Material For Lithium-sulfur Batteries Research Articles

Manipulating the electrocatalytic activity of sulfur cathode via distinct cobalt sulfides as sulfur host materials in lithium-sulfur batteries

For the better development of lithium-sulfur (Li-S) batteries, it is necessary to fabricate sulfur hosts with cheap, rapid sulfur reaction dynamic and inhibiting the shuttling effect of lithium polysulfides (LiPSs). Herein, four hollow cubic materials with two kinds of nitrogen-doped carbon derived from Prussian blue analogues (PBA) precursor, Co9S8/MnS/NC@NC-400, CoS2/MnS/NC@NC-500, CoS1.097/MnS/NC@NC-600 and CoS1.097/MnS/NC@NC-700, are reported when the vulcanization temperatures are regulated at 400 °C, 500 °C, 600 °C and 700 °C, respectively. Among them, Co9S8/MnS/NC@NC-400, CoS2/MnS/NC@NC-500 and CoS1.097/MnS/NC@NC-600 have the similar hollow cubic structure, which can physically confine the LiPSs's shuttle, however, the Co vacancies of CoS1.097 in the CoS1.097/MnS/NC@NC-600 can promote the rearrangement of surface electrons, which is beneficial to the diffusion of Li+/e−, improving the electrochemical reaction kinetics. As for the CoS1.097/MnS/NC@NC-700 with the same substance but almost collapsed structure, the CoS1.097/MnS/NC@NC-600 can accommodate the volume expansion of sulfur conversion. In the four sulfur-host materials, the CoS1.097/MnS/NC@NC-600 not only displays the outstanding adsorption ability on LiPSs, but also presents the best electrocatalytic activity in the Li2S potentiostatic deposition experiments and active sulfur reduction/oxidation conversion reactions, greatly promoting the electrochemical performances of Li-S batteries. The S@CoS1.097/MnS/NC@NC-600 cathode can deliver 1010.2 mA h g−1 at 0.5 C and maintain 651.1 mA h g−1 after 200 cycles. In addition, the in-situ X-ray diffraction (in-situ XRD) test reveals that the sulfur conversion mechanism is the processes of the α-S8 → Li2S → β-S8 (first cycle), then β-S8 ↔ Li2S during the subsequent cycles. Based on the fundamental understanding of the design and preparation of CoxSy/MnS/NC@NC hosts with the desired adsorption and catalysis functions, the work can provide new insights and reveal the defect-engineering to develop the advanced Li-S batteries.

Two-dimensional biphenylene: a promising anchoring material for lithium-sulfur batteries

Trapping lithium polysulfides (LiPSs) on a material effectively suppresses the shuttle effect and enhances the cycling stability of Li–S batteries. For the first time, we advocate a recently synthesized two-dimensional material, biphenylene, as an anchoring material for the lithium-sulfur battery. The density functional theory calculations show that LiPSs bind with pristine biphenylene insubstantially with binding energy ranging from −0.21 eV to −1.22 eV. However, defect engineering through a single C atom vacancy significantly improves the binding strength (binding energy in the range −1.07 to −4.11 eV). The Bader analysis reveals that LiPSs and S8 clusters donate the charge (ranging from −0.05 e to −1.12 e) to the biphenylene sheet. The binding energy of LiPSs with electrolytes is smaller than those with the defective biphenylene sheet, which provides its potential as an anchoring material. Compared with other reported two-dimensional materials such as graphene, MXenes, and phosphorene, the biphenylene sheet exhibits higher binding energies with the polysulfides. Our study deepens the fundamental understanding and shows that the biphenylene sheet is an excellent anchoring material for lithium-sulfur batteries for suppressing the shuttle effect because of its superior conductivity, porosity, and strong anchoring ability.

Enhancements of surface functional groups and degree of graphitization in gamma irradiated activated carbon as an electrode material

Enhancements of oxygen-containing groups on the surface of activated carbons (ACs) and the degree of graphitization in their structures allow a potential solution for the development of the cathode materials in Lithium Sulfur Batteries (LSBs). Despite the two factors having been researched considerably, the most applicable electrochemical performances and development method of the materials have not been reached. Here the chemical properties of a commercial AC in terms of surface functional groups and degree of graphitization were successfully improved by gamma irradiation with dose and medium variations. The number of oxygen-containing groups on the AC surface and the degree of graphitization in its structure were both found to increase after gamma irradiation, depending strongly upon the irradiation dose and medium type. The best electrochemical performance of 900 mAh/g capacity given by the AC irradiated in water medium under the experimental conditions suggested a larger correlation with the number of oxygen-containing groups than that with the degree of graphitization, which was found to be maximized in air.

Recent advances on graphene-based materials as cathode materials in lithium-sulfur batteries

Representing one of the advanced energy storage devices, lithium-sulfur batteries have a wide range of possible applications. While it serves as a promising energy storage system, it should adhere to multiple important criteria before a large-scale application can be realized. The novel uses of graphene can resolve the deficiencies of lithium-sulfur batteries. Graphene is an exceptional conductive material with excellent mechanical stability and is extremely flexible. Because of its large porosity value, it enables a high sulfur loading within its matrix and effectively encapsulates polysulfide. Graphene oxide, on the other hand, often exhibits a number of functional groups capable of chemically bonding to polysulfides, resulting in good capability for polysulfide entrapping. Physical containment of sulfur by graphene materials and its chemical interactions with sulfur can be further improved by designing 3D graphene-sulfur configurations through doping of functional groups or heteroatoms. This review article offers an insight into the strategies for achieving a high sulfur loading cathode with a long cycle life and high retention potential through sulfur containment and carbon host functionalization, for which this review focuses on the functionalization of graphene. Throughout these strategies, significant performance improvements can be achieved. • LSB as one of the promising alternatives for lithium-ion battery. • Discussion on solutions for key issues affecting the performance of LSB cathode. • Overview of the scientific and technological works in graphene-based LSB cathode. • Graphene with chemical and physical irregularities is more favorable as cathode.

Insight into the Anchoring Effect of Two-Dimensional TiX2 (X = S, Se, Te) Materials for Lithium-Sulfur Batteries: A DFT Study

It is desirable to develop suitable anchoring materials to refrain the notorious shuttle phenomenon in lithium-sulfur (Li-S) batteries. Two-dimensional transition metal dichalcogenides (2D TMDs), especially TiS2, with excellent physicochemical properties have attracted much attention. Here, in this work, density functional theory (DFT) computations were performed to systematically explore the adsorption behaviors of lithium polysulfides (LiPSs) over TiX2 (X = S, Se, Te) monolayer. It is concluded that TiS2 shows the best anchoring effect owing to the strongest adsorption energy. And it’s found that the intrinsic structures of LiPSs after adsorption could be preserved by calculating the decomposition energy. Moreover, the low diffusion energy barrier of Li2S on TiS2 surface is expected to accelerate the kinetics during the charge/discharge process. Based on a series of calculations and discussion, we can theoretically demonstrate that TiS2, as an anchoring material, has advantages over TiSe2 and TiTe2 in enhancing Li-S batteries performance.

Sulfur Composite Cathode Coupled with Highly Polarized Doped BiFeO3 for High-Rate Performance of Li-S Batteries

Sulfur is a promising cathode material for lithium sulfur batteries due to its high theoretical capacity (1675 mAh/g). Sulfur cathodes mostly suffer from rapid falls of capacity resulting in poor Coulombic efficiency starting from the dissolution of intermediate polysulfides in the electrolyte during discharge cycles. To enhance the electrochemical performance, carbon nanotube as conductive material has been added in sulfur. Ferroelectric materials on the other hand, have unique property of possessing permanent internal microscopic field in the ferroelectric phases. Coupling with highly polarized ferroelectric material, such as doped BiFeO3 (Bi0.9Gd0.1Fe0.95Ni0.05O3), is a process that can be used to enhance higher rate characteristics and trapping of shuttle mechanism because ferroelectrics provide internal electric field that induces macroscopic charge separation on the surface of the cathode.We report a study on nanostructured composite of Sulfur and doped BiFeO3 in wt % of the formula SX(BGFNO)1-X (where x=0.1, 0.2, 0.3 and 0.4) and adding 10% CNT in the composites as a cathode material fabricated by ball-milling technique for lithium sulfur batteries. The characterization of the sulfur composites were carried out by techniques, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), RAMAN spectroscopy and the electrochemical studies and the results will be presented.

Plasma-engineered organic dyes as efficient polysulfide-mediating layers for high performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have attracted extensive attention as a promising energy storage technology owing to their high theoretical capacity and energy density coupled with high cost efficiency. Despite these advantages, Li-S batteries still face problems in the shuttling behavior of soluble lithium polysulfides and the electrically insulating nature of sulfur, which has motivated considerable efforts toward developing conductive nanomaterials to improve electrochemical performances. In this study, microporous N, S dual-doped carbon materials based on a basic dye compound, methylene blue, were prepared via plasma engineering and carbonization process. Experimental and theoretical investigations revealed that an introduction of the carbon coated separators, denoted as PPMB interlayers, in Li-S batteries resulted in reduced cell polarization and effectively alleviated the lithium polysulfide shuttling behavior, leading to a high specific capacity of 1,329 mAh g−1 and retained specific capacity of 669 mAh g−1 after 100 cycles at 0.3C. This work highlights the potential application of this heteroatom-doped carbon material in Li-S batteries, as well as the viability of dye compound-derived carbon materials in energy storage devices.

Machine-Learning-Enabled Tricks of the Trade for Rapid Host Material Discovery in Li-S Battery.

The shuttle effect has been a major obstacle to the development of lithium-sulfur batteries. The discovery of new host materials is essential, but lengthy and complex experimental studies are inefficient for the identification of potential host materials. We proposed a machine learning method for the rapid discovery of an AB2-type sulfur host material to suppress the shuttle effect using the 2DMatPedia database, discovering 14 new structures (PdN2, TaS2, PtN2, TaSe2, AgCl2, NbSe2, TaTe2, AgF2, NiN2, AuS2, TmI2, NbTe2, NiBi2, and AuBr2) from 1320 AB2-type compounds. These structures have strong adsorptions of greater than 1.0 eV for lithium polysulfides and appreciable electron-transportation capability, which can serve as the most promising AB2-type host materials in lithium-sulfur batteries. On the basis of a small data set, we successfully predicted Li2S6 adsorption at arbitrary sites on substrate materials using transfer learning, with a considerably low mean absolute error (below 0.05 eV). The proposed data-driven method, as accurate as density functional theory calculations, significantly shortens the research cycle of screening AB2-type sulfur host materials by approximately 8 years. This method provides high-precision and expeditious solutions for other high-throughput calculations and material screenings based on adsorption energy predictions.

Decoration of carbon nanofibers with bimetal sulfides as interlayer for high performance lithium-sulfur battery

In order to obtain high-performance lithium-sulfur (Li-S) batteries, the rapid capacity loss caused by the notorious polysulfide shuttle effect is an urgent challenge to be solved. It is widely reported that polysulfides are trapped in electrolytes due to the strong chemisorption of polar materials in Li-S batteries. Here, a free-standing NiCo2S4 nanoparticles decorated carbon nanofibers (NiCo2S4-CNFs) interlayer is prepared via electrospinning and simple hydrothermal method for the application in Li-S batteries. Three-dimensional carbon fibers (CNFs) skeleton builds a highly conductive carbon network, which provides a large quantities of transmission paths for electrons and ions. Uniformly distributed NiCo2S4 nanoparticles act as an absorbent of the long-chain lithium polysulfides (LiPSs) and a catalyst to accelerate the conversion of sulfur species. Meticulous designed NiCo2S4-CNFs interlayer significantly improves the capacity retention rate and cycle stability of Li-S batteries. It supplies an initial specific capacity of 1421 mAh g−1 at 0.1 C, and its capacity remains at 918 mAh g−1 after 200 cycles at 0.2 C. Even at a high current density of 1 C, it still possesses a reversible specific capacity of 515 mAh g−1 after 500 cycles and extremely low capacity decay of 0.06% per cycle. More importantly, the NiCo2S4-CNFs interlayer still delivers excellent electrochemical performance with a higher sulfur loading of 4.5 mg cm−2, which verifies its huge commercial application potential.

Lithium sulfur battery cathode materials based on COFs ordering

In recent years, lithium-sulfur batteries and fuel cells, as a kind of new energy which is expected to replace traditional fossil fuels, have attracted people’s attention. At present, the “shuttle effect” of lithium-sulfur batteries is one of the key factors limiting the performance and application of lithium-sulfur batteries. It is urgent to find a suitable positive electrode composite material to suppress the “shuttle effect”. Covalent organic compounds (COFs) have been considered as ideal potential cathode composites for the anchors of sulfur and lithium compounds because of their regularized structure and polar functional groups. This paper mainly discusses the structure order of COF material, and gives the synthesis method of this kind of porous polymer material. The method of COFs synthesis is to design and assemble 2-D and 3-D COFs materials with different topological structures by choosing different geometrically constructed monomers and linking methods. Lithium-sulfur battery is a kind of battery with high energy density and theoretical capacity. The key to solve the shuttle effect is to find a suitable cathode composite material. Based on the order of COFs material structure, the feasibility and advantages of COFs as cathode material for lithium sulfur batteries were proposed.

Exploring the anchoring effect and catalytic mechanism of 3d transition metal phthalocyanine for S8/LiPSs: A density functional theory study

The strong anchoring effects for lithium polysulfides (LiPSs), as well as fast redox kinetics, are of great significance and necessity for the commercial development of lithium-sulfur batteries (LSBs). Metal phthalocyanines (MPc), with special M-N4 moieties, are a class of macrocyclic compounds that have the potential to be employed as sulfur host materials in LSBs. Herein, a series of 3d transition metal phthalocyanines (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) were systematically investigated for the anchoring effects and catalytic conversion activities for S8/LiPSs. The binding energy analysis demonstrates that most of MPc (except NiPc and CuPc) have stronger binding strength for S8/LiPSs than metal-free phthalocyanine (H2Pc), mainly due to the strong interaction between transition metals and S atoms. Meanwhile, the formation of the M–S bond shows a weakening effect on the Li–S bonds of Li2S then boosts the decomposition of Li2S, and MPc also possesses a relatively lower lithium diffusion barrier than H2Pc. Moreover, MPc can also accelerate the multi-step conversions from S8 to Li2S by reducing the free energy of the rate-limiting reaction (Li2S2 to Li2S) in sulfur reduction reactions (SRR). Among these MPc, TiPc has the best performance in anchoring LiPSs, accelerating the decomposition of Li2S, and promoting SRR.

Defective TiO2-graphene heterostructures enabling in-situ electrocatalyst evolution for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered as one of the promising next-generation energy storage systems because of their high energy density. While the low utilization of sulfur and sluggish reaction kinetics would lead to degradation of electrochemical performance and thus hinder the practical application of Li-S batteries. Herein, a double-shelled TiO2-graphene heterostructure (H-TiO2/rGO) with abundant oxygen vacancies (OVs) and highly exposed active plane as advanced host material in Li-S batteries is designed. This rational structure not only provides sufficient active sites and lower bandgap for lithium polysulfides (LiPSs), but also builds smooth adsorption-diffusion-conversion of LiPSs on catalyst, which greatly reduces interfacial energy barrier and promotes the utilization of sulfur through suppressing the devastating shuttling effect. Combining the synergetic merits of strong anchoring ability and catalyzing the of LiPSs, the electrode (S-TiO2/rGO-1) exhibits superior rate performance and long lifespan (1000 cycles at 1C, 0.023% capacity loss per cycle) with high columbic efficiency. This work paves an alternative way to establish smooth adsorption-diffusion-conversion of polysulfides on catalyst in Li-S batteries and provides a new sight to understand catalyst design in energy storage devices.

S, N-codoped carbon capsules with microsized entrance: Highly stable S reservoir for Li-S batteries

Nanostructured carbon materials are extensively applied as host materials to improve the utilization rate and reversibility of elemental sulfur in lithium sulfur (Li-S) batteries. Here, S, N-codoped carbon capsules (SNCCs) with microporous walls, prepared by a self-assembly process, are used as the sulfur host material in Li-S batteries. The SNCCs provide plenty of micron-sized cavities to accommodate a high S loading, which are sealed by thick walls with microsized entrance to efficently suppress the shuttle effect of lithium polysulfides. As the cathode in Li-S battery, the SNCCs/sulfur composite with a sulfur mass loading of 70 wt% exhibits a high average reversible capacity of 1220 and 1116 mA h g−1 at 0.5C and 1C, respectively, superior rate performance (905 and 605 mAh g−1 at 5C and 10C, respectively) and excellent cycling stability (capacity fading rate of 0.03% per cycle in 500 cycles). Even at a high sulfur areal loading of 7.3 mg/cm2, the SNCCs/0.7S electrode still deliver a high initial discharge capacity of 838 mAh g−1 and keeps at 730 mAh g−1 after 100 cycles, corresponding to an extraordinary capacity retention of 87.1%, showing an excellent cyclic stability. The outstanding electrochemical performance is associated with the unique capsule structure with abundant volume, microsized entrance and high conductivity. Our results provides a new strategy to prepare highly stable sulfur-carbon composites for the application in Li-S batteries.

NiCo2S4/S Composites Used as Cathode Materials in Lithium-Sulfur Batteries with High Performance

Application of lithium-sulfur battery has been limited due to polysulfide dissolution, the insulating nature of sulfur and the volumetric strain produced during charge and discharge process. To improve the performance of Li-S batteries, two kinds of bimetallic sulfides of NiCo2S4 with flaky (F-NiCo2S4) and sea urchin-like (S-NiCo2S4) structures were synthesized by using simple hydrothermal method, which were used as sulfur carriers in lithium-sulfur batteries and showed excellent electrochemical properties. At 0.2[Formula: see text]C, both electrodes of F-NiCo2S4/S and S-NiCo2S4/S have high pristine discharge specific capacities of 986[Formula: see text]mAh[Formula: see text]g[Formula: see text] and 959[Formula: see text]mAh[Formula: see text]g[Formula: see text]. At high current density of 4[Formula: see text]C, the F-NiCo2S4/S electrode still has a high pristine discharge specific capacity of 673[Formula: see text]mAh[Formula: see text]g[Formula: see text] and a coulombic efficiency of 97.00%. The specific capacity can remain at 526[Formula: see text]mAh[Formula: see text]g[Formula: see text] with a low average attenuation of 0.17% even after 130 cycles. The excellent electrochemical performances of the cathode material can be ascribed to the synergistic effect of tubular morphology, good electrical conductivity and strong adsorption ability of NiCo2S4 matrix for polysulfide. The job provides a new scheme and material for application of lithium-sulfur batteries with high performance.

Metal–Organic Aerogel Assisted Reduced Graphene Oxide Coated Sulfur as a Cathode Material for Lithium Sulfur Batteries

As a sort of cathode material with appreciable theoretical capacity, sulfur has received a lot of attention for lithium–sulfur batteries. There is extensive research focused on cathode materials. H...

A new insight into capacity fading of sulfurized polyacrylonitrile composite in carbonate electrolyte

Sulfurized polyacrylonitrile (S/PAN) composite shows great potential as a cathode material for lithium sulfur batteries, due to its advantages in cycle performance and carbonate electrolyte compatibility. However, the cell using S/PAN composite as a cathode material exhibits sluggish reaction kinetics due to the low conductivity. Moreover, capacity fading is also found in long-term cycle test and the mechanism is not well studied in previous reports. In this work, a compact composite, S/PAN confined in macro-porous carbon (MaPC), is firstly prepared by using a sulfur copolymer to improve the cycle stability. The cathode shows stable cycle stability during the initial 150 cycles at the current density of 1050 mA gsulfur−1 and the capacity maintained at 806 mAh gsulfur−1. The cycle stability is getting worse during the long-term cycle test. It is found that the capacity fading is highly related to the increasing resistance and the formation of sulfates or sulfate-like components during the repeated cycling process.

MOFs Reinforce CNTs Sponge Derived Functional Carbon Network As Sulfur Host for Lithium Sulfur Battery

Lithium sulfur battery is one of the most prospective alternatives for lithium ion battery. It possesses high theoretical capacity of 1672 mAh/g and high theoretical gravimetric energy density of a Li-S cell is approximately 2,510 Wh/kg, which is about eight folds compare to transition metal oxide [1]. The mechanism of lithium sulfur battery is based on the conversion reaction of sulfur to lithium sulfide (Li2S) which create high capacity. The transfer of two electrons per sulfur atom is more preferred than one or less than one electron per transition-metal ion [2]. However, tremendous challenges such as natural insulator characteristic of sulfur and lithium sulfide, dissolution of mediators into electrolyte, significant volume change during cycling and lithium metal anode corrosion have hindered the commercialization in industry [3].To overcome these drawbacks, the design of the sulfur cathode material plays an important role in boosting sulfur electrochemistry and accelerating the battery performance. In the past few years, metal–organic frameworks (MOFs) which consist of metal ions and organic moiety as linker have been used as novel sulfur host materials in lithium sulfur batteries [4]. Particularly, MOFs are prospective as both a precursor and derived materials. The porous carbon materials created from MOFs shows a uniform porosity due to its highly ordered crystalline structures [5]. Besides the confining sulfur within the porous carbon materials, the functional materials have been recently employed to supply both a strong interaction surface with lithium polysulfides and to provide electron transport for enhancing the redox reaction [6]. Moreover, the polysulfide shuttle effect could be manipulated by electrocatalysis [7]. Recent researches found that the atomic cobalt dopants can serve as active sites to improve the kinetics of the sulfur redox reactions. It is therefore pivotal to design an effective electrode that not only improve the electrochemical processes of sulfur but also could efficiently suppress the intermediate polysulfide shuttle effect [8].In this study, we designed a novel sulfur film coated on the three-dimensional nitrogen and cobalt co-doped carbon polyhedral wrapped on multi-walled carbon nanotubes sponge composite as a high-performance cathode material for rechargeable lithium-sulfur batteries. CNTs is employed to supply an interconnected conductive carbon network. Along with the abundant uniform micropores that provided by carbon derived from ZIF 67, sponge-like structure provides abundant mesopores that create favorable pathway for the electrolyte permeability and lithium ion diffusion. The doping of nitrogen and cobalt atom leads to improve electrical conductivity and enhance the surface polarity of the composite. Moreover, the strong interaction between cobalt and lithium polysulfides leads to efficiently suppress the shuttle effect. Figure 1 presents the photo of sponge-like composite and SEM image of composite after sulfur infiltration. We will report in detail about the latest results achieved on as cathode material for lithium-sulfur batteries.

ZnSe/N-Doped Carbon Nanoreactor with Multiple Adsorption Sites for Stable Lithium-Sulfur Batteries.

To commercially realize the enormous potential of lithium-sulfur batteries (LSBs) several challenges remain to be overcome. At the cathode, the lithium polysulfide (LiPS) shuttle effect must be inhibited and the redox reaction kinetics need to be substantially promoted. In this direction, this work proposes a cathode material based on a transition-metal selenide (TMSe) as both adsorber and catalyst and a hollow nanoreactor architecture: ZnSe/N-doped hollow carbon (ZnSe/NHC). It is here demonstrated both experimentally and by means of density functional theory that this composite provides three key benefits to the LSBs cathode: (i) A highly effective trapping of LiPS due to the combination of sulfiphilic sites of ZnSe, lithiophilic sites of NHC, and the confinement effect of the cage-based structure; (ii) a redox kinetic improvement in part associated with the multiple adsorption sites that facilitate the Li+ diffusion; and (iii) an easier accommodation of the volume expansion preventing the cathode damage due to the hollow design. As a result, LSB cathodes based on S@ZnSe/NHC are characterized by high initial capacities, superior rate capability, and an excellent stability. Overall, this work not only demonstrates the large potential of TMSe as cathode materials in LSBs but also probes the nanoreactor design to be a highly suitable architecture to enhance cycle stability.

Strongly trapping soluble lithium polysulfides using polar cysteamine groups for highly stable lithium sulfur batteries

Sulfur has become one of the most promising positive electrode materials for lithium sulfur batteries due to its high theoretical capacity and high energy density (2500 Wh kg−1). The use of common nonpolar carbon/sulfur composites has proved to be a good way to improve the performance, but they still cannot efficiently trap highly polar lithium polysulfides due to the weak interactions between nonpolar carbon and polar polysulfides. Herein, we report a new strategy of using polar cysteamine groups to trap polar polysulfides, leading to greatly enhanced capacity of ∼920 mAh g−1 at 1 C with a high Coulombic efficiency of ∼99.1%, and a long cycle life of over 600 cycles with a capacity retention higher than 80%. Importantly, in situ UV/Vis spectroscopy was employed to identify intermediates during cycling, which demonstrates the constructed unique polar cysteamine functionalized carbon nanotubes (CNTs) can greatly reduce the production of polysulfides and suppress the shuttle effect. The broken-bond model of linear polysulfane during cycling was further demonstrated by density functional theory calculations. The present strategy of using polar cysteamine-functionalized CNTs to trap soluble intermediates is promising and has significant potential for the development of highly efficient lithium sulfur batteries.

A review of cathode materials in lithium-sulfur batteries

Lithium-sulfur battery, one of the most prominent and widely studied batteries, takes sulfur as the cathode which has rich reserves in the earth. It has the characteristics of high energy density, high theoretical specific capacity, affordable cost, and environment-friendly. Although this system has many advantages, it has many essential shortcomings, such as the non-conductivity of active materials and discharge intermediates, shuttle effect, the volume effect of the sulfur cathode, and the dendritic growth of lithium. In this paper, we summarize the solutions and related research of cathode materials in the lithium-sulfur battery from three aspects: the improvement of conductivity, the alleviation of the shuttle effect, and the use of Li2S cathode. And put forward the suggestions and prospects for future improvement methods.