Cathode Material For Lithium-sulfur Batteries Research Articles

Vacuum-assisted sulfur crystallization process to improve the electrochemical performance of S@PC composite cathode materials for Li–S batteries

The melt-diffusion method and vapor-phase infusion method are high-frequency approach to composite sulfur to porous materials, but in these methods the crystallization process of sulfur occurs naturally and cannot be controlled. In this work, we prepared the S@PC composites via a facile dissolution-crystallization method and vacuum was used to assist the sulfur crystallization process. Comparing the composites prepared under vacuum and atmosphere, the results show that crystallized sulfur obtains a finer particle size under vacuum condition, which leads to an obviously increase in the initial discharge capacity, rate performance and cycle stability of the battery. The improvement of electrochemical performance is attributed to the fact that the finer sulfur provides quantities interface contact with conductor matrix and sufficient reaction sites between the electrode and electrolyte, accelerating charge transfer and the electrolyte diffusion. This research provides a technical support for the simplified and controllable preparation of cathode materials for lithium-sulfur batteries.

Biomass-Derived Carbon/Sulfur Composite Cathodes with Multiwalled Carbon Nanotube Coatings for Li-S Batteries

Lithium sulfur (Li-S) batteries stand out among many new batteries for their high energy density. However, the intermediate charge–discharge product dissolves easily into the electrolyte to produce a shuttle effect, which is a key factor limiting the rapid development of Li-S batteries. Among the various materials used to solve the challenges related to pure sulfur cathodes, biomass derived carbon materials are getting wider research attention. In this work, we report on the fabrication of cathode materials for Li-S batteries based on composites of sulfur and biomass-derived porous ramie carbon (RC), which are coated with multiwalled carbon nanotubes (MWCNTs). RC can not only adsorb polysulfide in its pores, but also provide conductive channels. At the same time, the MWCNTs coating further reduces the dissolution of polysulfides into the electrolyte and weakens the shuttle effect. The sulfur loading rate of RC is 66.3 wt.%. As a result, the initial discharge capacity of the battery is 1325.6 mAh·g−1 at 0.1 C long cycle, and it can still maintain 812.5 mAh·g−1 after 500 cycles. This work proposes an effective double protection strategy for the development of advanced Li-S batteries.

Two-dimensional square metal organic framework as promising cathode material for lithium-sulfur battery with high theoretical energy density

Lithium-sulfur (Li-S) batteries are considered as new generation of energy storage which offer cost-effectiveness and high energy density. However, their commercialization is restricted due to a host of challenges associated with the cathode material which usually contains sulfur with several drawbacks, including a low electronic conductivity of sulfur, the ‘shuttle effect’, and a large volume expansion during discharge. Herein, a novel two-dimensional porphyrin-like square metal organic framework (MOF) was explored as a promising cathode material using first principles density function theory (DFT) assisted by genetic global search. The DFT results show that, among 7 kinds of transition-metal organic framework (TM-MOF), only V-MOF and Ru-MOF is found to possess considerable chemical interactions with S8 and lithium polysulfides (LiPSs) in both vacuum and in electrolytic solvents, demonstrating distinguishable anchoring performance. The genetic global search and further DFT calculations indicate that the lithiation process on V-MOF exhibited a nearly constant open-circuit voltage of about 1.92 V to 1.95 V, and the theoretical energy density could reach up to 1469 Wh kg−1 when lithiation of S8 is considered on both sides of the substrate. The volume expansion of V-MOF during discharge is found to be about 34%, much smaller than 80% for solid sulfur. The band structure and density of states of V-MOF suggest metallic properties or a small band gap for bare surface or during the lithiation process. These results indicate that two-dimensional (2D) V-MOFs can serve as high-performance cathode material with distinguished anchoring performance to block polysulfide dissolution and thereby reduce the ‘shuttle effect’, and help attain ultra-high energy density. Our work points the way for designing and providing experimental realization of 2D layered materials applied in cathode with high energy density and stability.

Graphene-wrapped microspheres decorated with nanoparticles as efficient cathode material for lithium-sulfur battery

• Graphene-wrapped microspheres decorated with metal nanoparticles was developed. • Cr-Ni-NDs@G is an efficient multifunctional sulfur host material for Li-S batteries. • The interaction and conversion kinetic of lithium polysulfide were studied. • The sulfur cathode exhibits high specific capacity and cycling performance. Lithium-sulfur (Li-S) battery is now a promising technology for energy storage. However, the commercialization of Li-S battery was hindered by the shuttle effect of lithium polysulfide and the slow reaction kinetics of sulfur. In this study, MIL-101(Cr) with graphene oxide was composited together through spray-drying. Then, a graphene microsphere composite consisted of three-dimensional conductive network decorated with Cr-Ni-based nanodots (Cr-Ni-NDs) was developed through a facile heat treatment. The microsphere composite was denoted as Cr-Ni-NDs@G, which offers a porous structure and high surface area to increase the accommodation and uniform distribution of sulfur in the cathode. Meanwhile, the three-dimensional conductive network embedded by Cr and Ni nanoparticle not only improved the transportation of electrons, but also act as the active site strengthening the adsorption of lithium polysulfide, promoting the catalytic transformation of lithium polysulfide to Li 2 S. Due to these complementary features, the S/Cr-Ni-NDs@G cathode exhibited a high initial specific capacity (1222.3 mAh·g −1 at 0.2C) and good rate performance (706 mAh·g −1 at 3.0C). In addition, after 500cycles at 1.0C, the faded rate of per cycle of the Li-S battery is only 0.059%. The result demonstrated that S/Cr-Ni-NDs@G composite can be a promising energy storage material in the development of Li-S batteries.

Titania Containing Cathodes for Lithium-Sulfur Batteries: Case Studies by Electrochemical Impedance Spectroscopy

Electrochemical impedance spectroscopy is used to study novel cathode materials for lithium-sulfur batteries, based on commercial carbon and titania. Coin cells with Li anode are investigated at various stages of galvanostatic cycling. For comparison, also symmetrical coin cells with a pair of positive (S/C/TiO2) or negative (Li) electrodes are studied. In addition to the application of titania as a barrier material impeding the polysulfide diffusion in the electrolyte solution, the inherent Li-insertion activity of TiO2 (anatase) and its contribution to the sulfur redox reactions is discussed.

Regulate the reaction kinetic rate of lithium-sulfur battery by rational designing of TEMPO-oxidized cellulose nanofibers/rGO porous aerogel with monolayer MXene coating

The sluggish reaction kinetics, polysulfide shuttling and low-efficiently use of sulfur largely imped the rate performance and energy density of lithium-sulfur batteries. To overcome the bottleneck, we used 1D TEMPO-oxidized cellulose nanofibers (T-CNF) and 2D rGO nanosheets as “rebar” and “cement” to construct a tough framework, and the monolayer MXene (m-MXene) was uniformly wrapped on the framework forming a MXene-coated three-dimensional aerogel (MCG aerogel) with high ionic and electronic conductivity. It is worth mentioning that the negatively charged groups of MXene can not only accelerate the ion diffusion rate and the conversion process of polysulfides by anchoring polysulfides through strong adsorption sites, but also construct an ion selective layer to inhibit the shuttle effect of polysulfides. Moreover, the T-CNF-enhanced three-dimensional structure alleviates the negative impact of sulfur volume expansion during the charging and discharging process, making it possible to directly used the aerogel as self-supporting electrodes without any binder. Therefore, the T-CNF/rGO hybrid aerogels with monolayer MXene coating as cathode materials for Lithium-sulfur batteries exhibit high discharge capacity of 1470 mA h g−1 at 0.1 C and improved rate capability of 744 mA h g−1 at 5 C. The high-strength framework structure with uniform surface sulfur-anchor coating design strategy offers a new angle of regulating the diffusion kinetic rate of lithium-sulfur batteries.

An excellent adsorptive TiO2@yV2O5 (y = 0.025–0.045) bifunctional composite endowing high sulfur loading as cathode material for lithium-sulfur batteries

Low conductivity and shuttle effect of lithium polysulfides (LiPSs) are the major impediments to the development of lithium-sulfurbatteries. Therefore, there is an urgent need for a reasonably designed host to simultaneously meet the needs of sulfur and LiPSs storage and improve the conductivity of the cathode material. In this work, inspired by synergetic effect, we design excellent adsorptive TiO2@yV2O5 (y = 0.025–0.045) bifunctional composites. And the different compositions of matrix material can be fabricated via manipulating the amount of KOH, which combines the advantages of high stability of TiO2 and strong adsorption of V2O5. The V2O5 exists inside TiO2 and part of it is used to provide a cavity, which can buffer volume expansion and store LiPSs and sulfur. The other can enhance the activity and energy of TiO2, thereby go a step further enhance the reaction kinetics. In addition, this TiO2@0.040 V2O5/S electrode exhibits high capacity retention of 91% and 93% at 0.5 C and 1 C after 50 cycles. And the cell exhibits a small polarization (202 mV at 0.1 C, 202 mV at 0.2 C and 234 mV at 0.5 C).

3D Net-like GO-d-Ti3C2Tx MXene Aerogels with Catalysis/Adsorption Dual Effects for High-Performance Lithium-Sulfur Batteries.

High theoretical specific capacity and rich resources in nature make sulfur an ideal cathode material for lithium-metal batteries. However, the shuttle effect and sluggish reduction reaction kinetics of lithium polysulfides (LiPSs) seriously affect the performance of the batteries. Here, we report GO-d-Ti3C2Tx MXene aerogels with a novel three-dimensional (3D) reticular structure that served as sulfur host cathode materials for lithium-sulfur batteries (LiSBs), which benefits adsorption/catalytic conversion of LiPSs simultaneously. The dissolved LiPSs can be rapidly captured through chemisorption and then catalyzed into insoluble Li2S by low-coordinated-state Ti on the d-Ti3C2Tx MXene surface. The combination of adsorption and catalysis enormously improves the capacity and cycling performance of LiSBs. At an S mass loading of 1.5 mg cm-2, the cell with the S@GM0.4 composite electrode achieves excellent cycling performance. The discharge specific capacity of 1039 mA h g-1 (1.56 mA h cm-2) decays to 542.9 mA h g-1 after 1000 cycles with a capacity fading rate of 0.048% per cycle at 0.5 C. Even at an S mass loading of 4.88 mg cm-2, an areal capacity of 4.3 mA h cm-2 can be achieved at 0.2 C.

Novel Polyaniline-Silver-Sulfur Nanotube Composite as Cathode Material for Lithium-Sulfur Battery.

The preparation and characterization of a polyaniline–silver–sulfur nanotube composite were reported in this paper. The polyaniline–silver nanotube composite was synthesized via an oxidation-reduction method in the sodium dodecyl sulfate (SDS) solution. After being vulcanized, the polyaniline–silver–sulfur (Poly (AN–Ag–S)) nanotube composite was prepared as active cathode material and assembled into lithium–sulfur (Li–S) batteries with electrolyte and negative electrode materials. When the feed ratio of raw materials (aniline and AgNO3) was 2:1, the initial specific capacity of poly (AN–Ag–S) composite cells reached 1114 mAh/g. The specific capacity was kept at 573 mAh/g, and the capacity retention rate stayed above 51% after 100 cycles. The introduction of Ag into the composite cathode material can effectively solve the poor conductivity of sulfur and improve the Li–S battery performance.

On the Structure of Sulfur/1,3‐Diisopropenylbenzene Co‐Polymer Cathodes for Li‐S Batteries: Insights from Density‐Functional Theory Calculations

Sulfur co‐polymers have recently drawn considerable attention as alternative cathode materials for lithium‐sulfur batteries, thanks to their flexible atomic structure and the ability to provide high reversible capacity. Here, we report on the atomic structure of sulfur/1,3‐diisopropenylbenzene co‐polymers (poly(S‐co‐DIB)) based on the insights obtained from density‐functional theory calculations. The focus is set on studying the local structural properties, namely the favorable sulfur chain length (S n with n=1⋯8 ) connecting two DIBs. In order to investigate the effects of the organic groups and sulfur chains separately, we perform series of atomic structure optimizations. We start from simple organic groups connected via sulfur chains and gradually change the structure of the organic groups until we reach a structure in which two DIB molecules are attached via sulfur chains. Additionally, to increase the structural sampling, we perform temperature‐assisted minimum‐energy structure search on slightly simpler model systems. We find that in DIB‐S n ‐DIB co‐polymers, shorter sulfur chains with n∼4 are preferred, where the stabilization is mostly brought about by the sulfur chains rather than the organic groups. The presented results, corresponding to the fully charged state of the cathode in the thermodynamic limit, have direct applications in the field of lithium‐sulfur batteries with sulfur‐polymer cathodes.

Nitrogen-doped ordered multi-hollow layered carbon embedded with Mo2C as lithium polysulfide restrained cathode for Li-S batteries

Practical applications of lithium-sulfur (Li-S) batteries are constrained due to the poor electrical conductivity of sulfur, the shuttle effect, and the volume expansion during the cycle. In this study, N-doped ordered multi-hollow layered carbon embedded with Mo2C is successfully prepared (Mo2C@NC-NaCl) under the co-regulation of dicyandiamide and sodium chloride on the carbon material. In the carbon material, the multi-hollow layered carbon skeleton derived from biomass acts as an advanced sulfur host, which can accelerate electron transportation and buffer volume changes. The synergistic effect of Mo2C nanoparticles and pyridine N anchors lithium polysulfides and realizes fast sulfur electrochemistry. Benefiting from the above advantages, Mo2C@NC-NaCl with a sulfur loading of 2.5 mg cm−2 delivers a high initial discharge specific capacity of 1226.2 mAh g−1 at 0.2 C. Even at a high rate of 1 C, the battery still achieves an initial capacity of 853.7 mAh g−1 and the average capacity decay rate per cycle is 0.065% over 500 cycles. It is expected this work provides a new perspective for large-scale production of cathode materials for Li-S batteries.

Hollow Co-Fe LDH as an effective adsorption/catalytic bifunctional sulfur host for high-performance Lithium–Sulfur batteries

Lithium–sulfur batteries (LSBs) have been regarded as one of the most promising candidates for energy storage devices because of their high energy density, high theoretical capacity, and low cost. However, severe shuttle effect and sluggish redox reaction kinetics of lithium polysulfides (LiPSs), resulting in unsatisfactory rate performance and cycling stability, greatly hinder the further development of LSBs. Herein, we successfully synthesized a hollow structured Co-Fe layered double hydroxide (Co-Fe LDH). This Co-Fe LDH could inhibit the diffusion and accelerate the redox reaction kinetics of LiPSs, indicating that Co-Fe LDH is an effective adsorption/catalytic bifunctional sulfur host. When served as a cathode material for LSBs, the sulfur-loaded Co-Fe LDH (Co-Fe LDH@S) delivers a high specific capacity and outstanding cyclic stability with a low average capacity decay rate at 1 C. This composite cathode also displays excellent rate performance with a high capacity of 530.7 mAh g–1at 2 C. The results demonstrate that the Co-Fe LDH@S composites are a promising cathode for high-performance LSBs.

Sulfur/carbon binding with polar MoS3 as cathode materials for lithium-sulfur batteries

MoS3 is in situ grown on sulfur carbon composite (S/C-MoS3) surface by chemical oxidative reaction of (NH4)2MoS4. Based on the synergistic role of porous carbon and polar MoS3 with sulfur-like characteristic, polysulfides are effectively anchored and shuttle effect is greatly reduced. In particular, 10 wt% MoS3 bridged S/C composite exhibits the best electrochemical performance. After 100 cycles at 0.2C, the discharge specific capacity remains 727.6 mA h g−1, and the capacity retention rate is 59.0%. When cycling 300 times at 1C, the capacity is still maintained at 546.9 mA h g−1, and the coulomb efficiency is around 97.0%. The results show that MoS3 effectively improves the cyclic property of S/C composite for lithium‑sulfur battery.

Preparation of CoO/SnO2@NC/S composite as high-stability cathode material for lithium-sulfur batteries

Preparation of CoO/SnO2@NC/S composite as high-stability cathode material for lithium-sulfur batteries

Yttrium oxide nanorods as electrocatalytic polysulfides traps for curbing shuttle effect in lithium-sulfur batteries

Although lithium-sulfur (Li-S) batteries have high theoretical specific capacity, their development is limited by low reaction kinetics during solid-liquid conversion of polysulfides and severe dissolution of polysulfides leading in loss of active materials and the corrosion of Li metal. In this paper, a novel electrode material which synthesized by yttrium oxide (Y2O3) nanorods modified Ketjen black@sulfur (Y2O3/KB@S) composites is introduced and evaluated in Li-S batteries. Y2O3 nanorods have good adsorption-catalytic synergistic effect on polysulfides, which can curb the shuttle effect and enhance the redox kinetics of polysulfides. The initial specific discharge capacity of Y2O3/KB@S electrode shows 828 mAh g−1 at 0.5 C current density, and the capacity maintains at 388 mAh g−1 after 500 cycles with the areal sulfur loading of 3.1 mg cm−2. Furthermore, Y2O3/KB@S cathode delivered 5.09 mAh discharge capacity and retained 4.21 mAh after 100 cycles at 0.2 C current density when the areal sulfur loading increasing to 5.0 mg cm−2. Therefore, Y2O3 nanorods modified Li-S battery cathode material has good application potential in its industrialization process.

Rational design of an Allyl-rich Triazine-based covalent organic framework host used as efficient cathode materials for Li-S batteries

To overcome the loss of soluble lithium polysulfides (LiPSs) generated during the discharge process of lithium-sulfur (Li-S) batteries, a lot of efforts have been devoted to the design of novel micro- or nano-structured host materials, aiming to trap soluble polysulfide within the network. Covalent organic framework (COF) as porous materials have been receiving a great deal of attention. Herein, an allyl-rich triazine covalent organic framework (ART-COF) synthesized by 5-(allyloxy) isophthalaldehyde and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl) trianiline (TAPT) is used as cathode host material for Li-S batteries. Owning to the synergistic effect of physical force (through microporous channel) and chemical force (through C-S covalent bond and dipole–dipole interaction between nitrogen and lithium), the shuttle action of LiPSs to anode electrode can be effectively limited. ART-COF shows a high initial specific capacity of 1270 mAh g−1 which retains 1220 mAh g−1 after 100 charge–discharge cycles at 0.2C, and even at 1C it also demonstrates an initial specific capacity of 993 mAh g−1 which retains 818 mAh g−1 after 500 cycles with a low fading rate of 0.035% per cycle. This work represents a sustainable approach for developing highly stable and long-lived Li-S batteries.

Promoting polysulfides redox conversion by sulfur-deficient ZnS1−x hollow polyhedrons for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are deemed as the attractive systems for high-energy storage. However, the polysulfides shuttling with slow redox kinetics has seriously hindered their practical applications. Herein, sulfur-deficient zinc sulfide (ZnS1−x) hollow polyhedrons are synthesized as the multifunctional sulfur host material via the sulfurization and high-temperature annealing method. The unique hollow structure could supply adequate void spaces for sulfur loading and alleviate volumetric expansion of sulfur upon the cycling process. Besides, ZnS1−x hollow polyhedrons with abundant sulfur vacancies can provide effective adsorption sites to chemically immobilize polysulfides and enhance polysulfides redox conversion as confirmed by theoretical calculation results and electrocatalytical experiments. Thus, the S/ZnS1−x cathode delivers the remarkable initial capacity (1206 mAh g−1 at 0.2 C) and excellent cycling stability (592 mAh g−1 after 500 cycles at 1 C). The study points out the idea of functional cathode material for Li-S batteries based on a simple yet efficient vacancy engineering method.

Ionic-additive Crosslinked Polymeric Sulfur Composites as Cathode Materials for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are one of attractive energy conversion and storage system based on high theoretical specific capacity and energy density with low costs. However, volatile nature of elemental sulfur is one of critical problem for their practical acceptance in industry because it considerably affects electrode uniformity during electrode manufacturing. In this work, polymeric sulfur composite consisting of ionic liquid (IL) are suggested to reduce volatility nature of elemental sulfur, resulting in better processibility of the Li-S cell. According to systematic spectroscopic analysis, it is found that polymeric sulfur is consisting of repeating units combining with elemental sulfur and volatility of them is negligible even at high temperature. In addition, the IL-embedded polymeric sulfur shows moderate cycle performance compared to the cell with elemental sulfur. From these results, it is found that the IL-embedded polymeric sulfur composite is applicable cathode candidate for the Li-S cell based on their excellent non-volatility as well as their superior electrochemical performance.

A Supramolecular Complex of C60 -S with High-Density Active Sites as a Cathode for Lithium-Sulfur Batteries.

The well-known "shuttle effect" of the intermediate lithium polysulfides (LiPSs) and low sulfur utilization hinder the practical application of lithium-sulfur (Li-S) batteries. Herein, we describe a novel C60 -S supramolecular complex with high-density active sites for LiPS adsorption that was formed by a simple one-step process as a cathode material for Li-S batteries. Benefiting from the cocrystal structure, 100 % of the C60 molecules in the complex can offer active sites to adsorb LiPSs and catalyze their conversion. Furthermore, the lithiated C60 cores promote internal ion transport inside the composite cathode. At a low electrolyte/sulfur ratio of 5 μL mg-1 , the C60 -S cathode with a sulfur loading of 4 mg cm-2 exhibited a high capacity of 809 mAh g-1 (3.2 mAh cm-2 ). The development of the C60 -S supramolecular complex will inspire the invention of a new family of S/fullerenes as cathodes for high-performance Li-S batteries and extend the application of fullerenes.

Research progress of high performance cathode materials for lithium-sulfur batteries

Lithium-sulfur battery is supposed to be a key for the next generation of energy storage devices due to its advantages of high energy density, high theoretical specific capacity, low cost and environmental friendliness, and has attracted extensive attention from researchers. However, the intermediate products of lithium-sulfur batteries are easily dissolved in the electrolyte to produce shuttle effect. In addition, there is volume expansion, low inherent conductivity, slow dynamics and other factors, which limit its commercial application. This paper describes the working principle of lithium-sulfur batteries, reviews the current research status of lithium-sulfur battery cathode materials, analyzes the existing problems of lithium-sulfur batteries, summarizes the improvement methods of cathode materials, and prospects the future development direction of lithium-sulfur batteries.