Sulfur Embedded in a Mesoporous Carbon Nanotube Network as a Binder-Free Electrode for High-Performance Lithium–Sulfur Batteries

Abstract

Sulfur-porous carbon nanotube (S-PCNT) composites are proposed as cathode materials for advanced lithium-sulfur (Li-S) batteries. Abundant mesopores are introduced to superaligned carbon nanotubes (SACNTs) through controlled oxidation in air to obtain porous carbon nanotubes (PCNTs). Compared to original SACNTs, improved dispersive behavior, enhanced conductivity, and higher mechanical strength are demonstrated in PCNTs. Meanwhile, high flexibility and sufficient intertube interaction are preserved in PCNTs to support binder-free and flexible electrodes. Additionally, several attractive features, including high surface area and abundant adsorption points on tubes, are introduced, which allow high sulfur loading, provide dual protection to sulfur cathode materials, and consequently alleviate the capacity fade especially during slow charge/discharge processes. When used as cathodes for Li-S batteries, a high sulfur loading of 60 wt % is achieved, with excellent reversible capacities of 866 and 526 mAh g(-1) based on the weights of sulfur and electrode, respectively, after 100 cycles at a slow charge/discharge rate of 0.1C, revealing efficient suppression of polysulfide dissolution. Even with a high sulfur loading of 70 wt %, the S-PCNT composite maintains capacities of 760 and 528 mAh g(-1) based on the weights of sulfur and electrode, respectively, after 100 cycles at 0.1C, outperforming the current state-of-the-art sulfur cathodes. Improved high-rate capability is also delivered by the S-PCNT composites, revealing their potentials as high-performance carbon-sulfur composite cathodes for Li-S batteries.

Facile synthesis of mesoporous graphene platelets with in situ nitrogen and sulfur doping for lithium–sulfur batteries

“…Extensive research has been conducted to prepare different structures of carbon materials to encapsulate sulfur, 10 including mesoporous carbon, 11 carbon nanotube, 12 carbon nanober 13 and graphene, 14 which has demonstrated the potential to improve the electrical conductivity and mitigate the dissolution of polysuldes and the shuttle effect. Among the carbon materials for Li-S batteries, graphene is a promising candidate because of its high electron mobility, good chemical stability, and super hydrophobicity at nanometer scale.…”

Multifunctionality of Carbon-based Frameworks in Lithium Sulfur Batteries

“…Carbon nanotubes (CNTs) are a type of typical onedimensional (1D) carbon material that possess conductive 1 3 characteristics and provide electron pathways for Li-S batteries with increasing performances [88][89][90][91]. CNTs can be used as conductive networks and mixed with sulfur to fabricate carbon-sulfur cathodes and aligned CNT/sulfur electrode materials with high sulfur loadings of up to 90 wt% through ball milling [92].…”

Advances in Cathode Materials for High-Performance Lithium-Sulfur Batteries

“…However, the preparation of S-CNT composite in large quantities at low cost remains a great challenge, and this disadvantageous condition partly offsets the merit of the low-price LSBs. For the same purpose, CNT network has been investigated as a conductive matrix to load sulfur by many researchers (Sun et al., 2016a, Yoo et al., 2016). For example, an encapsulated sulfur electrode was designed by Kim's group (Moon et al., 2013).…”