Energy Density Lithium-sulfur Batteries Research Articles

ZIF 67@Ce-MOF derived Co-N-C@CeO2-C for separator modification of lithium sulfur batteries

High energy density Lithium-sulfur batteries (LSBs) have become one of the future energy storage devices. However, the shuttle effect induced by the diffusion of polysulfides between the positive and negative electrodes makes the application prospects of LSBs very challenging. So as to overcome this difficult challenge, a special Co-N-C@CeO2-C composite which displays the Co-N-C nanoparticle coated on CeO2-C nanorods structure was obtained using ZIF-67@Ce-MOF precursor, and applied as the separator modification material for LSBs. This Co-N-C@CeO2-C composite has a higher specific surface area and more micro/meso porous structures than the simple Ce-MOF derived CeO2-C nanorod. The presence of Co-N-C nanoparticles can induce the charge imbalance, resulting in more oxygen vacancy defects and plenty of active sites. By virtue of its excellent physical and chemical adsorption ability, the long chain polysulfide can be quickly bound to the surface of the material, furthermore the metal active centers are used to accelerate the transformation of polysulfides, effectively inhibiting its shuttle effect. Moreover, the combination of Co-N-C enhanced the conductivity of CeO2-C nanorod and the mobility of lithium ions. Therefore, when the sulfur content is 2.8 mg cm−1, the specific capacity of 915.9 mAh g−1 is released under 0.5 C, and there is still 46.63 % capacity retained after 700 cycles. Even under a high sulfur area density of 5 mg cm−1, an initial discharge capacity of 933.9 mAh g−1 can be achieved, furthermore it can maintain 72.75 % of the initial capacity at the 120th cycle, demonstrating its application value.

Dual-stage polyporate framework with redox mediator for high loading lithium sulfur batteries

Realizing a high sulfur loading cathode is a necessary measure for assembling a high actual energy density lithium sulfur battery, which requires consideration of conductivity, reaction interface, confinement of lithium polysulfide, and redox kinetics. Herein, a pomegranate-inspired dual-stage porous graphene foam with large cavity skeletons and submicron small cavity carriers is obtained by combining the bubble-template and the flash-freezing ice-template. Furthermore, the redox mediator of poly (1-aminoanthraquinone) is electropolymerized onto it to obtain a sulfur host with high specific surface area and strong confinement capability. The nanosized sulfur deposition behavior and the rich electronic relay capability of the sulfur host are analyzed by the independent gradient model combined with in-situ Raman spectroscopy. Besides, a few of electro-depolymerization products of poly (1-aminoanthraquinone) are confirmed to be able to migrate to the anode surface to stabilize lithium deposition. With these merits, the assembled lithium sulfur batteries exhibit a discharge capacity of 1214 mAh g−1 and a high capacity retention rate of 75.1 % after 800 cycles at a sulfur loading of 10.0 mg cm−2, and provide an excellent areal capacity of 17.5 mAh cm−2 (867 mAh g−1) even at an ultra-high sulfur loading of 20.1 mg cm−2.

Double hollow spherical SnO2@Co3O4 applied to separator for efficient catalysis of polysulfides in lithium-sulfur batteries

High energy density lithium-sulfur batteries have been greatly suffered by the shuttle effect of lithium polysulfides. In this work, SnO2@Co3O4 double hollow spheres are synthesized to form a unique heterojunction structure that can efficiently catalyze and strongly absorb the regulation of polysulfides, which can catalyze the conversion of needle-like polysulfides into flower-like structures when applied in separator modification, effectively blocking the polysulfides in the cathode side and greatly improving the battery performance and cycle stability. At 0.5C current density, the initial discharge specific capacity of SnO2@Co3O4 separator battery is 893 mAh g−1, and its capacity degradation rate is only 0.082 % in 500 turns of cycling. Under harsh conditions (sulfur areal density = 6 mg cm−2, E/S = 5 μL mg−1), SnO2@Co3O4 separator cells can also achieve an area capacity of 4.03 mAh cm−2 at 0.1C. Additionally, the SnO2@Co3O4 separator cells also have high stability and cycling performance at different temperatures.

Multifunction-balanced porous carbon and its application in sulfur-loading host and separator modification for lithium–sulfur batteries

Lithium–sulfur batteries have been researched extensively because of their high energy density and low price. However, the poor conductivity of sulfur, the shuttle effect of polysulfide, the slow redox kinetics of sulfur species, and the significant volume expansion and contraction during charging and discharging have hindered the commercial application of lithium–sulfur batteries. In this study, a simple, scalable, and cost-effective strategy was developed to control the balance of the porosity, specific surface area, graphitization, heteroatom co-doping, and polar-polar interactions of a biomass carbon source. With this strategy, multifunctional porous carbon materials with three-dimensional network structures were prepared to serve as sulfur-loading hosts with high specific surface area, strong adsorption activity, and good conductivity. Moreover, the optimal porous carbon material was directly coated on a commercial separator, and the modified separator was found to further improve the electrochemical performance of a lithium–sulfur battery. As a result, for the battery with GPCS-3 as cathode electrode and modified separator as separator, the initial discharge capacity at 1.0C is 926.2 mAh g−1. After 300 cycles, the discharge capacity is 712.7 mAh g−1, and the average capacity decay is only 0.077 % per cycle. Since the three-dimensional network structure material exhibits good performance as a sulfur-loading host as well as the ability to effectively modify a separator, this study provides a valuable strategy for the fabrication of high energy density lithium–sulfur batteries.

Enhanced Electron Delocalization within Coherent Nano-Heterocrystal Ensembles for Optimizing Polysulfide Conversion in High-Energy-Density Li-S Batteries.

Commercialization of high energy density Lithium-Sulfur (Li-S) batteries is impeded by challenges such as polysulfide shuttling, sluggish reaction kinetics, and limited Li+ transport. Herein, a jigsaw-inspired catalyst design strategy that involves in situ assembly of coherent nano-heterocrystal ensembles (CNEs) to stabilize high-activity crystal facets, enhance electron delocalization, and reduce associated energy barriers is proposed. On the catalyst surface, the stabilized high-activity facets induce polysulfide aggregation. Simultaneously, the surrounded surface facets with enhanced activity promote Li2S deposition and Li+ diffusion, synergistically facilitating continuous and efficient sulfur redox. Experimental and DFT computations results reveal that the dual-component hetero-facet design alters the coordination of Nb atoms, enabling the redistribution of 3D orbital electrons at the Nb center and promoting d-p hybridization with sulfur. The CNE, based on energy level gradient and lattice matching, endows maximum electron transfer to catalysts and establishes smooth pathways for ion diffusion. Encouragingly, the NbN-NbC-based pouch battery delivers a Weight energy density of 357Wh kg-1, thereby demonstrating the practical application value of CNEs. This work unveils a novel paradigm for designing high-performance catalysts, which has the potential to shape future research on electrocatalysts for energy storage applications.

A Novel Approach for the Development of a Scalable, High Energy Density, and Long Life Lithium-Sulfur Battery Technology

Rechargeable lithium-sulfur (Li-S) batteries represent one of the most promising “Beyond Li-ion” battery chemistries due to their high theoretical specific energies ~2,500 Wh/kg.1,2 However, Li-S batteries face substantial technical challenges that must be overcome before they become commercially viable.3 One of the major technical challenges is low practical specific capacity and fast performance degradation due to the formation, migration, and shuttling of intermediate lithium polysulfides (PSs). Several strategies have been used to trap the PS species either chemically or physically; however, they either incur increased cost due to the use of expensive catalysts4 or suffer from the reduced battery specific energy due to added inactive weights from the cell design.5,6 We showed previously a novel strategy to address the PS-shuttle issue using a nanolayer polymer modified high surface area carbon (NPC) as a new type of PS-trapping material (Fig. 1a).7,8 When thin films of NPC were coated on sulfur electrodes (NPC-S), we found that our NPC-S based Li-S battery demonstrated a high discharge specific capacity (~1,600 mAh/g) that is nearing sulfur’s theoretical specific capacity (Fig. 1b). We also showed that our molecular dynamics simulation suggested the observed high specific capacity was attributed to NPC’s strong PS trapping capability via dipole-dipole interactions (Fig. 1c).In this presentation, we will show our continued research effort on this novel approach to further stabilize the long-term battery cycle stability and battery product scalability. We believe our novel approach holds a high promise of developing of a scalable, high energy density, and long life Li-S battery technology for many high-energy-density demanding applications. References Zhang, S. S., Journal of Power Sources 2013, 231, 153-162.Manthiram, A.; Fu, Y.; Su, Y.-S., Accounts of Chemical Research 2013, 46 (5), 1125-1134.Chen, Z. X.; Zhao, M.; Hou, L. P.; Zhang, X. Q.; Li, B. Q.; Huang, J. Q., Advanced Materials 2022, 2201555.Hamal, D.; Awadallah, O.; El-Zahab, B., Catalysis in Lithium-Sulfur Cathodes for Improved Performance and Stability. In 242nd The Electrochemical Society Meeting, Atlanta, GA, USA, 2022.Chung, S.-H.; Han, P.; Singhal, R.; Kalra, V.; Manthiram, A., Advanced Energy Materials 2015, 5 (18).Singhal, R.; Chung, S.-H.; Manthiram, A.; Kalra, V., Journal of Materials Chemistry A 2015, 3 (8), 4530-4538.Hasan, W.; Hyynh, K.; Razzaq, A.; Smdani, G.; Shende, R.; Paudel, T.; Xing, W., "Scalable, High Energy Density Lithium-Sulfur Batteries". In NASA Battery Workshop, November 15-17, 2022 , Huntsville, AL, USA, 2022.Hasan, W.; Huynh, K.; Razzaq, A. A.; Sumdani, G.; Shende, R.; Paudel, T.; Xing, W., #A01-0417, “An Effective Polysulfide Trapping Strategy for the Development of a Scalable, High Energy Density Lithium-Sulfur Battery”, 243rd ECS Meeting, Boston, MA, May 28 – June 2, 2023. Acknowledgment This work was supported by the Larry and Linda Pearson Endowed Chair at the Department of Mechanical Engineering, South Dakoda School of Mines and Technology. Figure 1

The “dual-layer sulfur cathode” strategy: An In2S3/Bi2S3@rGO heterostructure as an interlayer/modified separator for boosting the areal capacities of lithium-sulfur batteries

The specific energies and energy densities of lithium–sulfur (Li-S) batteries are influenced by various cell parameters, including the sulfur loading, the sulfur weight percentage in the cathode, and the electrolyte/sulfur ratio. An In2S3/Bi2S3@rGO heterostructure was obtained by growing indium sulfide nanoparticles on the surface of bismuth sulfide nanoflowers in a graphene oxide (GO) solution via a one-step solvothermal approach. This structure was introduced as a modified separator/dual-layer sulfur cathode for Li-S batteries. The Bi2S3/In2S3 heterointerfaces act as active sites to speed up interfacial electron transfer, along with the entrapment, diffusion, and transformation of lithium polysulfides. A Li-S cell containing a dual-layer sulfur cathode (thin layer of In2S3/Bi2S3@rGO sandwiched between two thick layers of sulfur) and coupled with an In2S3/Bi2S3@rGO-coated separator suppressed the polysulfide shuttle effect. The cell based on the dual-layer sulfur cathode technology and operated at a current rate of 0.3C achieved a high capacity (7.1 mAh cm−2) after the 200th cycle, giving an electrolyte/sulfur ratio (10 µL mg−1) under a high sulfur loading (11.53 mg cm−2). These results demonstrate the unique nature of the dual-layer sulfur cathode technique, which can yield high energy density Li-S batteries with high sulfur loadings and low electrolyte/sulfur ratios.

An Effective Polysulfide Trapping Strategy for the Development of a Scalable, High Energy Density Lithium-Sulfur Battery

Rechargeable lithium-sulfur (Li-S) batteries represent an attractive, “beyond Li-ion”, battery technology because they offer a high specific energy of 2,500 Wh/kg at the material level1 and 550 Wh/kg at the cell level.2 However, Li-S batteries face substantial technical challenges that have thus far prevented the realization of the battery’s tremendous performance potentials.3 One of the major technical challenges is low practical specific capacity and fast performance degradation due to the formation, migration, and shuttling of intermediate lithium polysulfides (PSs). Several strategies have been used to trap the PS species either chemically or physically; however, they either incur increased cost due to the use of expensive catalysts4 or suffer from the reduced battery specific energy due to added inactive weights from the cell design.5,6 We will present a novel strategy to address the PS-shuttle issue using a nanolayer polymer modified high surface area carbon (NPC) as a new type of PS-trapping material.7 When thin films of NPC were coated on sulfur electrodes (NPC-S), we found that our NPC-S based Li-S battery demonstrated a high discharge specific capacity (~1,600 mAh/g) that is nearing sulfur’s theoretical specific capacity. Our molecular dynamics simulation suggests such an excellent performance is attributed to NPC’s strong PS trapping capability via dipole-dipole interactions. We will show that, using a sustainable starting material, our approach is low-cost and economically scalable for the advanced Li-S battery technology. References Zhang, S. S., Journal of Power Sources 2013, 231, 153-162.Manthiram, A.; Fu, Y.; Su, Y.-S., Accounts of Chemical Research 2013, 46 (5), 1125-1134.Chen, Z. X.; Zhao, M.; Hou, L. P.; Zhang, X. Q.; Li, B. Q.; Huang, J. Q., Advanced Materials 2022, 2201555.Hamal, D.; Awadallah, O.; El-Zahab, B., Catalysis in Lithium-Sulfur Cathodes for Improved Performance and Stability. In 242nd The Electrochemical Society Meeting, Atlanta, GA, USA, 2022.Chung, S.-H.; Han, P.; Singhal, R.; Kalra, V.; Manthiram, A., Advanced Energy Materials 2015, 5 (18).Singhal, R.; Chung, S.-H.; Manthiram, A.; Kalra, V., Journal of Materials Chemistry A 2015, 3 (8), 4530-4538.Hasan, W.; Hyynh, K.; Razzaq, A.; Smdani, G.; Shende, R.; Paudel, T.; Xing, W., "Scalable, High Energy Density Lithium-Sulfur Batteries". In NASA Battery Workshop, November 15-17, 2022 , Huntsville, AL, USA, 2022. Acknowledgment This work was supported by the Larry and Linda Pearson Endowed Chair at the Department of Mechanical Engineering, South Dakoda School of Mines and Technology and by the South Dakota Governor’s Research Center for Electrochemical Energy Storage. Figure 1

Lead-Free Ferroelectric Ba0.9Sr0.1TiO3 Coupled Polysulfide Trapping on Sulfur Cathode in Stable and High Energy Density Lithium-Sulfur (Li-S) Batteries

In the present work we are reporting electrochemical performance of Lead-free ferroelectric Ba0.9 Sr0.1TiO3 (BST), a high polarization (~14.58 μC/cm2 ) material, to assist polysulfide chemisorption via their permanent dipoles. The performance of fabricated cathodes in terms of structural, electronic, morphological, and electrochemical characteristics have been carried out with various concentrations of ferroelectric inclusion. X-ray diffraction analysis revealed tetragonal symmetry (c/a=1.0073) and the Raman spectroscopic studies confirmed A1(TO1), A1(TO2), A1(TO3) and A1(LO3) optical modes of the tetragonal phase of the BST modified composites. All the compositional cations were observed in SEM-based EDAX analysis, confirming homogeneous distribution of BST in the sulfur cathode system having grain sizes of ~ 1-1.5 μm. The porosity in the composites were found to be negligible based on the microscopic analysis. Considering that polar substances have good affinity towards trapping polysulfides and that can provide more stable reacting environment in the cathodic site, ferroelectric BST was employed to trap such polysulfide intermediates due to possessing permanent dielectric polarizability. With the spontaneous polarization induced by composite structure, ferroelectric material provides internal electric fields and increase chemisorption with the reactive heteropolar material. Thus, BST coupled C-S composite cathodes improved the electrochemical performance in comparison with the cathodes composed of only C-S. A stable high capacity of 1200 mAh/g was achieved for the BST coupled C-S cathodes in contrast to 700 mAh/g in pristine C-S cathode, due to reduction in polysulfides migration influence by the electric field of the BST ferroelectric. Two plateaus were observed, namely at 1.5 V and 3 V in the charge/discharge characteristics. The detail results will be presented at the ECS meeting 2023.

Improving performances of Lithium-Sulfur cells via regulating of VSe2 functional mediator with Doping-Defect engineering and Electrode-Separator integration strategy

The sluggish redox kinetics and the severe shuttle effect of soluble lithium polysulfides (LiPSs) are the main key issues which would hinder the development of lithium-sulfur (Li-S) batteries. In this work, a nickel-doped vanadium selenide in-situ grows on reduced graphene oxide(rGO) to form a two-dimensional (2D) composite Ni-VSe2/rGO by a simple solvothermal method. When it is used as a modified separator in Li-S batteries, the Ni-VSe2/rGO material with the doped defect and super-thin layered structure can greatly adsorb LiPSs and catalyze the conversion reaction of LiPSs, resulting in effectively reducing LiPSs diffusion and suppressing the shuttle effect. More importantly, the cathode-separator bonding body is first developed as a new strategy of electrode-separator integration in Li-S batteries, which not only could decrease the LiPSs dissolution and improve the catalysis performance of the functional separator as the upper current-collector, but also is good for the high sulfur loading and the low electrolyte/sulfur (E/S) ratio for high energy density Li-S batteries. When the Ni-VSe2/rGO-PP (polypropylene, Celgard 2400) modified separator is applied, the Li-S cell can retain 510.3 mA h g−1 capacity after 1190 cycles at 0.5C. In the electrode-separator integrated system, the Li-S cell can still maintain 552.9 mA h g−1 for 190 cycles at a sulfur loading 6.4 mg cm−2 and 4.9 mA h cm−2 for 100 cycles at a sulfur loading 7.0 mg cm−2. The experimental results indicate that both the doped defect engineering and the super-thin layered structure design might optimally be chosen to fabricate a new modified separator material, and especially, the electrode-separator integration strategy would open a practical way to promote the electrochemical behavior of Li-S batteries with high sulfur loading and low E/S ratio.

High Energy Density Lithium-Sulfur Batteries Based on Carbonaceous Two-Dimensional Additive Cathodes.

The increasing demand for electrical energy storage makes it essential to explore alternative battery chemistries that overcome the energy-density limitations of the current state-of-the-art lithium-ion batteries. In this scenario, lithium-sulfur batteries (LSBs) stand out due to the low cost, high theoretical capacity, and sustainability of sulfur. However, this battery technology presents several intrinsic limitations that need to be addressed in order to definitively achieve its commercialization. Herein, we report the fruitfulness of three different formulations using well-selected functional carbonaceous additives for sulfur cathode development, an in-house synthesized graphene-based porous carbon (ResFArGO), and a mixture of commercially available conductive carbons (CAs), as a facile and scalable strategy for the development of high-performing LSBs. The additives clearly improve the electrochemical properties of the sulfur electrodes due to an electronic conductivity enhancement, leading to an outstanding C-rate response with a remarkable capacity of 2 mA h cm-2 at 1C and superb capacities of 4.3, 4.0, and 3.6 mA h cm-2 at C/10 for ResFArGO10, ResFArGO5, and CAs, respectively. Moreover, in the case of ResFArGO, the presence of oxygen functional groups enables the development of compact high sulfur loading cathodes (>4 mgS cm-2) with a great ability to trap the soluble lithium polysulfides. Notably, the scalability of our system was further demonstrated by the assembly of prototype pouch cells delivering excellent capacities of 90 mA h (ResFArGO10 cell) and 70 mA h (ResFArGO5 and CAs cell) at C/10.

Ultrathin NiO/Ni3S2 Heterostructure as Electrocatalyst for Accelerated Polysulfide Conversion in Lithium–Sulfur Batteries

The practical application of Lithium–Sulfur batteries largely depends on highly efficient utilization and conversion of sulfur under the realistic condition of high‐sulfur content and low electrolyte/sulfur ratio. Rational design of heterostructure electrocatalysts with abundant active sites and strong interfacial electronic interactions is a promising but still challenging strategy for preventing shuttling of polysulfides in lithium–sulfur batteries. Herein, ultrathin nonlayered NiO/Ni3S2 heterostructure nanosheets are developed through topochemical transformation of layered Ni(OH)2 templates to improve the utilization of sulfur and facilitate stable cycling of batteries. As a multifunction catalyst, NiO/Ni3S2 not only enhances the adsorption of polysulfides and shorten the transport path of Li ions and electrons but also promotes the Li2S formation and transformation, which are verified by both in‐situ Raman spectroscopy and electrochemical investigations. Thus, the cell with NiO/Ni3S2 as electrocatalyst delivers an area capacity of 4.8 mAh cm−2 under the high sulfur loading (6 mg cm−2) and low electrolyte/sulfur ratio (4.3 μL mg−1). The strategy can be extended to 2D Ni foil, demonstrating its prospects in the construction of electrodes with high gravimetric/volumetric energy densities. The designed electrocatalyst of ultrathin nonlayered heterostructure will shed light on achieving high energy density lithium–sulfur batteries.

Two birds with one stone: engineering siloxane-based electrolytes for high-performance lithium–sulfur polyacrylonitrile batteries

A lightweight and weakly solvating siloxane-based electrolyte is proposed to link the lithium metal anode and sulfurized polyacrylonitrile cathode simultaneously for high energy density lithium–sulfur batteries.

Molecular polysulfide-scavenging sulfurized–triazine polymer enable high energy density Li-S battery under lean electrolyte

Lean electrolyte with low electrolyte/sulfur (E/S) ratio is a crucial step for the advancement of high energy density lithium-sulfur (Li-S) batteries. However, the low E/S introduces serious kinetics issues where the cell can only last for a few cycles. Here, aiming to overcome the operational constraints, we rationally design covalently grafted sulfurized–triazine polymeric (STP) cathodes housing > 60% sulfur capable of cycling under lean electrolyte. As-developed STP cathodes at lean E/S: 4, 6, and 8 µL mgs–1 show improved sulfur reactivity and cycle-life, delivering 522, 574, and 601 mAh gs–1 at the 200th cycle. Further, at sulfur loading 5 mg cm–2 with E/S: 6 µL mgs–1, the Li-S cell exhibits 588 mAh gs–1 capacity with 93% Coulombic efficiency. Experimental and modeling tools reveal that the triazine cathode support allows covalent grafting and good wettability beneficial for facile Li ion and sulfur reactivity. As a result, the generated polysulfide is concurrently regulated in a molecularly fashion via bulk-immobilization involving abundant pyridinic–N and pyrrolic–N to confine within the electrode. Extending to construct a practical lean Li-S pouch cell with sulfur, lithium, and electrolyte accounting 53.7% cell's mass delivers an energy density of 371 Wh kg–1 that is par to the predicted values under lean electrolyte. Our study provides an invaluable resource in a potential way and future directions for developing practical high energy Li-S batteries.

Mitigating Polysulfide Shuttles with Upcycled Alkali Metal Terephthalate Decorated Separators

High energy density lithium–sulfur batteries (LSBs) are a potential replacement for lithium-ion batteries (LIBs). However, practical lifetimes are inhibited by lithium polysulfide (LiPS) shuttling. Concurrently, plastic waste accumulation worldwide threatens our ecosystems. Herein, a fast and facile strategy to upcycle polyethylene terephthalate (PET) waste into useful materials is investigated. Dilithium terephthalate (Li2TP) and dipotassium terephthalate (K2TP) salts were synthesized from waste soda bottles via microwave depolymerization and solution coated onto glass fiber paper (GFP) separators. Salt-functionalized separators with Li2TP@GFP and K2TP@GFP mitigated LiPS shuttling and improved electrochemical performance in cells. Pore analysis and density functional theory (DFT) calculations indicate the action mechanism is synergistic physical blocking of bulky LiPS anions in nanopores and diffusion inhibition via electrostatic interactions with abundant carboxylate groups. LSBs with K2TP@GFP separator showing highest LiPS affinity and smallest pore size demonstrated enhanced initial capacity as compared to non-modified GFP by 5.4% to 648 mAh g−1, and increased cycle 100 capacity by 23% to 551 mAh g−1. Overall, K2TP@GFP retained 85% of initial capacity after 100 cycles with an average capacity fading of 0.15% per cycle. By comparison, GFP retained only 73% of initial capacity after 100 cycles with 0.27% average capacity loss, demonstrating effective LiPS retention.

Dual-Layer Sulfur Cathode Integrating Sulfur Composite Electrode and Binder-Free Sulfur Thin Film for High Loading Li-S Batteries

The Lithium-sulfur (Li-S) battery is one of the most promising future electrochemical energy storage systems owing to the intrinsic advantages of sulfur such as its high energy density, low cost, and innocuous nature. For several decades, many research teams have tried to develop high performance Li-S batteries. Recently, various approaches for high sulfur loading have been demonstrated to achieve high energy density Li-S batteries. Many types of porous carbon materials (e.g., graphene, mesoporous carbons, hollow carbon spheres, and carbon nanotubes) have been used as a sulfur host. In many cases, however, the large-scale implementation to Li-S batteries has been discouraged due to the non-scalable synthesis process of these carbon materials. To improve the energy density of a sulfur cathode, we demonstrate a dual-layer sulfur cathode composed of a S-filled carbon electrode and a sulfur deposit film. First, a sulfur electrode was fabricated by uniformly embedding sulfur within the porous network of a carbon film. Then, an ultra-thin sulfur layer was constructed on the surface of the sulfur electrode through physical vapor deposition (PVD) of elemental sulfur

Cu-Mo Bimetal Modulated Multifunctional Carbon Nanofibers Promoting the Polysulfides Conversion for High-Sulfur-Loading Lithium-Sulfur Batteries.

High sulfur loading is essential for achieving high energy density lithium-sulfur (Li-S) batteries. However, serious issues such as low sulfur utilization, poor cycling stability, and sluggish rate performance have been exposed when increasing the sulfur loading for freestanding cathodes. To solve these problems, the adsorption/catalytic ability of high-sulfur-loading cathode toward polysulfides must be improved. Herein, based on excellent properties of cationic MOFs, we proposed that Cu-Mo bimetallic nanoparticles embedded in multifunctional freestanding nitrogen-doped porous carbon nanofibers (Cu-Mo@NPCN) with efficient catalytic sites could be prepared by facile MoO42- anion exchange of cationic MOFs. And, the sulfur embedded in Cu-Mo@NPCN was directly used as self-supporting electrodes, enabling a high areal capacity, good rate performance, and decent cycling stability even under high sulfur loading. The freestanding Cu-Mo@NPCN/10.3S cathode achieves a high volumetric capacity of 1163 mA h cm-3 and a decent areal capacity of 9.3 mA h cm-2 at 0.2 C with a sulfur loading of 10.3 mg cm-2. This work provides an innovative approach for engineering a freestanding sulfur cathode and would forward the development of cationic MOF-derived bimetallic catalysts in various energy storage systems.

Carbon Coated Metal-Based Composite Electrode Materials for Lithium Sulfur Batteries: A Review.

Lithium-sulfur battery is one of the most promising secondary battery systems due to their high energy density and low material cost. During the past decade, great progress has been achieved in promoting the performances of Li-S batteries by addressing the challenges at the laboratory-level model systems. With growing attention paid to the application of Li-S batteries, new challenges at practical cell scales emerge as the bottleneck. However, challenges remain for the commercialization of lithium-sulfur batteries. The current review mainly focused on metal-based catalysts decorated-carbon materials for enhanced lithium sulfur battery performance. Firstly, the synthesis methods of various carbon-sulfur composites are discussed, as well as the influence of different material structures on the electrochemical performance. Secondly, a variety of catalysts, including metal atoms, metal oxides, sulfides, phosphides, nitrides, and carbide-decorated carbon nanomaterials, are systematically introduced to determine how lithium can be enhanced by suppressing polysulfides and promoting redox conversion reactions. Also, analyzed the multi-step electrochemical reaction mechanism of the battery during the charging and discharging process, and provide a feasible path for the practical application of high energy density lithium-sulfur batteries.

Ultrahigh Sulfur Loading Tolerant Cathode Architecture with Extended Cycle Life for High Energy Density Lithium–Sulfur Batteries

AbstractLithium–sulfur batteries are regarded as the imminent energy storage device for high energy density applications. However, at practical sulfur loadings >5 mg cm−2, the cell suffers from severe capacity fade and durability. In the present work, a hybrid MoS2–WS2 heterodimensional structure is reported. The strain induced growth of transition metal dichalcogenides preferentially exposes edge sites and maximizes the geometric coverage for anchoring‐diffusion‐conversion of polysulfides to restrain the shuttle effect at practical S‐loadings. The systematic analysis (5–50 mg cm−2 of S‐loadings) reveals that the unique cathode architecture exhibits reversible S‐loading tolerance up to 28 mg cm−2. A high initial areal capacity of 32 mAh cm−2 with an area specific energy density of 67 mWh cm−2 is achieved with a low electrolyte volume/S‐loading ratio of 5 mL g−1. The strategy presented here can unlock high S‐loading Li–S cells with extended cyclability and high energy density.

Engineering Fe and V Coordinated Bimetallic Oxide Nanocatalyst Enables Enhanced Polysulfides Mediation for High Energy Density Li‐S Battery

Lithium sulfur (Li-S) batteries are expected to become the next-generation rechargeable energy storage devices owing to their high theoretical energy density, environmental benignity, and economic benefits. However, the undesirable lithium polysulfides (LiPSs) shuttling and sluggish redox kinetics of sulfur electrochemistry severely degenerate the wide-ranging electrochemical performances, hindering the commercialization process of Li-S batteries. Herein, a Fe and V coordinated bimetallic oxide FeVO4 (denote FVO) nanocatalyst with three-dimensional (3D) ordered structure is thoughtfully tailored and cooperated with the commercialized carbon nanotubes (CNT) to modify polypropylene (PP) separator for achieving high efficiencies of restraining the LiPSs shuttling and boosting the redox conversion of sulfur species. The Fe and V coordinated bimetallic oxide demonstrates enhanced anchoring and catalyzing activities toward sulfur species than single metal oxides of Fe and V with homometallic valence states due to the reconfiguration of the 3d-band. Impressively, the Li-S pouch cell with the FVO/CNT@PP separator achieves an energy density up to 341Wh kg-1 . The bimetallic oxide nanocatalyst used in this work enlightens a new designing route toward the separator modification for the development of high energy density Li-S batteries.