PVDF Research Articles

Molecular dynamics simulation of DNAN/DNB cocrystal PBXs.

The DNAN/DNB eutectic is a high-energy explosive eutectic with superior safety and thermal stability compared to traditional melt-cast explosives. However, the addition of polymer binders can effectively enhance its mechanical properties, allowing for continued production demands without the need for changes to existing factory equipment. In this paper, a model of the DNAN/DNB eutectic explosive was established, and five different types of polymers-cis-1,4-polybutadiene (BR), ethylene-vinyl acetate copolymer (EVA), polyethylene glycol (PEG), fluorinated polymer (F2603), and polyvinylidene fluoride (PVDF)-were added to the (1 0 - 1), (1 0 1), and (0 1 1) cleavage planes, respectively, to form polymer-bonded explosives (PBXs). The stability, trigger bond length, mechanical properties, and detonation performance of the various polymer-bound PBXs were predicted retrogressively. Among the five PBX models, the DNAN/DNB/PEG model exhibited the highest binding energy and the shortest trigger bond length, indicating a significant improvement in stability, compatibility, and sensitivity compared to the original eutectic. Additionally, although the detonation performance of DNAN/DNB decreased after the addition of binders, the final results were still satisfactory. Overall, the DNAN/DNB/PEG model demonstrated excellent comprehensive performance, proving that among the many polymer binders, PEG is the optimal choice for DNAN/DNB. Within the Materials Studio software, molecular dynamics (MD) simulations were employed to predict the properties of the DNAN/DNB eutectic PBX. The MD simulation timestep was set to 1fs, with a cumulative simulation duration of 2ns. A 2ns MD simulation was conducted using the isothermal-isobaric ensemble (NPT). The COMPASS force field was applied, and the temperature was fixed at 295K.

Ultra-flexible and foldable Cu mesh transparent electrodes for the electromagnetic shielding

Ultra-flexible and foldable transparent electrodes have been developed by embedding conductive Cu meshes into a thin polyvinylidene difluoride (PVDF) film. The prepared transparent electrodes exhibit excellent optical and electrical properties (transmittance of 91.5 % at a wavelength of 550 nm, sheet resistance of 0.9 Ω/sq). Particularly, the sheet resistance remains nearly a constant after 1500 bending cycles at a bending radius of 15 μm, demonstrating exceedingly good foldability. Moreover, the Cu meshes possess strong adhesion to the PVDF films, and there is no significant performance degradation after experiencing taping cycles and ultrasonication. To assess the application potentials, transparent shielding of radiofrequency with ＞30 dB attenuation in the range from 10 M to 9 GHz are achieved. Good optical and electrical performance, outstanding foldability, strong adhesion and low-cost material, suggest that the Cu mesh transparent electrode can be applied to the next generation of wearable optoelectronic systems.

Synergistically enhanced dielectric properties and thermal conductivity in percolating flaky copper/poly(vinylidene fluoride) nanocomposites via engineering magnesium oxide as a buffer interlayer

AbstractHigh dielectric constant (ε), thermal conductivity (TC), and breakdown strength (Eb) along with low loss flexible polymeric nanocomposites display multifunctional applications. In this work, to synergistically bolster the TC and Eb while restraining dielectric loss and leakage current in the percolating flaky copper (f‐Cu)/poly(vinylidene fluoride) (PVDF), presenting a giant ε, the core@shell structured f‐Cu@MgO (magnesium oxide) nanosheets were first created via a chemical precipitation method, then incorporated into host PVDF to explore the MgO shell’ impact on the TC and dielectric properties of the resulting nanocomposites. The introduced MgO interlayer strengthens the interfacial interactions and significantly mitigates the interfacial mismatch in both ε and conductivity between the f‐Cu and PVDF, resulting in elevated TC and Eb of the f‐Cu@MgO/PVDF in comparison to pristine f‐Cu/PVDF. Furthermore, the insulating MgO interlayer introduces deep traps and inhibits the long‐distance migration of electrons, leading to remarkably suppressed dielectric loss. More importantly, the TC and dielectric properties of nanocomposites can be optimized by tuning the MgO thickness. The fitting results via the Havriliak‐Negami equation theoretically support the MgO shell's suppression effect on charge migration and reveal the underlying polarization mechanism in the nanocomposites. The developed nanocomposites with currently high ε, Eb and TC but low loss, present promising applications in electrical power systems.

Electrospinning of porous polyvinylidene fluoride microspheres alloyed fibrous membrane with enlarged strain for efficient piezoelectric energy harvesting

AbstractPiezoelectric energy harvesters (PEHs) developed from electrospun polyvinylidene fluoride (PVDF) fibers offer flexibility and superior piezoelectric output, making them promising for self‐powered systems and sensors. Nonetheless, the electromechanical conversion efficiency of conventional electrospun PVDF fibers is impeded by their limited pressure‐strain range. Herein, elastic porous PVDF microspheres are introduced in‐situ via electrospinning to craft a piezoelectric membrane with higher compressive strain. The PVDF microspheres are uniformly embedded between the fibers in a sandwich fashion, and their dimension is easily tunable by varying spinning solution's concentration. Moreover, the micropores on the PVDF microspheres created by removing pre‐mixed SiO2 template not only elevates the β crystal content of PVDF to 82.19%, but also improves the compressibility, significantly boosting the piezoelectric output. The microsphere alloyed PVDF PEH delivers a piezoelectric output of 33.0 V and a power density of 8 μW/cm2, over 5.8 times that of conventional electrospun PVDF membrane, and can consistently charge lithium‐ion batteries. Our research unveils a novel strategic path to modify fiber structured PEHs, advancing their applications in self‐powered systems.

Composite Nanoarchitectonics of Electrospun Piezoelectric PVDF/AgNPs for Biomedical Applications, Including Breast Cancer Treatment

This study focused on preparing composite nanomats by incorporating silver nanoparticles (AgNPs) in polyvinylidene fluoride (PVDF) nanofibers through the electrospinning process. A short review of piezoelectric PVDF-related research is presented. PVDF is known for its biocompatibility and piezoelectric properties. Since electrical signals in biological tissues have been shown to be relevant for therapeutic applications, the influence of the addition of AgNPs to PVDF on its piezoelectricity is studied, due to the ability of AgNPs to increase the piezoelectric signal, along with providing antibacterial properties. The prepared samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. In addition, the biological activity of composites was examined using a cytotoxicity assay and an assessment of the antibacterial activity. The obtained results show that the incorporation of AgNPs into PVDF nanofibers further enhances the piezoelectricity (crystalline β-phase fraction), already improved by the electrospinning process, compared to solution-casted samples, but only with a AgNPs/PVDF concentration of up to 0.3%; a further increase in the nanoparticles led to a β-phase reduction. The cytotoxicity assay showed a promising effect of PVDF/AgNPs nanofibers on the MDA-MB-231 breast cancer cell line, following the non-toxicity displayed in regard to the healthy MRC-5 cell line. The antibacterial effect of PVDF/AgNPs nanofibers showed promising antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus, as a result of the Ag content. The anticancer activity, combined with the electrical properties of nanofibers, presents new possibilities for smart, multifunctional materials for cancer treatment development.

Electromechanical coupling in polyetheretherketone through flexoelectricity

The electrical signals generated by an electromechanical coupling mechanism in biomaterials have significant potential applications in the field of biomedical engineering. For example, the piezoelectric- or flexoelectric-induced electrical signals in bone biomaterials play an important role in facilitating self-repair, remodeling, and reshaping processes. Polyetheretherketone (PEEK) has been found to possess excellent mechanical properties and biocompatibility with bone, making it an outstanding choice as an implantable polymer material. It is particularly important to investigate the electromechanical response performance of PEEK materials. In this study, we experimentally examine the flexoelectricity of PEEK and evaluate its effective out-of-plane direct and converse flexoelectric coefficients. Using the piezoresponse force microscopy module of atomic force microscopy, we observe a clear converse flexoelectric effect in a PEEK disk-shaped sample. The effective out-of-plane converse flexoelectric coefficient of the PEEK disk-shaped sample is about μ3333eff=0.21 ± 0.02 nN/V. The effective out-of-plane direct flexoelectric coefficient, determined through the bending experiment of a PEEK cantilever, is f3113eff = 17.61 nC/m, which is larger than that of polyvinylidene fluoride and is nearly two orders of magnitude superior over other biomaterials such as bone and hydroxyapatite. This indicates that PEEK materials have even greater potential for development and research in biomedical engineering applications such as intervertebral fusion, bone joint replacement, bone rehabilitation and regeneration, etc.

Interfacially crystallized Enzyme@MOFs biocatalytic membranes for highly efficient synthesis of D-amino acids via continuously recirculating stereoinversion

D-Amino acids (D-AAs) constitute essential building blocks found in many pharmaceuticals and fine chemicals. We herein presented the coating of polyvinylidene fluoride (PVDF) hollow fiber membrane with L-amino acid oxidase (LAAO) embedded zeolitic imidazolate framework-8 (ZIF-8) layer by a single-step interfacial biomineralization strategy for efficient synthesis of D-AAs. The ZIF-8 skeleton and PVDF membrane structure not only guaranteed free enzyme activity and stability, but also reinforced the applicability of this bioreactor for continuous enzymatic reactions. By placing the prepared biocatalytic membrane in the constructed circulation device, only the L-AAs can be specifically oxidized. The D-AAs are accumulated and synthesized after multiple rounds of continuously recirculating stereoinversion. Impressively, using tryptophan (Trp) as the model molecule, the thus-designed bioreactor exhibited an excellent conversion rate (92.10%) and ee% (99.41%) of D-Trp with a shorter time under constant flow conditions. This study provides an unprecedented protocol for highly efficient synthesis of D-AAs, and immensely advances the promising application field of membrane bioreactors.

Synergistic Molecular Alignment and Dipole Polarization in Stretched Nafion/Poly(vinylidene fluoride) Blend Membranes for High Proton Conduction in PEMFCs.

The nanostructure of Nafion and poly(vinylidene fluoride) (PVDF) blend membranes is successfully aligned through a mechanical uniaxial stretching method. The phase-separated morphology of Nafion molecules distinctly forms hydrophilic proton channels with increased connectivity, resulting in enhanced proton conductivity. Additionally, the crystalline phase of PVDF molecules undergoes a successful transformation from the α- to β-phase during membrane stretching, demonstrating an alignment of fluorine and hydrogen atoms with a TTTT(trans) structure. The aligned nanostructure of the blend film, combined with the dipole polarization of the β-phase PVDF, synergistically enhances the proton conduction through the membrane for operating proton-exchange membrane fuel cells (PEMFCs). The controlled structures of the blend membranes are thoroughly investigated using atomic force microscopy and small-angle X-ray scattering. Furthermore, the improved in-plane proton conductivity facilitates increased proton conduction at the interface between the membrane and catalyst layer in the membrane-electrode assembly, ultimately enhancing the power generation of PEMFCs.

Enhanced Dielectric and Energy Storage Capacity of Polymer Dielectrics via Reverse Infiltration of Poly(vinylidene fluoride)–Boron Nitride into a Three-Dimensional Barium Titanate Network

Enhanced Dielectric and Energy Storage Capacity of Polymer Dielectrics via Reverse Infiltration of Poly(vinylidene fluoride)–Boron Nitride into a Three-Dimensional Barium Titanate Network

Synergistic effect of Ni(OH)2 and MXene nanosheets in 3D framework on the improvement of Dielectric, Energy storage, Mechanical and Thermal characteristics of Polyvinylidene fluoride(PVDF). polymeric composites

This work introduces a novel method for incorporating meticulously designed nanohybrids to improve the dielectric characteristics of polymer composites. Conventional ceramic fillers have problems with dispersion even if they are good at increasing permittivity. Here, we overcome this constraint by creating nanohybrids made of MXene, polyvinylidene fluoride (PVDF), and single-layered and three-dimensional Ni(OH)2. An essential coupling agent, polyethyleneimine (PEI), fosters a robust electrostatic connection between Ni(OH)2 and superior adhesion with MXene. Using only 9.5 weight percent filler loading, we are able to achieve a low loss tangent (tan δ=0.4) at 1kHz with a considerable permittivity improvement (ε=1000) thanks to this creative design. The nanohybrid structure's ability to promote longer interfacial contact is crucial to this enhancement. Moreover, the integrated Ni(OH)2 layer functions as a semiconductor, obstructing the passage of current through the MXene flakes and lowering conductivity overall. At a low Ni(OH)2/MXene loading of 1.5wt%, our three-phase composites also show higher dielectric strength (248.68MV/m). Specifically, the synergistic coupling of MXene with Ni(OH)2 provides notable increases in mechanical and thermal properties. The tensile strength and Young's modulus of these films are much higher than those of virgin PVDF and Ni(OH)2-modified composites.

Dual function sMoS2-cellulose/PVDF-based membrane for energy generation and pollutant removal

Fostering the creation of clean energy technologies that eliminate gas emissions and positively impact the environment is vital for confronting the dual challenges of escalating energy demands and environmental contaminants. Membrane-based technologies have emerged as effective strategies for harvesting clean energy and practically purifying water from contaminated wastewater. Here, we show that polyvinylidene difluoride (PVDF) with functionalized molybdenum disulfide (sMoS2) and nanocellulose (NC) is an attractive membrane for single-chamber air cathode microbial fuel cells (MFCs). Compared with conventional proton exchange membranes, our membrane boosts power generation up to 48.5 mW m−2 and efficiently catalyzes sonocatalytic dye degradation with 96 % efficiency when treating wastewater. This performance is due to a relatively high hydrophilicity, ion exchange capacity (0.84 meq. g−1), and proton conductivity (1.03 × 10−2 S cm−1), combined with reduced oxygen permeability (27 × 1012 cm·s−1) compared with conventional membranes. The synergy effect of the PVDF matrix and sMoS2 + NC promotes proton transfer, enhancing electricity generation and pollutant degradation. The membrane shows promising stability and mechanical properties 42.04 MPa, offering a viable membrane for improved energy recovery from wastewater treatment.

A green zwitterionic bi-continuous membranes prepared by dual-bath procedure for mitigating biofouling during bacterial removal from water

This work explores the possibility of forming green microfiltration antifouling membranes based on polyvinylidene fluoride (PVDF) and a zwitterionic copolymer derivative of sulfobetaine methacrylate (SBMA), utilizing gamma- valerolactone (GVL) as the solvent and a mixture of ethanol and water as non-solvents. Efforts were initially focused on adjusting the immersion time of the matrix polymer in alcohol alone to obtain a porous structure, and 15 s were sufficient to achieve a symmetric, open porous morphology. Next, the polymer/copolymer/solvent blend was characterized. While it did not show the characteristics of a fully miscible system, DLS and visual observations revealed the obtaining of a homogeneous (relatively narrow particle size) and transparent to translucent system. Thus, membranes could be cast, and were shown to be stable. The addition of the copolymer maintained the physical characteristics of microfiltration membranes, but an FT-IR analysis revealed its effect on the dominant crystalline polymorph (switching from β to α). The membrane wettability was enhanced in an important extent with a dynamic water contact angle (WCA) gradually falling to < 40° (while the virgin membrane’s WCA remained about 138° all test long), and a hydration capacity reaching about 530 mg/cm3 against < 10 mg/cm3. It reflected on the antifouling abilities of the membranes as tested using bovine serum albumin, fibrinogen, Escherichia coli, and Stenotrophomonas maltophilia, with relative decreases in adsorption during static tests measured to be 95%, 70%, 91% and 98%, respectively. Finally, compared to the virgin membrane, the modified membrane featured improved flux recovery (32% vs. 11%), significantly higher rejection (98.9% vs. 89.1%) and lower irreversible fouling tendency (68% vs. 89%) during cyclic water/bacterial solution filtration in dead-end mode, making it potentially suitable for addressing bacterial pollution in wastewater.

Spray coating of 2D materials in the production of antifouling membranes for membrane distillation

Membrane surface coatings with 2D materials have been shown to exhibit antifouling properties for water-treatment applications; however, synthesis methods currently based on vacuum filtration are not easily scalable. This study describes a scalable method for coating membranes with a range of 2D materials including graphene oxide (GO), hexagonal boron nitride (hBN), molybdenum disulphide (MoS2) and tungsten disulphide (WS2). Isopropyl alcohol solutions containing each class of the 2D flakes were spray-coated onto commercial polyvinylidene fluoride (PVDF) using a pyrolyser. The nanomaterials were secured with polydopamine (PDA) as a crosslinker in a method that could easily be integrated into a scalable roll-to-roll process. Changes in morphology, surface roughness, hydrophobicity, mechanical durability and chemical composition were evaluated using scanning electron microscopy, atomic force microscopy, contact angle, tensile strength measurements and Fourier-transform infrared spectroscopy. The 2D nanomaterials-coated membranes were tested in membrane distillation (MD) experiments over 72 hours and compared to pristine PVDF and PDA/PVDF membranes. Salt rejection and MD performance stability were evaluated using feedwaters with high concentrations of humic acid (150 ppm) and paraffin oil (200 ppm) simulating simple organic wastewater from oil and gas extraction. The flux decline ratio was measured in terms of percentage permeate loss per hour (%/h), to allow for future comparisons with studies with different experimental times. The pristine PVDF membrane failed after 10 hours by pore-wetting due to fouling while the PDA/PVDF membrane had the largest flux decline ratio (0.3 %/h). The membranes coated with GO and hBN had flux decline ratios orders of magnitude lower (0.0021 ± 0.005 and 0.028 ± 0.01 %/h, respectively). All membranes had a high salt rejection (>99.9 %). The GO-coated membrane was the only membrane type that was able to treat both surfactant-containing and foulant-containing feedwaters. The improved performance is attributed to the decrease in both surface roughness and hydrophobicity, which reduces the adsorption of foulants onto the membrane surface. This work shows a facile, scalable method to overcome fouling limitations in MD.

Polyamidoamine dendrimer-modified polyvinylidene fluoride microporous membranes for protein separation

The separation efficiency of pressure-driven filtration membranes is primarily dictated by the membrane pore size. Membranes with larger pores typically demonstrate high flux but low or zero rejection when it comes to separating small molecules. In protein separation, ultrafiltration (UF) membranes with pore sizes smaller than the molecular dimensions of target proteins are commonly used for size rejection. Taking inspiration from the separation mechanism of nanofiltration (NF) membranes, we hypothesize that introducing charged groups into membranes of appropriate pore sizes could significantly enhance the electrical interaction between membrane charges and protein charges. This enhancement, occurring at the nanoscale distance when protein molecules approach or pass through charged nanoscale membrane channels, may enable the rejection of proteins substantially smaller than the pore size. Using membranes with relatively large pore sizes could lead to an increase in flux. To test this hypothesis, we conducted experiments involving the modification of polyvinylidene fluoride (PVDF) membranes with suitable pore sizes, using polyamidoamine (PAMAM) dendrimers to introduce negative charges to the membranes. The performance of the PVDF membranes and the modified membranes were investigated in the separation of whey proteins. To evaluate the contribution of steric and electrical hindrance to the solute separation, filtration experiments were performed using polyethylene oxide (PEO) and polyacrylic acid (PAA). The membranes were characterized using techniques such as Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM). The results indicate that the modification enhances the rejection efficiency of whey proteins. The whey protein rejection and permeate flux for PVDF membranes were 58.9% and 15.3 LMH, respectively. Following alkaline treatment or PAMAM-G3.5 dendrimer modification, the whey protein rejection increased to 97.3% and 98.8%, respectively. However, alkaline treatment and PAMAM-G3.5 dendrimer modification resulted in a reduction of permeate flux to 5.6 LMH and 2.3 LMH, respectively. This suggests that increasing membrane charge effectively enhances the separation ability of filtration membranes in charged macromolecule separation.

A biodegradable ZnFe2O4/PLLA electrospun fibers based longitudinal mode piezoelectric membrane for health monitoring

Recently, multifunctional sensors based on piezoelectric active film fabricated with environmental friendly materials is a nascent field which can address the growing concern of electronic waste. Nevertheless, frequently utilized poly(vinylidene fluoride) (PVDF) and poly(L-lactic acid) (PLLA) encounter challenges of limited biocompatibility and weak piezoelectricity with low shear piezoelectric coefficient (d14), respectively. Accordingly, a biodegradable piezoelectric sensor comprising of PLLA nanofiber blended with ZnFe2O4 nanoparticles was developed in this work. The ZnFe2O4 nanoparticles served as heterogeneous nucleation center leading to improved piezoelectric coefficient and output than pure PLLA due to more consistent orientation of CO dipoles. The ZnFe2O4/PLLA film exhibited significant performance improvement featured with 1.7-fold higher longitudinal piezoelectric coefficient (d33 ∼ 6.5 ± 0.3 pm/V), nearly 250 % boosting on the output voltage. The ZnFe2O4/PLLA piezoelectric sensor induced high sensitivity (2–10 N:0.55 V/N; 10–32 N:0.29 V/N) and excellent mechanical stability for 27,000 cycles. The results of the soil burial experiment demonstrate that the film can degrade by over 75 % within 90 days, confirming its excellent biodegradability. Moreover, the ZnFe2O4/PLLA nanofibers based piezoelectric sensor could serve as effective detection evidenced by different output signals of head motion, pulse and artery beating demonstrating its feasible application for health monitoring. Considering the characteristics of straightforward fabrication and readily accessible sustainable materials, the ZnFe2O4/PLLA sensor provides an appealing eco-friendly solution for self-powered flexible personal devices disregarding the need to dispose of electronic waste.

Ultrahigh energy harvesting ability of PVDF incorporated with 2D halide perovskite nanosheets via interface effect

Two-dimensional (2D) perovskites have recently emerged as an new family of ferroelectrics and attracted extensive attention for their specific surface interface characteristics benefitting from the unique structure by inserting hydrophobic organic cations into conventional three-dimensional frameworks. In this study, 2D metal–organic perovskite nanosheets, (C4H9NH3)2CsPb2Br7, ((BA)2CsPb2Br7), were successfully synthesized by facile temperature-cooling method and introduced into poly (vinylidene fluoride) (PVDF) polymer fibers to construct flexible piezoelectric energy harvester (PEH). (BA)2CsPb2Br7/PVDF nanofibers reveal a high piezoelectric coefficient (d33) of 63.3 pm/V, which is 2.9 times of the PVDF polymer (21.7 pm/V). Principally, the PVDF composite with 5 wt% (BA)2CsPb2Br7 nanosheet filler assumes an superior electroactive phase amount of about ∼ 93 % profiting from the interfacial interaction between BA+ cations of (BA)2CsPb2Br7 and the dipoles of PVDF. The PEH based on (BA)2CsPb2Br7 nanosheets embedded in PVDF fibers showed a maximum output voltage, 135 V, which is almost 17 times of the PEH based on neat PVDF fibers. Furthermore, the interfacial interaction between (BA)2CsPb2Br7 and PVDF was analyzed by first principle DFT study which reveals electrons migrate and the interfacial polarization between the interface. Simultaneously, (BA)2CsPb2Br7/PVDF composite fibers based PEH reveals exceptional long-term stabilities and durability. More attractively, the exceptional performance of this fabricated PEH evinces a pressure sensitivity of ∼ 7.3 V/N and bio-mechanical harvesting behavior arising from varied human motions, such as beating, pressing, twisting, walking and running. This cost-effective and high performance of (BA)2CsPb2Br7/PVDF based PEH is favorable for the continuation of 2D halide perovskites for further application in new energy and biomechanical filed.

Properties, characterization and biomedical applications of polyvinylidene fluoride (PVDF): a review

AbstractPolyvinylidene fluoride (PVDF) boosted its technological applications because of its piezoelectric and pyroelectric properties, together with mechanical, chemical, and thermal resistance. In this review, we address the PVDF chemical structure and its synthesis procedure, also describing the occurrence of polymorphism (alpha (α), beta (β), gamma (γ), and delta (δ) of this semicrystalline polymer, and the processes involved in phase transformation that govern the adaptability of the PVDF crystalline phases and properties for several industrial uses. It can be used as a component of implants and sutures, as engineering plastic to play a structural role in aggressive environments, acting in the field of process control as a component of transducers and sensors, as well as in the synthesis of separation membranes, fuel cells, and a long list of new applications that include an important role in robotics. The main physicochemical techniques used for PVDF characterization, i.e., differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, that highlight its unique properties, are also discussed, showing the versatility of PVDF for a range of biomedical and pharmaceutical applications.

Impact of Binder Thin-Films on Surface Chemistry of Silicon Anodes in Lithium-Ion Batteries

Abstract The effect of polymer binder on the nature and location of solid-electrolyte interphase (SEI) formation on Si active material was investigated. Thin layers of polymeric binder (polyvinylidene fluoride and sodium carboxymethyl cellulose) were spin-coated onto polished single crystal Si wafers. The samples were cycled against a Li counter/reference electrode under various electrochemical conditions in a coin cell configuration. The electrolyte was 1 M of LiPF6 in 1:1:1 wt % EC:DEC:DMC. After cycling, the samples were extracted from the coin cell under inert conditions and X-ray photoelectron spectroscopy (XPS) was performed. Electron microscopy and atomic force microscopy indicate that the binder films are smooth and continuous across the wafer surface, and no impact on the electrochemical behavior was observed. However, notable differences were detected using XPS, which revealed both difference in SEI composition and location relative to the binder-electrolyte and binder-substrate interfaces. These observations and insights will be useful in cell designs, binder selection, and reliability estimates because the location of SEI formation may influence cyclic performance of electrodes.

Multi-Template-Guided Synthesis of High-Dimensional Molecular Assemblies for Humidity Gradient-Based Power Generators.

Systematically orchestrating fundamental building blocks into intricate high-dimensional molecular assemblies at molecular level is imperative for multifunctionality integration. However, this remains a formidable task in crystal engineering due to the dynamic nature of inorganic building blocks. Herein, we develop a multi-template-guided strategy to control building blocks. The coordination modes of ligands and the spatial hindrance of anionic templates are pivotal in dictating the overall structures. Flexible multi-dentate linkers selectively promote the formation of oligomeric assembly ([TeO3(Mo2O2S2)3O2(OH)(C5O2H7)3]4- {TeMo6}) into tetrahedral cages ([(TeO3)4(Mo2O2S2)12(OH)12(C9H9O4P)6]8- {Te4Mo24} and [(AsO4)4(Mo2O2S2)12(OH)12(C9H9O6)4]12- {As4Mo24}), while steric hindrance from anionic templates further assists in assembling cages into an open quadruply twisted Möbius nanobelt ([(C6H5O3P)8(Mo2O2S2)24(OH)24(C8H10O4)12]16- {P8Mo48}). Among these structures, the hydrophilic-hydrophobic hybrid cage {Te4Mo24} emerges as an exemplary molecular model for proton conduction and serves as a prototype for humidity gradient-based power generators (HGPGs). The Te4Mo24-PVDF-based HGPG (PVDF = Poly(vinylidene fluoride)) exhibits notable stability and power generation, yielding an open-circuit voltage of 0.51 V and a current density of 77.8 nA cm-2 at room temperature and 90% relative humidity (RH). Further insights into the interactions between water molecules and microscale molecules within the generator are achieved through molecular dynamics simulations. This endeavor unveils a universal strategy for synthesizing multifunctional integration molecules.

Multi‐Template‐Guided Synthesis of High‐Dimensional Molecular Assemblies for Humidity Gradient‐Based Power Generators

Systematically orchestrating fundamental building blocks into intricate high‐dimensional molecular assemblies at molecular level is imperative for multifunctionality integration. However, this remains a formidable task in crystal engineering due to the dynamic nature of inorganic building blocks. Herein, we develop a multi‐template‐guided strategy to control building blocks. The coordination modes of ligands and the spatial hindrance of anionic templates are pivotal in dictating the overall structures. Flexible multi‐dentate linkers selectively promote the formation of oligomeric assembly ([TeO3(Mo2O2S2)3O2(OH)(C5O2H7)3]4‐ {TeMo6}) into tetrahedral cages ([(TeO3)4(Mo2O2S2)12(OH)12(C9H9O4P)6]8‐ {Te4Mo24} and [(AsO4)4(Mo2O2S2)12(OH)12(C9H9O6)4]12‐ {As4Mo24}), while steric hindrance from anionic templates further assists in assembling cages into an open quadruply twisted Möbius nanobelt ([(C6H5O3P)8(Mo2O2S2)24(OH)24(C8H10O4)12]16‐ {P8Mo48}). Among these structures, the hydrophilic‐hydrophobic hybrid cage {Te4Mo24} emerges as an exemplary molecular model for proton conduction and serves as a prototype for humidity gradient‐based power generators (HGPGs). The Te4Mo24‐PVDF‐based HGPG (PVDF = Poly(vinylidene fluoride)) exhibits notable stability and power generation, yielding an open‐circuit voltage of 0.51 V and a current density of 77.8 nA cm‐2 at room temperature and 90% relative humidity (RH). Further insights into the interactions between water molecules and microscale molecules within the generator are achieved through molecular dynamics simulations. This endeavor unveils a universal strategy for synthesizing multifunctional integration molecules.