Novel Ceramic-Grafted Separator with Highly Thermal Stability for Safe Lithium-Ion Batteries

Two-dimensional titania-assisted synthesis of flaky amorphous nano-alumina as a high-performance separator coating for lithium metal batteries

The polyolefin separators in lithium metal batteries face issues with low thermal stability, poor electrolyte wettability, and inferior mechanical properties. As a coating on polypropylene separators, flaky amorphous alumina is poised to promote mechanical properties and uniform lithium deposition with enhanced thermal stability, wettability, and Li+ transport, but the related study has been rarely conducted so far. This study introduces a flaky nano-alumina synthesized via a nanosheet-seeding method, showcasing its efficacy as a separator coating. The amorphous nano-alumina exhibits a high specific surface area of 228.1 m2/g, leading to exceptional electrolyte uptake (243 %), ionic conductivity (1.13 mS cm-1), and lithium-ion transference number (0.58). When integrated into LiFePO4||Li cells, the amorphous Al2O3-coated separators demonstrate superior rate performance and cycling stability. Moreover, Li||Li symmetric batteries exhibit excellent stability against lithium dendrite growth, achieving over 1000 h of stable cycling at 1 mA cm-2. Density functional theory (DFT) simulations indicate that the amorphous structure promotes Li+ ion diffusion and tolerates doping with foreign elements, positioning flaky amorphous nano-alumina as a promising material for high-performance battery coatings.

Polybenzimidazole Composite Separators Engineered from MOFs-HNTs Composites Applicated in Lithium-Ion Batteries

Incorporating inorganic nanostructured materials into polymeric separators for lithium-ion batteries (LIBs) enhances properties such as ionic conductivity, electrolyte wettability, and thermal resistance. However, poor interfacial compatibility between inorganic materials and the polymeric matrix remains a significant challenge. In this study, Zr-based UiO-66 metal-organic frameworks (MOFs) is employed as an interfacial binder between halloysite nanotubes (HNTs) and a poly-(arylene ether benzimidazole) (OPBI) matrix, preparing porous separators using the non-solvent phase separation (NIPS) method. The UiO-66 MOFs promote strong adhesion of HNTs to the OPBI chains, creating a more cohesive inorganic-organic system, as confirmed by molecular dynamics (MD) simulations of binding energy. The resulting OPBI@M-H10 composite separator exhibits high porosity (80%), an electrolyte absorption capacity of 377%, and an ionic conductivity of 1.59 mS·cm⁻¹. Furthermore, LiFePO4 half-cells assembled with this composite separator show a discharge capacity of 161 mAh·g⁻¹ and a retention rate of 97.96% after 200 charge-discharge cycles. The separator also demonstrates excellent electrode stability in the plating/stripping test of Li symmetric cells, lasting up to 1600 hours and effectively inhibiting dendrite growth on the Li anode. This approach provides a promising solution for high-performance LIBs separators and paves the way for advancements in LIBs technology and energy storage applications.

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.

Stable anode/separator interface enabled by graft modification of polypropylene separator via electron beam irradiation technique toward high-performance sodium metal batteries

Sodium metal batteries (SMBs) are considered as strong alternatives to lithium-ion batteries (LIBs), due to the inherent merits of sodium metal anodes (SMAs) including low redox potential (-2.71 V vs. SHE), high theoretical capacity (1166 mAh g-1), and abundant resources. However, the uncontrollable Na dendrite growth has significantly impeded the practical deployment of SMBs. Separator modification has emerged as an effective strategy for substantially enhancing the performance of SMAs. Herein, for the first time, we present the successful grafting polyacrylic acid (PAA) onto polypropylene (PP) separators (denoted as PP-g-PAA) using highly efficient electron beam (EB) irradiation to improve the cyclability of SMAs. The polar carboxyl groups of PAA can facilitate the electrolyte wetting and provide ample mechanical strength to resist dendrite penetration. Consequently, the regulation of Na+ ion flux enables uniform Na+ deposition with dendrite-free morphology, facilitated by the favorable anode/separator interface. The PP-g-PAA separator significantly enhances the cyclability of fabricated cells. Notably, the lifespan of Na||Na symmetric cells can be extended up to 5519 h at 1 mA cm-2 and 1 mAh cm-2. The stable design of the anode/separator interface achieved through polyolefin separator modification presented in this study holds promise for the further advancement of next-generation advanced battery systems.

Bio-Based Aerogels in Energy Storage Systems

Bio-aerogels have emerged as promising materials for energy storage, providing a sustainable alternative to conventional aerogels. This review addresses their syntheses, properties, and characterization challenges for use in energy storage devices such as rechargeable batteries, supercapacitors, and fuel cells. Derived from renewable sources (such as cellulose, lignin, and chitosan), bio-based aerogels exhibit mesoporosity, high specific surface area, biocompatibility, and biodegradability, making them advantageous for environmental sustainability. Bio-based aerogels serve as electrodes and separators in energy storage systems, offering desirable properties such as high specific surface area, porosity, and good electrical conductivity, enhancing the energy density, power density, and cycle life of devices. Recent advancements highlight their potential as anode materials for lithium-ion batteries, replacing non-renewable carbon materials. Studies have shown excellent cycling stability and rate performance for bio-aerogels in supercapacitors and fuel cells. The yield properties of these materials, primarily porosity and transport phenomena, demand advanced characterization methods, and their synthesis and processing methods significantly influence their production, e.g., sol-gel and advanced drying. Bio-aerogels represent a sustainable solution for advancing energy storage technologies, despite challenges such as scalability, standardization, and cost-effectiveness. Future research aims to improve synthesis methods and explore novel applications. Bio-aerogels, in general, provide a healthier path to technological progress.

Facile one-pot synthesis of biomass-derived activated carbon as an interlayer material for a BAC/PE/Al2O3 dual coated separator in Li-S batteries

Lithium-sulfur batteries (LSB) are an attractive alternative electrochemical energy storage device compared to conventional lithium-ion batteries due to their higher theoretical capacity and energy density. Despite these advantages, it is still difficult to commercialize LSB because of poor electrochemical performance caused by the dissolution of soluble lithium polysulfides (LiPS). To solve these critical issues, a multi-functional separator was prepared using biomass-derived activated carbon (BAC) and a ceramic layer on the polyethylene (PE) separator. For this purpose, BAC was synthesized by a facile one-pot synthesis method by a specifically designed furnace using various forms of milk waste. The multi-functional separator suppresses the effect of LiPS dissolution and increases the Li+ diffusion kinetics. BAC was able to absorb the LiPS shuttle, as confirmed by UV-vis measurements and X-ray photoelectron spectroscopy (XPS). LSB cells assembled using this multi-functional separator show a higher discharge capacity of 1092.5 mA h g-1 at 0.1 C-rate, while commercial PE separators deliver a specific capacity of 811.8 mA h g-1. These novel separators were also able to suppress lithium dendrites during cycling. This work offers a novel and simple approach for streamlining the synthesis process of BAC and applying it to LSB, aiding in the development of sustainable energy sources.

Flattening of Lithium Plating in Carbonate Electrolytes Enabled by All-In-One Separator

The uncontrollable dendritic growth of metallic lithium during repeated cycling in carbonate electrolytes is a crucial obstacle hindering the practical use of Li-metal batteries (LMBs). Among numerous approaches proposed to mitigate the intrinsic constraints of Li metal, the design of a functional separator is an attractive approach to effectively suppress the growth of Li dendrites because direct contact with both the Li metal surface and the electrolyte is maintained. Here, a newly designed all-in-one separator containing bifunctional CaCO₃ nanoparticles (CPP separator) is proposed to achieve the flattening of Li deposits on the Li electrode. Strong interactions between the highly polar CaCO₃ nanoparticles and the polar solvent reduces the ionic radius of the Li⁺ -solvent complex, thus increasing the Li⁺ transference number and leading to a reduced concentration overpotential in the electrolyte-filled separator. Furthermore, the integration of CaCO₃ nanoparticles into the separator induces the spontaneous formation of mechanically-strong and lithiophilic CaLi₂ at the Li/separator interface, which effectively decreases the nucleation overpotential toward Li plating. As a result, the Li deposits exhibit dendrite-free planar morphologies, thus enabling excellent cycling performance in LMBs configured with a high-Ni cathode in a carbonate electrolyte under practical operating conditions.

Novel Functionalized Boron Nitride Nanosheets Achieved by Radiation-Induced Oxygen Radicals and Their Enhancement for Polymer Nanocomposites

Boron nitride nanosheets (BNNSs) exfoliated from hexagonal boron nitride (h-BN) show great potential in polymer-based composites due to their excellent mechanical properties, highly thermal conductivity, and insulation properties. Moreover, the structural optimization, especially the surface hydroxylation, of BNNSs is of importance to promote their reinforcements and optimize the compatibility of its polymer matrix. In this work, BNNSs were successfully attracted by oxygen radicals decomposed from di-tert-butylperoxide (TBP) induced by electron beam irradiation and then treated with piranha solution. The structural changes of BNNSs in the modification process were deeply studied, and the results demonstrate that the as-prepared covalently functionalized BNNSs possess abundant surface hydroxyl groups as well as reliable structural integrity. Of particular importance is that the yield rate of the hydroxyl groups is impressive, whereas the usage of organic peroxide and reaction time is greatly reduced due to the positive effect of the electron beam irradiation. The comparisons of PVA/BNNSs nanocomposites further indicate that the hydroxyl-functionalized BNNSs effectively promote mechanical properties and breakdown strength due to the enhanced compatibility and strong two-phase interactions between nanofillers and the polymer matrix, which further verify the application prospects of the novel route proposed in this work.

A Review of Nonaqueous Electrolytes, Binders, and Separators for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are the most important electrochemical energy storage devices due to their high energy density, long cycle life, and low cost. During the past decades, many review papers outlining the advantages of state-of-the-art LIBs have been published, and extensive efforts have been devoted to improving their specific energy density and cycle life performance. These papers are primarily focused on the design and development of various advanced cathode and anode electrode materials, with less attention given to the other important components of the battery. The “nonelectroconductive” components are of equal importance to electrode active materials and can significantly affect the performance of LIBs. They could directly impact the capacity, safety, charging time, and cycle life of batteries and thus affect their commercial application. This review summarizes the recent progress in the development of nonaqueous electrolytes, binders, and separators for LIBs and discusses their impact on the battery performance. In addition, the challenges and perspectives for future development of LIBs are discussed, and new avenues for state-of-the-art LIBs to reach their full potential for a wide range of practical applications are outlined.

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Experimental Study on Thermal-Induced Runaway in High Nickel Ternary Batteries

Recently, fire and explosion accidents associated with lithium ion battery failure occurred frequently. Safety has become one of the main constraints on the wide application of lithium ion batteries in the field of electric vehicles (EVs). By using a simultaneous thermal analyzer (STA8000) and accelerating rate calorimetry (ARC), we studied the thermal stability of high nickel battery materials and the high temperature thermal runaway of the battery, combining the two experimental results to analyze the battery thermal runaway process. We studied the temperature difference between inside and outside during thermal runaway by arranging two temperature sensors inside and outside the battery. The chemical reactions of the battery at high temperature through the thermal performance of the anode, cathode, and separator are also revealed. In-depth exploration of the occurrence process and the trigger mechanism of thermal runaway of lithium batteries was made. The main findings of the study are as follows: The temperature at which the anode materials begin to decompose is 77.13 °C, caused by decomposition of the solid electrolyte interface and the temperature at which the cathode materials begin to decompose is 227.09 °C. The maximum surface temperature of the battery during thermal runaway is 641.41 °C; and the maximum inside temperature of the battery is 1117.80 °C. The time difference between the maximum temperatures inside and outside the battery is 40 s. The thermal runaway temperature of the battery T _c is 228.47 °C, which is mainly contributed by the internal short circuit of the anode and cathode to release Joule heat and the cathode/electrolyte reaction. The maximum temperature of T _m is 642.65 °C, which is mainly caused by the reaction between oxygen and electrolyte.

Photopatternable Porous Separators for Micro-Electrochemical Energy Storage Systems

The miniaturization of electrochemical energy storage (EES) systems, one of the key challenges facing the rapid expansion of the Internet-of-Things, has been limited by poor performance of the various energy-storage components at the micrometer scale. Here, the development of a unique photopatternable porous separator that overcomes the electrolyte difficulties involving resistive losses at small dimensions is reported. The separator is based on modifying the chemistry of SU-8, an epoxy-derived photoresist, through the addition of a miscible ionic liquid. The ionic liquid serves as a templating agent, which is selectively removed by solution methods, leaving the SU-8 scaffold whose interconnected porosity provides ion transport from the confined liquid electrolyte. The photopatternable separator exhibits good electrochemical, chemical, thermal, and mechanical stability during the operation of electrochemical devices in both 2D and 3D formats. For the latter, the separator demonstrates the ability to form conformal coatings over 3D structures. The development of the photopatternable separator overcomes the electrolyte issues, which have limited progress in the field of micro-EES.

Graphene's Role in Emerging Trends of Capacitive Energy Storage

Technological breakthroughs in energy storage are being driven by the development of next-generation supercapacitors with favorable features besides high-power density and cycling stability. In this innovation, graphene and its derived materials play an active role. Here, the research status of graphene supercapacitors is analyzed. Recent progress is outlined in graphene assembly, exfoliation, and processing techniques. In addition, electrochemical and electrical attributes that are increasingly valued in next-generation supercapacitors are highlighted along with a summary of the latest research addressing chemical modification of graphene and its derivatives for future supercapacitors. The challenges and solutions discussed in the review hopefully will shed light on the commercialization of graphene and a broader genre of 2D materials in energy storage applications.

Ionic Covalent Organic Frameworks for Energy Devices

Covalent organic frameworks (COFs) are a class of porous crystalline materials whose facile preparation, functionality, and modularity have led to their becoming powerful platforms for the development of molecular devices in many fields of (bio)engineering, such as energy storage, environmental remediation, drug delivery, and catalysis. In particular, ionic COFs (iCOFs) are highly useful for constructing energy devices, as their ionic functional groups can transport ions efficiently, and the nonlabile and highly ordered all-covalent pore structures of their backbones provide ideal pathways for long-term ionic transport under harsh electrochemical conditions. Here, current research progress on the use of iCOFs for energy devices, specifically lithium-based batteries and fuel cells, is reviewed in terms of iCOF backbone-design strategies, synthetic approaches, properties, engineering techniques, and applications. iCOFs are categorized as anionic COFs or cationic COFs, and how each of these types of iCOFs transport lithium ions, protons, or hydroxides is illustrated. Finally, the current challenges to and future opportunities for the utilization of iCOFs in energy devices are described. This review will therefore serve as a useful reference on state-of-the-art iCOF design and application strategies focusing on energy devices.

Application of a Modified Porphyrin in a Polymer Electrolyte with Superior Properties for All-Solid-State Lithium Batteries

Porphyrins and their derivatives are a unique class of multifunctional and modifiable π-conjugated heterocyclic organic molecules, which have been widely applied in the fields of optoelectronic devices and catalysis. However, the application of porphyrins in polymer electrolytes for all-solid-state lithium-ion batteries (ASSLIBs) has rarely been reported. Herein, porphyrin molecules modified by polyether chains are used for composite solid-state polymer electrolytes (CSPEs) for the first time. The introduction of a modified porphyrin in an electrolyte can not only promote the electrochemical properties by constructing ordered ion channels via the intermolecular interaction between π-conjugated heterocyclic porphyrins, but also significantly improve the mechanical strength and interface contact between the electrolyte membrane and the lithium metal anode. Consequently, the all-solid-state batteries assembled by the modified porphyrin composite polymer electrolyte, LiFePO₄ cathodes, and Li anodes deliver a higher discharge capacity of 158.2 mA h g^-1 at 60 °C, 0.2 C, which remains at 153.6 mA h g^-1 after 120 cycles with an average coulombic efficiency of ∼99.60%. Furthermore, the flexible porphyrin-based composite polymer electrolyte can also enable a Li || LiCoO₂ battery to exhibit a maximum discharge capacity of 108.6 mA h g^-1 at 60 °C, 0.1 C with an active material loading of 2-3 mg cm^-2, which is unable to realize for the corresponding batteries with a pure PEO-based polymer electrolyte. This work not only broadens the application scope of porphyrins, but also proposes a novel method to fabricate CSPEs with improved electrochemical and mechanical properties, which may shed new light on the development of CSPEs for next-generation high-energy-density lithium-ion batteries.

Robust and High-Temperature-Resistant Nanofiber Membrane Separators for Li-Metal, Li-Sulfur, and Aqueous Li-Ion Batteries

Mechanically strong separators with good electrolyte wettability and low-shrinkage properties are desirable for highly efficient and safe lithium batteries. In this study, multifunctional nanofiber membranes are fabricated by electrospinning a homogeneous solution containing amphiphilic poly(ethylene glycol)diacrylate-grafted siloxane and polyacrylonitrile. After the chemical cross-linking of siloxane, the prepared nanofiber membranes are found to exhibit good mechanical properties, high thermostability, and superior electrolyte-philicity with aqueous and nonaqueous electrolytes. Li-metal cells with the fabricated membrane separator exhibit high cycling stability (Coulombic efficiency of 99.8% after 1000 cycles). Moreover, improved cycling stability of Li-sulfur batteries can be achieved using these membrane separators. These membrane separators can be further used in flexible aqueous lithium-ion batteries and exhibit steady electrochemistry performance. This work opens up a potential route for designing multifunctional universal separators for rechargeable batteries.

Design of Block-Copolymer Nanoporous Membranes for Robust and Safer Lithium-Ion Battery Separators

Lithium-ion batteries (LIBs) suffer from unsatisfied performance and safety risks mainly because of the separators. Herein, a block copolymer (BCP) composed of robust and electrolyte-affinitive polysulfone (PSF) and Li+-affinitive polyethylene glycol (PEG) is rationally designed to prepare a new type of LIB separator. The copolymer is subjected to selective swelling, producing nanoporous membranes with PEG chains enriched along the pore walls. Intriguingly, when used as LIB separators, thus-produced BCP membranes efficiently integrate the merits of both PSF and PEG chains, endowing the separators thermal resistance as high as 150 °C and excellent wettability. Importantly, the nanoporous separator is able to close the pores with a temperature of 125 °C, offering the battery a thermal shutdown function. The membrane exhibits ultrahigh electrolyte uptake up to 501% and a prominent ionic conductivity of 10.1 mS cm-1 at room temperature. Batteries assembled with these membranes show excellent discharge capacity and C-rate performance, outperforming batteries assembled from other separators including the extensively used Celgard 2400. This study demonstrates a facile strategy, selective swelling of block copolymer, to engineer high-performance and safer LIB separators, which is also applicable to produce advanced copolymer-based separators for other types of batteries.

Structure and electrochemical properties of hierarchically porous carbon nanomaterials derived from hybrid ZIF-8/ZIF-67 bi-MOF coated cyclomatrix poly(organophosphazene) nanospheres

Hierarchically porous carbon nanostructures with intrinsically doped heteroatoms and metal elements are attractive for electrochemical energy storage applications.

The design of a multifunctional separator regulating the lithium ion flux for advanced lithium-ion batteries

Herein, we design a controllable approach for preparing multifunctional polybenzimidazole porous membranes with superior fire-resistance, excellent thermo-stability, and high wettability. Specifically, the recyclable imidazole is firstly utilized as the eco-friendly template for micropores formation, which is an interesting finding and has tremendous potential for low-cost industrial production. The unique backbone structure of the as-prepared polybenzimidazole porous membrane endows the separator with superb thermal dimensional stability at 300 °C. Most significantly, the inherent flame retardancy of polybenzimidazole can ensure the high security of lithium-ion batteries, and the existence of polar groups of imidazole can regulate the Li+ flux and improve the ionic conductivity of lithium ions. Notably, the cell with a polybenzimidazole porous membrane presents higher capability (131.7 mA h g-1) than that of a commercial Celgard membrane (95.4 mA h g-1) at higher charge-discharge density (5C), and it can work normally at 120 °C. The fascinating comprehensive properties of the polybenzimidazole porous membrane with excellent thermal-stability, satisfying wettability, superb flame retardancy and good electrochemical performance indicate its promising application for high-safety and high-performance lithium-ion batteries.

A Review on Inorganic Nanoparticles Modified Composite Membranes for Lithium-Ion Batteries: Recent Progress and Prospects

Separators with high porosity, mechanical robustness, high ion conductivity, thin structure, excellent thermal stability, high electrolyte uptake and high retention capacity is today's burning research topic. These characteristics are not easily achieved by using single polymer separators. Inorganic nanoparticle use is one of the efforts to achieve these attributes and it has taken its place in recent research. The inorganic nanoparticles not only improve the physical characteristics of the separator but also keep it from dendrite problems, which enhance its shelf life. In this article, use of inorganic particles for lithium-ion battery membrane modification is discussed in detail and composite membranes with three main types including inorganic particle-coated composite membranes, inorganic particle-filled composite membranes and inorganic particle-filled non-woven mates are described. The possible advantages of inorganic particles application on membrane morphology, different techniques and modification methods for improving particle performance in the composite membrane, future prospects and better applications of ceramic nanoparticles and improvements in these composite membranes are also highlighted. In short, the contents of this review provide a fruitful source for further study and the development of new lithium-ion battery membranes with improved mechanical stability, chemical inertness and better electrochemical properties.

A SuperLEphilic/Superhydrophobic and Thermostable Separator Based on Silicone Nanofilaments for Li Metal Batteries

Conventional polyolefin separators suffer from poor wettability to liquid electrolytes (LEs). Although some modified separators exhibit improved wettability, they are hydrophilic, causing inevitable moisture uptake. Trace water could result in poor performance and safety hazard of Li metal batteries. Here, we report a design idea of superLEphilic/superhydrophobic and thermostable separators by modifying the Celgard separator using silicone nanofilaments. The separator features low moisture uptake (∼0%), fast LE diffusion (454 ms), and high LE uptake (287.8%), LE retention rate, and Li⁺ conductivity. Consequently, the Li/LiFePO₄ cells show high cycling stability (96.05% after 350 cycles), good rate performance (125 mA h g⁻¹ at 5.0 C), low resistance, and stable open circuit voltage at 160°C. Moreover, the separator could improve performance of the other Li metal batteries with high-voltage cathodes and the LiFePO₄/graphite pouch cells. This work provides an avenue for designing advanced separators by using bioinspired superwetting surfaces.

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A superLEphilic/superhydrophobic separator is first reported for Li metal batteries

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The separator has low moisture uptake and could improve performance of Li/Li cells

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The separator features fast LE diffusion, high LE uptake, and Li⁺ conductivity

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The separator could enhance performance of high-voltage Li metal batteries

Constructing Effective Interfaces for Li1.5Al0.5Ge1.5(PO4)3 Pellets To Achieve Room-Temperature Hybrid Solid-State Lithium Metal Batteries

Solid electrolytes are considered as strong alternatives for conventional liquid electrolytes to overcome the safety issues of next-generation high-energy-density lithium metal batteries (LMBs). Although Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) has satisfied ionic conductivity at room temperature (∼10^-4 S cm^-1), high stability in air, and can be easily sintered, it still suffers from instability of the lithium metal. Moreover, the large interfacial resistance between solid electrolytes and solid electrodes and the stress generated by the volumetric change of lithium metal anodes during cycling would deteriorate the performance of LMBs. Here, we report an effective solution to overcome the abovementioned problems by introducing a three-dimensional gel polymer electrolyte at the interface between LAGP pellets and lithium metal anodes, achieving stable cycling of LiFePO₄//Li cells at room temperature for 300 cycles. Besides, the degeneration mechanisms of the interfaces of LAGP pellets under different conditions are compared, and peculiar properties different from their counterparts were found.