High-strength and flexible cellulose/PEG based gel polymer electrolyte with high performance for lithium ion batteries

Recent Progress in Cellulose-Based Conductive Hydrogels

Cellulose, a widely abundant natural polymer, is well recognized for its remarkable properties, such as biocompatibility, degradability, and mechanical strength. Conductive hydrogels, with their unique ability to conduct electricity, have attracted significant attention in various fields. The combination of cellulose and conductive hydrogels has led to the emergence of cellulose-based conductive hydrogels, which show great potential in flexible electronics, biomedicine, and energy storage. This review article comprehensively presents the latest progress in cellulose-based conductive hydrogels. Firstly, it provides an in-depth overview of cellulose, covering aspects like its structure, diverse sources, and classification. This emphasizes cellulose's role as a renewable and versatile material. The development and applications of different forms of cellulose, including delignified wood, bacterial cellulose, nanocellulose, and modified cellulose, are elaborated. Subsequently, cellulose-based hydrogels are introduced, with a focus on their network structures, such as single-network, interpenetrating network, and semi-interpenetrating network. The construction of cellulose-based conductive hydrogels is then discussed in detail. This includes their conductive forms, which are classified into electronic and ionic conductive hydrogels, and key performance requirements, such as cost-effectiveness, mechanical property regulation, sensitive response to environmental stimuli, self-healing ability, stable conductivity, and multifunctionality. The applications of cellulose-based conductive hydrogels in multiple areas are also presented. In wearable sensors, they can effectively monitor human physiological signals in real time. In intelligent biomedicine, they contribute to wound healing, tissue engineering, and nerve regeneration. In flexible supercapacitors, they offer potential for green and sustainable energy storage. In gel electrolytes for conventional batteries, they help address critical issues like lithium dendrite growth. Despite the significant progress, there are still challenges to overcome. These include enhancing the multifunctionality and intelligence of cellulose-based conductive hydrogels, strengthening their connection with artificial intelligence, and achieving simple, green, and intelligent large-scale industrial production. Future research directions should center around exploring new synthesis methods, optimizing material properties, and expanding applications in emerging fields, aiming to promote the widespread commercialization of these materials.

Anisotropic Conductivity and Mechanical Strength Enhancements in Gel Polymer Electrolyte Films by Hot Pressing

Gel polymer electrolyte (GPE) with a polymer matrix swollen in liquid electrolytes offers several advantages over conventional liquid electrolytes, including no leakage, lightweight properties, and high reliability. While poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based GPEs show promise for lithium-ion batteries, their practical application is hindered by the intrinsic trade-off between ionic conductivity and mechanical robustness in conventional PVDF systems. Typical strategies relying on excessive plasticizers (e.g., ionic liquids) compromise mechanical integrity. Here, we propose a novel hot-pressing-induced recrystallization strategy to synergistically enhance both anisotropic ionic conductivity and puncture strength in PVDF-based GPE films. By blending PVDF with controlled amounts of 1-hexyl-3-methylimidazolium chloride ([HMIM]Cl), followed by solution casting and hot pressing, we achieve microstructural reorganization that dramatically improves through-thickness ion transport and mechanical performance. Crucially, hot-pressed PVDF with only 25 wt% [HMIM]Cl exhibits a 12.5-fold increase in ionic conductivity (reaching 4.7 × 10-4 S/cm) compared to its solution-cast counterparts. Remarkably, this formulation surpasses the conductivity of PVDF-HFP composites with a higher [HMIM]Cl content (35 wt%, 1.7 × 10-4 S/cm), demonstrating performance optimization of anisotropic conductivity. What is more, the mechanical strength of the piercing strength perpendicular to the GPE film after hot pressing increased by 42% compared to the solution-cast film. This work establishes a scalable processing route to break the conductivity-strength dichotomy in GPEs, offering critical insights for designing high-performance polymer electrolytes.

Quasi-Solid Gel Electrolytes for Alkali Metal Battery Applications

Alkali metal batteries (AMBs) have undergone substantial development in portable devices due to their high energy density and durable cycle performance. However, with the rising demand for smart wearable electronic devices, a growing focus on safety and durability becomes increasingly apparent. An effective strategy to address these increased requirements involves employing the quasi-solid gel electrolytes (QSGEs). This review focuses on the application of QSGEs in AMBs, emphasizing four types of gel electrolytes and their influence on battery performance and stability. First, self-healing gels are discussed to prolong battery life and enhance safety through self-repair mechanisms. Then, flexible gels are explored for their mechanical flexibility, making them suitable for wearable devices and flexible electronics. In addition, biomimetic gels inspired by natural designs are introduced for high-performance AMBs. Furthermore, biomass materials gels are presented, derived from natural biomaterials, offering environmental friendliness and biocompatibility. Finally, the perspectives and challenges for future developments are discussed in terms of enhancing the ionic conductivity, mechanical strength, and environmental stability of novel gel materials. The review underscores the significant contributions of these QSGEs in enhancing AMBs performance, including increased lifespan, safety, and adaptability, providing new insights and directions for future research and applications in the field.

Unveiling potential of cellulose gel electrolyte: Molecular engineering for enhanced electrostatic interactions with Mg adatoms in Mg-ion battery

The Mg-ion battery faces significant limitations due to its liquid electrolyte, which suffers from inherent issues such as leakage and the growth of Mg dendrites. In contrast, gel polymer electrolytes (GPEs) offer heightened safety, a wide voltage window, and excellent flexibility, making them a promising alternative with outstanding electrochemical performance. In this study, a cyano-modified cellulose (CEC) GPE was engineered to aim at enhancing ion transportation and promoting uniform ion-flux through interactions between N and Mg2+ ions. The resulting CEC-based GPE demonstrated a high ionic conductivity of 1.73 mS cm-1 at room temperature. Furthermore, it exhibited remarkable Mg plating/stripping performance (coulombic efficiency ∼96.7 %) and compatibility with electrodes. Importantly, when employed in a Mo6S8//Mg battery configuration, the CEC GPE displayed exceptional cycle stability, with virtually no degradation observed even after 650 cycles at 1C, thereby significantly advancing Mg-ion battery technology due to its excellent electrochemical properties. This study provides valuable insights into the molecular engineering of cellulose-based GPEs.

Cathode|Electrolyte Interface Engineering by a Hydrogel Polymer Electrolyte for a 3D Porous High-Voltage Cathode Material in a Quasi-Solid-State Zinc Metal Battery by In Situ Polymerization

This work highlights the development of a superior cathode|electrolyte interface for the quasi solid-state rechargeable zinc metal battery (QSS-RZMB) by a novel hydrogel polymer electrolyte using an ultraviolet (UV) light-assisted in situ polymerization strategy. By integrating the cathode with a thin layer of the hydrogel polymer electrolyte, this technique produces an integrated interface that ensures quick Zn2+ ion conduction. The coexistence of nanowires for direct electron routes and the enhanced electrolyte ion infiltration and diffusion by the 3D porous flower structure with a wide open surface of the Zn-MnO electrode complements the interface formation during the in situ polymerization process. The QSS-RZMB configured with an integrated cathode (i-Zn-MnO) and the hydrogel polymer electrolyte (PHPZ-30) as the separator yields a comparable specific energy density of 214.14 Wh kg-1 with that of its liquid counterpart (240.38 Wh kg-1, 0.5 M Zn(CF3SO3)2 aqueous electrolyte). Other noteworthy features of the presented QSS-RZMB system include its superior cycle life of over 1000 charge-discharge cycles and 85% capacity retention with 99% coulombic efficiency at the current density of 1.0 A g-1, compared to only 60% capacity retention over 500 charge-discharge cycles displayed by the liquid-state system under the same operating conditions.

Recent Advancements in Gel Polymer Electrolytes for Flexible Energy Storage Applications

Since the last decade, the need for deformable electronics exponentially increased, requiring adaptive energy storage systems, especially batteries and supercapacitors. Thus, the conception and elaboration of new deformable electrolytes becomes more crucial than ever. Among diverse materials, gel polymer electrolytes (hydrogels, organogels, and ionogels) remain the most studied thanks to the ability to tune the physicochemical and mechanical properties by changing the nature of the precursors, the type of interactions, and the formulation. Nevertheless, the exploitation of this category of electrolyte as a possible commercial product is still restrained, due to different issues related to the nature of the gels (ionic conductivity, evaporation of filling solvent, toxicity, etc.). Therefore, this review aims to resume different strategies to tailor the properties of the gel polymer electrolytes as well as to provide recent advancements in the field toward the elaboration of deformable batteries and supercapacitors.

A Comprehensive Review of Functional Gel Polymer Electrolytes and Applications in Lithium-Ion Battery

The rapid expansion of flexible and wearable electronics has necessitated a focus on ensuring their safety and operational reliability. Gel polymer electrolytes (GPEs) have become preferred alternatives to traditional liquid electrolytes, offering enhanced safety features and adaptability to the design requirements of flexible lithium-ion batteries. This review provides a comprehensive and critical overview of recent advancements in GPE technology, highlighting significant improvements in its physicochemical properties, which contribute to superior long-term cycling stability and high-rate capacity compared with traditional organic liquid electrolytes. Special attention is given to the development of smart GPEs endowed with advanced functionalities such as self-protection, thermotolerance, and self-healing properties, which further enhance battery safety and reliability. This review also critically examines the application of GPEs in high-energy cathode materials, including lithium nickel cobalt manganese (NCM), lithium nickel cobalt aluminum (NCA), and thermally stable lithium iron phosphate (LiFePO4). Despite the advancements, several challenges in GPE development remain unresolved, such as improving ionic conductivity at low temperatures and ensuring mechanical integrity and interfacial compatibility. This review concludes by outlining future research directions and the remaining technical hurdles, providing valuable insights to guide ongoing and future efforts in the field of GPEs for lithium-ion batteries, with a particular emphasis on applications in high-energy and thermally stable cathodes.

Green Polymer Electrolytes Prepared by a Cost-Effective Approach

The preparation of solid polymer electrolytes (SPEs) using poly(ethylene oxide) (PEO) typically involves incorporating fillers or undergoing chemical modifications to reduce crystallinity and enhance conductivity. PEO with a lower molecular weight, known as polyethylene glycol (PEG), exhibits higher conductivity, despite weaker mechanical strength. It is commonly employed as a plasticizer to improve the conductivity of SPEs or to fabricate PEG-based gel polymer electrolytes (GPEs). In this study, we use a straightforward approach to create innovative SPEs by blending liquid polymer electrolytes (LPEs), particularly low-molecular-weight polyethylene glycol (PEG), with a molecular weight of 400 g/mol, and sustainable poly(l-lactide) (PLLA). Solid PEG/PLLA forms are achieved by introducing 30 wt % of PLLA. Subsequently, the addition of lithium salts results in the development of novel PEG/PLLA SPEs. Another focal point of this study involves incorporating 1,3:2,4-dibenzylidene sorbitol (DBS) into these PEG/PLLA systems. DBS, an organic gelator derived from natural sugars, demonstrates self-assembly, leading to the formation of a nanofibrillar network structure. Leveraging DBS's ability to form organogels in liquid organic environments, we facilitate the transformation of low PLLA content LPEs into innovative solvent-free GPEs. Our prepared PEG/PLLA SPEs exhibited a maximum conductivity value of 4.39 × 10-5 S/cm, approximately five times higher than that of neat PEG (10000 g/mol) SPEs. The ionic conductivity exhibited a declining trend as the content of PLLA and DBS increased. However, there was an improvement in electrochemical stability. Furthermore, the incorporation of PLLA and DBS into electrolytes contributed to enhanced mechanical support and stability within the electrolyte layer. This, in turn, mitigated capacity decay and improved the cycling performance of assembled lithium-ion cells.

Cellulose-Based Ionic Conductor: An Emerging Material toward Sustainable Devices

Ionic conductors (ICs) find widespread applications across different fields, such as smart electronic, ionotronic, sensor, biomedical, and energy harvesting/storage devices, and largely determine the function and performance of these devices. In the pursuit of developing ICs required for better performing and sustainable devices, cellulose appears as an attractive and promising building block due to its high abundance, renewability, striking mechanical strength, and other functional features. In this review, we provide a comprehensive summary regarding ICs fabricated from cellulose and cellulose-derived materials in terms of fundamental structural features of cellulose, the materials design and fabrication techniques for engineering, main properties and characterization, and diverse applications. Next, the potential of cellulose-based ICs to relieve the increasing concern about electronic waste within the frame of circularity and environmental sustainability and the future directions to be explored for advancing this field are discussed. Overall, we hope this review can provide a comprehensive summary and unique perspectives on the design and application of advanced cellulose-based ICs and thereby encourage the utilization of cellulosic materials toward sustainable devices.

Efficient Biorenewable Membranes in Lithium-Oxygen Batteries

Lithium-oxygen batteries, with their very high energy density (3500 Wh kg-1), could represent a real breakthrough in the envisioned strategies towards more efficient energy storage solutions for a less and less carbonated energy mix. However, the problems associated with this technology are numerous. A first one is linked to the high reactivity of the lithium metal anode, while a second one is linked to the highly oxidative environment created by the cell's O2 saturation. Keeping in mind the necessity for greener materials in future energy storage solutions, in this work an innovative lithium protective membrane is prepared based on chitosan, a polysaccharide obtained from the deacetylation reaction of chitin. Chitosan was methacrylated through a simple, one-step reaction in water and then cross-linked by UV-induced radical polymerization. The obtained membranes were successively activated in liquid electrolyte and used as a lithium protection layer. The cells prepared with protected lithium were able to reach a higher full discharge capacity, and the chitosan's ability to slow down degradation processes was verified by post-mortem analyses. Moreover, in long cycling conditions, the protected lithium cell performed more than 40 cycles at 0.1 mA cm-2, at a fixed capacity of 0.5 mAh cm-2, retaining 100% coulombic efficiency, which is more than twice the lifespan of the bare lithium cell.

Effect of the Poly(ethylene glycol) Diacrylate (PEGDA) Molecular Weight on Ionic Conductivities in Solvent-Free Photo-Cross-Linked Solid Polymer Electrolytes

To obtain safe, high-performance Li-ion batteries, the development of electrolytes with high impact resistance and high ionic conductivity is important. Ionic conductivity at room temperature has been improved by using poly(ethylene glycol) (PEG) diacrylate (PEGDA) to form three-dimensional (3D) networks and solvated ionic liquids. However, the effects of the molecular weight of PEGDA on ionic conductivities and the relationship between ionic conductivities and network structures of cross-linked polymer electrolytes have not been discussed in detail. In this study, the dependence of the ionic conductivity of photo-cross-linked PEG solid electrolytes on the molecular weight of the PEGDA was evaluated. X-ray scattering (XRS) gave detailed information about the dimensions of 3D networks formed by the photo-cross-linking of PEGDA, and the effects of the network structures on the ionic conductivities were discussed.

Anticorrosion and Antimicrobial Evaluation of Sol-Gel Hybrid Coatings Containing Clitoria ternatea Modified Clay

In this study, Clitoria ternatea (CT) was incorporated into the structure of sodium montmorillonite (Na⁺-MMT), then these new nanoparticles (CT-MMT) were added to sol-gel-based hybrid silanol coatings (SGC). The results of the CT-MMT investigation using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM) confirmed the presence of CT in the structure. The results of polarization and electrochemical impedance spectroscopy (EIS) tests showed that the presence of CT-MMT in the matrix improves corrosion resistance. The EIS results showed that the coating resistance (R_f) of the sample containing 3 wt.% CT-MMT after immersion was 687 Ω·cm², while this value was 218 Ω·cm² for pure coating. CT and MMT compounds improve corrosion resistance by blocking anodic and cathodic regions, respectively. Additionally, the presence of CT in the structure created antimicrobial properties. CT contains phenolic compounds that have the ability to suppress by membrane perturbation, reduction of host ligands adhesion, and neutralizing bacterial toxins. Therefore, CT-MMT showed inhibitory effects and killing of Staphylococcus aureus (gram-positive bacteria) and Salmonella paratyphi-A serotype (gram-negative bacteria), and also improved corrosion resistance.

An Asymmetric Cross-Linked Ionic Copolymer Hybrid Solid Electrolyte with Super Stretchability for Lithium-Ion Batteries

Composite solid electrolytes are recommended to be the most promissing strategy for solid-state batteries because they combine the advantages of inorganic ceramics and polymers. However, the huge interfacial resistance between the inorganic ceramic and polymer results in low ionic conductivity, which is still the major impediment that limits their applications. Herein, a novel highly elastic and weakly coordinated ionic copolymer hybrid electrolyte with asymmetric structure based on surface-modified Li_1.5 Al_0.5 Ge_1.5 (PO₄ )₃ by "in situ" polymerization is proposed to improve ionic conductivity and mechanical properties simultaneously. The all-solid hybrids electrolytes exhibit room-temperature ionic conductivity up to 2.61 × 10^-4 S cm^-1 and lithium-ion transference number of 0.41. The hybrids electrolytes can be repeatedly stretching-releasing-stretching, showing a super stretchability with the elongation at break up to 496%. The Li symmetrical cells assembled with the hybrid electrolytes can continuously operate for 800 h at 0.1 mA cm^-2 without discernable dendrites, indicating good interfacial compatibility between the hybrid electrolytes and lithium electrodes. The Li|LiFePO₄ batteries assembled with the hybrid electrolytes deliver an initial discharge specific capacity of 165.5 mAh g^-1 with an initial coulombic efficiency of 94.8% and 154 mAh g^-1 after 100 cycles at 0.1 C, and maintain 95.4% capacity retention after 100 cycles at 0.5 C.

Enhancement of Electrochemical Stability Window and Electrical Properties of CNT-Based PVA-PEG Polymer Blend Composites

New polymer blend composite electrolytes (PBCEs) were prepared by the solution casting technique using poly(vinyl alcohol) (PVA)-polyethylene glycol (PEG), sodium nitrate (NaNO₃) as a doping salt and multiwalled carbon nanotubes (MWCNTs) as fillers. The X-ray diffraction pattern confirms the structural properties of the polymer blend composite films. FTIR investigations were carried out to understand the chemical properties and their band assignments. The ionic conductivity of the 10 wt % MWCNTs incorporated PVA-PEG polymer blend was measured as 4.32 × 10^-6 S cm^-1 at 20 °C and increased to 2.253 × 10^-4 S/cm at 100 °C. The dependence of its conductivity on temperature suggests Arrhenius behavior. The equivalent circuit models that represent the R _s(Q₁(R₁(Q₂(R₂(CR₃))))) were used to interpret EIS data. The dielectric behavior of the samples was investigated by utilizing their AC conductance spectra, dielectric permittivity, dielectric constant (εⁱ and ε^r), electric modulus (Mⁱ and M^r), and loss tangent tan δ. The dielectric permittivity of the samples increases due to electrode polarization effects in low frequency region. The loss tangent's maxima shift with increasing temperature; hence, the peak height rises in the high frequency region. MWCNTs-based polymer blend composite electrolytes show an enhanced electrochemical stability window (4.0 V), better transference number (0.968), and improved ionic conductivity for use in energy storage device applications.

High Performance Carbon Fiber Structural Batteries Using Cellulose Nanocrystal Reinforced Polymer Electrolyte

In recent years, structural batteries have received great attention for future automotive application in which a load-bearing car panel is used as an energy storage. However, based on the current advances, achieving both high ionic conductivity and mechanical performance has remained a challenge. To address this challenge, this study introduces a cellulose nanocrystal (CNC) reinforced structural battery electrolyte (CSBE) consisting of CNC, triethylene glycol dimethyl ether (TriG) electrolyte containing a quasi-solid additive, e.g., cyclohexanedimethanol (CHDM), in a vinyl ester polymer. This green and renewable CSBE electrolyte system was in situ polymerized via reaction induced phase transition to form a high performance multidimensional channel electrolyte to be used in structural carbon fiber-based battery fabrication. The effect of various concentrations of CNC on the electrolyte ionic conductivity and mechanical properties was obtained in their relation to intermolecular interactions, interpreted by FTIR, Raman, Li NMR results. Compared to the neat SBE system, the optimized CSBE nanocomposite containing 2 wt % CNC shows a remarkable ionic conductivity of 1.1 × 10^-3 S cm^-1 at 30 °C, which reveals ∼300% improvement, alongside higher thermal stability. Based on the FTIR, Raman, Li NMR results, the content of CNC in the CSBE structure plays a crucial role not only in the formation of cellulose network skeleton but also in physical interaction with polymer matrix, providing an efficient Li⁺ pathway through the electrolyte matrix. The carbon fiber composite was fabricated by 2 wt % CNC reinforced SBE electrolyte to evaluate as a battery half-cell. The results demonstrated that by addition of 2 wt % CNC into SBE system, 7.6% and 33.9% improvements were achieved in specific capacity at 0.33 C and tensile strength, respectively, implying outstanding potential of ion conduction and mechanical load transfer between the carbon fibers and the electrolyte.

Cellulose Acetate-Based High-Electrolyte-Uptake Gel Polymer Electrolyte for Semi-Solid-State Lithium-Oxygen Battery with Long-Cycling Stability

The lithium-oxygen battery has inspired great research interests owing to its ultrahigh theoretical energy density and has been considered as one of the promising secondary batteries. However, there are still some challenges in its practical application, like liquid organic electrolyte evaporation in the semi-open system and instability in the high-voltage oxidizing environment. In this work, a cellulose acetate-based gel polymer electrolyte (CA@GPE) is proposed, whose cross-linked microporous structure ensures the ultrahigh liquid electrolyte uptake of 2391%. The prepared CA@GPE exhibits a high lithium-ion transference number of 0.595, a satisfying ionic conductivity of 0.47 mS cm -1 and a wide electrochemical stability window up to 5.0 V. The Li//Li symmetric cell employing CA@GPE could cycle stably over 1200 h. The lithium-oxygen battery with CA@GPE presents a superb cycling lifetime of 370 cycles at 0.1 mA cm -2 under 0.25 mAh cm -2 . This work offers a possible strategy to realize long-cycling stability lithium-oxygen batteries.

Scalable fabrication of Solvent-Free composite solid electrolyte by a continuous Thermal-Extrusion process

Composite solid-state electrolytes (CSEs) are regarded as a promising alternative for the next-generation lithium-ion batteries because they integrate the advantages of inorganic electrolytes and organic electrolytes. However, there are two issues faced by current CSEs: 1) a green and feasible approach to prepare CSEs in large scales is desired; and 2) the trace solvents, remaining from the preparation processes, lead to some serious concerns, such as safety hazard issues, electrolyte-electrode interfacial issues, and reduced durability of batteries. Here, a continuous thermal-extrusion process is presented to realize the large-scale fabrication of solvent-free CSE. A 38.7-meter CSE membrane was prepared as a demonstration in this study. Thanks to the elimination of residual solvents, the electrolyte membrane exhibited a high tensile strength of 3.85 MPa, satisfactory lithium transference number (0.495), and excellent electrochemical stability (5.15 V). Excellent long-term stability was demonstrated by operating the symmetric lithium cell at a stable current density of 0.1 mA cm^-2 for over 3700 h. Solvent-free CSE lithium metal batteries showed a discharge capacity of 155.7 - 25.17 mAh g^-1 at 0.1 - 2.0C, and the discharge capacity remained 78.1% after testing for 380cycles.

Substantial Proton Ion Conduction in Methylcellulose/Pectin/Ammonium Chloride Based Solid Nanocomposite Polymer Electrolytes: Effect of ZnO Nanofiller

In this research, nanocomposite solid polymer electrolytes (NCSPEs) comprising methylcellulose/pectin (MC/PC) blend as host polymer, ammonium chloride (NH₄Cl) as an ion source, and zinc oxide nanoparticles (ZnO NPs) as nanofillers were synthesized via a solution cast methodology. Techniques such as Fourier transform infrared (FTIR), electrical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) were employed to characterize the electrolyte. FTIR confirmed that the polymers, NH₄Cl salt, and ZnO nanofiller interact with one another appreciably. EIS demonstrated the feasibility of achieving a conductivity of 3.13 × 10⁻⁴ Scm⁻¹ for the optimum electrolyte at room temperature. Using the dielectric formalism technique, the dielectric properties, energy modulus, and relaxation time of NH₄Cl in MC/PC/NH₄Cl and MC/PC/NH₄Cl/ZnO systems were determined. The contribution of chain dynamics and ion mobility was acknowledged by the presence of a peak in the imaginary portion of the modulus study. The LSV measurement yielded 4.55 V for the comparatively highest conductivity NCSPE.

Enhancing ionic conductivity in solid electrolyte by relocating diffusion ions to under-coordination sites

Solid electrolytes are highly important materials for improving safety, energy density, and reversibility of electrochemical energy storage batteries. However, it is a challenge to modulate the coordination structure of conducting ions, which limits the improvement of ionic conductivity and hampers further development of practical solid electrolytes. Here, we present a skeleton-retained cationic exchange approach to produce a high-performance solid electrolyte of Li₃Zr₂Si₂PO₁₂ stemming from the NASICON-type superionic conductor of Na₃Zr₂Si₂PO₁₂. The introduced lithium ions stabilized in under-coordination structures are facilitated to pass through relatively large conduction bottlenecks inherited from the Na₃Zr₂Si₂PO₁₂ precursor. The synthesized Li₃Zr₂Si₂PO₁₂ achieves a low activation energy of 0.21 eV and a high ionic conductivity of 3.59 mS cm^-1 at room temperature. Li₃Zr₂Si₂PO₁₂ not only inherits the satisfactory air survivability from Na₃Zr₂Si₂PO₁₂ but also exhibits excellent cyclic stability and rate capability when applied to solid-state batteries. The present study opens an innovative avenue to regulate cationic occupancy and make new materials.

MOF-Enabled Ion-Regulating Gel Electrolyte for Long-Cycling Lithium Metal Batteries Under High Voltage

High-voltage lithium metal batteries (LMBs) are a promising high-energy-density energy storage system. However, their practical implementations are impeded by short lifespan due to uncontrolled lithium dendrite growth, narrow electrochemical stability window, and safety concerns of liquid electrolytes. Here, a porous composite aerogel is reported as the gel electrolyte (GE) matrix, made of metal-organic framework (MOF)@bacterial cellulose (BC), to enable long-life LMBs under high voltage. The effectiveness of suppressing dendrite growth is achieved by regulating ion deposition and facilitating ion conduction. Specifically, two hierarchical mesoporous Zr-based MOFs with different organic linkers, that is, UiO-66 and NH₂ -UiO-66, are embedded into BC aerogel skeletons. The results indicate that NH₂ -UiO-66 with anionphilic linkers is more effective in increasing the Li⁺ transference number; the intermolecular interactions between BC and NH₂ -UiO-66 markedly increase the electrochemical stability. The resulting GE shows high ionic conductivity (≈1 mS cm^-1 ), high Li⁺ transference number (0.82), wide electrochemical stability window (4.9 V), and excellent thermal stability. Incorporating this GE in a symmetrical Li cell successfully prolongs the cycle life to 1200 h. Paired with the Ni-rich LiNiCoAlO₂ (Ni: Co: Al = 8.15:1.5:0.35, NCA) cathode, the NH₂ -UiO-66@BC GE significantly improves the capacity, rate performance, and cycle stability, manifesting its feasibility to operate under high voltage.

Solvent-Free Procedure to Prepare Ion Liquid-Immobilized Gel Polymer Electrolytes Containing Li0.33La0.56TiO3 with High Performance for Lithium-Ion Batteries

Based on the advantages of intrinsic safety, flexibility, and good interfacial contact with electrodes, a gel polymer electrolyte (GPE) is a promising electrolyte for lithium-ion batteries, compared with the conventional liquid electrolyte. However, the unstable electrochemical performance and the liquid state in a microscale limit the commercial application of GPE. Herein, we developed a novel gel polymer electrolyte for lithium-ion batteries by blending methyl methacrylate (MMA), N-butyl-N-methyl-piperidinium (Pyr₁₄TFSI), and lithium salts in a solvent-free procedure, with SiO₂ and Li_0.33La_0.56TiO₃ (LLTO) additives. The prepared MMA-Pyr₁₄TFSI-3 wt % LLTO electrolyte shows the best electrochemical performance and obtains a high ion conductivity of 4.51 × 10^-3 S cm^-1 at a temperature of 60 °C. Notably, the electrochemical window could be stable up to 5.0 V vs Li⁺/Li. Moreover, the batteries with the GPE also show excellent electrochemical performance. In the LiFePO₄/MMA-Pyr₁₄TFSI-3 wt % LLTO/Li cell, a high initial discharge capacity was achieved 150 mA h g^-1 at 0.5C with a Coulombic efficiency over 99% and maintaining a good capacity retention of 90.7% after 100 cycles at 0.5C under 60 °C. In addition, the physical properties of the GPE have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) measurements, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetry (TG).

Simultaneous surface functionalization and drug loading: A novel method for fabrication of cellulose nanocrystals-based pH responsive drug delivery system

Herein, a novel strategy for surface functionalization and drug loading of cellulose nanocrystals (CNCs) through formation of hydrazone bonds between functionalized CNCs and aldehyde group containing polyethylene glycol (CHO-PEG)/anticancer drug doxorubicin (DOX) was reported for the first time. DOX could be loaded on PEGylated CNCs with high capacity and released from drug complexes (P-CNCs-D) with pH dependent behavior. The biological evaluation results demonstrated that drug carriers (CNCs-EBO-NH) showed negative cytotoxicity while DOX could be transported into cells and exhibits desirable anticancer effects. As compared with other method, the method developed in this work is rather simple and effective and can be achieved for simultaneous for surface functionalization and drug loading in a one-pot route. This work will open a new avenue for fabrication of various multifunctional composites based on other carbohydrate polymers or materials and to explore their applications in biomedical fields.

Recent Progress in High-Strength and Robust Regenerated Cellulose Materials

High-strength petroleum-based materials like plastics have been widely used in various fields, but their nonbiodegradability has caused serious pollution problems. Cellulose, as the most abundant sustainable polymer, has a great chance to act as the ideal substitute for plastics due to its low cost, wide availability, biodegradability, etc. Herein, the recent achievements for developing cellulose "green" solvents and regenerated cellulose materials with high strength via the "bottom-up" route are presented. Cellulose can be regenerated to produce films/membranes, hydrogels/aerogels, filaments/fibers, microspheres/beads, bioplastics, etc., which show potential applications in textiles, biomedicine, energy storage, packaging, etc. Importantly, these cellulose-based materials can be biodegraded in soil and oceans, reducing environmental pollution. The cellulose solvents, dissolving mechanism, and strategies for constructing the regenerated cellulose functional materials with high strength and performances, together with the current achievements and urgent challenges are summarized, and some perspectives are also proposed. The near future will be an exciting era for high-strength biodegradable and renewable materials. The hope is that many environmentally friendly materials with good properties and low cost will be produced for commercial use, which will be beneficial for sustainable development in the world.

Effects of Comonomers on the Performance of Stable Phosphonate-Based Gel Terpolymer Electrolytes for Sodium-Ion Batteries with Ultralong Cycling Stability

Gel polymer electrolyte (GPE) is one of the most promising alternatives to solve the bottlenecks of nonaqueous liquid electrolytes such as decomposition, safety hazards, and growth of dendrites. In this work, three novel methyl phosphonate-based crosslinking gel terpolymer electrolytes with different comonomers are designed and prepared by in situ radical polymerization. The gel polymer electrolytes have excellent thermal stability, wide electrochemical windows (≥4.9 V), and high ionic conductivities (±3 mS cm^-1), and may be used as less-flammable electrolytes for sodium-ion batteries. ³¹P NMR spectra, Arrhenius plot, and density functional theory (DFT) calculations confirm that multifunctional phosphonate structural units promote the dissociation of NaClO₄ and help to transport the sodium ions freely in the polymer framework. X-ray photoelectron spectroscopy (XPS) results show that the gel polymer electrolytes have the capability of inhibiting liquid electrolyte decomposition and the formation of the stable solid electrolyte interphase (SEI) film. The Na₃V₂(PO₄)₃/GPE/Na cells exhibit better ultralong cycling stability and enhanced temperature performance than those of liquid cells. Strikingly, GPE1 has the best comprehensive electrochemical performance, especially the rate performance and long-term cycling stability with a capacity retention ratio of 82.6% after 3500 cycles, which indicates that different comonomers have obvious effects on the performance. Therefore, the full cell of SnS₂/GPE1/Na₃V₂(PO₄)₃ is evaluated and delivers good cycling stability of 500 cycles, holding a great prospect for the design and production of phosphorus-containing electrolytes for safer sodium-ion batteries.

The Development of Polylactic Acid/Multi-Wall Carbon Nanotubes/Polyethylene Glycol Scaffolds for Bone Tissue Regeneration Application

Composite electrospun fibers were fabricated to develop drug loaded scaffolds to promote bone tissue regeneration. Multi-wall carbon nanotubes (MWCNTs) were incorporated to polylactic acid (PLA) to strengthen electrospun nanofibers. To modulate drug release behavior, different ratios of hydrophilic polyethylene glycol (PEG) were added to composite fibers. Glass transition temperature (Tg) can be reduced by the incorporated PEG to enhance the ductility of the nanofibers. The SEM images and the MTT results demonstrated that composite fibers are suitable scaffolds for cell adhesion and proliferation. Dexamethasone (DEX), an osteogenic inducer, was loaded to PLA/MWCNT/PEG fibers. The surface element analysis performed by XPS showed that fluorine of DEX in pristine PLA fibers was much higher than those of the MWCNT-containing fibers, suggesting that the pristine PLA fibers mainly load DEX on their surfaces, whereas MWCNTs can adsorb DEX with evenly distribution in nanofibers. Drug release experiments demonstrated that the release profiles of DEX were manipulated by the ratio of PEG, and that the more PEG in the nanofibers, the faster DEX was released. When rat bone marrow stromal cells (rBMSCs) were seeded on these nanofibers, the Alizarin Red S staining and calcium quantification results demonstrated that loaded DEX were released to promote osteogenic differentiation of rBMSCs and facilitate mineralized tissue formation. These results indicated that the DEX-loaded PLA/MWCNT/PEG nanofibers not only enhanced mechanical strength, but also promoted osteogenesis of stem cells via the continuous release of DEX. The nanofibers should be a potential scaffold for bone tissue engineering application.

Decoupling of Mechanical Strength and Ionic Conductivity in Zwitterionic Elastomer Gel Electrolyte toward Safe Batteries

Quasi-solid state electrolyte is one of the promising options for next generation batteries due to its superiority on safety and electrochemistry performance. However, the trade-off between the electrolyte swelling ratio and mechanical property of the quasi-solid state electrolyte significantly influences the battery performance. Herein, we design a nonswelling, solvent-adaptive polymer gel composed of oleophobic zwitterion poly(3-(1-vinyl-3-imidazolio)-propanesulfonate) and oleophilic elastomer poly(2-methoxyethyl acrylate) segments to retain high battery performance without sacrificing the mechanical property in lithium batteries. The as-designed gel can not only uptake enough electrolyte for a high ionic conductivity of 1.78 mS cm^-1 but also achieve excellent mechanical strength with compression stress at 90% strain (σ_0.9) reaching 5.8 MPa after long time soaking for battery safety due to its nonswelling property in ester electrolyte. Moreover, the as-prepared zwitterionic gel is beneficial to electrolyte salt dissociation, which further enhances the ionic conductivity and transference number of batteries. Consequently, the gel electrolyte can cycle for more than 500 h under a high current density of 3 mA cm^-2 on dendrite inhibition performance, and when assembled with LiFePO₄ as a cathode, the battery demonstrates a reversible specific capacity as high as 70 mAh g^-1 under a high current density of 5 C after 300 cycles. The rational designed solvophilic/solvophobic zwitterionic elastomers provide a guidance for engineering quasi-solid state electrolytes of different solvents with broad applications on flexible devices.

A Review of Experimental and Numerical Studies of Lithium Ion Battery Fires

Lithium-ion batteries (LIBs) are used extensively worldwide in a varied range of applications. However, LIBs present a considerable fire risk due to their flammable and frequently unstable components. This paper reviews experimental and numerical studies to understand parametric factors that have the greatest influence on the fire risks associated with LIBs. The LIB chemistry and the state of charge (SOC) are shown to have the greatest influence on the likelihood of a LIB transitioning into thermal runaway (TR) and releasing heats which can be cascaded to cause TR in adjacent cells. The magnitude of the heat release rate (HRR) is quantified to be used as a numerical model input parameter (source term). LIB chemistry, the SOC, and incident heat flux are proven to influence the magnitude of the HRR in all studies reviewed. Therefore, it may be conjectured that the most critical variables in addressing the overall fire safety and mitigating the probability of TR of LIBs are the chemistry and the SOC. The review of numerical modeling shows that it is quite challenging to reproduce experimental results with numerical simulations. Appropriate boundary conditions and fire properties as input parameters are required to model the onset of TR and heat transfer from thereon.

A Novel Silicon/Phosphorus Co-Flame Retardant Polymer Electrolyte for High-Safety All-Solid-State Lithium Ion Batteries

Developing a solid polymer electrolyte with superior flame retardancy and lithium-ion transportation properties is still a challenge. Herein, an intrinsic silicon/phosphorus co-flame retardant polymer solid electrolyte was prepared by using polyethylene glycol (PEG) co-polymerized with silicon and phosphorus-containing monomers. Due to the synergistic flame-retardant effect of silicon and phosphorus elements, this polymer electrolyte exhibits excellent thermal stability and flame resistance. Moreover, the ionic conductivity of the electrolyte at 25 °C is as high as 2.98 × 10-5 S/cm when the mass ratio of LiN(SO2CF3)2 (LiTFSI) and the prepared polymer electrolyte is 10:1. What is more, the LiFePO4/Li all-solid-state battery assembled with this solid electrolyte can work stably at a high temperature of 60 °C and exhibits a specific capacity of 129.2 mAh/g at 0.2 C after 100 cycles, providing a promising application prospect for high-safety lithium-ion batteries.

Textile Based Electrochromic Cells Prepared with PEDOT: PSS and Gelled Electrolyte

Electrochromic devices can act as passive displays. They change their color when a low voltage is applied. Flexible and bendable hybrid textile-film electrochromic devices with poly-3,4-ethylenedioxythiophene polystyrene sulfonate (PEDOT:PSS) were prepared on polyethylene polyethylene terephthalate (PEPES) membranes using a spray coating technique. The electrolyte consisted of a gelatin glycerol mixture as host matrix and calcium chloride. Titanium dioxide was used as an ion storage layer and a carbon containing dispersion was used for the counter electrode on a polyester rip-stop fabric. The sheet resistance of PEDOT:PSS on PEPES was 500 Ohm/sq. A 5 × 5 electrochromic matrix with individually addressable pixels was successfully designed and assembled. The switching time of the pixels was 2 s at a voltage of 2.0 V directly after assembling. The use of titanium dioxide as ion storage also increased the contrast of the dark-blue reduced electrochromic layer. Coloration was not self-sustaining. The PEDOT:PSS layer needed a constant low voltage of at least 0.5 V to sustain in the dark-blue reduced state. The switching time increased with time. After 12 months the switching time was ~4 s at a voltage of 2.8 V. The addition of glycerol into the electrolyte extended the lifetime of a non-encapsulated textile electrochromic cell, because moisture is retained in the electrolyte. Charge carriers can be transported into and out of the electrochromic layer.

A Review of Lithium-Ion Battery Fire Suppression

Lithium-ion batteries (LiBs) are a proven technology for energy storage systems, mobile electronics, power tools, aerospace, automotive and maritime applications. LiBs have attracted interest from academia and industry due to their high power and energy densities compared to other battery technologies. Despite the extensive usage of LiBs, there is a substantial fire risk associated with their use which is a concern, especially when utilised in electric vehicles, aeroplanes, and submarines. This review presents LiB hazards, techniques for mitigating risks, the suppression of LiB fires and identification of shortcomings for future improvement. Water is identified as an efficient cooling and suppressing agent and water mist is considered the most promising technique to extinguish LiB fires. In the initial stages, the present review covers some relevant information regarding the material constitution and configuration of the cell assemblies, and phenomenological evolution of the thermal runaway reactions, which in turn can potentially lead to flaming combustion of cells and battery assemblies. This is followed by short descriptions of various active fire control agents to suppress fires involving LiBs in general, and water as a superior extinguishing medium in particular. In the latter parts of the review, the phenomena associated with water mist suppression of LiB fires are comprehensively reviewed.

A flexible Cellulose/Methylcellulose gel polymer electrolyte endowing superior Li+ conducting property for lithium ion battery

With the advent of gel polymer electrolyte (GPE), a series of safety problems of lithium ion batteries have been resolved. However, poor self-standing property, the low ionic conductivity and Li⁺ transference number are still the obstacles that impede the practical application of GPE. Herein, a flexible and eco-friendly GPE is designed using allyl-modified cellulose with methylcellulose through simple UV curing. The crosslinked structure facilitates the integrity of GPE during use, and methylcellulose guarantees the high affinity to liquid electrolyte and improve interfacial compatibility. The specific polar functional groups (OH, OCH₃ and COC) in GPE cooperate to enhance the lithium salt dissociation, anion immobilization and lithium ion transporting and enable the high Li⁺ transference number (0.902) and ion conductivity (4.36 × 10^-3 S cm^-1). The assembled Li/GPE/LiFePO₄ coin cells possess high initial discharge capacity of 150.6 mA h g^-1 and a high capacity retention of 91.6 % after 100 cycles.