A Triple Crosslinked Binder with Hierarchical Stress Dissipation and High Ionic Conductivity for Advanced Silicon Anodes in Lithium-ion Batteries

Silicon (Si) is a promising anode material for high-energy-density lithium-ion batteries, but the significant volume change of Si particles during alloying/dealloying with lithium (Li) undermines the mechanical integrity of Si anode, causing electrode fracture, delamination and rapid capacity decay. Herein, a robust triple crosslinked network (TCN) binder with high ionic conductivity and hierarchical stress dissipation is reported for Si anodes, which is prepared by in situ chemical crosslinking polyacrylic acid (PAA) and melamine (MA). The triple interactions of hydrogen bonds, electrostatic interactions, and covalent amide bonds enhance the adhesion of binder to Si and synergistically promote stress dissipation within Si anodes, thus strengthening the dynamic structural stability of Si anodes during cycling. Moreover, the rapid coupling/decoupling of Li+ with the TCN binder enables an impressive Li+ transference number of 0.63 and high ionic conductivity of 1.2 × 10-4 S cm-1. Consequently, the Si-TCN anode delivers specific capacity of 2268 mAh g-1 with a high mass loading of 2 mg cm-2, high-rate performance of 1673 mAh g-1 at 5 A g-1, and stable cycling for 250 cycles at 1 A g-1, thus showing great prospects for high-energy-density Si-based batteries.

Heteroatom-engineered multicolor lignin carbon dots enabling bimodal fluorescent off-on detection of metal-ions and glutathione

Carbon dots (CDs) have emerged as a promising subclass of optical nanomaterials with versatile functions in multimodal biosensing. Howbeit the rapid, reliable and reproducible fabrication of multicolor CDs from renewable lignin with unique groups (e.g., -OCH3, -OH and -COOH) and alterable moieties (e.g., β-O-4, phenylpropanoid structure) remains challenging due to difficult-to-control molecular behavior. Herein we proposed a scalable acid-reagent strategy to engineer a family of heteroatom-doped multicolor lignin carbon dots (LCDs) that are functioned as the bimodal fluorescent off-on sensing of metal-ions and glutathione (GSH). Benefiting from the modifiable photophysical structure via heteroatom-doping (N, S, W, P and B), the multicolor LCDs (blue, green and yellow) with a controllable size distribution of 2.06-2.22 nm deliver the sensing competences to fluorometric probing the distinctive metal-ion systems (Fe3+, Al3+ and Cu2+) under a broad response interval (0-500 μM) with excellent sensitivity and limit of detection (LOD, 0.45-3.90 μM). Meanwhile, we found that the addition of GSH can efficiently restore the fluorescence of LCDs by forming a stable Fe3+-GSH complex with a LOD of 0.97 μM. This work not only sheds light on evolving lignin macromolecular interactions with tunable luminescent properties, but also provides a facile approach to synthesize multicolor CDs with advanced functionalities.

Bidirectional Interphase Modulation of Phosphate Electrolyte Enables Intrinsic Safety and Superior Stability for High-Voltage Lithium-Metal Batteries

Developing advanced high voltage lithium-metal batteries (LMBs) with superior stability and intrinsic safety is of great significance for practical applications. However, the easy flammability of conventional carbonate solvents and inferior compatibility of commercial electrolytes for both highly reactive Li anodes and high-voltage cathodes severely hinder the implementation process. Hence, we rationally designed an intrinsically nonflammable and low-cost phosphate electrolyte toward stable high-voltage LMBs by bidirectionally modulating the interphases. Benefiting from the synergistic regulation of LiNO3 and DME dual-additives in the 1.5 M LiTFSI/Triethyl phosphate electrolyte, thin, dense and robust electrodes/electrolyte interphases were well constructed simultaneously on the surfaces of Li anode and Ni-rich cathode, dramatically improving the stability and compatibility between electrodes and electrolyte. Consequently, boosted kinetic and high Coulombic efficiency of 98.6% for Li metal plating/stripping over 400 cycles and superior cycling stability of exceeding 4,000 h in Li symmetric cell is achieved. More importantly, the Li∥LiNi0.6Mn0.2Co0.2O2 cell assembled with a thin Li anode and high mass-loading cathode at a high cutoff voltage of 4.6 V retains a 98.4% capacity retention after 500 cycles at 1C. This work affords a promising strategy to develop nonflammable electrolytes enabling the high safety, good cyclability, and low cost of high-energy LMBs.

Structural and Interfacial Manipulation of Multifunctional Skeletons Enabled Shuttling-Free and Dendrite-Free Li-S Full Batteries

Li-S batteries are regarded as promising devices for energy storage systems owing to high energy density, low cost, and environmental friendliness. However, challenges of polysulfides shuttling in sulfur cathode and dendrite growth of lithium anode severely hinder the practical application. Developing advanced skeletons simultaneously regulating the cathode and anode is significant and challenging. Hence, a novel and scalable strategy combining spray drying and topological nitriding is proposed, and hierarchically assembled rGO hollow microspheres encapsulated highly porous nanospheres consisted of ultrafine Nb4 N5 -Nb2 O5 or Nb4 N5 nanoparticles as multifunctional skeletons for S and Li are designed. In such unique architecture, a 3D highly porous structure provides abundant void space for loading of S and Li, and accommodates volume change during cycling. Moreover, Nb4 N5 -Nb2 O5 heterostructured interface promotes adsorption-conversion process of polysulfides, while strong lithophilic Nb4 N5 induces the selective infiltration of Li into the void of the skeleton and regulates the uniform deposition and growth. More interestingly, in situ generated Li3 N@Nb ion/electron conducting interfaces induced by the reaction of Nb4 N5 and Li reduce the nucleation overpotential and induce selective deposition of Li into the cavity. Consequently, the Li-S full cell exhibits superior cycling stability and impressive rate performance with a low capacity ratio of negative/positive.

Mixed Ion/Electron Conductive Li3N-Mo Interphase Enabling Stable and Ultrahigh-Rate Lithium Metal Anodes

Lithium (Li) metal is a promising anode for high-energy-density batteries; however, its practical viability is hampered by the unstable metal Li-electrolyte interface and Li dendrite growth. Herein, a mixed ion/electron conductive Li₃N-Mo protective interphase with high mechanical stability is designed and demonstrated to stabilize the Li-electrolyte interface for a dendrite-free and ultrahigh-current-density metallic Li anode. The Li₃N-Mo interphase is simultaneously formed and homogeneously distributed on the Li metal surface by the surface reaction between molten Li and MoN nanosheets powder. The highly ion-conductive Li₃N and abundant Li₃N/Mo grain boundaries facilitate fast Li-ion diffusion, while the electrochemically inert metal Mo cluster in the mosaic structure of Li₃N-Mo inhibits the long-range crystallinity and regulates the Li-ion flux, further promoting the rate capability of the Li anode. The Li₃N-Mo/Li electrode has a stable Li-electrolyte interface as manifested by a low Li overpotential of 12 mV and outstanding plating/stripping cyclability for over 3200 h at 1 mA cm^-2. Moreover, the Li₃N-Mo/Li anode inhibits Li dendrite formation and exhibits a long cycling life of 840 h even at 30 mA cm^-2. The full cell assembled with LiFePO₄ cathode exhibits stable cycling performance with 87.9% capacity retention for 200 cycles at 1C (1C = 170 mA g^-1) as well as high rate capability of 83.7 mAh g^-1 at 3C. The concept of constructing a mixed ion/electron conductive interphase to stabilize the Li-electrolyte interface for high-rate and dendrite-free Li metal anodes offers a viable strategy to develop high-performance Li-metal batteries.

Highly efficient overall urea electrolysis via single-atomically active centers on layered double hydroxide

Anodic urea oxidation reaction (UOR) is an intriguing half reaction that can replace oxygen evolution reaction (OER) and work together with hydrogen evolution reaction (HER) toward simultaneous hydrogen fuel generation and urea-rich wastewater purification; however, it remains a challenge to achieve overall urea electrolysis with high efficiency. Herein, we report a multifunctional electrocatalyst termed as Rh/NiV-LDH, through integration of nickel-vanadium layered double hydroxide (LDH) with rhodium single-atom catalyst (SAC), to achieve this goal. The electrocatalyst delivers high HER mass activity of 0.262 A mg^-1 and exceptionally high turnover frequency (TOF) of 2.125 s^-1 at an overpotential of 100 mV. Moreover, exceptional activity toward urea oxidation is addressed, which requires a potential of 1.33 V to yield 10 mA cm^-2, endorsing the potential to surmount the sluggish OER. The splendid catalytic activity is enabled by the synergy of the NiV-LDH support and the atomically dispersed Rh sites (located on the Ni-V hollow sites) as evidenced both experimentally and theoretically. The self-supported Rh/NiV-LDH catalyst serving as the anode and cathode for overall urea electrolysis (1 mol L^-1 KOH with 0.33 mol L^-1 urea as electrolyte) only requires a small voltage of 1.47 V to deliver 100 mA cm^-2 with excellent stability. This work provides important insights into multifunctional SAC design from the perspective of support sites toward overall electrolysis applications.

Enhanced Activities in Alkaline Hydrogen and Oxygen Evolution Reactions on MoS2 Electrocatalysts by In-Plane Sulfur Defects Coupled with Transition Metal Doping

2D transition metal disulfides (TMDs) are promising and cost-effective alternatives to noble-metal-based catalysts for hydrogen production. Activation of the inert basal plane of TMDs is crucial to improving the catalytic efficiency. Herein, introduction of in-plane sulfur vacancies (S_v ) and 3d transition metal dopants in concert activates the basal planes of MoS₂ (M-S_v -MoS₂ ) to achieve high activities in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Acetate introducing mild wet chemical etching removes surface S atoms facilitating subsequent cation exchange between the exposed Mo atoms and targeted metal ions in solution. Density-functional theory calculation demonstrates that the exposed 3d transition metal dopants in MoS₂ basal planes serve as multifunctional active centers, which not only reduce ΔG_H* but also accelerate water oxidation. As a result, the optimal Ni-S_v -MoS₂ and Co-S_v -MoS₂ electrocatalysts show excellent stability and alkaline HER and OER characteristics such as low overpotentials of 101 and 190 mV at 10 mA cm^-2 , respectively. The results reveal a strategy to activate the inert MoS₂ basal planes by defect and doping co-engineering and the technique can be extended to other types of TMDs for high-efficiency electrocatalysis beyond water splitting.

Enabling dual valorization of lignocellulose by fluorescent lignin carbon dots and biochar-supported persulfate activation: Towards waste-treats-pollutant

The rationally-designed lignocellulose valorization that promotes a novel "waste-treats-pollutant" standpoint is highly desired yet still challenging for the spread of biomass industry. At this point, a cascade technique with the assistance of deep eutectic solvent (DES) fractionation is tailored to dually valorize wheat straw into fluorescent lignin carbon dots (LCDs) and bimetallic Mg-Fe oxide-decorated biochar (MBC) via solvothermal engineering and co-precipitation/pyrolysis respectively. Benefitting from the abundance of β-aryl ether and hydroxyl groups in DES-extracted lignin, the photoluminescence LCDs emit blue color in a wide excitation span, which can be adopted to selectively detect ferric ions (Fe³⁺) in a broad dosage scale with a highly linear correlation of 10-50 μM. Taking advantages of the MBC-aided persulfate activation, we propose the efficient arbidol removal system with a universal concentration of 20-200 ppm in the scalable pH ranging from 3 to 11. The dominate migration pathways involving with active oxygen species and surface electron transfer are comprehensively studied via electron paramagnetic resonance, radical-quenching experiments, and theoretical arithmetic. With the endeavor of biorefineries, this full-scale platform ignites the dazzling wildfire from dual lignocellulose valorization that will also seek its accurate position in the kingdoms of functional materials and wastewater restoration.

Unique CoWO4@WO3 heterostructured nanosheets with superior electrochemical performances for all-solid-state supercapacitors

Transition metal oxide-based battery-type electrode materials with well-defined nanostructure have shown great potential in supercapacitors, due to their high electrical conductivity and superior redox activity. Herein, promising CoWO₄@WO₃-1 heterostructured nanosheets with rich oxygen vacancies are designed via a two-step in situ construction process and following thermal treatment. The CoWO₄@WO₃-1 heterostructured nanosheet arrays grown on a flexible carbon cloth substrate can provide an effective nanoporous framework, facilitate electrons/ions transport, and generate effective synergistic effect of high conductivity from WO₃ and superior redox activity from CoWO₄. As a result, the as-prepared CoWO₄@WO₃-1 electrodes exhibit a high area specific capacity of 578.6 mF cm^-2 at a current density of 0.5 mA cm^-2 and keep 98.38% capacity retention at 20 mA cm^-2 over 30 000 cycles. Additionally, all-solid-state supercapacitors assembled with CoWO₄@WO₃-1 as cathodes and O_v-NiMoO₄ as anodes show a maximum area energy density of 13.93 mW h cm^-2 and power density of 6502.11 mW cm^-2, keeping outstanding cycling stability of 98.1% capacity retention over 20 000 cycles.

Metal-Organic Frameworks Offering Tunable Binary Active Sites toward Highly Efficient Urea Oxidation Electrolysis

Electrocatalytic urea oxidation reaction (UOR) is regarded as an effective yet challenging approach for the degradation of urea in wastewater into harmless N₂ and CO₂. To overcome the sluggish kinetics, catalytically active sites should be rationally designed to maneuver the multiple key steps of intermediate adsorption and desorption. Herein, we demonstrate that metal-organic frameworks (MOFs) can provide an ideal platform for tailoring binary active sites to facilitate the rate-determining steps, achieving remarkable electrocatalytic activity toward UOR. Specifically, the MOF (namely, NiMn_0.14-BDC) based on Ni/Mn sites and terephthalic acid (BDC) ligands exhibits a low voltage of 1.317 V to deliver a current density of 10 mA cm⁻². As a result, a high turnover frequency (TOF) of 0.15 s⁻¹ is achieved at a voltage of 1.4 V, which enables a urea degradation rate of 81.87% in 0.33 M urea solution. The combination of experimental characterization with theoretical calculation reveals that the Ni and Mn sites play synergistic roles in maneuvering the evolution of urea molecules and key reaction intermediates during the UOR, while the binary Ni/Mn sites in MOF offer the tunability for electronic structure and d-band center impacting on the intermediate evolution. This work provides important insights into active site design by leveraging MOF platform and represents a solid step toward highly efficient UOR with MOF-based electrocatalysts.

In-Plane Mott-Schottky Effects Enabling Efficient Hydrogen Evolution from Mo5 N6 -MoS2 Heterojunction Nanosheets in Universal-pH Electrolytes

Cost-effective electrocatalysts for the hydrogen evolution reaction (HER) spanning a wide pH range are highly desirable but still challenging for hydrogen production via electrochemical water splitting. Herein, Mo₅ N₆ -MoS₂ heterojunction nanosheets prepared on hollow carbon nanoribbons (Mo₅ N₆ -MoS₂ /HCNRs) are designed as Mott-Schottky electrocatalysts for efficient pH-universal HER. The in-plane Mo₅ N₆ -MoS₂ Mott-Schottky heterointerface induces electron redistribution and a built-in electric field, which effectively activates the inert MoS₂ basal planes to intrinsically increase the electrocatalytic activity, improve electronic conductivity, and boost water dissociation activity. Moreover, the vertical Mo₅ N₆ -MoS₂ nanosheets provide more activated sites for the electrochemical reaction and facilitate mass/electrolyte transport, while the tightly coupled HCNRs substrate and metallic Mo₅ N₆ provide fast electron transfer paths. Consequently, the Mo₅ N₆ -MoS₂ /HCNRs electrocatalyst delivers excellent pH-universal HER performances exemplified by ultralow overpotentials of 57, 59, and 53 mV at a current density of 10 mA cm^-2 in acidic, neutral, and alkaline electrolytes with Tafel slopes of 38.4, 43.5, and 37.9 mV dec^-1 , respectively, which are superior to those of the reported MoS₂ -based catalysts and outperform Pt in overall water splitting. This work proposes a new strategy to construct an in-plane heterointerface on the nanoscale and provides fresh insights into the HER electrocatalytic mechanism of MoS₂ -based heterostructures.

Recent Advances of Freestanding Cathodes for Li-S Batteries

Lithium-sulfur batteries (LSBs) with high energy density and low cost have been recognized as one of the most promising next-generation energy storage systems. Although it has taken decades of development, the practical application of LSBs has been hindered by several inherent obstacles, particularly the severe shuttle effect and sluggish reaction kinetics in the sulfur cathode. Various strategies have been proposed to address these problems via rational design of electrode materials and configurations. Freestanding sulfur cathode could be a promising strategy to improve the sulfur mass loading at the cathode level and energy density of LSBs. This minireview will briefly summary the recent advances in freestanding cathodes for LSBs. The advantages and disadvantages of various freestanding cathodes are discussed and the prospects for the development of flexible cathodes are envisioned.

Biofunctional Elements Incorporated Nano/Microstructured Coatings on Titanium Implants with Enhanced Osteogenic and Antibacterial Performance

Bone fracture is prevalent among athletes and senior citizens and may require surgical insertion of bone implants. Titanium (Ti) and its alloys are widely used in orthopedics due to its high corrosion resistance, good biocompatibility, and modulus compatible with natural bone tissues. However, bone repair and regrowth are impeded by the insufficient intrinsic osteogenetic capability of Ti and Ti alloys and potential bacterial infection. The physicochemical properties of the materials and nano/microstructures on the implant surface are crucial for clinical success and loading with biofunctional elements such as Sr, Zn, Cu, Si, and Ag into nano/microstructured TiO2 coating has been demonstrated to enhance bone repair/regeneration and bacterial resistance of Ti implants. In this review, recent advances in biofunctional element-incorporated nano/microstructured coatings on Ti and Ti alloy implants are described and the prospects and limitations are discussed.

A general approach towards carbonization of plastic waste into a well-designed 3D porous carbon framework for super lithium-ion batteries

Due to the ever-increasing plastic waste causing serious environmental problems, it is highly desirable to recycle it into high-value-added products, such as carbon nanomaterials. However, the traditional catalytic carbonization of hydrocarbon polymers is severely prohibited by the complexity of real-world plastic waste due to the existence of halogen-containing polymers. In this study, through a universal combined template based on magnesium oxide and iron(iii) acetylacetonate (Fe(acac)₃), a three-dimensional hollow carbon sphere/porous carbon flake hybrid nanostructure is prepared from carbonization of plastic waste with high yields (>70 wt%). This approach is not only suitable for hydrocarbon polymers, but also for halogen-containing polymers. Interestingly, the obtained advanced carbon framework exhibits excellent performance in lithium-ion batteries (802 mA h g^-1 after 500 cycles at 0.5 A g^-1). The present research paves a new avenue to upcycle plastic waste into a high value-added product.

Hierarchical 0D-2D Co/Mo Selenides as Superior Bifunctional Electrocatalysts for Overall Water Splitting

Development of efficient electrocatalysts combining the features of low cost and high performance for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) still remains a critical challenge. Here, we proposed a facile strategy to construct in situ a novel hierarchical heterostructure composed of 0D−2D CoSe₂/MoSe₂ by the selenization of CoMoO₄ nanosheets grafted on a carbon cloth (CC). In such integrated structure, CoSe₂ nanoparticles dispersed well and tightly bonded with MoSe₂ nanosheets, which can not only enhance kinetics due to the synergetic effects, thus promoting the electrocatalytic activity, but also effectively improve the structural stability. Benefiting from its unique architecture, the designed CoSe₂/MoSe₂ catalyst exhibits superior OER and HER performance. Specifically, a small overpotential of 280 mV is acquired at a current density of 10 mA·cm⁻² for OER with a small Tafel slope of 86.8 mV·dec⁻¹, and the overpotential is 90 mV at a current density of 10 mA·cm⁻² for HER with a Tafel slope of 84.8 mV·dec⁻¹ in 1 M KOH. Furthermore, the symmetrical electrolyzer assembled with the CoSe₂/MoSe₂ catalysts depicts a small cell voltage of 1.63 V at 10 mA·cm⁻² toward overall water splitting.

Two-Dimensional Transition Metal Chalcogenides for Alkali Metal Ions Storage

On the heels of exacerbating environmental concerns and ever-growing global energy demand, development of high-performance renewable energy-storage and -conversion devices has aroused great interest. The electrode materials, which are the critical components in electrochemical energy storage (EES) devices, largely determine the energy-storage properties, and the development of suitable active electrode materials is crucial to achieve efficient and environmentally friendly EES technologies albeit the challenges. Two-dimensional transition-metal chalcogenides (2D TMDs) are promising electrode materials in alkali metal ion batteries and supercapacitors because of ample interlayer space, large specific surface areas, fast ion-transfer kinetics, and large theoretical capacities achieved through intercalation and conversion reactions. However, they generally suffer from low electronic conductivities as well as substantial volume change and irreversible side reactions during the charge/discharge process, which result in poor cycling stability, poor rate performance, and low round-trip efficiency. In this Review, recent advances of 2D TMDs-based electrode materials for alkali metal-ion energy-storage devices with the focus on lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), potassium-ion batteries (PIBs), high-energy lithium-sulfur (Li-S), and lithium-air (Li-O₂ ) batteries are described. The challenges and future directions of 2D TMDs-based electrode materials for high-performance LIBs, SIBs, PIBs, Li-S, and Li-O₂ batteries as well as emerging alkali metal-ion capacitors are also discussed.

Lithiated NiCo2O4 Nanorods Anchored on 3D Nickel Foam Enable Homogeneous Li Plating/Stripping for High-Power Dendrite-Free Lithium Metal Anode

Lithium (Li) metal is one of the promising anode materials in the next-generation high-energy batteries, but Li dendrite growth and a big volume change during cycling result in low Coulombic efficiency (CE), short lifespan, and safety hazards, thereby impeding practical implementation of Li in rechargeable batteries. Herein, we report a highly stable and dendrite-free Li metal anode based on a three-dimensional (3D) conductive and lithiophilic scaffold comprising lithiated NiCo₂O₄ nanorods grown on nickel foam (LNCO/Ni). The nanorods grown on 3D Ni foam with a large surface area effectively reduce the averaged electrical current in the electrode, and the conformal Li₂O coating produced in situ on the lithiated NiCo₂O₄ nanorods provides the surface lithiophilicity enabling stable Li plating/stripping without Li dendrite growth even at a high current density of 5 mA cm^-2. The LNCO/Ni-Li anode shows a low voltage hysteresis of 16 mV, high CE of 98.7%, and stable cycling without obvious voltage fluctuation for over 500 cycles (1000 h) at a current density of 1 mA cm^-2. Specifically, for a scalable Li loading of 20 mA h cm^-2 on LNCO/Ni, no growth of Li dendrite and electrode thickness fluctuations are observed. The full cell consisting of the LNCO/Ni-Li anode and the LiFePO₄ cathode exhibits a high rate capability and CE as high as 99.6% for more than 160 cycles. Our study reveals a new strategy to develop stable Li-metal anodes for high-energy batteries.

Long-lasting bactericidal activity through selective physical puncture and controlled ions release of polydopamine and silver nanoparticles-loaded TiO2 nanorods in vitro and in vivo

Background: Titanium (Ti) implant-associated infection, which is mostly caused by bacterial adhesion and biofilm formation, may result in implant failure and secondary surgery. Thus it is an urgent issue to prevent bacterial infections at the earliest step.

Purpose: To develop a novel surface strategy of polydopamine (PDA) and silver (Ag) nanoparticle-loaded TiO₂ nanorods (NRDs) coatings on Ti alloy.

Materials and methods: Ag-TiO₂@PDA NRDs was fabricated on Ti alloy by hydrothermal synthesis. The antibacterial activity of Ag-TiO₂@PDA NRDs against Escherichia coli and methicillin-resistant Staphylococcus aureus were tested by FE-SEM, Live/Dead staining, zone of inhibition, bacteria counting method and protein leakage analysis in vitro. In addition, an implant infection model was conducted and the samples were tested by X-ray, Micro-CT and histological analysis in vivo. Besides, cell morphology and cytotoxicity of Mouse calvarial cells (MC3T3-E1) were characterized by FE-SEM, immunofluorescence and CCK-8 test in vitro.

Results: Our study successfully developed a new surface coating of Ag-TiO₂@PDA NRDs. The selective physical puncture of bacteria and controlled release of Ag+ ions of Ag-TiO₂@PDA NRDs achieved a long-lasting bactericidal ability and anti-biofilm activity with satisfied biocompatibility.

Conclusion: This strategy may be promising for clinical applications to reduce the occurrence of infection in the implant surgeries

Conductive Mesoporous Niobium Nitride Microspheres/Nitrogen-Doped Graphene Hybrid with Efficient Polysulfide Anchoring and Catalytic Conversion for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are promising next-generation energy storage devices because of their high energy density of 2600 Wh kg^-1. Efficient immobilization and fast conversion of soluble lithium polysulfide intermediates (LiPSs) are crucial to the electrochemical performance of Li-S batteries. Herein, we report a novel strategy to simultaneously achieve large capacity, high rate capability, and long cycle life by utilizing mesoporous niobium nitride microspheres/N-doped graphene nanosheets (NbN@NG) hybrids as multifunctional host materials for sulfur cathodes. The mesoporous NbN microspheres chemically immobilize LiPSs via Nb-S chemical bonding and catalytically promote conversion of LiPSs into insoluble Li₂S resulting in enhanced redox reaction kinetics. Moreover, the highly conductive NbN and N-doped graphene nanosheets provide rapid electron transport and consequently, the S/NbN@NG cathode demonstrates a large capacity of 948 mAh g^-1 at 1 C (1 C = 1650 mA g^-1), high rate capability of 739 mAh g^-1 at 5 C, and excellent cycle stability with a capacity decay of 0.09% per cycle for over 400 cycles. The results described here provide insights into the design of multifunctional host materials for high-performance Li-S batteries.