Sulfur Evolution Research Articles

Interfacial synergy in twinborn CoS2/CoS1.097 heterojunction to promote sulfur conversion kinetics in lithium-sulfur batteries

The rational design of sulfur hosts is essential for mitigating the shuttle effect of lithium polysulfides (LiPSs) and improving the sluggish conversion kinetics of sulfur during multi-step phase transition. Herein, a twinborn CoS2/CoS1.097 heterojunction encapsulated in N-doped hollow carbon polyhedrons and in-situ generated CNTs (CoS2/CoS1.097@NC/CNT) was elaborately synthesized and utilized as the electrocatalyst in sulfur cathodes. The CoS2/CoS1.097 heterojunction provides abundant chemisorption sites that facilitate the formation of chemical bonds with polysulfides, thereby effectively adsorbing LiPSs. More importantly, the spontaneously generated internal electric field at the CoS2/CoS1.097 interface accelerates electron transfer, which promotes the reversible transformation between LiPSs and Li2S. Additionally, the hollow carbon polyhedrons and grafted CNTs not only effectively confine sulfur, but also provide extra buffer space for the sulfur evolution reaction. Benefiting from these characteristics, the battery assembled with CoS2/CoS1.097@NC/CNT/S cathode exhibits a remarkable initial capacity of 1454.4mAh/g at 0.1C), excellent rate capability of 674.7mAh/g at 4C, and outstanding capacity retention of 604.7mAh/g over 500 cycles at 2C (∼73.1 % of initial capacity).

Sulfur Distribution Analysis in Lithium−Sulfur Cathode via Confined Inverse Vulcanization in Carbon Frameworks

AbstractLithium–Sulfur (Li–S) batteries are promising energy storage devices due to their high theoretical energy density. However, challenges such as the shuttling effect and volume expansion have significantly hindered their cycle life and capacity retention. Furthermore, the complex kinetic pathways in Li–S batteries call for advanced characterization techniques to unravel underlying mechanisms. In this study, a hollow porous carbon (HPC) is used as a microreactor, where inverse vulcanization occurs between 1,3‐diisopropylbenzene (DIB) and sulfur (S8), resulting in the creation of three‐dimensionally interconnected and well‐distributed S‐DIB in carbon frameworks. As a result, the dual confinement strategy imparts Li–S coin cells with remarkable cycling stability and capacity retention, exhibiting an impressive capacity of 866 mAh g−1 when returning to 0.1 C after 100 cycles of rate capability tests. Particularly, the Energy‐selective Backscattered (EsB) assisted Scanning Electron Microscope (SEM) technique as a novel approach is introduced to distinguish different lengths of polysulfides. Their distribution is visualized in the cross‐section view of the electrode in a micrometer range. These EsB images provide concrete indications of the sulfur evolution process and explain the capacity degradation during cycling.

Chip−like high−entropy oxide catalysts enhance fast sulfur evolution reaction for long−life lithium−sulfur batteries

Many catalysts have shown excellent activity for the sulfur reduction reaction (SRR), but sluggish electrochemistry kinetics have hindered the development of lithium–sulfur batteries. It has been found that the activity of catalysts for the sulfur evolution reaction (SER) plays a crucial role in determining the overall reaction kinetics. To address this issue, the rational design of catalysts is crucial. Here, we proposed a popular rule to accelerate SER by using chip–like high–entropy perovskite oxide La0.7Sr0.3(Fe0.2Co0.2Ni0.2Zn0.2Mn0.2)O3-δ (LMO–HEO) as advanced electrocatalysts. The strong interaction between the adjacent metal atoms in different metals of LMO–HEO electrocatalysts could lead to a "cocktail effect", which not only greatly improved the catalytic capacity toward sulfur species, but also accelerated the oxidation reaction kinetics of Li2S. As a result, the S/La0.7Sr0.3(Fe0.2Co0.2Ni0.2Zn0.2Mn0.2)O3-δ cathodes delivered excellent cyclic stability with a capacity decay of only 0.025% after 1200 cycles at 2 C. This work has provided a rational design idea for new multifunctional electrocatalysts with high catalytic capacity.

Developing a Multifunctional Cathode for Photoassisted Lithium-Sulfur Battery.

Integration of solar cell and secondary battery cannot only promote solar energy application but also improve the electrochemical performance of battery. Lithium-sulfur battery (LSB) is an ideal candidate for photoassisted batteries owing to its high theoretical capacity. Unfortunately, the researches related the combination of solar energy and LSB are relatively lacking. Herein, a freestanding photoelectrode is developed for photoassisted lithium-sulfur battery (PALSB) by constructing a heterogeneous structured Au@N-TiO2 on carbon cloths (Au@N-TiO2/CC), which combines multiple advantages. The Au@N-TiO2/CC photoelectrode can produce the photoelectrons to facilitate sulfur reduction during discharge process, while generating holes to accelerate sulfur evolution during charge process, improving the kinetics of electrochemical reactions. Meanwhile, Au@N-TiO2/CC can work as an electrocatalyst to promote the conversion of intermediate polysulfides during charge/discharge process, mitigating induced side reactions. Benefiting from the synergistic effect of electrocatalysis and photocatalysis, PALSB assembled with an Au@N-TiO2/CC photoelectrode obtains ultrahigh specific capacity, excellent rate performance, and outstanding cycling performance. What is more, the Au@N-TiO2/CC assembled PALSB can be directly charged under light illumination. This work not only expands the application of solar energy but also provides a new insight to develop advanced LSBs.

3d‐Orbital High‐Spin Configuration Driven From Electronic Modulation of Fe3O4/FeP Heterostructures Empowering Efficient Electrocatalyst for Lithium−Sulfur Batteries

AbstractThe intricate lithium polysulfides (LiPSs) shuttle and uncontrollable lithium dendrite growth critically hinder the commercialization of lithium−sulfur (Li−S) batteries. The rational and orderly assignment of multi‐electron induced flow is the critical link in sulfer redox reaction. Herein, the yolk‐shell Fe3O4/FeP@C heterostructure nanoreactors are fabricated to modulate electronic structure, including spin‐related charge behavior and orbital orientation control, which can demonstrate the interaction between catalytic activity and spin‐state conformation. The orbital spin splitting of Fe3O4/FeP@C induces the electron transition from low‐spin to high‐spin, where the non‐degenerate orbitals contribute to energy level up‐shift, guiding electron migration from FeP to Fe3O4, and activating more electronic states in 3d orbitals. Spin polarization guides electron flow and induces sulfur closed‐loop conversion, which are confirmed by DFT simulations and in situ Raman. Hence, the electrochemical performances are remarkable at ultra‐high current density and sulfur loading. Even an initial specific capacity of 928.5 mAh g−1 of a Li−S pouch cell reveals the practical prospect of Fe3O4/FeP@C/PP separator. The Li//Li symmetric cell cycles steadily for 4000 h, confirming the interlayer simultaneously promotes sulfur evolution kinetics and sieves lithium ions. This work deciphers the principles of spin‐orbit coupling, achieving the topological modulation of “charge−spin−orbit” toward electrocatalysts.

Iron Production By Molten Sulfide Electrolysis

With urgency and incentives to cut CO2 emissions, alongside increasing demand for steel, there is a need for technologies that use solely electricity for iron ore reduction, eliminating the role of carbon as a reductant. Herein, we propose the electrolytic production of liquid cast iron using a novel sulfide route, molten sulfide electrolysis (MSE). The process operates using sulfide chemistry and an inert anode. Sulfides are well known from non-ferrous metallurgy1 and the exclusion of oxygen supports a virtual elimination of green-house gases(GHG) emissions from the reduction step. The electrolytic decomposition of iron sulfide into iron and elemental sulfur gas operates in a multi-component molten sulfide electrolyte. The underlying thermodynamics suggests the absence of trivalent iron species (Fe3+) in such conditions, supporting the reduction of only divalent iron (Fe2+) and reducing the energy need proportionally, as compared to other oxide-based routes. Iron sulfide deposits or tailings, as well as conventional iron oxide ores after sulfidation2 are some of the suitable feedstocks for MSE.Both thermal only, and galvanostatic electrochemical experiments were carried out on electrolyte droplets (~200mg) in a thermal imaging furnace, to confirm the electrolytic deposition of Fe and the evolution of sulfur in a 2-electrode set-up. Faradaic efficiency estimates based on mass-loss measurements – i.e. with respect to gaseous sulfur anodic evolution – are of the order of 90%. Key electrochemical attributes of MSE to be reported include impedance measurement at various fixed DC potentials, measurements at various current densities up to 2A/cm2, and the role of the total charge passed, to highlight the potential limitations observed in such an experimental set up. Characterization of the electrochemical deposits are also presented.

Coupled Ni─Co Dual-Atom Catalyst for Guiding Sulfur and Lithium Evolutions in Lithium-Sulfur Batteries.

The kinetically retarded sulfur evolution reactions and notorious lithium dendrites as the major obstacles hamper the practical implementation of lithium-sulfur batteries (LSBs). Dual metal atom catalysts as a new model are expected to show higher activity by their rational coupling. Herein, the dual-atom catalyst with coupled Ni─Co atom pairs (Ni/Co-DAC) is designed successfully by programmed approaches. The Ni─Co atom pairs alter the local electron structure and optimize the coordination configuration of Ni/Co-DAC, leading to the coupling effect for promoting the interconversion of sulfur and guiding lithium plating/striping. The LSB delivers a remarkable capacity of 818mA h g-1 at 3.0 C and a low degeneration rate of 0.053% per cycle over 500 cycles. Moreover, the LSB with a high sulfur mass loading of 6.1mg cm-2 and lean electrolyte dosage of 6.0µL mgS -1 shows a remarkable areal capacity of 5.7mA h cm-2.

Solubility evolution of elemental sulfur in natural gas with a varying H2S content.

The solubility variations of elemental sulfur are of great importance in the prevention of sulfur deposition during the development of high-sulfur gas formations. It has been observed that the solubility varies with H2S content, which is the main solvent of elemental sulfur in natural gas. Moreover, the addition of small amounts of CH4 and/or CO2 in H2S leads to a dramatic solubility reduction of which the mechanism remains unclear. Using a modified direct coexistence method, molecular dynamics simulations are conducted to uncover the molecular mechanism of the solubility reduction. The observed solubility variations with H2S content are reproduced, and the solubility reduction is interpreted by the antisolvent effect of CH4 and CO2. While the H2S content varies in a wide range in the known high-sulfur gas formation, our simulations provide useful information for controlling the sulfur deposition in gas development. Molecular dynamics simulations are carried out using the LAMMPS package. The initial models are constructed with the Packmol software. The Ballone and Jones' potential is used for S8, the Galliero's potential for H2S and CO2, and the transferable potentials for phase equilibria-united atom (TraPPE-UA) force field for CH4. The time step is set to 1fs, and the molecular trajectories of additional 2ns after equilibrium are collected for analysis.

Advancing lithium-sulfur battery efficiency: utilizing a 2D/2D g-C3N4@MXene heterostructure to enhance sulfur evolution reactions and regulate polysulfides under lean electrolyte conditions.

Lithium-sulfur batteries (LSBs) show promise for achieving a high energy density of 500 W h kg-1, despite challenges such as poor cycle life and low energy efficiency due to sluggish redox kinetics of lithium polysulfides (LiPSs) and sulfur's electronic insulating nature. We present a novel 2D Ti3C2 Mxene on a 2D graphitic carbon nitride (g-C3N4) heterostructure designed to enhance LiPS conversion kinetics and adsorption capacity. In a pouch cell configuration with lean electrolyte conditions (∼5 μL mg-1), the g-C3N4-Mx/S cathode exhibited excellent rate performance, delivering ∼1061 mA h g-1 at C/8 and retaining ∼773 mA h g-1 after 190 cycles with a Coulombic efficiency (CE) of 92.7%. The battery maintained a discharge capacity of 680 mA h g-1 even at 1.25 C. It operated reliably at an elevated sulfur loading of 5.9 mg cm-2, with an initial discharge capacity of ∼900 mA h g-1 and a sustained CE of over 83% throughout 190 cycles. Postmortem XPS and EIS analyses elucidated charge-discharge cycle-induced changes, highlighting the potential of this heterostructured cathode for commercial garnet LSB development.

Benzo-crown ether electrolyte additives in facilitating sulfur evolution and lithium anode stabilization for high-performance lithium–sulfur batteries

Dibenzo-24-crown-8 (D24C8), as a bifunctional additive, promoted sulfur species conversion kinetics and mitigated detrimental side reactions at the lithium anode caused by LiPSs.

Numerical investigation of boiler waterwall corrosion by integrated tube temperature prediction and sulfur evolution model

High temperature corrosion has become one of the leading causes of boiler waterwall tube failures because of the wide application of air-staged combustion in coal-fired boilers. High temperature corrosion is strongly affected by the H2S concentration and wall tube temperature distributions in the furnace. Particularly, the corrosion rate increases exponentially with the increase of tube temperature. However, by far most of the numerical studies on high temperature corrosion only considered the effects of H2S concentration while the critical effects of tube temperature were overlooked. Thus, this paper presents a comprehensive corrosion model that incorporates the key effects of both tube temperature and H2S concentration. Specifically, the tube temperature is predicted by a coupled combustion and hydrodynamic model that integrates the critical effects of both the boiler gas flow and steam flow on waterwall tube temperature. The H2S concentration is predicted by a sulfur evolution model describing the devolatilization process of coal sulfur species and their subsequent gaseous reactions. The tube temperature prediction model and H2S evolution model provide all the key parameters for accurate prediction of boiler waterwall corrosion. The corrosion model is applied to a 350 MW supercritical wall-fired boiler. The results show that the tube temperature varies significantly over the boiler waterwall, and hence, has significant impacts on the distribution of wall tube corrosion. Particularly, local high tube temperature zones could form on the waterwall areas of relatively low H2S concentration leading to substantially higher tube corrosion rates than the adjacent wall areas. The results demonstrate the importance of incorporating both the wall tube temperature and H2S concentration in the prediction of boiler waterwall corrosion.

Spontaneous Built-In Electric Field in C3N4-CoSe2 Modified Multifunctional Separator with Accelerating Sulfur Evolution Kinetics and Li Deposition for Lithium-Sulfur Batteries.

The discovery of the heterostructures that is combining two materials with different properties has brought new opportunities for the development of lithium sulfur batteries (LSBs). Here, C3N4-CoSe2 composite is elaborately designed and used as a functional coating on the LSBs separator. The abundant chemisorption sites of C3N4-CoSe2 form chemical bonding with polysulfides, provides suitable adsorption energy for lithium polysulfides (LiPSs). More importantly, the spontaneously formed internal electric field accelerates the charge flow in the C3N4-CoSe2 interface, thus facilitating the transport of LiPSs and electrons and promotingthe bidirectional conversion of sulfur. Meanwhile, the lithiophilic C3N4-CoSe2 sample with catalytic activity can effectively regulate the uniform distribution of lithium when Li+ penetrates the separator, avoiding the formation of lithium dendrites in the lithium (Li) metal anode. Therefore, LSBs based on C3N4-CoSe2 functionalized membranes exhibit a stable long cycle life at 1C (with capacity decay of 0.0819% per cycle) and a large areal capacity of 10.30mAhcm-2 at 0.1C (sulfur load: 8.26mgcm-2, lean electrolyte 5.4µLmgs -1). Even under high-temperature conditions of 60°C, a capacity retention rate of 81.8% after 100 cycles at 1C current density is maintained.

Breaking Barriers to High-Practical Li-S Batteries with Isotropic Binary Sulfiphilic Electrocatalyst: Creating a Virtuous Cycle for Favorable Polysulfides Redox Environments.

Investigations into lithium-sulfur batteries (LSBs) has focused primarily on the initial conversion of lithium polysulfides (LiPSs) to Li2 S2 . However, the subsequent solid-solid reaction from Li2 S2 to Li2 S and the Li2 S decomposition process should be equally prioritized. Creating a virtuous cycle by balancing all three chemical reaction processes is crucial for realizing practical LSBs. Herein, amorphous Ni3 B in synergy with carbon nanotubes (aNi3 B@CNTs) is proposed to implement the consecutive catalysis of S8(solid) → LiPSs(liquid) → Li2 S(solid) →LiPSs(liquid) . Systematic theoretical simulations and experimental analyses reveal that aNi3 B@CNTs with an isotropic structure and abundant active sites can ensure rapid LiPSs adsorption-catalysis as well as uniform Li2 S precipitation. The uniform Li2 S deposition in synergy with catalysis of aNi3 B enables instant/complete oxidation of Li2 S to LiPSs. The produced LiPSs are again rapidly and uniformly adsorbed for the next sulfur evolution process, thus creating a virtuous cycle for sulfur species conversion. Accordingly, the aNi3 B@CNTs-based cell presents remarkable rate capability, long-term cycle life, and superior cyclic stability, even under high sulfur loading and extreme temperature environments. This study proposes the significance of creating a virtuous cycle for sulfur species conversion to realize practical LSBs.

Unique Octupolar 2D‐Polymer Frameworks as Mixed Conductors and Metal‐Free Catalysts for Dual‐Promoted Li and S Electrochemistry: Multi‐regulation Role of Ethoxylation Chemistry

Here, we for the first time introduce ethoxylation chemistry to develop a new octupolar cyano‐vinylene‐linked 2D polymer framework (Cyano‐OCF‐EO) capable of acting as efficient mixed electron/ion conductors and metal‐free sulfur evolution catalysts for dual‐promoted Li and S electrochemistry. Our strategy creates a unique interconnected network of strongly‐coupled donor 3‐(acceptor‐core) octupoles in Cyano‐OCF‐EO, affording enhanced intramolecular charge transfer, substantial active sites and crowded open channels. This enables Cyano‐OCF‐EO as a new versatile separator modifier, which endows the modified separator with superior catalytic activity for sulfur conversion and rapid Li ion conduction with the high Li+ transference number up to 0.94. Thus, the incorporation of Cyano‐OCF‐EO can concurrently regulate sulfur redox reactions and Li‐ion flux in Li‐S cells, attaining boosted bidirectional redox kinetics, inhibited polysulfide shuttle and dendrite‐free Li anodes. The Cyano‐OCF‐EO‐involved Li‐S cell is endowed with excellent overall electrochemical performance especially large areal capacity of 7.5 mAh cm–2 at high sulfur loading of 8.7 mg cm–2. Mechanistic studies unveil the dominant multi‐promoting effect of the triethoxylation on electron and ion conduction, polysulfide adsorption and catalytic conversion as well as previously‐unexplored ‐CN/C‐O dual‐site synergistic effect for enhanced polysulfide adsorption and reduced energy barrier toward Li2S conversion.

Sulfur migration and distribution during pyrolysis of a typical Chinese pyrite-enriched coal

ABSTRACT Sulfur migration and distribution during pyrolysis of coal is quite complicated with the effect from different intertwined influencing factors, which requires extensive investigation. In this research, a typical Chinese pyrite-enriched coal was selected and pretreated through acid leaching combined with CrCl2 reduction. Thereby, minerals such as silicates and sulfates in the raw coal were effectively separated with the ash contents decreased from 37.74% to 0.57% while the inorganic sulfur was completely removed. Furthermore, programmed combined with isothermal pyrolysis of the selected coal and its two pretreated counterparts were conducted on the home-designed horizontal reactor to systematically ascertain the gaseous sulfur evolution. Possible sulfur formation pathways were revealed to explain the effect from the intertwined factors between the reaction temperature and the intrinsic factors as minerals distribution, different sulfur occurrences and their association with the organic matrix of coal. Finally, quantitative evaluation of the temperature effect on the sulfuric gases distribution and their yields was conducted with the total fraction of all the gaseous sulfur much decreasing from 5.6% to below 2.0% for the deashed and depyrited coal. Overall, through such a systematic investigation on the sulfur evolution from a typical pyrite-rich coal, comprehensive insights were obtained for future efficient sulfur control.

Molecular mechanism in the solubility reduction of elemental sulfur in H2S/CH4 mixtures: A molecular modeling study

The solubility evolution of elemental sulfur in sour gas is key to study the occurrence and inhibition of sulfur deposition in the exploitation of high-sulfur gas reservoirs. Elemental sulfur mainly dissolves in H2S, and its solubility decreases dramatically in the presence of methane. As both methane and H2S are the main components in high-sulfur gas, it is essential to understand the molecular mechanism of the solubility reduction in H2S/CH4 mixtures. Molecular dynamics simulations are carried out for the S8, H2S and CH4 mixtures to reproduce the solubility reduction upon methane addition, and then used to reveal the reduction mechanism at the level of intermolecular interaction. The simulations reveal that both the strong competitiveness and high collision probability of H2S–CH4 pairs reduce the average densities of H2S–S(S8) and H2S–H2S pairs, which reduce the sulfur solubility in a direct/indirect but cooperative way. The role of methane in the solubility reduction is then discussed and the molecular mechanism of sulfur dissolution and precipitation in the sour gasses is addressed.

Modelling the Mechanism of Sulphur Evolution in the Coal Combustion Process: The Effect of Sulphur–Nitrogen Interactions and Excess Air Coefficients

The efficient use of coal resources and the safe operation of coal-fired boilers are hindered by high-temperature corrosion caused by corrosive sulphur components. To predict the impact of sulphur–nitrogen interactions on sulphur’s evolution and its mechanism of action, a conventional sulphur component evolution model (uS–N) and an improved sulphur component evolution model (S–N) that considers sulphur–nitrogen interactions were proposed in the present study. The models were built using OpenFOAM–v8 software for the coal combustion process, and the generation of SO2, H2S, COS, and CS2 was simulated and analysed under different air excess coefficients. The simulations were conducted to analyse the patterns of SO2, H2S, COS, and CS2 generation at different air excess factors. The results show that, compared with the uS–N condition, the simulated values of coal combustion products (SO2, H2S, COS, and CS2) under the S–N condition were closer to the experimental values, and the errors of different sulphur components at the furnace exit were all less than 5%. As such, the S–N model can more accurately predict the evolution of sulphur components. In the simulation range, when the air excess factor increased from 0.7 to 0.9, the production rate of SO2 increased, while the production rates of corrosive sulphur components H2S, COS, and CS2 decreased significantly by 41.3%, 34.8%, and 53.8%, respectively. Further, the mechanism of the effect of sulphur–nitrogen interactions on the generation rates of different components was revealed at different air excess coefficients. Here, the effect of sulphur–nitrogen interactions on SO2 and COS was found to be more significant at smaller air excess coefficients, and the effect of sulphur–nitrogen interactions on H2S and CS2 was more significant at larger air excess coefficients. The present study can provide a theoretical basis for predicting the evolution of sulphur components during coal combustion and improving the high-temperature corrosion problems caused by such a process.

Accelerated Sulfur Evolution Reactions by TiS2/TiO2@MXene Host for High‐Volumetric‐Energy‐Density Lithium–Sulfur Batteries

AbstractThe poor cycling stability and low volumetric energy density of lithium–sulfur batteries compared with lithium‐ion batteries are hindering their practical applications. Here, it is demonstrated that a dense sulfur electrode containing heavy TiS2/TiO2@MXene heterostructures can tackle these issues. It is observed that the TiO2 part functionally anchors the lithium polysulfides through the strong chemical affinity, and the TiS2 part serves as an efficient electrocatalyst to enhance the kinetics of sulfur evolution reactions. Benefitting from these synergistic effects, the TiS2/TiO2@MXene heterostructures effectively suppress the shuttle effects, leading to superior cyclability of the sulfur cathode with a low capacity decay of 0.038% per cycle for 500 cycles at a current rate of 1 C. More encouragingly, a highly dense S/TiS2/TiO2@MXene cathode exhibits a high volumetric energy density of 2476 Wh L−1 (based on the volume of the composite) at a high sulfur mass loading of 7.5 mg cm−2 and lean electrolyte of 5 µL mg−1. The electrochemical performance is comparable to or even superior to the lithium‐ion and lithium–sulfur batteries reported in the literature. This study provides an effective strategy to design stable and high‐volumetric‐energy‐density lithium–sulfur batteries for practical energy storage applications.

Dual-Functional V2 C MXene Assembly in Facilitating Sulfur Evolution Kinetics and Li-Ion Sieving toward Practical Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are considered as one of the most promising candidates to achieve an energy density of 500Wh kg⁻1 . However, the challenges of shuttle effect, sluggish sulfur conversion kinetics, and lithium-dendrite growth severely obstruct their practical implementation. Herein, multiscale V2 C MXene (VC) with a spherical confinement structure is designed as a high-efficiency bifunctional promotor for the evolution of sulfur and lithium species in Li-S batteries. Combining synchrotron X-ray 3D nano-computed tomography (X-ray 3D nano-CT), small-angle neutron scattering (SANS), and first-principle calculations, it is revealed that the activity of VC can be maximized by tuning the scale, and the as-attained functions are conducted as follows: (i) the VC acts as the efficient lithium polysulfide (LiPS) scavenger due to the large number of active sites; (ii) the VC exhibits significantly improved electrocatalytic function for the Li2 S nucleation and decomposition reaction kinetics owing to the scale effect; and (iii) the VC can regulate the dynamic behavior of Li-ions and thus stabilize the lithium plating/stripping effectively on account of the unique ion-sieving effect.

Atomically Dispersed Fe–N4 and Ni–N4 Independent Sites Enable Bidirectional Sulfur Redox Electrocatalysis

Single-atom catalysts (SACs) with high atom utilization and outstanding catalytic selectivity are useful for improving battery performance. Herein, atomically dispersed Ni-N4 and Fe-N4 dual sites coanchored on porous hollow carbon nanocages (Ni-Fe-NC) are fabricated and deployed as the sulfur host for Li-S battery. The hollow and conductive carbon matrix promotes electron transfer and also accommodates volume fluctuation during cycling. Notably, the high d band center of Fe in Fe-N4 site demonstrates strong polysulfide affinity, leading to an accelerated sulfur reduction reaction. Meanwhile, Li2S on the Ni-N4 site delivers a metallic property with high S 2p electron density of states around the Femi energy level, enabling a low sulfur evolution reaction barrier. The dual catalytic effect on Ni-Fe-NC endows sulfur cathode high energy density, prolonged lifespan, and low polarization.