Sulfur Redox Reactions Research Articles

Electronic Modulation and Symmetry‐Breaking Engineering of Single‐Atom Catalysts Driving Long‐Cycling Li−S Battery

AbstractDeveloping efficient and durable single‐atom catalysts is vitally important for the sulfur redox reaction (SROR) in Li−S battery, while it remains enormous challenging. Herein, undercoordinated Ni−N3 moieties anchored on N,S‐codoped porous carbon (Ni−NSC) is obtained to enhance the SROR. The experiments and theoretical calculations indicate that the symmetry‐breaking charge transfer in Ni single‐atom catalyst originates from tuning effect of sulfur atoms mediated Ni−N3 moieties, which can both facilitate the chemical adsorption by formation of N−Ni⋅⋅⋅Sn2−, and achieve a rapid redox conversion of polysulfides because of the enhanced electron transfer. As results, the Ni−NSC based Li−S battery delivers a very high initial reversible capacity (1025 mAh g−1 at 1 C), as well as outstanding cycling‐stability for 2400 cycles at 2 C and 3 C, respectively. Noteworthy, the areal capacity can reach 7.8 mAh cm−2 at 0.05 C and a retention capacity of 4.7 mAh cm−2 after 100 cycles at 0.2 C for Ni−NSC based Li−S battery with sulfur loading of 5.88 mg cm−2. This work provides profound insight for rational optimizing microscopic electronic density of active site to promoting SROR in metal‐sulfur batteries.

Highly Solvating Electrolytes with Core‐Shell Solvation Structure for Lean‐Electrolyte Lithium‐Sulfur Batteries

The practical energy density of lithium‐sulfur batteries is limited by the low sulfur utilization at lean electrolyte conditions. The highly solvating electrolytes (HSEs) promise to address the issue at harsh conditions, but the conflicting challenges of long‐term stability of radical‐mediated sulfur redox reactions (SRR) and the poor stability with lithium metal anode (LMA) have dimmed the efforts. We now present a unique core‐shell solvation structured HSE formulated with classical ether‐based solvents and phosphoramide co‐solvent. The unique core‐shell solvation structure features confinement of the phosphoramide in the first solvation shell, which prohibits severe contact reactions with LMA and endows prolonged stability for [S3]•– radical, favoring a rapid radical‐mediated solution‐based SRR. The cell with the proposed electrolyte showing a high capacity of 864 mA h gsulfur−1 under high sulfur loading of 5.5 mgsulfur cm−2 and low E/S ratio of 4 µL mgsulfur−1. The strategy further enables steady cycling of a 2.71‐A h pouch cell with a high specific energy of 307 W h kg−1. Our work highlights the fundamental chemical concept of tuning the solvation structure to simultaneously tame the SRR and LMA stability for metal‐sulfur batteries wherein the electrode reactions are heavily coupled with electrolyte chemistry.

Highly Solvating Electrolytes with Core-Shell Solvation Structure for Lean-Electrolyte Lithium-Sulfur Batteries.

The practical energy density of lithium-sulfur batteries is limited by the low sulfur utilization at lean electrolyte conditions. The highly solvating electrolytes (HSEs) promise to address the issue at harsh conditions, but the conflicting challenges of long-term stability of radical-mediated sulfur redox reactions (SRR) and the poor stability with lithium metal anode (LMA) have dimmed the efforts. We now present a unique core-shell solvation structured HSE formulated with classical ether-based solvents and phosphoramide co-solvent. The unique core-shell solvation structure features confinement of the phosphoramide in the first solvation shell, which prohibits severe contact reactions with LMA and endows prolonged stability for [S3]•- radical, favoring a rapid radical-mediated solution-based SRR. The cell with the proposed electrolyte showing a high capacity of 864 mA h gsulfur-1 under high sulfur loading of 5.5 mgsulfur cm-2 and low E/S ratio of 4 µL mgsulfur-1. The strategy further enables steady cycling of a 2.71-A h pouch cell with a high specific energy of 307 W h kg-1. Our work highlights the fundamental chemical concept of tuning the solvation structure to simultaneously tame the SRR and LMA stability for metal-sulfur batteries wherein the electrode reactions are heavily coupled with electrolyte chemistry.

HighSpin-State Modulation of Catalytic Centers by Weak Ligand Field for Promoting Sulfur Redox Reaction in Lithium-Sulfur Batteries.

The spin state of transition-metal compounds in lithium-sulfur batteries (LSBs) significantly impacts the electronic properties and the kinetics of sulfur redox reactions (SRR). However, accurately designing the spin state remains challenging, which is crucial for understanding the structure-performance relationship and developing high-performance electrocatalysts. Herein, the CoF2, specifically the Co2+ with 3d7 electrons in a high-spin state distribution (t2g5eg2), were tailored predictably for the first time through the weak coordination field effect of the F element. Both DFT calculations and experimental results confirm that the spin state of Co2+ transitions from low- to high-spin configurations and strongly interacts with sulfur species through Co-S and Li-F bonds during the SRR process. This interaction weakens the S-S bond, promoting its facile cleavage from both ends while also facilitating the rapid and uniform nucleation of Li2S2/Li2S, thus resulting in LSBs with a capacity of 447.7 mAh g-1 at 10 C rates and stable cycling for 1000 cycles, with an acceptable practical capacity of 585 mAh g-1 at a high sulfur loading mass of 10 mg cm-2. This work achieves rational control of the active Co2+ d electron state through the field effect and enriches the application of spin control to accelerate SRR in LSBs.

Origin of the High Catalytic Activity of MoS2 in Na-S Batteries: Electrochemically Reconstructed Mo Single Atoms.

Room-temperature sodium-sulfur (RT Na-S) batteries with high energy density and low cost are considered promising next-generation electrochemical energy storage systems. However, their practical feasibility is seriously impeded by the shuttle effect of sodium polysulfide (NaPSs) resulting from the sluggish reaction kinetics. Introducing a suitable catalyst to accelerate conversion of NaPSs is the most used strategy to inhibit the shuttle effect. Traditional catalytic approaches often want to avoid the irreversible phase transition of the catalyst at a deep discharge. On the contrary, here, we leverage the intrinsic structural tunability of the MoS2 catalyst in the opposite direction and innovatively propose a voltage modulation strategy for in situ generation of trace Mo single atoms (MoSAC) during the first charge-discharge process, leading to the formation of highly active catalytic phases (MoS2/MoSAC) through the self-reconstruction. Theoretical calculations reveal that the incorporation of MoSAC modulates the electronic structure of the Mo d-band center, which not only effectively promotes the d-p orbital hybridization but also accelerates the catalytic intermediate desorption by the bonding transition, the dynamic single-atom synergistic catalytic mechanism enhances the adsorption response between the metal active site and NaPSs, which significantly improves the sulfur redox reaction (SRR), and the initial capacity of the MoS2/MoSAC/CF@S cell at 0.2 A g-1 is increased by 46.58% compared to that of the MoS2/CF@S cell. The discovery of the MoS2/MoSAC/CF catalyst provides new insights into adjusting the structure and function of transition metal disulfide catalysts at the atomic scale, offering hope for the development of high-specific-energy RT Na-S batteries.

High Spin‐State Modulation of Catalytic Centers by Weak Ligand Field for Promoting Sulfur Redox Reaction in Lithium‐Sulfur Batteries

High Spin‐State Modulation of Catalytic Centers by Weak Ligand Field for Promoting Sulfur Redox Reaction in Lithium‐Sulfur Batteries

Electronic Modulation and Symmetry-Breaking Engineering of Single-Atom Catalysts Driving Long-Cycling Li-S Battery.

Developing efficient and durable single-atom catalysts is vitally important for the sulfur redox reaction (SROR) in Li-S battery, while it remains enormous challenging. Herein, undercoordinated Ni-N3 moieties anchored on N,S-codoped porous carbon (Ni-NSC) is obtained to enhance the SROR. The experiments and theoretical calculations indicate that the symmetry-breaking charge transfer in Ni single-atom catalyst originates from tuning effect of sulfur atoms mediated Ni-N3 moieties, which can both facilitate the chemical adsorption by formation of N-Ni⋯Sn2-, and achieve a rapid redox conversion of polysulfides because of the enhanced electron transfer. As results, the Ni-NSC based Li-S battery delivers a very high initial reversible capacity (1025 mAh g-1 at 1 C), as well as outstanding cycling-stability for 2400 cycles at 2 C and 3 C, respectively. Noteworthy, the areal capacity can reach 7.8 mAh cm-2 at 0.05 C and a retention capacity of 4.7 mAh cm-2 after 100 cycles at 0.2 C for Ni-NSC based Li-S battery with sulfur loading of 5.88 mg cm-2. This work provides profound insight for rational optimizing microscopic electronic density of active site to promoting SROR in metal-sulfur batteries.

Nanosized CeO2C2 with rich oxygen vacancies embedded in hollow mesoporous carbon as a multifunctional sulfur-loaded matrix for lithium-sulfur batteries

The innovative structural and compositional design of sulfur-loaded matrices is an effective strategy to improve the performance of lithium-sulfur batteries (LSBs). Herein, nanosized CeO2C2 with rich oxygen vacancies embedded in hollow mesoporous carbon composites (HMC/CeO2C2) were synthesized by hydrothermal and annealing reduction processes. This structure has several advantages: the large specific surface area and mesoporous carbon walls facilitate sulfur penetration and electron/ion transport; the abundant mesopores and hollow inner cavities provide the structural basis for sulfur storage and buffer its volume expansion; the oxygen vacancy-rich CeO2C2 nanoparticles grown in situ in HMC and in close contact with carbon form an electrically favorable CeO2C2/C heterointerface as an efficient catalyst, which is conducive to catalyzing the redox reaction of sulfur. Consequently, the retention capacity of the HMC/CeO2C2/S electrode is 728 mAh g−1 after 500 cycles at 0.5 C with a decay rate of 0.056 % per cycle, and it maintains a high reversible area capacity of 3.18 mAh cm−2 and excellent cycling performance even under a high sulfur loading of 4.7 mg cm−2. It provides an idea for the development of multifunctional sulfur-loaded materials with high sulfur loading, high conductivity, and high catalytic activity.

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.

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.

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.

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.

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.

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.

Remediation of shuttle effect in a Li-sulfur battery via a catalytic pseudo-8-electron redox reaction at the sulfur cathode

A catalytic pseudo-8-electron redox reaction of sulfur is achieved by facilitating the disproportionation of high-order polysulfide ions in a Li-Sulfur battery. Electrochemically generated polysulfide ions (Sx2-, where 3 < x < 7) undergo rapid disproportionation into elemental sulfur (S8) and Li2S2, catalyzed by a bifunctional carbon host/catalyst. The overall catalytic redox reaction at the sulfur cathode is represented as S8+8Li++8e⇌4Li2S2. In contrast to physical or chemical confinement methods for polysulfide ions, this approach remediates the shuttle effect by swiftly converting soluble polysulfides in the electrolyte to elemental sulfur and insoluble Li2S2 within the cathode matrix. As a result, the adverse chemical interaction between dissolved polysulfides and the Li anode is mitigated.