Titanium-dioxide-grafted carbon paper with immobilized sulfur as a flexible free-standing cathode for superior lithium-sulfur batteries

Titanium-dioxide-grafted carbon paper (CP@TiO2) has been synthesized by pyrolysis of tetrabutyltitanate-treated filter paper, which is a simple, large-scale, and green method, while the product is a superior material for immobilising sulfur as a flexible free-standing electrode for lithium-sulfur (Li-S) batteries. The as-synthesised CP@TiO2 membrane is constructed of interlaced circuitous carbon fibers and TiO2 nanoparticles distributed on/in the void among the carbon fibers. The CP@TiO2-S membrane retains the robust and flexible structure of the CP membrane after infiltrating the sulfur, and the sulfur particles are homogeneously distributed within the CP@TiO2. As a free-standing cathode, the CP@TiO2-S membrane exhibits superior electrochemical performance than the CP-S membrane, displaying a reversible discharge capacity of 850 mAh g(-1) after 200 cycles at 0.5C and a specific capacity of 660 mAh g(-1) at 5C. The superior electrochemical performance of the CP@TiO2-S membrane is ascribed to the synergetic effect between the interlaced carbon fibers of the CP membrane, which provides electronic conduction pathways and works as mechanical support, and the TiO2 nanoparticles with relatively high surface area and pore volume, which could physically/chemically trap polysulfides. The results indicate that the CP@TiO2 membrane owns potential suitability for efficient, free-standing, and high-performance batteries. (C) 2015 Elsevier B.V. All rights reserved.