Sulfur Cathode Materials Research Articles

Aligned sulfur-coated carbon nanotubes with a polyethylene glycol barrier at one end for use as a high efficiency sulfur cathode

High efficient sulfur cathode materials were constructed by the incorporation of aligned sulfur-coated carbon nanotubes (CNTs) and a polyethylene glycol (PEG) barrier at one end. During the charge and discharge of lithium sulfur batteries, high Li ion storage performance can be achieved on the composite electrode, which was benefited from both the aligned CNT structure and the polymer barrier. Aligned CNT framework afforded high conductivity for electron transportation and ordered pores for lithium ion transportation. Meanwhile, the PEG barrier layer greatly suppressed the shuttle of polysulfides. Therefore, this aligned sulfur-coated CNTs with a PEG barrier showed a high initial discharge capacity of 920 and 1128mAhg−1 in lithium bis(trifluoromethanesulfonyl)imide/1,3-dioxolane/1,2-dimethoxyethane and electrolyte with LiNO3 additives, respectively. The PEG coated cathode showed high cycle stability that a low degradation with 0.38% per cycle during the 100 cycles at 0.1C was achieved in LiNO3-free electrolytes. These Li storage performance was superior to the aligned sulfur-coated CNT electrode without PEG barrier.

Metallic anodes for next generation secondary batteries

Li-air(O2) and Li-S batteries have gained much attention recently and most relevant research has aimed to improve the electrochemical performance of air(O2) or sulfur cathode materials. However, many technical problems associated with the Li metal anode have yet to be overcome. This review mainly focuses on the electrochemical behaviors and technical issues related to metallic Li anode materials as well as other metallic anode materials such as alkali (Na) and alkaline earth (Mg) metals, including Zn and Al when these metal anodes were employed for various types of secondary batteries.

Decoration of sulfur with porous metal nanostructures: an alternative strategy for improving the cyclability of sulfur cathode materials for advanced lithium–sulfur batteries

Porous Pt nanostructure decorated sulfur microparticles (Pt@S) are fabricated using sulfur as the template. The Pt@S electrode shows a higher volumetric specific capacity of 520 mA h cm(-3) and improved cyclability with only 15% capacity fading after 80 cycles at 0.1 C (167.5 mA g(-1)).

Challenges and Prospects of Lithium–Sulfur Batteries

Electrical energy storage is one of the most critical needs of 21st century society. Applications that depend on electrical energy storage include portable electronics, electric vehicles, and devices for renewable energy storage from solar and wind. Lithium-ion (Li-ion) batteries have the highest energy density among the rechargeable battery chemistries. As a result, Li-ion batteries have proven successful in the portable electronics market and will play a significant role in large-scale energy storage. Over the past two decades, Li-ion batteries based on insertion cathodes have reached a cathode capacity of ∼250 mA h g(-1) and an energy density of ∼800 W h kg(-1), which do not meet the requirement of ∼500 km between charges for all-electric vehicles. With a goal of increasing energy density, researchers are pursuing alternative cathode materials such as sulfur and O2 that can offer capacities that exceed those of conventional insertion cathodes, such as LiCoO2 and LiMn2O4, by an order of magnitude (>1500 mA h g(-1)). Sulfur, one of the most abundant elements on earth, is an electrochemically active material that can accept up to two electrons per atom at ∼2.1 V vs Li/Li(+). As a result, sulfur cathode materials have a high theoretical capacity of 1675 mA h g(-1), and lithium-sulfur (Li-S) batteries have a theoretical energy density of ∼2600 W h kg(-1). Unlike conventional insertion cathode materials, sulfur undergoes a series of compositional and structural changes during cycling, which involve soluble polysulfides and insoluble sulfides. As a result, researchers have struggled with the maintenance of a stable electrode structure, full utilization of the active material, and sufficient cycle life with good system efficiency. Although researchers have made significant progress on rechargeable Li-S batteries in the last decade, these cycle life and efficiency problems prevent their use in commercial cells. To overcome these persistent problems, researchers will need new sulfur composite cathodes with favorable properties and performance and new Li-S cell configurations. In this Account, we first focus on the development of novel composite cathode materials including sulfur-carbon and sulfur-polymer composites, describing the design principles, structure and properties, and electrochemical performances of these new materials. We then cover new cell configurations with carbon interlayers and Li/dissolved polysulfide cells, emphasizing the potential of these approaches to advance capacity retention and system efficiency. Finally, we provide a brief survey of efficient electrolytes. The Account summarizes improvements that could bring Li-S technology closer to mass commercialization.

Fabrication of conductive polymer-coated sulfur composite cathode materials based on layer-by-layer assembly for rechargeable lithium–sulfur batteries

Lithium–sulfur battery is a promising energy storage system due to its high specific energy density, low cost and environmental friendliness. Layer-by-layer (LbL) assembly technique is introduced as a simple method to fabricate polymer-coated sulfur cathode materials for rechargeable lithium–sulfur batteries. Conductive polyaniline (PANI) were assembled on the outer shell of sulfur particles to provide an electron conducting paths for the charge and discharge of lithium–sulfur battery. The low permeability of sulfur shells was obtained by assembling the enough number of polyelectrolyte bilayers. A crosslinker and heat treatment were utilized to further reduce its permeability. The assembled polymer shells can be expected to be permeable for Li+ and slowly or hardly for sulfur and polysulfide during charge and discharge process. The obtained sulfur composite cathode materials were characterized by four-point probe instrument, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectroscopy. The results demonstrated polymers have been coated on the surface of sulfur only by physical interaction and have no effect on sulfur. The conductive polymer-coated sulfur cathode also represents a well conductivity of 0.23Scm−1. Moreover, after coated by polymers, the crystal structure of sulfur still keeps its orthorhombic corresponding to cyclooctasulfur molecule (S8).

Graphene Oxide as a Sulfur Immobilizer in High Performance Lithium/Sulfur Cells

The loss of sulfur cathode material as a result of polysulfide dissolution causes significant capacity fading in rechargeable lithium/sulfur cells. Here, we use a chemical approach to immobilize sulfur and lithium polysulfides via the reactive functional groups on graphene oxide. This approach enabled us to obtain a uniform and thin (around tens of nanometers) sulfur coating on graphene oxide sheets by a simple chemical reaction-deposition strategy and a subsequent low-temperature thermal treatment process. Strong interaction between graphene oxide and sulfur or polysulfides enabled us to demonstrate lithium/sulfur cells with a high reversible capacity of 950-1400 mA h g(-1), and stable cycling for more than 50 deep cycles at 0.1C (1C = 1675 mA g(-1)).

Improvement of the electrochemical properties of sulfur cathode materials with multiwalled carbon nanotubes

In order to improve electronic conductivity and prevent dissolution of sulfur into the electrolyte,composite materials based on elemental sulfur and multiwalled carbon nanotubes(MWCNTs) with high specific surface area and strong absorbability as an inactive additive were prepared by a completely airtight step-wise heat synthesis method.X-ray diffraction,scanning electron microscopy and specific surface area measurements all indicated that elemental sulfur was distributed evenly throughout the MWCNTs.The electrochemical tests showed that the initial discharge specific capacity of an elemental sulfur positive electrode with MWCNTs was 1487.0mAh·g-1 and the utilization of electrochemically active sulfur was 88.9%.The specific capacity remained as high as 913.7mAh·g-1 after 50 cycles which showed that the electrochemical properties of the sulfur cathode with the addition of MWCNTs were remarkably improved.

Review of Sulfur-Based Cathodes for High Performance Lithium Rechargeable Batteries

The preparation, characteristics and electrochemical performances of the sulfur-based cathode materials in lithium/sulfur batteries are reviewed in this paper. The elemental sulfur cathode material is briefly introduced. The structural designs, preparation processes, reaction mechanisms, and charge/discharge properties of organic sulfide, sulfur-porous carbon and sulfur-polymer composites as cathode materials are systematically discussed and problems associated with these materials are also analyzed. In addition, the research and application of lithium sulfides as cathode materials are also outlined. Finally, the further development of sulfur-based cathode materials and the commercialization of lithium/sulfur batteries are discussed.

Preparation and enhanced electrochemical properties of nano-sulfur/poly(pyrrole-co-aniline) cathode material for lithium/sulfur batteries

Abstract Poly(pyrrole-co-aniline) (PPyA) copolymer nanofibers were prepared by chemical oxidation method with cetyltrimethyl ammonium chloride (CTAC) as template, and the nano-sulfur/poly(pyrrole-co-aniline) (S/PPyA) composite material in lithium batteries was achieved via co-heating the mixture of PPyA and sublimed sulfur at 160 °C for 24 h. The component and structure of the materials were characterized by FTIR, Raman, XRD, and SEM. PPyA with nanofiber network structure was employed as a conductive matrix, adsorbing agent and firm reaction chamber for the sulfur cathode materials. The nano-dispersed composite exhibited a specific capacity up to 1285 mAh g −1 in the initial cycle and remained 866 mAh g −1 after 40 cycles.

Electrochemical Performance of the Exfoliated Graphite Containing Sulfur Cathode Material for Lithium Sulfur Battery

Electrochemical Performance of the Exfoliated Graphite Containing Sulfur Cathode Material for Lithium Sulfur Battery