Tannic-Acid-Coated Polypropylene Membrane as a Separator for Lithium-Ion Batteries

Harnessing geometric distortion to stimulate oxygen reduction activity of atomically dispersed Fe catalysts in quasi-solid-state zinc-air batteries

To achieve precise optimization of the geometric structure and control over spatial distribution of single atom active sites, we introduce an in situ polymer layer modification strategy. Through co-deposition of tannic acid (TA) and polyethyleneimine (PEI) on carbon nanotubes (CNTs), the polymer improves the dispersion and prevents the agglomeration of Fe atoms. Consequently, after controlled calcination, the geometrically distorted Fe-N4 single atom active sites are constructed on the surface of the curved carbon support. The optimized distortion reduces the reaction energy barrier, optimizes the adsorption energy of oxygen intermediates, and leading to a remarkable improvement of oxygen reduction reaction (ORR) activity. As the result, the obtained single atom catalyst (SAC) Fe-NC@CNTs exhibits exceptional performance with a large onset potential (Eonset) of 1.03 V and a half-wave potential (E1/2) of 0.91 V in 0.1 M KOH solution, surpassing the previously reported ORR electrocatalysts. Benefitting from these features, Fe-NC@CNTs-based rechargeable aqueous Zn-air battery (A-ZAB) delivers a higher power density of 209.5 mW cm-2 and can sustain stable changing/discharging for over 2000 h and experiences negligible charge-discharge potential gap fluctuation, being the most booming competitor among the reported electrocatalysts. Furthermore, quasi-solid-state Zn-air battery (QSS-ZAB) with Fe-NC@CNTs air cathode exhibits an impressive peak power density of 130.8 mW cm-2, large round-trip efficiency of 82 %, and long cycling life of over 100 h. Our work reveals the relationship of strain-induced geometrical distortion and the structure activity relationship, offering a new way for the rational design of other highly efficient catalytic systems.

Enhancing the Performances of Lithium Batteries through Functionalization of Porous Polyolefin Separators with Cross-Linked Single-Ion Polymer Electrolytes

Lithium-ion batteries (LiBs) require advanced separators to meet the growing demands of high energy density, safety, and durability. However, conventional polyolefin separators often suffer from poor electrolyte wettability and limited ionic conductivity, hindering the overall battery performance. This study presents a scalable approach for the surface functionalization of porous polyolefin separators using single-ion statistical copolymers bearing lithium sulfonate or lithium trifluoromethanesulfonamidosulfonyl groups. These copolymers are deposited via a wet coating process followed by UV cross-linking, achieving durable and uniform functionalization without compromising the separator's porous structure. The functionalized separators exhibit significantly enhanced wettability, electrolyte uptake, and effective ionic conductivity. Electrochemical performance tests of LiBs reveal stable interfacial resistance, improved cycle life, and better rate capabilities owing to the effectiveness of the covalently bonded ionic groups in promoting selective lithium-ion transport. This approach combines simplicity, scalability, and robust chemical stability, offering a promising solution for next-generation LiBs by addressing the key limitations of commercial separators.

Innovative Separator Engineering: Hydrogen Bond-Driven Layer-By-Layer Assembly for Enhanced Stability and Efficiency in Lithium Metal Batteries

Lithium metal batteries (LMBs) face critical challenges due to uncontrolled lithium dendrite growth and inhomogeneous Li+ flux, largely attributed to conventional separators' poor interfacial compatibility. To address this, we propose a hydrogen bond-driven layer-by-layer (LbL) assembly strategy for engineering functional separators using poly(vinyl alcohol) (PVA) and tannic acid (TA). The optimized PP/(TA/PVA)15 separator leverages the synergistic interplay between PVA's hydroxyl groups and TA's carbonyl moieties, forming a robust hydrogen-bonded network that simultaneously enhances lithiophilicity, regulates Li+ flux uniformity, and immobilizes anions. The interfacial design achieves exceptional electrochemical performance: Li//Li symmetric cells maintain stable operation for 800 h at 0.5 mA cm-2/0.5 mAh cm-2, while Li//LiFePO4 half cells retain 73.8% capacity after 1000 cycles at 5C (decay rate: 0.026% per cycle). The separator further exhibits high ionic conductivity (0.94 mS cm-1) and Li+ transference number (0.63), outperforming conventional polyolefin counterparts. By integrating simplicity, scalability, and eco-friendliness, this work pioneers a universal interface chemistry paradigm for next-generation LMBs, offering transformative insights into separator engineering through molecular-level hydrogen-bonding control.

Functionalized Separators Boosting Electrochemical Performances for Lithium Batteries

The growing demands for energy storage systems, electric vehicles, and portable electronics have significantly pushed forward the need for safe and reliable lithium batteries. It is essential to design functional separators with improved mechanical and electrochemical characteristics. This review covers the improved mechanical and electrochemical performances as well as the advancements made in the design of separators utilizing a variety of techniques. In terms of electrolyte wettability and adhesion of the coating materials, we provide an overview of the current status of research on coated separators, in situ modified separators, and grafting modified separators, and elaborate additional performance parameters of interest. The characteristics of inorganics coated separators, organic framework coated separators and inorganic-organic coated separators from different fabrication methods are compared. Future directions regarding new modified materials, manufacturing process, quantitative analysis of adhesion and so on are proposed toward next-generation advanced lithium batteries.

Enhanced filtration membranes with graphene oxide and tannic acid for textile industry wastewater dye removal

A novel modification technique employing a layer-by-layer (LbL) self-assembly method, integrated with a pressure-assisted filtration system, was developed for enhancing a commercial polyethersulfone (PES) microfiltration (MF) membrane. This modification involved the incorporation of tannic acid (TA) in conjunction with graphene oxide (GO) nanosheets. The effectiveness of the LbL method was confirmed through comprehensive characterization analyses, including ATR-FTIR, SEM, water contact angle (WCA), and mean pore size measurements, comparing the modified membrane with the original commercial one. Sixteen variations of PES MF membranes were superficially modified using a three-factorial design, with the deposited amount of TA and GO as key factors. The influence of these factors on the morphology and performance of the membranes was systematically investigated, focusing on parameters such as pure water permeability (PWP), blue corazol (BC) dye removal efficiency, and flux recovery rate (FRR). The membranes produced with the maximum amount of GO (0.1 mg, 0.55 wt%) and TA as the inner and outer layers demonstrated remarkable FRR and significant BC removal, exceeding 80%. Notably, there was no significant difference observed when using either 0.2 (1.11 wt%) or 0.4 mg (2.22 wt%) in the first layer, as indicated by the Tukey mean test. Furthermore, the modified membrane designated as MF/TA0.4GO0.1TA0.4 was evaluated in the filtration of a simulated dye bath wastewater, exhibiting a BC removal efficiency of 49.20% and a salt removal efficiency of 27.74%. In conclusion, the novel PES MF membrane modification proposed in this study effectively enhances the key properties of pressure-driven separation processes.

Tannic acid crosslinked chitosan/gelatin/SiO2 biopolymer film with superhydrophobic, antioxidant and UV resistance properties for prematuring fruit packaging

The environmental pollution caused by plastic films urgently requires the development of non-toxic, biodegradable, and renewable biopolymer films. However, the poor waterproof and UV resistance properties of biopolymer films have limited their application in fruit packaging. In this work, a novel tannic acid cross-linked chitosan/gelatin film with hydrophobic silica coating (CGTS) was prepared. Relying on the adhesion of tannic acid and gelatin to silica, the coating endows CGTS film with excellent superhydrophobic properties. Especially, the contact angle reaches a maximum value 152.6°. Meanwhile, tannic acid enhanced the mechanical strength (about 36.1 %) through the forming of hydrogen bonding and the network structure. The prepared CGTS films showed almost zero transmittance to ultraviolet light and exhibited excellent radical scavenging ability (∼76.5 %, DPPH). Hence, CGTS film is suitable as a novel multifunctional packaging material for the agriculture to protect premature fruits, or the food industry used in environments exposed to ultraviolet radiation and rainwater.

Preparation of a CPVC composite loose nanofiltration membrane based on plant polyphenols for effective dye wastewater treatment

The textile industry's high-salinity wastewater presents a significant difficulty for fractioning salts and dyes. To fractionate the dyes and salts, a high-performance CPVC composite loose nanofiltration membrane (LNM) was fabricated by interfacial polymerization. The organic phase was obtained by crosslinking polyethylenimine (PEI) with tannic acid (TA) and gallic acid (GA) using TMC. The resultant composite LNM performance was enhanced by adjusting the coating parameters, which included TA and GA concentrations as well as coating time. The study examined the effects of the total content of TA/PEI and GA/PEI concentrations on the chemical structure, surface roughness, and microstructure of the selective layer of LNM using SEM, AFM, FTIR, and water contact angle measurements. It also investigated the filtration performance of the membrane's selective layer, including pure water flux, PEG800 rejection rate, and membrane fouling analysis. However, the resultant membrane treated simulated reactive black 5 (RB5) dye wastewater. When the total content of TA/PEI is 4 kg L-1, the permeability of pure water flux is high at 7.5 L per m2 per h per bar when the total content of GA/PEI is 14 kg L-1 and the pure water flux is high at 8.8 L per m2 per h per bar. The overall PEG800 rejection rates were 97-98.98%. The optimal TA : PEI ratios reached a good pure water permeability up to 6.4 L per (m2 per h per bar) with a high rejection rate of 99.69% for a ratio 1/3 to dye, and GA : PEI ratios reached a good water permeability at 5.5 and 6.5 L per (m2 per h per bar) with rejection rates of 99.21% and 98.88% for ratio 1/3 and 3.5/10.5 for simulated RB5 dye, and the NaCl retention rate gradually decreased from 4% to 3%. The resultant LNM demonstrated promising applications in dye and salt fractionation.

Tannic acid - a bridge and suspending agent for lithium cobalt oxide and reduced graphene oxide: a lodestar for lithium-ion batteries

ABSTRACTLithium cobalt oxide (LCO) has been employed as cathode material for 40 years. However, the low solubility of LCOs in water and strong electrostatic force and H-bonding between the LCOs particles limited the use of the aqueous binders in the LCO system. We report a feasible and universal approach to fabricating a complex cathode of LCO and reduced graphene oxide (RGO). Tannic acid (TA) could simultaneously disperse LCO and RGO particles. Meanwhile, the branched polyphenol TA acts as a 'bridge' molecule for connecting the LCO and RGO, confirmed by the SEM test. The rheology properties of the PVDF slurry of cathode materials (LCO, LCO/, RGO, and TA/LCO/RGO) were also determined. It could be found that the TA could act as a crosslinking agent for the LCO and RGO particles, increasing the viscosity and storage modulus of the slurry. The cell employed the TA/LCO/RGO slurry as the cathode material, have a higher areal capacity, and had a higher redox potential than employed LCO/RGO and LCO as cathode materials, all of which could be attributed to the addition of the TA. This green molecule can be used to fabricate environmentally friendly and possibly biodegradable electrochemical energy storage devices.

Underwater Bonding with a Biobased Adhesive from Tannic Acid and Zein Protein

Herein are presented several adhesive formulations made from zein protein and tannic acid that can bind to a wide range of surfaces underwater. Higher performance comes from more tannic acid than zein, whereas dry bonding required the opposite case of more zein than tannic acid. Each adhesive works best in the environment that it was designed and optimized for. We show underwater adhesion experiments done on different substrates and in different waters (sea water, saline solution, tap water, deionized water). Surprisingly, the water type does not influence the performance to a great deal but the substrate type does. An additional unexpected result was bond strength increasing over time when exposed to water, contradicting general experiments of working with glues. Initial adhesion underwater was stronger compared to benchtop adhesion, suggesting that water helps to make the glue stick. Temperature effects were determined, indicating maximum bonding at about 30 °C and then another increase at higher temperatures. Once the adhesive was placed underwater, a protective skin formed on the surface, keeping water from entering the rest of the material immediately. The shape of the adhesive could be manipulated easily and, once in place, the skin could be broken to induce faster bond formation. Data indicated that underwater adhesion was predominantly induced by tannic acid, cross-linking within the bulk for adhesion and to the substrate surfaces. The zein protein provided a less polar matrix that helped to keep the tannic acid molecules in place. These studies provide new plant-based adhesives for working underwater and for creating a more sustainable environment.

Separation Performance of Membranes Containing Ultrathin Surface Coating of Metal-Polyphenol Network

Metal-polyphenol networks (MPNs) are being used as versatile coatings for regulating membrane surface chemistry and for the formation of thin separation layers. The intrinsic nature of plant polyphenols and their coordination with transition metal ions provide a green synthesis procedure of thin films, which enhance membrane hydrophilicity and fouling resistance. MPNs have been used to fabricate tailorable coating layers for high-performance membranes desirable for a wide range of applications. Here, we present the recent progress of the use of MPNs in membrane materials and processes with a special focus on the important roles of tannic acid-metal ion (TA-Mⁿ⁺) coordination for thin film formation. This review introduces the most recent advances in the fabrication techniques and the application areas of TA-Mⁿ⁺ containing membranes. In addition, this paper outlines the latest research progress of the TA-metal ion containing membranes and summarizes the role of MPNs in membrane performance. The impact of fabrication parameters, as well as the stability of the synthesized films, is discussed. Finally, the remaining challenges that the field still faces and potential future opportunities are illustrated.

Metal-Polyphenol Coordination at the Aqueous Contra-diffusion "Interface": A Green Way to High-Performance Iron(III)/Tannic Acid Thin-Film-Composite Nanofiltration Membranes

Thin-film-composite (TFC) nanofiltration membranes have found wide uses in environment remediation and industrial separation. There is a growing trend to avoid the use of organic solvents and toxic chemicals during membrane fabrication. Therefore, the aqueous fabrication of TFC membranes receives considerable interest as a green and sustainable process. However, it remains challenging to construct a defect-free and ultrathin film in a homogeneous aqueous phase without the assistance of an interface. The contra-diffusion process provides a special "interface" to confine the film formation within a narrow space by regulating the competition between precursor diffusion and interfacial reactions. Herein, Fe³⁺/tannic acid (TA) TFC membranes were fabricated by a contra-diffusion process. The effects of fabrication parameters on the Fe³⁺/TA TFC membrane microstructure and performance were also investigated. The negatively charged membrane performs a competitive Na₂SO₄ rejection of 95.6% with a permeation flux of 44.3 L m^-2 h^-1 under 0.6 MPa as well as more than 99.5% rejection to several anionic dyes. The as-prepared membranes perform superior nanofiltration performance compared to other reported Fe³⁺/TA-based membranes, owing to the thin and defect-free selective layers by self-regulation. Moreover, the membranes exhibit stable rejection during a long-term nanofiltration test.

Radical-Scavenging Activatable and Robust Polymeric Binder Based on Poly(acrylic acid) Cross-Linked with Tannic Acid for Silicon Anode of Lithium Storage System

The design of a novel binder is required for high-capacity silicon anodes, which typically undergo significant changes during charge/discharge cycling. Hence, in this study, a stable network structure was formed by combining tannic acid (TAc), which can be cross-linked, and poly(acrylic acid)(PAA) as an effective binder for a silicon (Si) anode. TAc is a phenolic compound and representative substance with antioxidant properties. Owing to the antioxidant ability of the C-PAA/TAc binder, side reactions during the cycling were suppressed during the formation of an appropriate solid-electrolyte interface layer. The results showed that the expansion of a silicon anode was suppressed compared with that of a conventional PAA binder. This study demonstrates that cross-linking and antioxidant capability facilitate binding and provides insights into the behavior of binders for silicon anodes. The Si anode with the C-PAA/TAc binder exhibited significantly improved cycle stability and higher Coulombic efficiency in comparison to the Si anode with well-established PAA binders. The C-PAA/TAc binder demonstrated a capacity of 1833 mA h g^-1_Si for 100 cycles, which is higher than that of electrodes fabricated using the conventional PAA binder. Therefore, the C-PAA/TAc binder offers better electrochemical performance.

Co3O4 Nanoparticles Uniformly Dispersed in Rational Porous Carbon Nano-Boxes for Significantly Enhanced Electrocatalytic Detection of H2O2 Released from Living Cells

A facile and ingenious method to chemical etching-coordinating a metal-organic framework (MOF) followed by an annealing treatment was proposed to prepare Co₃O₄ nanoparticles uniformly dispersed in rational porous carbon nano-boxes (Co₃O₄@CNBs), which was further used to detect H₂O₂ released from living cells. The Co₃O₄@CNBs H₂O₂ sensor delivers much higher sensitivity than non-etching/coordinating Co₃O₄, offering a limit of detection of 2.32 nM. The wide working range covers 10 nM-359 μM H₂O₂, while possessing good selectivity and excellent reproducibility. Moreover, this biosensor was used to successfully real-time detect H₂O₂ released from living cells, including both healthy and tumor cells. The excellent performance holds great promise for Co₃O₄@CNBs’s applications in electrochemical biomimetic sensing, particularly real-time monitor H₂O₂ released from living cells.

Multifunctional polyphenol-based silk hydrogel alleviates oxidative stress and enhances endogenous regeneration of osteochondral defects

In osteochondral defects, oxidative stress caused by elevated levels of reactive oxygen species (ROS) can disrupt the normal endogenous repair process. In this study, a multifunctional hydrogel composed of silk fibroin (SF) and tannic acid (TA), the FDA-approved ingredients, was developed to alleviate oxidative stress and enhance osteochondral regeneration. In this proposed hydrogel, SF first interacts with TA to form a hydrogen-bonded supramolecular structure, which is subsequently enzymatically crosslinked to form a stable hydrogel. Furthermore, TA had multiple phenolic hydroxyl groups that formed interactions with the therapeutic molecule E7 peptide for controlled drug delivery. In vitro investigations showed that SF-TA and SF-TA-E7 hydrogels exhibited a multitude of biological effects including scavenging of ROS, maintaining cell viability, and promoting the proliferation of bone marrow mesenchymal stem cells (BMSCs) against oxidative stress. The proteomic analysis indicated that SF-TA and SF-TA-E7 hydrogels suppressed oxidative stress, which in turn improved cell proliferation in multiple proliferation and apoptosis-related pathways. In rabbit osteochondral defect model, SF-TA and SF-TA-E7 hydrogels promoted enhanced regeneration of both cartilage and subchondral bone as compared to hydrogel without TA incorporation. These findings indicated that the multifunctional SF-TA hydrogel provided a microenvironment suitable for the endogenous regeneration of osteochondral defects.

Bimetallic polyphenol networks structure modified polyethersulfone membrane with hydrophilic and anti-fouling properties based on reverse thermally induced phase separation method

In order to improve the hydrophobicity of traditional polyethersulfone (PES) membranes, this study combined the reverse thermally induced phase separation (RTIPS) method with the constructed bimetallic polyphenol networks (BMPNs) to prepare hydrophilic anti-fouling membranes. As for BMPNs, tannic acid (TA) was served as an intermediate to construct both the inner and surface hydrophilic layers of the PES membranes. On the one hand, etching Zeolitic imidazolate framework-8 (EZIF-8) with synergistic etching and surface functionalization via TA not only retained the high pore structure of MOFs, but also had good hydrophilicity. On the other hand, the MPN hydrophilic layer was formed on the membrane surface by the combination of TA from the surface of EZIF-8 and iron ions in the coagulation bath. Therefore, BMPNs structure penetrated the interior and surface of PES membrane, which greatly improved the hydrophilic properties. In addition, the membrane with porous surfaces and spongy cross sections by RTIPS method improved the permeability and mechanical properties of the membrane by several times compared with the membrane via NIPS method. The obtained membranes in this experiment showed excellent permeability, just like pure water flux reached 1662.16 L/m² h, while BSA rejection rate remained at 92.78%. Compared with pure membrane, it showed a better flux recovery rate (FRR = 83.33%) after cleaning, and the reduction of irreversible (R_ir = 16.67%) fouling indexes indicated that the adsorption of protein was inhibited. These results suggested that the hydrophilic anti-fouling PES membranes prepared by this method possessed great application potential in membrane separation technology.

Improving Surface Functionality, Hydrophilicity, and Interfacial Adhesion Properties of High-Density Polyethylene with Activated Peroxides

Polyolefins have had limited application in advanced technologies due to their low surface energy, hydrophobicity, and weak interfacial adhesion with polar coatings. Herein, we propose the use of transition metals at their lowest oxidation state and inorganic peroxides to improve the functionality, surface free energy, hydrophilicity, and adhesion properties of high-density polyethylene (HDPE). Among the nine combinations of transition metals and peroxides used in this study, the combination of Co(II) and peroxymonosulfate (PMS) peroxide was the most effective for surface modification of HDPE, followed closely by the combination of Ru(III) and PMS. After chemical treatment, HDPE's surface functionality, composition, and energy were analyzed via Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. Hydroxyl, carbonyl, and carboxylic acid functional groups were detected on the surface, which explained the improved hydrophilicity of the modified HDPE surface; the contact angle of HDPE with DI water decreased from 94.31 to 51.95° after surface treatment. To investigate the effect of HDPE's surface functionality on its interfacial properties, its adhesion to a commercial epoxy coating was measured via pull-off strength test according to ASTM D54541. After only 20 min of surface treatment with Co(II)/PMS solution, the adhesion strength at the interface of HDPE and the epoxy coating increased by 193%, confirming the importance of polyolefins' surface functionality on their interfacial adhesion properties. The method outlined herein can improve HDPE's surface functionality by introducing sulfate radicals. It improves HDPE's hydrophilicity and adhesion properties without requiring strong acids or time-consuming pre- or post-treatment processes. This process has the potential to increase the use of polyolefins in various industries, such as for protective coatings, high performance lithium-ion battery separators, and acoustic sensors.

Preparation of porous fluorinated polyimide separator for lithium-ion batteries by non-solvent induced phase separation process

A series of novel porous fluorinated polyimide (FPI) separators containing trifluoromethyl group (–CF3) were prepared by the non-solvent induced phase separation (NIPS) strategy. The prepared FPI separator with 60% molar content (fluorinated dianhydride: non-fluorinated dianhydride: diamine = 60: 40: 100) of fluorinated groups (FPI-60%) could stably exist in the electrolyte as a LIBs separator. The resultant FPI-60% separator possesses high thermal stability with the Tg of 289.4°C and exhibits no shrinkage even at 200°C. The morphologies of the FPI-60% separators were adjusted by introducing small molecular non-solvent additives-ethanol, and the FPI-60% separators present the spongy-like and interconnected structure with different porosity as the amount of ethanol changed from 1 wt% to 10 wt%. The FPI-60% separators display excellent electrolyte uptake with 170%–200% and the ionic conductive could reach 1.17 mS/cm which is four times approximately than that of the PP separator. The lithium-ion batteries (LIBs) using FPI-60% separators with 10 wt% ethanol added show better rate capacities (102.8 mAh/g, 70.8 mAh/g of PI-10 and PP separator at 2 C, respectively) and the capacity retention rate is 93.2% after 50 cycles. The results prove that the porous FPI separator is a promising candidate for high-performance LIBs.

Photoenhanced Dual-Functional Nanomedicine for Promoting Wound Healing: Shifting Focus from Bacteria Eradication to Host Microenvironment Modulation

Pathogenic bacterial infection has become a serious medical threat to global public health. Once the skin has serious defects, bacterial invasion and the following chain reactions will be a thorny clinical conundrum, which takes a long time to heal. Although various strategies have been used to eradicate bacteria, the treatment which can simultaneously disinfect and regulate the infection-related host responses is rarely reported. Herein, inspired by the host microenvironment, a photoenhanced dual-functional nanomedicine is constructed (Hemin@Phmg-TA-MSN) for localized bacterial ablation and host microenvironment modulation. The "NIR-triggered local microthermal therapy" and positively charged surface endow the nanomedicine with excellent bacterial capture and killing activities. Meanwhile, the nanomedicine exhibits broad-spectrum reactive oxygen species (ROS) scavenging activity via the synergistic effect of hemin and tannic acid with photoenhanced electron and hydrogen transfers. Furthermore, the in vivo experiments demonstrate that the dual-functional nanomedicine not only presents robust bacterial eradication capability, but also triggers the oxidative stress and inflammatory microenvironment regulation. The work not only shows a facile and effective way for infected wound management but also provides a new horizon for designing novel and efficient anti-infection therapy shifting focus from bacteria treatment to host microenvironment modulation.

Fabrication and Analysis of Near-Field Electrospun PVDF Fibers with Sol-Gel Coating for Lithium-Ion Battery Separator

Environmental and economic concerns are driving the demand for electric vehicles. However, their development for mass transportation hinges largely on improvements in the separators in lithium-ion batteries (LIBs), the preferred energy source. In this study, innovative separators for LIBs were fabricated by near-field electrospinning (NFES) and the sol-gel method. Using NFES, poly (vinylidene fluoride) (PVDF) fibers were fabricated. Then, PVDF membranes with pores of 220 nm and 450 nm were sandwiched between a monolayer and bilayer of the electrospun fibers. Nanoceramic material with organic resin, formed by the sol-gel method, was coated onto A4 paper, rice paper, nonwoven fabric, and carbon synthetic fabric. Properties of these separators were compared with those of a commercial polypropylene (PP) separator using a scanning electron microscope (SEM), microtensile testing, differential scanning calorimetry (DSC), ion-conductivity measurement, cyclic voltammetry (CV), and charge-discharge cycling. The results indicate that the 220 nm PVDF membrane sandwiched between a bilayer of electrospun fibers had excellent ionic conductivity (~0.57 mS/cm), a porosity of ~70%, an endothermic peak of ~175 °C, better specific capacitance (~356 mAh/g), a higher melting temperature (~160 °C), and a stable cycle performance. The sol-gel coated nonwoven fabric had ionic conductivity, porosity, and specific capacitance of ~0.96 mS/cm., ~64%, and ~220 mAh/g, respectively, and excellent thermal stability despite having a lower specific capacitance (65% of PP separator) and no peak below 270 °C. The present study provides a significant step toward the innovation of materials and processes for fabricating LIB separators.

Tannic acid-functionalized HEPA filter materials for influenza virus capture

Influenza, one of the most contagious and infectious diseases, is predominantly transmitted through aerosols, leading to the development of filter-based protective equipment. Though the currently available filters are effective at removing submicron-sized particulates, filter materials with enhanced virus-capture efficiency are still in demand. Coating or chemically modifying filters with molecules capable of binding influenza viruses has received attention as a promising approach for the production of virus-capturing filters. For this purpose, tannic acid (TA), a plant-derived polyphenol, is a promising molecule for filter functionalization because of its antiviral activities and ability to serve as a cost-efficient adhesive for various materials. This study demonstrates the facile preparation of TA-functionalized high-efficiency particulate air (HEPA) filter materials and their efficiency in influenza virus capture. Polypropylene HEPA filter fabrics were coated with TA via a dipping/washing process. The TA-functionalized HEPA filter (TA-HF) exhibits a high in-solution virus capture efficiency of up to 2,723 pfu/mm² within 10 min, which is almost two orders of magnitude higher than that of non-functionalized filters. This result suggests that the TA-HF is a potent anti-influenza filter that can be used in protective equipment to prevent the spread of pathogenic viruses.

Combined strategy of blending and surface modification as an effective route to prepare antifouling ultrafiltration membranes

Ultrafiltration (UF) membranes blended with hydrophilic nanomaterials usually exhibit preferable overall performance including the membrane permeability and antifouling capability. However, the improvement in antifouling performance may be not outstanding due to the small amount of nanomaterial distributed near the membrane surface and the limited improvement in membrane hydrophilicity. Notably, excess addition of nanomaterials may lead to the decline in membrane permeability. In order to solve the above problem, we integrated the strategy of blending and surface modification to construct novel hybrid UF membranes. Novel nanohybrid was prepared via tannic acid (TA) coating on hydroxyapatite nanotubes (HANTs) and the subsequent grafting of zwitterionic polyethylenimine (ZPEI). The prepared nanohybrid (HANTs@TA-ZPEI) was incorporated with the polysulfone containing tertiary amine groups to fabricate hybrid membranes via the solution blending and the subsequent immersion-precipitation phase inversion process. Then the matrix was modified with zwitterions via the reaction of tertiary amine group with 1, 3-propane sultone. UF tests were conducted using the bovine serum albumin (BSA) and humic acid (HA) as the representative foulants. Results showed that both the permeability and the antifouling performance of the membranes achieved favorable promotion. Thereinto, the water flux of M-B0.4-Z membrane (pre blended with 0.4 wt% HANTs@TA-ZPEI in the casting solution and post-surface modified) exhibited 2.6 times that of the pristine membrane and the flux recovery ratio (FRR) for BSA and HA attained 93.4% and 96.1%, respectively. By the combination of blending and surface modification, both the membrane permeability and fouling resistant properties could attain remarkable promotion, which exerted the advantages of two methods and made up the deficiency of single blending method.

Applications of tannic acid in membrane technologies: A review

Today, membrane technologies play a big role in chemical industry, especially in separation engineering. Tannic acid, one of the most famous polyphenols, has attracted widespread interest in membrane society. In the past several years, researches on the applications of tannic acid in membrane technologies have grown rapidly. However, there has been lack of a comprehensive review for now. Here, we summarize the recent developments in this field for the first time. We comb the history of tannic acid and introduce the properties of tannic acid firstly, and then we turn our focus onto the applications of membrane surface modification, interlayers and selective layers construction and mixed matrix membrane development. In those previous works, tannic acid has been demonstrated to be capable of making a great contribution to the membrane science and technology. Especially in membrane surface/interface engineering (such as the construction of superhydrophilic and antifouling surfaces and polymer/nanoparticle interfaces with high compatibility) and development of thin film composite membranes with high permselectivity (such as developing thin film composite membranes with ultrahigh flux and high rejection), tannic acid can play a positive and great role. Despite this, there are still many critical challenges lying ahead. We believe that more exciting progress will be made in addressing these challenges in the future.

Recent Development of Polyolefin-Based Microporous Separators for Li-Ion Batteries: A Review

Secondary Li-ion batteries have been paid attention to wide-range applications of power source for the portable electronics, electric vehicle, and electric storage reservoir. Generally, lithium-ion batteries are comprised of four components including anode, cathode, electrolyte and separator. Although separators do not take part in the electrochemical reactions in a lithium-ion (Li-ion) battery, they conduct the critical functions of physically separating the positive and negative electrodes to prevent electrical short circuit while permitting the free flow of lithium ions through the liquid electrolyte that fill in their open porous structure. Hence, the separator is directly related to the safety and the power performance of the battery. Among a number of separators developed thus far, polyethylene (PE) and polypropylene (PP) porous membrane separators have been the most dominant ones for commercial Li-ion batteries over the decades because of their superior properties such as cost-efficiency, good mechanical strength and pore structure, electrochemical stability, and thermal shutdown properties. However, there are main issues for vehicular storage, such as nonpolarity, low surface energy and poor thermal stability, although the polyolefin separators have proven dependable in portable applications. Hence, in this review, we decide to provide an overview of the types of polyolefin microporous separators utilized in Li-ion batteries and the methods employed to modify their surface in detail. The remarkable results demonstrate that extraordinary properties can be exhibited by mono- and multilayer polyolefin separators if they are modified using suitable methods and materials.

Superoleophobic micro-nanostructure surface formation of PVDF membranes by tannin and a condensed silane coupling agent

A tannin-based hybrid coating was coated on the PVDF membrane surface through a simple one-step co-deposition of tannin and KH550. A micro/nano hierarchical structure was formed on the PVDF membrane surface through hydrolysis/condensation of KH550 and Michael addition reaction between oxidized tannin and an amino group revealed by the field-emission scanning electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy, which established a harsh surface. Abundant hydrophilic groups and high surface roughness endowed the modified membranes with high hydrophilicity and underwater superoleophobicity. The modified PVDF membranes possess excellent oil/water separation and antifouling performance due to the underwater superoleophobicity. Moreover, the modified membrane exhibited outstanding stability.

Biofilm Nanofiber-Coated Separators for Dendrite-Free Lithium Metal Anode and Ultrahigh-Rate Lithium Batteries

Rechargeable batteries that combine high energy density with high power density are highly demanded. However, the wide utilization of lithium metal anode is limited by the uncontrollable dendrite growth, and the conventional lithium-ion batteries (LIBs) commonly suffer from low rate capability. Here, we for the first time develop a biofilm-coated separator for high-energy and high-power batteries. It reveals that the coating of Escherichia coli protein nanofibers can improve electrolyte wettability and lithium transference number and enhance adhesion between separators and electrodes. Thus, lithium dendrite growth is impeded because of the uniform distribution of the Li-ion flux. The modified separator also enables the stable cycling of high-voltage Li|Li_1.2Mn_0.6Ni_0.2O₂ (LNMO) cells at an extremely high rate of 20 C, delivering a high specific capacity of 83.1 mA h g^-1, which exceeds the conventional counterpart. In addition, the modified separator in the Li₄Ti₅O₁₂|LNMO full cell also exhibits a larger capacity of 68.2 mA h g^-1 at 10 C than the uncoated separator of 37.4 mA h g^-1. Such remarkable performances of the modified separators arise from the conformal, adhesive, and endurable coating of biofilm nanofibers. Our work opens up a new opportunity for protein-based biomaterials in practical application of high-energy and high-power batteries.

Electrospun Core-Shell Nanofiber as Separator for Lithium-Ion Batteries with High Performance and Improved Safety

Though the energy density of lithium-ion batteries continues to increase, safety issues related to the internal short circuit and the resulting combustion of highly flammable electrolytes impede the further development of lithium-ion batteries. It has been well-accepted that a thermal stable separator is important to postpone the entire battery short circuit and thermal runaway. Traditional methods to improve the thermal stability of separators include surface modification and/or developing alternate material systems for separators, which may affect the battery performance negatively. Herein, a thermostable and shrink-free separator with little compromise in battery performance was prepared by coaxial electrospinning and tested. The separator consisted of core-shell fiber networks where poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) layer served as shell and polyacrylonitrile (PAN) as the core. This core-shell fiber network exhibited little or even no shrinking/melting at elevated temperature over 250 °C. Meanwhile, it showed excellent electrolyte wettability and could take large amounts of liquid electrolyte, three times more than that of conventional Celgard 2400 separator. In addition, the half-cell using LiNi1/3Co1/3Mn1/3O2 as cathode and the aforementioned electrospun core-shell fiber network as separator demonstrated superior electrochemical behavior, stably cycling for 200 cycles at 1 C with a reversible capacity of 130 mA·h·g−1 and little capacity decay.

Recent Development in Separators for High-Temperature Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are promising energy storage devices for integrating renewable resources and high power applications, owing to their high energy density, light weight, high flexibility, slow self-discharge rate, high rate charging capability, and long battery life. LIBs work efficiently at ambient temperatures, however, at high-temperatures, they cause serious issues due to the thermal fluctuation inside batteries during operation. The separator is a key component of batteries and is crucial for the sustainability of LIBs at high-temperatures. The high thermal stability with minimum thermal shrinkage and robust mechanical strength are the prime requirements along with high porosity, ionic conductivity, and electrolyte uptake for highly efficient high-temperature LIBs. This Review deals with the recent studies and developments in separator technologies for high-temperature LIBs with respect to their structural layered formation. The recent progress in monolayer and multilayer separators along with the developed preparation methodologies is discussed in detail. Future challenges and directions toward the advancement in separator technology are also discussed for achieving remarkable performance of separators in a high-temperature environment.