Free-standing carbon nanotube (CNT) frameworks have been found to be highly effective in increasing sulfur loading and energy density of lithium-sulfur (Li-S) batteries. This owes to their ability to accommodate a large amount of sulfur in their interspaces. Also, this solution does require neither a binder nor a current collector. As a drawback, the application of free-standing CNT frameworks suffers from the abundance of their inherent macroporosities, as these promote the diffusion of polysulfides. In this work, we address this issue by incorporating disordered mesoporous carbon (DMC), as a polysulfide reservoir, into a CNT matrix to form CNT-DMC hybrid film. We apply facile hot-pressing to incorporate sulfur into the composite electrode. Furthermore, we determine the electrochemical performances of CNT-DMC/sulfur (S) cathode by a galvanostatic method. We find that the CNT-DMC/S cathode exhibits a high initial capacity of 1032 mAh/g at 0.25 C and a superior capacity retention of 92% after 100 cycles, compared to sulfur-impregnated CNT cathode. We attribute these enhancements to the efficient polysulfide absorption ability of DMC. This novel approach bears a high potential for the development of high-performance Li-S batteries with flexible sulfur cathodes.

The removal of heavy-metal ions from wastewater is an important objective from a public-health perspective, and chelating agents can be used to achieve this aim. Herein, we report the synthesis of mesoporous carbon as a chelating polymer host using nanoarchitectonics approach. Carboxymethylated polyethyleneimine, a chelating polymer, was incorporated into the mesopore walls of mesoporous carbon to create a polymer-mesoporous-carbon composite. Nitrogen adsorption– desorption experiments and scanning electron microscopy (SEM) were used to illustrate the structural advantages of the composite. Co2+ adsorption by the composite material was examined using cobalt nitrate solutions at pH 3. The study revealed that the Co2+-absorption data are most closely modeled by the Langmuir isotherm. The maximum adsorption capacity, calculated by linear regression, was determined to be about 40 mg-Co/g-composite at pH 3. The composite exhibited about a six-times higher adsorption capacity toward a dilute Co solution (12.5 ppm) than that of the pristine mesoporous carbon. In addition, the composite showed a substantially higher distribution coefficient (Kd = 1.54×105) compared to that (Kd = 2.05×102) of the mesoporous carbon. Overall, we expect that the mesoporous composite, with its large mesopores (~20 nm), will be in high demand for adsorption applications.

We present a new and facile design of a high-performance Li-S cell by integrating a Li 2 S-impregnated glass fiber separator together with a common sulfur cathode. We find that a considerable amount of Li 2 S is consumed amidst the first charge, and most of Li 2 S disappears at the end of the second charge. During the charge process, additional sulfur material is formed and contributes to a significant enhancement of the discharge capacity (~1400 mAh/g), compared with a control cell (~1260 mAh/g) without Li 2 S. Moreover, the Li 2 S containing cell exhibits much higher cycling stability (a 31% increase from ~840 to ~1100 mAh/g in the 100th cycle) and rate capability (a 30% increase from ~580 to ~750 mAh/g at 2 C) than the control cell. Our results indicate that adopting Li 2 S-containing separator is highly effective to improving the electrochemical performances of Li-S cells.

To obtain a high S-loading cathode for a Li–S battery, we propose a free-standing carbon nanotube (CNT)-based S cathode, which consists of two layers: a pure S deposition layer with a thickness of 20 μm, and a S-containing CNT film (S-CNT). Based on scanning electron microscopic (SEM) studies, it was observed that the S layer completely vanished when the cell with the S/S-CNT cathode was discharged to 2.1 V after cell assembly, indicating that the thick sulfur film dissolved in the form of polysulfide intermediates during discharge. The proposed S/S-CNT cathode delivered double the areal capacity with good capacity retention of 83% after 100 cycles, compared with that of the control cathode (S-CNT). Thus, we believe that our new cathode design will be useful in developing stable, high-energy Li–S batteries.

The use of carbon nanotube (CNT) films as a sulfur host is a promising approach to improve the sulfur loading and energy density of Li–S batteries. However, the inability to durably incorporate polysulfides within the cathode structure results in a limited cycle life. Herein, we propose a CNTbased sulfur cathode with carbon-coated ordered mesoporous silica (c-OMS) to overcome the cycle performance issue. Scanning electron microscopy and X-ray diffraction studies on the c-OMS prepared in this work revealed that the wall surface of OMS was evenly coated with an extremely thin carbon layer. The sulfur-CNT cathode with c-OMS retained a remarkably improved capacity (942 mAh g−1) with excellent cycling stability (91%) after 100 cycles as well as significantly high sulfur utilization in the first cycle compared with the sulfur-CNT cathode with OMS. This result may stem from the surface property of c-OMS with high chemical affinity towards electrolyte solvents.