Shuangke Liu

A 3D nanostructure of graphene interconnected with hollow carbon spheres for high performance lithium–sulfur batteries

To better suppress the capacity decay over cycling and improve the electrical insulation of the sulfur cathode for lithium–sulfur (Li–S) batteries, we designed a novel three-dimensional nanostructure of graphene interconnected with hollow carbon spheres (3D rGO–HCS) as the sulfur host. The 3D rGO–HCS nanostructure was first prepared via a hydrothermal self-assembly method followed by carbonization and etching of the SiO2 core, then sulfur was impregnated into the nanostructure by an in situ solution deposition method to obtain the S@rGO–HCS cathode. The as-prepared cathode material delivers a high discharge capacity of ∼770 mA h g−1 at 4 C rate. More importantly, it has a high capacity retention of 93.9% after 100 cycles and demonstrates a low capacity-decay rate of 0.052% per cycle after 400 cycles at 0.5 C rate. The superior comprehensive electrochemical performance of the S@rGO–HCS cathode is ascribed to the synergic effects from the 3D graphene-network design, including fast electron and ion transportation, efficient confinement of polysulfide dissolution and shuttling and successful maintenance of structural integrity.

Graphene oxide wrapped hierarchical porous carbon–sulfur composite cathode with enhanced cycling and rate performance for lithium sulfur batteries

A graphene oxide sheet wrapped hierarchical porous carbon–sulfur (HPC–S@GO) composite was designed by a two-step method to improve the lithium sulfur battery performance. With this nanostructure design, the hierarchical porous carbon supplies an electronic transport pathway and provides a large pore volume to load the sulfur while the encapsulated graphene oxide sheet is effective in trapping sulfur and polysulfides during cycling. The obtained HPC–S@GO composite delivers prolonged cycling stability and an enhanced rate performance: the capacity fading is 0.12% per cycle over 400 cycles at 1 C (1672 mA g−1) rate, and the capacities at 0.2, 0.5, 1, 2 and 5 C rate are 1333.3, 896.9, 763.0, 669.5 and 505.6 mA h g−1, respectively.

A facile one-step hydrothermal synthesis of α-Fe2O3 nanoplates imbedded in graphene networks with high-rate lithium storage and long cycle life

In this study, we demonstrate a facile one-step hydrothermal strategy to build a nanostructure of α-Fe2O3 nanoplates imbedded in graphene networks, using water and glycerol as hydrothermal solvents. The graphene oxide was chemically reduced with Fe2+ and glycerol, and the obtained α-Fe2O3 nanoplates with a thickness of 20–30 nm and a side length of 100–300 nm are well wrapped by and in tight contact with the flexible conductive graphene networks. When used as the anode material for lithium ion batteries, the rGO/α-Fe2O3 nanoplate composite demonstrates high discharge capacities of ∼896 mA h g−1 up to 200 cycles at 5 C and ∼429 mA h g−1 up to 1000 cycles even at a 10 C rate. The excellent lithium storage performance could be attributed to the synergistic effects of the unique structures, which can provide fast electron transport and shorten the diffusion path of the Li ions as well as accommodate the volume change of the composite in the cycling.

Encapsulating sulfur into highly graphitized hollow carbon spheres as high performance cathode for lithium–sulfur batteries

Encapsulating sulfur into a highly graphitized hollow carbon sphere (GHCS) is proposed as sulfur cathode for the first time. After annealing the amorphous hollow carbon sphere (HCS) at a high temperature of 2600 °C, the obtained GHCS shows polyhedral morphology and few layers graphene characteristic with extremely low oxygen content. When used as sulfur cathode, the S@GHCS composite delivers a high discharge capacity of ∼800 mA h g−1 at 4C rate and high capacity retention of 93.7% after 240 cycles at 1C rate, demonstrating much better rate capability and cycling performance compared to those of S@HCS composite.