Research On The Preparation And Electrochemical Performances Of Hollow Nanospheres Composite

Sulfur as one of the most abundant elements on earth has a high theoretical specific capacity up to 1675 mAh/g, and lithium sulfur batteries have a theoretical energy density of -2600 Wh/kg. In this paper,we begin with a brief discussion of the operating principles and scientific/technical challenges faced by the development of lithium/sulfur cells. We then introduce some recent progress in exploring cathodes including sulfur-carbon composites, anodes, and electrolytes for lithium/sulfur cells.Finally, the opportunities and perspective for future research directions will be discussed.Double-shell SnO2@C hollow nanospheres were synthesized by a template method, and then the sulfur was loaded to form a cathode material of S/SnO2@C composite. In Li-S batteries, it delivered a high initial specific capacity of 1473.1 mAh/g at a current density of 200 mA/g, and the capacity retention was even up to 95.7% over 100 cycles at 3200 mA/g, i.e., a capacity fade rate of only 0.043% per cycle. These good electrochemical performances should be attributed to the SnO2@C hollow nanospheres. They can enhance the electronic conductivity by the outside carbon shell, and confine the lithium polysulfides by S-Sn-O and S-C chemical bonds to suppress the shuttle effect. Besides, the hollow nanospheres can readily accommodate the sulfur/sulfides to prevent the electrical/mechanical failure of the cathode, instead of their agglomeration on the external surface of SnO2@C.However, the conductivity of SnO2 is relatively poor, considering the problem, a novel spatial confinement strategy based on a carbon/TiO2/carbon sandwich structure is proposed to synthesize TiC nanoparticles anchored on hollow carbon nanospheres(TiC@C) through a carbothermal reduction reaction. During the synthesis process,two carbon layers not only serve as reductant to convert TiO2 into TiC nanoparticles,but also create a spatial confinement to suppress the aggregation of TiO2, resulting in the formation of well-dispersed TiC nanoparticles. This unique TiC@C structure shows an outstanding long-term cycling stability at high rates owing to the strong physical and chemical adsorption of lithium polysulfides (i.e., a high capacity of 732.6 mAh/g at 1600 mA/g) and it retains a capacity of 443.2 mAh/g after 1000 cycles, corresponding to a decay rate of only 0.0395% per cycle. Therefore, this unique TiC@C composite could be considered as an important candidate for the cathode material in Li-S batteries.