Dispersible percolating carbon nano-electrodes for improvement of polysulfide utilization in Li-S batteries

Percolating carbon nanoparticles were added into electrolyte to improve the performance of Li-S batteries. These percolating carbon nanoparticles acted as dispersible nanosized electrodes, allowed the direct electrochemical utilization of dissolved polysulfides in electrolyte, and mitigated the polysulfide shuttle. As a result, the polysulfide utilization was improved with the virtual sulfur capacity increasing from 538 mA h g(-1) to 1270 mA h g(-1). The increment in high plateau-sloping capacity is 43% while a much more significant 158% increment is observed in low plateau region. The percolating carbon nanoparticles also improved the battery stability. (C) 2015 Elsevier Ltd. All rights reserved

Carboxymethyl cellulose binders enable high-rate capability of sulfurized polyacrylonitrile cathodes for Li-S batteries

Li-S batteries have attracted ever-increasing interest in recent years due to their high theoretical specific energy. However, the cycling and rate performance of the sulfur cathode are seriously hindered by the notorious polysulfide dissolution and its low conductivity. Sulfurized carbon materials containing covalently bonded sulfur chains have shown relatively better stability for Li-S batteries. In this study, we report the improvement of the high-rate performance of sulfurized carbon cathodes derived through vulcanization of polyacrylonitrile. We compared sodium carboxymethyl cellulose (NaCMC) with poly(vinylpyrrolidone) (PVDF) as cathode binders for the sulfurized polyacrylonitrile (SPAN) electrode. The SPAN cathode using the NaCMC binder showed a capacity of 938 mA h g (-1) after 450 cycles at 0.9C rate (1C = 1675 mA h g (1)) and a capacity of 677 mA h g (1) at 5C rate; both performances are much superior to that of the SPAN cathode using the PVDF binder. This result illustrates the feasibility of using water-soluble oxygen-containing binders to improve the C-rate performance of sulfurized carbons

Electroactive cellulose-supported graphene oxide interlayers for Li-S batteries

Electroactive graphene oxide (GO) interlayers between cathode and separator are examined in a lithium–sulfur cell. The GO interlayer is bifunctional and capable for lithium storage and polysulfide trapping depending on the specific surface properties. The corresponding electrochemical behaviors were evaluated by using galvanostatic charge–discharge, cyclic voltammetry and electrochemical impedance spectroscopy. A series of GO with different oxidation degrees were synthesized by tuning modified Hummer’s method. The results revealed that hydroxyl was formed at insufficient oxidation while epoxide appeared at strong oxidation. The residual graphitic structures in weakly oxidized GO can donate electrons to improve polysulfide utilization while the enriched oxygen functional groups can react with lithium ion giving rise to higher cathode capacity

Implementazione dei SIC marini della Regione Veneto: Ambienti di Transizione ed aree costiere.

Diatomite, a porous non-metal mineral, was used as support to prepare TiO2/diatomite composites by a modified sol–gel method. The as-prepared composites were calcined at temperatures ranging from 450 to 950 _C. The characterization tests included X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with an energy-dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption measurements. The XRD analysis indicated that the binary mixtures of anatase and rutile exist in the composites. The morphology analysis confirmed the TiO2 particles were uniformly immobilized on the surface of diatom with a strong interfacial anchoring strength, which leads to few drain of photocatalytic components during practical applications. In further XPS studies of hybrid catalyst, we found the evidence of the presence of Ti–O–Si bond and increased percentage of surface hydroxyl. In addition, the adsorption capacity and photocatalytic activity of synthesized TiO2/diatomite composites were evaluated by studying the degradation kinetics of aqueous Rhodamine B under UV-light irradiation. The photocatalytic degradation was found to follow pseudo-first order kinetics according to the Langmuir–Hinshelwood model. The preferable removal efficiency was observed in composites by 750 _C calcination, which is attributed to a relatively appropriate anatase/rutile mixing ratio of 90/10

Long-chain solid organic polysulfide cathode for high-capacity secondary lithium batteries

Organic polysulfides are linear sulfur chains (R–S–R, n ≥ 2) capped with organic moieties, and are appealing cathode materials in lithium batteries. The theoretical capacity of polysulfides essentially relies on the length of the sulfur chains; long-chain polysulfides could store more charges than short-chain polysulfides. Herein, we report the successful synthesis of a long-chain solid organic polysulfide (SOPS) by a radical coupling method and disclose its functions as high capacity cathode materials for secondary lithium batteries. The capped, long-chain polysulfide offers the fast charge transfer and thereby enabling the better performance than the pure sulfur. The SOPS cathode reaches an initial capacity of 1166 mA h g at 750 mA g, and maintains a high capacity of 674 mA h g at 3000 mA g