Vinylidene Fluoride-co-hexafluoropropylene) (P Research Articles

3D Printed P(VdF‐HFP)/SBA‐15 composite‐based gel polymer electrolyte versus commercial celgard: A comparative investigation on thermal stability and electrochemical performance for lithium‐ion battery application

AbstractThe current work reports on tailoring of 3D printed gel polymer electrolyte (GPE) employing poly(vinylidene fluoride‐co‐hexafluoropropylene) P(VdF‐HFP) as the host matrix and mesoporous Santa Barbara Amorphous‐15 (SBA‐15) mesoporous sieve as ceramic filler. Further, this work envisages an investigation on its physicochemical properties, thermal shrinkage behavior, and electrochemical performance. An effort has been undertaken to formulate 3D printable P(VdF‐HFP)/SBA‐15 composite‐based GPE ink with suitable rheological properties. The breath figure method is followed to investigate the influence of 1‐methyl‐2‐pyrrolidinone (NMP)/tetrahydrofuran (THF) mixture as a solvent on the porosity of 3D printed GPE, through which enhanced porosity is evident from scanning electron microscopy (SEM) analysis. The morphological analysis further confirms the hybrid porous structure facilitated by the addition of SBA‐15 into the P(VdF‐HFP) matrix. The 3D printed P(VdF‐HFP)/SBA‐15 (10%) composite‐based GPE shows promising ionic conductivity in the order of 0.2 × 10−4 S/cm at room temperature and demonstrates excellent dimensional thermal stability up to 175°C. The electrochemical measurement of 3D printed GPE is tested separately using 3D printed cathode half‐cell (3D printed LFP vs. Li+) and 3D printed anode half cell (3D printed LTO vs. Li+) with GPE as separator. Further, also tested with conventionally prepared electrode and the coin cell studies show discharge capacity of 3D printed P(VdF‐HFP)/SBA‐15 (10%) composite‐based GPE is comparable to commercial celgard separator. All these features speculate that the 3D printed fabricated in the current work may find potential application in lithium‐ion battery.

Significantly enhanced permittivity and suppressed loss of P(VDF-HFP)-based composites by introducing PPy@BT-OH fillers

Polymer-based composites with high dielectric permittivity (high-k) are extensively utilized in embedded capacitors, pulse power supplies and radio frequency filter, etc. However, the enhancement of permittivity often comes at the price of elevated loss, which greatly diminishes the energy conversion efficiency and stability of the device. Herein, we loaded hydroxylated barium titanate (BT-OH) onto polypyrrole nanowire (PPy) to prepare a kind of PPy@BT-OH fillers and further incorporated them into Poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) polymer. Gaining from the stronger interfacial polarization effect and the hindrance to the development of conductive network triggered by PPy@BT-OH fillers, a significantly enhanced permittivity of ∼ 209.2 @ 10 kHz accompanied by a relatively low loss (tan δ ∼ 0.14 @ 10 kHz) was simultaneously realized in PPy@BT-OH/P(VDF-HFP) composite with 8 wt% filler contents.

The flexoelectric properties of various polymers and energetic composites

Electroactivity of polymers used in energetic materials may result in charge separation that could result in safety concerns (unintentional ignition) or be exploited for multifunctional applications. We measured the flexoelectric properties of several polymers and energetic composites including poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)], nanosized aluminum (nAl)/P(VDF-TrFE), poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)], micron aluminum (μAl)/P(VDF-HFP), hydroxyl-terminated polybutadiene (HTPB), ammonium perchlorate (AP)/HTPB, μAl/AP/HTPB, polytetrafluoroethylene (PTFE), and polydimethylsiloxane (PDMS). The presence of flexoelectricity in PTFE (Teflon®) and the relatively high flexoelectric coefficient of P(VDF-HFP) (Viton®) measured in this work may help explain accidents involving the production and use of Magnesium-Teflon-Viton (MTV) that in many instances have been attributed to electro-static discharge. The addition of aluminum nanopowders to the P(VDF-TrFE) increased the flexoelectric coefficient by ∼30%. However, the addition of aluminum micrometer particles (10 wt. %) to P(VDF-HFP) decreased the effective flexoelectric coefficient, while an increase was observed when the aluminum loading was increased from 10 to 20 wt. %. The effective flexoelectric coefficient of HTPB and two propellant compositions (AP/HTPB and μAl/AP/HTPB) were measured to be in the same range as each other. The effect of particle addition (nAl, μAl, and AP) on flexoelectricity was different depending on the binder, further illustrating the complexity of flexoelectric properties in composite energetics. This may be somewhat explained by competing effects where particle additions (nAl, μAl, and AP) create additional strain gradients that contribute to flexoelectricity, but the particle additions also replace the mass of flexoelectric polymer binders (P(VDF-TrFE, P(VDF-HFP), and HTPB) with particles (nAl, μAl, and AP) that are less flexoelectric.

Highly efficient and versatile daytime radiative cooler based on optimized polymer-ceramic composite fabricated via facile process

Radiative cooling is a carbon-free, zero energy technology that can substitute various energy-consuming cooling systems such as air conditioners and auto-chillers for cooling heat-generating machines. Previous reports on radiative cooling have focused mainly on the cooling performance, thereby overlooking the applicability, structural complexity, manufacturing complexity, and certain physical properties of the cooler. In this study, we present an efficient, applicable, and facile-fabricated radiative cooler composed of poly(vinylidene fluoride-co-hexafluoro propene) (P(VDF-HFP)) and alumina (Al2O3). Apart from being fabricated in the form of a freestanding sheet with 97.5% solar reflectance and 94.8% infrared (IR) emissivity, the P(VDF-HFP)/Al2O3-based radiative cooler (PARC) can be applied to various solid substrates via simple coating techniques. This shows that the PARC can be introduced in architecture, clothing, and other fields that demand cooling. The cooling performance of PARC is experimentally proven by a sub-ambient temperature drop of 10.1 °C during daytime and the cooling power of the PARC is calculated to be 125.6 Wm-2 under the AM1.5 global spectrum, which is superior to that of previously reported radiative cooling emitters.

Effect of Hot Pressing on the Optical, Thermal, and Dielectric Properties of Solution Cast Prepared Nanocomposite Films Based on a Poly(Vinylidene Fluoride-co-Hexafluoropropylene) and Poly(Ethylene Oxide) Blend Matrix with Dispersed Zinc Oxide Nanoparticles

In our research described herein, the hot pressing treatment at 90 °C under 2 tons of pressure on solution cast polymer nanocomposite (PNC) films based on a host matrix of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and poly(ethylene oxide) (PEO) with varying polymer blend compositions (20, 50, and 80 wt% P(VDF-HFP) or PEO) and 2 wt% zinc oxide (ZnO) nanofiller, was performed; the effects of this treatment and the composition variations on the optical, thermal, and dielectric properties was explored. The ultraviolet-visible wavelength range study revealed slightly reduced absorbance and a little increased energy band gap after the hot pressing of the nanocomposite films. Differential scanning calorimetry of the solution cast-hot pressed (SC-HP) PNC films explained the reduced thermal stability of the poly(ethylene oxide) crystallites and also the degree of crystallinity. The broadband dielectric measurements of these materials, at 27 °C, confirmed significant changes in various dielectric polarization processes, demonstrating a large redistribution of constituent interfaces by the hot press treatment. Additionally, the 90 °C hot pressed PNC film of equal polymer compositional ratio was further hot pressed at 130 °C and 160 °C, step by step, and characterized to examine the variations in dielectric properties. The properties of these thermally treated composite films are discussed concerning their use for flexible device applications.

ZnO nanofiller concentrations modified P(VDF-HFP)/PEO polymer matrix-based nanocomposites of enhanced optical and dielectric properties for emerging optoelectronic and energy storage devices

Wide bandgap metal oxide nanoparticles incorporated polymer blend matrix-based polymer nanocomposites (PNCs) are established as innovative multifunctional and properties tunable materials in the dimensional design and fabrication of promising performance extensive flexible type advanced devices. For further progress in these materials, herein, the detailed structural and promising properties of solution-cast prepared ternary PNC films, composed of poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP)/ poly(ethylene oxide) PEO (50/50 wt%) host matrix and zinc oxide (ZnO) nanofiller (0, 1, 2, 5, and 10 wt%), are characterized. A sequence of employed experimental techniques, namely SEM, XRD, FTIR, and DSC, confirm that the surface morphology, polymorphic crystallographic character, polymer-polymer interactions, polymer-nanoparticle interfaces, crystalline phase thermal transitions, and degree of crystallinity of these PNCs largely affected with varying nanofiller concentrations. The optical study conducted with a UV–Vis spectrophotometer revealed high photo sensing and UV shielding characteristics with an energy bandgap of about 3.0 eV, demonstrating widespread applications of these semiconducting PNC materials in emerging optoelectronic device technologies. The broadband dielectric spectroscopic (BDS) characterization over the 20 Hz–1 GHz range explained harmonic field frequency and nanofiller concentration tunable dielectric permittivity (about 3 to 13) with low losses and multiple relaxation processes, predominantly ruled by microstructural interfaces and interactions developed in these ternary hybrid complex materials. The meaningful broadband dielectric characteristics of P(VDF-HFP)/PEO/ZnO materials demonstrated that they could be used as innovative nanodielectrics for energy storage purposes in capacitive devices, and flexible dielectric substrate and insulators for the fabrication of frequency-adjustable discrete and integrated microelectronic devices.

Porous polymer bilayer with near-ideal solar reflectance and longwave infrared emittance

Abstract This study explores the optical design of a daytime radiative cooler with near-ideal solar reflectance and longwave infrared (LWIR) emittance through materials selection and nanostructuring. Focusing on polymers as a materials platform, we introduce a bilayer architecture, comprising a porous poly(vinylidene fluoride-co-hexafluoropropene) (P(VdF-HFP)) topcoat that serves as a low-index LWIR emissive effective medium, over a nanofibrous, solar scattering polytetrafluoroethene underlayer. This novel configuration yields a superwhite coating with a near-ideal solar reflectance of >0.99, and a blackbody-like near-normal and hemispherical LWIR emittances of ∼0.98 and ∼0.96 respectively. Under humid and partially cloudy sky conditions unfavorable for radiative heat loss, these values enable the bilayer radiative cooler to achieve a sub-ambient of 2.3 °C. Given that the porous polymer bilayer uses scalable fabrication processes and commercially available materials, it holds significant promise for device-scale, as well as building thermoregulation applications.

Ultra-high output triboelectric nanogenerator based on synergies of material modification and charge pumping

On the road to large-scale industrialization of triboelectric nanogenerators (TENGs), higher output is the constant quest. Here, inspired by the ubiquitous synergies in nature, an ultra-high-output TENG is proposed based on the synergistic effect of internal modification of materials along with the external integration of a charge pumping module. The carefully chosen poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) film possesses strong polarization and high permittivity, which leads to excellent triboelectric properties, and can be further enhanced by doping BaTiO3 (BTO) nanoparticles. Meanwhile, the elaborately designed and optimized charge pumping module endows it with the ability to pump affluent charges. As a consequence, a TENG based on 8 µm P(VDF-HFP)/BTO 1 wt% composite film can achieve an ultra-high total transfer charge density (TTCD) of 3.5 mC/m2 under optimal charge pumping conditions. Compared to the output of the P(VDF-HFP)/BTO-based TENG (0.1 mC/m2) and the output of the P(VDF-HFP)-based TENG under charge pumping (2.6 mC/m2), the output of the P(VDF-HFP)/BTO-based TENG under charge pumping is greater than the sum of the above two devices, which indicates that the proposed synergistic effect for designing an ultra-high-output TENG is remarkable and successful. Moreover, a novel charge transfer pattern based on synergistic effect is proposed, expounding the role inherent modifications of P(VDF-HFP) and external integration of charge pumping modules play. This work presents a concept that is at the forefront of contemporary designs for ultra-high output TENGs, providing insight into the preparation of high-performance TENGs in a state-of-the-art manner.

Synergistic effect of polymer blend compositions on the structural, thermal, optical, and broadband dielectric properties of P(VDF-HFP)/PEO/ZnO polymer nanocomposites

Polymer nanocomposites (PNCs) composed of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP))/ poly(ethylene oxide) (PEO) blend host matrix of varying compositions i.e., xP(VDF-HFP)/(100–x)PEO with x values 20, 50, and 80 wt%, and zinc oxide (ZnO) as nanofiller (2 wt%) are prepared by state-of-the-art homogenized solution cast method. The SEM micro-images of these PNC films revealed that the polymer blend compositions considerably affect the polymers miscibility, spherulitic morphologies, and crystalline phases. FTIR spectra demonstrated that the P(VDF-HFP) and PEO chain interactions in these PNCs change significantly with the polymer blend compositions. The DSC results revealed a decrease in PEO crystallite temperature and degree of crystallinity with the increase of P(VDF-HFP) amount in the blend matrix of these PNC materials. Analysis of UV-Vis spectra categorized these PNCs of wide band gap (∼ 3.1 eV) semiconductive optical materials. Broadband frequency range (20 Hz–1 GHz) dielectric dispersion demonstrated that 50P(VDF-HFP)/50PEO-2 wt% ZnO composition based nanodielectric film has a relatively high dielectric constant, whereas the chain segmental and dipolar reorientation relaxation processes are strongly polymer blend composition dependent for these PNC materials. The experimental results are discussed in detail concerning the multifunctionality of these PNCs as promising candidates for innovation in flexible optoelectronic and nanodielectric-based microelectronic devices.

Effect of fluorinated polymer matrix type in the performance of solid polymer electrolytes based on ionic liquids for solid-state lithium-ion batteries

Solid polymer electrolytes (SPEs) have been produced using an ionic liquid (IL) (1-Methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide – [PMPyrr][TFSI]) embedded in different fluorinated polymer matrices, including poly(vinylidene-fluoride) – PVDF, poly(vinylidene fluoride-co-hexafluoropropylene) – P(VDF-HFP), poly(vinylidene fluoride-co-trifluoroethylene) – P(VDF-TrFE) and poly(vinylidene fluoride-co-trifluoroethylene-chlorofluoroethylene) – P(VDF-TrFE-CFE), in order to evaluate the effect of the polymer chain polarity, degree of crystallinity and dielectric constant on the electrochemical properties and battery performance. It is shown that the use of the different polymers for SPE development does not have significant influence on the morphology, and thermal properties of the samples. The degree of crystallinity is significantly reduced for the P(VDF-TrFE-CFE) sample. The mechanical characteristics (Young modulus and yield strength and strain) are also associated with the crystallinity degree, being reduced for lower crystallinities. Regarding the electrochemical parameters, the samples present considered high ionic conductivity, with a maximum room temperature value of 6.2 × 10−5 S cm−1 for the P(VDF-HFP) sample. The lithium transference number for all samples show their suitability for application in lithium-ion batteries with an outstanding value of 0.71 for the P(VDF-TrFE-CFE) sample associated with the higher dielectric constant and lower degree of crystallinity of this polymer. Battery cycling tests show a maximum initial discharge capacity of 146 mAh/g for the P(VDF-TrFE) sample at room temperature and C/10 rate. Furthermore, the P(VDF-TrFE-CFE) sample presents an excellent ability to cycle at high discharge rates, achieving 91 mAh/g at 1C rate, an maintaining a high stability after 60 cycles at room temperature, showing excellent potential for application in lithium-ion batteries due to its low crystallinity and high dielectric constant. This work proves the suitability of fluorinated polymer based SPE with embedded ionic liquids for the next generation of solid-state batteries and provides a valuable insight on the role of the polymer dielectric constant and degree of crystallinity on battery performance.

Improved energy density and efficiency of polymer nanocomposites by filling ultralow amounts of 2D Ni(OH)2 nanosheets and building sandwich structure

Currently, the application of polymer dielectric capacitors is largely limited by their low energy storage density. Herein, novel sandwich-structured composite films with simultaneously enhanced energy storage density and efficiency are fabricated, which combine outer layers of inorganic nanosheets Ni(OH)2/poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) with high permittivity and intermediate layer of polycarbonate (PC) with high breakdown strength. The trilayer film with only 1 vol% Ni(OH)2 exhibits an excellent energy storage density of 7.322 J/cm3 accompanied with a high efficiency of 72.1 % at 605 kV/mm, which are 120 % and 113 % of pure P(VDF-HFP). Furthermore, hindrance effect of micro-interfaces and macroscopical-interfaces on electrical trees is well revealed through finite element simulation. These excellent characteristics of composite films suggest that this design strategy is effective to realize concurrent high energy density and efficiency.

Performance enhancement of self-charging system by combining triboelectric nanogenerators and dielectric capacitors

As an emerging platform technology, triboelectric nanogenerator (TENG) provides an effective strategy for the realization and widespread deployment of self-powered wireless sensor nodes. However, TENG still faces challenges that necessitate continuous optimization in terms of device structure and output performance. Here, we propose a novel approach to fabricate an all-in-one self-charging system (A-SCS) by integrating a TENG and a dielectric capacitor made from poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) membrane using the configuration of shared electrodes. The integration capitalizes on the unique characteristics of each component, leading to an enhanced output performance. A 5.5 cm × 5.5 cm sized A-SCS is capable of generating voltages up to 2800 V, with each cycle storing an impressive energy of approximately 3 μJ, which can achieve self-triggered high voltage pulse output through the utilization of discharge tubes. Furthermore, even when miniaturized to a size of 1 cm × 1 cm, the A-SCS exhibits excellent output performance, with a maximum voltage output of 271 V, which is of significant importance for the integration and miniaturization of the A-SCSs. This work not only provides a feasible strategy to develop a new type of high-performance A-SCS, but also presents an excellent application prospect for miniaturized TENGs capable of generating high-voltage pulses.

Fabrication of mesoporous SiO2/P(VDF-HFP) composite membrane for high-performance lithium-ion batteries

The aim of this work is to improve the characteristics of lithium-ion batteries (LIBs) by designing and applying advanced quasi-solid electrolytes. Mesoporous silica nanorods (m-SiO2) with a high specific surface area (537.8 m2 g−1) were prepared via a sol–gel method, then compounded with poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and Li-salt (in organic solvent) to prepare composite gel electrolyte (m-SiO2/P(VDF-HFP)-GE) membrane. It exhibits strong thermal stability (∼353 °C), wide electrochemical stability window (5.3 V), excellent lithium-ion transfer number (tLi+ = 0.71) and high ionic conductivity (σ = 1.6 × 10−3 S cm−1). Meanwhile, when the m-SiO2/P(VDF-HFP)-GE membrane was assembled with LiFePO4 and Li, a long-cycling stable LIB with high-capacity (137 mA h g−1 at 0.3C) was obtained.

Efficient single-crystal 4-N,N-dimethylamino-4-N-methyl-stilbazolium tosylate (DAST) on the optical, piezoelectric coefficient and structure of P(VDF-HFP) copolymer for energy conversion systems

Poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) doped with 4-N,N-dimethylamino-4-N-methyl-stilbazolium tosylate (DAST) composites with various concentrations of DAST dye is prepared using the casting method. The crystal structure and optical properties of the pure and P(VDF-HFP)/DAST composites with various contents of DAST dye are investigated using various techniques such as UV–Vis spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and polarized optical microscopy (POM). The analysis of XRD data and FTIR spectra revealed that the β-fraction has been improved in the composite samples with increasing the content of DAST dye. Analysis of UV spectra displayed that the optical band gap of P(VDF-HFP) pure copolymer is 5.41 eV and has been reduced to be 3.75 eV for P(VDF-HFP)/10 wt% DAST that will be suitable for efficient systems of energy conversion and multijunction-based layer solar cells. Also, it is found that the nonlinear and linear optical parameters of the composite samples are DAST dye-dependent. Thermally stimulated depolarization current (TSDC) technique has been applied to investigate the dipolar and space charge relaxations of the composites. Moreover, it is observed that the pyroelectricity and piezoelectricity are enhanced with increasing the content of DAST dye. The highest content of the DAST dye showed maximum values of the pyroelectric and the piezoelectric coefficients of ~ 4 × 10–5 C/m2 K and ~ 34 pC/N at stress of 6.27 × 105 Pa, respectively. Our results of the polymer/dye composites give an opportunity of a promising material for flexible piezoelectricity devices used in many potential applications and energy harvesting systems.

Flexible coated textile with remarkable passive daytime radiative cooling, UV resistance and hydrophobicity performance

Flexible Passive Daytime Radiative Cooling (PDRC) textiles have great potential for applications in personal thermal management, device cooling, and energy-efficient buildings. It is still a tremendous challenge, however, to simultaneously realize ultra-high solar reflectance and infrared emittance for flexible PDRC textiles. Here, a Poly (vinylidene fluoride-co-hexafluoropropene) (P(VDF-HFP)) coating with uniformly dispersed aluminum oxide (Al2O3) micron particles and nanoporous structure was designed and employed for the fabrication of flexible PDRC textiles. The composite porous coating enabled flexible textiles to exhibit 0.95 solar reflectance and 0.98 atmospheric window emittance with only 150 μm of thickness. The flexible PDRC textile was used for outdoor radiative cooling demonstrating as a maximum cooling effect of 12.5 °C during the daytime and 5 °C at night. The roughened composite porous structure imparted favorable hydrophobicity and UV resistance to the coating, highlighting the potential of this flexible coated textile as a durable outdoor application. This article has blazed a new trail for simplified and large-scale preparation of highly efficient flexible PDRC textiles.

Surface functionalized electrolyte-gated perovskite transistors with enhanced performance via insulating polymer additive

Perovskite–polymer microstructure engineering enables outstanding performance and improved stability in perovskite-based electronic devices. Here, we report perovskite/insulating polymer composite as engineered semiconductors for the simultaneous enhancement of the carrier mobility and environmental stability of electrolyte-gated field-effect transistors (FETs). To this end, we employed conventional poly(methyl methacrylate) (PMMA) and fluorinated poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) insulating polymers. The structural properties of the fabricated perovskite–polymer semiconductors were tuned by controlling the amount of insulating polymer in the perovskite–polymer composites. The optimized methylammonium lead iodide (MAPbI3) perovskite–PMMA-based FETs with a poly(3-hexylthiophene-2,5-diyl) (P3HT) surface passivation layer exhibited a highly-stable operation with a hole mobility of approximately 20 cm2 V−1 s−1 at ≤ 1.5 V and current on/off ratio of ∼103, which exceeds that of the MAPbI3-P(VDF-HFP)-based FETs under highly humid conditions (relative humidity ≈ 60–70%). This exceptional performance of our devices was attributed to the improved injection properties, increased grain size, and passivation of grain boundariesin the transistor channel coupled with the hydrophobic nature, and resistance of the insulating polymers to humidity. This study provide insights into achieving high-performance and environmentally stable perovskite transistor devices through combined bulk and surface passivation.

Highly conductive ceramic-in-polymer composite electrolyte enabling superior electrochemical performance for all-solid-state lithium batteries

In the present work, poly (vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)] and various amounts of NASICON-type LiZr1.5Sn0.5(PO4)3 (LZSP) as the active filler were used to fabricate composite solid electrolytes (CSEs) by solution-casting method and their structural and electrochemical behaviour were studied. The X-ray diffraction (XRD) data showed the compatibility of the rhombohedral LZSP with P(VDF-HFP). A uniform distribution of ceramic particles in the polymer was observed from scanning electron microscopy (SEM) images and energy X-ray dispersive maps. The addition of 15% wt. ceramic filler to the polymer matrix enhanced the room temperature ionic conductivity (σ ∼ 2.87 × 10−5 S/cm), lithium-ion transference number (tLi+ ∼ 0.55), and electrochemical stability window (∼4.87 V). The reversibility and endurance of lithium-ion conduction across the composite electrolyte at various current densities were confirmed through galvanostatic charge-discharge measurements on a symmetric lithium cell for more than 500 h. A full cell fabricated using a commercial grade LiMn2O4 cathode and the optimized CSE electrolyte showed excellent rate performance at room temperature. The cell delivered a discharge capacity of 105 mAh/g with a nominal voltage of 4.0 V and retained 93% of its initial capacity after 100 cycles at a current density of 0.1 mA/cm2.

SiO2 nanofiber reinforced P(VdF-HFP) based microporous polymer electrolytes for advanced energy storage applications

The application of ceramic nanofiller-dispersed microporous polymer gel electrolytes (MPGEs) in energy storage devices has been a subject of utmost research importance for a long time. However, a clear understanding of ion transport properties in this type of electrolyte is not yet achieved. The present article includes a detailed investigation of the uptake kinetics and ion transport mechanism in poly(vinylidene fluoride-co-hexafluoropropylene) [P(VdF-HFP)] based MPGEs reinforced with silica (SiO2) nanofibers. Very high ionic conductivity of 9.21 × 10−3 Scm−1 at ambient temperature has been achieved at a relatively low uptake ratio of 212 %, maintaining the dimensional integrity of the films when nanofiber content in P(VdF-HFP) is 2.5 wt%. This result ascertains the role of nanofibers in promoting ion transport in MPGEs, as revealed by XRD, FTIR, XPS, and simulative computational studies. The diffusive behavior of the MPGEs has been analyzed for both the liquid and the gel phases of the porous polymer membranes. The maximum diffusion coefficients for gel and liquid phases are 2.83 × 10−6 cm2s−1 and 2.36 × 10−12 cm2s−1, respectively, when the weight ratio of nanofiber is 2.5 %, confirming that the gel phase is the dominant conducting phase in MPGEs. The nanofiber-reinforced MPGEs show the highest electrochemical potential window of 4.6 V and excellent interfacial stability at 2.5 wt% of nanofiber concentrations. Nanofiber loaded MPGE also exhibits extreme non-flammability, which can be exposed to the flame for longer without burning. Being highly conductive with outstanding electrochemical, interfacial and flame retardant properties, the synthesized MPGEs could be a suitable candidate for next-generation energy-storing devices.

Influence of the Inclusion of Propylene Carbonate Electrolyte Solvent on the Microstructure and Thermal and Mechanical Stability of Poly(l-lactic acid) and Poly(vinylidene fluoride-co-hexafluoropropylene) Battery Separator Membranes.

The influence of the inclusion of the organic solvent propylene carbonate (PC) in microporous membranes based on poly(l-lactic acid) (PLLA) and poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) has been studied based on its relevance for the application of those separator membranes in lithium-ion batteries. The membranes have been produced through solvent casting and characterized with respect to the swelling ratio originated by the uptake of the organic solvent. The organic solvent uptake affects the porous microstructure and crystalline phase of both membrane types. The organic solvent uptake amount affects the crystal size of the membranes as a consequence of the interaction between the solvent and the polymer, since the presence of the solvent modifies the melting process of the polymer crystals due to a freezing temperature depression effect. It is also shown that the organic solvent partially penetrates into the amorphous phase of the polymer, leading to a mechanical plasticizing effect. Thus, the interaction between the organic solvent and the porous membrane is essential to properly tailor membrane properties, which in turn will affect lithium-ion battery performance.

A gradient “Ceramic-in-Ionogel” electrolyte with tidal ion flow for ultra-stable lithium metal batteries

Composite solid-state electrolytes are considered as key components for safe and high-energy-density lithium metal batteries, given their superior mechanical properties and ion conductive kinetics. However, it still remains a challenge to simultaneously guarantee high ionic conductivity and excellent interfacial compatibility. Herein, a gradient “Ceramic-in-Ionogel” electrolyte with tidal ion flow is proposed for decoupling ionic conductivity and interfacial property. It is composed of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP))/EMIMTFSI/Al2O3 (30 wt. %) layer (Ionogel-dual30) toward cathode and P(VDF-HFP)/EMIMTFSI/Al2O3 (50 wt. %) layer (Ionogel-dual50) to Li-metal anode. Ionogel-dual50 can provide a relatively large number of Al2O3 particles for the formation of AlF3 and Li3AlF6 after being offered electrons at lithium-metal anode and carbon-fluorine bond cleavage in TFSI-, resulting in rapid Li+ transfer and insulated electron transport at interface. Both simulation and experimental characterization suggest that the tidal-flow-like ion transport pathway can offer [Li+-NMP]-P(VDF-HFP) dominant pathway in Ionogel-dual30 and [Li(TFSI)x]+-Al2O3 interface dominant pathway in Ionogel-dual50, achieving a high ionic conductivity of 0.25 mS cm−1. Benefiting from these unique merits, the cycling performance of symmetric Li batteries was greatly improved with a lifetime of over 1000 h at 0.1 mA h cm−2. The effect of this gradient ionogel electrolyte could be well demonstrated in various full cells, evidenced by substantially enhanced cyclability under large current density (2 C), wide voltage range (3–4.5 V) and extreme conditions. This novel “Ceramic-in-Ionogel” electrolyte with tidal ion flow will accelerate the commercialization of high-energy-density lithium metal batteries.