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Graphite anode materials and carbonate electrolyte have been the top choices for commercial lithium-ion batteries (LIBS) for a long time. However, the uneven deposition and stripping of lithium cause irreversible damage to the graphite structure, and the low flash point and high flammability of the carbonate electrolyte pose a significant fire safety risk. Here, we proposed a multifunctional electrolyte additive diphenylphosphoryl azide (DPPA), which can construct a solid electrolyte interphase (SEI) with high ionic conductivity lithium nitride (Li3N) to ensure efficient transport of Li+. This not only protects the artificial graphite (AG) electrode but also inhibits lithium dendrites to achieve excellent electrochemical performance. Meanwhile, the LIBS with DPPA offers satisfactory flame retardancy performance. The AG//Li half cells with DPPA-0.5M can still maintain a specific capacity of about 350 mAh/g after 200 cycles at 0.2 C. Its cycle performance and rate performance were better than commercial electrolyte (EC/DMC). After cycling, the microstructure surface of the AG electrode was complete and flat, and the surface of the lithium metal electrode had fewer lithium dendrites. Importantly, we found that the pouch cell with DPPA-0.5M had low peak heat release rate. When exposed to external conditions of continuous heating, DPPA significantly improved the fire safety of the LIBS. The research of DPPA in lithium electrolyte is a step towards the development of safe and efficient lithium batteries. [ABSTRACT FROM AUTHOR]

To explore the potential application of industrial waste, iron tailings powder, which is in combination with expandable graphite (EG), was adopted to improve the flame retardancy of rigid polyurethane foam (RPUF). The flame retardant performance, combustion performance, and gas products of composites were investigated. The flame retardant test indicated that 20 wt% MITS/EG increased the limiting oxygen index value of RPUF/MITS/EG composite to 23.3–26.6 vol% and passed the V-0. Thermogravimetric analysis test confirmed that MITS/EG improved the overall thermal stability of RPUF-4, and the residual char rate at 700 °C was increased to 35.76 wt%. The peak of heat release rate, total smoke release, and smoke factor of RPUF-4 were reduced by 61.55, 77.99, and 91.54%, respectively, compared with the pure sample, which significantly improved the fire safety of RPUF. Thermogravimetric–Fourier transform infrared spectrometer test implied that MITS/EG system reduced the release intensity of CO2, isocyanate compounds, and HCN in the composites. Scanning electron microscopy, Raman, and X-ray diffraction tests showed that MITS/EG promoted RPUF to form a heat-resistant and dense expanded char layer. [ABSTRACT FROM AUTHOR]

A high content of flame retardant in non‐combustible electrolytes leads to deterioration of the electrochemical performance of lithium‐ion batteries (LIBs). Besides, fire hazard of most non‐flammable electrolytes is studied in coin cell, for which it is impossible to reveal real performance. Thus, the stable interfacial, phosphorus‐fixed nonflammable gel polymer electrolyte (GPE) with low content of flame retardant (7.5 wt.%) has been designed by in situ polymerization of tri(acryloyloxyethyl) phosphate and triethylene glycol dimethacrylate in electrolyte. After being heated by fire for >10 s, the GPE is still not ignited. The average capacity attenuation rate of graphite//GPE//Li (0.008%) is much lower than that of the liquid electrolyte (0.039%). Besides, the nonflammable GPE based pouch cell with good flexibility and excellent fire safety is prepared. No fire, no thermal runaway and no electrolyte leakage occur for 1 Ah flexible pouch cell with 100% SOC. The mechanism for high safety of pouch cell has also been revealed. First the amount of combustible pyrolysis products from thermal degradation of GPE is reduced through forming P and F containing char. Second, the combustion of GPE is extinguished through OH free radical quenching effect of flame retardant molecular. This work provides a guideline for designing high‐safety LIBs. [ABSTRACT FROM AUTHOR]

Iron tailings (IT) is the remaining industrial solid waste after beneficiation. The accumulation of billion tons of tailings not only occupies valuable land resources but also causes serious environmental pollution and human harm. This work aims to explore the potential application of IT in flame retardant field. The modified iron tailings (MIT) were combined with aluminum hypophosphite (AHP) to prepare a series of TPU/AHP/MIT composites by melt blending method. Thermogravimetric (TGA) test indicated that MIT and AHP significantly improved the thermal stability of the composites. The char residue of TPU/AHP22.5/MIT2.5 was enhanced to 29.60 wt% compared with 27.51 wt% of TPU/AHP25. Cone calorimetry test (CCT) confirmed that PHRR and THR of TPU/AHP15/MIT10 were decreased by 88.4% and 55.2% compared with those of pure TPU. Adding 2.5 wt% MIT could reduce the gas production of the TPU/AHP system by 32.82%. Scanning electron microscopy (SEM) and Raman spectroscopy tests confirmed that AHP/MIT system could increase the thickness and graphitization degree of char residue for the TPU composites, and thus increase the thermal stability and fire resistance of the composites. Lastly, the possible fire retarding mechanism of TPU/AHP/MIT composites was illustrated. This work provided a novel strategy for utilization of IT. [ABSTRACT FROM AUTHOR]

A novel and highly effective flame retardant (FR), DOPO‐TPMP oligomer, was synthesized by a simple condensation of 4‐(hydroxymethyl)‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane‐1‐oxide and phosphorus oxychloride followed by a polycondensation reaction with 6‐(2,5‐dihydroxyphenyl)‐6H‐dibenzo[c,e][1,2]oxaphosphinine‐6‐oxide. The chemical structure of DOPO‐TPMP was well characterized using Fourier transform infrared and NMR spectra. DOPO‐TPMP was used as an additive‐type FR for epoxy resin (EP). The FR properties of the resultant EP composites were investigated by limiting oxygen index (LOI) test, UL‐94 vertical burning test and cone calorimeter measurements. Specifically, the EP composite containing 10.0% DOPO‐TPMP achieved a LOI value of 36.1%, V‐0 rating in the UL‐94 test and a 58% reduction in peak heat release rate. Further mechanism analysis attributed the enhanced flame retardancy to the increased char yield on the addition of DOPO‐TPMP. © 2019 Society of Chemical Industry A novel oligomeric flame retardant, DOPO‐TPMP, was synthesized, which imparted high flame‐retardant performance to epoxy resins. [ABSTRACT FROM AUTHOR]

In this work, two kinds of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based phosphonamidate flame retardants named 4,4′-diamino-diphenyl methane (DDM)-DOPO and morpholine (MPL)-DOPO are successfully synthesized by the classic Atherton–Todd reaction, and their chemical structures are characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Epoxy composites containing DDM-DOPO or MPL-DOPO are prepared, which still retain relatively high transparency compared with pure epoxy resin (EP). Its fire behavior is studied in terms of vertical burning test (UL-94), limiting oxygen index (LOI), and cone calorimeter tests. The LOI values can achieve 30% and UL-94 test past V-0 rating for DDM-DOPO-modified epoxy composites with 0.25 wt% phosphorus content. The cone calorimeter results indicate that the modified epoxy composites can release less heat and smoke compared with pure EP. Also, thermal degradation behavior and flame-retardant mechanism of epoxy composites are investigated by thermogravimetric analysis and thermogravimetric analysis/infrared spectrometry. The results indicate that two DOPO-based phosphonamidates show a significant gaseous-phase effect on reducing the release of combustible volatiles. [ABSTRACT FROM AUTHOR]

In this work, we reported the synthesis, characterization of Ce-doped titania nanotubes (Ce-TNTs), and application in flame retardancy of an intumescent flame-retardant polystyrene (PS/IFR) system. The flame retardancy of polystyrene (PS) composite that was composed of pentaerythritol, microencapsulated ammonium polyphosphate, and PS was enhanced significantly by adding a small amount (0.1 wt%) of (Ce-TNTs). The thermal properties of the flame-retardant PS were investigated by thermogravimetric analysis, limiting oxygen index (LOI), vertical burning test (UL-94), scanning electronic microscopy, dynamic mechanical thermal analysis, and the real-time Fourier transform infrared spectrometry (FTIR). The maximal decomposition rate temperature of PS/IFR containing Ce-TNTs in air is much higher than that of other PS composite without Ce-TNTs. The LOI value of PS/IFR that contained 0.1 wt% of Ce-TNTs was increased from 27.0 to 28.5, and the UL-94 rating was also enhanced to V-0 from no rating when the total loading of additive was the same. The real-time FTIR showed that the degradation process was changed after the addition of TNTs. All results indicated that Ce-TNTs had a significant synergistic effect on the flame retardancy of PS/IFR. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, the effect of organo-modified montmorillonite (OMMT) on a novel intumescent flame retardant (IFR) system was studied in poly(1,4-butylene terephthalate) (PBT) composites containing microencapsulated ammonium polyphosphate (MAPP) and melamine cyanurate (MC). Nanocomposite morphology was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal decomposition analysis was studied via thermogravimetric analysis (TGA). Combustion behavior was investigated by microcombustion calorimeter (MCC), limited oxygen index (LOI), and UL-94 test. Residues obtained after samples treated in muffle furnace at 500°C under air condition for 10 min were analyzed through X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). It was found that the addition of OMMT improved the flame retardancy of PBT/IFR composites significantly. A mass of microcomposite structure particles formed in the heating or combustion process of PBT/IFR/OMMT nanocomposites were found for the first time in the SEM images, which is strong evidence to confirm the migration or accumulation of montmorillonite and carbonaceous-silicate materials during the heating or combustion process. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The phosphorus- and nitrogen-containing monomer, acryloxyethyl phenoxy phosphorodiethyl amidate (AEPPA), was synthesized and characterized. Poly(St-co-AEPPA)/α-zirconium phosphate (α-ZrP) nanocomposites with different amounts of α-ZrP were then prepared by in situ radical bulk copolymerization. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the α-ZrP layers were exfoliated in the polymer matrix. Improvements in thermal stability and char residues of the copolymer and nanocomposites were observed by thermogravimetric analysis (TGA). The incorporation of AEPPA can reduce the flammability of polystyrene (PS). Moreover, further reductions were observed when α-ZrP was added. The reduction in flammability was attributed to a lower maximum mass loss rate and more char residues of the nanocomposites involved in thermal degradation. [Copyright &y& Elsevier]

• Two phosphorus-nitrogen type flame retardants N-DOPO and PPDAT that contain triazole units were designed and synthesized. • N-DOPO and PPDAT endowed epoxy resin (EP) composites with an improved fire safety reflected in low flammability, light smoke, and less emission of toxic gases during the combustion of EP composites. • EP/PPDAT composite could catalyze the formation of dense continuous carbon layer, with efficient condensed phase flame retardant mechanism. Epoxy resin (EP) is one kind of thermosetting polymer with prominent physical and chemical properties and has been extensively used in various aspects of the world. Nevertheless, its intrinsic inflammability impedes its application in some occasions. Therefore, the flame retardant treatment of EP is of much significance. In this work, two novel phosphorus-nitrogen type flame retardants N-DOPO and PPDAT based on triazole were prepared. The distribution of molecular weight of the as-prepared polymeric flame retardant PPDAT was characterized by gel permeation chromatography (GPC) analysis. The number-average molecular weight (M n), the weight-average molecular weight (M w) and the distribution index (D) value of PPDAT were 8849, 9324 and 1.05, respectively. The results of flame retardant tests evinced that after introducing 7.5 wt% N-DOPO, a V-0 rating in the UL-94 test and a desirable limiting oxygen index (LOI) value of 33.5% were achieved. With 7.5 wt% PPDAT added, this composite only reached V-1 level with a LOI value of merely 30%, indicating that in contrast with PPDAT, N-DOPO presents better flame retardant efficiency for epoxy resin. Through the analysis of the products in combustion process, it was determined that EP/PPDAT composite could catalyze the formation process of dense continuous carbon layers, with efficient flame retardant effect in the condensed phase. This work provided the strategy of introducing triazole units into flame retardants and would help sprout a new series of flame retardants. [Display omitted] [ABSTRACT FROM AUTHOR]

• The fire-proof TD-GPE with + 3 and + 5 phosphorus valence states was synthesized via in-situ polymerization. • The TD-GPE shows highly stable cycle performance for NCM811 and LFP full soft pack batteries (1 Ah). • The "jet fire" and leakage were suppressed in the thermal abuse test of NCM811 battery by using flame-retardant TD-GPE. Lithium-ion batteries (LIBs) have been widely used today owing to portability, high energy storage, and reusability. However, commercial liquid electrolytes in LIBs possess intensive mobility and terrible flammability. Accordingly, leakage, combusting, and even exploding can frequently occur when LIBs work under abuse conditions. Herein, a novel flame-retardant gel polymer electrolyte (GPE) containing + 3 and + 5 phosphorus valence states of phosphorus structures was designed by in-situ thermal polymerization of tri(acryloyloxyethyl) phosphate (TAEP), diethyl vinylphosphonate (DEVP), and pentaerythritol tetraacrylate in electrolytes. After being ignited by fire, this GPE extinguished quickly with a combusting time of only 0.9 s, showing much lower flammability. Besides, the GPE is compatible with graphite anode, LiFePO 4 (LFP), and even LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes. The as-assembled LFP and NCM811-based pouch cells (1 Ah-type) with TD-GPE achieved stable cycling, maintaining 88.52 % and 95.2 % of the initial capacities, respectively after 200 and 190 cycles at 0.5C. Moreover, the as-prepared TD-GPE dramatically reduced the fire hazard of NCM811 batteries without sacrificing the electrochemical performance. The thermal abuse test demonstrates that the leakage and combustion of NCM811||TD-GPE||Graphite pouch cell could be significantly suppressed in the test process, indicating that battery safety improves significantly via the combined use of different phosphorus valence structures. This is because the + 5 phosphorus valence of TAEP promoted the formation of carbon layers, and the + 3 phosphorus structure in DEVP captured free radicals by quenching effect. This work paves a different path for designing safe and high-performance GPEs in LIBs based on gaseous-phase and condensed-phase mechanisms. [ABSTRACT FROM AUTHOR]

Fire hazards are a primary concern in aircraft accidents, and controlling combustible materials is pivotal in managing cabin fire risks. This work aims to elucidate the impact of widespread measures that introduce phosphorus-based flame retardants (PFRs) on the fire safety of carbon fiber epoxy composites (CF/EP). Firstly, the hazardous indicators for flame retardant CF/EP composites exhibit two categories of optimization and degradation, which are caused by the intrinsic feature, pyrolysis characteristics and chemical valence states of PFRs. Secondly, the fire hazards of composites are assessed by fusing the analytic network process and information weights guided by Nash Equilibrium theory. The method combines the merits of subjective and objective weights from dimensions of intrinsic hazards, interrelationships and data dispersion of indicators. Finally, the assessed fire hazard rankings under 35 and 65 kW/m2 both are EP > CF/EP16%DOPO-HQ > CF/EP > CF/EP7%DPO. In conclusion, DOPO-HQ (+1) primarily increases the fire hazard of CF/EP due to gas-phase flame-retardant effects, while DPO (+3) predominantly reduces the fire hazard of CF/EP by contributing to condensed-phase effects. This work highlights the contradictory effects of PFRs on the fire safety of CF/EP composites due to structure and thermal stability. The proposed ANP and IW hybridization method provides a theoretical foundation for selecting flame retardants and assessing material fire hazards comprehensively. [ABSTRACT FROM AUTHOR]

Abstract Lithium-ion rechargeable batteries have attracted considerable research enthusiasm and meanwhile achieved great successes in industry during the past three decades. To meet the ever-increasing demand of batteries safety especially for the application in electric vehicles and energy storage devices, phosphorus-based flame retardants as additives have been developed and investigated. Herein, trivalent and pentavalent phosphorus-based flame retardants are purposely employed to comparably investigate the influence on safety and electrochemical performance of Li-ion batteries. The results show that pentavalent phosphorus-based electrolytes possess wider electrochemical windows and can endure higher voltage compared to trivalent phosphorus-based electrolytes, revealing that pentavalent phosphorus-based flame retardants are more suitable as efficient additives for cathode materials systems. Interestingly, trivalent phosphorus flame retardants may act as solid electrolyte interphase layer formers, which can be decomposed and meanwhile promote the formation of stable solid electrolyte interphase layer on the surface of graphitic anode materials even with a low loading. Moreover, it is worth noting that both trivalent and pentavalent phosphorus flame retardants show potential for application in high rate performance. This work can provide help for scientific research or industry in the study of phosphorus-containing flame retardants for batteries. Highlights • Pentavalent phosphorus shows better affinity with cathodes than graphitic anode. • Trivalent phosphorus promotes the formation of SEI layer on graphitic electrode. • Phosphorus additives may endow batteries with high rate performance. [ABSTRACT FROM AUTHOR]

Lithium-Sulfur (Li-S) battery is a potential alternative energy storage system owing to its high theoretical capacity, low cost, and eco-friendly features. However, the commercialization of Li-S battery has been hindered by the notorious "shuttle effect". To overcome the above-mentioned long-standing problem, herein, an advanced separator modified by N and P heteroatoms co-doped carbon frameworks with confined Co 2 P nanoparticles (named Co 2 P/Co/C) has been successfully prepared. The introduction of functional coating can obviously enhance the thermal stability of separator. To be specific, it showed higher initial decomposition temperature (475 ℃) and lower maximum mass loss rate (1.755 % ℃ − 1 ) values than the Celgard separator (400 ℃ and 2.915 % ℃ − 1 , respectively). Notably, when kindled separators directly, the modified separator can quench by itself with many residual remains. In addition, the engineered functional layer possesses the capability of capturing lithium polysulfides (LiPSs), and then confines them within the cathode region so that the "shuttle effect" can be restrained effectively. After assembling the modified separator in the Li-S cell, compared with the cell with Celgard separator of low initial specific discharge capacity (730 mAh g−1), the cell with Co 2 P/Co/C separator delivered a superior initial discharge capacity of 1310 mAh g−1 at 0.5 C. Also, the modified cell can perform remarkably enhanced rate performances. In addition, As a consequence of these merits, the modified separator with improved thermal stability, preferable fire safety, and satisfied electrochemical performances shows significant guiding value for advancing the practical application of Li-S batteries. The work mechanism of a fresh Li-S battery and a modified Li-S battery. [Display omitted] • Materials compose of heteroatoms doped carbon frameworks and Co 2 P nanoparticles. • Modified layers can trap polysulfides by physical and chemical synergistic effects. • The novel flame retardant separator shows higher fire safety. [ABSTRACT FROM AUTHOR]

The cell with flame retardant separator shows promoted rate property as well as inhibited dendrites growth. [Display omitted] • A MOFs-derived hierarchical composite (NSPCFS@CoS 2) modified separator is designed. • This designed separator possesses markedly improved flame retardancy. • The effective suppression on shuttle behavior of polysulfides is realized. • The suppressed growth of lithium dendrites corroborates the higher battery safety. Considering the unprecedented advantages such as superb theoretical capacity, high energy density and low cost, lithium-sulfur batteries (LSBs) have been under spotlight in past several years. Nevertheless, limited by its intrinsic drawbacks of highly insulating character, serious shuttle effect and lithium dendrites growth, there is still a long way from large-scale application of LSBs. Here, a polyacrylonitrile@metal organic frameworks (PAN@MOFs) composite-derived heteroatoms doped carbon@encapsulated CoS 2 nanoparticles (NSPCFS@CoS 2) modified separator is designed to surmount these issues. Notably, the modified separator shows improved flame retardancy. By using this separator, the effective suppression on shuttle behavior as well as boost in polysulfides conversion kinetics are realized, which can be assigned to the integrative superiorities of conductive carbon fiber network, electrocatalytic activity, polar-polar interaction and Lewis acid-base interaction. The cell with modified separator shows an initial discharge capacity of 1140.7 mAh g−1. After running for 100 cycles, a high capacity of 631.6 mAh g−1 is retained. Notably, the inhibited growth of lithium dendrites is also obtained, indicating the promoted battery safety. Overall, this work may provide useful inspirations for the utilization of MOFs-derived hierarchical composite in implementing safer high-performance LSBs. [ABSTRACT FROM AUTHOR]

• Hyperbranched phosphorus-containing flame-retardant grafted POP is prepared. • POP and P-POP based separators with high fire safety and good electrochemical properties are reported. • P-POP/polyolefin composite separator can be compressed during assembly. • It can not only guarantee the capacity of lithium ion battery, but also load with more flame-retardant P-POP. Melamine-based porous organic polymer (POP) is a three-dimensional organic porous material with good thermal stability, large specific surface area, abundant polar groups and low crystallinity. Here, melamine-based POP and flame retardant grafted melamine-based POP (P-POP) is prepared. Compressible POP and P-POP based lithium battery separators with high fire safety and good electrochemical properties are reported first. The compressibility, cycle, rate, size stability and fire safety performances of samples are investigated. The mechanism for good electrochemical property and high fire performance of P-POP based separator is proved. The thick P-POP/polyolefin composite separator with more flame retardant forms a good intumescent protective char between anode and cathode during fire hazard, resulting in increasing internal resistance and preventing thermal runaway. However, the P-POP/polyolefin composite separator is compressible. P-POP/polyolefin composite separator can be compressed during assembly to guarantee the capacity of lithium ion battery. [ABSTRACT FROM AUTHOR]