Flame-retardant ammonium polyphosphate/MXene decorated carbon foam materials as polysulfide traps for fire-safe and stable lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries are one of the most promising modern-day energy supply systems because of their high theoretical energy density and low cost.However,the development of high-energy density Li-S batteries with high loading of flammable sulfur faces the challenges of electrochemical performance degradation owing to the shuttle effect and safety issues related to fire or explosion accidents.In this work,we report a three-dimensional(3D)conductive nitrogen-doped carbon foam supported electrostatic self-assembled MXene-ammonium polyphosphate(NCF-MXene-APP)layer as a heat-resistant,thermally-insulated,flame-retardant,and freestanding host for Li-S batteries with a facile and costeffective synthesis method.Consequently,through the use of NCF-MXene-APP hosts that strongly anchor polysulfides,the Li-S batteries demonstrate outstanding electrochemical properties,including a high initial discharge capacity of 1191.6 mA h g^(-1),excellent rate capacity of 755.0 mA h g^(-1)at 1 C,and long-term cycling stability with an extremely low-capacity decay rate of 0.12%per cycle at 2 C.More importantly,these batteries can continue to operate reliably under high temperature or flame attack conditions.Thus,this study provides valuable insights into the design of safe high-performance Li-S batteries.

Leakage Proof,Flame-Retardant,and Electromagnetic Shield Wood Morphology Genetic Composite Phase Change Materials for Solar Thermal Energy Harvesting

Phase change materials(PCMs)offer a promising solution to address the challenges posed by intermittency and fluctuations in solar thermal utilization.However,for organic solid-liquid PCMs,issues such as leakage,low thermal conductivity,lack of efficient solar-thermal media,and flamma-bility have constrained their broad applications.Herein,we present an innova-tive class of versatile composite phase change materials(CPCMs)developed through a facile and environmentally friendly synthesis approach,leveraging the inherent anisotropy and unidirectional porosity of wood aerogel(nanowood)to support polyethylene glycol(PEG).The wood modification process involves the incorporation of phytic acid(PA)and MXene hybrid structure through an evaporation-induced assembly method,which could impart non-leaking PEG filling while concurrently facilitating thermal conduction,light absorption,and flame-retardant.Consequently,the as-prepared wood-based CPCMs showcase enhanced thermal conductivity(0.82 W m^(-1)K^(-1),about 4.6 times than PEG)as well as high latent heat of 135.5 kJ kg^(-1)(91.5%encapsula-tion)with thermal durability and stability throughout at least 200 heating and cooling cycles,featuring dramatic solar-thermal conversion efficiency up to 98.58%.In addition,with the synergistic effect of phytic acid and MXene,the flame-retardant performance of the CPCMs has been significantly enhanced,showing a self-extinguishing behavior.Moreover,the excellent electromagnetic shielding of 44.45 dB was endowed to the CPCMs,relieving contemporary health hazards associated with electromagnetic waves.Overall,we capitalize on the exquisite wood cell structure with unidirectional transport inherent in the development of multifunctional CPCMs,showcasing the operational principle through a proof-of-concept prototype system.

Flame-retardant oligomeric electrolyte additive for self-extinguishing and highly-stable lithium-ion batteries:Beyond small molecules

Preparing both safe and high-performance lithium-ion batteries(LIBs) based on commonly used commercial electrolytes is highly desirable,yet challenging.To overcome the poor compatibility of conventional small-molecular flame-retardants as electrolyte additives for safe LIBs with graphite anodes,in this study,we propose and design a novel low-cost flame-retardant oligomer that achieves an accurate and complete reconciliation of fire safety and electrochemical performance in LIBs.Owing to the integration of phosphonate units and polyethylene glycol(PEG) chains,this oligomer,which is a phosphonatecontaining PEG-based oligomer(PPO),not only endows commercial electrolytes with excellent flame retardancy but also helps stabilize the electrodes and Li-ion migration.Specifically,adding 15 wt% of PPO can reduce 70% of the self-extinguishing time and 54% of total heat release for commercial electrolytes.Moreover,LiFePO_(4)/lithium and graphite/lithium cells as well as LiFePO_(4)/graphite pouch full cells exhibit good long-term cycling stability.

Flame-retardant Mechanism of Magnesium Oxychloride in Epoxy Resin

Flame-retardant mechanism of magnesium oxychloride （M OC） in EP was in-vestigated by limiting oxygen index （LOI）, XRD, SEM, TG-DTG and DSC. The results show that MOC performed well as an inorganic flame-retardant in EP. When the content of MOC is 50%, the LOI of EP reaches 29.6% and mass of residual char reaches 9.6%. The flame retarde mechanism of MOC is due to the synergies of diluting, cooling, catalyzing char forming and obstructing effects.

Comparison of Flame-retardancy Property and Mechanism between a Phosphate Ester and a Phosphoramine Flame-retardants

A halogen-free flame-retardant (hydroquinone bis (N,N’-diarylphosphoramidate),4N-HDP) containing phosphorus-nitrogen was synthesized.Its structure was characterized by infrared spectroscopy (IR),nuclear magnetic resonance (^(1)H-NMR and^(31)P-NMR).Thermogravimetric analysis (TG),limiting oxygen index (LOI),UL-94 vertical burning test (UL-94),thermogravimetric-infrared instrument (TG-IR) and scanning electron microscopy (SEM) were used to compare the flame-retarding performance and mechanism of hydroquinone bis (diphenyl phosphate) (HDP) and 4N-HDP.TG,IR and TG-IR were used for comparative analysis,indicating that both HDP and 4N-HDP are flame-retardants,and the gas phase and condensed phase act synergistically.In the pyrolysis process,it is divided into two steps:the first step is the breakage of large molecules to small molecules;the second step is the gasification and carbonization of small molecules,and eventually produces phosphate ester and non-flammable gases.Through the comparison of various results,it could be found that 4N-HDP has better flame-retarding performance compared to HDP in the composite with polycarbonate (PC).

3D flame-retardant skeleton reinforced polymer electrolyte for solid-state dendrite-free lithium metal batteries

For solid polymer electrolytes(SPEs),improving their mechanical and electrochemical properties is the key to obtaining batteries with higher safety and higher energy density.Herein,a novel synergistic strategy proposed is preparing a 3D flame-retardant skeleton(3DPA)and adding nano-multifunctional fillers(Li-ILs@ZIF-8).In addition to providing mechanical support for the polyethylene oxide(PEO)matrix,3DPA also has further contributed to the system’s flame retardancy and further improved the safety.Simultaneously,the electrochemical performance is fully guaranteed by rigid Li-ILs@ZIF-8,which provides fast migration channels forLi^(+),reduces the crystallinity of PEO and effectively inhibits lithium dendrites.The limiting oxygen index of the optimal sample(PL3Z/PA)is as high as 20.5%,and the ionic conductivity reaches 2.89×10^(-4) and 0.91×10^(-3) S cm^(-1) at 25 and 55°C,respectively.The assembled Li|PL3Z/PA|Li battery can be cycled stably for more than 1000 h at a current density of 0.1 m A cm^(-2) without short circuit being pierced by lithium dendrites.The specific capacity of the LFP|PL3Z/PA|Li battery was 160.5 m Ah g^(-1) under a current density of 0.5 C,and the capacity retention rate was 90.0%after 300 cycles.

A new flame-retardant polymer electrolyte with enhanced Li-ion conductivity for safe lithium-sulfur batteries

Flame-retardant polymer electrolytes(FRSPEs)are attractive due to their potential for fundamentally settling the safety issues of liquid electrolytes.However,the current FRSPEs have introduced large quantity of flame-retardant composition which cannot conduct lithium ions,thus decreasing the Li-ion conductivity.Here,we synthesize a novel liquid monomer 2-((bis((2-oxo-1,3-dioxolan-4-yl)methoxy)phosphoryl)oxy)ethyl acrylate(BDPA)for preparing FRSPE by in-situ polymerization,in which PBDPA polymer can not only conduct lithium ions,but also prevent burning.The prepared FRSPE demonstrated outstanding flame-retardant property,favorable lithium-ion conductivity of 5.65×10^(-4) S cm^(-1) at ambient temperature,and a wide electrochemical window up to 4.5 V.Moreover,the Li/in-situ FRSPE/S@pPAN cell exhibited favorable electrochemical performances.We believe that this work provides an effective strategy for establishing high-performance fireproof quasi-solid-state battery system.

Property of Polyimide/Flame-Retardant Viscose Blended Fabrics

Although polyimide fibers are excellent intrinsic flame-retardant fibers, their price is so high that they are rarely used in clothing. To expand their application, the polyimide fibers were blended with flame-retardant viscose fibers at a ratio of 30∶70, and the blended yarns were woven with flame-retardant polyester filaments. Fabrics with different parameters, including fabric weaves, warp yarn densities, and fabric layers, were designed, and the effects of those fabric parameters on mechanical properties and flame-retardant properties were tested and analyzed. The results show that the tearing load of the fabrics is affected by fabric weaves, warp yarn densities, and fabric layers, and the tearing load of the weft mountain weave fabric and the twill weave fabric is higher than that of the plain weave fabric. The bursting load of the fabric increases with the increase of warp yarn densities and layers. Among the tested fabric samples, the triple-layer twill fabric has the best flame-retardant performance, which meets the standard of flame-retardant protective fabric Grade B1 level. The research of this paper would provide guidance for the development and production of polyimide blended fabrics.

SYNTHESES AND CHARACTERIZATION OF CYCLIC ORGANIC BORONATE ESTERS AS FLAME-RETARDANTS

Some organoboron compounds as flame-retardants for fiber materials were prepared.Flame-retarding properties of these compounds determined by the Oxygen-Index Method weregood.These new compounds were characterized by IR,~1H NMR spectrum and elementalanalysis.

Enhanced High-Temperature Cycling Stability of Garnet-Based All Solid-State Lithium Battery Using a Multi-Functional Catholyte Buffer Layer

The pursuit of safer and high-performance lithium-ion batteries(LIBs)has triggered extensive research activities on solid-state batteries,while challenges related to the unstable electrode-electrolyte interface hinder their practical implementation.Polymer has been used extensively to improve the cathode-electrolyte interface in garnet-based all-solid-state LIBs(ASSLBs),while it introduces new concerns about thermal stability.In this study,we propose the incorporation of a multi-functional flame-retardant triphenyl phos-phate additive into poly(ethylene oxide),acting as a thin buffer layer between LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)cathode and garnet electro-lyte.Through electrochemical stability tests,cycling performance evaluations,interfacial thermal stability analysis and flammability tests,improved thermal stability(capacity retention of 98.5%after 100 cycles at 60℃,and 89.6%after 50 cycles at 80℃)and safety characteristics(safe and stable cycling up to 100℃)are demonstrated.Based on various materials characterizations,the mechanism for the improved thermal stability of the interface is proposed.The results highlight the potential of multi-functional flame-retardant additives to address the challenges associated with the electrode-electrolyte interface in ASSLBs at high temperature.Efficient thermal modification in ASSLBs operating at elevated temperatures is also essential for enabling large-scale energy storage with safety being the primary concern.

Strategies for flame-retardant polymer electrolytes for safe lithiumbased batteries

The advancement of lithium-based batteries has spurred anticipation for enhanced energy density,extended cycle life and reduced capacity degradation.However,these benefits are accompanied by potential risks,such as thermal runaway and explosions due to higher energy density.Currently,liquid organic electrolytes are the predominant choice for lithium batteries,despite their limitations in terms of mechanical strength and vulnerability to leakage.The development of polymer electrolytes,with their high Young’s modulus and enhanced safety features,offers a potential solution to the drawbacks of traditional liquid electrolytes.Despite these advantages,polymer electrolytes are still susceptible to burning and decomposition.To address this issue,researchers have conducted extensive studies to improve their flame-retardant properties from various perspectives.This review provides a concise overview of the thermal runaway mechanisms,flame-retardant mechanisms and electrochemical performance of polymer electrolytes.It also outlines the advancements in flame-retardant polymer electrolytes through the incorporation of various additives and the selection of inherently flame-retardant matrix.This review aims to offer a comprehensive understanding of flame-retardant polymer electrolytes and serve as a guide for future research in this field.

Porous Flame-retarded Asphalt Pavement for Highway Tunnel

A new way to improve the tunnel fire protection by using flame-retarded porous asphalt pavement containing ATH powders was introduced. Based on the miniature burning test designed and conducted, the burning time and temperature of porous asphalt （PA） and flame-retarded porous asphalt （FRPA） were studied comparing with cement concrete pavement, dense-graded lIMA and SMA. Results of burning test and pavement performance test indicate that FRPA is appropriate and suitable as the pavement material of highway tunnel.

Research on Alkaline Filler Flame-Retarded Asphalt Pavement

Used as flame returdant of tunnel asphalt pavement, organic bromides produce a large amount of poisons and smoke in construction and flame retardation stage. The alkaline filler was found to replace mineral filler, and the flame- retarded asphalt mixtures were produced. Experimental results show that these asphalt mixtures are smoke restrained ; the performances and construction technology of asphalt pavement are not influenced; also the alkaline filler is of low-price. So this kind of flame-retarded asphalt mixtures is suitable for tunnel patement.

Three-in-one fire-retardant poly(phosphate)-based fast ion-conductor for all-solid-state lithium batteries

The development of flame retardant or nonflammable electrolytes is the key to improve the safety of lithium batteries,owing to inflammable organic solvents and polymer matrix in common liquid and polymer electrolytes regarded as the main cause of battery fire.Herein,a series of solid-state polyphosphate oligomers(SPPO)as a three-in-one electrolyte that integrated the roles of lithium salt,dissociation matrix,and flame retardant were synthesized.The well-designed SPPO electrolytes showed an optimal ionic conductivity of 5.5×10^(-4)S cm-1at 30℃,an acceptable electrochemical window up to 4.0 V vs.Li/Li+,and lithium ion transference number of 0.547.Stable Li-ion stripping/plating behavior for 500 h of charge-discharge cycles without internal short-circuit in a Li|SPPO|Li cell was confirmed,together with outstanding interface compatibility between the SPPO electrolyte and lithium foil.The optimal Li|SPPO|LiFePO4cell presented good reversible discharge capacity of 149.4 mA h g-1at 0.1 C and Coulombic efficiency of 96.4%after 120 cycles.More importantly,the prepared SPPO cannot be ignited by the lighter fire and show a limited-oxygen-index value as high as 35.5%,indicating splendid nonflammable nature.The SPPO could be a promising candidate as a three-in-one solid-state electrolyte for the improved safety of rechargeable lithium batteries.

Preparation and properties of flame-retardant rubber composites based on steel slag filler

Ultrafine steel slag powder(shield powder)was prepared by grinding ordinary steel slag with a functional compound.As a substitute for aluminum hydroxide,the shield powder was combined with rubber to prepare flame-retardant composites.Vulcanization tests showed that the incorporation of shield powder enhances the crosslinkage of the composite and speeds up the curing rate.The gaseous products formed in the pyrolysis process are mainly hydrocarbons.Mechanical and combustion tests revealed that the introduction of shield powder improves flame-retardant performance without sacrificing mechanical properties.Specifically,the optimum substitution ratio of shield powder for aluminum hydroxide is 50.0%.In this case,the composite has the highest degree of graphitization and exhibits excellent flame-retardant performance.

气相色谱-质谱联用法测定塑料产品中的溴系阻燃剂

Brominated flame-retardant,such as deca-BDE,TBBP-A,TBBP-A-bis is one kind of the additives of plastic product for flame retardation.European has published a direction to restrict the used amount of brominated flame-retardant,because of their toxicity.The present work reports a GC-MS method for the determination of the brominated retardants.The method meets the requirements of the direction 2002/95/EC,and has been applied to the real sample analysis.

Ni Flower/MXene-Melamine Foam Derived 3D Magnetic/Conductive Networks for Ultra-Efficient Microwave Absorption and Infrared Stealth

The development of multifunctional and efficient electromagnetic wave absorbing materials is a challenging research hotspot.Here,the magnetized Ni flower/MXene hybrids are successfully assembled on the surface of melamine foam(MF)through electrostatic self-assembly and dip-coating adsorption process,realizing the integration of microwave absorption,infrared stealth,and flame retardant.Remarkably,the Ni/MXene-MF achieves a minimum reflection loss(RLmin)of−62.7 dB with a corresponding effective absorption bandwidth(EAB)of 6.24 GHz at 2 mm and an EAB of 6.88 GHz at 1.8 mm.Strong electromagnetic wave absorption is attributed to the three-dimensional magnetic/conductive networks,which provided excellent impedance matching,dielectric loss,magnetic loss,interface polarization,and multiple attenuations.In addition,the Ni/MXene-MF endows low density,excellent heat insulation,infrared stealth,and flame-retardant functions.This work provided a new development strategy for the design of multifunctional and efficient electromagnetic wave absorbing materials.

Polyimide-silver nanocomposite containing phosphine oxide moieties in the main chain:Synthesis and properties

New flame-retardant polyimide-silver nanocomposite containing phosphine oxide moiety in the main chain was synthesized by a convenient ultraviolet irradiation technique.A precursor such as AgNO_3 was used as the source of the silver particles.Polyimide 6 as a source of polymer was synthesized by polycondensation reaction of bis（3-aminophenyl） phenyl phosphine oxide 4 with pyromellitic anhydride 5 in the presence of iso-quinoline as base and in m-cresol solution.The resulting composite film was characterized by FTIR spectroscopy,X-ray diffraction（XRD）,transmission electron microscopy（TEM）,thermogravimetry（TGA） and differential scanning calorimetry（DSC）.The average size of the nanometer Ag particles is about 10 nm.The temperature of 5 and 10%weight loss and also the char yield at 600℃of polyimide-silver nanocomposite 6a were higher than the pure PI 6.

A Furan-based Phosphaphenanthrene-containing Derivative as a Highly Efficient Flame-retardant Agent for Epoxy Thermosets without Deteriorating Thermomechanical Performances

In order to reduce greenhouse gas emissions, developing flame retardants from bio-based resources has aroused extensive interest in recent years. In this work, we utilized furfural(biomass) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO) to synthesize a biobased co-curing agent(FGD) to combine with 4,4'-diaminodiphenyl methane(DDM) for obtaining a low-phosphorus loading flame-retardant epoxy thermosets. The introduction of FGD decreased the activation energy of the curing progress, enhanced the mechanical properties of the epoxy thermosets, and did not affect the glass transition temperature of the epoxy thermosets. EP-5.0 had a lower thermal degradation rate and a doubled char yield compared with EP-0. The phosphorus content of EP-5.0 was only 0.45 wt%, while EP-5.0 reached the UL-94 V-0 rating with a high LOI value of 32%. Compared with EP-0, the PHRR of EP-2.5 and EP-5.0 decreased by 22.3% and 31.3%, respectively. The SEM results showed that the addition of FGD made the char residues more uniform and denser, which could effectively prevent combustible volatiles from escaping from the degradation area to the flame area and isolate the heat transfer so that the epoxy thermosets had an excellent flame-retardant performance.

Single-step flash-heat synthesis of red phosphorus/ graphene flame-retardant composite as flexible anodes for sodium-ion batteries

Red phosphorus （RP） has attracted considerable attention as the anode for high-performance Na-ion batteries, owing to its low cost and high theoretical specific capacity of -2,600 mAh/g. In this study, a facile single-step flash-heat treatment was developed to achieve the reduction of graphene oxide （GO） and the simultaneous deposition of RP onto the reduced graphene oxide （rGO） sheets. The resulting RP/rGO composite was shown to be a promising candidate for overcoming the issues associated with the poor electronic conductivity and large volume variation of RP during cycling. The RP/rGO flexible film anode delivered an average capacity of 1,625 mAh/g during 200 cycles at a charge/ discharge current density of 1 A/g. Average charge capacities of 1,786, 1,597, 1,324, and 679 mAh/g at 1, 2, 4, and 6 A/g current densities were obtained in the rate capability tests. Moreover, owing to the RP component, the RP/rGO film presented superior flame retardancy compared to an rGO film. This work thus introduces a highly accessible synthesis method to prepare flexible and safe RP anodes with superior electrochemical performance toward Na-ion storage.