2) . Benefiting from the high electrolyte absorbability of the HCFF and the multiple conductive channels, the obtained electrode demonstrates excellent cycling stability and a high areal capacity of 23.32 mAh cm(-2) , showing great promise in commercially viable Li-S batteries.

Mesoporous TiN microspheres as an efficient polysulfide barrier for lithium–sulfur batteries

Although lithium–sulfur batteries are expected to be the promising next generation of energy storage systems, the shuttle effect of polysulfides severely hampers their practical application. In this study, we introduce mesoporous titanium nitride microspheres to decorate the commercial separator and effectively suppress the shuttle effect. Specifically, titanium nitride improves the utilization of sulfur as an upper current collector through its strong chemical adsorption for polysulfides and high conductivity. In addition, its mesoporous spherical structure also forms a favorable physical barrier to block the diffusion of polysulfides. With this titanium nitride modified separator, the cell exhibits an excellent capacity retention ratio of 76% after 200 cycles at 0.5C. A relatively high capacity of 672 mA h g−1 is obtained even at a high current density of 3C. These results suggest that the design of separators modified with transition metal nitride-based materials is a promising approach for developing high performance lithium–sulfur batteries.