Lithium-sulfur (Li-S) batteries have attracted tremendous interest because of their high theoretical energy density and cost effectiveness. The target of Li-S battery research is to produce batteries with a high useful energy density that at least outperforms state-of-the-art lithium-ion batteries. However, due to an intrinsic gap between fundamental research and practical applications, the outstanding electrochemical results obtained in most Li-S battery studies indeed correspond to low useful energy densities and are not really suitable for practical requirements. The Li-S battery is a complex device and its useful energy density is determined by a number of design parameters, most of which are often ignored, leading to the failure to meet commercial requirements. The purpose of this review is to discuss how to pave the way for reliable Li-S batteries. First, the current research status of Li-S batteries is briefly reviewed based on statistical information obtained from literature. This includes an analysis of how the various parameters influence the useful energy density and a summary of existing problems in the current Li-S battery research. Possible solutions and some concerns regarding the construction of reliable Li-S batteries are comprehensively discussed. Finally, insights are offered on the future directions and prospects in Li-S battery field.

Although the rechargeable lithium–sulfur battery is an advanced energy storage system, its practical implementation has been impeded by many issues, in particular the shuttle effect causing rapid capacity fade and low Coulombic efficiency. Herein, we report a conductive porous vanadium nitride nanoribbon/graphene composite accommodating the catholyte as the cathode of a lithium–sulfur battery. The vanadium nitride/graphene composite provides strong anchoring for polysulfides and fast polysulfide conversion. The anchoring effect of vanadium nitride is confirmed by experimental and theoretical results. Owing to the high conductivity of vanadium nitride, the composite cathode exhibits lower polarization and faster redox reaction kinetics than a reduced graphene oxide cathode, showing good rate and cycling performances. The initial capacity reaches 1,471 mAh g−1 and the capacity after 100 cycles is 1,252 mAh g−1 at 0.2 C, a loss of only 15%, offering a potential for use in high energy lithium–sulfur batteries.

Plasmon-based photothermal therapy is one of the most intriguing applications of noble metal nanostructures. The photothermal conversion efficiency is an essential parameter in practically realizing this application. The effects of the plasmon resonance wavelength, particle volume, shell coating, and assembly on the photothermal conversion efficiencies of Au nanocrystals are systematically studied by directly measuring the temperature of Au nanocrystal solutions with a thermocouple and analyzed on the basis of energy balance. The temperature of Au nanocrystal solutions reaches the maximum at ∼75 °C when the plasmon resonance wavelength of Au nanocrystals is equal to the illumination laser wavelength. For Au nanocrystals with similar shapes, the larger the nanocrystal, the smaller the photothermal conversion efficiency becomes. The photothermal conversion can also be controlled by shell coating and assembly through the change in the plasmon resonance energy of Au nanocrystals. Moreover, coating Au nanocrystals with semiconductor materials that have band gap energies smaller than the illumination laser energy can improve the photothermal conversion efficiency owing to the presence of an additional light absorption channel.

Gold nanorods exhibit rich surface-plasmon-resonance (SPR)derived properties, which have made discrete nanorods useful for many interesting applications such as optical data storage, [1] submicrometer metallic barcodes, [2] sensing, [3] biological imaging, [4] and controlled gene delivery. [5] Future scientific and technological applications of Au nanorods require the capability to assemble into complex one-, two-, or even three-dimensional (3D) functional architectures. The assembly of Au nanorods also allows for the utilization of their collective properties that result from the coupling of the optical and electronic properties between neighboring individual nanorods. Several approaches have been developed for the assembly of Au nanorods in either end-to-end (EE) or side-by-side (SS) orientations. They include i) assembly through electrostatic interactions, hydrogen bonding, or covalent bonding, [6] ii) antibody/antigen and streptavidin/biotin biorecognitions, [7] iii) use of carbon nanotubes and silica nanofibers as templates, [8] and iv) interactions between functionalized polymers in selective solvents. [9] Au nanorods assembled by these approaches are generally difficult to disassemble. Even though significant progress has been made in the organization of nanomaterials, reversible assembly and disassembly of Au nanorods in either EE or SS orientations has remained a big challenge. So far, reversible aggregation of spherical Au nanoparticles has been demonstrated by functionalizing them with thiol-modified DNA oligomers. [10] Here, we report on a robust strategy for the reversible assembly and disassembly of Au nanorods in both EE and SS fashion. Thiol-containing bifunctional molecules are selectively bound to the end or side surface of individual Au nanorods. The bound molecules induce the assembly of Au nanorods if the pH of the nanorod solution is adjusted within an optimal range. Outside the optimal pH range, Au nanorods are disassembled. This pH-controlled assembly and disassembly is reversible and can be repeated many times. Moreover, the distances between assembled nanorods are estimated to vary from 0.080 to 1.8 nm for different assembling molecules and assembly orientations.As-prepared Au nanorods are stabilized in 0.1 M aqueous cetyltrimethylammonium bromide (CTAB) solutions with pH ¼ 3.5. Their ensemble transverse and longitudinal plasmon wavelengths are 515 and 780 nm, respectively. The ensemble extinction values at the two plasmon peaks are 1.0 and 3.7, respectively, suggesting a high yield of Au nanorods. The nanorod concentration is estimated to be %0.8 nM according to previously determined molar extinction coefficients. [11] The average length, diameter, and aspect ratio, determined from %500 nanorods on transmission electron microscopy (TEM) images, are 38 AE 4 nm, 11 AE 1 nm, and 3.6 AE 0.5 nm, respectively. The used bifunctional molecules include 3-mercaptopropionic acid (MPA), 11-mercaptoundecanoic acid (MUA), glutathione (GSH), and cysteine (CYS). Their concentrations in nanorod so...

A 3D graphene-foam-reduced-graphene-oxide hybrid nested hierarchical network is synthesized to achieve high sulfur loading and content simultaneously, which solves the "double low" issues of Li-S batteries. The obtained Li-S cathodes show a high areal capacity two times larger than that of commercial lithium-ion batteries, and a good cycling performance comparable to those at low sulfur loading.