Application Of Li-S Batteries Research Articles

Ultra-Low Alginate-Based Multifunctional Composite Binders for Enhanced Mechanical, Electrochemical, and Thermal Performance of Li-S Batteries.

The practical application of Li-S batteries, which hold great potential as energy storage devices, is impeded by various challenges, such as capacity degradation caused volume change, polysulfide shuttling, poor electrode kinetics, and safety concerns. Binder plays a crucial role in suppressing volume change of cathode side, thereby enhancing the electrochemical performance of Li-S batteries. In this research, a novel network binder (SA-Co-PEDOT) composed of sodium alginate is presented, Co2+ ions as cross-linking agent and PEDOT as an electronic conductor. The theoretical analysis and experimental testing confirm that the SA-Co-PEDOT binder with synergistic combination of catalytic center and electron transfer network effectively mitigates large volumetric changes during cycling while simultaneously enhancing electrode kinetics through controlling the deposition morphology of sulfur end product and its nucleation and dissolution. As a result, it achieves a capacity of 844 mAh g-1 after 150 cycles at 0.2 C. Moreover, the electrode with SA-Co-PEDOT binder subjected a bending test maintains a capacity of 395 mAh g-1 after 500 cycles at 0.5 C, exhibiting an impressively low decay rate of only 0.11%. Even with an ultra-low content of 2 wt.% SA-Co-PEDOT binder, the electrode still maintains a capacity of 999.7 mAh g-1 after 100 cycles at 0.5 C.

Heteroelectrocatalyst MoS2@CoS2 modified separator for Li-S battery: Unveiling superior polysulfides conversion and reaction kinetics

Mitigating the shuttle effect of polysulfides and enhancing their conversion efficiency are critical challenges for the practical application of Li-S batteries. Herein, we present a novel MoS2@CoS2 heteroelectrocatalyst synthesized via a hydrothermal method, used to modify the separator for Li-S batteries. This innovative heterostructure combines the exceptional properties of metallic CoS2 and semiconductor MoS2, creating a synergistic effect that significantly improves electrochemical performance. The built-in electric field at the heterointerface promotes rapid charge transport and enhances surface reaction kinetics, effectively addressing polysulfide shuttle and sluggish redox kinetics. The Li-S battery with MoS2@CoS2 separator exhibits an impressive initial capacity of 1480 mAh g−1 at 0.1 C and maintains 811 mAh g−1 at 3 C, with long-term cycling stability showing a minimal decay rate of 0.05 % per cycle at 1 C. Even with high sulfur loading (6 mg cm−2) and a low electrolyte/sulfur ratio, the cell achieves a high reversible capacity of 4.5 mAh cm−2 at 0.2 C. The innovative approach of integrating semimetal-semiconductor heterointerfaces opens new avenues for the development of high-performance Li-S batteries, addressing critical challenges and paving the way for future technological advancements in the field.

Revealing a volcano correlation of sulfur reduction catalytic activity and elements doping in cobalt-based sulfides for Li-S batteries

The effective utilization of Li-S batteries still necessitates the incorporation of an efficient catalytic medium to address the challenges posed by shuttle effects and sluggish reaction kinetics. Furthermore, the structure-activity relationship of catalysts for the sulfur reduction reaction remains inadequately understood. In this study, we utilize Co9S8 as a template to investigate the correlation between the doping of co-periodic elements (Fe, Ni, Cu and Zn) and their catalytic effects on the sulfur reduction reaction. There is a “volcano peak” correlation between the catalytic performance and the type of doped elements from Fe to Zn, and research indicates that the Ni-doped Co9S8 (NCS) demonstrates superior performance compared to other samples. The NCS not only maintains the inherent advantages of Co9S8 but also effectively lowers the apparent activation energy necessary for Li-S batteries. Consequently, this enhancement facilitates a more rapid and complete conversion of soluble lithium polysulfides, thereby endowing Li-S batteries with an enhanced reaction kinetics. When the sulfur areal loading is elevated to 5.2 mg cm−2, the maximum areal capacity of the cell can attain 5.2 mAh cm−2 at 0.05 C. This work further substantiates the efficacy of the element doping strategy in enhancing the catalytic performance of reduction reaction catalysts, and it also offers significant insights or considerations for the development of practical catalysts, thereby facilitating the practical application of Li-S batteries.

Kinetics enhancement of an advanced separator modified by vanadium-based MXene for Li-S batteries

Li-S batteries are promising because of the ultrahigh theoretical energy density (2600 Wh kg−1), however the severe shuttle effect of polysulfides and hysteresis of reaction kinetics hinder the application of Li-S batteries. Hence, this work raises a vanadium-based MXene modified separator for Li-S batteries, which can effectively inhibit the irreversible loss of polysulfides and further accelerate their rapid conversion. In addition, the kinetic enhancement role of this functionalized separator is studied from the electrochemistry perspective. As expected, both the cyclic stability and rate performance of Li-S batteries with this advanced separator are significantly improved, which highlight the application prospect in the field of energy storage and conversion.

(Invited) Solid/Electrolyte Interface Under Confinement in Divalent Water-in-Salt Electrolytes

Concentrated aqueous electrolytes (water-in-salt electrolytes, WiSEs) have gained increasing attention in the last few years because they display much wider electrochemical stability windows (upwards of 3V) than the thermodynamic limit of water (1.23V), making them exciting candidates for a variety of electrochemical systems including aqueous batteries. Importantly, it is the ions directly at the electrode/electrolyte interface that are key to explaining this unexpected reactivity. The electrode/electrolyte interface is classically thought of as the electrical double layer (EDL), or the ion arrangement at an interface that builds up to neutralize the surface potential. WiSEs present very different EDL structures than do classical dilute electrolytes. However, most work has focused on monovalent WiSEs, primarily motivated by Li-battery applications using lithium bis(trifluoromethylsulphonyl)imide (LiTFSI).In this work, we aim to understand how divalent ions within the WiSE regime alter both the short-range and long-range signatures of the EDL under confinement. For most of the above applications, reactions occur within the pore-space of a porous electrode, which exhibit confined, overlapping EDLs. Therefore, we use confinement as a tool to probe both the short-range layering structure (<10 nm) and electrostatic decay length (~10-100 nm) away from a charged interface with Surface Forces Apparatus (SFA) measurements.Using WiSEs comprising LiTFSI, Zn(TFSI)2, and mixtures of the two salts, we first establish the bulk structure of these electrolytes using Wide Angle X-Ray Scattering and Raman Spectroscopy, which reveal that the anion and cation are closely associated in all electrolytes, regardless of cation valency. Additionally, clusters of ions are formed in all electrolytes, however, the clusters are suppressed with increasing divalent ion fraction. Under confinement, SFA results demonstrate that the thickness of the adsorbed layer of ions at a solid/electrolyte interface grows with increasing divalent ion fraction. Multiple interfacial layers are formed following this adlayer, and these layers seem dependent on anion size, rather than cation. Importantly, all electrolytes exhibit very long electrostatic decay lengths that are insensitive to valency. This work contributes significant fundamental understanding regarding the structure and charge-neutralization mechanism in this class of electrolytes both in the bulk and under confinement at an interface.

Spodumene nanosheets@ZrO2-SiO2 heterostructure nanofibers modified separator for long-cycle lithium-sulfur batteries

Lithium-sulfur batteries have become highly promising next-generation energy storage devices owing to their high theoretical capacity density, environmental friendliness, high cost-effectiveness, etc. Nevertheless, the commercial applications of Li-S batteries are severely hampered by the fatal shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish reaction kinetics. To address these issues, a unique modifying interlayer of ZrO2-SiO2 heterostructure nanofibers inlaid with spodumene nanosheets (Spodumene@ZrO2-SiO2) has been innovatively designed and facilely prepared. In the interlayer, ZrO2-SiO2 heterostructure nanofibers provide abundant catalytic active sites to promote the conversion of LiPSs to improve kinetics, and effectively anchor LiPSs to reduce the shuttle effect. Simultaneously, the natural spodumene nanosheets as Li+ sieves offer selective Li+ transfer channels to allow Li+ fast transportation, but physically hinder the transportation of LiPSs owing to their small-size channels, further suppressing the shuttle effect of LiPSs. As a result, only host-free sulfur cathode by using this interlayer modified separator exhibits an extremely low capacity loss rate of 0.077 % per cycle during 500 cycles under 1 C. Even at the 2 C current density, the cathode still maintains a discharge-specific capacity of 630 mAh g−1, demonstrating the effectiveness of this strategy. With the help of combination of DFT and BVS theoretical calculations with the sound experiments, it is proved that the synergistic effects among physically and chemically anchoring LiPSs and catalytic capacity for LiPSs conversion of ZrO2-SiO2 heterostructure nanofibers, the Li+ selective transport and blocking effect for LiPSs shuttling of the spodumene nanosheets jointly achieve excellent long-life stability of Li-S battery. This study provides valuable insight into the design and fabrication of innovative separators for highly stable Li-S batteries via a cost-effective and environmentally friendly approach.

Universal, minute-scale synthesis of transition metal compound nanocatalysts via graphene-microwave system for enhancing sulfur kinetics in lithium-sulfur batteries

The application of Li-S batteries on large scale is held back by the sluggish sulfur kinetics and low synthesis efficiency of sulfur host. In addition, the preparation of catalysts that promote polysulfide redox kinetics is complex and time-consuming, reducing the cost of raw materials in Li-S. Here, a universal synthetic strategy for rapid fabrication of sulfur cathode and metal compounds nanocatalysts is reported based on microwave heating of graphene. Heat-sensitive materials can achieve rapid heating due to graphene reaching 500 ℃ within 4 s via microwave irradiation. The MoP-MoS2/rGO catalyst demonstrated in this work was synthesized within 60 s. When used for catalysts for Li-S batteries whose graphene/sulfur cathodes were also synthesized by microwave heating, enhanced catalytic effect for sulfur redox reaction was verified via experimental and DFT theoretical results. Benefiting from fast redox reaction (MoP), smooth Li+ diffusion pathways (MoS2), and large conductive network (rGO), the assembled Li-S battery with MoP-MoS2/rGO-Add@CS displays a remarkable initial specific capacity, stable lithium anode and good cycle stability (in pouch cells) using this two-pronged strategy. The work provides a practical strategy for advanced Li-S batteries toward a wide range of applications.

Two-dimensional SnP3 monolayer for inhibiting the shuttle effect in lithium-sulfur batteries: A first-principles study

The problems of the shuttle effect and sluggish transformation kinetics of lithium polysulfides (LiPSs) severely inhibit the practical application of Li-S batteries. Exploring anchoring materials with catalytic properties is an effective way to overcome these obstacles. In this paper, the electrochemical performance of SnP3 monolayer as an anchoring material is explored by using first-principles calculations. SnP3 monolayer can effectively anchor soluble LiPSs under vacuum and solvent conditions, and provides abundant adsorption sites for anchoring multiple LiPSs. Importantly, the rate-limiting step has changed to the conversion of Li2S8 to Li2S6, suggesting that the monolayer can facilitate the conversion of LiPSs and inhibit their accumulation in the electrolyte. Furthermore, lower decomposition and diffusion barriers of Li2S effectively inhibit the volume expansion of Li-S batteries. Thus, SnP3 monolayer becomes a promising anchoring material with suitable catalytic properties. This work demonstrates the feasibility of SnP3 monolayer as an anchoring material and expands the membership of phosphide family for applications in the field of Li-S batteries.

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

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

Encapsulating Sulfur into a Gel-Derived Nitrogen-Doped Mesoporous and Microporous Carbon Sponge for High-Performance Lithium-Sulfur Batteries.

The practical application of Li-S batteries (LSBs) has long been impeded by the inefficient utilization of sulfur and slow kinetics. Utilizing conductive carbonaceous frameworks as a host scaffold presents an efficient and cost-effective approach to enhance sulfur utilization for redox reactions in LSBs. However, the interaction of pure carbon materials with lithium polysulfide intermediates (LiPSs) is limited to weak van der Waals forces. Hence, the development of an economical method for synthesizing heteroatom-doped carbon materials for sulfur fixation is of paramount importance. In this study, we introduce a hierarchical porous nitrogen-doped carbon sponge (NPCS) with an exceptionally high BET surface area of 3182.2 m2 g-1, achieved through a facile template-assisted polymerization method. The incorporation of inorganic salts, free radical polymerization, and deuteric freeze-drying techniques facilitates the formation of hierarchical pores within the NPCS. After sulfur fixation, the resulting S/NPCS electrode demonstrates remarkable electrochemical performance in LSBs. Specifically, it achieves an 80% sulfur utilization rate, maintains a high reversible specific capacity of 400 mA h g-1 even after 600 cycles at a demanding current density of 5.0 A g-1, and exhibits superior rate capability. It is believed that this work will inspire the rational design of cost-effective carbon-based electrodes for high-performance LSBs.

Preparing of N-P dual-doped auricularia auricula carbon host by yeast fermentation and its application in Li-S batteries

A nitrogen-phosphorus dual-doped auricularia auricula carbon (NP-AC) matrix was prepared through hydrothermal treatment using natural auricularia auricula as raw material and medium solution. Yeast was introduced and cultured by the auricularia auricula liquid medium. The NP-AC/S composite was prepared through further freeze-drying, carbonization, activation and compounding with sulfur procedures. The composition and microstructure of samples was characterized by X-ray diffraction (XRD), raman and X-ray photoelectron spectroscopy (XPS). The morphology was observed under scanning electron microscope (SEM) and transmission electron microscopy (TEM) method. The specific surface area was analyzed using nitrogen adsorption/desorption test. The weight ratio of sulfur was measured through thermogravimetric (TG) analysis. The original structure and composition of biomass were improved by yeast fermentation and the auricularia auricula block structure with low porosity was modified. The electrochemical performance of NP-AC/S composite in Li-S batteries was systematically explored. After 100 cycles at 0.2C current density, there was still nearly 1000 mAh g−1 reversible capacity, holding a capacity retention rate of more than 84 %. The cycle performance and rate performance were both far better than the ordinary activated carbon materials.

Enhanced polysulfide regulation of lithium-sulfur batteries by ZnS-SnO2 nano-heterostructures

Lithium–sulfur (Li–S) battery is recognized as the most promising next-generation energy storage system due to its high theoretical capacity and energy density. However, the shuttle effect of lithium polysulfides (LiPSs) and the sluggish electrochemical reaction kinetics severely hinder its practical application. In this study, a hierarchical porous carbon (HPC) conductive framework loaded with ZnS-SnO2 heterostructures (ZnS-SnO2/HPC) in situ was designed for application in Li-S batteries. The ZnS-SnO2/HPC combines the advantages of physical confinement, chemical anchoring, and rapid electron/ion migration to inhibit the shuttling of LiPSs while ensuring its rapid conversion, achieving effective regulation of the electrochemical behavior of LiPSs. The obtained lithium-sulfur battery has significantly improved electrochemical properties: high reversible capacity (868.2 mAh g−1 after 100 cycles at 0.2 C), excellent rate capacity (841.5 mAh g−1 at 3 C), and low self-discharge capacity loss (97% capacity retention after 5 days of standing). In addition, the synergistic effect also helps to improve the cycle stability, with a capacity fading rate of only 0.079% per cycle over 500 cycles at 1 C.

CAU-17 derived bismuth nanoparticles embedded in nitrogen doped carbon belts as catalyst layer on separator for high performance Li-S batteries

Sluggish polysulfide conversion (SPC) process combined with shuttling effect and poor electronic conductivity of sulfur become the main obstacles in hindering the commercial application of Li-S battery. In this study, to address these issues, CAU-17 derived bismuth nanoparticels embedded in nitrogen doped carbon belts is proposed as a catalyst layer on separator for high performance Li-S batteries. By incorporating the excellent electronic conductivity of bismuth metal nanoparticles, the abundant polar adsorption sites of nitrogen-doped carbon belts, and tailored adsorption space on such “metal-carbon hybrid architecture”, the promotion of the polysulfide nucleation as well as effective conversion efficiency in SPC process have been achieved. Density functional theory computation further confirms the enhanced adsorption energy of bismuth nanoparticles to dissolved polysulfides during SPC process. Benefitting from the unique architecture and rational catalytic design, the Li-S battery with bismuth nanoparticles embedded in nitrogen doped carbon belts modified separator possesses a high specific capacity of 1045 mAh g−1 at 0.2 C and maintains a satisfactory specific capacity of 612.8 mAh g−1 at 4.0 C. Simultaneously, the decent high-rate cycling stability is achieved after 500 cycles. This work deepens the understanding of designing a metallic-based electrocatalyst layer on separator for high performance Li-S battery.

Boosting Polysulfide Redox Kinetics by Temperature-Induced Metal-Insulator Transition Effect of Tungsten-Doped Vanadium Dioxide for High-Temperature Lithium-Sulfur Batteries.

The practical application of Li-S batteries is still severely restricted by poor cyclic performance caused by the intrinsic polysulfides shuttle effect, which is even more severe under the high-temperature condition owing to the inevitable increase of polysulfides' solubility and diffusion rate. Herein, tungsten-doped vanadium dioxide (W-VO2) micro-flowers are employed with first-order metal-insulator phase transition (MIT) property as a robust and multifunctional modification layer to hamper the shuttle effect and simultaneously improve the thermotolerance of the common separator. Tungsten doping significantly reduces the transition temperature from 68 to 35 °C of vanadium dioxide, which renders the W-VO2 easier to turn from the insulating monoclinic phase into the metallic rutile phase. The systematic experiments and theoretical analysis demonstrate that the temperature-induced in-suit MIT property endows the W-VO2 catalyst with strong chemisorption against polysulfides, low energy barrier for liquid-to-solid conversion, and outstanding diffusion kinetics of Li-ion under high temperatures. Benefiting from these advantages, the Li-S batteries with W-VO2 modified separator exhibit significantly improved rate and long-term cyclic performance under 50°C. Remarkably, even at an elevated temperature (80°C), they still exhibit superior electrochemical performance. This work opens a rewarding avenue to use phase-changing materials for high-temperature Li-S batteries.

Highly dispersed conductive and electrocatalytic mediators enabling rapid polysulfides conversion for lithium sulfur batteries

The practical application of Li-S batteries encounters hurdles in maintaining cycling durability and rate capability under realistic conditions. Electrostatic self-assembly stands as a captivating avenue for exploring new frontiers in nanoscale catalysis. Leveraging renewable bio-oil both as a carbon source and self-polymerization precursor, ultrafine Mo2C nanocrystals anchored on bio-oil-derived 3D hierarchical carbon matrix (Mo2C@BOC) are fabricated by a facile NaCl template-assisted electrostatic self-assembly and followed annealing procedure. Densely anchored ultrafine Mo2C nanocrystals, intertwined with highly conductive carbon nanosheets, unveil an enhanced exposure of catalytically active sites for lithium polysulfide immobilization, conversion, and supply amply nucleation sites to mediate the fast precipitation of Li2S2/Li2S. Attributed to these favorable features, Li-S cells based on the as-designed catalytic host attain satisfactory cyclability with a minimum capacity fading rate of 0.0144 % over 1000 cycles and excellent rate capability. Decent performance can be achieved even at a high sulfur loading of 8.0 mg cm−2 and a low electrolyte-to-sulfur ratio of 3.5 µL mg−1. This strategy for solving the shuttle effect under high sulfur loading provides a promising solution for the further development of high-performance Li-S batteries. This work provides a rational strategy for solving the shuttle effect under high sulfur loading and sheds light on the great potential of Mo2C@BOC for developing more practical Li-S batteries.

MoO2/t-C3N4 Heterogeneous Materials with Bidirectional Catalysis for the Rapid Conversion of S Species in Li-S Batteries.

Li-S batteries have drawn a lot of attention for their high theoretical specific capacity and significant economic benefits. However, the shuttle effect of polysulfides prevents them from being used widely. To tackle this difficulty, a heterogeneous structure based on tubular carbon nitride with evenly dispersed molybdenum dioxide nanoparticles (MoO2/t-C3N4) as the S host is constructed in this work. As a polar material with a large specific surface area, MoO2/t-C3N4 has a strong anchoring effect on polysulfide. Additionally, the heterogeneous material has excellent bidirectional catalytic ability for the redox process of S species based on the action of the built-in electric field formed by electron directional transfer. Not only does it improve the reaction kinetics of the redox process of the polysulfides but it also prevents polysulfides from accumulating on the surface of the modified material and deactivating it, further improving the utilization of the active material. Thus, MoO2/t-C3N4/S shows the high initial-discharge specific capacity of 812.7 mAh g-1 at the current density of 5C, and the Coulombic efficiency is maintained at more than 95% after 400 charge/discharge cycles. Moreover, MoO2/t-C3N4/S achieved a capacity retention of 89% after 100 cycles at the current density of 0.1C under the high S loading. Therefore, the research results of this work provide a trustworthy reference for the future commercial application of Li-S batteries.

Investigation of the Reaction Mechanism of All-Solid-State Lithium-Sulfur Batteries by Operando in Situ Raman Spectroscopy

In recent years, all-solid-state lithium-sulfur batteries (ASSLSBs) with sulfide-based solid electrolytes have become a leading energy storage system due to their high ionic conductivity, ultra-high energy density, high safety, and low cost. There have been many challenges with the practical applications of Li-S batteries, however, as a result of the sluggish redox kinetics of lithium polysulfide (LPS) and its shuttling effects. Single-atom catalysts (SACs) with atomically dispersed metal-based sites have proven to be promising electrocatalysts in Li-S batteries. To construct the ASSLSBs, we design and develop MoS2/SnS2 and Fe SACs with MoS2/SnS2 cathodes, Li5.4PS4.4Cl1.6 sulfide-based solid electrolytes, and Li-In anode. In the current study, in situ Raman spectroscopy is used to determine the LPS species in the sulfur cathode with SACs and without SACs during the ASSLSBs cycling. The aim is to understand the charge-discharge mechanism and the influence of SACs on the dissolution of sulfur and poly-sulfides. As compared to the MoS2/SnS2 cathode, the Fe@MoS2/SnS2 cathode exhibit the highest catalytic LPS conversion. In addition, the Fe@MoS2/SnS2 cathode delivers a high discharge capacity and long-cycling performance with high coulombic efficiency in ASSLSBs. In operando in situ Raman studies, SACs provide important new insights into the charge-discharge reaction mechanism for the next generation of ASSLSBs.

A multifunctional LaFeO3 nanocages modified separator for propelling polysulfides chemisorption and catalytic conversion in Li-S batteries

The sluggish reaction kinetics of sulfur and the shuttle effect of intermediate polysulfides are the thorny issues for the commercialization of Li-S batteries. Commercial polypropylene separators cannot prevent the shuttling of polysulfides due to their large porosity. Therefore, the development of a novel type of separator can efficiently prohibit the transmission of polysulfides, will be beneficial to the practical application of Li-S batteries. Herein, we report a commercial membrane modified with perovskite-type LaFeO3 nanocages to block the transportation of polysulfides. Researches show that the modified multifunctional separators can not only effectively inhibit the shuttle of polysulfides, but also accelerate the reaction kinetics between S and Li2S. The electrochemical performance is greatly improved, which can be mirrored in the rate performance: 689.3 mA h g−1at 4C, and cycling performance with the capacity decay rate of only 0.0585% per cycle for 1000 cycles at 1C. More significantly, the considerable electrochemical performance is still hold under the harsh condition of lean electrolyte.

High loading atomically distributed Fe asymmetrically coordinated with pyridinic and pyrrolic N on porous N-rich carbon matrix driving high performance of Li-S battery

The practical application of Li-S battery is severely hampered by the sluggish sulfur-related redox reaction (SROR) kinetics along with lithium polysulfides (LiPSs) shuttle effect, advanced single-atom catalyst (SAC) is pursued to improve the SROR conversion capability. Herein, a novel SAC possessing of high loading (3.02 wt%) atomically dispersed Fe five-coordinated with pyridinic and pyrrolic N anchored on porous N-rich (16.4 at.%) carbon matrix is obtained. The resultant Fe-N5/NC SAC has a high Brunauer-Emmett-Teller surface area of 523 m2 g−1. The unique asymmetrical Fe-N5 sites in Fe-N5/NC are identified by spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscope, X-ray photoelectron spectroscope, synchrotron X-ray absorption spectroscopy, density functional theory calculation, etc. The experimental and theoretical results demonstrate that the Fe-N5/NC SAC not only exhibits strong adsorption for LiPSs, but also provides a significant electrocatalytic effect on the SROR in Li-S battery. A high initial capacity of 1519 mAh g−1 was obtained at a current density of 0.1 C for the Li-S battery based on the Fe-N5/NC modified separator. An ultralong life of 2000 cycles was achieved for the Li-S battery, which has good initial capacities of 1030 mAh g−1 and 883 mAh g−1 with low decay rates of 0.032% and 0.031% per cycles at 1 C and 2 C, respectively.

Spherical Sulfur-Infiltrated Carbon Cathode with a Tunable Poly(3,4-ethylenedioxythiophene) Layer for Lithium-Sulfur Batteries.

Li-S batteries have received significant attention owing to their high energy density, nontoxicity, low cost, and eco-friendliness. However, the dissolution of lithium polysulfide during the charge/discharge process and its extremely low electron conductivity hinder practical applications of Li-S batteries. Herein, we report a sulfur-infiltrated carbon cathode material with a spherical morphology and conductive polymer coating. The material was produced via a facile polymerization process that forms a robust nanostructured layer and physically prevents the dissolution of lithium polysulfide. The thin double layer composed of carbon and poly(3,4-ethylenedioxythiophene) provides sufficient space for sulfur storage and effectively prevents the elution of polysulfide during continuous cycling, thereby playing an essential role in increasing the sulfur utilization rate and significantly improving the electrochemical performance of the battery. Sulfur-infiltrated hollow carbon spheres with a conductive polymer layer demonstrate a stable cycle life and reduced internal resistance. The as-fabricated battery demonstrated an excellent capacity of 970 mA h g-1 at 0.5 C and a stable cycle performance, exhibiting ∼78% of the initial discharge capacity after 50 cycles. This study provides a promising approach to significantly improve the electrochemical performance of Li-S batteries and render them as valuable and safe energy devices for large-scale energy storage systems.