Sulfur Utilization Research Articles

Dissociation-Precipitation Chemistry of Lithium Polysulfides and Its Correlation to Dynamic Evolution of Cathode-Electrolyte Interphase in Highly Solvating Electrolyte.

Lithium-sulfur (Li-S) batteries has been regarded as one of the most promising next-generation energy storage systems due to their high theoretical energy density. However, the practical application of Li-S batteries is still hindered by the unstable cathode-electrolyte interphase and the early passivation of charge product (Li2S), leading to poor cycling stability and low S utilization. Herein, we propose an electrolyte engineering strategy using highly solvating hexamethylphosphoramide (HMPA) as a co-solvent to elucidate the dissociation-precipitation chemistry of lithium polysulfides (LiPSs). The multimode optical spectroscopies confirm that this electrolyte engineering is able to effectively regulate the solvation of LiPSs to initiate a radical-assisted conversion pathway and control three-dimensional (3D) Li2S electrodeposition to boost sulfur utilization. More importantly, the dynamic evolution of cathode-electrolyte interphase, featuring with S-/P-containing species, is also assessed by both distribution of relaxation times technology and X-ray photoelectron spectroscopy, which can suppress the passivation of Li2S to enhance conversion reversibility. As a proof-of-concept, a Li-S cell with high S loading mass of 7.75 mg cm-2 demonstrates an extremely high area capacity of 7.86 mAh cm-2 at a current density of 1.30 mA cm-2 , representing a significant advancement in promoting the development of practical high-energy-density Li-S batteries.

Molecular Clip Strategy of Modified Sulfur Cathodes for High-Performance Potassium Sulfur Batteries.

Potassium-sulfur (K-S) batteries are severely limited by the sluggish reaction kinetics of the cyclooctasulfur (cyclo-S8) electrode with low conductivity, which urgently requires a novel cathode to facilitate activity to improve sulfur utilization. In this study, using the wet chemistry method, the molecular clip of Li+ is created to replace cyclo-S8 molecular with the highly active chain-like S6 2- molecular. The molecular clip strategy effectively lowers the reaction barrier in potassium-sulfur systems, and the stretching of S─S bonds weakens the binding between sulfur atoms, facilitating the transformation of potassium polysulfides (KPSs). The as-prepared cathode exhibits a reversible capacity of 894.8mAhg-1 at a current rate of 0.5C. It maintains a long cycle life of 1000 cycles with a stable coulombic efficiency in the potassium-sulfur cells without cathode catalysts. Operando XRD and Raman spectra combined with density functional theory (DFT) calculations, revealing the high efficiency of enhanced conversion of potassium polysulfide for high-performance K-S batteries.

Overcoming the conversion reaction limitation at three-phase interfaces using mixed conductors towards energy-dense solid-state Li-S batteries.

Lithium-sulfur (Li-S) all-solid-state batteries (ASSBs) hold great promise for next-generation safe, durable and energy-dense battery technology. However, solid-state sulfur conversion reactions are kinetically sluggish and primarily constrained to the restricted three-phase boundary area of sulfur, carbon and solid electrolytes, making it challenging to achieve high sulfur utilization. Here we develop and implement mixed ionic-electronic conductors (MIECs) in sulfur cathodes to replace conventional solid electrolytes and invoke conversion reactions at sulfur-MIEC interfaces in addition to traditional three-phase boundaries. Microscopic and tomographic analyses reveal the emergence of mixed-conducting domains embedded in sulfur at sulfur-MIEC boundaries, helping promote the thorough conversion of active sulfur into Li2S. Consequently, substantially improved active sulfur ratios (up to 87.3%) and conversion degrees (>94%) are achieved in Li-S ASSBs with high discharge capacity (>1,450 mAh g-1) and long cycle life (>1,000 cycles). The strategy is also applied to enhance the active material utilization of other conversion cathodes.

Dual-Functional SnO2-CNT-PANI||PP||SnO2 Separator for Enhanced Lithium-Sulfur Battery Stability and Capacity

Lithium-sulfur batteries (LSBs) provide high capacity and energy density for advanced energy storage but encounter performance and safety issues due to lithium polysulfides (LiPSs) dissolution and dendrite formation. This study introduces a dual-functional SnO2-CNT-PANI||PP||SnO2 separator (DF-SNCPS) aimed at improving the stability and safety of LSBs. The separator includes a SnO2-CNT-PANI layer on the sulfur cathode side for enhanced electrical conductivity and polysulfide adsorption and a SnO2 nanoparticle (nano-SnO2) layer on the lithium anode side to regulate lithium-ion concentration and inhibit dendrite growth. Density functional theory (DFT) and the phase field method have verified the relevant material's catalytic performance and dendrite suppression ability. These methods have provided a comprehensive understanding of the underlying mechanisms, providing auxiliary explanations for their role in catalyzing polysulfide conversion and suppressing lithium dendrite growth. This innovative design mitigates the shuttle effect and enhances cyclic stability and sulfur utilization, achieving a notable cyclic performance with a capacity retention of 0.05% per cycle over 800 cycles at 1C. The synergistic effects of the modified separator present a viable pathway for LSB commercialization.

Rationally Designed Binder with Polysulfide-Affinitive Moieties and Robust Network Structures for Improved Polysulfide Trapping and Structural Stability of Sulfur Cathode.

Lithium-sulfur batteries (LSBs) have emerged as a promising next-generation energy storage application owing to their high specific capacity and energy density. However, inherent insulating property of sulfur, along with its significant volume expansion during cycling, and shuttling behavior of lithium-polysulfides (LiPSs), hinder their practical application. To overcome these issues, a crosslinked cationic waterborne polyurethane (CCWPU) is rationally designed as a binder for LSBs. The mechanical robustness of CCWPU enables it to withstand the high stress derived from volume expansion of sulfur, facilitating charge-transferring through conserved charge-transfer pathway and promoting interconversion of LiPSs. Additionally, polar urethane groups offer favorable interaction sites with LiPSs, mitigating shuttling behavior of LiPSs via polar-polar interaction. Density functional theory investigations further elucidate that the incorporation of cationic moieties enhances LiPSs immobilization by confining Sn x- (x = 1 or 2) in LiPSs, thereby improving sulfur utilization. Benefiting from these, the cell with CCWPU demonstrates reduced polarization, superior LiPSs conversion rates, and stable cycling performance. Moreover, water-processable nature of CCWPU aligns with environmental consciousness. These diverse functionalities of CCWPU provide valuable insights for the development of advanced binder for LSBs, ultimately improving the electrochemical performances of LSBs.

MOF-Derived MoC/WC Heterostructure as Bidirectional Catalyst for Lithium Polysulfide Enables High-Performance Lithium-Sulfur Batteries.

Since lithium-sulfur (Li-S) batteries have high energy density and environmental friendliness, they have garnered a lot of attention as a new type of energy storage technology. However, the shuttle effect of lithium polysulfides (LiPSs) and low utilization of sulfur (S) in Li-S batteries reduce the cycle stability and energy efficiency and limit their practical application. Therefore, it is urgent to achieve simultaneous immobilization and conversion of LiPSs utilizing catalysts. Herein, a metal-organic framework (MOF)-derived MoC/WC@NC heterojunction is synthesized as a bidirectional catalyst for LiPSs in high-performance Li-S batteries. Experimental and theoretical calculations indicate that the catalyst is expected to improve the catalytic activity for reduction and oxidation reactions of LiPSs, thereby accelerating the kinetics of Li-S batteries. In conclusion, with the incorporation of the novel catalyst between the cathodes and separators in Li-S batteries, the assembled batteries demonstrate excellent rate performance, with an initial discharge capacity of 1752.1 mAh g-1 at 0.1 C, and a discharge-specific capacity of 783.2 mAh g-1 even at 2 C. More significantly, the coulombic efficiency stayed above 99% and the capacity of 589.1 mAh g-1 after 1000 cycles at 1 C with a decay rate of only 0.062% each cycle.

A conjugated porous triazine-linked polyimide host with dual confinement of polysulfides for high-performance lithium-sulfur batteries

In the quest for next-generation energy storage solutions, lithium-sulfur (Li-S) batteries present exceptional potential due to their high energy density and cost-effectiveness. Nevertheless, significant challenges, such as the shuttle effect of lithium polysulfides (LiPSs) and inadequate sulfur utilization, have impeded their practical application. In this study, we report the design and synthesis of a novel covalent organic polymer that integrates a triazine-linked framework with carbonyl-enriched polyimide moieties, serving as a highly effective sulfur host for Li-S batteries. This engineered polymer not only provides abundant micropores for the physical confinement of LiPSs, but also facilitates robust chemical interaction through synergistic N-Li and O-Li bonding. The hierarchical porous architecture enhances sulfur loading, while the extended π-conjugation promotes rapid electron transport during LiPSs conversion. Consequently, the composite cathode achieves an impressive specific capacity of 1352 mAh g-1 at 0.1C, along with sustained cyclic stability (453 mAh g-1 after 400 cycles at 4C). These findings highlight the potential of multifunctional polymeric hosts in addressing critical limitations of Li-S batteries, offering a new blueprint for further developments in the field of high-performance energy storage systems.

Construction of spontaneous built‐in electric field on heterointerface furnishing continuous efficient adsorption-directional migration-conversion of polysulfides

Integrating sulfur with efficient electrocatalysts remains a pressing need in lithium-sulfur (Li-S) batteries for modulating the sluggish conversion kinetics and restricting the shuttle behavior of lithium polysulfides (LiPSs). Herein, a compact p-type Fe3O4 and n-type MoS2 heterostructure embedded on nitrogen-doped porous carbon (Fe3O4-MoS2-NPC-0.5) is meticulously constructed as dual-functional hosts that can facilitate continuous catalytic conversion of LiPSs. The p-type Fe3O4 exhibits a high affinity for polysulfides, while n-type MoS2 enables effective catalysis of LiPSs. The successful migration of LiPSs from Fe3O4 to MoS2 is bridged due to a spontaneous built-in electric field (BIEF) at the p-n heterojunction interface. The synergistic effect prevents the passivation of adsorption sites on Fe3O4 and enhances the efficient catalytic conversion capabilities of MoS2. Consequently, the battery with Fe3O4-MoS2-NPC-0.5/S exhibits a prominent initial capacity of 1120.6 mAh g−1 at 2 C, maintains outstanding cyclability with a capacity attenuation rate of 0.045 % per cycle at 0.5 C, and high sulfur utilization at large sulfur loadings. This work offers insights into optimizing the performance-enhanced Li-S battery electrodes by the formation of a dynamic “trapping-directional migration-conversion” reaction.

In Situ Welding Ionic Conductive Breakpoints for Highly Reversible All-Solid-State Lithium-Sulfur Batteries.

Poly(ethylene oxide) (PEO)-based solid-state lithium-sulfur batteries (SSLSBs) have garnered considerable interest owing to their impressive energy density and high safety. However, the dissolved lithium polysulfide (LiPS) together with sluggish reaction kinetics disrupts the electrolyte network, bringing about ionic conductive breakpoints and severely limiting battery performance. To cure this, we propose an in situ welding strategy by introducing phosphorus pentasulfide (P2S5) as the welding filler into PEO-based solid cathodes. P2S5 can react with LiPS to form ion-conducting lithium polysulfidophosphate (LSPS), which suppresses the interaction with PEO and in situ weld breakpoints within the ionic conductive network. Of interest, LSPS also shows another function, that is, to catalyze sulfur redox reactions by decreasing the activation energy of sulfur reduction reaction from 0.87 to 0.75 eV, mitigating the shuttle effect. The in situ welding strategy helps the assembled SSLSB to feature exceptional cycling stability and a high energy density of up to 358 Wh·kg-1 due to the high sulfur utilization. Our findings pave an avenue for practical high-performance SSLSBs with a novel welding filler for in situ welding of ionic conductive network.

Quantitative Trait Loci Mappings for the Sulfur Utilization Efficiency-Related Traits at the Seedling Stage of Wheat.

Sulfur (S) is a vital element for the normal growth and development of plants, performing crucial biological functions in various life processes. This study investigated thirteen S utilization efficiency (SUE)-related traits at the seedling stage of wheat using a recombinant inbred line (RIL) population. The quantitative trait loci (QTLs) were mapped by genetic mapping. Thirteen S utilization efficiency-related traits were investigated under two hydroponic culture trials with low S (0.1S, T1), moderate S (0.5S, T2), and high S (1.5S, T3) levels, using the wheat RILs. A total of 170 QTLs for the thirteen traits in different treatment environments were identified. Among them, 89, 103, and 101 QTLs were found in T1, T2, and T3, respectively. A total of 63 QTLs were found in the multiple treatment environments, the other 107 QTLs only being detected in a single treatment environment. Among them, thirteen relatively high-frequency QTLs (RHF-QTLs) and eleven QTL clusters were found. Five (QSh-1D, QRn-1D, QSdw-1D, QTdw-1D, and QTsc-1D) and six (QRdw-6A, QSdw-6A, QTdw-6A, QRsc-6A, QSsc-6A, and QTsc-6A) RHF-QTLs were identified in QTL clusters C3 and C10, respectively. These thirteen RHF-QTLs and eleven QTL clusters are expected to apply to the molecular marker-assisted selection (MAS) of wheat.

Decelerating and Accelerating Sulfur Reduction Reaction via P-OV-In2O3 Enables High-Performance Li-S Batteries.

The sluggish sulfur reduction reaction (SRR) kinetics of lithium-sulfur (Li-S) batteries seriously limits the development of Li-S batteries. The initial reduction of solid (S8) to liquid (soluble Li2Sn (4≤n≤8)) is relatively easy due to the low activation energy, whereas the subsequent conversion of liquid (soluble Li2Sn) to solid (insoluble Li2S2/Li2S) has much higher activation energy, which leads to the accumulation of Li2Sn and exacerbates the shuttle effect of Li2Sn. Therefore, establishing one selective catalyst that decelerates the previous solid-liquid reaction and accelerates the subsequent liquid-solid reaction is essential for rational tailoring of the SRR for improved performance of Li-S batteries, but it represents a daunting challenge. Here, considering that the indium oxide catalyst possesses selective catalytic properties and drawing inspiration from the theoretical calculations, In2O3 nanospheres containing phosphorus doping and oxygen vacancies (P-OV-In2O3 NSs) are designed and synthesized as a selective catalyst for Li-S batteries. Contributed by the unique selective catalytic capability, the batteries using P-OV-In2O3 NSs modified separators exhibit excellent sulfur utilization, superb rate performance (656mAhg-1 at 5.0C), and low-capacity decay rate of about 0.069% per cycle over 500 cycles at 1.0C.

Entropy Engineering-Modulated D-Band Center of Transition Metal Nitrides for Catalyzing Polysulfide Conversion in Lithium-Sulfur Batteries.

The sluggish sulfur redox kinetics and severe polysulfide shuttle effect seriously restrict the cycling stability and lower the sulfur utilization of lithium-sulfur (Li-S) batteries. Efficient catalytic conversion of polysulfides is deemed a crucial strategy to address these issues, but still suffers from an unclear electronic structure-activity relationship and a limited catalysis performance. Herein, entropy engineering-induced electronic state modulation of metal nitride nanoparticles embedded within hollow N-doped carbon (HNC) polyhedra are theoretically and experimentally constructed as a catalyst to accelerate the redox process of sulfur and suppress polysulfide migration in Li-S batteries. By introducing V, Cr, and Nb elements to engineer the entropy of TiN, the metal d-band center is optimized to approach the Fermi level, significantly facilitating the conversion of sulfur species. Accordingly, the TiVCrNbN@HNC catalyst enables Li-S batteries to achieve a high initial capacity (1299 mAh g-1 at 0.1C) and excellent cycling stability with a low capacity decay rate of 0.086% per cycle after 500 cycles. This work may provide a new insight into entropy engineering in catalyst design for high-performance Li-S 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 mAh 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.

Tethering and Catalyzing Lithium Polysulfides in the Cathode to Improve Lithium-Sulfur Battery Lifetime, Energy, & Power

Lithium-sulfur has been identified as one of the most promising lithium battery chemistries to achieve performance requirements that enable next-generation electrified applications, such as satellite miniaturization and long duration electrified aviation, with a completely U.S.-centric supply-chain [1] . In general, the dissolution and shuttling of intermediate lithium polysulfide (Li2Sx, 4 < x < 8) phases in current- and prior-generation Li-S batteries have limited sulfur utilization (<60%) and led to rapid lifetime degradation [2] . Substantial progress has occurred in C/S composites with sulfur utilization exceeding 60% using various sulfur dispersion and carbon support selection [3] [4] , though commercialization has been fraught with difficulties. NantG Power is pursuing novel routes to overcome many of the cell-scaling issues with the use of carbon substrate materials modified with sub-nanometer thick catalyst coatings to both accelerate the Solid -> Liquid and Liquid -> Solid phase transformations, as well as act as polar tethering sites for polysulfides. ALD has been shown to improve cathode stability in traditional Li-ion [5] and has been used to cap traditional C/S composite particles and electrodes [6] .These coatings, prepared with powder atomic-layer deposition (ALD), immobilize the intermediate polysulfides while simultaneously catalyzing their otherwise sluggish reaction kinetics of the multi-phase reactions. With this method, long-term sulfur utilization above 60% can be demonstrated in multi-Ah cells with >5mg/cm2/>60% sulfur loading and E:S < 5, exceeding 400 Wh/kg. This talk will outline a combination of computational modeling approaches (MD, AIMD, DFT, etc.) that predicts the energetic and lattice matching of highly disordered, sub nanometer ALD coatings coupled with electrochemical/chemical/physical interrogation and 1Ah test cell builds to highlight the promise of this reasonably novel direction.

Promoting the Radical-Mediated Pathway and Li₂S Conversion By N-Doped Carbon-Embedded Cobalt-Doped Titanium Nitride Electrocatalyst with High Donor-Number Solvent for Lean Electrolyte Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are recognized as some of the most promising candidates for next-generation batteries, owing to their high specific capacity, cost-effectiveness, and lightweight properties. Despite these advantages, the dissolution of the sulfur leads to the shuttling effect of long-chain lithium polysulfides (Li2Sx, 4≤x≤8). Moreover, the lean electrolyte system experiences a reduction in ionic transport due to the formation of ion-pairing and clusters of polysulfides. Therefore, the development of electrolytes that can stabilize the solvation structure of lithium-polysulfide and the introduction of electrocatalysts to suppress the shuttling effect are required for lean electrolyte lithium-sulfur batteries.High donor-number solvents can stabilize the Li+-solvated structure by effectively shielding the Li+ ion’s effective nuclear charge. This Li+-solvated structure, in coordination with high donor-number solvents, can effectively interact with tri-sulfur radicals and long-chain polysulfides, which possess relatively delocalized negative charges. As a result, a high donicity electrolyte can enhance sulfur utilization by increasing the solubility of polysulfides. However, the poor compatibility of high donor-number solvents with Li metal presents a challenge, making their excessive use impractical. Therefore, optimizing the amount of high donor-number solvent is essential. Through careful optimization, it is possible to achieve high donicity electrolyte conditions that are compatible with Li metal. The 1 vol% N,N-Dimethylacetamide (DMA) in 1,2-dimethoxyethane (DME)/1,3-dioxolane (DOL) co-solvent (DMA:DME:DOL=1:49.5:49.5 vol%) electrolyte achieved a higher discharge capacity after 20 cycles compared to both a low donicity (DME/DOL, 1:1 vol%) and a high donicity (DMA/DOL, 1:1 vol%) electrolyte. Electrolyte modification alone cannot completely suppress the shuttling effect, as the radical-mediated pathway activated by high donor-number solvent leads to the presence of tri-sulfur radicals. Recent research has investigated the ferromagnetic catalysts to enhance the adsorption of polysulfides through the Lorentz force and facilitate the conversion of Li2S with spin polarization in lithium-sulfur batteries. Introducing ferromagnetism through cobalt-doping into N-doped carbon embedded titanium nitride nanowires electrocatalysts could improve the adsorption of polysulfides and tri-sulfur radicals, as well as their conversion to Li2S and promote radical-mediated pathways with high donor-number solvents in lean electrolyte lithium-sulfur batteries. Consequently, N-doped carbon-embedded cobalt-doped titanium nitride nanowires on separator within the 1 vol% DMA electrolyte achieves a high discharge capacity of 454.8 mA h g−1 after 120 cycles with sulfur loading of 3.6 mg cm−2 and E/S ratio of 10 μL mg−1.

Electrochemical Responses of Solution-Impregnated Sulfur/Mesoporous Carbon Composites in Liquid Li-S and Solid-State Li-S Batteries

Lithium sulfur solid-state batteries (Li-S SSBs) have received great attention as next-generation sustainable energy storage devices due to their high energy density, low cost and potential safety. However, start-of-the-art Li SSBs have still faced a few serious of hinders such as distinct high interfacial impedance, insufficient sulfur utilization, lower sulfur mass loading, mismatch triple phase interfaces and also uncertain electrochemical mechanism between liquid and solid-state lithium sulfur batteries. Here, to address these concerns, we employed the encapsulation of sulfur into high conductivemesoporous carbon (MC) by combined solution impregnation and melt-diffusion techniques (IM) to prepare S@MC, and looked into their electrochemical responses in liquid (LiTFSI+LiNO3) and sulfide solid-state (LI6PS5Cl, LPSCl) electrolyte systems. The separately assembled liquid and solid-state Li-S cells exhibited initial discharge capacities of 1438 mAh g-1 and 1411 mAh g-1 at 0.1 C, and capacity retentions of 85.6% (at 0.5 C after 300 cycles) and 48.2% (at 0.5 C after 200 cycles), respectively. In order to enhance the long-term capacity retention of the Li-S SSB prepared by dry mixing of S and LPSCl, we tailored interfaces and introduced ploysulfido-intermediate compounds between S and LPSCl, and thus increasing intimate ionic contact through a weak polar solvent by wet mixing. The solid-state Li-S cells exhibited an initial discharge capacity of 1621 mAh g-1 at 0.1 C with capacity retention of 97.12% (0.1 C initial 5 cycles) and 58.53% (0.5 C after 200 cycles). This work evidently revealed that two step solid-liquid-solid and one step solid-solid charge transfer conversions followed for liquid and sulfide solid state electrolytes, respectively. The solution-impregnated S@MC-2-65%+LPSCl sulfur composite prepared by wet mixing could be potential candidate for high performance Li-S SSBs.

(Invited) Revealing the Reaction Mechanism and Chemo-Mechanics of Solid-State Na-S Batteries

Solid-state sodium-sulfur batteries show great promise for energy storage applications due to their high energy density, cost-effectiveness, and abundance of raw materials. Despite these promising characteristics, challenges such as the phase evolution of (poly)sulfides and how it is linked to the significant volume expansion occurring in the cathode during cycling are still poorly understood.1,2 In this talk, I will showcase our recent progress in developing solid-state sodium-sulfur batteries using different solid electrolyte systems, namely Na3PS4 and closo-borates. I will discuss how tortuosity impacts sulfur utilization in the composite cathode and provide new insights into sulfur redox chemistry and associated kinetic limitations. Furthermore, I will examine the correlation between phase, volume, and stress evolution.In summary, this study will offer unprecedented insights into the underlying mechanisms in solid-state sodium-sulfur batteries, which are of utmost importance for their further development towards commercialization. References Lei, Y. J., Liu, H. W., Yang, Z., Zhao, L. F., Lai, W. H., Chen, M., ... & Wang, Y. X. (2023). A Review on the Status and Challenges of Cathodes in Room‐Temperature Na‐S Batteries. Advanced Functional Materials, 33(11), 2212600.Ma, J., Wang, M., Zhang, H., Shang, Z., Fu, L., Zhang, W., ... & Lu, K. (2023). Toward the Advanced Next‐Generation Solid‐State Na‐S Batteries: Progress and Prospects. Advanced Functional Materials, 33(20), 2214430. Acknowledgment D.R. acknowledge financial support from the Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology, and Development, and the Christian Doppler Research Association (Christian Doppler Laboratory for Solid-State Batteries). J.T., J.K., D.R. acknowledge funding from the European Union's Horizon Europe research and innovation program under Grant Agreement No 101103834 (OPERA).

Nanocatalysts for High-Energy-Density Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries hold promise to be the next-generation Li energy-storage systems due to the high theoretical energy density (2600 W h ), and the abundance and environmental friendless of sulfur. Nevertheless, challenges arising from the fundamental Li-S chemistry hamper the practical viability of Li-S batteries. Specifically, the dissolution of Li polysulfides and their slow conversion kinetics collectively cause irreversible loss of the active material and short cycle life. Efforts have been intensively dedicated in physical confinement or chemical trapping of Li polysulfides, yet such passive blocking strategy is unable to fundamentally and sufficiently suppress the accumulation of sulfide products in the electrolyte, especially for high sulfur loading and long cycling. Here, we report a Li cation-doped tungsten oxide electrocatalyst that allows accelerated conversion kinetics to counteract the polysulfide dissolution and migration. In addition, the significant lithium sulfide (Li2S) oxidation barrier necessitates activation with a high overpotential, which results in low sulfur utilization and fast capacity decay. Accordingly, we also report a heterostructured WOx/W2C nanocatalyst synthesized via ultrafast Joule heating, and the resulting heterointerfaces contribute to enhance electrocatalytic activity for Li2S oxidation, as well as controlled Li2S deposition. We studied the fundamental relationships between the improved electrocatalytic activity and the optimized structures of the electrocatalysts, demonstrated the electrocatalytic effect on battery performance and highlighted the future design of catalytic materials for the advancement of practical Li-S batteries.

Enabling Separator Modification with Sulfiphilic CoTe2 Sites on Electrospun Carbon Nanofibers for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) have been recognized as a promising candidate for next generation electrochemical energy-storage technologies owing to their unparalleled theoretical capacity and energy density compared to conventional lithium-ion batteries. However, the sluggish redox kinetics of the electrochemistry and the formidable dissolution of polysulfides during cycling lead to poor sulfur utilization, serious polarization, cyclic instability, and hazardous Li corrosion/dendrites issues. Herein, cobalt tellurides and carbon nanofibers composites (CoTe2@CNFs) were designed, synthesized by facial electrospinning, and applied to modify the separator of Li–S batteries, providing a viable solution for these challenges. The composites feature polar CoTe2 nanoparticles embedded in each carbon nanofiber, and the carbon nanofibers intertwine with each other to form an interconnected 3D nanofiber network. The sulfiphilic CoTe2 nanoparticles exhibit dual functionality, as they both strongly interact with soluble polysulfides and dynamically facilitate polysulfide redox reactions. Moreover, the 3D nanofiber network not only provides an additional physical barrier to lithium polysulfides (LiPSs) but also enables uniform sulfur distribution, thereby significantly inhibiting LiPSs shuttling and accelerating sulfur conversion reactions. In summary, the functionally modified separator synergistically works as both redox mediators, catalyzing the sulfur conversion, and a buffer layer, regulating Li ions stripping/deposition behaviors. This work has provided a new avenue for designing nanomaterials with synergistic effect of catalytic conversion and chemisorption of polysulfides to promote high-performance Li-S batteries. Furthermore, it is expected to inspire the engineering of novel material architectures with enhanced properties for various energy-storage devices.

The Key Role of N/S Codoped Carbon Dots in Efficient Capture and Conversion of Lithium Polysulfides

AbstractThe dissolution and shuttle of lithium polysulfides (LiPSs) should be primarily responsible for rapid capacity decay in lithium‐sulfur batteries (LSBs), which severely limits sulfur utilization. Introduction of cathode additives that can immobilize and rapidly convert LiPSs has been identified as effective in alleviating the shuttle effect. In this study, N/S codoped carbon dots (NSCDs) have been synthesized via a typical hydrothermal method, whose surfaces are rich in polar functional groups (─COOH, ─OH, ─SO3, and ─NH2) to capture LiPSs and effectively modulate the deposition behavior of Li2S. NSCDs as an additive of cathode significantly improve the battery discharge capacity and cycle life that it could deliver a reversible specific capacity of 1207.2 mAh g−1 at a current density of 0.2 C and stably operate for over 400 cycles at 1 and 2 C current densities. This work provides valuable insights into the application of 0D carbon nanomaterials in the field of LSBs.