High Energy Density Lithium-sulfur 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.

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

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.

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

Evaluating the Effect of Binder for Sulfurized Polyacrylonitrile Cathode via Optical Fiber Sensors

AbstractSulfurized polyacrylonitrile (SPAN) is a very stable and promising sulfur‐based cathode material for high energy density lithium–sulfur (Li–S) batteries, which can circumvent the polysulfides dissolution issue. However, the stress concentration caused by volume change in SPAN cathodes is relatively significant but is rarely focused on. It is widely reckoned that the binder plays a key role in buffering the stress induced by electrode materials and hence maintains the integrity of electrodes. Nevertheless, the understanding of the actual effect of binders to SPAN cathodes from the aspect of mechanics remains to be deepened. Here, the optical fiber Bragg grating (FBG) is implanted into SPAN cathode films to in situ evaluate the electrochemo‐mechanical behaviors by using four different binders. The internal strain evolution of SPAN cathodes is affected by multiple factors of adhesion and mechanical properties of different binders. It is found that the SPAN cathode using poly(acrylic acid) (PAA) binder with outstanding mechanical properties experiences the largest strain change but the electrochemical performance is even better under high sulfur loading. Furthermore, the strain evolution is monitored under high sulfur loading condition and how the sulfur loading affects the signals of the built‐in FBG sensors is tried to figure out.

Synergistic constraint and conversion of lithium polysulfide using a 3D hollow carbon interlayer in ultrahigh sulfur content Li-S batteries

Low sulfur content and inevitable polysulfide shuttle effect have always been the critical obstacle of the practical application of high-energy–density lithium sulfur batteries. Herein, a waste passiflora edulis peel derived in-situ N-doping porous carbon (PINPC) combined with three-dimensional hollow carbon cloth interlayer (3DHCI) was designed and constructed by facile simultaneous activation/carbonization. The abundant porous structure and nitrogen heteroatom doping of the PINPC not only significantly confine the soluble polysulfides through the physical and chemical adsorption, but also the high conductivity of the 3DHCI effectively accelerate the conversion reaction of polysulfides encapsulated in the unique hollow carbon skeletons. Owing to the synergetic enhancement of the PINPC and 3DHCI, the sulfur contents of the corresponding sulfur cathode composites are easily regulated from 70 wt% to 95 wt%, whilst exhibiting excellent electrochemical performances. The PINPC/S with a sulfur content of 70 wt% and 3DHCI interlayer obtains a high initial discharge capacity of 1032 mAh·g−1 and then retains 954 mAh·g−1 at 0.2 C after 200 cycles. At 2 C, a durable cycle life with capacity retention of 86% can be achieved up to 500 cycles. Even with an ultrahigh sulfur content of 95 wt%, the relatively high initial discharge capacity of 692 mAh·g−1 and capacity retention of 96 % are also achieved at 0.2 C after 200 cycles. This work offers a potential design for high-performance lithium sulfur batteries simultaneously with a high sulfur content.

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.

A Permselective Coating Protects Lithium Anode toward a Practical Lithium-Sulfur Battery.

Lithium metal is a desirable anode for high-energy density lithium-sulfur (Li-S) batteries. However, its reliability is severely limited by dendrite growth and side reactions with polysulfides, which are yet challenging to solve simultaneously. Herein, we report a protective layer that works the same way as the ion-permselective cell membrane, yielding a corrosion-resistant and dendrite-free Li metal anode specially for Li-S batteries. A self-limited assembly of octadecylamine together with Al3+ ions on a Li metal anode surface produces a dense, stable yet thin layer with ionic conductive Al-Li alloy uniformly embedded in it, which prevents the passage of polysulfides but regulates the penetrated Li ion flux for uniform Li deposition. As a result, the assembled batteries show excellent cycling stability even with a high sulfur-loaded cathode, suggesting a straightforward but promising strategy to stabilize highly active anodes for practical applications.

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.

Cracking‐Controlled Slurry Coating of Mosaic Electrode for Flexible and High‐Performance Lithium–Sulfur Battery

AbstractThe realization of high‐performance thick S cathodes is a critical step to achieve high energy density lithium–sulfur (Li–S) batteries. However, it normally requires a complicated and time‐consuming fabrication processes to obtain high‐performance S cathodes with high mass loading. On the other hand, thick S cathodes fabricated with high‐speed slurry coating method show poor flexibility, capacity, and cycle life due to unpredictable electrode cracking. Herein, an industrial‐speed cracking‐controlled slurry coating method to generate mosaic‐like cracks in the S cathode is developed, which provides vertical channels to facilitate the rapid diffusion of electrolyte, adequate space to accommodate the volume expansion during cycling, and strain‐releasing structure to achieve high flexibility. With this simple method, thick Mosaic‐S cathodes (9 mAh cm−2) provide outstanding energy density, long cycle life, and outstanding flexibility under dynamic bending. This work paves the way for scalable fabrication of high‐performance S cathodes in the near future.

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.

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.

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.

Self-Supporting Carbon Nanofibers with Ni-Single-Atoms and Uniformly Dispersed Ni-Nanoparticles as Scalable Multifunctional Hosts for High Energy Density Lithium-Sulfur Batteries.

The energy density of lithium-sulfur batteries (LSBs) is currently hampered by modest sulfur loadings and high electrolyte/sulfur ratios (E/S). These limitations can potentially be overcome using easy-to-infiltrate sulfur hosts with high catalytic materials. However, catalytic materials in such hosts are very susceptible to agglomeration due to the lack of efficient confinement in easy-to-infiltrate structures. Herein, using carbon dots as an aggregation limiting agent, the successful fabrication of self-supporting carbon nanofibers (CNF) containing Ni-single-atoms (NiSA ) and uniformly dispersed Ni-nanoparticles (NiNP ) of small sizes as multifunctional sulfur hosts is reported. The NiSA sites coordinated by such NiNP offer outstanding catalytic activity for sulfur reactions and CNF is an easy-to-infiltrate sulfur host with a large-scale preparation method. Accordingly, such hosts that can be prepared on a large scale enable sulfur cathodes to exhibit high sulfur utilization (66.5 mAh cm-2 at ≈0.02 C) and cyclic stability (≈86.1% capacity retention after 100 cycles at ≈0.12 C) whilst operating at a high sulfur loading (50mg cm-2 ) and low E/S (5µL mg-1 ). This work provides a blueprint toward practical LSBs with high energy densities.

Advanced Nanostructured MXene-Based Materials for High Energy Density Lithium-Sulfur Batteries.

Lithium–sulfur batteries (LSBs) are one of the most promising candidates for next-generation high-energy-density energy storage systems, but their commercialization is hindered by the poor cycling stability due to the insulativity of sulfur and the reaction end products, and the migration of lithium polysulfide. MXenes are a type of emerging two-dimensional material and have shown excellent electrochemical properties in LSBs due to their high conductivity and large specific surface area. Herein, several synthetic strategies developed for MXenes since their discovery are summarized alongside discussion of the excellent properties of MXenes for LSBs. Recent advances in MXene-based materials as cathodes for LSBs as well as interlayers are also reviewed. Finally, the future development strategy and prospect of MXene-based materials in high-energy-density LSBs are put forward.