Capacity Of Lithium-sulfur Batteries Research Articles

Separator modification of lithium-sulfur batteries based on Ni-Zn bimetallic MOF derived magnetic porous Ni-C composites

Because of its high theoretical specific capacity, lithium-sulfur batteries are regarded as one of the most promising secondary batteries. However, there are still a series of problems, which seriously affect the commercial application of lithium-sulfur batteries. Therefore, a magnetic porous carbon material was developed in this work for the modification of lithium-sulfur battery separators, which may reduce the shuttle effect of polysulfides and increase its electrochemical performances. The solvothermal preparation of Ni-Zn bimetallic MOF precursors was followed by a high-temperature carbonization in nitrogen environment to sublimate Zn ions and produce porous structures, achieving Ni@C(Zn) composite. In order to improve the electrochemical performances of lithium-sulfur batteries, the Ni@C(Zn) composite was coated on one side of the polyethylene (PE) separator. Ni@C(Zn) composite displays good physisorption and chemisorption properties, and it can also operate as a secondary current collector to promote the usage of active materials as well as inhibiting shuttle effect of polysulfides. By using Ni@C(Zn) coated PE separator, the initial discharge specific capacity of lithium sulfur battery is as high as 1278.6 mAh g−1 at a current density of 0.05 C when the S cathode is loaded with 3 mg cm−2 active materials. Furthermore, the discharge specific capacity in the first cycle at 0.5 C is 749.4 mAh g−1, which remains at 461 mAh g−1 after 500 long cycles, and the capacity retention rate is as high as 61.5%. Even when the S loading is as high as 5 mg cm−2, it can still experience a stable cycle of 100 cycles at 0.2 C.

3D printing CO2-activated carbon nanotubes host to promote sulfur loading for high areal capacity lithium-sulfur batteries

3D printing CO2-activated carbon nanotubes host to promote sulfur loading for high areal capacity lithium-sulfur batteries

Horizontally aligned lamellar porous graphene/nickel composite for high volumetric capacity lithium-sulfur batteries

Although lithium-sulfur batteries have the advantages of gravimetric energy density, it remains a challenge to achieve high volumetric energy density in lithium-sulfur batteries due to the employment of conductive porous carbon with low tap density and high porosity. To this context, we synthesized a horizontally aligned lamellar porous graphene/nickel composite (LPG-Ni) as a dense sulfur host material to increase the volumetric capacity of lithium-sulfur batteries while retaining high gravimetric capacity. The nickel decorated on the surface of the porous graphene serves as active sites, effectively adsorbing and catalytically converting polysulfides, thus improving the redox kinetics and reducing shuttle effect. More importantly, the abundant pores on the graphene sheet are considered as a shortcut for lithium-ion diffusion, which accelerates the ion transport through the whole electrode. Owing to the synergistic effect, the as-prepared sulfur cathode exhibits both excellent ionic and electronic conductivity, and has a dense-stacked structure. Thus, the LPG-Ni/S cathode provides high gravimetric and volumetric capacity (718.7 mA h g-1cathode and 884.0 mA h cm-3cathode at 0.1C). Meanwhile, the battery exhibits superior rate capability (369.7 mA h cm-3cathode at 5C) and cycling performance (1000 cycles, 0.037% decay per cycle at 1C).

A “Three‐Region” Configuration for Enhanced Electrochemical Kinetics and High‐Areal Capacity Lithium–Sulfur Batteries

AbstractA main hurdle for the commercial application of lithium–sulfur (Li–S) batteries lies in inadequate loading of sulfur due to a huge volume change over charging–discharging, poor electric conductivity of sulfur and associated sulfides, and the shuttling effect of lithium polysulfides (LiPS). Herein, a universal “three‐region” configuration including: Region I (sulfur source region), Region II (LiPS electrocatalysis region), and Region III (multi‐functional shield) for high‐areal capacity Li–S batteries is proposed. Mechanism of the configuration including the competitive relationship between Region II and Region III based on the Sabatier principle is further confirmed through density functional theory theoretical simulation and a series of in situ experimental methods. Compared with a conventional mechanical mixing electrode structure, it is demonstrated that the orderly integration “three‐region” configuration is able to prevent shuttling of LiPS effectively, which delivers high gravimetric energy density at the sulfur loading of 10.7 mg cm−2. Furthermore, a pouch cell achieves a high capacity of 148.15 mAh at a sulfur loading of 108 mg, which is by far higher than that of most previous batteries and pouch Li–S cells. Impressively, with bending and even partial damage, the pouch cell can still work normally, showing considerable safety.

Development of Si/C6 Negative Electrode for High Capacity Lithium-Sulfur Batteries

Recently, lithium-sulfur batteries are attracting attention as large-capacity energy storage devices for renewable energy. Lithium-sulfur battery uses elemental sulfur (S8) as positive electrode and Li metal as the negative electrode, respectively. Although large theoretical capacity (1,672 mAhg-1) of the sulfur active material is expected as advantage, formation of Li dendrites at the Li metal surface during charge process is concerned as serious problem. In this study, we applied a negative electrode with Si to suppress the precipitation of Li dendrites. The theoretical capacity of Si is extremely high at 4,200 mAhg-1 and high energy density can be expected. However, Si has low cycle performance owing to their volume changes with Li+ insertion and desorption. In this study, several cells ([Li | 1M-LiFSI EC/DEC(=3/7) | x wt%-Si/C6] ) using nano-Si mixed electrodes with C6 ( x wt%-Si/C6 (x=5,10,25,50) ) were prepared and evaluated.As example, showing how the 5wt%-Si/C6 electrode is fabricated. C6:Si:Acetylene Black:PVdF was mixed into the NMP solvent at a weight ratio of 81:4:7:8. The mixed slurry was applied onto copper foil and dried at 353 K. The 5wt%-Si/C6 electrode was punched to φ 16 mm and pressed with a uniaxial force. [Li| 1M-LiFSI EC/DEC(=3/7) | x wt%-Si/C6] cells were prepared and investigated by charge-discharge test at 303 K.Fig. 1 shows the charge-discharge profiles at the first cycle of the [Li| 1M-LiFSI EC/DEC(=3/7) |x wt%-Si/C6] (x=5,10,25,50) cells (a) and the relationship between the number of cycles and discharge capacity (b) . The initial discharge capacity was higher than the theoretical capacity of C6 (ca. 360 mAhg-1). However, remarkable decrease in discharge capacity is confirmed in accordance with an increase in the mixing amount of Si. Miniaturization might be occurred due to the volume change of Si during the charge-discharge reaction. As a result, the reaction at the electrode/electrolyte interface should be degraded. Irreversible reactions might be occurred after 2nd cycle. In addition, the lowest discharge capacity was obtained at 10wt%. As a result, isolation of active material was also suggested. Therefore, it is necessary to consider improving the cycle characteristics by the use of additives and improvement of the negative electrode itself. In the presentation, we will report for improvement methods of charge-discharge properties, such as new binder and composites with electric conductive additives. Figure 1

Nickel-based metal–organic framework-derived Ni/NC/KB as a separator coating for high capacity lithium–sulfur batteries

The Ni/NC/KB composite derived from Ni-MOFs was used as a separator coating in the Li–S battery, effectively confining the polysulfides through the Ni nanoparticles and N-doping.

Selective S/Li2S Conversion via in-Built Crystal Facet Self-Mediation: Toward High Volumetric Energy Density Lithium-Sulfur Batteries.

The gravimetric, areal, and volumetric capacities pose important influences on market penetration for secondary batteries. Carbonaceous materials take a leading stand for the improvement of gravimetric and areal capacity in lithium-sulfur batteries; however, they exhibit some intrinsic deficiencies, including insufficient fixation on lithium polysulfides (LiPS) and low tap density, incurring poor volumetric performance and inferior cycling behavior. Here, we report a sulfur cathode based on highly conductive ZrB2 nanoflakes with only 2 wt % conductive carbon. The resultant closely packed ZrB2-S electrode delivers a high areal capacity of 8.5 mAh cm-2 and cell-level volumetric energy density of 533 Wh L-1 with a high sulfur loading of 7.8 mg cm-2 and an ultralow electrolyte dosage. With combined spectroscopic studies and theoretical calculation results, it was confirmed that an in-built Janus crystal facet self-mediation is on-site constructed by the exposed B and Zr atoms for an effective bonding and selective conversion on LiPS upon charge-discharge processes.

Constructing Defect-Rich MoS2/N-Doped Carbon Nanosheets for Catalytic Polysulfide Conversion in Lithium–Sulfur Batteries

Polysulfide dissolution is one of the inherent challenges in lithium–sulfur batteries (LSBs). The shuttle effect of soluble polysulfide species between the cathode and the anode can cause the loss of active materials and the attenuation of specific capacity in LSBs. Herein, the N-doped porous carbon (NC) nanosheets with uniformly anchored defect-rich MoS₂ nanosheets (MoS₂/NC) were constructed by a simple and low-cost method. The NC nanosheets facilitate transfer of lithium ion and electron and localize polysulfides via the Li–N chemical bond. The defect-rich MoS₂ nanosheets can be used as electrocatalysts to propel polysulfide conversion by abundant catalytic activity sites and thus control the shuttle effect as well as improve cycling performances of LSBs. Consequently, the defect-rich MoS₂/NC composites as separator modification present a high specific capacity of 1021 mAh g–¹ at 0.2 C after 100 cycles and superior long-term performances with enhanced specific capacities of 429 mAh g–¹ with a low capacity fading rate of 0.027% per cycle at 5 C after 1000 cycles. The reasonable construct strategy of defect-rich MoS₂/NC composites is effective in enhancing the electrochemical performances of LSBs and promoting their commercial applications.

Integrating hierarchical porous nanosheets in the design of carbon cloth-based sandwiched sulfur cathodes to achieve high areal capacity in lithium sulfur batteries

Due to Co3O4 nanosheets grown on carbon fiber surface and within inter-fiber spaces (as shown in the graph), sulfur cathodes integrating the modified carbon cloth (CC@pCo3O4) demonstrate a superior areal capacity than most of previously reported CC-based sulfur cathodes.

Multifunctional Effects of Sulfonyl-Anchored, Dual-Doped Multilayered Graphene for High Areal Capacity Lithium Sulfur Batteries

Li–S batteries (LSBs) require a minimum 6 mAh cm–2 areal capacity to compete with the state-of-the-art lithium ion batteries (LIBs). However, this areal capacity is difficult to achieve due to a major technical issue—the shuttle effect. Nonpolar carbon materials limit the shuttle effect through physical confinement. However, the polar polysulfides (PSs) only provide weak intermolecular interactions (0.1–0.7 eV) with these nonpolar carbon materials. The physically encapsulated PSs inside the nonpolar carbon scaffold eventually diffuses out and starts shuttling. Chemically interactive hosts are more effective at interacting with the PSs due to high binding energies. Herein, a multifunctional separator coating of nitrogen-doped multilayer graphene (NGN) and −SO3– containing Nafion (N-NGN) is used to mitigate PS shuttling and to produce a high areal capacity LSB. The Nafion is used as a binder instead of PVDF to provide an additional advantage of −SO3– to chemically bind the PS. The motive of this research is to investigate the effect of highly electronegative N and −SO3– (N-NGN) in comparison with the −OH, −COOH, and −SO3– groups from a hydroxyl graphene and Nafion composite (N-OHGN) to mitigate PS shuttling in LSBs. The highly conductive doped graphene architecture (N-NGN) provides efficient pathways for both electrons and ions, which accelerates the electrochemical conversion at high sulfur loading. Moreover, the electron-rich pyridine N and −SO3– show strong chemical affinity with the PS through polar–polar interactions, which is proven by the superior electrochemical performance and density functional theory calculations. Further, the N-NGN (5 h) produces a maximum areal capacity of 12.0 and 11.0 mAh cm–2, respectively, at 15 and 12 mg cm–2 sulfur loading. This areal capacity limit is significantly higher than the required areal capacity of LSBs for commercial application, which shows the significant strength of N-NGN as an excellent separator coating for LSBs.

Synthesis and Application of Spent Tea Leaves As the Sulfur Cathode for Lithium Sulfur Battery

Sulfur is able to react with Li in reversible reaction to form Li2S in the lithium sulfur battery configuration. The theoretical capacity of lithium sulfur battery is about 1672 mAh/g which is higher than the capacity of conventional Li-ion batteries. However, there are some problems should be overcome for the utilization of sulfur cathodes. It is common to use of carbon as the matrix to host sulfur cathodes and increase the conductivity. Previously, numerous carbons with specific morphology and porosity have been used. The presence of porous structures is believed can be able to facilitate the homogeneous infiltration of sulfur on the carbon pore structures and improves the connectivity between carbon and sulfur components. Generally, the synthesis process of carbon materials is very complex that cause the large scale production is expensive and difficult. Here, porous carbon was synthesized from biomass waste spent tea leaves by hydrothermal carbonization and ZnCl2 activation process. Hierarchical porous carbon with high surface area (1875 m2/g) and pore volume (1.15 cm3/g) was obtained at ZnCl2/carbon ratio 0f 4.0 and activation temperature of 800 C. As-obtained porous carbons were then utilized as as composite sulfur cathodes for Lithium Sulfur battery. The porous structure permits sulfur loading of 59.5 wt% to be diffused into the carbon host. The carbon-sulfur composite electrodes exhibited the electrochemical performance by showing an initial specific capacity of 1048 mAhg-1 at 0.05 C and maintained specific capacity of 627 mAhg-1 after 100 cycles. Furthermore it had good capacity retention of 428 mAhg-1 at 0.5 C even after 100 cycles, which reveals its promising roles as sulfur cathodes in lithium sulfur batteries.

The role of functional materials to produce high areal capacity lithium sulfur battery

Abstract The lithium sulfur batteries (LSBs) are considered as one of the promising next generation energy storage devices due to the high theoretical specific capacity of sulfur (1675 mAh g −1 ), naturally available, low cost. However, the practical LSBs are impeded by the well-known ‟shuttle effect” combined with other technical drawbacks. The ‟shuttle effect” causes rapid capacity decay, severe self-discharging and low active material utilization. The polysulfide (PS) which has lone pair electrons in each sulfur atom is considered as Lewis base and shows strong affinity to various polar, Lewis acid and catenation interactive materials but very weakly interacts with the non-polar conductive carbons. The ‟shuttle effect” occurs due to the diffusion of high order PS from the cathode to the anode and then low-order PS back to the cathode. The PS is polar and, due to a lone pair of electrons associated with the sulfur atom, is considered a Lewis base. As such, the PS shows a strong affinity with various polar and Lewis acid materials. In addition, a more novel trapping can be performance through a catenation reaction. For LSBs to compete with the state-of-the-art lithium ion batteries (LIBs), the LSB areal capacity need to be ∼6 mAh cm −2 (which is proportional to sulfur loading). To achieve this target the PS shuttling needs to mitigate, which can be achieved through using functional materials. This review addresses the aforementioned phenomena by considering the PS phase interacts with the various functional materials and how this impacts areal capacity and cycling stability of LSBs.

MoS2 anchored carbon nitride based mesoporous material as a polysulfide barrier for high capacity lithium-sulfur battery

Molybdenum disulfide (MoS2) anchored carbon nitride (CN) based nanomaterial have been developed by using the hydrothermal method, which confines sulfur on to the CN and is utilized as a sulfur host for Li-Sulfur (LiS) battery. The prepared material CN/MoS2 demonstrated enhanced electrochemical performance with an initial charge-discharge capacity of 1252 mAh g−1 and 1264 mAh g−1 at 0.5C rate, with a reversible capacity of 680 mAh g−1 after 200cycles. The enhanced capacity and cyclic stability for CN/MoS2 in comparison with the bare CN is attributed to anchored MoS2 which can change the structural, physiochemical and increased electrochemical active surface area of CN/MoS2 based hybrid.

Self-Discharge Behavior of Lithium-Sulfur Batteries at Different Electrolyte/Sulfur Ratios

The commercialization of lithium sulfur (Li-S) batteries is hindered by their poor cycling performance, including fast capacity fade, low Coulombic efficiency, and high self-discharge rate. The static electrochemical stability of Li-S batteries, which is usually described in terms of their self-discharge properties, was much less studied compared to the dynamic electrochemical stability under continuous cycling. In this article, a set of experiments designed to understand the correlation between the self-discharge process and various operational conditions were made by using freestanding carbon nanotube foams as cathodes. We found a strong dependence of the self-discharge rate on the depth of discharge and on the electrolyte/sulfur ratio. We show that the effects of the self-discharge on the subsequent discharge capacities of Li-S cells are closely related to the type and concentration of lithium polysulfide species in the electrolyte and their interaction with the Li anode. This relation is analyzed in detail in this article, showing that one should pay special attention to the state-of-charge during self-discharge and the other operational conditions in order to improve the cyclability and capacity of Li-S batteries. In addition, we also highlight the importance of an efficient anode protection to improve the static electrochemical stability of these batteries.

Manipulating Polysulfide Conversion with Strongly Coupled Fe3O4 and Nitrogen Doped Carbon for Stable and High Capacity Lithium–Sulfur Batteries

AbstractLi–S batteries are among the most promising energy storage technologies but their commercialization faces substantial challenges, largely due to difficulties in controlling their reaction pathways under practical conditions. Here, the synthesis of strongly coupled Fe3O4 and N‐doped carbon directly in flexible carbon cloth is demonstrated, as well as their novel use for hosting sulfur with outstanding performance for Li–S batteries. It is discovered that the synergistic effects of Fe3O4 and N‐carbon bring strong adsorption toward lithium polysulfide, and ensure nearly complete conversion of short‐chain polysulfide to Li2S during discharge. The Li2S solids generated on these novel hosts are extremely reactive and can be readily charged back to S without a noticeable overpotential. The critical roles of Fe3O4 and N‐doped carbon are studied and direct correlations are established between their surface concentration/crystallinity and the Li2S4 to Li2S conversion capacity. This novel manipulation of polysulfide conversion allows to fabricate freestanding and flexible sulfur cathodes that deliver a specific capacity of 1316 mAh g−1 at 0.1C and stable cycling for 1000 cycles at 0.2C under a high sulfur loading of ≈4.7 mg cm−2.

TiO2 quantum dots decorated multi-walled carbon nanotubes as the multifunctional separator for highly stable lithium sulfur batteries

Lithium sulfur battery is considered one of the most promising rechargeable energy storage devices due to its ultrahigh theoretical energy density and specific capacity. It still cannot be applied because of some key problems. In particular, the shuttle effect of soluble polysulfide compounds leads to the rapid attenuation of battery capacity, short cycle life and serious self-discharge effect. TiO2 quantum dots and polysulfide compounds have strong interactions and can capture soluble polysulfide compounds, thus inhibiting the shuttle effect. Herein, we introduce a battery separator based on TiO2 quantum dots modified multi walled carbon nanotubes to solve the shuttle effect and adapt to the expansion of electrodes during charging and discharging. The interlayer has abundant spacing and excellent conductivity. This strategy can significantly improve the stability of lithium sulfur batteries. As a result, Li-S cells with MWCNTs@TiO2 quantum dots modified separator deliver an initial capacity of 1083 mAh g−1 and keep a cycle capacity of 610 mAh g−1 after 600 cycles at the rate of 838 mA g−1, which maintains an average capacity decay of only 0.072% per cycle. This simple and effective method can greatly improve the application capacity of lithium sulfur batteries.

Enabling Enhanced Capacity in Lithium-Sulfur Batteries Via an Intermediate Radical

Lithium-sulfur batteries offer a tremendous increase in specific capacity compared to the current state-of-the-art lithium-ion batteries, with the sulfur cathode having a large theoretical capacity of 1672 mA h g-1.1 In practice, however, this large theoretical capacity is rarely achieved, particularly at high loadings of sulfur within the cathode, at low electrolyte amount, or at kinetically limiting high rates and low temperatures.2, 3 A primary reason for this is the highly insulating nature of sulfur and its lithium polysulfide and lithium sulfide (Li2Sx, 1 < x <8) discharge products. During charge and discharge, reduction and oxidation of sulfur species are confined to a primarily surface-based reaction pathway, which limits the total utilizable capacity as insulating discharge products precipitate and drive the voltage down to the cell’s lower voltage limits.4 While many efforts have focused on limiting the solubility of intermediate polysulfide species, it has been reported that higher donor number solvents can offer a pathway to greater electrochemical utilization of sulfur through a solution-based reaction pathway, primarily driven by the S3 .- radical.4 Here, we demonstrate that some higher donor number solvents, such as Dimethyl Sulfoxide (DMSO) and N,N-Dimethylacetamide (DMA), exhibit greater utilization and relative disproportionation to the S3 ·- radical, while others, like 1-methylimidazole (MeIm), show little presence of the S3 ·- radical and less first cycle discharge capacity. We investigate this unique phenomenon via ultraviolet-visible spectrophotometry at a high concentration of Li2S6 in each solvent. Relative concentration of each polysulfide species varies with overall concentration, and we choose to study relative speciation at high concentrations as this approximates the typical polysulfide concentrations found in electrolyte while cycling. Favorable disproportionation to the S3 ·- radical can be strategically used as a framework to optimize electrolytes for increased capacity in lithium-sulfur cells through a solution-based reaction pathway. Intelligent use of these radical-inducing solvents in conjunction with the predominantly used Dioxolane (DOL) and Dimethoxyethane (DME) electrolytes can enable greater sulfur utilization in traditionally capacity limiting scenarios, such as low temperature, high rates, and large sulfur loadings.

Analysis of Precipitation Effects in Li-S Batteries: Modeling, Simulation, and Experimental Perspectives

Lithium-sulfur (Li-S) batteries with organic electrolyte have attracted much interest recently because of their relatively high energy density. Being environmentally friendly and avoiding some of the disadvantages of other competing types of batteries (such as metal-air batteries, which are open systems and subject to external contamination), Li-S batteries have the potential to replace conventional Li-ion batteries in many applications. Although Li-S batteries are currently being investigated experimentally extensively by the research community, there are a limited number of theoretical studies predicting the limitations of these systems and, unfortunately, the existing studies are often contradictory. In this presentation we analyze the limitations of Li-S batteries using a comprehensive approach that involves modeling, simulation, as well as experimental measurements. First, in agreement with some recent computational and experimental results published in the literature [1], we show that the capacity of Li-S batteries is limited by surface passivation: Li2S and possibly higher order lithium polysulfides (LiPS) deposit on the surface of the cathode and passivate the active carbon-electrolyte interface. Because of surface passivation, Li ions are prohibited from reaching the electron conductive material in the cathode (i.e. the electron conductive material), limiting the capacity of the battery. We show that tunneling effects across the solid Li2S layer can be neglected and, because of the high resistivity of Li2S, the cathode material becomes unreachable as soon as the solid Li2S deposits on the surface of the electron conductive material. The solid reaction product does not deposit uniformly on the surface of the electron conductive material but it appears as nuclei that grow non-uniformly during discharge, in agreement with the classical nucleation theory. We also show that, because of the relatively high diffusivities, long range diffusion processes (from separator to cathode) can also be neglected for most organic electrolytes reported in the literature. Finally, a differential model that describes the nucleation and precipitation of Li2S and LiPS in the cathode is presented and the discharge curves are compared with experimental data. Unlike the existing works in the literature, which keep track of the statistical distribution and growth of the nuclei at each location in the cathode, our model is expressed entirely in the form of a differential system of equations that can be solved using finite-difference or finite-element methods. In this way, the numerical implementation of the model is much simplified compared with the existing models in the literature and can be easily implemented in standard finite element simulators. The theoretical model presented in this work is based on a differential implementation of the Kolmogorov [2] and Avrami [3] precipitation models and takes into consideration discrete nuclei formation and size evolution on the surface of the electron conductive material. The number of nuclei and growth rate is expressed locally in the form of two ordinary differential equations that are solved self-consistently with the transport equations for sulfur and Li ions. Notice that in reference 1 the number and size of nuclei is described in integral form at each node of the finite-element (or finite-difference) discretization. A detailed analysis of the limitations of Li-S batteries will be presented at the conference. In addition, a few possible solutions to overcome these limitations will also be proposed.

Honeycomb polyaniline-dodecyl benzene sulfonic acid (hPANI-DBSA)/sulfur as a new cathode for high performance Li–S batteries

Abstract In the last few years, there has been a growing interest in lithium–sulfur (Li–S) batteries due to their high theoretical capacity of 1672 mAh/g, long life cycle, and low cost. However, Li–S batteries have been plagued with fast capacity loss and dissolution and diffusion of the polysulfides. In this study, honeycomb polyaniline-dodecyl benzene sulfonic acid (hPANI-DBSA) was prepared through the breath figure (BF) method, then, sulfur was electrodeposited on hPANI-DBSA and used to investigate the electrochemical properties of the Li–S cells. The hPANI-DBSA/S exhibit a higher capacity and excellent reversible capacity of 873.5 mAh/g after 100 cycles at 0.1 C. An initial specific capacity of 848 mAh/g at 0.2 C and coulombic efficiency of 99.3% over 100 cycles was achieved. The results suggest that this approach can also be useful for applying the Li–S cathodes for use in high capacity lithium–sulfur batteries.

DTT-doped MWCNT coating for checking shuttle effect of lithium-sulfur battery

In order to improve the rate and reversible capacity of lithium-sulfur (Li-S) battery, a reagent of dithiothreitol (DTT) was utilized to check the dissolution and shuttle of long-chain lithium polysulfides (LiPSs) by cutting the disulfide bond (–S–S– bonds) in them. The slurry of DTT-doped multi-walled carbon nanotubes (MWCNTs) was coated on the surface of sulfur cathode as a shield to slice the long-chain LiPSs to short-chain ones for checking the dissolution and migration of LiPSs to lithium anode. The morphology and structure of the electrodes were observed by scanning electron microscopy (SEM). The electrochemical performance was tested by galvanostatic charge-discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The initial discharge capacity of S-DTT- carbon nanotube paper (CNTP) electrode reached 1670 and 949 mAh/g at 0.05 and 2 C respectively with a coulombic efficiency of over 99%. The electrode maintained a reversible specific capacity of 949 mAh/g after 45 cycles at 2 C. This suggested that the DTT-doped MWCNT coating can restrain shuttle effect and improve the rate and capacity of Li-S battery. The S-DTT-CNTP electrode not only accommodates the volume expansion but also provides stable electronics and ions channels.