From Nature to Energy Storage: A Novel Sustainable 3D Cross-Linked Chitosan-PEGGE-Based Gel Polymer Electrolyte with Excellent Lithium-Ion Transport Properties for Lithium Batteries

Toward Sustainable Polymer Materials for Rechargeable Batteries: Utilizing Natural Feedstocks and Recycling/Upcycling of Polymer Waste

The ever-increasing demand for rechargeable battery systems in the era of electric vehicles has spurred extensive research into developing polymeric components for batteries, such as separators, polymer electrolytes, and binders. However, current battery systems rely on expensive and nonrenewable resources, which potentially have a negative environmental impact. Therefore, polymer materials derived from natural resources have gained significant attention, primarily due to their cost-effective and environmentally sustainable features. Moreover, natural feedstocks often possess highly polar functional groups and high molecular weights, offering desirable electro-chemo-mechanical features when applied as battery materials. More recently, various recycling and upcycling strategies for polymeric battery components have also been proposed given the substantial waste generation from end-of-life batteries. Recycling polymeric materials includes an overall process of recovering the components from spent batteries followed by regeneration into new materials. Polymer upcycling into battery materials involves transforming daily-used plastic waste into high-value-added battery components. This review aims to give a state-of-the-art overview of contemporary methods to develop sustainable polymeric materials and recycling/upcycling strategies for various battery applications.

An In Situ Polymerization Gel Polymer Electrolyte Based on Pentaerythritol Tetracrylate for High-Performance Lithium-Ion Batteries

Problems occur frequently during the application of traditional liquid electrolyte batteries, such as fluid leakage and low energy density. As a product of liquid electrolyte transition to solid electrolyte, gel polymer electrolyte has its own advantages for achieving high conductivity and good thermal stability. In this study, pentaerythritol tetracrylate (PETEA) was used as the precursor to prepare polymer-based materials with the assistance of azobis(isobutyronitrile) (AIBN) as the initiator. Because fluorine is beneficial to improving the migration efficiency of Li+ and the electrochemical performance of the gel polymer electrolyte, dodecafluoroheptyl methacrylate (DFHMA) is introduced to the PETEA-based gel polymer electrolyte (GPE) system. The DFHMA-introduced GPE shows better electrochemical performance, battery cycle performance, conductivity, and lithium-ion migration number compared with the pristine PETEA-based GPE. In particular, the DFHMA-introduced GPE exhibits the best performance because the molar ratio of PETEA to DFHMA is 5:1. Herein, the electrochemical window is 4.6 V, the ionic conductivity reaches 1.207 mS cm-1, and the number of lithium-ion migrations reaches the value of 0.663. Because the electric current density is 2 C, the specific capacity of LiNi0.5Co0.2Mn0.3O2 (NCM523)/GPE/Li reaches 143.1 mAh g-1 after 100 cycles.

Chitosan-based gel polymer electrolytes for high performance Li-ion battery

This study explores the use of glutaraldehyde-crosslinked chitosan-based gel polymer electrolytes (GPEs) in lithium-ion batteries (LIBs). GPEs are prepared by solution casting using two different molecular weights of chitosan including 150 kDa as medium and 400 kDa as high molecular weight (MMWCS and HMWCS, respectively) with varying amounts of crosslinker. Degree of crystallinity was 25.9 and 24.1 % for HMWCS and MMWCS, respectively that was decreased to 18.3 and 22.7 % by using 5 % crosslinker and 17.8 and 21.1 % by using 10 % crosslinker, and 17.2 and 17.6 % by using 20 % crosslinker. The obtained ionic conductivity for HMWCS and MMWCS was 3.1 × 10-3 and 2.9 × 10-3 S.cm-1. After crosslinking by 5, 10, and 20 % crosslinker, the ionic conductivity was obtained to 0.9 × 10-3 and 0.3 × 10-3 S.cm-1, 6.3 × 10-3 and 5 × 10-3 S.cm-1, and 1.1 × 10-3 and 0.5 × 10-3 S.cm-1 for high and medium molecular weight, respectively. Lithium-ion transfer number was obtained between 0.34 and 0.83 and the highest t+ value was obtained for the MMWCS-GA10. Electrochemical stability window of the prepared polymer electrolytes was >5 V and samples showed no remarkable dendrite growth after cycling analyses. The symmetric cells demonstrated reliable performance, operating for over 300 h without any short-circuiting, which indicates excellent reversible cycling stability for chitosan-based lithium-ion batteries. Furthermore, the Gr/GPE cell exhibited very low voltage polarization, with the over-potential decreasing from 10 mV initially to 6 mV after 300 h at the same current density. Discharge capacity was obtained higher than 170 mAh/g at 0.2C with CE = 97 % for both HMWCS-GA20 and HMWCS-GA20.

Chitosan nanofiber paper used as separator for high performance and sustainable lithium-ion batteries

Separators are indispensable components in lithium-ion batteries (LIBs), providing efficient pathways for lithium ions to travel and isolating the positive and negative electrodes to avoid short circuits. However, traditional polyolefin-based separators exhibit inferior electrolyte affinities, limited porosities, and low thermal stabilities. In this study, a novel method was developed to prepare chitosan micro/nanofiber membranes as LIB separators using natural materials. The pore sizes of the chitosan micro/nanofibers separators were modulated by changing the diameters of the chitosan fibers. The results demonstrated that the chitosan nanofiber separators (CSNFs) had superior electrolyte uptake (281 %), excellent thermal dimensional stability, and electrochemical performance in LiFePO4/Li half-cell, as indicated by the higher discharge capacity after 100 cycles, and higher rate capacity than commercial Celgard2325 separator. This study paves the way for the fabrication of eco-efficient and environment-friendly separators for high-performance LIBs.

MoS2 nanoflower decorated bio-derived chitosan nanocomposites for sustainable energy storage: Structural, optical and electrochemical studies

Bio-derived chitosan-molybdenum di sulfide (Cs-MoS2) nanocomposites are prepared by a simple and economical aqueous casting method with varying concentrations of MoS2. The structural, surface morphological, optical, and electrochemical properties of the nanocomposites were studied. FTIR analysis reveals the strong interaction between Cs and MoS2. FESEM micrograph showed an increment of the surface roughness due to the incorporation of MoS2 layers into Cs. The surface wettability of the nanocomposites was found to be decreased from 73° to 33° due to the incorporation of MoS2 into the chitosan. UV-vis spectroscopy study demonstrates a reduction of optical bandgap from 4.29 to 3.44 eV as the nanofiller, MoS2, introduces localized states within the forbidden energy bandgap. The incorporation of MoS2 was found to increase the specific capacitance of Cs from 421 mFg-1 to 1589 mFg-1 at a current density of 100 μAg-1. The EIS analysis revealed an increase in the pseudo-capacitance from 0.09 μF to 4.13 μF and a reduction of charge transfer resistance that comes from the nanofiller contribution. MoS2 nanoflower introduces more active sites and expands the electroactive zone, thus improving the charge storage property of Cs. The Cs-MoS2 may offer a new route for the synthesis of eco-friendly, biodegradable, and electrical storage devices.

3D Porous VOx/N-Doped Carbon Nanosheet Hybrids Derived from Cross-Linked Dicyandiamide-Chitosan Hydrogels for Superior Supercapacitor Electrode Materials

Three-dimensional porous carbon materials with moderate heteroatom-doping have been extensively investigated as promising electrode materials for energy storage. In this study, we fabricated a 3D cross-linked chitosan-dicyandiamide-VOSO4 hydrogel using a polymerization process. After pyrolysis at high temperature, 3D porous VOx/N-doped carbon nanosheet hybrids (3D VNCN) were obtained. The unique 3D porous skeleton, abundant doping elements, and presence of VOx 3D VNCN pyrolyzed at 800 °C (3D VNCN-800) ensured excellent electrochemical performance. The 3D VNCN-800 electrode exhibits a maximum specific capacitance of 408.1 F·g-1 at 1 A·g-1 current density and an admirable cycling stability with 96.8% capacitance retention after 5000 cycles. Moreover, an assembled symmetrical supercapacitor based on the 3D VNCN-800 electrode delivers a maximum energy density of 15.6 Wh·Kg-1 at a power density of 600 W·Kg-1. Our study demonstrates a potential guideline for the fabrication of porous carbon materials with 3D structure and abundant heteroatom-doping.

A Review of the Relationship between Gel Polymer Electrolytes and Solid Electrolyte Interfaces in Lithium Metal Batteries

Lithium metal batteries (LMBs) are a dazzling star in electrochemical energy storage thanks to their high energy density and low redox potential. However, LMBs have a deadly lithium dendrite problem. Among the various methods for inhibiting lithium dendrites, gel polymer electrolytes (GPEs) possess the advantages of good interfacial compatibility, similar ionic conductivity to liquid electrolytes, and better interfacial tension. In recent years, there have been many reviews of GPEs, but few papers discussed the relationship between GPEs and solid electrolyte interfaces (SEIs). In this review, the mechanisms and advantages of GPEs in inhibiting lithium dendrites are first reviewed. Then, the relationship between GPEs and SEIs is examined. In addition, the effects of GPE preparation methods, plasticizer selections, polymer substrates, and additives on the SEI layer are summarized. Finally, the challenges of using GPEs and SEIs in dendrite suppression are listed and a perspective on GPEs and SEIs is considered.

Renewable Biopolymers Combined with Ionic Liquids for the Next Generation of Supercapacitor Materials

The search for biocompatible and renewable materials for the next generation of energy devices has led to increasing interest in using biopolymers as a matrix component for the development of electric double-layer capacitors (EDLCs). However, using biopolymers as host matrices presents limitations in performance and scalability. At the same time, ionic liquids (ILs) have shown exceptional properties as non-aqueous electrolytes. This review intends to highlight the progress in integrating ILs and biopolymers for EDLC. While ILs have been used as solvents to process biopolymers and electrolyte materials, biopolymers have been utilized to provide novel chemistries of electrolyte materials via one of the following scenarios: (1) acting as host polymeric matrices for IL-support, (2) performing as polymeric fillers, and (3) serving as backbone polymer substrates for synthetic polymer grafting. Each of these scenarios is discussed in detail and supported with several examples. The use of biopolymers as electrode materials is another topic covered in this review, where biopolymers are used as a source of carbon or as a flexible support for conductive materials. This review also highlights current challenges in materials development, including improvements in robustness and conductivity, and proper dispersion and compatibility of biopolymeric and synthetic polymeric matrices for proper interface bonding.

A Self-Healing Gel Polymer Electrolyte, Based on a Macromolecule Cross-Linked Chitosan for Flexible Supercapacitors

Gel polymer electrolytes with a satisfied ionic conductivity have attracted interest in flexible energy storage technologies, such as supercapacitors and rechargeable batteries. However, the poor mechanical strength inhibits its widespread application. One of the most significant ways to avoid the drawbacks of the gel polymer electrolytes without compromising their ion transportation capabilities is to create a self-healing structure with the cross-linking segment. Herein, a new kind of macromolecule chemical cross-linked network ionic gel polymer electrolyte (MCIGPE) with superior electrochemical characteristics, a high flexibility, and an excellent self-healing ability were designed, based on chitosan and dibenzaldehyde-terminated poly (ethylene glycol) (PEGDA) via dynamic imine bonds. The ionic conductivity of the MCIGPE-65 can achieve 2.75 × 10^-2 S cm^-1. A symmetric all-solid-state supercapacitor employing carbon cloth as current collectors, activated a carbon film as electrodes, and MCIGPE-65 as a gel polymer electrolyte exhibits a high specific capacitance of 51.1 F g^-1 at 1 A g^-1, and the energy density of 7.1 Wh kg^-1 at a power density of 500.2 W kg^-1. This research proves the enormous potential of incorporating, environmentally and economically, chitosan into gel polymer electrolytes for supercapacitors.

A PEGylated Chitosan as Gel Polymer Electrolyte for Lithium Ion Batteries

Due to their safety and sustainability, polysaccharides such as cellulose and chitosan have great potential to be the matrix of gel polymer electrolytes (GPE) for lithium-based batteries. However, they easily form hydrogels due to the large numbers of hydrophilic hydroxyl or amino functional groups within their macromolecules. Therefore, a polysaccharide-based amphiphilic gel, or organogel, is urgently necessary to satisfy the anhydrous requirement of lithium ion batteries. In this study, a PEGylated chitosan was initially designed using a chemical grafting method to make an GPE for lithium ion batteries. The significantly improved affinity of PEGylated chitosan to organic liquid electrolyte makes chitosan as a GPE for lithium ion batteries possible. A reasonable ionic conductivity (1.12 × 10-3 S cm-1) and high lithium ion transport number (0.816) at room temperature were obtained by replacing commercial battery separator with PEG-grafted chitosan gel film. The assembled Li/GPE/LiFePO4 coin cell also displayed a high initial discharge capacity of 150.8 mA h g-1. The PEGylated chitosan-based GPE exhibits great potential in the field of energy storage.

Gel Electrolyte for Li Metal Battery

The pursuit of high energy density enables lithium metal batteries (LMBs) to become the research hotpot again. However, the safety concerns including easy leakage and inflammability of the liquid electrolyte and the performance deterioration due to the uncontrollable Li dendrites growth in liquid electrolyte limit the further development of LMBs. Gel electrolyte, the most promising alternative for the commercial liquid electrolyte, is expected to solve the dilemma faced by the liquid electrolyte because of its higher safety, good flexibility and adaptability to the electrode and high ionic conductivity comparable to that of liquid electrolyte. Deeply understanding the characteristics and the role of the gel electrolyte in LMBs is of great importance to achieve superior electrochemical performance of LMBs. In this review, we comprehensively introduce the chemical fundamental of the gel electrolyte. On this basis, the modification strategies and the recent progress of the gel electrolyte for LMBs are systematically reviewed and particularly highlighted, which are categorized based on composition regulation, structural design and functional design. We endeavor to provide guidance for the rational design of the gel electrolyte with superior properties for LMBs.

Two-Dimensional Zeolitic Imidazolate Framework ZIF-L: A Promising Catalyst for Polymerization

Here, for the first time, a 2D and leaf-like zeolitic imidazolate framework (ZIF-L) is reported for the synthesis of ultrahigh molecular weight (UHMW) poly(methyl methacrylate) (PMMA) with Mn up to 1390 kg mol−1. This synthesis method is a one-step process without any co-catalyst in a solvent-free medium. SEM, PXRD, FT-IR, TGA, and nitrogen sorption measurements confirmed the 2D and leaf-like structure of ZIF-L. The results of PXRD, SEM, TGA demonstrate that the catalyst ZIF-L is remarkably stable even after a long-time polymerization reaction. Zwitterionic Lewis pair polymerization (LPP) has been proposed for the catalytic performance of ZIF-L on methyl methacrylate (MMA) polymerization. This MMA polymerization is consistent with a living system, where ZIF-L could reinitiate the polymerization and propagates the process by gradually growing the polymer chains.

Sustainable Natural Bio-Origin Materials for Future Flexible Devices

Flexible devices serve as important intelligent interfaces in various applications involving health monitoring, biomedical therapies, and human-machine interfacing. To address the concern of electronic waste caused by the increasing usage of electronic devices based on synthetic polymers, bio-origin materials that possess environmental benignity as well as sustainability offer new opportunities for constructing flexible electronic devices with higher safety and environmental adaptivity. Herein, the bio-source and unique molecular structures of various types of natural bio-origin materials are briefly introduced. Their properties and processing technologies are systematically summarized. Then, the recent progress of these materials for constructing emerging intelligent flexible electronic devices including energy harvesters, energy storage devices, and sensors are introduced. Furthermore, the applications of these flexible electronic devices including biomedical implants, artificial e-skin, and environmental monitoring are summarized. Finally, future challenges and prospects for developing high-performance bio-origin material-based flexible devices are discussed. This review aims to provide a comprehensive and systematic summary of the latest advances in the natural bio-origin material-based flexible devices, which is expected to offer inspirations for exploitation of green flexible electronics, bridging the gap in future human-machine-environment interactions.

Quasi-Ionic Liquid Enabling Single-Phase Poly(vinylidene fluoride)-Based Polymer Electrolytes for Solid-State LiNi0.6 Co0.2 Mn0.2 O2 ||Li Batteries with Rigid-Flexible Coupling Interphase

Poly(vinylidene fluoride)-based polymer electrolytes are being intensely investigated for solid-state lithium metal batteries. However, phase separation and porous structures are still pronounced issues in traditional preparing procedure. Herein, a bottom-to-up strategy is employed to design single-phase and densified polymer electrolytes via incorporating quasi-ionic liquid with poly(vinylidene fluoride-co-hexafluoropropylene). Due to strong ion/dipole-dipole interaction, the optimized polymer electrolyte delivers high room-temperature ionic conductivity of 1.55 × 10^-3 S cm^-1 , superior thermal and oxidation stability of 4.97 V, excellent stretchability of over 1500% and toughness of 43 MJ cm^-3 as well as desirable self-extinguishing ability. Furthermore, the superb compatibility toward Li anode enables over 3000 h cycling of Li plating/stripping and ≈98% Coulombic efficiency in Li||Cu test at 0.1 mA cm^-2 . In particular, lithium metal battery Li||LiNi_0.6 Co_0.2 Mn_0.2 O₂ exhibits a room-temperature discharge retention rate of 96% after 500 cycles under a rate of 0.1 C, which is associated with the rigid-flexible coupling electrodes/electrolytes interphase. This investigation demonstrates the potential application of quasi-ionic liquid/polymer electrolytes in safe lithium metal batteries.

A comprehensive survey upon diverse and prolific applications of chitosan-based catalytic systems in one-pot multi-component synthesis of heterocyclic rings

Heterocyclic compounds are among the most prestigious and valuable chemical molecules with diverse and magnificent applications in various sciences. Due to the remarkable and numerous properties of the heterocyclic frameworks, the development of efficient and convenient synthetic methods for the preparation of such outstanding compounds is of great importance. Undoubtedly, catalysis has a conspicuous role in modern chemical synthesis and green chemistry. Therefore, when designing a chemical reaction, choosing and or preparing powerful and environmentally benign simple catalysts or complicated catalytic systems for an acceleration of the chemical reaction is a pivotal part of work for synthetic chemists. Chitosan, as a biocompatible and biodegradable pseudo-natural polysaccharide is one of the excellent choices for the preparation of suitable catalytic systems due to its unique properties. In this review paper, every effort has been made to cover all research articles in the field of one-pot synthesis of heterocyclic frameworks in the presence of chitosan-based catalytic systems, which were published roughly by the first quarter of 2020. It is hoped that this review paper can be a little help to synthetic scientists, methodologists, and catalyst designers, both on the laboratory and industrial scales.

Cathode/gel polymer electrolyte integration design based on continuous composition and preparation technique for high performance lithium ion batteries

Gel polymer electrolytes (GPEs) combine the high ionic conductivity of liquid electrolytes and good safety assurance of solid electrolytes. However, the poor interfacial contact between electrode materials and electrolyte is still a big obstacle to the high performance of solid-state batteries. Herein, an integrated cathode/GPE based on continuous composition and preparation technic is obtained by simple UV curing. The improved interfacial contact between cathode and GPE helps to facilitate the fast ions transfer at the interface. Compared with cells assembled with separated cathode and GPE, the cells with integrated cathode-GPE showed much lower interfacial impedance, lower potential polarization and more stable cycling property. This work provided a low-cost natural material gelatin and a simple UV irradiation method to prepare an integrated cathode and gel polymer electrolyte for solid-state lithium batteries. The capacity retention of the cells assembled from integrated structure was 91.4% which was much higher than that of the non-integrated cells (80.9%) after 200 cycles.

Preparation of ionogel-bonded mesoporous silica and its application in liquid chromatography

A new preparation strategy for stable ionogels on silica obtained by a chemical bonding method and its application in LC.

Fast-Charging Lithium-Sulfur Batteries Enabled via Lean Binder Content

Next-generation energy storage devices such as lithium-sulfur batteries (LSBs) face several challenges including fast charging and high-power delivery. Thus, it is necessary to improve the stability of the electrodes with efficient electrochemical system. In this work, a durable sulfur cathode even at high rates is enabled via lean binder content. The binder consists of a chitosan cross-linked with a carboxylated nitrile-butadiene rubber (XNBR), which exhibits high affinity toward lithium polysulfide along with robust mechanical properties because of the synergistic effect of the polar chitosan and the elastomeric XNBR. Despite using extremely small content of binder (3 wt%), the LSB shows a highly stable long-term cycling performance with capacity retention decay values of 0.026% and 0.029% after 500 cycles at 5 and 10 C. Moreover, the cell shows an outstanding specific capacity of 228 mAh g^-1 at an ultrahigh charge-discharge rate of 20 C. This approach may significantly improve the design of the sulfur cathode and pave a facile way to fabricate commercially viable next-generation energy storage devices.

Three-Dimensional Porous Alginate Fiber Membrane Reinforced PEO-Based Solid Polymer Electrolyte for Safe and High-Performance Lithium Ion Batteries

The rational design and optimization of solid polymer electrolytes (SPEs) are critical for the application of safety and high efficiency lithium ion batteries (LIBs). Herein, we synthesized a novel poly(ethylene oxide) (PEO)-based SPE (PEO@AF SPE) with a cross-linking network by the introduction of alginate fiber (AF) membranes. Depending on the high-strength supporting AF skeleton and the cross-linking network formed by hydrogen bonds between the PEO matrix and AF skeleton, the obtained PEO@AF SPE exhibits an excellent tensile strength of 3.71 MPa, favorable heat resistance (close to 120 °C), and wide electrochemical stability window (5.2 V vs Li/Li⁺). Meanwhile, the abundant oxygen-containing groups in alginate macromolecular and the three-dimensional (3D) porous structure of the AF membrane can greatly increase Li⁺ anchor points and provide more Li⁺ migration pathways, leading to the enhancement of Li⁺ conduction and interfacial stability between the SPE and Li anode. Furthermore, the assembled LiFePO₄/PEO@AF SPE/Li cells also exhibit satisfactory electrochemical performance. These results reveal that PEO incorporating with AFs can boost the mechanical strength, thermostability, and electrochemical properties of the SPE simultaneously. Furthermore, one will expect that the newly designed PEO@AF SPE with cross-linked networks thus provides the possibility for future applications of safety and high-performance LIBs.

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.