Sulfur Redox Research Articles

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.

Probing the effect of Se doping in S cathode for high performance Mg-S batteries

Magnesium-sulfur (Mg-S) batteries present an attractive option as a new type of energy storage device given their high energy density, safety and the use of low-cost original materials. However, magnesium polysulfide (MgPS) is susceptible to dissolution and shuttling, and the insulating nature of sulfur and MgS leads to high overpotentials and low columbic efficiencies. The selenium-sulfur system is noted to offer enhanced electronic conductivity and improved sulfur utilization. In this study, S K-edge X-ray absorption near-edge structure (XANES) spectra demonstrate that Se doping mitigates irreversibility in Mg-S batteries. Mg-K spectra demonstrate that Se dopants induce local negative charges on S, strengthening the Mg-S bond compared to that of pure sulfur, thereby promoting Mg/Mg2+ redox reactions. Operando Raman spectroscopy was also used to reveal Mg-S0.9Se0.1/C battery redox mechanisms. Hence, kinetically favored S0.9Se0.1/C cathodes deliver an initial capacity of ∼1350 mAh·g−1 at 0.2C. Furthermore, separators modified with layered MoS2 entrap polysulfides, thereby postponing cell death. Thus, Mg-S battery with a S0.9Se0.1/C cathode and a MoS2@polypropylene (PP) separator exhibit a reversible capacity of ∼200 mAh·g−1 at 0.2C after 250 cycles, with a low fade rate of 4 mAh·g−1/cycle. This study delineates the overall impact of Se doped cathodes on Mg-S batteries. Moreover, the MoS2 modified separator provides a route to chemically immobilize MgPS and accelerate sulfur redox reactions, consequently enabling high capacities and sustained cycling.

Accelerating sulfur redox kinetics by rare earth single-atom electrocatalysts toward efficient lithium–sulfur batteries

Toward practical lithium−sulfur (Li−S) batteries, there is a pressing need to improve the rate performance and longevity of cells. Herein, we report developing a cathode electrocatalyst Lu SA/NC, capable of accelerating sulfur redox kinetics with a high specific capacity of 1391.8 mAh g−1 at 0.1 C, and a low-capacity fading rate of 0.049 % per cycle over 1000 cycles even with a high sulfur loading (5.96 mg cm−2). The unparalleled cathodes are built upon the unique structure in which single-atoms of rare earth metals are doped in nitrogen-doped porous carbon (RM SAs/NC). The theoretical and experimental studies reveal that the rare earth Lu atom has an unrivaled adsorption capacity for polysulfides and can promote facile deposition and dissolution reactions in charge-discharge processes. The in-situ Raman experiments provide direct evidence for its promotion of polysulfide transformation to eliminate the shuttle effect. The theoretical calculations suggest that the presence of f-d-p hybridization enables accelerating sulfur reduction kinetics and enhancing lithium−sulfur battery performance. The strategic paradigm introduced in this study underscores significant practical potential in the exploration of rare earth single-atom catalysts for high performance Li−S batteries.

Building Li–S batteries with enhanced temperature adaptability via a redox-active COF-based barrier-trapping electrocatalyst

Covalent organic frameworks (COFs) are promising materials for mitigating polysulfide shuttling in lithium-sulfur (Li–S) batteries, but enhancing their ability to convert polysulfides across a wide temperature range remains a challenge. Herein, we introduce a redox-active COF (RaCOF) that functions as both a physical barrier and a kinetic enhancer to improve the temperature adaptability of Li–S batteries. The RaCOF constructed from redox-active anthraquinone units accelerates polysulfide conversion kinetics through reversible C=O/C-OLi transformations within a voltage range of 1.7 to 2.8 V (vs. Li+/Li), optimizing sulfur redox reactions in ether-based electrolytes. Unlike conventional COFs, RaCOF provides bidentate trapping of polysulfides, increasing binding energy and facilitating more effective polysulfide management. In-situ XRD and ToF-SIMS analyses confirm that RaCOF enhances polysulfide adsorption and promotes the transformation of lithium sulfide (Li2S), leading to better sulfur cathode reutilization. Consequently, RaCOF-modified Li–S batteries demonstrate low self-discharge (4.0% decay over a 7-day rest), excellent wide-temperature performance (stable from −10 to +60 °C), and high-rate cycling stability (94% capacity retention over 500 cycles at 5.0 C). This work offers valuable insights for designing COF structures aimed at achieving temperature-adaptive performance in rechargeable batteries.

In-situ Construction of an Alloy Hybrid Interface and Ultrathin ZnS Nanosheets Catalyst for Polysulfide by Trifunctional ZnI2 Electrolyte Additive for Li-S Batteries

Lithium-sulfur batteries (LSBs) are considered promising candidates for next-generation energy storage devices owing to their ultrahigh theoretical energy density. However, LSBs are hindered by uncontrollable lithium dendrite growth, polysulfides shuttle effects, and sluggish sulfur kinetics. Herein, this work develops a multifunctional ZnI2 electrolyte additive for LSB for local high concentration base electrolyte. At anode side, an LixZn alloy hybrid interface leading to planar deposited lithium is formed from the reaction between Li metal and the ZnI2 additive and reduction products of Li+ solvation shell of the electrolyte. Moreover, planar deposited lithium was confirmed by in-situ liquid transmission electron microscopy (TEM). For cathode side, Zn2+ under the drive of electric field prior react with lithium polysulfide to form ultrathin ZnS nanosheets exposed with (100) miller index serving as a catalyst to accelerate sulfur redox kinetics and inhibit polysulfides shuttling. Consequently, the LSB with ZnI2 additive exhibits a remarkable discharge capacity of 712 mA h g−1 at 0.5 C after 300 cycles and a superior rate capability of 674.9 mA h g−1 at 2 C. This work demonstrates that ZnI2 serves as a multifunctional electrolyte additive to simultaneously facilitate the sulfur redox kinetics, reduce the shuttle effect, and promote smooth Li growth.

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.

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.

In Situ Built ZnS/MXene Heterostructure by a Mild Method for Inhibiting Polysulfide Shuttle in Li-S Batteries.

With high specific surface area, excellent polysulfide conversion activity, and fast electron/ion transfer at the interface, MXene-derived heterostructures can be employed as catalysts for lithium-sulfur (Li-S) batteries to accelerate sulfur redox kinetics and suppress shuttle effect. However, the preparation of MXene-derived heterostructures often requires high-temperature reactions, which can easily lead to the oxidation of MXene and sacrifice the electrical conductivity. Herein, a catalytic two-dimensional heterostructure (ZnS/MXene) was successfully synthesized via a mild method. The MXene skeleton retains the original nanosheet structure without oxidation. The in situ-grown ZnS nanospheres prevent the restacking of MXene nanosheets, which not only increases the active sites, but also guarantees channels for the fast passage of lithium ions. The interfacial built-in electric field further promotes electron/ion migration, thereby expediting the polysulfide conversion and suppressing the shuttle effect. Consequently, the batteries using ZnS/MXene modified separators exhibit a high initial discharge capacity of 1230 mAh g-1 at 0.1 C and a low decaying rate of 0.082% per cycle after 500 cycles at 0.5 C. This work offers a reference for the fabrication of MXene-based heterostructure in Li-S batteries.

Dual-Functional Metal-Organic Framework Freestanding Aerogel Boosts Sulfur Reduction Reaction for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) technology stands out as a promising energy storage system. However, its journey toward practical implementation is hindered by sluggish sulfur reduction reaction (SRR) kinetics. A free-standing graphene aerogel (GA) combined with a copper-based metal-organic framework (MOF-GA) is fabricated as the sulfur host material for Li-S battery cathodes. The presence of MOF particles assumes a dual role, demonstrating its efficacy not only as a catalyst for the reduction reaction of graphene oxide (GO) but also as an electrochemical catalyst to promote sluggish SRR kinetics. The former amplifies electron transfer kinetics within the electrode, and the latter elevates the overall cell performance. Experimental results and theoretical calculations have proven the catalytic activity of MOF-GA electrodes, leading to a higher sulfur utilization of over 80% and a lower capacity decay of 0.082% per cycle. Under extreme conditions, the Li-S cells show a high initial specific capacity of 1113.0 mAh·g-1 under an elevated loading of 4.25 mg·cm-2 and a high sulfur fraction >70%. This study shows the effectiveness of the synergist effects of MOF particles within the GA framework in promoting the sulfur redox reaction in Li-S batteries.

Hollow bimetallic layered hydroxides nanocages/mxenes electrocatalysts as superior accelerators for boosting sulfur redox kinetics under high sulfur loadings

Addressing the challenge of designing a high sulfur loading cathode while ensuring rapid sulfur redox kinetics and minimizing lithium polysulfides (LiPSs) shuttling is crucial for achieving high-energy density lithium-sulfur batteries (LSBs). Herein, we design hollow bimetallic layered hydroxide nanocages/MXenes electrocatalysts (denoted as NiCo-LDHs@MXenes) as superior accelerators. The synergistic integration of NiCo-LDHs and MXenes substantially enhances the electronic conductivity and catalytic activity, thereby promoting fast LiPSs conversions and facilitating Li2S nucleation/decomposition within high sulfur loading cathodes. Consequently, the NiCo-LDHs@MXenes/S cathode with a sulfur loading of 2.4 mg cm−2 achieves a high specific capacity of 1174.6 mAh g−1 at 0.1 C after 100 cycles. Remarkably, it exhibits an ultrastable lifespan over 600 cycles with a minimal capacity decay of ∼ 0.062 % per cycle at 1.0 C. Even under a high sulfur loading of 7.5 mg cm−2 and lean electrolyte of 4.5 μL mg−1, it still maintains a high areal capacity of 6.02 mAh cm−2 after 100 cycles. These exceptional outcomes underscore the potential of bimetallic LDHs/MXenes as high-performance cathodes for LSBs, offering valuable insights into the design and application of multifunctional electrocatalysts for LSBs with remarkably long lifespans.

A Click Chemistry Strategy Toward Spin-Polarized Transition-Metal Single Site Catalysts for Dynamic Probing of Sulfur Redox Electrocatalysis.

Catalytic conversion of lithium polysulfides (LiPSs) is a crucial approach to enhance the redox kinetics and suppress the shuttle effect in lithium-sulfur (Li-S) batteries. However, the roles of a typical heterogenous catalyst cannot be easily identified due to its structural complexity. Compared with the distinct sites of single atom catalysts (SACs), each active site of single site catalysts (SSCs) is identical and uniform in their spatial energy, binding mode, and coordination sphere, etc. Benefiting from the well-defined structure, iron phthalocyanine (FePc) is covalently clicked onto CuO nanosheet to prepare low spin-state Fe SSCs as the model catalyst for Li-S electrochemistry. The periodic polarizability evolution of Fe-N bonding is probed during sulfur redox reaction by in situ Raman spectra. Theoretical analysis shows the decreased d-band center gap of Fe (Δd) and delocalization of dxz/dyz after the axial click confinement. Consequently, Li-S batteries with Fe SSCs exhibit a capacity decay rate of 0.029% per cycle at 2 C. The universality of this methodological approach is demonstrated by a series of M SSCs (M = Mn, Co, and Ni) with similar variation of electronic configuration. This work provides guidance for the design of efficient electrocatalysis in Li-S batteries.

Template‐Sacrificing Synthesis of Asymmetrically Coordinated Zn Single‐Atom Sites for High‐Performance Sodium–Sulfur Batteries

AbstractMetal single‐atom catalysts (SACs) are extensively investigated to accelerate the sulfur redox kinetics in room‐temperature sodium─sulfur (Na─S) batteries. Nevertheless, the influence of the structure symmetry of SACs center on the electrocatalytic mechanism and the precise pathway in which single‐atom active sites facilitate sodium polysulfides (Na2Sn) conversion remain unknown. To enable controlled construction of highly active single‐atom configuration, herein, Zn SACs with an asymmetrical Zn─N3O configuration are designed for sodium polysulfides conversion. Both theoretical and experimental explorations reveal that the Zn─N3O single‐atom center displays higher electrocatalytic activity for polysulfides conversion than the Zn─N4 single‐atom center. The N/O co‐coordination induces the localized charge at Zn single‐atom center, which strengthens the d‐p hybridization with Na2Sn and stretches Na─S bond length of Na2Sn, thus accelerating the sulfur redox reaction kinetics. Consequently, the as‐assembled Na─S batteries achieve a high capacity of 1016 mAh g−1 at 1.0 C with a capacity decay of 0.0186% per cycle over 1000 cycles. This work uncovers the subtle relationship between the electrocatalytic activity of species conversion and the local coordination environment of SACs, and offers a guidance for the design of efficient asymmetrical SACs for different catalysis applications.

Synergistic improvement of the sulfur redox reaction by MOF-driven dual-defect polyhedral Mn-doped Co1-xS embedded in an N-doped carbon composite host for practical lithium-sulfur batteries

In the quest for practical sulfur hosts for lithium-sulfur batteries, a novel approach has been delineated. By meticulously adjusting the Mn:Co (1:5/1:9/1:1) ratio and the sulfidation temperature, a series of nitrogen-doped carbon nanopolyhedron composites have been synthesized, denoted as 1:9 Mn-Co1-xS-NC@NC, 1:5 Mn-Co1-xS-NC@NC, 1:1 Mn-Co1-xS-NC@NC, and Co1-xS-NC@NC. These materials, inheriting the polyhedral shape and a novel cavity structure from their precursors, exhibit enhanced lithium polysulfide adsorption and catalytic activity due to the introduction of Mn heteroatoms and cobalt vacancies. The resultant S@1:9 Mn-Co1-xS-NC@NC cathode excels in electrochemical performance, delivering an initial discharge capacity of 999.37 mA h g−1 at 1 C, and sustaining 715.65 mA h g−1 over 100 cycles. Notably, at an elevated sulfur loading of 3.05 mg cm−2 (E/S, 14.5 uL g−1), the cathode retains an areal capacity of 3.24 cmmA h cm−2 (corresponding specific capacity of 1067.59 mA h g−1) after 61 cycles at 0.2 C. The synergistic effect of manganese dopants and cobalt vacancies confers superior adsorptive and catalytic properties, presenting a promising avenue for the development of sulfur host materials with tailored morphologies and defect-rich structures.

Bimetallic Coupling Strategy Modulating Electronic Construction to Accelerate Sulfur Redox Reaction Kinetics for High-Energy Flexible Li-S Batteries.

Lithium-sulfur (Li-S) batteries are considered the most promising energy storage battery due to their low cost and high theoretical energy density. However, the low utilization rate of sulfur and slow redox kinetics have seriously limited the development of Li-S batteries. Herein, the electronic state modulation of metal selenides induced by the bi-metallic coupling strategy is reported to enhance the redox reaction kinetics and sulfur utilization, thereby improving the electrochemical performance of Li-S batteries. Theoretical calculations reveal that the electronic structure can be modulated by Ni-Co coupling, thus lowering the conversion barrier of lithium polysulfides (LiPSs)and Li+, and the synergistic interaction between NiCoSe nanoparticles and nitrogen-doped porous carbon (NPC) is facilitating to enhance electron transport and ion transfer kinetics of the NiCoSe@NPC-S electrodes. As a result, the assembled Li-S batteries based on NiCoSe@NPC-S exhibit high capacities (1020mAhg-1 at 1C) and stable cycle performance (80.37% capacity retention after 500 cycles). The special structural design and bimetallic coupling strategy promote the batteries working even under lean electrolyte (7.2µLmg-1) with a high sulfur loading (6.5mgcm-2). The proposed bimetallic coupling strategy modulating electronic construction with N-doping porous carbon has jointly contributed the good redox reaction kinetics and high sulfur utilization.

Seeding Co Atoms on Size Effect‐Enabled V2C MXene for Kinetically Boosted Lithium–Sulfur Batteries

AbstractLithium‐sulfur (Li–S) batteries are facing a multitude of challenges, mainly pertaining to the sluggish sulfur redox kinetics and rampant lithium dendrite growth on the cathode and anode side, respectively. In this sense, MXene has shown conspicuous advantages in serving as a dual‐functional promotor for Li–S batteries throughout the morphologic engineering, but still suffers from poor electrocatalytic activity and insufficient lithophilic sites. Herein, atomically dispersed Co sites are seeded onto the size effect‐enabled V2C MXene spheres (Co‐VC), leading to the generation of unique coordination configurations and rich active sites. Electrochemical tests combined with synchrotron radiation X‐ray 3D nano‐computed tomography and theoretical calculations unravel that Co‐VC with optimal coordination environments simultaneously boost sulfur reaction kinetics and lithium nucleation. As a consequence, Li–S batteries with Co‐VC modified separator can sustain a stable operation over 700 cycles with negligible capacity decay at 1.0 C, and delivers an areal capacity of 9.0 mAh cm−2 and desired cyclic performance at a high sulfur loading of 7.6 mg cm−2 with a lean electrolyte dosage of 4.0 µL mgS−1 at 0.1 C. The work opens a new avenue for boosting atomic‐scale site design with the aid of 2D substrates toward pragmatic Li–S batteries.

Seasonal Sulfur Redox Cycling in Two Constructed Wetlands with Insight on How They Age.

Long-term metal remediation in wetland treatment systems (WTSs) involves facilitating dissimilatory sulfate reduction to produce sulfide and mineralize metals in deep sediments. We evaluated seasonal sulfur cycling in two constructed wetlands (Maintained WTS constructed in 2007, and the Unmaintained WTS constructed in 2000) on the Savannah River Site in Aiken, South Carolina, USA. Significant interactions in sulfide concentration were observed between sediment depth, season, and wetland (F = 4.64, df = 11, P = 3.28 × 10 - 5). In the Maintained WTS, dissimilatory sulfate reduction dominated the surface sediments during the warm season (0-2cm depth, t=-2.66, P = 9.70 × 10 - 3), unlike the Unmaintained system. Sulfate concentrations in pore waters increased in the warm season (F = 7.84, df = 1, P = 6.50 × 10 - 3), contrary to expectations. Sulfur limitation in the Unmaintained WTS during the warm season correlated with increased sulfur assimilation in giant bulrush. Lower sulfide concentrations in surface sediments of the Unmaintained WTS illustrated aging effects. The Maintained WTS shows potential for managing erosion, pH reduction, and sulfur limitation observed in the older Unmaintained WTS.

An anthraquinone derivative for modulating the energy levels of polysulfide molecular orbitals to enhance the kinetics of redox reactions

The shuttle effect of lithium polysulfides (LiPSs) and the slow kinetics of sulfur redox reactions severely hinder the commercialization of lithium-sulfur (Li–S) batteries. In this study, 2,6-dihydroxyanthraquinone (DHAQ) is absorbed onto the surface of carbon materials through π-π interactions to facilitate the adsorption and catalytic conversion of LiPSs. Electrostatic potential (ESP) results indicate that introducing hydroxyl groups into the molecule enhances the carbonyl group's ability to adsorb LiPSs and thereby facilitates the formation of covalent Li-O bonds for their immobilization. The interaction between DHAQ and LiPSs results in a complex with a higher energy level for the highest occupied molecular orbital (HOMO) and a lower energy level for the lowest unoccupied molecular orbital (LUMO). This leads to enhanced redox activity, which accelerates the kinetics of LiPSs conversion reactions. Consequently, the S@DHAQ/C composite demonstrates a capacity decay rate of just 0.040 % per cycle after 600 cycles at 1 C. At a sulfur loading of 5 mg cm−2, it retains an initial discharge specific capacity of 643 mAh g−1 at 0.2 C. This work introduces a novel approach to improving polysulfide adsorption capacity through organic molecules while also accelerating the kinetics of redox reactions.

P‐doped RuSe2 on Porous N‐doped Carbon Matrix as Catalysts for Accelerated Sulfur Redox Reactions

Monocomponent catalysts exhibit the limited catalytic conversion of polysulfides due to their intrinsic electronic structure, but their catalytic activity can be improved by introducing heteroatoms to regulate its electronic structure. However, the rational selection principles of doping elements remain unclear. Here, we are guided by theoretical calculations to select the suitable doping elements based on the balanced relationship between the adsorption strength of lithium polysulfides (LiPSs) and catalytic activity of lithium sulfide. We apply the screening method to develop a new catalyst of phosphorus doped RuSe2, manifesting the further enhanced conductivity compared with original RuSe2, facilitating charge transfer and further modulating the d–band center of RuSe2, thereby augmenting its effectiveness in interacting with LiPSs. Consequently, the assembled cell exhibits an areal capacity of 7.7 mAh cm–2, even under high sulfur loading of 8.0 mg cm–2 and a lean electrolyte condition (5.0 μL mg–1). This rational screening strategy offers a robust solution for the design of advanced catalysts in the field of lithium–sulfur batteries and potentially other domains as well.

P-doped RuSe2 on Porous N-Doped Carbon Matrix as Catalysts for Accelerated Sulfur Redox Reactions.

Monocomponent catalysts exhibit the limited catalytic conversion of polysulfides due to their intrinsic electronic structure, but their catalytic activity can be improved by introducing heteroatoms to regulate its electronic structure. However, the rational selection principles of doping elements remain unclear. Here, we are guided by theoretical calculations to select the suitable doping elements based on the balanced relationship between the adsorption strength of lithium polysulfides (LiPSs) and catalytic activity of lithium sulfide. We apply the screening method to develop a new catalyst of phosphorus doped RuSe2, manifesting the further enhanced conductivity compared with original RuSe2, facilitating charge transfer and further modulating the d-band center of RuSe2, thereby augmenting its effectiveness in interacting with LiPSs. Consequently, the assembled cell exhibits an areal capacity of 7.7 mAh cm-2, even under high sulfur loading of 8.0 mg cm-2 and a lean electrolyte condition (5.0 μL mg-1). This rational screening strategy offers a robust solution for the design of advanced catalysts in the field of lithium-sulfur batteries and potentially other domains as well.

Nitrogen-Doped Carbon and Metal-Nitrogen-Carbon Materials as Cathode Hosts for Li-S Batteries: Experimental Study and Mechanism Analysis.

Both nitrogen-doped carbon (NC) and metal-nitrogen-carbon (MNC) materials have been extensively investigated in lithium-sulfur batteries to alleviate the "shuttle effect". MNC are generally synthesized using NC as the parent material, wherein nitrogen atoms in NC serve as the "bridge" to coordinate with metal atoms. So far, an important scientific issue has not been settled: does the introduction of metal sites into NC certainly enhance the Li-S battery performance? In this work, NC and MNC materials derived from the same precursor, a nitrogen-rich porous polymer, are systematically compared as cathode hosts for Li-S battery through theoretical calculations and experimental investigation. Li-S cell with NC as the cathode sulfur host exhibits better cycle performance at low current densities (0.1 and 0.2C), whereas MNC materials predominate at higher current densities (such as 1C and 2C). Based on theoretical calculation and experimental results, it is concluded that the introduction of metal sites into NC through nitrogen bonding promoted the catalytic capability for faster sulfur redox reaction kinetics, whereas the adsorption energy toward polysulfides decreased. This work provides important guidance for more targeted design of advanced materials for lithium-sulfur battery application in the future.