Material For Lithium-sulfur Batteries Research Articles

Characterization and electrochemical activities of nanostructured transition metal nitrides as cathode materials for lithium sulfur batteries

Abstract The Lithium Sulfur (Li–S) battery system is one of the most promising candidates for electric vehicle applications due to its higher energy density when compared to conventional lithium ion batteries. However, there are some challenges facing Li−S battery commercialization, such as: low active material utilization, high self-discharge rate, and high rate of capacity fade. In this work, a series of transition metal nitrides: Tungsten nitride (WN), Molybdenum Nitride (Mo2N), and Vanadium Nitride (VN) was investigated as cathode materials for lithium polysulfide conversion reactions. Capacities of 697, 569, and 264 mAh g−1 were observed for WN, Mo2N, VN, respectively, with 8 mg cm−2 loading, after 100 cycles at a 0.1 C rate. WN higher electrochemical performance may be attributed to a strong reversible reaction between nitrides and polysulfide, which retains the sulfur species on the electrode surface, and minimizes the active material and surface area loss. X-ray photoelectron spectroscopy (XPS) analysis was performed to gain a better understanding of the mechanism underlying each metal nitride redox reactions.

Sulfur Encapsulated Porous Rattle-Type Carbon Sphere as Cathode Material for Lithium Sulfur Batteries

Sulfur Encapsulated Porous Rattle-Type Carbon Sphere as Cathode Material for Lithium Sulfur Batteries

Hydrothermal Carbon Nanosphere (CNS) Based CNS/S Composite as a Cathode Material for Lithium-Sulfur Batteries

Hydrothermal Carbon Nanosphere (CNS) Based CNS/S Composite as a Cathode Material for Lithium-Sulfur Batteries

Stability of Li Metal Anode in Li-S Batteries

Because of its high energy density and promising potential to revolutionize the future electric energy storage systems, the technology of Li-S batteries has attracted significant interests in recent years. With the significant progresses made on the development of cathode materials in lithium-sulfur (Li-S) batteries, the stability of anode in Li-S batteries has become one of the more urgent challenges in order to reach the long-term stability of Li-S batteries. Lithium metal is the preferential option for the anode material in Li-S batteries because of its high specific capacity. However, lithium polysulfides formed during discharge and charge processes may migrate from cathode to anode side to react with the lithium metal, so called shuttle problem, leading to limited cycle life and poor Coulombic efficiency of Li-S batteries. A passivation layer is easily formed on the metallic Li anode surface because of the presence of polysulfides and electrolyte additives, which is supposed to corrode Li anode and result in failure of the Li-S battery. Various strategies used to minimize the corrosion of Li anode and to reduce its impedance increase have been developed, including electrolyte additives, polymer electrolytes and interlayers. Recently, concentrated electrolytes were demonstrated to offer lower solubility of polysulfides and could lead to more stable cycling stability in Li-S batteries. Concentrated electrolytes tend to reduce the solubility of lithium polysulfides due to the lack of available solvent to partially solvate the Li+ cations. Coordinating anions also affect the solubility of lithium polysulfides through interacting with the Li+ cations with different solvation strength. In this presentation, the failure mechanism and the stability of anode/electrolyte interface in Li-S batteries with highly concentrated electrolyte will be reported.

Elemental Sulfur Mediated Facile Synthesis of a Colvalent Triazine Framework for High Performance Lithium-Sulfur Batteries

Sulfur is one of the most abundant elements and more than 70 million tons of elemental sulfur is annually produced as a by-product of the hydrodesulfurization process in the petroleum refining industry. This mostly involuntary production of sulfur, however, creates a significant global supply surplus. Therefore, the development of highly functional sulfur-rich polymers that are synthesized via direct utilization of elemental sulfur can be a useful direction in recycling the abundant sulfur to high value outcomes. Rechargeable lithium–sulfur (Li-S) batteries have received significant attention in recent years as one of such opportunities owing to their high theoretical gravimetric capacity and energy density of 1,675 mAh g-1 and 2,567 Wh kg-1, respectively. However, despite almost 30 years of development, Li-S batteries are still at the research stage, because of insufficient cycle life mainly due to the fatal redox shuttling process originating from the dissolution of the intermediate lithium polysulfide species in most of operating organic electrolytes during charge/discharge process. Herein, we report, for the first time, sulfur-medidated synthesis of CTF-1 (S-CTF-1) using 1,4-dicyanobenzene and elemental sulfur without any catalysts or solvents. The formation of CTF engages in-situ vulcanization with elemental sulfur, enabling both covalent attachment of sulfur and its homogeneous distribution within the pores. S-CTF-1 was found to have a high sulfur content of 62 wt% along with a well-shaped bipyramidal morphology that has been achieved without using any external template. We have also examined electrochemical performance of S-CTF-1 as a sulfur-cathode material in Li-S batteries. S-CTF-1 exhibited robust cycling performance for 300 cycles with 85.8% capacity retention along with the highest initial Coulombic efficiency (ICE) reported to date: 94.4% at 0.05C (25 mA g-1). Our results demonstrate the promising aspect of microporous polymers as active supports for sulfur, thus it is expected to motivate further research in this area. In a broader perspective, direct utilization of elemental sulfur in the synthesis of covalent triazine frameworks can open up new high-value applications, such as advanced electrode materials for energy storage and conversion.

A polydopamine coating ultralight graphene matrix as a highly effective polysulfide absorbent for high-energy Li[sbnd]S batteries

The soft polydopmine (PDA) layer with polar functional group was coated onto the ultralight graphene sheets (HRG) using a simple approach in a mixture of ethanol and water solution. Sulfur was further dispersed onto the surface of PDA-HRG sheets by S/CS2 solution impregnation method to obtain PDA-HRG/S composite as the cathode material for lithium sulfur batteries. The resulting composites are characterized by SEM, TEM, XRD and so on. The ultralight graphene matrix could improve the conductivity of the electrode and offer a large surface for deposition of sulfur, while the coating of hydrophilic soft PDA layer can adsorb polar polysulfides on-site and accommodate the volume change of S during the discharging processes, resulting in an excellent electrochemical performance.

Sulfur-doped ordered mesoporous carbons: A stability-improving sulfur host for lithium-sulfur battery cathodes

We report on sulfur-functionalized ordered mesoporous carbons aimed for lithium-sulfur battery electrode applications with improved charge capacity retention. The carbons were obtained by a hard-template strategy using a mixture of furfuryl alcohol and furfuryl mercaptan. For the application as electrode material in lithium-sulfur batteries, the carbons were additionally loaded with sulfur following a traditional melt-diffusion approach. It was found that the sulfur interacts stronger with the sulfur-functionalized carbon matrix than with the non-functionalized material. Electrodes showed very high capacity in the second discharge-charge cycle amounting to approximately 1500, 1200 and 1400 mAh/g (sulfur) for carbon materials with no, medium and high degrees of sulfur functionalization, respectively. More importantly, the sulfur-functionalization of the carbon was found to increase the capacity retention after 50 discharge-charge cycles by 8 and 5% for the carbons with medium and high degrees of sulfur-functionalization, respectively, compared to carbon with no sulfur-functionalization. We attribute this significant improvement to the presence of covalently bound sulfur groups at the internal surface of the functionalized carbon providing efficient anchoring sites for catenation to the sulfur loaded into the pores of the carbons and provide experimental support for this in the form of results from cyclic voltammetry and X-ray photoelectron spectroscopy.

Silicon dioxide molecular sieve with mono-layer carbon deposited in the channels and carbon nanotubes on the outside for lithium–sulfur batteries

A novel sulfur host matrix prepared by the deposition of mono-layer carbon into silicon dioxide molecular sieve channels and carbon nanotubes on the molecular sieve surface is proposed as an electrode material for lithium sulfur batteries.

All Inorganic Frameworks of Tin Dioxide Shell as Cathode Material for Lithium Sulfur Batteries with Improved Cycle Performance

SnO2 shells with micromesopores are synthesized using the template sacrifice method from silica sphere templates. The pores and specific surface area are characterized with SEM, TEM, and BET absorptions. Sulfur is introduced into the SnO2 shells up to 66 wt % according to TGA results. Extra sulfur can only be located at the outer surface of SnO2, resulting in a drastically reduced specific surface area. Because of the unique structure, the S/SnO2 composites with 66 wt % sulfur content exhibit a high initial capacity of 1517 mA·h·g–1 at a current density of 0.2 C, and 1176 mA·h·g–1 at 0.5 C, and remaining capacity of 1176 and 736.6 mA·h·g–1 after 50 cycles, respectively. The performance is much better than that of pure sulfur or S/SnO2 at higher sulfur content. Better performance of S/SnO2 at 66 wt % is attributed to the micromesopores and the shell framework of SnO2, while the performance fading at higher sulfur content is owing to the coating of extra sulfur on the outer surface of SnO2 shells.

Graphene/sulfur hybrid nanosheets from a space-confined "sauna" reaction for high-performance lithium-sulfur batteries.

A space-confined "sauna" reaction system is introduced for the simultaneous reduction and functionalization of graphene oxide to unique graphene-sulfur hybrid nanosheets, in which thin layers of amorphous sulfur are tightly anchored on the graphene sheet via strong chemical bonding. Upon being used as the cathode material in lithium-sulfur batteries, the as-synthesized composite shows an excellent electrochemical performance.

Nickel fibers/sulfur composites cathode with enhanced electrochemical performance for rechargeable lithium-sulfur batteries

The commercialization of lithium sulfur batteries have so far hindered by the low electrochemical utilization and rapid capacity fading of sulfur cathode, which is induced by low electron conductivity and high dissolution of intermediate polysulfides. Recent studies have shown that the metal (Pt, Au, Ni) as electrocatalyst of lithium polysulfides and its metallic porous nanostructure can suppress the shuttle effect. In this work, we use the porous nanostructure of nickel fibers/sulfur as-designed composite cathode material for lithium sulfur batteries. The initial discharge capacity of the cathode with the added 3(%) nickel fibers was 805mAhg−1, and the remaining capacity was 440mAhg−1 after 50 cycles at 0.766mAcm−2. Even at a high current density of 1.532mAcm−2, it also kept a high discharge capacity of 310mAhg−1. Compared with pure sulfur electrodes, the electrodes containing nickel fibers showed an obviously improved cycle and rate performances, confirming that metallic porous nanostructure of nickel can not only contribute to reducing the dissolution of polysulfides into electrolytes, but also has a catalytic effect on the redox reactions during charge-discharge process.

In situ incorporation of a S, N doped carbon/sulfur composite for lithium sulfur batteries

A novel sulfur–nitrogen co-doped carbon material (SNC), which is obtained by taking polyaniline as the nitrogen-containing carbon precursor and then incorporating sulfur atomsin situas the matrix material for lithium sulfur batteries, is investigated.

Investigation into the role of silica in lithium polysulfide adsorption for lithium sulfur battery

A new type of sulfur electrodes with the ability for polysulfide adsorption was prepared by incorporating silica nanoparticles (SN) or amine functionalized silica nanoparticles (AFSN). AFSN was synthesized by a simple and cost-effective method. The functionalization and surface morphology of silica were confirmed with Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), respectively. Polysulfide adsorption studies were carried out using UV–vis spectrometer, which confirmed the excellent adsorption of polysulfides by AFSN. Interaction of polysulfides with SN or AFSN was studied using FTIR and FT-Raman spectroscopy. The effective polysulfide adsorption by SN and AFSN leads to good and stable cycle performance of lithium sulfur cells. The results show that the incorporation of SN or AFSN with sulfur is a promising method to prepare cathode material for lithium sulfur batteries.

Enhanced cycling stability of lithium sulfur batteries using sulfur-polyaniline-graphene nanoribbon composite cathodes.

A hierarchical nanocomposite material of graphene nanoribbons combined with polyaniline and sulfur using an inexpensive, simple method has been developed. The resulting composite, characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron microscopy, and X-ray diffraction analysis, has a good rate performance and excellent cycling stability. The synergistic combination of electrically conductive graphene nanoribbons, polyaniline, and sulfur produces a composite with high performance. The method developed here is practical for the large-scale development of cathode materials for lithium sulfur batteries.

Graphene/Sulfur Nanocomposite for High Performance Lithium-Sulfur Batteries

The graphene/sulfur nanocomposite has been synthesized by heating a mixture of graphene sheets and elemental sulfur. The morphology, structure and electrochemical performance of graphene/sulfur nanocomposite as cathode material for lithium-sulfur batteries were systematically investigated by field-emission scanning electron microscope, X-ray diffraction and a variety of electrochemical testing techniques. The graphene/sulfur nanocomposite cathodes display a high reversible capacity of 800-1200 mAh g-1, and stable cycling for more than 100 deep cycles at 0.1 C. The graphene sheets have good conductivity and an extremely high surface area, and provide a robust electron transport network. The graphene network also accommodates the volume change of the electrode during the Li-S electrochemical reaction.

Sulfur–nitrogen doped multi walled carbon nanotubes composite as a cathode material for lithium sulfur batteries

The performance of lithium sulfur (Li/S) battery was greatly improved by the employment of nitrogen doped carbon nanotubes (N-CNTs) based cathode. By manipulating its structure thereby creating more defects, N-CNTs presents better dispersion of sulfur particles on N-CNTs and higher electrical conductivity compared with their non-doped counterpart, which explain the reason why N-CNTs/S composite shows improved performance. The specific discharge capacity was maintained at 625 mAh g−1 and 513 mAh g−1 after 100 cycles at 0.2 C and 0.5 C, respectively, which was about 2 times as that of CNTs. This method is proved to be a promising way to develop cathode materials for lithium sulfur batteries.

Sulfur-infiltrated graphene-based layered porous carbon cathodes for high-performance lithium-sulfur batteries.

Because of advantages such as excellent electronic conductivity, high theoretical specific surface area, and good mechanical flexibility, graphene is receiving increasing attention as an additive to improve the conductivity of sulfur cathodes in lithium-sulfur (Li-S) batteries. However, graphene is not an effective substrate material to confine the polysulfides in cathodes and stable the cycling. Here, we designed and synthesized a graphene-based layered porous carbon material for the impregnation of sulfur as cathode for Li-S battery. In this composite, a thin layer of porous carbon uniformly covers both surfaces of the graphene and sulfur is highly dispersed in its pores. The high specific surface area and pore volume of the porous carbon layers not only can achieve a high sulfur loading in highly dispersed amorphous state, but also can act as polysulfide reservoirs to alleviate the shuttle effect. When used as the cathode material in Li-S batteries, with the help of the thin porous carbon layers, the as-prepared materials demonstrate a better electrochemical performance and cycle stability compared with those of graphene/sulfur composites.

Polymer-Decorated Mesoporous Carbon for Encapsulating Sulfur As Cathode Material in Lithium Sulfur Batteries

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A mesoporous carbon–sulfur composite as cathode material for high rate lithium sulfur batteries

Sulfur composite was prepared by encapsulating sulfur into CMK-3 mesoporous carbon with different heating times and then used as the cathode material for lithium sulfur batteries. Thermal treatment at 300°C plays an important role in the sulfur encapsulation process. With 20h of heating time, a portion of sulfur remained on the surface of carbon, whereas with 60h of heating time, sulfur is confined deeply in the small pores of carbon that cannot be fully exploited in the redox reaction, thus causing low capacity. The S/CMK-3 composite with thermal treatment for 40h at 300°C contained 51.3wt.% sulfur and delivered a high initial capacity of 1375mAhg−1 at 0.1C. Moreover, it showed good capacity retention of 704mAhg−1 at 0.1C and 578mAhg−1 at 2C even after 100 cycles, which proves its potential as a cathode material for high capability lithium sulfur batteries.

One step synthesis of sulfur–carbon nanosheet hybrids via a solid solvothermal reaction for lithium sulfur batteries

Sulfur–carbon nanosheet hybrids (SCNHs) are simply synthesized by a single-step solid solvothermal reaction as the cathode material for lithium sulfur (LiS) batteries. Sulfur is homogeneously embedded into the carbon nanosheet by an in situ hybridization process, which enhances the electron and ion transportation due to the higher electronic conductivity and morphology, respectively. The solid solvothermal reaction provides insight into the unique chemical-state of the sulfur content in the sulfur–carbon hybrids due to the small difference in electronegativity between sulfur and carbon contents. This characteristic effect on the production of electrolyte-dissoluble lithium sulfide in the electrochemical reaction can enhance the cycle performance of the hybrid as a cathode material in LiS batteries. The SCNHs show improved electrochemical performance of 810 mA h g−1 at 100 mA g−1 and excellent Coulombic efficiency close to 100% at a high rate.