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).

Nanowall network of MoS2 grown by atomic layer deposition shows single crystalline nature and epitaxial relationship with c-sapphire. The nanowall network grown directly on current collector exhibits high capacity, remarkable stability, cyclability and high rate capability over a wide range of operating currents.

We discuss here the efficient confinement of sulfur and polysulfides within a non-carbonaceous ion conducting zeolite (NaY) host wrapped inside electronically conducting polyaniline (PAni) sheaths as a low-cost, high performance cathode for rechargeable lithium-sulfur battery. The sulfur is observed to be confined within the intra crystallite and interstitial spaces of the NaY zeolite and the (PAni) sheaths prevent leakage of sulfur (and polysulfides). Additionally, this NaY-PAni assembly provides distinct pathways for electrons (through PAni) and ions (through NaY channels and across PAni sheaths) during battery operation. Raman spectroscopy confirms the presence of sulfur in diradical S 8 * chain forms in the cylindrical pores of NaY and as far our knowledge is concerned, this is the very first result demonstrating the stabilization of sulfur in its metastable state only under confinement at ambient conditions. Sulfur content as high as 75% could be loaded in the NaY-PAni assembly. However, extremely stable battery performance is obtained for slightly lower S-loadings. At sulfur content of 65%, capacity of around 600 mAh g -1 is obtained at the end of 200 cycles.[a] S.

The bulk of the work related to a Li–S rechargeable battery revolves around materials design strategies of a suitable carbon­(/noncarbon)–host matrix targeted toward the entrapment of sulfur and prevention of leaching out of polysulfides into the electrolyte. This strategy, however, limits the extent of sulfur loading and, depending on the host, may simultaneously increase the unutilizable mass of sulfur in the electrode. Recently, usage of interlayers between conventional S|C composite cathode and separator has been demonstrated in Li–S batteries. This interlayer, mostly carbon or doped carbon, has been used to trap the polysulfides in between the interlayer and S-cathode. Instead of carbon, we demonstrate here an alternative and novel interlayer of metal oxide nanoparticles between cathode and separator to efficiently trap and arrest the polysulfides at the S-cathode. Oxide-based compounds exhibit a superior ability to hold the lower order polysulfides toward the S-cathode by bonding interactions, thereby enhancing anode protection. We employ pseudocapacitive metal oxides viz. Ni­(OH)2 and NiO as the interlayers for efficient anchoring of the polysulfide. In the presence of the Ni­(OH)2/NiO nanoparticle interlayer, an alternative pathway for sulfur reduction and oxidation takes place which simultaneously leads to a phenomenal reduction in the polysulfide shuttle effect, even at extremely high loadings of sulfur (up to 15 mg cm–2). The beneficial role of the interlayers in inhibiting the shuttle effect is studied via in depth ex situ UV–vis and powder X-ray diffraction of the battery separator and the interlayer, respectively, cycled at various depths of discharge and charge. The conventional Li–S cell with S/C composite cathodes and metal oxide interlayers exhibits a remarkable improvement in both cycliability and rate capability (range: C/10–5C) vis à vis the cell without any interlayer.

A high surface area porous carbon synthesized using a sacrificial‐template assisted synthesis protocol, is demonstrated here as a host for the confinement of sulfur for use in Li−S and intermediate temperature (25‐70 °C) Na−S rechargeable batteries. The hierarchical porous pillared carbon host, comprising of an intricate network of mesopores and micropores provide a landscape of sites with varying strength of interaction with sulfur. Thus, the amount of sulfur (and associated polysulfides) inside the carbon host is predetermined by the host structural characteristics rather than by the loading protocol. The mesoporous‐microporous carbon led to sulfur content in excess of 70%. While the bulk of S (and polysulfides) are stored inside the mesopores of the carbon host, the micropore apart from sulfur storage strongly contributes towards the modulation of sulfur flux during charge‐discharge cycling. The S−C cathode exhibited remarkable cycling and rate capability with Li and also against Na at intermediate temperature (25‐70 °C). This result is a paradigm shift from the conventional Na−S electrochemistry which is known to efficiently work only at elevated temperatures, in the temperature range starting from excess of 100 °C to 300 °C.