Carbon–Sulfur Composites from Cylindrical and Gyroidal Mesoporous Carbons with Tunable Properties in Lithium–Sulfur Batteries

Abstract

Sulfur is a high-potential candidate for next generation electrical energy storage due to its abundance, low cost, and nontoxicity. The electrically insulating property of sulfur and lithium sulfide and the solubility of polysulfides in the electrolyte, however, pose great challenges for the realization of long-lasting lithium–sulfur batteries for commercial applications. In recent years, much attention has been focused on mesoporous carbon–sulfur composites as cathode material. Fundamental studies on the performance of such electrodes correlated to systematic variations of structural and porosity characteristics of the carbons remain elusive, however. In this work a variety of block copolymer (BCP) derived mesoporous carbons were studied with uniform and tunable pore sizes as sulfur hosts. Morphologies included hexagonally packed cylinders and co-continuous gyroids, with one- and three-dimensional porosity, respectively. Dependence of the cyclability of carbon–sulfur composites was tested on mesopore size, morphology, and carbonization temperatures of up to 1600 °C. Results demonstrate the significant impact of the carbon properties related to the carbonization temperature, such as heteroatom content, on the capacity retention of carbon–sulfur cathodes, while morphological parameters and mesopore sizes (between 15 and 40 nm) of carbons studied here have little influence on performance. The high-temperature-derived gyroidal mesoporous carbons (1600 °C) exhibited remarkable structural stability toward activation. This allowed for the introduction of nanopores (<4 nm) with a large pore volume of 0.8 cm3 g–1 in addition to the BCP-derived mesopores (15–40 nm), with total pore volumes over 2 cm3 g–1, surface areas over 2000 m2 g–1, and retention of the well-ordered gyroidal morphology. Highly activated, gyroidal carbon–sulfur composites showed good cyclability and rate capability with discharge capacities after 100 cycles of 831 mAh g–1 at 0.1 C and 730 mAh g–1 at 1 C.

Hierarchical Porous Carbon Cathode for Lithium–Sulfur Batteries Using Carbon Derived from Hybrid Materials Synthesized by Twin Polymerization

“…This new concept of producing layered nanostructure demonstrates promising electrochemical performances up to 60 cycles (Cycle 1: 900 mAh g sulfur −1 , cycle 60: 530 mAh g sulfur −1 ). 3D highly ordered nanostructured carbon with gyroidal morphology can offer a uniform lithium‐ion diffusion path with high surface area and conductivity, thus demonstrating stable cycle performances over 100 duty cycles . Recently, twin polymerization was shown to be efficient for fabrication of nanoporous carbon with controlled architecture .…”

A Hierarchically Porous Carbon Fabric for Highly Sensitive Electrochemical Sensors

“…[41] The conductivity of HC-PET can be adjusted by changing the carbonization conditions. [42] Conventionally, the carbonization process is usually carried out at 900 C for 60 min (HC-900-60 in short), ensuring the carbonized product maintains good conductivity. HC-900-60 samples with various F127/resol ratios all showed good conductivity with resistivity lower than 3.50 Â 10 À3 Vm in air (Figure 4a, an insert).…”

Gyroidal Porous Carbon Activated with NH3 or CO2 as Lithium−Sulfur Battery Cathodes

“…Werner et al. used a triblock terpolymer poly(isoprene)‐block‐poly(styrene)‐block‐poly(ethylene oxide) (ISO) and either phenol‐formaldehyde resin or oligomeric resorcinol‐formaldehyde to produce different gyroidal mesoporous structures by co‐assembly, followed by carbonization in argon at 900–1600 °C ,. An additional removal of a template to produce the ordered mesopores is unnecessary, because the ISO decomposes at high temperatures.…”

“…They also carried out physical activation of carbon with CO 2 to create suitable micropores that encapsulate the sulfur. This hierarchical activated carbon was used to produce a carbon/sulfur (ratio 1 : 1) hybrid electrode with a specific capacity of 830 mAh/g sulfur after 100 cycles . Choudhury et al.…”