Pressure-Induced Capillary Encapsulation Protocol for Ultrahigh Loading of Sulfur and Selenium Inside Carbon Nanotubes: Application as High Performance Cathode in Li–S/Se Rechargeable Batteries

Abstract

There has been a paradigm shift in research foci toward elemental electrodes from the conventional intercalation compound-based electrochemical storage. Replacing intercalation transition metal (oxide) compounds with elemental cathodes (e.g., sulfur, oxygen) theoretically raises the storage capacities by more than one order in magnitude. The insulating nature and complexities of the redox reaction associated with electroactive elements necessitates their housing inside an electronic conductor, which has been mainly carbon. Efficiency of the electrochemical storage using such elemental electrodes, besides depending on factors related to the electrolyte, solid-state diffusion, mainly depends on characteristics of the carbon host. We report here a novel, simple, and efficient pressure-induced capillary encapsulation protocol for the confinement of chalcogens, sulfur (S) and selenium (Se), inside carbon nanotubes (CNTs). Confinement led to lowering of the surface tension of molten S/Se, resulting in superior wetting and ultrahigh loading of the CNTs. Higher than 95% of the CNTs is loaded, and very high loading, nearly 85% of S/Se inside the CNTs, is achieved. When assembled at a very high areal loading (∼10 mg cm −2 ) in the Li−S/Se battery, the S/Se-CNT cathodes exhibited very stable cyclability and high values of specific capacity at widely varying operating current densities (0.1−10 C-rates).

C–S Bonds in Sulfur-Embedded Graphene, Carbon Nanotubes, and Flake Graphite Cathodes for Lithium–Sulfur Batteries

“…Many recent reports on sulfur-embedded carbon cathodes exhibited significant reduction of the shuttle effect for lithium sulfur batteries and hence alleviate the capacity fading dramatically. 11−16 Seeking promising sulfur substrates for lithium–sulfur battery applications, researchers have investigated mesoporous carbon, 17−20 CNTs, 21−23 graphene or graphene oxide, 24−30 mixture of CNTs 31 and graphene, 32−34 carbon fiber cloth, 35 carbon onion. 36…”

Free-Standing Selenium Impregnated Carbonized Leaf Cathodes for High-Performance Sodium-Selenium Batteries

“…Moreover, the electric conductivity of Se (10 −3 S cm −1 ) is much higher than that of S (10 −30 S cm −1 at 25 °C) [27]. The shuttle effect of polyselenides (which is similar to the polysulfides, Na 2 Se n , 3 < n < 8) can also deteriorate the cycle life of Na-Se batteries; therefore, it is a key challenge to overcome the hurdle of polyselenides shuttle [28–30]. Carbon matrixes with appropriate porosity and high electric conductivity, which are always used to load Se, have been regarded as an effective way to address the above issues in recent years [20, 21, 31, 32].…”

In‐situ Generated Ultra‐High Dispersion Sulfur 3D‐Graphene Foam for All‐Solid‐State Lithium Sulfur Batteries with High Cell‐Level Energy Density

“…Figure 2b shows the high-resolution S 2p spectrum and decomposition results, showing two components S 2p signal of 55%S-3DG foam. There are two peaks at 163.6 and 164.8 eV, correspond to the state of sulfur (S 8 ), S 2p 1/2 and S 2p 3/2 peaks, respectively [10,36] . Thermogravimetric analysis (TG) of S-3DG foams prepared with Na 2 S 3 and Na 2 S 5 were tested under the nitrogen atmosphere.…”