A novel ternary sulfur/carbon@tin dioxide composite with polysulfides- adsorptive shell and conductive core as high-performance lithium-sulfur battery cathodes

摘要

A polysulfides-adsorptive and conductive host for sulfur (S) cathode is highly required for Li-S batteries. Herein, we present a unique ternary S/C@SnO2 composite consisting of a 3D tubular core-shell structure in which a carbon matrix as the core is coated by a porous SnO2 shell. Sulfur is coated on carbon inside the tubes. The S/C@SnO2 exhibits a good electrochemical performance including a stable capacity of 730 mAh g(-1) after cycling for 500 times at 0.1C, along with a fading rate as low as 0.07% per cycle. The capacities recover well during two rounds of rate-performance measurements, exhibiting a recovery rate exceeding 96.3%. The composite also delivers stable capacities when cycling at different charge vs. discharge rates. The polysulfides-adsorptive capability of the SnO2 shell as an efficient protection shield is demonstrated through density functional theory calculation, which confirms a high surface-energy of SnO2 towards Li2S4, Li2S6, and Li2S8. The porous carbon matrix inside the SnO2 tubes provides a good conductivity for sulfur and spaces for the volume-change of sulfur. Those features of the ternary S/C@SnO2 enable it to be a promising cathode candidate for Li-S batteries.