High Energy Density Lithium-sulfur Batteries Research Articles

Effective Lithium Polysulfides Anchoring on Vanadium Disulfide Facets for Lithium-Sulfur Batteries – A Computational Study

The commercialization of Li-S batteries is hindered by the shuttle effects of lithium polysulfides (LiPS) and the sluggish reaction kinetics. Hence, effectively trapping and promoting the conversion rates of LiPSs is of prime importance1. However, the fundamental kinetics of the electrocatalytic charging and discharging of Li-S batteries and the underlying mechanism have not been sufficiently explored yet.2 Therefore, by taking the 2D transition metal sulfide, VS2 as a model, we conducted a systematic investigation using density functional theory to study the ability of dominant exposed crystal planes of VS2 to trap LiPSs from leaching into electrolyte solvents and to act as an electrocatalyst to increase the Sulfur Reduction Reaction (SRR) kinetics3. To reflect a realistic environment of a battery, the effect of electrolyte solvents on the electrocatalytic activity was further investigated. Our calculations show that VS2 has moderate binding energy toward LiPSs which inhibits LiPS from leaching into electrolytes while fulfilling the key prerequisite to act as an electrocatalyst simultaneously.4 At the discharge, the conversion of S8 to the long chain Li2S8 was facile with a lower energy barrier while the rest of the reactions were sluggish explaining the accumulation of LiPSs. Further, the VS2 (001) facet exhibits excellent electrocatalytic activity for the SRR and Li2S decomposition reaction at charging compared to other dominant crystal planes, which significantly lowers the energy barriers of LiPS conversion during the charging and discharging process, ensuring high-rate performance and longer cycle life4. References Manthiram, A., Fu, Y., Chung, S.-H., Zu, C., & Su, Y.-S. (2014). Rechargeable Lithium–Sulfur Batteries. Chemical Reviews, 114(23), 11751–11787.Abraham, A. M., Thiel, K., Shakouri, M., Xiao, Q., Paterson, A., Schwenzel, J., Ponnurangam, S., & Thangadurai, V. (2022). Ultrahigh Sulfur Loading Tolerant Cathode Architecture with Extended Cycle Life for High Energy Density Lithium–Sulfur Batteries. Advanced Energy Materials, 2201494.Abraham, A. M., Boteju, T., Ponnurangam, S., & Thangadurai, V. (2022). A global design principle for polysulfide electrocatalysis in lithium–sulfur batteries—A computational perspective. Battery Energy, 20220003.Boteju, T., Abraham, A. M., Ponnurangam, S., & Thangadurai, V. (2023). Theoretical Study on the Role of Solvents in Lithium Polysulfide Anchoring on Vanadium Disulfide Facets for Lithium–Sulfur Batteries. The Journal of Physical Chemistry C.

Interplay of Interphases in Lithium-Sulfur Cells

Lyten’s revolutionary 3D Graphene is enabling the transition to a greener future through its high energy density lithium-sulfur (Li-S) batteries. As with all battery chemistries, the electrolyte-electrode interphases formed in-situ during cell cycling not only regulate the redox processes but also strongly dictate the cycle life of the cells.In this talk, we will describe the different interphases formed on the cathode and anode of a Li-S battery and their importance. A glimpse into how regulating these interphases using different additives affects the cycle life of cells will also be demonstrated.

MXene-Bimetallic Hybrids via Mixed Molten Salts Etching for Kinetics-Enhanced and Dendrite-Free Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries with high theoretical energy density (2600Whkg-1) are considered to be one of the most promising secondary batteries. However, the practical application of Li-S batteries is limited by the polysulfides shuttling and unstable lithium metal anodes. Herein, an asymmetric separator (CACNM@PP), composed of Co-Ni/MXene (CNM) on the cathode and Cu-Ag/MXene (CAM) on the anode for high-performance Li-S batteries is reported. For the cathode, CNM provides a synergistic effect by integrating Co, Ni, and MXene, resulting in strong chemical interactions and fast conversion kinetics for polysulfides. For the anode, CAM with abundant lithiophilicity active sites can lower the nucleation barrier of Li. Moreover, LiCl/LiF layers are generated in situ as an ion conductor layer during charging and discharging, inducing a uniform deposition of Li. Therefore, the assembled cells with the CACNM@PP separators harvest excellent electrochemical performance. This work provides novel insights into the development of commercially available high-energy density Li-S batteries with asymmetric separators.

Defect engineering enables an advanced separator modification for high-performance lithium-sulfur batteries

High-energy–density lithium-sulfur batteries have been rated as a promising, yet challenging, next-generation battery technology. Typically, the serious shuttle of polysulfide intermediates and sluggish solid–solid reaction kinetics often result in irreversibly sulfur loss, low Coulombic efficiency, and limited lifespan. Herein, we propose a facile and efficient separator modification strategy using a rationally designed sulfiphilic and lithiophilic mediator, i.e. in-situ confinement growth of oxygen-deficient TiO2-x nanoparticles within nitrogen-doped mesoporous carbon matrix to modulate the sulfur electrochemistry. The nanoscale defective catalyst within open mesoporous host affords favorable adsorption of polysulfides and catalytic conversion ability. Moreover, the versatile composite improves the electrolyte wettability and Li+ transfer kinetics and alleviates self-discharge behavior. Resultantly, the Li-S batteries using modified separator achieves significantly improved cycling stability with a low capacity decay of only 0.067% per cycle after 500 cycles at 2C. The defect engineering together with separator modification strategies enable efficient and durable Li-S batteries.

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.

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.

Enabling fast diffusion/conversion kinetics by thiourea-induced wrinkled N, S co-doped functional MXene for lithium-sulfur battery

The long lifespan of high-energy density lithium-sulfur batteries (LSBs) is still hindered by severe polysulfide (PS) shuttling and sluggish sulfur reduction/evolution kinetics process. Herein, we report a facile preparation of thiourea-induced wrinkled nitrogen and sulfur co-doped functionalized MXene (NSMX) to modify the separator to enhance the ion diffusion and conversion kinetics for high-energy LSBs. The combination of theoretical calculations and experimental conclusions demonstrates that the introduction of N, S heteroatoms induces the shift of the d-band center in transition metal Ti towards the Fermi level and results in the robust bonding effect between N/S atoms and Li atom in PS, hence exhibiting admirable adsorption capability to PS and fast catalytic PS reversible conversion rate, which quickly deplete soluble high-order PS and expedites the depletion of the Li2S6 in high potential. The 2D wrinkled polar surface with excellent conductivity assures fast electron transfer and ion migration. Profiting from the enhancement of S utilization and the reduction of unfavorable accumulated Li2S6, the LSBs equipped with NSMX modified separators exhibit a high specific capacity of 1249 mAh g−1 at 0.2 C. At a high rate of 5 C, the LSBs also delivered an impressive reversible capacity of 600 mAh g−1. Moreover, a high capacity and stable cycling can be achieved even under the condition of high S load and lean electrolyte consumption.

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

Remarkable chemical adsorption and catalysis of monodisperse metallic cobalt sulfide nanoparticles enable long-cycling Li–S battery with high areal capacity and low shuttle constant

High-energy density lithium-sulfur battery is considered as one of the most potential new-generation energy-storage technologies. Nevertheless, the capacity decays rapidly due to severe volumetric change of sulfur, dissolution and slow redox kinetics of intermediate polysulfides, and instability of lithium anode. Herein, a novel highly conductive porous sulfur cathode host composed of graphene aerogel and polar Co9S8 nanoparticle is designed to address these obstacles. The porous conductive framework not only provides channels for rapid conduction of electron and lithium ion, but also provides adequate space to physically confine the lithium polysulfides and accommodate the volume expansion. Both experimental and theoretical calculations demonstrate that the in-situ uniformly deposited Co9S8 nanoparticles can effectively bind polar lithium polysulfides and catalyze their interconversion, and the shuttle effect is therefore effectively suppressed. The Co9S8-GA/S cathode exhibits high specific discharge capacity (1219.1 mAh g−1) and high areal specific capacity (14.3 mAh m−2) at 0.1 C, low shuttle constant (0.15 h−1), excellent rate performance (625.6 mAh g−1/7.4 mAh m−2 at 5 C), outstanding long cyclic stability (low decay of 0.024 %/cycle during 1000 cycles at 2 C). This study demonstrates a promising aerogel strategy to design high-performance composite cathode for lithium-sulfur battery.

Flame-retardant ammonium polyphosphate/MXene decorated carbon foam materials as polysulfide traps for fire-safe and stable lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are one of the most promising modern-day energy supply systems because of their high theoretical energy density and low cost. However, the development of high-energy density Li-S batteries with high loading of flammable sulfur faces the challenges of electrochemical performance degradation owing to the shuttle effect and safety issues related to fire or explosion accidents. In this work, we report a three-dimensional (3D) conductive nitrogen-doped carbon foam supported electrostatic self-assembled MXene-ammonium polyphosphate (NCF-MXene-APP) layer as a heat-resistant, thermally-insulated, flame-retardant, and freestanding host for Li-S batteries with a facile and cost-effective synthesis method. Consequently, through the use of NCF-MXene-APP hosts that strongly anchor polysulfides, the Li-S batteries demonstrate outstanding electrochemical properties, including a high initial discharge capacity of 1191.6 mA h g−1, excellent rate capacity of 755.0 mA h g−1 at 1 C, and long-term cycling stability with an extremely low-capacity decay rate of 0.12% per cycle at 2 C. More importantly, these batteries can continue to operate reliably under high temperature or flame attack conditions. Thus, this study provides valuable insights into the design of safe high-performance Li-S batteries.

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.

Magneli Ti4O7 nanotube arrays as a free-standing efficient interlayer for fast-delivery and high-energy density lithium-sulfur batteries

Improving lithium sulfur (Li-S) batteries performance has been a challenge due to sulfur drawbacks. Here, it addresses the use of Magneli Ti4O7 nano-tube arrays (MTNTAs) as free-standing interlayer in conjunction with carbon-coated separator (CCS) to improve the performance of lithium-sulfur batteries. The electrochemical catalytic activity of MTNTAs showed stable cycling and outstanding rate performance. The battery equipped with MTNTAs, and CCS delivered 723 mAh.g−1 with a low capacity-fading rate of 0.07% per cycle at 0.5 C after 500 cycles. The remarkably fast Li ion diffusion and low internal resistance of MTNTAs provided a discharge capacity of 407 mAh.g−1 after 500 cycles at 10 C. The high-sulfur loaded cathode (6.7 mg S. cm−2) can offer a discharge capacity of 719 mAh.g−1 at 0.1 C corresponding to areal capacity of 4.8 mAh.cm−2. The outperformance of the cell became drastically attractive when the cathode was fabricated with the simple blade-casting method using pure sulfur. The sulfur cathode delivered a superior discharge capacity of 471 mAh.g−1 after 250 cycles with coulombic efficiency> 95% at 0.2 C. The result of this study demonstrates that the coexistence of MTNTAs and CCS in the battery can offer a long-life cycle with outstanding properties such as fast charging and discharging, and high-energy density which is highly desirable for transportation sectors.

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.

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.

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.