Advances in the Development of Single-Atom Catalysts for High-Energy-Density Lithium-Sulfur Batteries

Encapsulation of FeS2 within N/S-Doped bamboo-like carbon nanotubes for facilitated rapid catalytic conversion of polysulfides in high-performance lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are considered to be competitive next-generation electrochemical energy storage devices, but their practical application is severely hampered by the shuttle effect and slow redox kinetics of soluble lithium polysulfides (LiPSs). To address this challenge, FeS2 encapsulated within N/S co-doped bamboo-like carbon nanotubes (FeS2/NSC) is synthesized via a pyrolysis sulfidation process, and act as a coating separator for LSBs. The 1-dimensional (1D) S and N co-doped carbon substrate materials can act as conductive networks, exposing more adsorption sites and enhancing the capture of LiPSs. Furthermore, the FeS2 can realize the fast catalytic transformation of LiPSs. The results show that batteries with FeS2/NSC separators exhibit excellent cycling stability (790.8 mAh g-1 after 500 cycles at 0.5 C) and rate performance (1056.5 mAh g-1 at 2 C). Meanwhile, a significant area capacity of 8.2 mAh cm-2 is shown when the S loading is 9.1 mg cm-2. Most importantly, the battery with FeS2/NSC separator demonstrates excellent performance over a wide temperature range (0 °C and 60 °C), maintaining 92.8%/76.3% capacity retention after 100 cycles, respectively. Hence, this research offers significant contributions to the understanding of transition metal sulfides and their potential for enhancing the performance of LSBs.

Advances in Catalytic Host Cathodes for Aqueous Metal (Zn, Cu, Fe)-Ion Batteries

Aqueous batteries with conversion mechanisms show promise for large-scale energy storage due to the inherent safety, cost-effectiveness, high energy density, and eco-friendly advantages. However, redox species migration and sluggish kinetics critically impede the further development of aqueous-conversion batteries. The integration of catalytically active sites into host cathode materials has been proposed as an effective solution to these challenges, with notable advancements in research. This review systematically summarizes recent advances in catalytic host materials for aqueous metal-ion batteries (zinc-iodine, zinc-bromide, zinc-sulfur, zinc-selenium, zinc-tellurium, copper-sulfur, and iron-iodine), analyzing their catalytic mechanisms and conversion processes. Meanwhile, this review identifies current research limitations while proposing targeted strategies to overcome the challenges. This work deepens the understanding of aqueous metal (Zn, Cu, and Fe)-ion batteries and guides the rational design of advanced energy storage technologies.

Emerging heterostructures derived from metal-organic frameworks for electrochemical energy storage: Progresses and perspectives

Heterostructures are a novel class of advanced materials have attracted considerable attention because they combine components with different structures and properties, exhibiting unique activity and function due to synergistic interactions at the interface. Over the last decade, there has been increasing research interest in constructing advanced heterostructures nanomaterials possessing efficient charge/ion transportation, optimize ion absorption behavior and rich accessible active sites for electrochemical energy storage (EES). Nonetheless, the conventional methodology for constructing heterostructures typically involves the self-assembly of active materials and conductive components, which poses significant challenges in achieving large-scale, uniformly atomically matched interfaces. Moreover, the development of heterostructures via transformation of the printine material into distinct phases can effectively address this limitation. Based on this, Metal-organic frameworks (MOFs), a class of porous materials with an inherently large surface area, uniform and adjustable cavities, and customizable chemical properties, have been widely used as precursors or templates for the preparation of heterostructure materials. Although there are some previous reviews on MOF-derived heterostructures for EES, they rarely focus on the structural engineering of MOF-derived heterostructures materials and their advanced characterization for EES. In this review, we summarize and discuss recent progress in the design and structural engineering (including morphology engineering, heteroatom doping, and defect engineering) of MOF-derived heterostructures and their applications in EES (e.g., supercapacitors, lithium-ion batteries, sodium-ion batteries, aluminum-ion batteries, aqueous Zn-ion batteries, etc.). The review concludes with a perspective on the remaining challenges and potential opportunities for future research.

Bioinspired Protein-Mineralized Single-Atom Nanozymes for Tumor-Specific Cascade Therapy via Self-Amplifying Catalytic Synergy

Single-atom catalysts (SACs) are highly promising in biomedical applications due to their unmatched catalytic activity and atomic-level precision, yet their clinical translation is hindered by limited biocompatibility, instability, and lack of tumor targeting. Here, a universal, bioinspired strategy is proposed to construct flexible, biocompatible SACs by leveraging enzymatic protein scaffolds for mineralization of single-atom platinum (Pt). This protein-mineralized platform enables the fabrication of stable dual-functional nanozymes, exemplified by glucose oxidase-coordinated Pt (GOx-Pt), which simultaneously catalyze glucose oxidation and H₂O₂-to-•OH conversion, generating a self-amplifying cascade for reactive oxygen species (ROS) production. To ensure tumor specificity, the GOx-Pt nanozyme is encapsulated within a pH-responsive zeolitic imidazolate framework (ZIF-8), which remains stable under physiological conditions but disintegrates in mildly acidic tumor environments, enabling localized and selective therapeutic activation. This synergistic design not only enhances antitumor efficacy by inducing oxidative stress and glucose depletion but also minimizes systemic toxicity. The resulting ZIF-8@GOx-Pt system achieves robust catalytic stability, selective cytotoxicity, and significant tumor inhibition (53%) in vivo without discernible side effects. This work pioneers a versatile biomineralization approach for engineering SAC-based nanozymes with dual catalytic and tumor-responsive functions, offering a generalizable strategy for next-generation precision cancer therapeutics.

Supramolecularly Confined Catalysis in Polyphthalocyanine-Crown-Ether Frameworks Boosts Sulfur Redox Kinetics

Metal phthalocyanines are considered as potent catalysts in lithium-sulfur (Li-S) chemistry. However, their adsorption capability is deficient to inhibit polysulfides from shuttling, which in turn retards the S-redox reaction in the cathode. Here we report flexible, two-dimensional (2D) polyphthalocyanine-crown-ether (PPc-CE) frameworks that provide a supramolecularly confined space created with the single-atom catalytic nickel phthalocyanine nodes and crown-ether linkers as Li host. Electrochemical and theoretical analyses reveal that a cooperative redox catalysis with the enhanced lithiophilicity of PPc-CE-coated carbon nanotubes (PPc-CE/CNTs) boosts Li-S redox kinetics and, meanwhile, suppresses the growth of Li dendrites for the long term. A Li||S cell employing PPc-CE/CNT catalysts delivers a high discharge capacity of 1,363 mAh g-1 at 0.1C and still retains a specific capacity of ∼700 mAh g-1 over 500 cycles at 1C. Our work provides insights into the molecular design of redox catalysts for Li-S batteries based on 2D polymers.

Bifunctional NiCoP nanofiber arrayed on carbon cloth for fast polysulfide conversion and uniform lithium deposition in lithium sulfur batteries

The severe polysulfides shuttling and irregular lithium dendrites impede the widespread adoption of lithium-sulfur (Li-S) batteries. Here, a sulfiphilic/lithiophilic NiCoP nanofiber arrayed on carbon cloth (NiCoP@CC) as the sulfur/lithium host is reported, providing a dual solution for both cathode and anode issues. Both theoretical calculations and experiments confirm that NiCoP@CC enhances the cycling stability of sulfur cathode and lithium anode by facilitating polysulfides conversion and homogenizing lithium deposition. Additionally, the unique structure of NiCoP nanofiber-decorated carbon cloth provides ample space to accommodate active materials and ensures even distribution of sulfur and lithium. Consequently, Li-S half cells containing NiCoP@CC exhibit an outstanding cycling life of 900 cycles at 1 C. Moreover, the Li@NiCoP@CC electrode achieves a stable, long cycling performance for 3000 h at 1 mA cm-2. Notably, Li-S full cells show enhanced cycling performance, maintaining stability over 750 cycles with a decay rate of 0.04 % per cycle at 1 C and a low N/P (negative/positive capacity) ratio of 2.4. A high areal capacity of 7.75mAh cm-2 is obtained at a high sulfur loading of 8.6 mg cm-2. This study presents a new strategy for designing bimetallic phosphides as bifunctional materials to overcome difficulties in practical Li-S batteries.

Design Strategies Based on Electronic Interactions for Effective Catalysts in Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are considered promising next-generation batteries due to their high energy density (>500 W h kg-1). However, LSBs exhibit an unsatisfactory energy density (<400 W h kg-1) and cycle life (<300 cycles) because of the shuttle effect caused by soluble lithium polysulfide (LiPS) intermediates and the sluggish conversion reaction kinetics caused by insulating sulfur (S8) and lithium sulfide (Li2S). Although various types of catalysts, including metal-based compounds to single-atom catalysts, have been reported to address these issues, most catalysts exhibited limited catalytic activity under practical lean electrolyte conditions (<5 µL mg-1). A comprehensive understanding of the synthetic strategy and catalytic mechanism of catalysts is essential for their design, but understanding the electronic effects of the catalysts and LiPS is more important. Furthermore, the electronic design of these catalysts is not well understood. In this review, we introduce the catalytic mechanisms in LSBs and discuss catalyst design strategies in terms of electronic effects on the interactions between reactants and catalysts, with a primary focus on heterogeneous catalytic systems. We additionally consider how the electronic property of homogeneous systems, particularly redox mediators, affects catalytic behavior under lean electrolyte conditions and propose future research directions for catalyst development in LSBs.

Advanced Electrolyte Additives for Enhanced Homogeneous Sulfur Fixation in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are regarded as leading contenders for next-generation energy storage owing to their exceptional theoretical energy density. However, severe sulfur electrode depletion causes rapid capacity fading and compromised cycling stability. Electrolyte engineering effectively enables homogeneous sulfur fixation, improving battery performance. The study investigates the mechanisms behind these homogeneous reactions, focusing on sulfur fixation processes. Sulfur fixation is explored through multiple perspectives, including the inhibition of polysulfide shuttling, mitigation of electrode passivation, and the combined application of both strategies. Regarding polysulfide shuttling inhibition, three distinct mechanisms for sulfur fixation are identified: 1) chemisorption-based sulfur fixation, involving the formation of chemical bonds with polysulfides; 2) redox-mediated sulfur fixation, which accelerates the kinetics of sulfur species; and 3) hybrid sulfur fixation, which combines elements of both approaches. Furthermore, the review analyzes current methods for homogeneous sulfur fixation, focusing on electrolyte designs that enable homogeneous sulfur fixation under limited conditions. It provides insights to optimize electrolytes, advancing Li-S battery performance and commercialization.

High-Entropy Oxide Heterostructure-Boosted Bidirectional Electrocatalysis in Lithium-Sulfur Batteries

Despite the advantageous features of high theoretical specific capacity (1675 mA h g-1) and low production costs, lithium-sulfur batteries have faced obstacles in achieving commercial fabrication, primarily due to sluggish reaction kinetics and the challenging shuttle effect. To address these issues, a novel high-entropy heterojunction interlayer, HEO@CC, was developed, which controllably grew homogeneous FeCoNiOx-MnCrOx (HEO) heterojunction particles onto carbon cloth. Consequently, HEO@CC generates multimetal active sites and a structure with low intrinsic resistance, enhancing the polysulfide anchoring capacity, accelerating the redox kinetics of Li2S, and physically impeding polysulfide shuttling. As analyzed by differential radial transmission (DRT) techniques, HEO@CC facilitates rapid anchoring ability and conversion capability of soluble polysulfides. This integration leads to a reduction in charge transfer impedance, improves sulfur utilization, and enhances Li+ diffusion. During the rate capability tests, the HEO@CC battery exhibited a substantial capacity retention of 622.79 mA h g-1 even after 500 cycles, demonstrating an average weekly capacity decay rate of only 0.029%. This research introduces innovative perspectives on the design of high-entropy heterostructured bidirectional catalytic interlayers and their catalytic mechanism, promoting the progress of high-capacity energy storage technologies.

Unsaturation degree of Fe single atom site manipulates polysulfide behavior in sodium-sulfur batteries

Sodium | |sulfur batteries hold great promise for grid-scale energy storage, yet their performance is hindered by the shuttling and sluggish redox of sulfur species. Herein, we report a strategic design of sulfur hosts modified with coordinatively unsaturated iron single-atom (Fe‒Nx) for sodium | |sulfur batteries. Utilizing theoretical calculations, geometric descriptor γ (lNa‒S/lFe‒N) and electronic descriptor φ (eg /t2g) simultaneously correlated with the unsaturation degree of Fe‒Nx site are proposed. A negative correlation between γ and the adsorption strength of sodium polysulfides, along with a positive correlation between φ and the decomposition capability of Na2S are established. The Fe‒N1 sites, with the minimum γ and maximum φ values, are identified as the optimal functional species for optimizing polysulfides behaviors. Sodium | |sulfur batteries utilizing Fe‒N1 /S positive electrodes deliver improved sulfur utilization (81.4% at 167.5 mA g‒1), sustained rate performance (1003.0 mAh g‒1 at 1675 mA g‒1), and stable cycling (83.5% retention over 450 cycles at 3350 mA g‒1). Moreover, Fe‒N1/S positive electrodes enable sodium | |sulfur pouch cells to deliver a sulfur utilization of 77.4% (1296.9 mAh g‒1) at 0.1 A g‒1. Our work offers a strategy for designing high-activity, fast redox sulfur positive electrodes and validates the practical potential of sodium | |sulfur batteries.

Anti-Self-Discharge Capability of Zn-Halogen Batteries Through an Entrapment-Adsorption-Catalysis Strategy Built Upon Separator

Aqueous Zn-halogen batteries (Zn-I2/Br2) suffer from grievous self-discharge behavior, resulting in irreversible loss of active cathode material and severe corrosion of zinc anode, which ultimately leads to rapid battery failure. Herein, an entrapment-adsorption-catalysis strategy is reported, leveraging Zn─Mn atom pairs-modified glass fiber separator (designated as ZnMn-NC/GF), to effectively mitigate the self-discharge phenomenon. The in situ Raman and UV experiments, along with theoretical calculations, confirmed the single-atom Mn sites are responsible for polyiodides adsorption, while Zn─Mn atom pairs facilitated the conversion of reaction intermediates. As a result, the utilization rate of cathode active species is enhanced through this ZnMn-NC/GF separator. The fully charged Zn-I2 battery assembled with ZnMn-NC/GF maintained a Coulombic efficiency (CE) of 90.1% after being left for 120 h, as well as a capacity retention rate of 95.3% after 30000 cycles at a current density of 5 A g-1. Additionally, the Zn-Br2 battery designed with ZnMn-NC/GF separator can withstand more serious self-discharge problems of bromine species, with an average discharge voltage platform of 1.75 V at 0.5 A g-1. The self-discharge problem of aqueous Zn-halogen batteries is significantly suppressed by this entrapment-adsorption-catalysis strategy, which can serve as a crucial reference for the advancement of high-performance aqueous Zn-halogen batteries.

Destabilization of Single-Atom Catalysts: Characterization, Mechanisms, and Regeneration Strategies

Numerous in situ characterization studies have focused on revealing the catalytic mechanisms of single-atom catalysts (SACs), providing a theoretical basis for their rational design. Although research is relatively limited, the stability of SACs under long-term operating conditions is equally important and a prerequisite for their real-world energy applications, such as fuel cells and water electrolyzers. Recently, there has been a rise in in situ characterization studies on the destabilization and regeneration of SACs; however, timely and comprehensive summaries that provide the catalysis community with valuable insights and research directions are still lacking. This review summarizes recent advances in the destabilization mechanisms and regeneration strategies of SACs, specifically highlighting various state-of-the-art characterization techniques employed in the studies. The factors that induce destabilization in SACs are identified by discussing the failure of active sites, coordination environments, supports, and reaction conditions under long-term operating scenarios. Next, the primary regeneration strategies for SACs are introduced, including redispersion, surface poison desorption, and exposure of subsurface active sites. Additionally, the advantages and limitations of both in situ and ex situ characterization techniques are discussed. Finally, future research directions are proposed, aimed at constructing structure-stability relationships and guiding the design of more stable SACs.

Energizing Robust Sulfur/Lithium Electrochemistry via Nanoscale-Asymmetric-Size Synergism

Sluggish redox kinetics and dendrite growth perplex the fulfillment of efficient electrochemistry in lithium-sulfur (Li-S) batteries. The complicated sulfur phase transformation and sulfur/lithium diversity kinetics necessitate an all-inclusive approach in catalyst design. Herein, a compatible mediator with nanoscale-asymmetric-size configuration by integrating Co single atoms and defective CoTe2-x (CoSA-CoTe2-x@NHCF) is elaborately developed for regulating sulfur/lithium electrochemistry synchronously. Substantial electrochemistry and theoretical analyses reveal that CoTe2-x exhibits higher catalytic activity in long-chain polysulfide transformation and Li2S decomposition, while monodispersed Co sites are more effective in boosting sulfur reduction kinetics to regulate Li2S deposition. Such cascade catalysis endows CoSA-CoTe2-x@NHCF with the all-around service of "trapping-conversion-recuperation" for sulfur species during the whole redox reaction. Furthermore, it is demonstrated by in situ transmission electron microscopy that initially formed electronic-conductive Co and ionic-conductive Li2Te provide sufficient lithiophilic sites to regulate homogeneous Li plating and stripping with markedly suppressed dendrite growth. Consequently, by coupling the CoSA-CoTe2-x@NHCF interlayer and Li@CoSA-CoTe2-x@NHCF anode, the constructed Li-S full batteries deliver superior cycling stability and rate performance, and the flexible pouch cell exhibits stable cycling performance at 0.3 C. The gained insights into the synergistic effect of asymmetric-size structures pave the way for the integrated catalyst design in advanced Li-S systems.

Vanadium doped in-plane 1T-2H molybdenum disulfide heterostructure as efficient electrocatalyst for lithium-sulfur batteries

The active electronic states in 1T-MoS2 are highly desirable for catalyzing polysulfides conversion. However, stable 1T-MoS2 is difficult to produce using common approaches. Herein, V uniformly doped in-plane 1T-2H heterostructured MoS2 nanosheets (V-MoS2) are prepared by a facile hydrothermal method with a polyoxometalate precursor containing periodic Mo and V atomic arrangement. The doping of V induces the phase transition from semiconducting 2H-MoS2 to metallic 1T-MoS2 and stabilizes the resulted 1T phase. Importantly, the incorporation of V not only modifies the surface electronic property of MoS2, enhancing the active site density, but also improves the adsorption of polysulfides and the catalytic efficiency for sulfur redox reactions. With these advantages, the Li-S batteries using V-MoS2 electrocatalyst achieve accelerated reaction kinetics and superior electrochemical performance. When the S loading of the cathode is 5.41 mg cm-2, a favorable discharge capacity of 4.98 mAh cm-2 is obtained with satisfying cycle stability. This work provides an efficient atomic engineering approach for the design of high performance electrocatalyst for Li-S batteries.

Single Atomic Cu-C3 Sites Catalyzed Interfacial Chemistry in Bi@C for Ultra-Stable and Ultrafast Sodium-Ion Batteries

Regulating interfacial chemistry at electrode-electrolyte interface by designing catalytic electrode material is crucial and challenging for optimizing battery performance. Herein, a novel single atom Cu regulated Bi@C with Cu-C3 site (Bi@SA Cu-C) have been designed via the simple pyrolysis of metal-organic framework. Experimental investigations and theoretical calculations indicate the Cu-C3 sites accelerate the dissociation of P-F and C-O bonds in NaPF6-ether-based electrolyte and catalyze the formation of inorganic-rich and powerful solid electrolyte interphase. In addition, the Cu-C3 sites with delocalized electron around Cu trigger an uneven charge distribution and induce an in-plane local electric field, which facilitates the adsorption of Na+ and reduces the Na+ migration energy barrier. Consequently, the obtained Bi@SA Cu-C achieves a state-of-the-art reversible capacity, ultrahigh rate capability, and long-term cycling durability. The as-constructed full cell delivers a high capacity of 351 mAh g-1 corresponding to an energy density of 265 Wh kg-1. This work provides a new strategy to realize high-efficient sodium ion storage for alloy-based anode through constructing single-atom modulator integrated catalysis and promotion effect into one entity.

Facile Growing of Ni-MOFs on Ni Foam by Self-Dissociation Strategy for Electrochemical Energy Storage

Metal-organic frameworks (MOFs) with redox metal centers have come into view as potential materials for electrochemical energy storage. However, the poor electrical conductivity largely impedes the potentiality of MOFs to construct high-performance electrodes in supercapacitors. In this work, a self-dissociation strategy has been applied to construct Ni-MOF microbelts on Ni foam (NF), where the NF is used as both a support and a Ni source. The transmission channels between the Ni-MOF and NF are favorable for the charge transport due to the in situ self-assembly of the TPA linkers with the dissociated Ni ions from the Ni foam. The grown Ni-MOF microbelt arrays can offer abundant active sites for redox reactions. The prepared Ni-MOF/NF-s electrode can yield a high capacitance of 1124 F g-1 at 1 A g-1 and retains 590 F g-1 at 10 A g-1. This design may offer a controllable protocol for the construction of MOF microbelt arrays on various metal substrates.

Basics and Advances of Manganese-Based Cathode Materials for Aqueous Zinc-Ion Batteries

It is greatly crucial to develop low-cost energy storage candidates with high safety and stability to replace alkali metal systems for a sustainable future. Recently, aqueous zinc-ion batteries (ZIBs) have received tremendous interest owing to their low cost, high safety, wide oxidation states, and sophisticated fabrication process. Nanostructured manganese (Mn)-based oxides in different polymorphs are the potential cathode materials for the widespread application of ZIBs. However, Mn-based oxide materials suffer from several drawbacks, such as low electronic/ionic conductivity and poor cycling performance. To overcome these issues, various structural modification strategies have been adopted to enhance their electrochemical activity, including phase/defect engineering, doping with foreign atoms (e. g., metal and/or nonmetal atoms), and coupling with carbon materials or conducting polymers. Herein, this review targets to summarize the advantages and disadvantages of the above-mentioned strategies to improve the electrochemical performance of the cathodic part of ZIBs. The challenges and suggestions for the development of manganese oxides for ZIBs are put forward.

Integrated Design of Homogeneous/Heterogeneous Copper Complex Catalysts to Enable Synergistic Effects on Sulfur and Lithium Evolution Reactions

Fatal polysulfide shuttling, sluggish sulfur redox kinetics and detrimental lithium dendrites have curtailed the real discharge capacity, working lifespan and safety of lithium-sulfur (Li-S) batteries. Organic small molecule promotors as one type of emerging active catalysts can fulfil the management of the electrochemical species evolution behaviors. Herein, an integrated engineering is organized by synthesizing dual chlorine-bridge enabled binuclear copper complex (Cu2(phen)2Cl2) and its derivative generated in electrolyte (Cu-ETL) as the heterogeneous and homogeneous catalyst, respectively. The well-designed Cu-ETL with a optimized concentration of 0.25 wt% as a homogeneous enabler offers highly utilized Cu centers and the sufficient interface contact for guiding the Li2S nucleation/decomposition reactions. The Cu2(phen)2Cl2 loaded on carbon spheres as an interlayer (Cu-INT) can break through the catalytic limitation resulting from the saturated concentration of Cu-ETL and thus offers an extended manipulation effect. Benefiting from the synergistic effect, the Li-S battery shows stable cycling at 3 C upon 500 cycles with a capacity degradation rate as low as 0.029 % per cycle. Of specific note, an actual cell energy density of 372.1 Wh kg-1 is harvested by a 1.2 Ah-level soft-packaged pouch cell, implying a chance for requiring the demand of high-energy batteries.

Metal-N Coordination in Lithium-Sulfur Batteries: Inhibiting Catalyst Passivation

Lithium-sulfur (Li-S) batteries exhibit great potential as the next-generation energy storage techniques. Application of catalyst is widely adopted to accelerate the redox kinetics of polysulfide conversion reactions and improve battery performance. Although significant attention has been devoted to seeking new catalysts, the problem of catalyst passivation remains underexplored. Herein, we find that metal-N coordination has a previously overlooked role in preventing the catalyst passivation. In the case of nickel, the Ni catalyst reacts with S8 to produce NiSx compounds on the surface, leading to catalyst passivation and slow the kinetics of LiPSs conversion. In contrast, when Ni is coordinated with N (typically Ni-N4), S8 remains stable on the surface. The Ni-N4 exhibits excellent resistance to passivation and rapid kinetics of LiPSs conversion. Consequently, the sulfur cathode with Ni-N4 exhibits a high rate capability of 604.11 mAh g-1 at 3 C and maintains a low capacity decay rate of 0.046 % per cycle over 1000 cycles at 2 C. Furthermore, preventing S passivation in M-N coordination applies not only to Ni-N4 but also to various coordination numbers and transition metals. This study reveals a new aspect of metal-N coordination in inhibiting catalyst passivation, improving our understanding of catalysts in Li-S batteries.

The Role of Long-Range Interactions Between High-Entropy Single-Atoms in Catalyzing Sulfur Conversion Reactions

Sulfur conversion reactions are the foundation of lithium-sulfur batteries but usually possess sluggish kinetics during practical battery operation. Herein, a high-entropy single-atom catalyst (HESAC) is synthesized for this process. In contrast to conventional dual-atom catalysts that form metal-metal bonds, the center metal atoms in HESAC are not bonded but exhibit long-range interactions at a sub-nanometer distance (<9 Å). The synergistic effect between the long-range interactions and entropy changes enables the regulation of d- and π-electron states. This alteration in the electronic structure improves the adsorption and electronic conductivity of intermediate polysulfides, thereby accelerating their conversion kinetics. Consequently, this leads to a significant enhancement in specific capacities by ≈40% at high rates compared to single-atom catalysts. The resulting lithium-sulfur battery with HESAC demonstrates a remarkable areal capacity of 3.4 mAh cm-2 at 10 C. These findings provide valuable insights into the design principle of metal atom catalysts for electrochemical reactions.

Single Atom Engineered Antibiotics Overcome Bacterial Resistance

The outbreak of antibiotic-resistant bacteria, or "superbugs", poses a global public health hazard due to their resilience against the most effective last-line antibiotics. Identifying potent antibacterial agents capable of evading bacterial resistance mechanisms represents the ultimate defense strategy. This study shows that -the otherwise essential micronutrient- manganese turns into a broad-spectrum potent antibiotic when coordinated with a carboxylated nitrogen-doped graphene. This antibiotic material (termed NGA-Mn) not only inhibits the growth of a wide spectrum of multidrug-resistant bacteria but also heals wounds infected by bacteria in vivo and, most importantly, effectively evades bacterial resistance development. NGA-Mn exhibits up to 25-fold higher cytocompatibility to human cells than its minimum bacterial inhibitory concentration, demonstrating its potential as a next-generation antibacterial agent. Experimental findings suggest that NGA-Mn acts on the outer side of the bacterial cell membrane via a multimolecular collective binding, blocking vital functions in both Gram-positive and Gram-negative bacteria. The results underscore the potential of single-atom engineering toward potent antibiotics, offering simultaneously a long-sought solution for evading drug resistance development while being cytocompatible to human cells.

Ionic Liquid-Assisted Synthesis of Higher Loaded Ni/Fe Dual-Atom Catalysts in N, F, B Codoped Carbon Matrix for Accelerated Sulfur Reduction Reaction

In response to mitigating the severe shuttle effect within lithium-sulfur batteries, single-atom catalysts have emerged as one of the most effective solutions. Here, N, F, B codoped porous hollow carbon nanocages (NFB-NiFe@NC) with high Ni and Fe doping are rationally designed and synthesized using ionic liquids (ILs) as dopants. The introduction of ILs inhibits the growth of zeolitic imidazolate framework-8 (ZIF8), resulting in NFB-ZIF8 precursors with smaller particle sizes, enabling higher loading dual-atom catalysts. Meanwhile, the abundant heteroatoms increase the reactive sites and alter the carbon matrix's nonpolar intrinsic properties, thus enhancing the chemisorption of polysulfides. The synergistic interaction of the heteroatoms with Ni and Fe dual-atoms ultimately promotes the catalytic conversion kinetics of polysulfides. As a result of these beneficial properties, the cells prepared using the NFB-NiFe@NC modified separator exhibit significantly improved performance, including a high initial capacity of 1448 mAh g-1 at 0.2 C. Even at a high S-loading of 7.6 mg cm-2, the ideal area capacity of 8.38 mAh cm-2 can still be maintained at 0.1 C. New insights are provided here for designing highly loaded dual-atom catalysts for application in lithium-sulfur batteries.

Bi-Functional Materials for Sulfur Cathode and Lithium Metal Anode of Lithium-Sulfur Batteries: Status and Challenges

Over the past decade, the most fundamental challenges faced by the development of lithium-sulfur batteries (LSBs) and their effective solutions have been extensively studied. To further transfer LSBs from the research phase into the industrial phase, strategies to improve the performance of LSBs under practical conditions are comprehensively investigated. These strategies can simultaneously optimize the sulfur cathode and Li-metal anode to account for their interactions under practical conditions, without involving complex preparation or costly processes. Therefore, "two-in-one" strategies, which meet the above requirements because they can simultaneously improve the performance of both electrodes, are widely investigated. However, their development faces several challenges, such as confused design ideas for bi-functional sites and simplex evaluation methods (i. e. evaluating strategies based on their bi-functionality only). To date, as few reviews have focused on these challenges, the modification direction of these strategies is indistinct, hindering further developments in the field. In this review, the advances achieved in "two-in-one" strategies and categorizing them based on their design ideas are summarized. These strategies are then comprehensively evaluated in terms of bi-functionality, large-scale preparation, impact on energy density, and economy. Finally, the challenges still faced by these strategies and some research prospects are discussed.

Built-in Electric Field Within CoSe2-FeSe2 Heterostructure for Enhanced Sulfur Reduction Reaction in Li-S Batteries

The conversion of Li2S4 to Li2S is the most important and slowest rate-limiting step in the complex sulfur reduction reaction (SRR) for Li-S batteries, the adjustment of which can effectively inhibit the notorious "shuttle effect". Herein, a CoSe2-FeSe2 heterostructure embedded in 3D N-doped nanocage as a modified layer on commercial separator is designed (CoSe2-FeSe2@NC//PP). The CoSe2-FeSe2 heterostructure forms a built-in electric field at the two-phase interface, which leads to the optimized adsorption force on polysulfides and the accelerated reaction kinetics for Li2S4-Li2S evolution. Density functional theory (DFT) calculations and experimental results combine to show that the liquid-solid reaction (Li2S4-Li2S2/Li2S) is significantly enhanced in terms of thermodynamics and electrodynamics. Consequently, the batteries assembled with CoSe2-FeSe2@NC//PP delivered an excellent rate capability (606 mAh g-1 under 8.0 C) and a long cycling lifespan (only 0.056% at 1.0 C after 1000 cycles). In addition, the cells can provide high initial capacity of 887 mAh g-1 at sulfur loading of 5.8 mg cm-2 and 0.1 C. This work would provide valuable insights into binary metal selenide heterostructures for liquid-solid conversion in Li-S batteries.

Electron-delocalization catalyzers for high performance, low-temperature Li-S batteries

The extremely depressive conversion kinetics of polysulfides due to sluggish Li+ diffusion kinetics remain to be resolved for low-temperature Li-S batteries (LT-LSB). Herein, the strategy for electron-delocalization of nanocatalysts has been designed through introducing oxygen defects on vanadium trioxide that was anchored on a porous carbon network (ODVO@PCN). The reconstructed active sites of the V2+ state tend to interact with sulfur species more easily due to the stronger hybridization between V2+ sites and S sites in sulfur species, allowing enhanced Li+ transformation kinetics across the electrolyte/electrode interface for a fast redox reaction in the low-temperature surrounding. Consequently, at a low temperature of 0 °C, the cell with the ODVO@PCN kinetic promotor exhibits 501 mA h g-1 at 1C and a long life time of up to 400 cycles at 0.5C. Reduced to ultralow -10 °C, the cell still provides a capacity of 706 mA h g-1 and stabilizes a remarkable capacity retention of 85% after 100 cycles.

Coordinatively Unsaturated Co Single-Atom Catalysts Enhance the Performance of Lithium-Sulfur Batteries by Triggering Strong d-p Orbital Hybridization

The catalytic activities displayed by single-atom catalysts (SACs) depend on the coordination structure. SACs supported on carbon materials often adopt saturated coordination structures with uneven distributions because they require high-temperature conditions during synthesis. Herein, bisnitrogen-chelated Co SACs that are coordinatively unsaturated are prepared by integrating a Co complex into a conjugated microporous polymer (CMP-CoN2). Compared with saturated analogues, i.e., tetranitrogen-chelated Co SACs (denoted as CMP-CoN4), CMP-CoN2 exhibits higher electrocatalytic activity in polysulfide conversions due to an enhanced hybridization between the 3d orbitals of the Co atoms and the 3p orbitals of the S atoms in the polysulfide. As a result, sulfur cathodes prepared with CoN2 deliver outstanding performance metrics, including a high specific capacity (1393 mA h g-1 at 0.1 C), a superior rate capacity (673.2 mA h g-1 at 6 C), and a low capacity decay rate (of only 0.045% per cycle at 2 C over 1000 cycles). They also outperform sulfur cathodes that contain CMP-CoN4 or CMPs that are devoid of Co SACs. This work reveals how the catalytic activity displayed by SACs is affected by their coordination structures, and the rules that underpin the structure-activity relationship may be extended to designing electrocatalysts for use in other applications.

Breaking the Passivation Effect for MnO2 Catalysts in Li-S Batteries by Anion-Cation Doping

Transition metal oxides (TMOs) are recognized as high-efficiency electrocatalyst systems for restraining the shuttle effect in lithium-sulfur (Li-S) batteries, owing to their robust adsorption capabilities for polysulfides. However, the sluggish catalytic conversion of Li2S redox and severe passivation effect of TMOs exacerbate polysulfide shuttling and reduce the cyclability of Li-S batteries, which significantly hinders the development of TMOs electrocatalysts. Here, through the anion-cation doping approach, dual incorporation of phosphorus and molybdenum into MnO2 (P,Mo-MnO2) was engineered, demonstrating effective mitigation of the passivation effect and allowing for the simultaneous immobilization of polysulfides and rapid redox kinetics of Li2S. Both experimental and theoretical investigations reveal the pivotal role of dopants in fine-tuning the d-band center and optimizing the electronic structure of MnO2. Furthermore, this well-designed configuration processes catalytic selectivity. Specifically, P-doping expedites rapid Li2S nucleation kinetics by minimizing reaction-free energy, while Mo-doping facilitates robust Li2S dissolution kinetics by mitigating decomposition barriers. This dual-doping approach equips P,Mo-MnO2 with robust bi-directional catalytic activity, effectively overcoming passivation effect and suppressing the notorious shuttle effect. Consequently, Li-S batteries incorporating P,Mo-MnO2-based separators demonstrate favorable performance than pristine TMOs. This design offers rational viewpoint for the development of catalytic materials with superior bi-directional sulfur electrocatalytic in Li-S batteries.

Physical Field Effects to Suppress Polysulfide Shuttling in Lithium-Sulfur Battery

Lithium-sulfur batteries (LSB) with high theoretical energy density are plagued by the infamous shuttle effect of lithium polysulfide (LPS) and the sluggish sulfur reduction/evolution reaction. Extensive research is conducted on how to suppress shuttle effects, including physical structure confinement engineering, chemical adsorption strategy, and the design of sulfur redox catalysts. Recently, the rational design to mitigate shuttle effects and enhance reaction kinetics based on physical field effects has been widely studied, providing a more fundamental understanding of interactions with sulfur species. Herein, the physical field effect is focused and their methods and mechanisms of interaction are summarized systematically with LPS. Overall, the working principle of LSB system, the origin of the shuttle effect, and kinetic trouble in LSB are briefly described. Then, the mechanism and application of rational design of materials based on physical field effect concepts and the external physical field-assisted LSB are elaborated, including electrostatic force, built-in electric field, spin state regulation, strain engineering, external magnetic field, photoassisted and other physical field-assisted strategies are pivotally elaborated and discussed. Finally, the potential directions of physical field effects in enhancing the performance and weakening the shuttle effect of high-energy LSB are summarized and anticipated.

In Situ Synthesis of CoMoO4 Microsphere@rGO as a Matrix for High-Performance Li-S Batteries at Room and Low Temperatures

Lithium-sulfur batteries (Li-S batteries) have attracted wide attention due to their high theoretical energy density and the low cost of sulfur cathode material. However, the poor conductivity of the sulfur cathode, the polysulfide shuttle effect, and the slow redox kinetics severely affect their cycling performance and Coulombic efficiencies, especially under low-temperature conditions, where these effects are more exacerbated. To address these issues, this study designs and synthesizes a microspherical cobalt molybdate@reduced graphene oxide (CoMoO4@rGO) composite material as the cathode material for Li-S batteries. By growing CoMoO4 nanoparticles on the rGO surface, the composite material not only provides a good conductive network but also significantly enhances the adsorption capacity to polysulfides, effectively suppressing the shuttle effect. After 100 cycles at room temperature with a current density of 1 C, the reversible specific capacity of the battery stabilizes at 805 mAh g-1. Notably, at -20 °C, the S/CoMoO4@rGO composite achieves a reversible specific capacity of 840 mAh g-1. This study demonstrates that the CoMoO4@rGO composite has significant advantages in suppressing polysulfide diffusion and expanding the working temperature range of Li-S batteries, showing great potential for applications in next-generation high-performance Li-S batteries.

Iodine-doped carbon nanotubes boosting the adsorption effect and conversion kinetics of lithium-sulfur batteries

Compared with lithium-ion batteries (LIBs), lithium-sulfur batteries (LSBs), based on electrochemical reactions involving multi-step 16-electron transformations provide higher specific capacity (1672 mAh g-1) and specific energy (2600 Wh kg-1), exhibiting great potential in the field of energy storage. However, the inherent insulation of sulfur, slow electrochemical reaction kinetics and detrimental shuttle-effect of lithium polysulfides (LiPSs) restrict the development of LSBs in practical applications. Herein, the iodine-doped carbon nanotubes (I-CNTs) is firstly reported as sulfur host material to the enhance the adsorption-conversion kinetics of LSBs. Iodine doping can significantly improve the polarity of I-CNTs. Iodine atoms with lone pair electrons (Lewis base) in iodine-doped CNTs can interact with lithium cations (Lewis acidic) in LiPSs, thereby anchoring polysulfides and suppressing subsequent shuttling behavior. Moreover, the charge transfer between iodine species (electron acceptor) and CNTs (electron donor) decreases the gap band and subsequently improves the conductivity of I-CNTs. The enhanced adsorption effect and conductivity are beneficial for accelerating reaction kinetics and enhancing electrocatalytic activity. The in-situ Raman spectroscopy, quasi in-situ electrochemical impedance spectroscopy (EIS) and Li2S potentiostatic deposition current-time (i-t) curves were conducted to verify mechanism of complex sulfur reduction reaction (SRR). Owing to above advantages, the I-CNTs@S composite cathode exhibits an ultrahigh initial capacity of 1326 mAh g-1 as well as outstanding cyclicability and rate performance. Our research results provide inspirations for the design of multifunctional host material for sulfur/carbon composite cathodes in LSBs.

Theoretical Design and Study of a Single-Atom Catalyst in Lithium-Sulfur Batteries: Edge-Type FeN4 Active Site Electron Density Redistribution Driven by Heteroatoms

Lithium-sulfur (Li-S) batteries are considered to be the most promising next-generation high energy density storage systems. However, they still face challenges, such as the shuttle effect of lithium polysulfides (LiPSs) and slow sulfur oxidation-reduction kinetics. In this work, heteroatom (P and S)-doped edge-type Fe single-atom catalytic materials (FeN4S2/P2-DG) for sulfur reduction reactions (SRRs) and sulfur oxidation reactions in Li-S batteries are investigated using density functional theory calculations. Theoretical analysis suggests that compared to planar Fe-N4 fragments, the charge density accumulation around edge-type Fe-N4 fragments in S- or P-doped structures is higher. Furthermore, the doping of P or S reduces the electron filling state of Fe_3d orbitals, leading to a decrease in electron occupancy in the antibonding orbitals, which is beneficial for the formation of d-p orbital hybridization, strengthening the anchoring strength of FeN4P2/S2-DG for S8/LiPSs. Specifically, FeN4P1,2-DG showed the lowest free energy barriers (0.57 eV) for SRRs and reduced the dissociation energy barrier of Li2S from 1.85 eV (for planar FeN4-G) to 0.96 eV during the charging process, demonstrating excellent catalytic ability. Additionally, this theoretical study provides further insights into the application of graphene-supported single-atom catalyst materials as anchoring materials for Li-S batteries.

Enabling Efficient Anchoring-Conversion Interface by Fabricating Double-Layer Functionalized Separator for Suppressing Shuttle Effect

Lithium-sulfur batteries (LiSBs) with high energy density still face challenges on sluggish conversion kinetics, severe shuttle effects of lithium polysulfides (LiPSs), and low blocking feature of ordinary separators to LiPSs. To tackle these, a novel double-layer strategy to functionalize separators is proposed, which consists of Co with atomically dispersed CoN4 decorated on Ketjen black (Co/CoN4@KB) layer and an ultrathin 2D Ti3C2Tx MXene layer. The theoretical calculations and experimental results jointly demonstrate metallic Co sites provide efficient adsorption and catalytic capability for long-chain LiPSs, while CoN4 active sites facilitate the absorption of short-chain LiPSs and promote the conversion to Li2S. The stacking MXene layer serves as a microscopic barrier to further physically block and chemically anchor the leaked LiPSs from the pores and gaps of the Co/CoN4@KB layer, thus preserving LiPSs within efficient anchoring-conversion reaction interfaces to balance the accumulation of "dead S" and Li2S. Consequently, with an ultralight loading of Co/CoN4@KB-MXene, the LiSBs exhibit amazing electrochemical performance even under high sulfur loading and lean electrolyte, and the outperforming performance for lithium-selenium batteries (LiSeBs) can also be achieved. This work exploits a universal and effective strategy of a double-layer functionalized separator to regulate the equilibrium adsorption-catalytic interface, enabling high-energy and long-cycle LiSBs/LiSeBs.

Single-Atom Cobalt Catalyst with Boron and Nitrogen Codoped Graphene (Co-BN-G) Enables Adsorption and Catalytic Conversion of Polysulfides for High-Performance Lithium-Sulfur Batteries

In lithium-sulfur batteries, the shuttling effect and sluggish redox conversion of soluble polysulfides lead to unsatisfactory sulfur utilization and capacity retention. In this research, we used a one-pot hydrothermal method to prepare graphene with single-atom Co and B, N codoped as a sulfur host in Li-S batteries, thereby suppressing the shuttling effect and facilitating the redox conversion of lithium polysulfides (LiPSs). A series of characterizations demonstrated that dual doping of B and N introduces more lattice defects and structural deformations in graphene oxide, thus enhancing its adsorption of polysulfides. Simultaneously, single-atom cobalt can also polarize adsorption and accelerate the conversion reaction of LiPSs. The Li-S cell with the as-prepared Co-BN-G sulfur host materials exhibited an excellent capacity of 1034 mAh g-1 at 0.5 C and satisfactory cycle performance (retention of 69% over 500 cycles). Even at a rate of 2 C, a discharge capacity of 851 mAh g-1 is achieved. The results show that the Co-BN-G configuration efficiently captures LiPSs and enhances their rate conversion kinetics in redox reactions, demonstrating significant practical potential.

Engineering Oxygen Vacancies in In2O3 with Enhanced Polysulfides Immobilization and Selective Catalytic Capability

Lithium-sulfur (Li-S) battery is identified as an ideal candidate for next-generation energy storage systems in consideration of its high theoretical energy density and abundant sulfur resources. However, the shuttling behavior of soluble polysulfides (LiPSs) and their sluggish reaction kinetics severely limit the practical application of the current Li-S battery. In this work, a series of In2O3 nanocubes with different oxygen vacancy concentrations are designed and prepared via a facile self-template method. The introduced oxygen vacancy on In2O3 can effectively rearrange the charge distribution and enhance sulfiphilic property. Moreover, the In2O3 with high oxygen vacancy concentration (H-In2O3) can slightly slow down the solid-liquid conversion process and significantly accelerate the liquid-solid conversion process, thus reducing the accumulation of LiPSs in electrolyte and inhibiting the shuttle effect. Contributed by the unique selective catalytic capability, the prepared H-In2O3 exhibits excellent electrochemical performance when used as sulfur host. For instance, a high reversible capacity of 609 mAh g-1 is obtained with only 0.044% capacity decay per cycle over 1000 cycles at 1.0 C. This work presents a typical example for designing advanced sulfur hosts, which is crucial for the commercialization of Li-S battery.

An Electrolyte Engineered Homonuclear Copper Complex as Homogeneous Catalyst for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries suffer from severe polysulfide shuttle, retarded sulfur conversion kinetics and notorious lithium dendrites, which has curtailed the discharge capacity, cycling lifespan and safety. Engineered catalysts act as a feasible strategy to synchronously manipulate the evolution behaviors of sulfur and lithium species. Herein, a chlorine bridge-enabled binuclear copper complex (Cu-2-T) is in situ synthesized in electrolyte as homogeneous catalyst for rationalizing the Li-S redox reactions. The well-designed Cu-2-T provides completely active sites and sufficient contact for homogeneously guiding the Li2S nucleation/decomposition reactions, and stabilizing the lithium working interface according to the synchrotron radiation X-ray 3D nano-computed tomography, small angle neutron scattering and COMSOL results. Moreover, Cu-2-T with the content of 0.25 wt% approaching saturated concentration in electrolyte further boosts the homogeneous optimization function in really operated Li-S batteries. Accordingly, the capacity retention of the Li-S battery is elevated from 51.4% to 86.3% at 0.2 C, and reaches 77.0% at 1.0 C over 400 cycles. Furthermore, the sulfur cathode with the assistance of Cu-2-T realizes the stable cycling under the practical scenarios of soft-packaged pouch cell and high sulfur loading (6.5 mg cm-2 with the electrolyte usage of 4.5 µL mgS -1).

Surface topology of MXene flakes induces the selection of the sintering mechanism for supported Pt nanoparticles

Sintering of metal nanocatalysts leading to particle growth and subsequent performance deactivation is a primary issue that hinders their practical applications. While metal-support interaction (MSI) is considered as the critical factor which influences the sintering behavior, the underlying microscopic mechanism and kinetics remain incompletely understood. Here, by using in situ scanning transmission electron microscopy (STEM) and theoretical analysis, we reveal the selection rule of the sintering mechanism for Pt nanoparticles on a two-dimensional (2D) MXene (Ti3C2T x ) support, which relies on the surface topology of MXene flakes. It is demonstrated that the sintering of Pt nanoparticles proceeds via Ostwald ripening (OR) in the surface defect (such as steps and pore edges) regions of MXene flakes due to strong MSI on the Pt/MXene interface; conversely, weak MSI between Pt nanoparticles and the planar surface of MXene leads to prevalent particle migration and coalescence (PMC) for sintering. Furthermore, our quantitative analysis shows a significant divergence in sintering rates for PMC and OR processes. These microscopic observations suggest a clear "sintering mechanism-MSI" relationship for Pt/MXene nanocatalysts and may shed light on the design of novel nanocatalysts.

Toward Functionality and Deactivation of Metal-Single-Atom in Heterogeneous Photocatalysts

Single-atom heterogeneous catalysts (SAHCs) provide an enticing platform for understanding catalyst structure-property-performance relationships. The 100% atom utilization and adjustable local coordination configurations make it easy to probe reaction mechanisms at the atomic level. However, the progressive deactivation of metal-single-atom (MSA) with high surface energy leads to frequent limitations on their commercial viability. This review focuses on the atomistic-sensitive reactivity and atomistic-progressive deactivation of MSA to provide a unifying framework for specific functionality and potential deactivation drivers of MSA, thereby bridging function, purpose-modification structure-performance insights with the atomistic-progressive deactivation for sustainable structure-property-performance accessibility. The dominant functionalization of atomically precise MSA acting on properties and reactivity encompassing precise photocatalytic reactions is first systematically explored. Afterward, a detailed analysis of various deactivation modes of MSA and strategies to enhance their durability is presented, providing valuable insights into the design of SAHCs with deactivation-resistant stability. Finally, the remaining challenges and future perspectives of SAHCs toward industrialization, anticipating shedding some light on the next stage of atom-economic chemical/energy transformations are presented.

Atomic-Level Catalyst Coupled with Metal Oxide Heterostructure for Promoting Kinetics of Lithium-Sulfur Batteries

Despite the low competitive cost and high theoretical capacity of lithium-sulfur (Li-S) batteries, their practical application is severely hindered by the lithium polysulfide (LiPS) shuttling and low conversion efficiency. Herein, the electronic structure of hollow Titanium dioxide nanospheres is tunned by single Iron atom dopants that can cooperatively enhance LiPS absorption and facilitate desired redox reaction in practical Li-S batteries, further suppressing the notorious shuttle effect, which is consistent with theoretical calculations and in situ UV/vis investigation. The obtained electrode with massive active sites and lower energy barrier for sulfur conversions exhibits exceptional cycling stability after 500 cycles and high capacity under the sulfur loading of 10.53 mg cm-2. In particular, an Ah-level Li-S pouch cell is fabricated, further demonstrating that the synthetic strategy based on atomic-level design offers a promising route toward practical high-energy-density Li-S batteries.

Dependence of Interlayer or Sulfur Host on Hollow Framework of Lithium-Sulfur Battery

Lithium-sulfur batteries are recognized as the next generation of high-specific energy secondary batteries owing to their satisfactory theoretical specific capacity and energy density. However, their commercial application is greatly limited by a series of problems, including disordered migration behavior, sluggish redox kinetics, and the serious shuttle effect of lithium polysulfides. One of the most efficient approaches to physically limit the shuttle effect is the rational design of a hollow framework as sulfur host. However, the influence of the hollow structure on the interlayers has not been clearly reported. In this study, the Mo2C/C catalysts with hollow(H-Mo2C/C) and solid(S-Mo2C/C) frameworks are rationally designed to explore the dependence of the hollow structure on the interlayer or sulfur host. In contrast to the physical limitations of the hollow framework as host, the hollow structure of the interlayer inhibited lithium-ion diffusion, resulting in poor electrochemical properties at high current densities. Based on the superiority of the various frameworks, the H-Mo2C/C@S | S-Mo2C/C@PP | Li cells are assembled and displayed excellent electrochemical performance. This work re-examines the design requirements and principles of catalyst frameworks in different battery units.

Advancing Metallic Lithium Anodes: A Review of Interface Design, Electrolyte Innovation, and Performance Enhancement Strategies

Lithium (Li) metal is one of the most promising anode materials for next-generation, high-energy, Li-based batteries due to its exceptionally high specific capacity and low reduction potential. Nonetheless, intrinsic challenges such as detrimental interfacial reactions, significant volume expansion, and dendritic growth present considerable obstacles to its practical application. This review comprehensively summarizes various recent strategies for the modification and protection of metallic lithium anodes, offering insight into the latest advancements in electrode enhancement, electrolyte innovation, and interfacial design, as well as theoretical simulations related to the above. One notable trend is the optimization of electrolytes to suppress dendrite formation and enhance the stability of the electrode-electrolyte interface. This has been achieved through the development of new electrolytes with higher ionic conductivity and better compatibility with Li metal. Furthermore, significant progress has been made in the design and synthesis of novel Li metal composite anodes. These composite anodes, incorporating various additives such as polymers, ceramic particles, and carbon nanotubes, exhibit improved cycling stability and safety compared to pure Li metal. Research has used simulation computing, machine learning, and other methods to achieve electrochemical mechanics modeling and multi-field simulation in order to analyze and predict non-uniform lithium deposition processes and control factors. In-depth investigations into the electrochemical reactions, interfacial chemistry, and physical properties of these electrodes have provided valuable insights into their design and optimization. It systematically encapsulates the state-of-the-art developments in anode protection and delineates prospective trajectories for the technology's industrial evolution. This review aims to provide a detailed overview of the latest strategies for enhancing metallic lithium anodes in lithium-ion batteries, addressing the primary challenges and suggesting future directions for industrial advancement.

Rare Earth Single-Atom Catalysis for High-Performance Li-S Full Battery with Ultrahigh Capacity

Lithium-sulfur (Li-S) batteries have many advantages but still face problems such as retarded polysulfides redox kinetics and Li dendrite growth. Most reported single atom catalysts (SACs) for Li-S batteries are based on d-band transition metals whose d orbital constitutes active valence band, which is inclined to occur catalyst passivation. SACs based on 4f inner valence orbital of rare earth metals are challenging for their great difficulty to be activated. In this work, we design and synthesize the first rare earth metal Sm SACs which has electron-rich 4f inner orbital to promote catalytic conversion of polysulfides and uniform deposition of Li. Sm SACs enhance the catalysis by the activated 4f orbital through an f-d-p orbital hybridization. Using Sm-N3C3 modified separators, the half cells deliver a high capacity over 600 mAh g-1 and a retention rate of 84.3 % after 2000 cycles. The fabricated Sm-N3C3-Li|Sm-N3C3@PP|S/CNTs full batteries can provide an ultra-stable cycling performance of a retention rate of 80.6 % at 0.2 C after 100 cycles, one of the best full Li-S batteries. This work provides a new perspective for the development of rare earth metal single atom catalysis in electrochemical reactions of Li-S batteries and other electrochemical systems for next-generation energy storage.

Room temperature, ultrafast and one-step synthesis of highly fluorescent sulfur quantum dots probe and their logic gate operation

The direct and rapid conversion of abundant and cheap elemental sulfur into fluorescent sulfur quantum dots (SQDs) at room temperature is a critical and urgent challenge. Conventional synthesis methods require high temperatures, high pressures, or specific atmospheric conditions, making them complex and impractical for real applications. Herein, we propose a simple method for synthesizing SQDs simply by adding H2O2 to an elemental sulfur-ethylenediamine (S-EDA) solution at room temperature. Remarkably, within a mere 10 min, SQDs with a photoluminescence quantum yield of 23.6 % can be obtained without the need for additional steps. A comprehensive analysis of the mechanism has demonstrated that H2O2 is capable of converting Sx2- ions generated in the S-EDA solution into zero-valent sulfur atoms through oxidation. The obtained SQDs can be utilized as a fluorescent probe for detection of tetracycline (TC) and Ca2+ ions with the limit of detection (LOD) of 0.137 μM and 0.386 μM respectively. Moreover, we have developed a sensitive logic gate sensor based on SQDs, harnessing the activated cascade effect to create an intelligent probe for monitoring trace levels of TC and Ca2+ ions. This paper not only presents a viable approach for ultrafast and scalable synthesis of SQDs at room temperature, but also contributes to the efficient utilization of elemental sulfur resources.

Hollow Defect-Rich Nanofibers as Sulfur Hosts for Lithium-Sulfur Batteries

The slow redox kinetics of lithium-sulfur batteries severely limit their application, and sulfur utilization can be effectively enhanced by designing different cathode sulfur host materials. Herein, we report the hollow porous nanofiber LaNi0.6Co0.4O3 as a bidirectional host material for lithium-sulfur batteries. After Co is substituted into LaNiO3, oxygen vacancies are generated to enhance the material conductivity and enrich the active sites of the material, and the electrochemical reaction rate can be further accelerated by the synergistic catalytic ability of Ni and Co elements in the B-site of the active site of LaNi0.6Co0.4O3. As illustrated by the kinetic test results, LaNi0.6Co0.4O3 effectively accelerated the interconversion of lithium polysulfides, and the nucleation of Li2S and the dissolution rate of Li2S were significantly enhanced, indicating that LaNi0.6Co0.4O3 accelerated the redox kinetics of the lithium-sulfur battery during the charging and discharging process. In the electrochemical performance test, the initial discharge specific capacity of S/LaNi0.6Co0.4O3 was 1140.4 mAh g-1 at 0.1 C, and it was able to release a discharge specific capacity of 584.2 mAh g-1 at a rate of 5 C. It also showed excellent cycling ability in the long cycle test, with a single-cycle capacity degradation rate of only 0.08%. Even under the harsh conditions of high loaded sulfur and low electrolyte dosage, S/LaNi0.6Co0.4O3 still delivers excellent specific capacity and excellent cycling capability. Therefore, this study provides an idea for the future development of bidirectional high-activity electrocatalysts for lithium-sulfur batteries.

Constructing Orbital Coupling-Modulated Homogeneous Dual-Atom Fe-Fe Sites for Boosting Bidirectional Conversion of Polysulfides

Homogeneous dual-atom catalysts (HDACs) have garnered significant attention for their potential to overcome the shuttling effect and sluggish reaction kinetics in lithium-sulfur (Li-S) batteries. However, modulating the electron structure of metal atomic orbitals for HDACs to dictate the catalytic activity toward polysulfides has remained meaningful but unexplored so far. Herein, an interfacial cladding strategy is developed to obtain a new type of dual-atom iron matrix with a unique FeN2P1-FeN2P1 coordination structure (Fe2@NCP). The 3d orbital electrons of the Fe centers are redistributed by incorporating phosphorus atoms into the first coordination sphere. The theoretical calculations disclose that the strong coupling between the Fe d orbital and the S p orbital exhibits an enhanced Fe-S bond and improved reactivity toward polysulfides. Moreover, the Fe2@NCP catalyst achieves robust adsorption ability toward Li2Sn (1 ≤ n ≤ 8) and significantly boosts bidirectional sulfur redox reaction kinetics by lowering the Li2S deposition/decomposition energy barriers. Consequently, the assembled Li-S batteries present a high retention ratio of 77.3% after 500 cycles at 1C. Furthermore, the Li-S pouch cell also exhibits good performance at 0.1C (80.2% retention over 100 cycles) for practical application with a sulfur loading of 4.0 mg/cm2. The outcome of this study will facilitate the design of homogeneous dual-atom catalysts for Li-S batteries.

Optimized Adsorption-Catalytic Conversion for Lithium Polysulfides by Constructing Bimetallic Compounds for Lithium-Sulfur Batteries

Although lithium-sulfur batteries possess the advantage of high theoretical specific capacity, the inevitable shuttle effect of lithium polysulfides is still a difficult problem restricting its application. The design of highly active catalysts to promote the redox reaction during charge-discharge and thus reduce the existence time of lithium polysulfides in the electrolyte is the mainstream solution at present. In particular, bimetallic compounds can provide more active sites and exhibit better catalytic properties than single-component metal compounds by regulating the electronic structure of the catalysts. In this work, bimetallic compounds-nitrogen-doped carbon nanotubes (NiCo)Se2-NCNT and (CuCo)Se2-NCNT are designed by introducing Ni and Cu into CoSe2, respectively. The (CuCo)Se2-NCNT delivers an optimized adsorption-catalytic conversion for lithium polysulfide, benefitting from adjusted electron structure with downshifted d-band center and increased electron fill number of Co in (CuCo)Se2 compared with that of (NiCo)Se2. This endows (CuCo)Se2 moderate adsorption strength for lithium polysulfides and better catalytic properties for their conversion. As a result, the lithium-sulfur batteries with (CuCo)Se2-NCNT achieve a high specific capacity of 1051.06 mAh g-1 at 1C and an enhanced rate property with a specific capacity of 838.27 mAh g-1 at 4C. The work provides meaningful insights into the design of bimetallic compounds as catalysts for lithium-sulfur batteries.

Alveoli-Inspired Carbon Cathodes with Interconnected Porous Structure and Asymmetric Coordinated Vanadium Sites for Superior Li-S Batteries

Accelerating sulfur conversion catalysis to alleviate the shuttle effect has become a novel paradigm for effective Li-S batteries. Although nitrogen-coordinated metal single-atom (M-N4) catalysts have been investigated, further optimizing its utilization rate and catalytic activities is urgently needed for practical applications. Inspired by the natural alveoli tissue with interconnected structure and well-distributed enzyme catalytic sites on the wall for the simultaneously fast diffusion and in situ catalytic conversion of substrates, here, we proposed the controllable synthesis of bioinspired carbon cathode with interconnected porous structure and asymmetric coordinated V-S1N3 sites for efficient and stable Li-S batteries. The enzyme-mimetic V-S1N3 shows asymmetric electronic distribution and high tunability, therefore enhancing in situ polysulfide conversion activities. Experimental and theoretical results reveal that the high charge asymmetry degree and large atom radius of S in V-S1N3 result in sloping adsorption for polysulfide, thereby exhibiting low thermodynamic energy barriers and long-range stability (0.076 % decay over 600 cycles).

Atom-Level Tandem Catalysis in Lithium Metal Batteries

High-energy-density lithium metal batteries (LMBs) are limited by reaction or diffusion barriers with dissatisfactory electrochemical kinetics. Typical conversion-type lithium sulfur battery systems exemplify the kinetic challenges. Namely, before diffusing or reacting in the electrode surface/interior, the Li(solvent)x + dissociation at the interface to produce isolated Li+, is usually a prerequisite fundamental step either for successive Li+ "reduction" or for Li+ to participate in the sulfur conversions, contributing to the related electrochemical barriers. Thanks to the ideal atomic efficiency (100 at%), single atom catalysts (SACs) have gained attention for use in LMBs toward resolving the issues caused by the five types of barrier-restricted processes, including polysulfide/Li2S conversions, Li(solvent)x + desolvation, and Li0 nucleation/diffusion. In this perspective, the tandem reactions including desolvation and reaction or plating and corresponding catalysis behaviors are introduced and analyzed from interface to electrode interior. Meanwhile, the principal mechanisms of highly efficient SACs in overcoming specific energy barriers to reinforce the catalytic electrochemistry are discussed. Lastly, the future development of high-efficiency atomic-level catalysts in batteries is presented.

Single-atom catalysts based on C2N for sulfur cathodes in Na-S batteries: a first-principles study

Several major roadblocks, including the "shuttle effect" caused by the dissolved higher-order sodium polysulfides (NaPSs), extremely poor conductivity of sulfur cathodes, and sluggish conversion kinetics of charging-discharging reactions, have hindered the commercialization of sodium-sulfur batteries (NaSBs). In our study, representative C2N-based single-atom catalysts (SACs), TM@C2N (TM = Fe, Ni and V), are proposed to improve the comprehensive performance of NaSBs. Based on first-principles calculations, we first discuss in detail the anchoring behavior of all adsorption systems, TM@C2N/(S8 and NaPSs). The results indicate that compared to pristine C2N, TM@C2N substrates exhibit a stronger capability to capture S8/NaPSs clusters through physical/chemical binding, with V@C2N showing the most outstanding capability ranging from -2.37 to -5.03 eV. The density of states analysis reveals that metallic properties can be well maintained before and after adsorption of polysulfides. More importantly, TM@C2N configurations can greatly reduce the energy barriers of charging and discharging reactions, thereby accelerating the conversion efficiency of NaSBs. It is worth mentioning that V@C2N has lower charge-discharge energy barriers and Na ion migration rates, since the embedded TM atom weakens the strong binding of Na+ in the N6 cavity of C2N. The intrinsic mechanism analysis reveals that the interaction between the d orbitals of V and the p orbitals of S leads to the weakening of Na-S bonds, which can not only effectively inhibit the shuttle effect, but also promote the dissociation of Na2S. Overall, this work not only offers excellent catalytic materials, but also provides vital guidance for designing SACs in NaSBs.

Relay-Type Catalysis by a Dual-Metal Single-Atom System in a Waste Biomass Derivative Host for High-Rate and Durable Li-S Batteries

An environmental-friendly and sustainable carbon-based host is one of the most competitive strategies for achieving high loading and practicality of Li-S batteries. However, the polysulfide conversion reaction kinetics is still limited by the nonuniform or monofunctional catalyst configuration in the carbon host. In this work, we propose a catalysis mode based on "relay-type" co-operation by adjacent dual-metal single atoms for high-rate and durable Li-S batteries. A discarded sericin fabric-derived porous N-doped carbon with a stacked schistose structure is prepared as the high-loading sulfur (84 wt %) host by a facile ionothermal method, which further enables the uniform anchoring of Fe/Co dual-metal single atoms. This multifunctional host enables superior lithiophilic-sulfiphilic and electrocatalytic capabilities contributed by the "relay-type" single-atom modulation effects on different conversion stages of liquid polysulfides and solid Li2S2/Li2S, leading to the suppression of the "shuttle effect", alleviation of nucleation and decomposition barriers of Li2Sx, and acceleration of polysulfide conversion kinetics. The corresponding Li-S batteries exhibit a high specific capacity of 1399.0 mA h g-1, high-rate performance up to 10 C, and excellent cycling stability over 1000 cycles. They can also endure the high sulfur loading of 8.5 mg cm-2 and the lean electrolyte condition and yield an areal capacity as high as 8.6 mA h cm-2. This work evidentially demonstrates the potential of waste biomass reutilization coupled with the design of a single-atom system for practical Li-S batteries with high energy density.

Rapid Growth of Bi2Se3 Nanodots on MXene Nanosheets at Room Temperature for Promoting Sulfur Redox Kinetics

Li-S batteries are hampered by problems with their cathodes and anodes simultaneously. The improvement of Li-S batteries needs to consider both the anode and cathode. Herein, a Bi2Se3@MXene composite is prepared for the first time by rapidly growing Bi2Se3 nanodots on two-dimensional (2D) MXene nanosheets at room temperature through simply adding high-reactive hydroxyethylthioselenide in Bi3+/MXene aqueous solution. Bi2Se3@MXene exhibits a 2D structure due to the template effect of 2D MXene. Bi2Se3@MXene can not only facilitate the conversion of lithium polysulfides (LiPSs) but also inhibit their shuttling in the S cathode due to its catalytic effect and adsorption force with LiPSs. Bi2Se3@MXene can also be used as an interfacial lithiophilic layer to inhibit Li dendrite growth in the Li metal anode. Theoretical calculations reveal that Bi2Se3 nanodots in Bi2Se3@MXene can effectively boost the adsorption ability with LiPSs, and the MXene in Bi2Se3@MXene can accelerate the electron transport. Under the bidirectional regulation of Bi2Se3@MXene in the Li metal anode and S cathode, the Li-S battery shows an enhanced electrochemical performance.