High Sulfur Loading Research Articles

Surface-Phosphided Metal Oxide Microspheres as Catalytic Host of Sulfur to Enhance the Performance of Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are one of the most promising high-energy density secondary batteries due to their high theoretical energy density of 2600 Wh kg-1. However, the sluggish kinetics and severe "shuttle effect" of polysulfides are the well-known barriers that hinder their practical applications. A carefully designed catalytic host of sulfur may be an effective strategy that not only accelerates the conversion of polysulfides but also limit their dissolution to mitigate the "shuttle effect." Herein, in situ surface-phosphided Ni0.96Co0.03Mn0.01O (p-NCMO) oxide microspheres are prepared via gas-phase phosphidation as a catalytic host of sulfur. The as-prepared unique heterostructured microspheres, with enriched surface-coated metal phosphide, exhibit superior synergistic effect of catalytic conversion and absorption of the otherwise soluble intermediate polysulfides. Correspondingly, the sulfur cathode exhibits excellent electrochemical performance, including a high initial discharge capacity (1162 mAh gs-1 at 0.1C), long cycling stability (491 mAh gs-1 after 1000 cycles at 1C), and excellent rate performance (565 mAh gs-1 at 5C). Importantly, the newly prepared sulfur cathode shows a high areal capacity of 4.0 mAh cm-2 and long cycle stability under harsh conditions (high sulfur loading of 5.3 mg cm-2 and lean electrolyte/sulfur ratio of 5.8 μL mg-1). This work proposes an effective strategy to develop the catalytic hosts of sulfur for achieving high-performance Li-S batteries via surface phosphidation.

Preparation of three-dimensionally interconnected sulfur-deficient MoS2/nitrogen-doped carbon composite via salt template method for separator modification in lithium–Sulfur batteries

Separator modification is a promising strategy with regard to lithium–sulfur batteries for trapping polysulfides and suppressing the involved shuttle effect. Herein, a sulfur-deficient molybdenum disulfide/nitrogen-doped carbon composite with an open and interconnected structure (IMoS2-x) was synthesized through facile salt template method using recrystallized salt powder. Unlike the two-dimensional sheet structure obtained through conventional salt template method, an effective three-dimensional IMoS2-x composite design can be achieved using small salt powder as a template. The prepared IMoS2-x-coated polypropylene separator (referred to as IMoS2-x/PP) exhibited remarkable electrochemical performances such as high initial discharge capacity of 1405.1 mAh/g and rate capability of 754.16 mAh/g at 0.1 and 3C, respectively. Furthermore, IMoS2-x/PP exhibited robust cycling performance of 911.18 mAh/g after 80 cycles at 0.2C under high sulfur loading and lean electrolyte conditions, with the electrolyte-to-sulfur ratio (E/S ratio) of 7.5 μL mg−1.

Layered double Hydroxides-MXene heterointerfaces with abundant anion vacancies expediting sulfur redox kinetics for High‑Performance Lithium–Sulfur batteries

Lithium-sulfur batteries (LSBs) are increasingly seen as advanced battery systems of great promise, owing to their exceptional energy density and cost-effectiveness. Yet, designing efficient electrocatalysts that can both effectively mitigate the diffusion of soluble lithium polysulfides (LiPSs) and enhance redox kinetics still remains a significant challenge, particularly at high sulfur loadings and lean electrolyte conditions. In this work, we develop NiCo-layered double hydroxides (NiCo-LDHs) nanosheets featuring abundant oxygen vacancies (Vo), anchored on Ti3C2-MXene nanosheets (denoted as Vo-LDHs-MXenes), tailored specifically for high-performance LSBs. The heterointerfaces between MXenes and Vo-LDHs modify the electronic structure and enhance the catalytic activity of the LDHs and MXenes, yielding multifunctional synergistic effects. Our theoretical and electrochemical analyses indicate that the Vo-LDHs-MXenes heterostructures exhibit enhanced affinity for LiPSs and superior catalytic performances compared to individual LDHs. This improvement facilitates the efficient adsorption and conversion of LiPSs, as well as the nucleation and decomposition of Li2S. Consequently, the cell with the Vo-LDHs-MXenes modified separator delivers stable cycling performances with a high initial specific capacity of 938.9 mAh/g over 300cycles at 1.0C and good rate capabilities. Notably, it still achieves a high initial areal capacity of 6.09 mAh cm−2 under a high sulfur loading of 6.7 mg cm−2 and low electrolyte/sulfur (E/S) ratio of 6.0 μL mg−1 over 50cycles.

Electronic Spin Alignment within Homologous NiS2/NiSe2 Heterostructures to Promote Sulfur Redox Kinetics in Lithium-Sulfur Batteries.

The catalytic activation of the Li-S reaction is fundamental to maximize the capacity and stability of Li-S batteries (LSBs). Current research on Li-S catalysts mainly focuses on optimizing the energy levels to promote adsorption and catalytic conversion, while frequently overlooking the electronic spin state influence on charge transfer and orbital interactions. Here, hollow NiS2/NiSe2 heterostructures encapsulated in a nitrogen-doped carbon matrix (NiS2/NiSe2@NC) are synthesized and used as a catalytic additive in sulfur cathodes. The NiS2/NiSe2 heterostructure promotes the spin splitting of the 3d orbital, driving the Ni3+ transformation from low to high spin. This high spin configuration raises the electronic energy level and activates the electronic state. Thisaccelerates the charge transfer and optimizes the adsorption energy, lowering the reaction energy barrier of the polysulfidesconversion. Benefiting from these characteristics, LSBs based on NiS2/NiSe2@NC/S cathodes exhibit high initial capacity (1458 mAh·g⁻1 at 0.1C), excellent rate capability (572 mAh·g⁻1 at 5C), and stable cycling with an average capacity decay rate of only 0.025% per cycle at 1C during 500 cycles. Even at high sulfur loadings (6.2 mg·cm⁻2), high initial capacities of 1173 mAh·g⁻1 (7.27 mAh·cm⁻2) are measured at 0.1C, and 1058 mAh·g⁻1 is retained after 300 cycles.

Accelerated Sulfur Redox Kinetics on Transition Metal Sulfide Electrocatalysts by Modulating Electronic‐State of Active Sites

AbstractLithium‐sulfur (Li‐S) batteries are considered a competitive next‐generation electrochemical energy storage device, while the shuttle effect of soluble lithium polysulfides (LiPSs) resulting from the sluggish redox kinetics severely impedes their practical applications. Herein, a novel cation doping strategy is demonstrated for substantially accelerating the sulfur redox kinetics on the transition metal sulfide (TMS) electrocatalysts by partially substituting cobalt atoms with in situ dissolved Ni dopants (NixCo3‐xS4, 0<x≤1). Theoretical calculations revealed that the doping of Ni in the spinel Co3S4 phase enables the electronic‐state modulation of metal active sites by realizing the upshift of the d‐orbital center, thus leading to good chemical adsorption of intermediates and low redox conversion barriers between LiPSs and solid Li2S products. This is confirmed by in‐depth electrochemical dynamics and in situ Raman characterizations, in which the obtained Ni0.5Co2.5S4 with hierarchical nanosheet structure delivers the stronger chemical affinity of Li2S6 and higher precipitation/dissociation capacity of Li2S in comparison to monometallic cobalt sulfides. Benefiting from these outstanding attributes, the assembled Li‐S batteries by incorporating Ni0.5Co2.5S4 electrocatalysts into S@carbon nanotube cathode (S@Ni0.5Co2.5S4/CNT) exhibit a high specific capacity of 1189 mAh g−1 with excellent rate performance of 596 mAh g−1 at 5 C and long‐term cycling performance over 600 cycles with a capacity decay of 0.06% per cycle at 1 C. More importantly, an ultrahigh reversible areal capacity of 6.6 mAh cm−2 can be achieved for S@Ni0.5Co2.5S4/CNT cathode even with a high sulfur loading of 6.1 mg cm−2. This work demonstrates a new insight into designing TMS electrocatalysts toward rapid redox conversion kinetics in Li‐S batteries.

N doped carbon supported cobalt/tungsten nitride Mott−Schottky heterojunction as an efficient electrocatalyst to enhance adsorption and conversion of lithium polysulfides for high-performance lithium–sulfur batteries

Lithium–sulfur batteries (LSBs) suffer from the dissolution of lithium polysulfides (LiPSs) which leading to capacity degradation and poor cycling stability. Hence, weʼve developed the Co/W3N4@NC Mott–Schottky heterostructures with built in electric field (BIF) are prepared as catalyst model to generate a built-in electric field to enhance the electrocatalytic effect on sulfur electrochemistry. Theoretical and experimental results have jointly demonstrated that the redistribution of charge and the presence of a built-in electric field at the Co/W3N4@NC heterointerface can promote the redox reaction within lithium sulfur battery during the discharge and charge processes, respectively. Experimental tests have confirmed its outstanding reversibility, achieving a capacity of 793.2 mAh·g−1 over 500 cycles at 1 C. It also shows excellent cycling performance with only 0.05 % attenuation per cycle over 800 cycles at 2 C for LSBs. Furthermore, even with a high sulfur loading of 5.5 mg·cm−2, the S@ Co/W3N4@NC cathode maintains favorable sulfur-related electrochemistry and delivers a high areal capacity of 3.61 mAh·cm−2 as well as maintaining considerable stability. This synthetic Mott–Schottky heterostructure not only amplifies the electrocatalytic effect in LSBs, but also advances the design of catalysts for advanced high-energy-density batteries.

Nano‐Scale Interface Engineering of Sulfur Cathode to Enable High‐Performance All‐Solid‐State Li–S Batteries

AbstractAll‐solid‐state lithium–sulfur batteries (ASSLSBs) are expected to be the next generation of high‐energy battery systems due to their long lifespan and high safety. However, unstable interfaces between elemental sulfur, conductive carbon, and solid electrolytes lead to slow charge transport and mechanical failures, thereby limiting battery performance. Herein, atomic layer deposition‐derived lithium phosphorus oxide is applied to the surface of carbon/sulfur particles to enhance the interfacial stability of the sulfur cathode and improve the electrochemical performance of ASSLSBs. The coating layer can inhibit electrolyte decomposition and improve interfacial stability by blocking electron conduction between carbon and electrolyte. Moreover, it not only serves as an ion‐conducting layer to facilitate Li+ transport but also acts as a stress buffer layer to alleviate contact failure. The assembled ASSLSBs with sulfide electrolyte exhibit an initial specific capacity of 1322 mAh g−1 at 0.2 C and capacity retention of 86.4% after 300 cycles. Furthermore, ASSLSBs maintain a reversible capacity of 645 mAh g−1 at 0.5 A g−1 after 1000 cycles, confirming the long cycling stability of the coated sulfur cathode. Even under high sulfur loading, ASSLSBs achieve high areal capacities of 4.6 mAh cm−2 at 30 °C and 11.7 mAh cm−2 at 60 °C.

In-situ constructing cathode protective film toward high performance of Li-S batteries at high sulfur loadings

Shuttle effect of lithium polysulfide (LiPSs) and low sulfur loadings encumber practical application of Li-S batteries. Sulfur cathode coating is a direct and effective strategy to alleviate the problem. However, it is difficult for the available ex-situ coating to suppress shuttle effect at high sulfur surface loading. In the present work, diphenylamine (DPA) is used as an electrolyte additive, which can undergo electropolymerization and form an in-situ PDPA film on sulfur cathode, thereby inhibiting LiPSs diffusion. More importantly, computations and experiments prove that DPA-LiPSs complexes are formed in the electrolyte, increasing the solubility of LiPSs and improving the conversion kinetics. Benefit from the above, the capacity of DPA battery reaches 1029.5 mAh g−1 with sulfur loading of 3 mg cm−2 at 1 C rate, and keeps 762.1 mAh g−1 after 1000 cycles. Excellent cycling performance is achieved even at a high sulfur loading of up to 7 mg cm−2. This work provides a new strategy for suppressing the LiPSs shuttle effect under high sulfur surface loadings.

Mxene quantum dots decorated reduced graphene oxide networks as multifunctional electrocatalyst for advanced lithium–sulfur batteries

Lithium sulfur (Li-S) battery has shown great potential as an attractive rechargeable energy storage devices, but the shuttle behavior and slow conversion kinetics of the intermediate lithium polysulfides (LiPSs) are the main obstacles to the practical application of Li-S battery. Herein, a simple and scalable spray drying strategy was used to construct conductive polar Ti3C2 MXene quantum dots (QDs)-decorated reduced graphene oxide (rGO) microsphere (rGO@Ti3C2 QDs) as efficient electrocatalyst and absorbent for Li-S battery. Firstly, the DFT results show that Ti3C2 QDs can effectively adsorb and catalyze LiPSs conversion. This ability can be attributed to the Ti3C2 QDs can provide a large number of LiPSs catalytic active sites. In addition, the rGO provides physical LiPSs constraint and a flexible substrate to prevent QDs from aggregating. Moreover, both parts are conductive, effectively improving the electron/charge transfer. Therefore, this unique structure and composition show high LiPSs adsorption and catalysis, while allowing rapid Li+/electron transfer. As a result, the S/rGO@Ti3C2 QDs electrode provides high initial capacity (1185 mAh/g at 0.2C), good rate capability (758 mAh/g at 3C), and excellent long-term cyclability (500 cycles at 1C with low attenuation of 0.07% per cycle), as well as an excellent electrochemical performance even at high sulfur loading. Meanwhile, the Li-S pouch cell based on S/rGO@Ti3C2 QDs also achieved a high initial energy density of 230.9 Wh kg−1. This work may provide a promising strategy to obtain better electrochemical performance by introducing quantum dots into Li-S cathodes.

Constructing honeycomb-structured LaCoO3 as an efficient polysulfide converter on the separator to achieve practical lithium-sulfur batteries

Owing to its remarkable energy density and specific capacity, lithium-sulfur (Li-S) battery has emerged as one of the most promising energy storage devices. Nevertheless, the shuttle effect and the sluggish conversion of polysulfides significantly impede the practical application of Li-S batteries. Hence, a LaCoO3 functional material with a unique honeycomb structure was designed as an efficient polysulfide converter. The honeycomb-structured LaCoO3 not only exhibits strong bonding energy towards polysulfides but also possesses abundant adsorption sites on its surface. The LaCoO3 material also shows excellent catalytic properties to quickly convert the adsorbed and aggregated polysulfides, effectively suppressing the shuttle effect. Moreover, the honeycomb structure of LaCoO3 can facilitate the rapid wetting and infiltration of the electrolyte. Consequently, the Li-S cell with LaCoO3 functionalized separator provides an areal specific capacity of 3.10 mAh cm−2 after 150 cycles under high sulfur loading of 6.52 mg cm−2. Moreover, under practical conditions where the electrolyte content is as low as 7 μL mg−1 and the sulfur loading is 7.96 mg cm−2, the Li-S battery equipped with LaCoO3-separator can still provide an areal specific capacity of 5.93 mAh cm−2 after 50 cycles.

Highly Conductive Quasi‐1D Hexagonal Chalcogenide Perovskite Sr8Ti7S21 with Efficient Polysulfide Regulation in Lithium‐Sulfur Batteries

AbstractLithium‐sulfur batteries (LSBs) are regarded as one of the most promising candidates for next‐generation energy storage systems. However, the commercialization of LSBs is still hindered by several technical issues, including the notorious polysulfide migration from the cathode to the anode and the sluggish sulfur conversion kinetics. Herein, a quasi‐1D hexagonal chalcogenide perovskite, Sr8Ti7S21, is demonstrated as an efficient sulfur host able to overcome these limitations. Experimental results and density functional theory calculations show Sr8Ti7S21 to offer strong lithium polysulfides (LiPS) binding through multiple bond formation. Besides, Sr8Ti7S21 effectively facilitates the kinetics of the LiPS redox reaction. As a result, S@Sr8Ti7S21‐based cathodes exhibit excellent initial capacities up to 1315 mAh g−1 at 0.2C, impressive cycling stability with an average capacity decay rate of 0.08% per cycle over 400 cycles at 1C, and a high areal capacity of 6.58 mAh cm−2 under a high sulfur loading of 6.5 mg cm−2. This work reveals the potential capabilities and promising prospects of chalcogenide perovskites in advancing LSBs technology.

Crystalline-amorphous heterostructure on the phosphatized P-CoS2/CNT for augmenting the catalytic conversion kinetics of Li-S batteries

Crystalline-amorphous heterostructure catalyst is employed to conquer the notorious shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) intermediates of lithium-sulfur (Li-S) batteries. Herein, crystalline-amorphous heterostructure on the phosphatized cobalt disulfide/carbon nanotube (designated as P-CoS2/CNT) are served as the functional interlayer for Li-S batteries. Crystalline-amorphous heterostructure of P-CoS2/CNT is composed of high crystalline CoS2 core and amorphous Co(PO3)2 (a-Co(PO3)2) shell along with abundant active Co-O-P bonds. The crystalline CoS2 core and grain boundary defects on the heterostructure can prop up the well-pleasing electron conductivity when a-Co(PO3)2 accelerates the catalytic conversion kinetics of the polysulfides through the comprehensive survey in terms of chemical anchoring capability, nucleation barrier for Li2S, In-situ Raman for monitoring the shuttle case of polysulfides, and the analysis of inactive sulfur species on Li anode. In consequence, the Li-S battery using the P-CoS2/CNT functional separator delivers an outstanding low-capacity decay of only 0.048 % per cycle for 1000 cycles at 2C, and the LiPSs's shuttle effect is efficaciously restrained. Even with a high sulfur loading of 3.6 mg cm−2, the cell still maintains an outstanding areal capacity of 1.75 mAh cm−2 after 200 cycles at 1C. This work develops a scalable crystalline-amorphous heterostructure strategy using the conventional heteroatom modulation in aspire of accurately guiding the high-efficiency electrocatalyst served for the Li-S electrochemistry.

Preparation and application of NiS2/NiSe2 heterostructure as a sulfur host in lithium-sulfur batteries

The introduction of heterostructure in the cathode material of Li-S battery is an effective method to improve the redox reaction kinetics and suppress the shuttle effect of polysulfide. A metal sulfide/metal selenide (NiS2/NiSe2) heterostructure with hollow tetrahedral structure is prepared as a sulfur host of lithium-sulfur batteries. The prepared NiS2/NiSe2 heterostructure exhibits efficient charge transfer at the heterojunction interface, thereby enhancing catalytic activity for redox reactions of polysulfides and facilitating their rapid conversion. Moreover, the unique hollow tetrahedral structure, along with abundant surface pores, enables high sulfur loading capacity, providing abundant electrochemical reaction sites to enhance sulfur utilization efficiency. The results demonstrate that the NiS2/NiSe2 heterostructure material exhibits a remarkable initial capacity of 1338.9 mAh/g at 0.2 C, along with exceptional cycling stability (maintaining a capacity of 517.6 mAh/g after 200 cycles at 0.2 C, with only a negligible decay rate of 0.3% per cycle, retaining a capacity of 462.6 mAh/g after 500 cycles at 1 C, with an insignificant decay rate of merely 0.12% per cycle). The facile preparation of this NiS2/NiSe2 heterostructure not only enables the realization of lithium-sulfur batteries with exceptional capacity, but also opens up broader avenues for exploring high-performance heterogeneous materials.

A Critical Review on Room-Temperature Sodium-Sulfur Batteries: From Research Advances to Practical Perspectives.

Room-temperature sodium-sulfur (RT-Na/S) batteries are promising alternatives for next-generation energy storage systems with high energy density and high power density. However, some notorious issues are hampering the practical application of RT-Na/S batteries. Besides, the working mechanism of RT-Na/S batteries under practical conditions such as high sulfur loading, lean electrolyte, and low capacity ratio between the negative and positive electrode (N/P ratio), is of essential importance for practical applications, yet the significance of these parameters has long been disregarded. Herein, it is comprehensively reviewed recent advances on Na metal anode, S cathode, electrolyte, and separator engineering for RT-Na/S batteries. The discrepancies between laboratory research and practical conditions are elaborately discussed, endeavors toward practical applications are highlighted, and suggestions for the practical values of the crucial parameters are rationally proposed. Furthermore, an empirical equation to estimate the actual energy density of RT-Na/S pouch cells under practical conditions is rationally proposed for the first time, making it possible to evaluate the gravimetric energy density of the cells under practical conditions. This review aims to reemphasize the vital importance of the crucial parameters for RT-Na/S batteries to bridge the gaps between laboratory research and practical applications.

Modified electron structure of CNT-CoSe2 (vs. CoSe2) with more Co2+ for improving catalytic effect in lithium sulfur batteries

Currently, the great challenge of lithium sulfur (Li-S) batteries is the sluggish redox kinetics and the ineludible shuttle effect, which induce the rapid capacity fading. Regulating the electron structure of metal-based catalysts is regarded as a significant strategy to improve the catalytic effect of Li-S batteries, for accelerating the redox kinetics and enhancing the cathode performance. In this work, the valence of Co in CoSe2 is regulated by introducing carbon nanotube (CNT) during the preparation of ZIF-67. Compared with CoSe2, the ratio of Co2+/Co3+ increases, which boost the catalytic activity of CNT-CoSe2 both in discharging and charging process. Furthermore, the ratio of Co2+/Co3+ is reduced after discharging due to the electron transfer to sulfur species, and the ratio is increased again due to the inverse electron transfer. As a result, the CNT-CoSe2 with better catalytic properties endows the corresponding Li-S batteries more stable cycling performance, especially at high current density or high sulfur loading. The CNT-CoSe2 modified separator can endow Li-S batteries with a discharge capacity of 735.49 mAh g−1 at 2 C, and a retention ratio of 72.28% for 200 cycles at 0.1 C with sulfur loading of 4.60 mg cm−2.

Electronic redistribution and fast delivery enabled by Co0.5Ni0.5Te2 grafting 3D MXene heterostructure for accelerating High-Durability sulfur redox kinetics

Lithium-sulfur (Li-S) batteries are regarded as the most commercially viable energy storage system, but the severe shuttling behavior and sluggish reaction kinetics hinder cycling stability and lifespan. Herein, a brand-new catalytic 3D Co0.5Ni0.5Te2/MXene heterostructure is constructed by uniformly grafting bimetallic telluride nanoparticles onto the MXene nanosheets, inhibiting the restacking of MXene nanosheets. Noticeably, bimetallic elements (Ni/Co) are crosslinking agents that synergistically fulfil and regulate 3D macroporous structure, thus enriching sulfophilic and lithiophilic interactions. The generated 3D porous Co0.5Ni0.5Te2/MXene heterostructure exhibits abundant polar active sites, enhances the chemical adsorption of polysulfides, reduces the transform energy barrier of redox reactions, and provides an accelerated pump for rapid Li+ diffusion at hetero-interface, as sufficient studied by performance analysis, theoretical calculations, and in-situ Raman. Resultantly, the Co0.5Ni0.5Te2/MXene-based batteries exhibit excellent cyclability with a minimum decay ratio of 0.0227 % per cycle during 500 cycles at 1 C, realizing an appealing areal capacity of 8.46 mAh cm−2 even with a high sulfur loading (9.21 mg cm−2) and a lean electrolyte/sulfur ratio (E/S = 6.2 µL mg−1). This work provides an elaborate designed strategy and mechanism insights for simultaneously blocking polysulfides shuttling and enhancing conversion kinetics in Li–S batteries.

Interfacial synergy of nanoengineered PANI/MnO2 for strong anchoring and fast conversion of polysulfides in Li-S batteries

The shuttle of polysulfides and slow sulfur redox kinetics are the two main issues in the practical application of lithium sulfur (Li-S) batteries. The interface-induced electric fields produced in MnO2-based conductive composites are proposed to solve the above obstacles. Herein, a novel hybrid structure of birnessite-MnO2 nanosheets in situ formed inside polyaniline nanotubes (NSs-MnO2@PANI) is prepared and applied as a catalytic host in Li-S batteries. The DFT calculation combined with experiments reveal the interface-induced electric field with a direction pointing from PANI to birnessite-MnO2 is created, which would induce interface charge redistribution and result in electron-rich MnO2 region and electron-deficient PANI region, optimizing the strong anchoring of polysulfides and their fast catalytic conversions. Owing to the interfacial synergy, the NSs-MnO2@PANI/S cathode delivers higher capacity than PANI/S at rates from 0.1 C (1473.7 vs. 467.5 mAh g−1) to 5 C (513.2 vs. 38.1 mAh g−1), with a low decay rate of 0.054% during 500 cycles at 0.2 C. Further, at an extremely high sulfur loading of 15.9 mg cm−2, the areal capacity achieves a high level of 10.2 mAh cm−2 at 0.05 C, with stable cycling at 1 C. Our work provides new insights for attaining high-energy and stable Li-S batteries.

Interfacial "Double-Terminal Binding Sites" Catalysts Synergistically Boosting the Electrocatalytic Li2S Redox for Durable Lithium-Sulfur Batteries.

Catalytic conversion of polysulfides emerges as a promising approach to improve the kinetics and mitigate polysulfide shuttling in lithium-sulfur (Li-S) batteries, especially under conditions of high sulfur loading and lean electrolyte. Herein, we present a separator architecture that incorporates double-terminal binding (DTB) sites within a nitrogen-doped carbon framework, consisting of polar Co0.85Se and Co clusters (Co/Co0.85Se@NC), to enhance the durability of Li-S batteries. The uniformly dispersed clusters of polar Co0.85Se and Co offer abundant active sites for lithium polysulfides (LiPSs), enabling efficient LiPS conversion while also serving as anchors through a combination of chemical interactions. Density functional theory calculations, along with in situ Raman and X-ray diffraction characterizations, reveal that the DTB effect strengthens the binding energy to polysulfides and lowers the energy barriers of polysulfide redox reactions. Li-S batteries utilizing the Co/Co0.85Se@NC-modified separator demonstrate exceptional cycling stability (0.042% per cycle over 1000 cycles at 2 C) and rate capability (849 mAh g-1 at 3 C), as well as deliver an impressive areal capacity of 10.0 mAh cm-2 even in challenging conditions with a high sulfur loading (10.7 mg cm-2) and lean electrolyte environments (5.8 μL mg-1). The DTB site strategy offers valuable insights into the development of high-performance Li-S batteries.

Decoration on the inner surface of low-tortuosity microchannels derived from wood plate for highly stable lithium sulfur batteries

The low-tortuosity microchannels of wood-based carbon matrix in free-standing cathodes for lithium sulfur batteries (LSBs) were a double-edged sword, which brought in both a high energy density due to a high sulfur loading and severe shuttle effect for poor cycling stability. Herein, a layer of cellulose aerogel extracted from the wood wall was coated on the inner surface of the low-tortuosity microchannels of the wood plate, which was further transformed into a hierarchical carbon matrix using in free-standing cathode for LSBs. The decorated cathode exhibited a maximal specific capacity of 1377.2 mAh g−1 due to the enhanced utilizing ratio of active materials and exceptional cycling stability even under a high current density (1 C) for more than 500 cycles. Furthermore, the decorated cathode maintained good cycling stability with a higher sulfur areal loading (6.3 mg cm−2). The cellulose-based carbon aerogel coated on the inner surface of low-tortuosity microchannels provided a large specific surface area. This decoration strategy not only provided physical restriction on polysulfides but also increased conversion sites for polysulfides, improving the cycling performance of the wood-based free-standing cathode of LSBs. This work provided a potential structural design strategy for the advanced free-standing cathode of LSBs.

Using the fermi level as a predictive indicator of the electrocatalytic activities displayed by single-atom catalysts in sulfur cathode reactions

Single-atom catalysts (SACs) have emerged as promising candidates for promoting sulfur cathode kinetics. Despite the growing popularity, the literature is devoid of general guidelines for predicting the electrocatalytic effects exerted by novel SACs. Herein, a series of SACs immobilized on N-doped graphene were prepared from metal (Mn, Ni, Cu, or Zn) porphyrins. The Fermi levels of the catalysts were found to be inversely correlated with their electrocatalytic effects. For example, the Ni-based SACs exhibited the lowest Fermi level but showed the strongest binding affinity to sulfur. As a result, Li−S cells containing Ni SACs exhibited a high specific capacity (10.0 mA h cm−2 at 0.05 C), excellent cycling stability (6.7 mA h cm−2 at 0.1 C after 100 cycles) and other remarkable performance metrics even at a high sulfur loading of 9.6 mg cm−2. The methodology offers a way to evaluate the catalytic activities of SACs rapidly and efficiently, particularly in electrocatalytic systems.