TiO2/CNTs dual-decorated functional carbon foam as self-supporting sulfur host for boosting the adsorption and redox kinetics of polysulfides

Abstract

Electrochemical properties of lithium-sulfur batteries suffer from the shuttle effect and redox kinetics of polysulfides. In this work, a solvothermal method is employed to rationally construct a self-supporting hybrid carbon foam sulfur host by TiO₂ and CNTs dual-decoration on the basis of the nitrogen-rich melamine foam. This unique hybrid carbon foam exhibits multiple functional merits including the in situ nitrogen-doping, strong chemical adsorption of polysulfides, three-dimensional high conducting network, fast reaction kinetics, good mechanical flexibility. When used to fabricate the self-supporting sulfur cathode composites for lithium-sulfur batteries, the shuttle effect and conversion kinetics of polysulfides are effectively improved. Consequently, the high first discharge capacity of 858.0 mAh g^-1 and reversible capacity of 673.5 mAh g^-1 are delivered at 0.2 C after 200 cycles. Even at a relatively high current rate of 1.0 C, the 500 cycles long-term cycling performance can be achieved, the corresponding capacity decay per cycle is 0.05%. Besides, the gravimetric capacity (832.0 mAh g^-1) and areal capacity (7.9 mAh cm^-2) are also obtained when the sulfur loading is increased to 9.5 mg cm^-2.