Battery Separator Research Articles

Structure Optimization for Cellulose‐Based Separator through Fiber Size Regulation for High Performance Lithium Metal Batteries

Cellulose‐based separator exhibits excellent electrolyte affinity, thermal stability, and mechanical strength, which acts as a promising alternative to commercial polyolefin separators in lithium metal batteries (LMBs). Fiber size in cellulose‐based separators plays a crucial role in determining their physicochemical structure and mechanical strength, as well as the electrochemical performance of corresponding LMBs. Herein, the fiber size in cellulose‐based separators was first time regulated to optimize their mechanical stability and the related battery performance. The influences of fiber size in the separator on chemical structure, mechanical properties, surface morphology, electrochemical behavior were investigated in detail, in which the underlying mechanism between separator structure and the related performance was elucidated. As a result, the separator optimized by fiber size regulation exhibited excellent thermal stability under 180 °C, good tensile strengths of 6.0 MPa and Young's moduli of 315.9 MPa, superior room temperature ionic conductivity of 1.87 mS cm‐1, as well as significantly improved electrochemical performance of corresponding batteries. It can be concluded that structure optimization for cellulose‐based separator through fiber size regulation is an effective and indispensable approach towards high safety and high performance LMBs.

PVDF/lithiated sulfonated poly (ether ether ketone) blend coated PE separators for high-performance lithium metal batteries

Ionic conductivity and lithium ion transference number (tLi+) of electrolytes are essential parameters governing the performances of high energy density lithium metal batteries. Although the importance of tLi+versus ionic conductivity has been theorized by simulation, the systematically experimental study of their respective effects on lithium dendrite suppression and battery performances is rarely carried out. Here, a series of polyvinylidene fluoride and lithated sulfonated poly (ether ether ketone) blend (PVDF/SPEEK-Li) coated polyethylene (PE) separators with exactly the same composition but different pore morphologies are fabricated by vapor and non-solvent induced phase separation. The effects of sulfonate group–ion interaction and pore morphologies on ionic conductivity and tLi+ of the electrolytes are studied. The performances of lithium metal batteries can be obviously improved by subtle increase of the tLi+, especially at high charge rates and even with a decrease in conductivity. Even at a high current density of 3 C, the PVDF/SPEEK-Li coated PE separator assembled lithium metal battery using a LiFePO4 cathode with a mass loading of 10.5 mg cm−2 can run stably for 200 cycles with a capacity retention of 79 %, which is superior to the PE separator assembled battery with a life of only 55 cycles.

One-step fabrication of Polyvinylidene fluoride membranes enriched with electroactive β-Phase for secondary battery separators via simultaneous near infrared radiation and electrospinning

This study reports a one-step fabrication method to prepare polyvinylidene fluoride (PVDF) membranes enriched with electroactive β-Phase in application for secondary battery separator using near infrared radiation (NIR) heated electrospinning techniques. The electrospun PVDF fibrous membranes with NIR heating applied were investigated by various characterizations and measurements. The results present that NIR heating during electrospinning not only increased the β phase content and mechanical strength of the PVDF membranes but also improved the electrochemical performances, suggesting its potential suitability in the battery separator applications.

Advanced Separator Materials for Enhanced Electrochemical Performance of Lithium-Sulfur Batteries: Progress and Prospects.

Lithium-sulfur (Li-S) batteries are promising energy storage devices owing to their high theoretical specific capacity and energy density. However, several challenges, including volume expansion, slow reaction kinetics, polysulfide shuttle effect and lithium dendrite formation, hinder their commercialization. Separators are a key component of Li-S batteries. Traditional separators, made of polypropylene and polyethylene, have certain limitations that should be addressed. Therefore, this review discusses the basic properties and mechanisms of Li-S battery separators, focuses on preparing different functionalized separators to mitigate the shuttle effect of polysulfides. This review also introduces future research trends, emphasizing the potential of separator functionalization in advancing the Li-S battery technology.

Biomass‐based functional separators for rechargeable batteries

AbstractThe global transition toward sustainable energy sources has prompted a paradigm shift in the field of energy storage. The separator is an important component in rechargeable batteries, which facilitates the rapid passage of ions and ensures the safety and efficiency of the electrochemical process by preventing direct contact between the anode and cathode. Traditional polyolefin‐based separators induce environmental concerns due to their nonbiodegradable nature. Biomass‐based separators derived from renewable sources such as plant fibers, agricultural waste, and biopolymers have emerged as promising alternatives to traditional polymer separators. In this review, we summarize the current state and development of biomass‐based separators for high‐performance batteries, including innovative manufacturing techniques, novel biomass materials, functionalization strategies, performance evaluation methods, and potential applications. The review also delves into the environmental impact and sustainability analysis of biomass‐based separators, offering insights into the potential of biomass as the most sustainable resource for future energy storage solutions. This review could provide a holistic understanding of the advancements and potential of biomass‐based separators, shedding light on the path toward sustainable and efficient energy storage based on biomass‐derived separators.

Environmental Stress-Induced Fracture Behavior of Polypropylene Battery Separators: Insights into Creep Behavior and Mechanical Stability

Environmental Stress-Induced Fracture Behavior of Polypropylene Battery Separators: Insights into Creep Behavior and Mechanical Stability

Interfacial engineering assists dendrite-inhibiting separators for high-safety Li-S batteries

The impediments to the safety and cyclic performance of lithium-sulfur (Li-S) batteries arise from the lithium dendrite growth and “shuttle effect” of polysulfides. Herein, an interfacial engineering was proposed by pre-irradiation grafting acrylic acid (AA) into polypropylene (PP) separator to achieve a dendrite-inhibiting and high stability functional separators. The abundant –COOH groups, introduced to the surface of PP along with AA, effectively modulate lithium dendrite growth by eliminating the local aggregation of Li+ on the surface of the anode and restrain the “shuttle effect” of polysulfides by the physical confinement and electrostatic interaction. Lithium-sulfur batteries with the grafted separator achieved a high initial capacity of 1108.7 mAh g−1 with an ultralow attenuation rate of 0.012 % per cycle at 1C, outperforming the traditional commercial PP separator. Additionally, the grafted separator also appeared a remarkable flexibility owing to the chemical bond between AA and PP-chain. Notably, the pre-irradiation grafting process, characterized by a mild reaction condition and high economic benefit, endowed the grafted separator with outstanding potential for industrialization. Those results showed the practical prospects of the grafted separator, offering a promising new option for high-safety Li-S batteries.

Preparation of polyethylene based composite nanofiltration membrane and its application in removal of heavy metals for water purification

The commercial polyethylene (PE) battery separator is well-suited as support for nanofiltration owing to its thickness of 7 um, high porosity, and strong mechanical properties. A new polyethylene based thin-film composite membrane was fabricated on the catechol/polyethyleneimine (CCh/PEI) modified PE support by pre-diffusion interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). By regulating the properties of the CCh/PEI layer and the PIP to influence the diffusion of PIP, a distinct worm-like structure in the polyamide (PA) layer was found, which provides more water penetration sites. After grafting melamine on the surface of PA layer, the TFC membrane exhibited outstanding chlorine resistance and the permeability of 12.5 L·m−2·h−1·bar−1 with the Mg2+ rejection of 94.5 %. Due to its small pore size, strong positively charged, and high adsorption capacity, the TFC membrane showed high rejection of heavy metal ions through pore size sieving, Donnan effect and adsorption. Therefore, it has great potential for water purification from heavy metal ions.

Green power solutions: Advancements in eco‐friendly cellulose‐derived composite battery separators—Material properties and processing techniques

AbstractBatteries play a crucial role in our daily lives, with separators being a key component influencing their functionality. The separators based on petrochemical for example polythene and polypropylene have been long favored for their chemical and thermal stability, their drawbacks in terms of sustainability, eco‐efficiency, and associated environmental risks are undeniable. In pursuit of sustainable development, there is a growing demand for biopolymer composite separators that offer a compelling combination of low cost, high mechanical and thermal stability, biodegradability, and renewability. Among these alternatives, cellulose‐derived separators have garnered significant attention from the scientific community. This review delivers a brief overview of cellulose's chemical structure, their types, delving into the intricate interplay of various electrodes and electrolytic solutions. The focus is then directed towards exploring diverse preparatory methods for cellulose‐derived separators, along with highlighting the promising factors associated with their adoption. Special attention is given to cellulose composite separators and the challenges they present.Highlights Cellulose‐based composite separators in LIB/SIB batteries are discussed. Preparatory methods for eco‐friendly cellulose‐derived composite battery separators. Prominent affecting factors of separator performance have been elaborated. Special attention to the challenges cellulose composite separators present.

Hydrophilicity regulation and microstructure change of Ethylene-tetrafluoroethylene copolymer films grafted acrylic acid by irradiation-induced co-grafting

The surface hydrophobicity of Ethylene-tetrafluoroethylene copolymer(ETFE) films limits its application in functional membranes. However, the surface energy of ETFE films is extremely low and the interface compatibility is poor, which makes it difficult to modify the surface hydrophilicity. In this work, acrylic acid was grafted onto ETFE films by the irradiation-induced co-grafting method. The effects of adsorbed dose on the structure and properties of grafted ETFE films were investigated by the various characterization methods. By irradiation- induced grafting method, the surface of ETFE films were successfully grafted with acrylic acid to modify its hydrophilicity. With the increase of absorbed dose, the contact angle of the ETFE was reduced from 102° to 44°, the microstructure and the natural crystallization area was destroyed, and the radius of gyration decreased. The destruction of the structure leads to a decrease in mechanical properties. When the absorbed dose is 60 kGy, it exhibits good hydrophilicity and mechanical properties. The contact angle, breaking strength and elongation at break are 68°, 13.0 MPa and 72.6 %, respectively. It clarified the effect of adsorbed dose on the structure of ETFE grafted acrylic acid, and helped to expand the application of ETFE in battery separators and other fields.

Amorphous FeSnOx Nanosheets with Hierarchical Vacancies for Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries, noted for their low material costs and high energy density, are emerging as a promising alternative to lithium-ion batteries (LIBs) in various applications including power grids and standalone renewable energy systems. These batteries are commonly assembled with glass fiber membranes, which face significant challenges like the dissolution of polysulfides, sluggish sulfur conversion kinetics, and the growth of Na dendrites. Here, we develop an amorphous two-dimensional (2D) iron tin oxide (A-FeSnOx) nanosheet with hierarchical vacancies, including abundant oxygen vacancies (Ovs) and nano-sized perforations, that can be assembled into a multifunctional layer overlaying commercial separators for RT Na-S batteries. The Ovs offer strong adsorption and abundant catalytic sites for polysulfides, while the defect concentration is finely tuned to elucidate the polysulfides conversion mechanisms. The nano-sized perforations aid in regulating Na ions transport, resulting in uniform Na deposition. Moreover, the strategic addition of trace amounts of Ti3C2 (MXene) forms an amorphous/crystalline (A/C) interface that significantly improves the mechanical properties of the separator and suppresses dendrite growth. As a result, the task-specific layer achieves ultra-light (~0.1 mg cm-2), ultra-thin (~200 nm), and ultra-robust (modulus=4.9 GPa) characteristics. Consequently, the RT Na-S battery maintained a high capacity of 610.3 mAh g-1 and an average Coulombic efficiency of 99.9 % after 400 cycles at 0.5 C.

Rheological and light scattering analyses for characterizing phase separation of polymer solutions in lithium-ion battery separator coating system

Rheological and light scattering analyses for characterizing phase separation of polymer solutions in lithium-ion battery separator coating system

A Polymer‐Sol Binder Realizes Single‐Particle Binding for Nacre‐Like Piezoelectric Nanocomposites and Component‐Integrated Batteries

AbstractAchieving precisely defined and stable component binding is of great interest for composite materials and batteries, but very challenging owing to the lack of effective strategies to manipulate the binder itself. Here, a concept of single‐particle binding (SPB) strategy is proposed based on a polymer‐sol binder to conquer the above challenge. To do that, a polymer‐sol binder is first prepared by dispersing commercial poly(vinylidene fluoride) (PVDF) powder into a mixture of its solvent and non‐solvent with a rational weight ratio of 8:2. Then, by manipulating this PVDF‐sol microfluid, PVDF particles are uniformly and singly introduced onto the surface of other components, such as graphene oxide nanosheets and battery separators. Results further show that the temperature‐induced sol–gel transition of the microfluid finally generates single‐particle fusion and strong component binding with commercial separators (31.6 N m−1). Meanwhile, a surface‐swelling model is proposed to understand its binding mechanism. Finally, this unique SPB strategy has been employed to fabricate nacre‐like nanocomposites with advanced self‐polarized piezoelectricity (23.0 mV N−1), and component‐integrated batteries with robust separator/electrode interphases. This SPB strategy with the PVDF‐sol binder may inspire significant studies on polymer sol, microfluidics, nanocomposites, battery interfaces and beyond.

Application of Nd-MOF derived Nd2O3-C/KB and Nd2O3-C/CNT for lithium-sulfur battery separators

Lithium-sulfur batteries have received widespread attention because of their good development prospects. Nevertheless, many problems such as the shuttle effect and poor conductivity seriously affect the development of lithium-sulfur batteries. In order to solve these obstacles, we use Nd-MOF/KB and Nd-MOF/CNT precursor to achieve Nd2O3-C/KB and Nd2O3-C/CNT composites via high-temperature carbonization, which are applied as separator coating layer. The high-temperature calcined Nd2O3-C/KB and Nd2O3-C/CNT have rich microporous and mesoporous structures which are proved to be good polysulfide absorbers. What’s more, the Nd2O3-C nanoparticles embedded in KB and CNT can accelerate the catalytic conversion of polysulfides rapidly, which in turn improves the electrochemical performance of the battery. Based on the above advantages, Nd2O3-C/KB and Nd2O3-C/CNT separator batteries show reliable electrochemical performances. Additionally, the Nd2O3-C/KB separator batteries have better cycle and rate performances because of the higher conductivity and porosity of KB.

High-performance Li[sbnd]S battery separators based on F-element doped loofah sponge biomass carbon materials

Lithium-sulfur batteries are a new high-performance battery technology that consists of lithium metal as the negative electrode and sulfide material as the positive electrode. Compared with conventional lithium-ion batteries, LiS batteries offer higher energy density as well as cost advantages. However, the shuttle effect of polysulfides in LiS batteries can lead to serious degradation of cycling performance, etc., which hinders the commercialization of LiS batteries. For this reason, in this study, the green biomass material loofah sponge was used as a precursor, and the porous carbon material was produced by calcination after introducing the F element and used as a separator modifier to curb the shuttle effect, which is environmentally friendly, economical, and green. Comparative studies were conducted on ordinary PP separators, separators made of carbon materials before and after F-doping. The experimental results show that the F-doped porous carbon material cladding membrane improves the charge/discharge capacity, multiplication performance, and cycle stability of LiS batteries, which reflects the great potential in practical applications.

Highly Economical and Efficient Polyethylene Separator for Vanadium Redox Flow Battery

Highly Economical and Efficient Polyethylene Separator for Vanadium Redox Flow Battery

The mechanism of in-homogeneous mass transfer process of separators in lithium-ion batteries.

The liquid-phase mass transport is the key factor affecting battery stability. The influencing mechanism of liquid-phase mass transport in the separators is still not clear, the internal environment being a complex multi-field during the service life of lithium-ion batteries. The liquid-phase mass transport in the separators is related to the microstructure of the separator and the physicochemical properties of electrolytes. Here, in-situ local electrochemical impedance spectra were developed to investigate local inhomogeneities in the mass transfer process of lithium-ion batteries. The geometric microstructure of the separator affects the mass transfer process, with a reduction in porosity leading to increased overpotentials. There is a competitive relationship among porosity, tortuosity, and membrane thickness in the geometric parameters of the separator, resulting in a peak of polarization. The resistance of the liquid-phase mass transfer process is positively correlated with the viscosity of the electrolyte, making ion migration difficult due to high viscosity. Polarization is closely related to the electrochemical performance, so a phase diagram of battery performance and inhomogeneous mass transfer was developed to guide the design of the battery. This study provides a guiding basis for the development of high stability lithium-ion batteries.

Recent progress of advanced separators for Li-ion batteries

Recent progress of advanced separators for Li-ion batteries

Eco-Friendly Lithium Separators: A Frontier Exploration of Cellulose-Based Materials.

Lithium-ion batteries, as an excellent energy storage solution, require continuous innovation in component design to enhance safety and performance. In this review, we delve into the field of eco-friendly lithium-ion battery separators, focusing on the potential of cellulose-based materials as sustainable alternatives to traditional polyolefin separators. Our analysis shows that cellulose materials, with their inherent degradability and renewability, can provide exceptional thermal stability, electrolyte absorption capability, and economic feasibility. We systematically classify and analyze the latest advancements in cellulose-based battery separators, highlighting the critical role of their superior hydrophilicity and mechanical strength in improving ion transport efficiency and reducing internal short circuits. The novelty of this review lies in the comprehensive evaluation of synthesis methods and cost-effectiveness of cellulose-based separators, addressing significant knowledge gaps in the existing literature. We explore production processes and their scalability in detail, and propose innovative modification strategies such as chemical functionalization and nanocomposite integration to significantly enhance separator performance metrics. Our forward-looking discussion predicts the development trajectory of cellulose-based separators, identifying key areas for future research to overcome current challenges and accelerate the commercialization of these green technologies. Looking ahead, cellulose-based separators not only have the potential to meet but also to exceed the benchmarks set by traditional materials, providing compelling solutions for the next generation of lithium-ion batteries.

Pristine MOF Materials for Separator Application in Lithium-Sulfur Battery.

Lithium-sulfur (Li-S) batteries have attracted significant attention in the realm of electronic energy storage and conversion owing to their remarkable theoretical energy density and cost-effectiveness. However, Li-S batteries continue to face significant challenges, primarily the severe polysulfides shuttle effect and sluggish sulfur redox kinetics, which are inherent obstacles to their practical application. Metal-organic frameworks (MOFs), known for their porous structure, high adsorption capacity, structural flexibility, and easy synthesis, have emerged as ideal materials for separator modification. Efficient polysulfides interception/conversion ability and rapid lithium-ion conduction enabled by MOFs modified layers are demonstrated in Li-S batteries. In this perspective, the objective is to present an overview of recent advancements in utilizing pristine MOF materials as modification layers for separators in Li-S batteries. The mechanisms behind the enhanced electrochemical performance resulting from each design strategy are explained. The viewpoints and crucial challenges requiring resolution are also concluded for pristine MOFs separator in Li-S batteries. Moreover, some promising materials and concepts based on MOFs are proposed to enhance electrochemical performance and investigate polysulfides adsorption/conversion mechanisms. These efforts are expected to contribute to the future advancement of MOFs in advanced Li-S batteries.