Synthesis of Double-Shell SnO2@C Hollow Nanospheres as Sulfur/Sulfide Cages for Lithium-Sulfur Batteries.

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.