Electrochemical Performance Of Sulfur Cathode Research Articles

Insights into the aspect ratio effects of ordered mesoporous carbon on the electrochemical performance of sulfur cathode in lithium-sulfur batteries

Tailoring porous host materials, as an effective strategy for storing sulfur and restraining the shuttling of soluble polysulfides in electrolyte, is crucial in the design of high-performance lithium-sulfur (Li-S) batteries. However, for the widely studied conductive hosts such as mesoporous carbon, how the aspect ratio affects the confining ability to polysulfides, ion diffusion as well as the performances of Li-S batteries has been rarely studied. Herein, ordered mesoporous carbon (OMC) is chosen as a proof-of-concept prototype of sulfur host, and its aspect ratio is tuned from over ∼ 2 down to below ∼ 1.2 by using ordered mesoporous silica hard templates with variable length/width scales. The correlation between the aspect ratio of OMCs and the electrochemical performances of the corresponding sulfur-carbon cathodes are systematically studied with combined electrochemical measurements and microscopic characterizations. Moreover, the evolution of sulfur species in OMCs at different discharge states is scrutinized by small-angle X-ray scattering. This study gives insight into the aspect ratio effects of mesoporous host on battery performances of sulfur cathodes, providing guidelines for designing porous host materials for high-energy sulfur cathodes.

A coral-like composite of CoP-modified polyaniline-derived carbon chain skeleton as an efficient sulfur host for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have attracted wide attention in the field of rechargeable batteries due to their high theoretical energy density. However, the severe “shuttle effect” of lithium polysulfides (LiPSs) and the slow conversion kinetics are key factors restricting the commercial application of LSBs. To address these issues, we designed and prepared a coral-like composite of CoP-modified polyaniline-derived carbon chain skeleton (CoP/C) as the sulfur host for LSBs. The carbon chains can provide multidirectional channels for the transport of Li+ and electron; and the uniformly scattered CoP can adsorb the LiPSs through chemical adsorption and simultaneously promote their conversion, thus the “shuttle effect” can be effectively alleviated. Meanwhile, the effect of the amount of aniline monomer on the electrochemical performance of sulfur cathode were studied. After sulfur loading, the CoP/C-300/S (with aniline monomer addition of 300 μL) exhibits the best electrochemical performance. At 1 C, after 500 cycles, it still maintains a reversible specific capacity of 478 mA h g−1, with a decay rate of 0.074% per cycle, indicating its excellent cycling stability. This work provides a new approach for the application of CoP material in advanced LSBs.

The Effect of Carbon Type and Solvent/Binder Ratio on the Structure and Performance of Sulfur Cathodes in Lithium-Sulfur Batteries

Lithium-Sulfur (Li-S) batteries are among the popular candidates for next-generation rechargeable energy storage devices due to their high specific capacity and superior energy storage capabilities. However, commercialization of Li-S batteries has been hindered by several challenges such as the insulating nature of sulfur, and the shuttling of soluble lithium polysulfides and accumulation of insulating deposits on the electrodes – leading to capacity degradation over extended cycling1.Several research efforts have been devoted to mitigating these challenges. Among the different approaches, many studies focus on addressing the poor conductivity of sulfur and lithium polysulfide shuttling simultaneously by developing conductive carbon hosts2,3. While improvements have been achieved in the development of host structures with better electronic conductivity and improved polysulfide trapping capability, many of those structures have advanced architectures that demand complex processing, expensive precursors, and often lower gravimetric sulfur loading (<70 wt%).This leads to expensive-to-produce electrodes that have lower true energy density than desired. What is needed are simple preparation methods that address the issues discussed above without overly complicated processing, and preferably already commercialized materials.In this work, we systematically investigate the effect of different electrode components, including various common carbons and polymeric binders. The effect of carbon type and loading is discussed. The effect of solvent to binder ratio in the electrode slurry preparation is also studied. By tuning the binder composition, types of conductive carbon black, and the amount of solvent, we observed a difference in the structure of the host medium and consequently the sulfur electrode. Specifically, a shell covering surrounding the sulfur particles was observed at low solvent/binder ratio. Increasing the solvent/binder ratio led to the disappearance of the shell coverings and particle agglomeration, which resulted in lower achieved capacity and reduced cycle life. Ketjen black offered the highest specific capacity, while the presence of shell covering achieved at a low solvent/binder ratio was found necessary for cycling stability.This work demonstrates the importance of electrode processing parameters on the structure and electrochemical performance of sulfur cathode in Li-S batteries. The new understandings from this work can provide guidance on electrode designs to achieve Li-S batteries with enhanced capacity and longevity.References G. Li et al., Adv. Mater., 30, 1705590 (2018).D.-W. Wang et al., J. Mater. Chem. A, 1, 9382 (2013).Y. Li and S. Guo, Matter, 4, 1142–1188 (2021).

Oxygen‐vacancy‐containing cerium oxide nanoparticle‐decorated nanonetwork‐structured carbon toward high‐performance lithium–sulfur batteries

AbstractLithium–sulfur (Li–S) batteries have been regarded as promising next‐generation energy‐storage devices owing to their inherently high theoretical energy density. Unfortunately, the poor capacity and cycling life caused by severe polysulfide shuttle effect and sluggish redox kinetics in sulfur cathodes greatly impede the practical application of Li–S batteries. Herein, a new class of nanonetwork‐structured carbon decorated with oxygen‐vacancy‐containing cerium oxide nanoparticles (NSC–CeO2−x), in which carbon skeleton is composed of highly conductive carbon nanotube core welded by hybrid carbon shell, has been developed via one‐step heating treatment of hybrid molecular brush and further employed as functional interlayer to modify separator of Li–S battery. Owing to the synergistic effect of the highly active CeO2−x nanoparticles and the three‐dimensional carbon nanonetwork in enhancing the preservation of the soluble polysulfides and boosting the redox kinetics of sulfur species, the NSC–CeO2−x significantly promotes the electrochemical performance of sulfur cathode. As a result, the as‐constructed Li–S batteries exhibit an ultrahigh initial sulfur utilization of 92.9% and an extremely large capacity of 751 mA h g−1 at a high rate of 5 C. Remarkably, a stable capacity of 728 mA h g−1 over 300 cycles at 1 C is also achieved.

Metalized Polyacrylates as Efficient Binder for a Sulfurized Polyacrylonitrile/Polydopamine Active Material in Sulfur Cathodes for Room Temperature Sodium–Sulfur Batteries

Promising binder systems with special chemical and mechanical functions are under extensive exploration to cope with serious volume change and harmful shuttle effect occurring during charge/discharge cycles of a sulfur cathode in sodium–sulfur (Na–S) batteries. In this aspect, sulfurized polyacrylonitrile (SPAN)/polydopamine (PDA) active materials are combined with different metalized polyacrylates (MPAAs) to result in a SPAN/PDA/MPAA binder system with peculiar morphology and superior mechanical and interfacial strengths. As the outer layer of SPAN/PDA/MPAA, MPAA can extend its long chains to interact with cathode components and, moreover, metal ions of MPAA can participate in the beneficial electron transport process. The results suggest that stability and electrochemical performance of the sulfur cathodes depend on the applied metal ions, which become better and better as the valence of metal ions change from mono (Na), di (Ca), and tri (Fe) to tetra (Ti). Cathode derived from SPAN/PDA/titanium polyacrylate (TiPAA) shows the best stability and electrochemical performance, exhibiting a rather high specific capacity of 1438 mAh g–1 at 0.2 C for 100 cycles and 1271 mAh g–1 at 1 C for 300 cycles. Hopefully, this study can provide a foundation on how to use different metal ions to manipulate the electrochemical performance of sulfur cathode in Na–S batteries.

Polydopamine as an interfacial layer to enhance mechanical and adhesive properties of the active materials in a sulfur cathode of sodium-sulfur batteries

Room temperature sodium-sulfur (Na-S) batteries are promising devices for energy storage system, but for practical applications volume expansion and detrimental shuttle effect of the sulfur cathode should be solved. Herein, we introduced a novel sulfur cathode system of using polydopamine (PDA) as an interlayer in between sulfurized polyacrylonitrile (SPAN) active material and pullulan-graft-sodium polyacrylic acid (PuA) binder. Active NH and OH functional groups of PDA interlayer serve as facile hydrogen bonding (H bonding) and/or chemical reaction sites to various functional groups of SPAN and PuA, thus forming an intimately packed SPAN/PDA/PuA composite with sufficient mechanical and interfacial adhesive strengths to survive from the dimensional variation of sulfur cathode during charge/discharge cycling. Moreover, various functional groups of the SPAN/PDA/PuA are capable of absorbing polysulfides to limit the shuttle effect. Sulfur cathode derived from SPAN/PDA/PuA exhibited a high specific capacity of 1340 mAh g−1 after 100 cycles at 0.2 C. Without the PDA interlayer, sulfur cathode derived from SPAN/PuA exhibits a much lower capacity of 790 mAh g−1. The role of PDA in promoting the stability and electrochemical performance of sulfur cathode is thus verified in this study.

Combined enhanced redox kinetics and physiochemical confinement in three-dimensionally ordered macro/mesoporous TiN for highly stable lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries with tremendous energy density possess great promise for the next-generation energy storage devices. Even though, the shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) seriously restrict practical applications of Li–S batteries. Herein, a three-dimensionally ordered macro/mesoporous TiN (3DOM TiN) nanostructure is established via using poly (methyl methacrylate) PMMA spheres as template. The interconnected macro/mesoporous channels are constructed to effectively alleviate the stacking of composite materials and render a large portion of inherent active sites exposed on the surface region. Moreover, TiN exhibits high electrical conductivity, which efficiently enhances charge-transfer kinetics and guarantees the favorable electrochemical performance of sulfur cathode. More importantly, the as-prepared 3DOM TiN suppresses the shuttle effect and improves the redox kinetics significantly due to strong affinity toward LiPSs. Attributed to these unique features, the S/3DOM TiN electrode achieves an ultrahigh initial discharge capacity of 1187 mAh g−1 at 0.2 C, and stable cycling performance of 552 mAh g−1 over 500 cycles at 1 C. Meanwhile, the discharge capacity retention of 701 mAh g−1 (3.5 mAh cm−2) can be endowed for the S/3DOM TiN electrode under high sulfur loading of 5 mg cm−2 after 100 cycles at 0.1 C. Therefore, the 3DOM TiN nanostructure electrocatalyst provides a promising path for developing practically useable Li–S batteries.

Hollow Molybdate Microspheres as Catalytic Hosts for Enhancing the Electrochemical Performance of Sulfur Cathode under High Sulfur Loading and Lean Electrolyte

AbstractLithium–sulfur battery possesses a high energy density; however, its application is severely blocked by several bottlenecks, including the serious shuttling behavior and sluggish redox kinetics of sulfur cathode, especially under the condition of high sulfur loading and lean electrolyte. Herein, hollow molybdate (CoMoO4, NiMoO4, and MnMoO4) microspheres are introduced as catalytic hosts to address these issues. The molybdates present a high intrinsic electrocatalytic activity for the conversion of soluble lithium polysulfides, and the unique hollow spherical structure could provide abundant sites and spatial confinement for electrocatalysis and inhibiting shuttling, respectively. Meanwhile, it is demonstrated that the unique adsorption of molybdates toward polysulfides exhibits a “volcano‐type” feature with the catalytic performance following the Sabatier principle. The NiMoO4 hollow microspheres with moderate adsorption show the highest electrocatalytic activity, which is favorable for enhancing the electrochemical performance of sulfur cathode. Especially, the S/NiMoO4 composite could achieve a high areal capacity of 7.41 mAh cm−2 (906.2 mAh g−1) under high sulfur loading (8.18 mg cm−2) and low electrolyte/sulfur ratio (E/S, 4 µL mg−1). This work offers a new perspective on searching accurate rules for selecting and designing effective host materials in the lithium–sulfur battery.

Puffed carbon/titanium carbide matrix to improve the electrochemical performance of sulfur cathode

Conductive titanium carbide (TiC) nanoparticles implanted into puffed rice carbon (PRC), forming a highly porous TiC/PRC host, is reported. Typically, PRC possesses cross-linked nano/microsheets with three-dimensional (3D) structure and large surface area, prepared by a puffing strategy. Moreover, TiC is further introduced into the carbon matrix (TiC/PRC) with excellent compatibility. TiC plays a dual role for not only enhancement of conductivity but also adsorption of soluble lithium polysulfides. When employed as a host of sulfur in LSBs, the designed TiC/PRC-S cathode exhibits improved rate capability, high reversible capacity of 1223.0 mA h g−1 at 0.1 C, and long cycling life of 884.5 mA h g−1 after 200 cycles. The excellent electrochemical performance is ascribed to the synergetic work of porous PRC architecture and polar conductive TiC with strong physisorption and chemisorption of soluble polysulfide simultaneously.

Porous carbon nanotubes microspheres decorated with strong catalyst cobalt nanoparticles as an effective sulfur host for lithium-sulfur battery

The commercialization of lithium-sulfur (Li–S) battery is largely obstructed by the slow redox kinetics of sulfur cathode and the shuttle effect of polysulfides during its operation, which negatively affect the battery rate capability and cycle life. Herein, a porous CNTs/Co microsphere is synthesized and applied as sulfur host material to boost the electrochemical performance of sulfur cathode. The porous conductive CNTs spherical network can realize a rapid charge and mass transfer via fast conduction of Li+-ions and mitigate the cathode volume expansion in the course of the cycles. Importantly, the Co metal nanoparticles can attain intense chemical adsorption and fast catalytic conversion of polysulfides. Because of the above merits, the high initial discharge specific capacity 1242.5 mAh g−1 was obtained for S-CNTs/Co composite at 0.2C. The capacity decay rate was only 0.066% per cycle at 1C over 300 cycles and the excellent rate performance at up to 3C could also be obtained. Moreover, the S-CNTs/Co composite delivered a high initial areal capacity of 5.7 mAh cm−2 at a high sulfur loading (5.9 mg cm−2), indicating broad perspectives of CNTs/Co as a sulfur host in lithium-sulfur battery.

Scalable TiO2 embedded sulfur bulks@MnO2 nanosheets composite cathode for long-cyclic lithium-sulfur batteries

Lithium‐sulfur batteries have stimulated great attention as an advanced power system for scale storage requirements due to the overwhelming energy density. However, the capacity degradation caused by polysulfide shuttle and volume expansion still impedes the practical application. Herein, we designed and fabricated a facile TiO2 embedded sulfur bulks@MnO2 nanosheets composite as scalable cathode for long-cyclic lithium-sulfur batteries. The TiO2 nanoparticles were embedded in sulfur bulks, which played important roles in the coverage of the uniform MnO2 nanosheets. The embedded TiO2 sites and external MnO2 nanosheets brought out the physic trapping and chemical synergistic encapsulation of polysulfides. Such a composite cathode exhibited high reversible capacity of 1289 mAh g−1 at 0.1 C and long-term cycling stability at high rate condition (430 mAh g‐1 after 500 cycles at 2 C). This work thus sheds new light on a scalable way to improve the electrochemical performance of sulfur cathode.

Systematic Study of Effect on Enhancing Specific Capacity and Electrochemical Behaviors of Lithium–Sulfur Batteries

AbstractHerein, a flexible method is designed to engineer nitrogen‐doped carbon materials (NC) with different functional and structural specialties involving N‐doping level, graphitization, and surface area via tuning the carbonization temperature of the pre‐prepared zeolitic imidazolate framework‐8 (ZIF‐8 ) crystals. With the aim to unveil the effect of these features on the electrochemical performance of sulfur cathode, these samples are evaluated as sulfur host and comprehensively investigated. NC‐800 (800 °C, 10.45%N, 1032.4 m2 g−1) exhibits the best electrochemical capability comparing with NC‐700 (700 °C, 16.59%N, 891.4 m2 g−1) and NC‐900 (900 °C, 7.59%N, 987.6 m2 g−1). High surface area and N‐doping can work together to well increase the capacity of sulfur cathode, thanks to the improved transportation of charge carriers and effective anchoring of active sulfur, while the latter specialty just makes sulfur cathode have decent capacity in case of low surface area. Graphitization and quaternary nitrogen favorably improve the electric conductivity of the electrode, empowering the improvement of discharge capacity initially and rendering the good cyclability cooperatively relying on the effective immobilization of active materials. The related results suggest the significance of rational design of carbon maxtrix for sulfur to improve the performance of Li‐S batteries.

Porous Carbon Paper as Interlayer to Stabilize the Lithium Anode for Lithium–Sulfur Battery

The lithium-sulfur (Li-S) battery is expected to be the high-energy battery system for the next generation. Nevertheless, the degradation of lithium anode in Li-S battery is the crucial obstacle for practical application. In this work, a porous carbon paper obtained from corn stalks via simple treating procedures is used as interlayer to stabilize the surface morphology of Li anode in the environment of Li-S battery. A smooth surface morphology of Li is obtained during cycling by introducing the porous carbon paper into Li-S battery. Meanwhile, the electrochemical performance of sulfur cathode is partially enhanced by alleviating the loss of soluble intermediates (polysulfides) into the electrolyte, as well as the side reaction of polysulfides with metallic lithium. The Li-S battery assembled with the interlayer exhibits a large capacity and excellent capacity retention. Therefore, the porous carbon paper as interlayer plays a bifunctional role in stabilizing the Li anode and enhancing the electrochemical performance of the sulfur cathode for constructing a stable Li-S battery.

Packing sulfur into carbon framework for high volumetric performance lithium-sulfur batteries

Low volumetric performance is a common bottleneck of carbon-based electrode materials for practical applications, owing to the low density of porous carbons caused by the intrinsic void space. Specifically, lithium-sulfur (Li-S) batteries as a hot topic of next-generation energy storage devices face the same dilemma that we have to balance their intrinsically electrochemical performance and volumetric performance. The use of conductive porous carbon materials in the cathode of Li-S batteries, such as mesoporous carbon, carbon nanotube and graphene-derived carbons, can effectively accelerate the reaction kinetics, improve the electrochemical performance of sulfur cathode and promote the practical application of insulting sulfur. However, addition of these materials results in massive void space in the electrode, which cannot meet the requirement of compact structure in real applications. Such electrodes usually deliver relatively low volumetric performance even though their gravimetric performance can reach a high value.

Enhanced electrochemical performance of sulfur cathode by incorporation of a thin conductive adhesion layer between the current collector and the active material layer

A novel coated current collector has been applied to improve the electrochemical performance of sulfur cathode. The conductive adhesion layer was successfully coated onto an Al foil by a simple slurry-coating method, as examined by scanning electron microscopy. The effect of the conductive adhesion layer on the electrochemical performance of sulfur cathode was investigated by charge–discharge cycle tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy. The results of electrochemical tests demonstrate that introducing conductive adhesion layer not only increases the rate capacity, but also greatly enhances the cycle performance of sulfur cathode with a specific capacity of 497.5 mAh g−1 after 50 cycles. The remarkable enhancements can be attributed to the reduction in charge transfer resistance. The curves of CV indicate that the sulfur cathode containing conductive adhesion layer displays an improved electrochemical reversibility.

Effect of Carbon Black Materials on the Electrochemical Properties of Sulfur-Based Composite Cathode for Lithium-Sulfur Cells

To investigate the effect of the electrode materials on the electrochemical performance of Li-S cells, sulfur cathodes were constructed using four types of carbon blacks: Ketjenblack EC-600JD (KB-600), Printex XE-2, Cabot BP-2000, and Super-P. It was found that the electrochemical performance of sulfur cathode was strongly dependent on the type of carbon black used. In the first discharge, the sulfur cathodes containing carbon blacks with a high surface area, KB-600 (SBET = 1270 m2/g), Printex XE-2 (SBET = 950 m2/g), or Cabot BP-2000 (SBET = 1487 m2/g), showed much higher discharge capacities (>1200 mA h/g) than the sulfur cathode (710 mA h/g) with Super-P (SBET = 62 m2/g). It was observed that the sulfur cathodes with KB-600, Printex XE-2, or Cabot BP-2000, which showed very similar discharge capacities one another at a low rate of 0.2 C, exhibited significantly different electrochemical behavior (the discharge capacity and midvoltage) at a high rate of 1.0 C. In particular, the sulfur cathode with KB-600 showed an extremely high capacity (831 mA h/g) with a midvoltage of 2.07 V at a 1.0 C rate, and excellent capacity retention (79%) after 50 cycles.