Excellent Flame Retardancy Research Articles

All-Polymer Composite Film with Outstanding Mechanical, Thermal Conductive, and EMI Shielding Performances.

Robust polymer-based composites with high thermal conductivity (TC) and electromagnetic interference shielding effectiveness (EMI SE) hold great promise for applications in rapidly developing electronics. Traditional composites containing inorganic fillers often suffer from increases in processing difficulty, density, and significant deterioration in mechanical properties. Herein, we report for the first time a flexible multilayered all-polymer composite of poly(p-phenyl-2,6-phenylene bisoxazole) (PBO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), featuring excellent mechanical strength of 203.9 MPa, in-plane TC of 21.9 W/mK, EMI shielding effectiveness (SE) of 44.2 dB, high-temperature stability, and flame retardancy. The excellent TC, mechanical strength, and flame retardancy of PBO, the remarkable EMI shielding performance of PEDOT:PSS, and the π-π stacking interactions between adjacent layers contribute to the comprehensive properties, which outperform most of the traditional composites of polymers and inorganic fillers reported so far. This full-polymer design may pioneer a new strategy for the preparation of robust and lightweight multifunctional composites.

Preparation of Phosphorus/Hollow Silica Microsphere Modified Polyacrylonitrile-Based Carbon Fiber Composites and Their Thermal Insulation and Flame Retardant Properties

Since thermal insulation materials with a single function cannot satisfy the increasing requirements for complex usage, the combination of thermal insulation with flame retardancy is desirable in multiple applications. Herein, phosphorous-containing flame retardant modifier (5.0 wt.%, 9.0 wt.%, and 13.0 wt.%) and hollow silica microsphere (130 nm of diameter) were composited with polyacrylonitrile-based carbon nanofibers via electrospinning technique. Electrospun phosphorous/silica/carbon nanofibers (P/HSM/CF) exhibited a uniform and clear fibrous structure (508, 170, and 1550 nm of average fiber diameter) with modified uniform and complete spherical silica. Reduced thermal conductivity (39.9–41.2 mW/m/K) and enhanced limiting oxygen index (29.5–33.5%) were achieved, enabling fire protection grade of fiber membrane from UL-94 V-1 grade to UL-94 V-0 grade efficiently. Moreover, favorable tensile strength (8.64–9.27 MPa) and elongation at break (43.28–48.54%) were obtained, presenting expected applications in structural components. The findings of this work provided a valuable reference for the fabrication of carbon nanofiber-based thermal insulation materials with excellent flame retardant and mechanical properties.

Flexible Inverse Opal Structural Color Films with High Strength and Harsh Environment Stability.

Flexible photonic crystals (PCs) constructed by PCs and special polymers are very promising to achieve a combination of vivid structural colors, mechanical robustness, and environment stability. However, PCs that incorporate polymer binders are still susceptible to destruction and subsequent loss of structural color when subjected to significant external forces or harsh environments. Besides, because most of these polymers are highly flammable, crucial fire safety is difficult to be guaranteed in the application of these materials. In this study, we report a poly(m-phenyleneisophthalamide) inverse opal (PMIA IO) structural color film through a SiO2 PC template sacrificing method. Benefiting from the high rigid PMIA molecular structural configuration, the PMIA IO films are able to maintain their structural colors even in harsh conditions, such as large tensile stress, high and low temperatures, potent acids and bases, and ultraviolet radiation. More attractively, the PMIA IO films demonstrate excellent flame retardancy, with the limiting oxygen index (LOI) and flame retardant rating reaching 28 vol % and V0, respectively. We believe that the flexible structural color films with high strength, harsh environment stability, and flame retardancy, which are difficult for other structural color materials to possess simultaneously, have great potential for special applications in fire protection, national defense, aviation, marine, and aerospace fields.

Nanostructured poplar wood via delignification and ammonium dihydrogen phosphate-SiO2 modification towards remarkable flame retardant performance: Synergistic effect and enhanced mechanism

Developing efficient methods to prepare high-performance flame retardant and smoke suppression wood is crucial for the application. Herein, nanostructured poplar wood (DWI-4) with remarkable flame retardant and smoke suppression performance was fabricated by impregnating ammonium dihydrogen phosphate (ADP) and nano-silica (SiO2) into delignified wood (DW-4). With the delignification treatment, lignin was partially removed, and numerous pores and cracks were developed on the cell wall of wood, allowing more ADP-SiO2 particles to be impregnated into wood. As a result, ADP-SiO2 particle was not only anchored in the lumens (pores) of wood, but also was penetrated and embedded into the cell wall, achieving the synergistic modification of the lumen and cell wall of wood. As anticipated, the produced DWI-4 featured outstanding flame retardant and smoke suppression performance. The peak heat release rate (pHRR) of DWI-4 was as low as 38.2 kW m−2, which was only 8 % of that of natural wood (NW). And the total heat release (THR) and total smoke production (TSP) demonstrated reductions of 73.9 % and 64.4 % comparing to NW. Moreover, the compressive strength of DWI-4 increased by 31.4 % comparing to NW. The structure of residual char of DWI-4 was more stable and the gas intensity produced by the combustion of DWI-4 decreased remarkably. Therefore, the synergy of delignification and ADP-SiO2 impregnation significantly enhanced the flame retardant and smoke suppression performance of wood and the enhanced mechanism was revealed. The nanostructured poplar wood with excellent flame retardant and smoke suppression performance was prepared, providing an effective method for the functional improvement of wood and expanding the fields of application.

Preparation of phosphorus-nitrogen synergistic flame retardant cellulose composite aerogel from waste cotton/phytic acid/acrylamide

Cellulose aerogel is a green and biodegradable material, but the high flammability of cellulose aerogel hinders its development. In order to expand the application range of cellulose aerogel, it is necessary to improve the flame retardancy of cellulose aerogel. In this paper, cellulose hydrogels were prepared by decolorizing waste cotton fabrics (WCF) and dissolving them in 1-butyl-3-methylimidazole chloride salt ([Bmim]Cl)/DMSO. The cellulose hydrogels were impregnated in aqueous phytic acid (PA)/acrylamide (AM) solution for a period of time and then heated and treated. A cellulose composite aerogel with excellent flame retardant properties was successfully prepared by using in situ polymerization. The results show that the cellulose composite aerogel has a porous structure and good thermal stability, and the residual carbon content in the air at 800 °C is >2.86 %. At the same time, it has excellent flame retardancy, the ultimate oxygen index (LOL) is >40, and the vertical combustion carbon length is <3.5 cm. The thermal insulation performance has also been improved, and the composite aerogel with a height of 1 cm has a temperature difference of 40.2 °C between the upper and lower surfaces on the 80 °C heating table.

Enhanced thermal and mechanical properties of flame-retardant expandable graphite modified silk fibroin-based rigid polyurethane foam

At present, in order to reduce the environmental pollution caused by the use of petrochemical products, the preparation of flame-retardant polyurethane foam (PUF) using green raw materials is increasingly attracting widespread attention. A biomass protein-based green flame-retardant rigid PUF (RPUF) with expandable graphite (EG) and silk fibroin (SF) was prepared in a one-step process. Thermal stability, combustion characteristics and compression properties of modified RPUFs were investigated by thermogravimetric analysis, cone test, limiting oxygen index (LOI) test, UL-94 vertical burning test and mechanical compression test. The RPUF with 10 wt% EG (RPUF-SF/EG10) exhibited superior heat resistance, with the highest initial decomposition temperature (Ti), integral programmed decomposition temperatures (IPDT) and activation energy (E). And RPUF-SF/EG10 had the lowest peak heat release rate (PHRR) and total heat release (THR), and it also showed the highest LOI and had a flammability rating of V-0. In Addition, the apparent density and compressive strength of RPUF-SF/EG10 were the largest among the four EG-added materials. The results indicated that RPUF-SF/EG10 had excellent thermal stability, flame retardancy and compression resistance, which was attributed to the synergistic effect of SF and EG in the system. This provided a valuable reference for the development of new, environmentally friendly and high-performance RPUFs.

Constructing a multifunctional reactive MXene-based additive for micro-crosslinking polyurea elastomer to achieve superior mechanical properties and enhanced fire safety

The widespread application of polyurea (PUA) in protective coatings typically requires excellent flame retardancy due to real-world usage scenarios. However, the addition of flame retardant additives often compromises the material’s mechanical properties. In this study, a multifunctional reactive additive, MX-SP-NH2, was creatively prepared by covalently grafting spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC) onto MXene (Ti3C2Tx) surfaces, followed by the introduction of 1,3-propanediamine (PDA) by the reaction with SPDPC. MX-SP-NH2 was then incorporated into PUA, participating in its crosslinking process and significantly enhancing both its mechanical strength and flame retardancy. Compared to the control PUA sample, the micro-crosslinked PUA sample with just 1.0 wt% MX-SP-NH2 demonstrated a 184.3% increase in tensile strength, a 126.1% increase in elongation at break, and a 436.3% increase in toughness. The flammability characterization revealed that the peak heat release rate, peak smoke production rate, and peak CO production rate were reduced by 31.7%, 28.9%, and 61.5%, respectively, indicating a substantial improvement in fire safety. Additionally, the flame retardant PUA-based flexible strain sensors demonstrated stable electrical signal responsiveness. This work has opened up new potential applications of PUA in flexible electronics.

Flame retardant, transparent, low dielectric and low smoke density EP composites implemented with reactive flame retardants containing P/N/B

For the purpose of investigating the modified flame-retardant epoxy resin (FREP) with the low smoke density release during combustion, the flame retardant containing P/N/B elements named DBT was synthesized with the raw materials of 4-Acetylphenylboronic acid, 3,5-diaminotriazole and DOPO. The DBT was added as a co-curing agent to an amine-cured epoxy resin system, and based on the DSC results of the resin, it was revealed that -NH- in the structure of the DBT was capable of facilitating EP curing. With the introduction of DBT, the transparency of FREP samples was slightly affected. On account of the excellent flame retardancy exerted by the DBT in the FREP system, the FREP samples reached the V-0 grade in UL-94 testing with an LOI of 35.9% at 5 wt% DBT addition. Meanwhile, the results of the cone calorimetry test demonstrated that in comparison with the epoxy resin, the PHRR, THR and av-EHC of the EP/DBT7.5 sample decreased by 34.0%, 35.4% and 18.68%, respectively. The DBT was effective in reducing the smoke density of EP, and the EP/DBT7.5 sample attained the HL1 level for DS (4) and VOF4. The chemical analyses for residual char revealed that DBT was mainly employed for flame retardancy and smoke suppression by forming P/B-containing chars in the condensed phase. There was no loss of mechanical properties of the FREP samples as the rigid groups were present in the DBT structure. Furthermore, it was noted that the FREP samples exhibited a decrease in dielectric loss and dielectric constant as the content increased.

Construction of multi-functional silicone rubber/reduced graphene oxide/multi-walled carbon nanotube composites with segregated structure by surfactant-free Pickering emulsion method

Polymer composites with segregated structure (PC–S) have the advantages of low filler usage and excellent functionality. Emulsion blending combined with direct molding technology is the main method for the preparation of PC-S. However, due to the high fluidity of low-viscosity silicone rubber (SR), PC-S cannot be prepared by this technique. In addition, surfactants affect the heat resistance of the final SR composites (SRC). In order to solve the above problems, in this study, a Pickering emulsification combined with pre-crosslinking technology for SR was successfully developed by using graphene oxides (GO)/multi-walled carbon nanotubes (MWCNTs) hybrid fillers (GM) as emulsifiers, and SR/reduced GO (RGO)/MWCNTs composites with segregated structure (SSGM) were prepared. When RGO content is 4.5 wt%, MWCNTs content is 3.2 wt%, SSGM shows the highest electrical conductivity of 12.5 S/m, the highest electromagnetic interference shielding efficiency (EMI SE) of 41.4 dB, and an excellent flame retardant performance. The whole preparation process avoids the use of organic solvents and surfactants, which reduces the production cost of SSGM and the environmental pollution, and provides a feasible preparation route for the industrialized production of SSGM.

Caramel doped with aromatic compounds as halogen- and phosphorus-free flame-retardant strategy for wool fabric

The development of halogen- and phosphorus-free flame-retardant strategies is urgently needed in textile industry. In this study, a caramel product doped with aromatic compounds was developed via caramelization and aldol reactions using glucose and p-phthaldialdehyde. The modified caramel (Car@PDA) was subsequently used as a sustainable approach to improve flame retardancy of wool fabric. The flame retardancy, washing durability, heat generation, and flame-retardant mode of action of Car@PDA on wool fabric were investigated. The modified wool fabrics showed excellent flame retardancy, with the limiting oxygen index increasing to 32.5 % and the damaged length decreasing to 10.1 cm, with good self-extinguishing capacity. Car@PDA could combine with wool fibers through Schiff base reaction and electrostatic attraction, so the modified wool fabrics still self-extinguished and met the B1 flame-retardant requirements after 10 washing cycles. The modified wool showed significantly decreased heat release capacity and fire growth rate, suggesting high fire safety. Car@PDA promoted the decomposition of the fabric to form char barrier, thereby achieving an effective flame-retardant effect. In addition, the Car@PDA modification had a minimal effect on the tensile strength and handle of wool fabric. This study provides an innovative way to create bio-based, halogen- and phosphorus-free flame-retardants for protein wool fabrics.

A P,N flame retardant containing flexible chain segments, imparting excellent toughness and flame retardancy to epoxy resins

AbstractIn order to enhance the flame retardancy of epoxy resin (EP) without affecting its mechanical properties, a phosphorus‐nitrogen synergistic flame retardant (MPCD) was synthesized in this paper by using melamine, paraformaldehyde, 9,10‐dihydro‐9‐oxa‐10‐phospha‐phenanthrene‐10‐oxide (DOPO) and cashew phenol as the raw materials, which was applied to the Ep in order to improve its flame retardancy and toughness. Experiments have shown that only 5% content of MPCD added into the EPs could achieve a significant LOI of 35.8% and successfully obtained a V‐0 rating in UL‐94 testing. In contrast, the PHRR with 5% additional MPCD was 456.4 kW/m2 and the THR was 80.2 MJ/m2, which were 52.6% and 29.4% lower than that of pure EPs, respectively. The PHRR of pure EPs was 963.1 kW/m2 and THR was 113.6 MJ/m2, which indicated that the addition of MPCD improved the EP system's flame retardant performance. The impact strength of pure EPs was 13.5 KJ/m2, and 5% addition of MPCD resulted in a 99% increase in the impact strength of EP/MPCD cured samples up to 26.9 KJ/m2, which was explained by the cashew phenol moiety's flexible chain segments. Furthermore, it is discovered by researching its flame‐retardant mechanism that the addition of MPCD may significantly improve the carbon layer's capacity to form char and maintain thermal stability. It can also efficiently trap free radicals and dilute the combustible gases produced during combustion. The flame retardant can increase the overall safety of the EP system by acting as a biphasic flame retardant in both the gas and the solidified phases at the same time.

High rubber elasticity and thermal conductivity in plasticized polyvinyl chloride film with flame retardancy and smoke suppression properties

AbstractFor hydrogenated nitrile‐butadiene rubber (HNBR) modified polyvinyl chloride (PVC), magnesium hydroxide and antimony trioxide are frequently employed as flame retardants. Fume silica is thought to be useful reinforced agent for rubber as well as efficient flame retardant for polymer‐based composites. The plasticized PVC and HNBR blend in this work were combined with three fillers mentioned above to create rubber‐plastic composites that performed well overall, with a notable improvement in combustion. The limiting oxygen index of the composites increased from 23.7% to 33.8% with no droplets falling during combustion, the smoke density rating decreased from 23.8% to 7.9%, and the maximum smoke density dropped from 95.5% to 15.5%. The cone calorimetry test findings revealed that the three fillers simultaneously prevented the emission of smoke and heat from combustion. High thermal conductivity is typically linked to excellent flame retardancy. The thermal conductivity of composites rose from 0.193 to 0.583 W m−1 K−1 with the addition of fillers. Furthermore, the low glass transition temperature and permanent set of improved composites reflect its softness and rubber elasticity. Thermogravimetric analysis was used to examine the thermal stability of the composites in nitrogen and air, and the results indicated the addition of fillers improved the thermal stability.

Biomimetic Ambient‐Pressure‐Dried Aerogels with Oriented Microstructures for Enhanced Electromagnetic Shielding

AbstractOriented aerogels, emerging as a new generation of lightweight electromagnetic interference (EMI) materials, often face complex synthesis processes. While creating an orderly oriented microstructure for EMI aerogels through ambient pressure drying (APD) shows promise, it remains a significant challenge. Here, inspired by the directional grown structure of the plant, a new strategy that employs rapid precursor orientation followed by slow cross‐linking to achieve the APD of directional EMI aerogels is proposed. This approach demonstrates that low‐temperature oriented polymerization of polyaniline enables strong cross‐linking with poly(3,4‐ethylenedioxythiophene) and alginate, forming a robust conductive directional skeleton and mitigating surface tension issues during mild drying. The resulting aerogel features high conductivity (48.84 S m−1), excellent flame retardancy, and impressive compressive strength. Notably, its sturdy frame allows for further enhancement with other functional materials, such as Mxene, through re‐processing and re‐drying. The tree‐branch‐like aerogel achieves a significantly improved EMI shielding effectiveness of 50.3 dB across an ultrawideband range of 8.2–40 GHz. This strategy offers a new idea for the straightforward preparation of functional aerogels with programmability and oriented microstructures using ambient drying.

A novel phosphorus-containing pyridinium porous organic framework with flame retardancy for enhancing efficiency and safety of solid-state polymer electrolyte

The development of solid-state polymer electrolytes (SPEs) is aimed to obtain electrolyte materials with higher ionic conductivity, better mechanical properties, and greater flame retardancy. Based on the above considerations, a phosphorus-containing cationic porous organic polymer (ZR-POF) is prepared through “one-pot” three-component polymerization and incorporated as a filler to prepare poly(ethylene oxide) (PEO)-based SPEs. By padding ZR-POF into PEO, the ionic conductivity of SPEs is significantly improved, especially the PEO-10 % ZR-POF electrolyte exhibits the highest ionic conductivity at 90 °C (1.26 × 10−3 S cm−1). And due to the nanosheet characteristics of ZR-POF, SPEs exhibit excellent mechanical properties, could form a more stable interface with the metal anode. It is worth noting that the introduction of phosphorus endows SPEs with excellent flame retardant properties, achieving rapid self-extinguishing within 12 s under intense combustion. Therefore, the resultant battery based on PEO-10 % ZR-POF electrolyte exhibits excellent electrochemical performance, with a capacity maintained at 591.8 mAh g−1 and a capacity attenuation rate of 0.027 % over 500 cycles at 1 C.

Weakly solvated electrolyte enables the robust solid electrolyte interface on SiOx anodes for lithium-ion battery

Silicon oxide (SiOx) anodes are considered to be the promising alternative to graphite anodes for lithium-ion batteries. However, the traditional carbonate electrolyte fails to generate the effective solid electrolyte interface (SEI) on SiOx anodes to well adapt the large volume expansion of SiOx particles. Herein, a weakly solvated perfluorinated electrolyte with dual lithium salts was designed to match SiOx anodes. The perfluorinated solvent with weakened solvation ability and the strong coordination of Li+-DFOB− and Li+-TFSI− lead to an anion-dominated solvated shell, which induces the formation of inorganics-rich SEI. The high-strength bonds (Li-F, B-F, B-O, B-N et al.) enable high mechanical strength and rapid ion migration of the SEI film, thereby effectively accommodating the volume expansion of SiOx and avoiding continuous decomposition of the electrolyte. Furthermore, as designed electrolyte also shows excellent flame retardancy and high voltage stability. Consequently, the SiOx anode exhibits remarkably improved cycling performance in contrast to that in traditional carbonate electrolyte, maintaining 1073.7 mAh/g after 300 cycles at 1.0 A/g when paired with metal Li, and presents excellent compatibility with commercial cathodes including LiFePO4 and LiNi0.8Co0.1Mn0.1O2. This work provides a new inspiration and path for the design of electrolyte highly matched with silicon oxide anodes.

Structural Design of Hybrid Fillers in a Polymer Matrix for Advanced Electromagnetic Interference Shielding

The rapid development of modern advanced electronic systems has created a pressing need for multifunctional polymer composites that can withstand external adversities such as electromagnetic waves, flames, and mechanical stresses. Although these requirements can be satisfied by incorporating different types of fillers, high filler loadings often lead to issues such as poor processability and increased material costs. Herein, a multifunctional polyamide‐6 composite is introduced using a carbon‐fiber flame‐retardant hybrid filler to design a next‐generation electromagnetic interference (EMI) shielding system. Based on the synergistic effect of the functionality and structural arrangement of these fillers in the composite, the EMI shielding system demonstrates high EMI shielding performance, improved mechanical properties, and excellent flame retardancy despite the low filler content. The scalability and multifunctionality of the proposed system highlight its potential for use in next‐generation applications, such as electric vehicles, aerospace, and 5G/6G telecommunications.

Zr4+ and Al3+ coordinated cross-linked conductive collagen fibers/solvent-free polyurethane foam with ultra-low reflective electromagnetic shielding properties

In recent years, electromagnetic shielding materials with low reflectance have developed rapidly. However, high material cost, poor bonding fastness, weak mechanical properties and other problems seriously limit its effect in practical use. In this work, flexible conductive collagen fibers (CLF-Zr4+/Al3+-CNTs) were prepared using chromium tanned waste leather as ingredient, carbon nanotubes (CNTs) as conductive filler and transition metal ions as coordination crosslinking agents, and their molecular dynamics were investigated by quantum chemical simulation software. On this basis, a flexible conductive foam with the double layer and double core-clad structure containing carbon nanotubes was constructed using the solvent-free polyurethane (SFPU) chemical foaming technology, and their electromagnetic shielding properties and reflectance were studied. The experiment results showed that when the ratio of CLF-Zr4+/Al3+-CNTs to SFPU polyol is 1:9 and the impregnation times of CNTs are 2, the loading capacity of CNTs in conductive foam is 0.14 mg/cm3, the electrical conductivity is 57.8 S/m, and the thermal conductivity is 0.061 W/(m·K). Meanwhile, when the thickness is 3 cm, the electromagnetic shielding performance is 42.09 dB, and the reflection efficiency is 0.66 %, the lowest reflection efficiency reaches 0.16 % in the experiment. The mechanism of electromagnetic shielding in conductive foams with the double layer and double core-clad structure has been further explored. The experiment results proved that the flexible conductive foam has excellent mechanical properties, stability, heat insulation and flame retardant properties, and has excellent electromagnetic shielding and low reflection characteristics due to its abundant holes, functional group, interface and hierarchical structure.

A P/Si-containing flame retardant towards simultaneous improvement of the toughness, transparency and fire safety of polycarbonate

Polycarbonate (PC) is a commonly used engineering plastic, but its poor flame retardancy limits its use. In this study, a DOPO-based flame-retardant (DOPO-TMTA) containing P and Si elements was synthesized via a simple method involving 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 2, 4, 6-trivinyl-2, 4, 6-trimethylcyclotrisiloxane (TMTA). The PC/mDOPO-TMTA (m = 4, 6, 8) composites were prepared by melt blending PC with different loadings of DOPO-TMTA. The prepared PC/DOPO-TMTA composites had excellent flame retardancy while maintaining good transparency. The limiting oxygen index (LOI) of PC/8DOPO-TMTA reached 32.5 % and achieved a UL-94 V-0 rating. Moreover, cone calorimetry tests revealed that, compared with those of pure PC, the peak heat release rate (PHRR) and total heat release (THR) of PC/8DOPO-TMTA decreased by 39.0 % and 38.1 %, respectively. Compared with pure PC, PC/mDOPO-TMTA also maintained good mechanical properties, and the tensile and impact strengths were slightly improved. The synergistic flame retardancy of DOPO-TMTA on P/Si elements for the PC matrix was revealed by condensed phase and gas phase product analysis. This work provides a good reference for the preparation of PC composites with high transparency and excellent comprehensive properties.

Unlocking Mechanism of Anion and Cation Interaction on Ion Conduction of Polymer Based Electrolyte in Metal Batteries.

Polymer based electrolyte shows advantages in compatibly improving safety and interface stability of batteries, while its limited ion conductivity and transfer number make it difficult to apply it in batteries with high energy density. Herein, by designing four crosslinking polyesters with different electron withdrawing group (EWG), it is found that strengthening the binding of EWG to anion for weakening the binding of anion to Li+ is critical for high Li+ transfer number (tLi+) and ionic conductivity of electrolyte. As a result, poly(2,2,3,3-tetrafluoropropyl methacrylate) (PTFM) based gel polymer electrolyte (GPE) shows an ionic conductivity of 0.78 mS cm-1 and a tLi+ of 0.85, much higher than those of poly(methyl methacrylate) (PMMA) without EWG. Moreover, PTFM based GPE shows excellent flame retardancy property. Li||PTFM||NCM811 batteries with an ultrahigh capacity of 5.5 mAh cm-2 show stable cycles of 5 times to that of Li||PMMA||NCM811. Moreover, the assembled graphite||PTFM||NCM811 pouch cell shows a capacity retention rate of 92% after 500 cycles. This work clarifies the mechanism of cation||anion interaction on ionic conductivity of GPE, which is important to develop high-performance devices with good safety and flexibility.

Unlocking Mechanism of Anion and Cation Interaction on Ion Conduction of Polymer Based Electrolyte in Metal Batteries

Polymer based electrolyte shows advantages in compatibly improving safety and interface stability of batteries, while its limited ion conductivity and transfer number make it difficult to apply it in batteries with high energy density. Herein, by designing four crosslinking polyesters with different electron withdrawing group (EWG), it is found that strengthening the binding of EWG to anion for weakening the binding of anion to Li+ is critical for high Li+ transfer number (tLi+) and ionic conductivity of electrolyte. As a result, poly(2,2,3,3−tetrafluoropropyl methacrylate) (PTFM) based gel polymer electrolyte (GPE) shows an ionic conductivity of 0.78 mS cm−1 and a tLi+ of 0.85, much higher than those of poly(methyl methacrylate) (PMMA) without EWG. Moreover, PTFM based GPE shows excellent flame retardancy property. Li||PTFM||NCM811 batteries with an ultrahigh capacity of 5.5 mAh cm−2 show stable cycles of 5 times to that of Li||PMMA||NCM811. Moreover, the assembled graphite||PTFM||NCM811 pouch cell shows a capacity retention rate of 92% after 500 cycles. This work clarifies the mechanism of cation||anion interaction on ionic conductivity of GPE, which is important to develop high‐performance devices with good safety and flexibility.