Cathode For Lithium-sulfur Batteries Research Articles

From industrial by-products to high-value materials: synthesizing sulfur-rich polymers for lithium–sulfur battery cathodes from the C5 fraction and sulfur

Sulfur-rich polymers synthesized from the C5 fraction via inverse vulcanization exhibit strong thermal stability and electrochemical performance, making them promising candidates for cost-effective lithium–sulfur battery cathodes.

Anionic Doping in Layered Transition Metal Chalcogenides for Robust Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are among the most promising next-generation energy storage technologies. However, a slow Li-S reaction kinetics at the LSB cathode limit their energy and power densities. To address these challenges, this study introduces an anionic-doped transition metal chalcogenide as an effective catalyst to accelerate the Li-S reaction. Specifically, a tellurium-doped, carbon-supported bismuth selenide with Se vacancies (Te-Bi2Se3-x@C) is prepared and tested as a sulfur host in LSB cathodes. X-ray absorption and in-situ X-ray diffraction analyses reveal that Te doping induces lattice distortions and modulates the local coordination environment and electronic structure of Bi atoms to promote the catalytic activity toward the conversion of polysulfides. Additionally, the generated Se vacancies alter the electronic structure around atomic defect sites, increase the carrier concentration, and activate unpaired cations to effectively trap polysulfides. As a result, LSBs based on Te-Bi2Se3-x@C/S cathodes demonstrate outstanding specific capacities of 1508 mAh·g-1 at 0.1C, excellent rate performance with 655 mAh·g-1 at 5C, and near-integral cycle stability over 1000 cycles. Furthermore, under high sulfur loading of 6.4 mg·cm-2, a cathode capacity exceeding 8 mAh·cm-2 is sustained at 0.1C current rate, with 6.4 mAh·cm-2 retained after 300 cycles under lean electrolyte conditions (6.8 μL·mg-1).

Anionic Doping in Layered Transition Metal Chalcogenides for Robust Lithium‐Sulfur Batteries

Lithium‐sulfur batteries (LSBs) are among the most promising next‐generation energy storage technologies. However, a slow Li‐S reaction kinetics at the LSB cathode limit their energy and power densities. To address these challenges, this study introduces an anionic‐doped transition metal chalcogenide as an effective catalyst to accelerate the Li‐S reaction. Specifically, a tellurium‐doped, carbon‐supported bismuth selenide with Se vacancies (Te‐Bi2Se3‐x@C) is prepared and tested as a sulfur host in LSB cathodes. X‐ray absorption and in‐situ X‐ray diffraction analyses reveal that Te doping induces lattice distortions and modulates the local coordination environment and electronic structure of Bi atoms to promote the catalytic activity toward the conversion of polysulfides. Additionally, the generated Se vacancies alter the electronic structure around atomic defect sites, increase the carrier concentration, and activate unpaired cations to effectively trap polysulfides. As a result, LSBs based on Te‐Bi2Se3‐x@C/S cathodes demonstrate outstanding specific capacities of 1508 mAh·g‐1 at 0.1C, excellent rate performance with 655 mAh·g‐1 at 5C, and near‐integral cycle stability over 1000 cycles. Furthermore, under high sulfur loading of 6.4 mg·cm‐2, a cathode capacity exceeding 8 mAh·cm‐2 is sustained at 0.1C current rate, with 6.4 mAh·cm‐2 retained after 300 cycles under lean electrolyte conditions (6.8 μL·mg‐1).

Effect of Carbon Morphology and Slurry Formulation in Sulfur Cathode for Li-S Batteries

The performance of Lithium-Sulfur (Li-S) batteries is significantly influenced by material selection and manufacturing processes, with conductive carbon and slurry formulation playing crucial roles. In this study, the impact of carbon morphology and solvent/solid ratio in slurry preparation on microstructure and electrochemical performance of sulfur cathodes was investigated. Various carbon structures, such as nanotubes, sheets, and particles, were explored, and the solvent volume was adjusted to assess their effects on electrode architecture and electrochemical performance. Our findings demonstrate that the binder dissolution process and consequent electrode architecture and performance are highly influenced by both the carbon structure and slurry solvent volume. Furthermore, it was observed that, contrary to common assumption, advanced carbon structures are not necessary for enhanced capacity and durability of Li-S cathodes. Accordingly, the best cycling durability was achieved by optimizing the slurry with 300 μL/mgPVDF of NMP solvent and using Ketjen black as the conductive carbon, resulting in an initial capacity of 1029 mAh gS −1, with a retention of 830 mAh gS −1 after 500 cycles. These results, obtained at a high areal loading of 4.5 mgS cm−2, demonstrate the commercial potential of the proposed electrode formulation and processing method without reliance on advanced materials or techniques.

Optical and X-Ray Absorption Interrogation of Selenium-Based Redox in Carbon Nanofoam Supported SxSey Cathodes

Sulfur-based batteries have emerged as a leading contender for next-generation energy storage owing to their high redox capacity and the global availability of elemental sulfur. Yet the electronically insulating nature of sulfur limits the applicability of this battery chemistry. Redox kinetics are enhanced by coating sulfur onto a conductive, porous carbon scaffold1 and atomically mixing with selenium.2 Electrochemical discharge of S/Se blends exhibit additional voltage plateaus compared to a pure S cathode and in-situ optical microscopy identifies a more direct reaction pathway with less active material dissolution.3 Lab scale in-operando X-ray absorption spectroscopy reveals shifts in the Se K-edge correlated with features in electrochemical charge-discharge profiles, providing critical insights on the redox mechanism in nanocomposites of sulfur and selenium.1. Neale, Z.G.; Lefler, M.J.; Long, J.W.; Rolison, D.R.; Sassin, M.B.; Carter, R.; Freestanding Carbon Nanofoam Papers with Tunable Porosity as Lithium-Sulfur Battery Cathodes. Nanoscale, 2023, 15, 16924-16932.2. Deblock, R.H.; Lefler, M..J.; Neale, Z.G.; Love, C.T.; Long, J.W.; Carter, R.; Optical and X-ray Absorption Interrogation of Selenium-based Re-dox in Li-SxSey batteries, Energy Advances, 2024, 2024, 3, 424-429.3. Carter, R.; NewRingeisen, A.; Reed, D.; Atkinson, R.W.; Mukherjee, P.P.; Love, C.T.; Optical Microscopy Reveals the Ambient Sodium Sulfur Discharge Mechanism, ACS Sustainable Chem. Eng. 2021, 9, 1, 92–100.

Atomic substitution engineering-induced domino synergistic catalysis in Li-S batteries

Atomic substitution engineering is considered as effective strategy to activate the basal plane of molybdenum disulfide (MoS2) which has been demonstrated effective catalytic cathode in lithium-sulfur (Li-S) batteries. Rationally designing atomic substitution structure is vital to figure out the origin of catalytic activity in doped-MoS2 based catalytic cathodes. Herein, an “adjacent period, adjacent group” atomic substitution engineering is constructed to investigate the role of foreign atoms in sulfur redox reaction, and reveal the origin of catalytic activity. Theoretical calculations reveal that the real active sites are the S atoms adjacent to the doped atoms. It has been demonstrated that Nb atomic substitution acts as an initiator to trigger a “Domino Effect” of activating the S sites, enhancing the adsorption ability, facilitating the conversion reaction of sulfur species, and accelerating the Li+ diffusion. Enlightened by the theoretical guidance, Nb-doped MoS2 ultrathin nanosheets assembled hollow nanotubes (Mo1-xNbxS2 HNTs) are fabricated as efficient “adsorption-conversion” sulfur hosts, which exhibit high initial discharge capacities (1163 mAh g−1 at 0.2 C, 971 mAh g−1 at 0.5 C). An initial capacity of 613 mAh g−1 could be achieved under high sulfur loading (3.13 mg cm−2) and lean electrolyte (5.6 μL mg−1). This work provides pivotal guidance to design highly efficient catalytic cathodes for advanced Li-S batteries.

Composite Lithium and Thick Cathode for High-Energy Long-Cycling Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are recognized as a promising candidate for next-generation energy storage systems due to their high theoretical energy density and the abundance of sulfur. However, achieving a long-cycling Li-S battery with a specific energy capacity more than 300 Wh kg−1 presents several challenges, notably lithium metal pulverization induced by non-uniform stripping leading to pit formation and subsequent dendritic deposition. This detrimental cycle exacerbates cell shorting and capacity degradation, particularly under conditions of high electrode loading and low electrolyte condition. To address this problem, we developed a composite lithium metal anode that incorporates nanometer-sized carbon particles uniformly dispersed throughout. This design promotes more uniform lithium stripping by intercepting the uneven growth of pits with the carbon particles. The following deposition of lithium on these carbon particles demonstrates improved uniformity compared to surfaces with irregular pits. As a result, the composite lithium demonstrated a pulverization rate significantly slower than that of commercial lithium, extending Li-S battery cycle life threefold when integrated into batteries with sulfurized polyacrylonitrile (SPAN) cathodes operating at an areal capacity of 8 mAh cm−2. Additionally, we present a strategy to further enhance Li-S battery energy density by increasing the active mass of the cathode, exemplified by a SPAN cathode with an areal capacity of 8 mAh cm−2 and an active-material-ratio of 96wt%, showcasing superior cycling stability.

Long Chain Polysulfides Control via Ferroelectric (Ba0.9Sr0.1TiO3) Nanoparticles Doped Sulfur Cathode for High-Capacity Li-S Batteries

Lithium-sulfur (Li-S) batteries show promise in energy storage technology due to their high energy density and cost-effectiveness. However, practical application faces challenges, including low electrical conductivity of sulfur and discharge products, and the generation of insoluble compounds like Li2S during cycling. Soluble polysulfides can migrate, perpetuating a shuttle effect that leads to deposition of solid Li2S2 and Li2S on the anode, reducing efficiency and cycle life. Efforts to enhance cathode conductivity and suppress polysulfide loss during cycling are ongoing to overcome these challenges. In this study we are reporting electrochemical performance of Ba0.9Sr0.1TiO3 (BST) having polarization of 14.58 μC/cm2 doped sulfur/carbon black/polyvinylidene fluoride (S/BST/CB/PVDF) composite as cathode materials for Li-S batteries. The performance of S50BST30CB10PVDF10, and S40BST40CB10PVDF10 fabricated cathodes in terms of structural, electronic, morphological, and electrochemical response have been tested. X-ray diffraction spectra confirm tetragonal symmetry (c/a=1.0073), Raman spectroscopic study confirms Raman modes (A1(TO1), A1(TO2), A1(TO3) and A1(LO3)) of the tetragonal orientation for BST modified composites. All the compositional cations are observed from SEM images confirm homogeneous distribution of BST in the sulfur cathode system having grain sizes (1-1.5 μm) which is based on microscopic analysis. BST coupled C-S composite cathodes showing improved electrochemical performance in comparison to C-S composites. The high-capacity composites cathode in 1st cycle is S50BST30CB10PVDF10, tested @100 mA/g & 200 mA/g with polypropylene (PP) separator showing specific capacities ~820 mAh/g & ~540 mAh/g respectively, with improved capacity retention up to 60%. We observed that the hybrid composite cathode S40BST40CB10PVDF10 which was tested @100 mA/g showing specific capacity ~1080 mAh/g and remained up to 395 mAh/g after 100th cycle with capacity retention of 36%, very stable response till 100th cycles attributes polysulfide migration is effectively reducing due to ferroelectric particles doping in the composite cathode. Two plateaus were observed in between 2.3V to 2.0 V and 2.0 V to 1.5 V in the charge/discharge characteristics and high cyclic stability substantiate the superior performance of the designed ferroelectric nanoparticles doped S/CB composite cathode materials due to the efficient reduction in the polysulfide shuttle effect in these composite cathodes. Oxidation peaks for S50BST30CB10PVDF10 composite are at 2.6 V & 2.7 V and reduction peaks are at 2.0 V & 2.2V suggests an enhanced kinetics of the reduction reaction with the BST doped cathode as expected due to the alteration in the kinetics might be due to ferroelectric nanoparticles coupling & reversible transformation of Li2S to short/long chain LiPSs and finally to S8. In the case of symmetric cells with the positive and blocking electrodes. We have confirmed that the active material, sulfur, does not contribute to the resistance of the positive electrode, however due to inclusion of BST up to 20 & 30 wt% and applying RC(R)W circuit model for interfacial parameters. The observed values for S50BST30CB10PVDF10 are as Rs (2.688) C= 9.1 µF Rct (145 Ώ) and W (0.02312) showing the improved diffusion pathways for Lithium ions. Considering that polar substances have good affinity towards polysulfide and can provide more stable reacting environment in the cathodic site, to trap polysulfide intermediates via induced permanent dielectric polarizability. It is expected that spontaneous polarization induced by asymmetric crystal structure of ferroelectrics provide internal electric fields and increase chemisorption with heteropolar reactive.

Evaluation and Regulation of Interfacial Reaction of Cathode for Lithium-Sulfur Batteries to Improve Electrochemical Performance

In the pursuit of high-energy-density batteries, sulfur (S)-based materials have emerged as promising cathode materials due to high-capacity (1,672 mAh g-1 for lithium-sulfur) [1]. However, their degradation caused by the dissolution of reaction intermediates during electrochemical cycling, has led to diminished electrochemical performance. To address this issue, various surface treatments, including the formation of chemical/physical protective layers and doping with heteroatoms, have been explored [1-2]. Despite these efforts, real-time evaluation of the degradation and the effectiveness of such surface modifications on electrochemical performance remains challenging due to the difficulty in distinguishing between degradation and electrochemical reactions.In this context, our aim is to evaluate the degradation of high-capacity S-based cathodes using electrochemical techniques in real-time. Specifically, we distinguish the chemical reactions from the electrochemical reactions based on the numerical analysis and further quantify the degradation. Furthermore, we apply our evaluation method to assess the effectiveness of surface treatments on electrode materials.

Ab Initio Simulation of Raman Fingerprints of Sulfur/Carbon Copolymer Cathodes During Discharge of Li-S Batteries.

Sulfur/carbon copolymers have emerged as promising alternatives for conventional crystalline sulfur cathodes for lithium-sulfur batteries. Among these, sulfur-n-1,3-diisopropenylbenzene (S/DIB) copolymers, which present a 3D network of DIB molecules interconnected via sulfur chains, have particularly shown a good performance and, therefore, have been under intensive experimental and theoretical investigations. However, their structural complexity and flexibility have hindered a clear understanding of their structural evolution during redox reactions at an atomistic level. Here, by performing state-of-the-art ab initio molecular dynamics-based Raman spectroscopy simulations, we investigate the spectral fingerprints of S/DIB copolymers arising from local structures during consecutive reactions with lithium. We discuss in detail Raman spectral changes in particular frequency ranges which are common in S/DIB copolymers having short sulfur chains and those consisting of longer ones. We also highlight those distinctive spectroscopic fingerprints specific to local S/DIB structures containing only short or long sulfur chains. This distinction could serve to help distinguish between them experimentally during discharge. Our theoretically predicted results are in a good agreement with experimental Raman measurements on coin cells at different discharge stages. This work represents, for the first time, an attempt to compute Raman fingerprints of sulfur/carbon copolymer cathodes during battery operation including quantum-chemical and finite-temperature effects, and provides a guideline for Raman spectral changes of arbitrary electrodes during discharge.

Accelerated Ion-Electron Transport in Bi-Heterostructures Constructed Based on Ohmic Contacts for Efficient Bi-Directional Catalysis of Lithium-Sulfur Batteries.

Although lithium-sulfur batteries have satisfactory theoretical specific capacity and energy density, they are difficult to further commercialize due to the shuttle effect of soluble polysulfides and slow sulfur oxidation kinetics. Based on this, in this work, the catalyst MXene-VS4-SnS2 (MVS), a dual heterostructured catalyst with ohmic contacts, is prepared by a one-step hydrothermal method and electrostatic self-adsorption for lithium-sulfur battery cathode materials. Experimental and theoretical results show that the ohmic contact induces spontaneous charge rearrangement, resulting in the formation of a fast charge transfer pathway at the MVS heterojunction interface, which helps to reduce the energy barrier for polysulfide reduction and Li2S oxidation during the discharge/charge process. In addition, the inherent sulfophilicity of VS4 and SnS2 promotes the conversion of S species, while the pleated MXene nanosheets not only provide a highly conductive network for the active sulfur but also retain a rich internal space to maintain the integrity of the cathode structure during the continuous cycling process. As a result, the MVS cathode exhibits excellent electrochemical performance even under high sulfur loading. The integration of excellent performance with a facile synthesis process provides a promising approach for designing highly efficient electrocatalysts suitable for the energy field.

Nanotechnology in Lithium-Sulfur Batteries: Addressing the Challenges in Battery Cycle Life and Safety

Lithium-sulfur (Li-S) batteries, with their high energy density and affordable material prices, are a viable alternative to ordinary lithium-ion batteries, especially for electric cars. Their actual application is limited by challenges such as substantial volume expansion, low electrical conductivity, and the polysulfide shuttle effect, despite their advantages. This research investigates how incorporating nanomaterials into Li-S battery cathodes, anodes, and electrolytes might improve battery performance and analyzes the potential of nanotechnology to address these problems. The application of metal oxides, graphene oxide, and carbon nanofibers to improve the stability and conductivity of sulfur cathodes is covered. Additionally, it examines anode protection strategies using nanocoating and protective layers to inhibit dendrite growth and improve safety. The incorporation of nanoparticles in electrolytes to improve ionic conductivity and reduce side reactions is also analyzed. Despite the progress, challenges such as the polysulfide shuttle effect and volume changes remain. The paper concludes with recommendations for future research to develop commercially viable Li-S batteries with higher capacity, longer lifespan, and improved safety.

Novel Resveratrol-Derived Sulfur-Rich Polymers: Advanced Materials for Silver Capture and High-Performance Lithium–Sulfur Battery Cathodes

Novel Resveratrol-Derived Sulfur-Rich Polymers: Advanced Materials for Silver Capture and High-Performance Lithium–Sulfur Battery Cathodes

Xanthate-Mediated Oxidation of Li2S as the Lithium-Containing Cathode in Lithium-Sulfur Batteries with Extremely Low Overpotential.

Lithium-sulfide (Li2S) has long been pursued as a lithium-containing cathode material for high-energy-density lithium-sulfur (Li-S) batteries. Unfortunately, its direct oxidation generally has a large overpotential, giving rise to low energy efficiency. The use of redox mediators to accelerate the conversion of solid Li2S to polysulfides represents a possible solution to lower the initial oxidation overpotential. However, most reported redox mediators exhibit significantly higher redox potentials than the desirable value. Herein, it is serendipitously found that lithium ethyl xanthate (LiEX) formed from the reaction among Li2S, ethanol, and CS2 at room temperature is an efficient redox mediator. It has a redox potential (≈2.3V vs Li+/Li) close to the electrochemical oxidation potential of Li2S (2.25V vs Li+/Li), which enables fast Li2S oxidation reaction kinetics, and more importantly, lowers the Li2S oxidation potential from ≈3.6 to ≈2.3V. When further integrated with an Ni-NC catalyst in a tandem catalysis scheme, a remarkable specific capacity of ≈1100 mAh g-1 at 0.2mA cm-2 and long cycle life of 1400 cycles with ∼73% capacity retention is achieved, outperforming those of other Li2S-based cathode materials from recent literature.

Study of the Activator Effects on the Specific Surface Area of Porous Carbon and its Performance as Lithium-Sulfur Battery Cathode

A study was conducted to investigate the effect of activator types KOH, ZnCl2, and H3PO4 on the specific surface area of porous carbon and its performance as a Li-S battery. Porous carbon was synthesized from candlenut shells through a carbonization process at 700 °C using three types of activator solutions with a concentration of 0.36 M. The porous carbon activated with KOH achieved the best results, with a specific surface area of 681 m²g-1. The porous carbon candlenut shell-sulfur (PCCS-S) composite was obtained by the solid-state reaction method in a ratio of 1:2.5 w% and heat-treated at 155 °C to form the PCCS-S composite. The PCCS-S composite was then made into a slurry and coated onto Al-foil to obtain a layer of electrodes with a thickness of 200 µm. The PCCS-S cathode was then assembled into a coin battery with lithium metal as the anode and an electrolyte of 1.0 M LiTFSi solution dissolved in 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) (v/v, 1:1). Charge-discharge characterization was carried out at a charge rate of 1 C for 50 cycles. Characterization shows that the performance of the PCCS-S KOH composite cathode Li-S battery is stable at a specific capacity of 324 mAhg-1 after the first 10 cycles, with an average Coulombic efficiency of around 86.8 %.

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

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

Waste to Wealth: One-Step Exfoliating of Spent Graphite to Build a Low-Cost Cathode for Lithium-Sulfur Batteries.

With the booming development of Li-ion batteries (LIBs), the recycling and reusing of spent graphite (SG) from LIBs is becoming increasingly crucial. Meanwhile, developing low-cost and efficient carbon hosts for lithium-sulfur (Li-S) batteries has gained widespread attention in the past decade. Nevertheless, the processing of carbon materials as sulfur hosts is often energy-consuming and complex. Herein, a simple and environmental-friendly strategy is proposed to reuse the SG to prepare graphene/sulfur composite cathode for Li-S batteries. Due to expanded layer spacing and defects of SG, sulfur molecules can strip it into a graphene-type host via ball milling. By optimizing the S/SG ratio and ball milling time, the as-prepared graphene/sulfur composite cathode with 70 wt.% sulfur content exhibits a high capacity of 1000 mAh g-1. With a high sulfur loading of 4.68 mg cm-2, the graphene/sulfur cathode can maintain 526 mAh g-1 after 400 cycles. This work provides a novel waste-to-wealth perspective for recycling spent graphite from LIBs to reuse in Li-S batteries.

Gelation-pyrolysis strategy for fabrication of advanced carbon/sulfur cathodes for lithium-sulfur batteries

The development of high-performance carbon-based composite hosts play decisive roles in the electrochemistry of lithium sulfur batteries. Herein, a novel metal-ion induced gelation self-assembly technology is reported to construct sodium alginate carbon (SAC) based polar hierarchical carbon composites with cross-linked network architecture and in-situ co-grown cross-linked polar nanoparticles. Interestingly, it shows high versatility to an extensive array of materials including metals, alloys, and metallic oxides. As a representative, NiCo alloy nanoparticles are chosen to obtain the SAC/NiCo composite host for sulfur in LSBs, which possess superior physical/chemical adsorption capabilities and catalytic conversion kinetics to polysulfide in virtue of synergistic interaction between the hierarchical pore structures and NiCo catalyst. The designed SAC/NiCo-S cathode shows superior electrochemical performance with excellent rate capacity (2 C: 693.5 mAh/g) and enhanced cycling stability (764.3 mAh/g at 0.1 C after 240 cycles). This work provides a straightforward approach for fabricating multifunctional carbon composites with adjustable component for advanced energy storage system.

Synthesis and performance evaluation of bio-derived and synthetic carbon as lithium-sulfur battery cathode

The next-generation of batteries need be both energy dense and environment friendly. Lithium sulfur batteries (LSBs) satisfy both criteria but their practical implementation is marred by the highly resistive nature of sulfur. Carbon-based cathodes play a vital role in mitigating the issue because their high conductivity allows for effective electron transfer during electrochemical cycling. Synthesis and electrochemical evaluation of carbon-based cathodes from two different sources for LSBs was carried out. Herein, two kinds of carbon, namely bio-derived carbon from coconut shells (CC500) and N-doped carbon (NC) from polyacrylonitrile fibers were synthesized and sulfur was incorporated via the melt diffusion route. The composites are characterized by PXRD and TGA, which determined 80 wt% mass loading of sulfur. The higher intensity of G-band over D-band in Raman spectroscopy indicates greater graphitic character for CC500 compared to NC. SEM images show large macro-pore like tunnels in CC500 while NC appears are irregular chunks. EDAX spectra showed 20 wt% N content in NC while CC500 is largely carbon with some minor surface oxygen. In galvanostatic charge–discharge cycling of coin cells, bare CC500/S shows better specific capacity compared to NC/S samples but the trend flips once a separator modified with 4 mg of graphene oxide (GO) is introduced (indicated as NC/S/GO4 and CC500/S/GO4). This points towards synergy between N-doped carbon and GO layer in retaining the soluble polysulfides in the catholyte region. NC/S/GO4 exhibited better capacity i.e., 1453, 1024, 866, 787, 697 mAh/g versus 1016, 779, 672, 551, 441 mAh/g offered by CC500/S/GO4 when discharged at 50, 100, 200, 300 and 500 mA/g, respectively.

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.