Size Effect of Sulfur Nanoparticles in Lithium Sulfur Batteries

Here we report size-dependent specific capacities and rate performances of lithium sulfur batteries on the basis of sulfur nanoparticles (SNPs) with different sizes adhering on the surface of reduced graphene oxide (RGO). Uniform SNPs with a tunable particle size from 150 to 10 nm were synthesized via sulfur-amine chemistry based synthesis method with S loading >75% (wt%). Our results clearly demonstrate that sulfur utilization and rate performance are dramatically increased with SNPs size down, due to prominent improvement of electron mobility and enlarging of active region for electrochemical reaction at the interface of sulfur and RGO. Furthermore, SNPs with size of 4 nm were also prepared, whose sulfur utilization can reach up to 100% at the current density of 0.2 A/g. Moreover, the capacity remains at 1254 mAh/g after 200 cycles under the rate of 0.5 C. The initial capacity of 1574 mAh/g remains at 963 mAh/g after 500 cycles under the rate of 1 C rate. Here represents the highest initial capacity and the best capacity retention so far.