PEO-urea-LiTFSI ternary complex as solid polymer electrolytes

NMR studies of lithium and sodium battery electrolytes

This review focuses on the application of nuclear magnetic resonance (NMR) spectroscopy in the study of lithium and sodium battery electrolytes. Lithium-ion batteries are widely used in electronic devices, electric vehicles, and renewable energy systems due to their high energy density, long cycle life, and low self-discharge rate. The sodium analog is still in the research phase, but has significant potential for future development. In both cases, the electrolyte plays a critical role in the performance and safety of these batteries. NMR spectroscopy provides a non-invasive and non-destructive method for investigating the structure, dynamics, and interactions of the electrolyte components, including the salts, solvents, and additives, at the molecular level. This work attempts to give a nearly comprehensive overview of the ways that NMR spectroscopy, both liquid and solid state, has been used in past and present studies of various electrolyte systems, including liquid, gel, and solid-state electrolytes, and highlights the insights gained from these studies into the fundamental mechanisms of ion transport, electrolyte stability, and electrode-electrolyte interfaces, including interphase formation and surface microstructure growth. Overviews of the NMR methods used and of the materials covered are presented in the first two chapters. The rest of the review is divided into chapters based on the types of electrolyte materials studied, and discusses representative examples of the types of insights that NMR can provide.

Ultrathin Solid Polymer Electrolyte Design for High-Performance Li Metal Batteries: A Perspective of Synthetic Chemistry

Li metal batteries (LMBs) have attracted widespread attention in recent years because of their high energy densities. But traditional LMBs using liquid electrolyte have potential safety hazards, such as: leakage and flammability. Replacing liquid electrolyte with solid polymer electrolyte (SPE) can not only significantly improve the safety, but also improve the energy density of LMBs. However, till now, there is only limited success in improving the various physical and chemical properties of SPE, especially in thickness, posing great obstacles to further promoting its fundamental and applied studies. In this review, the authors mainly focus on evaluating the merits of ultrathin SPE and summarizing its existing challenges as well as fundamental requirements for designing and manufacturing advanced ultrathin SPE in the future. Meanwhile, the authors outline existing cases related to this field as much as possible and summarize them from the perspective of synthetic chemistry, hoping to provide a comprehensive understanding and serve as a strategic guidance for designing and fabricating high-performance ultrathin SPE. Challenges and opportunities regarding this burgeoning field are also critically evaluated at the end of this review.

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.

A Silk Protein-Based Eutectogel as a Freeze-Resistant and Flexible Electrolyte for Zn-Ion Hybrid Supercapacitors

A eutectogel (ETG) based on immobilizing a zinc salt deep eutectic solvent (DES) in a silk protein backbone is prepared by a coagulating bath method as a solid electrolyte for Zn-ion hybrid supercapacitors (ZHSCs). The Zn salt DES is composed by ethylene glycol (EG), urea, choline chloride (ChCl), and zinc chloride (ZnCl₂) with a molar ratio of 6:10:3:3. A strong bonding of the DES liquid to the silk protein backbone is formed between protein macromolecules and the DES due to plenty of hydrogen bonds in both materials. The as-prepared ETG membrane is dense and has no obvious void defects, which possesses a fracture strength of 7.58 MPa and environmental stability. As a solid electrolyte, the ETG membrane exhibits a higher Zn²⁺ transference number of about 0.60 and a high ionic conductivity (12.31 mS cm^-1 at room temperature and 3.63 mS cm^-1 at -20 °C). A ZHSC (Zn∥ETG∥C) with the silk protein-based ETG electrolyte is assembled by Zn and active carbon as the anode and the cathode, respectively, which delivers a specific capacitance of 342.8 F g^-1 at a current density of 0.2 A g^-1 and maintains excellent cycling stability with 80% capacitance retention after 20,000 cycles at a high current rate (5 A g^-1) at room temperature. Moreover, the Zn∥ETG∥C device can safely work under a lower temperature of about -18 °C and damaging situations, such as folding states and even cutting tests. The interface evolutions between the Zn anode and the ETG electrolyte are explored, and it was found that a ZnCO₃/Zn(CH₂OCO₂)₂ solid electrolyte interphase is in situ formed on the Zn anode, which can inhibit the growth of Zn dendrites. This work provides a new way to fabricate advanced electrolytes for applications in Zn-ion hybrid supercapacitors.

Solvent-polymer guest exchange in a carbamazepine inclusion complex: structure, kinetics and implication for guest selection

Solvent–polymer guest exchange in a carbamazepine inclusion complex in a stirred solution was studied and a mechanism was proposed.

Review of Recent Nuclear Magnetic Resonance Studies of Ion Transport in Polymer Electrolytes

Current and future demands for increasing the energy density of batteries without sacrificing safety has led to intensive worldwide research on all solid state Li-based batteries. Given the physical limitations on inorganic ceramic or glassy solid electrolytes, development of polymer electrolytes continues to be a high priority. This brief review covers several recent alternative approaches to polymer electrolytes based solely on poly(ethylene oxide) (PEO) and the use of nuclear magnetic resonance (NMR) to elucidate structure and ion transport properties in these materials.

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

Developing a gel polymer electrolyte with a cross-linked structure is one of the best choices to improve the mechanical strength of the gel polymer electrolyte without sacrificing its lithium-ion transportation properties. However, the cost is always too high. Herein, a novel gel polymer electrolyte based on three-dimensional cross-linked chitosan-poly(ethylene glycol) diglycidyl ether macromolecule network was designed and synthesized through a simple and environmental harmless method, with sustainable and cheap chitosan as major material. The obtained gel polymer electrolyte shows improved mechanical strength of 5.5 MPa, which is higher than that of other gel polymer electrolytes without inert frameworks. The optimized gel polymer electrolyte exhibits a good lithium ionic conductivity of 2.74 × 10^-4 S cm^-1 with a superior lithium-ion transfer number of 0.869 at 25 °C. Lithium battery assembled with this gel polymer electrolyte demonstrates an initial discharge capacity of 146.8 mA h g^-1, which retains 88.49% capacity after 360 cycles at 0.2C. Moreover, this gel polymer electrolyte possesses good interfacial compatibility with lithium anode. Therefore, the growth of lithium dendrite is greatly delayed. This research proves the great possibility of applying sustainable and cost-effective chitosan into gel polymer electrolyte and lithium batteries.

Electrostatic-Force-Assisted Dispensing Printing of Electrochromic Gels for Low-Voltage Displays

In this study, low-voltage, printed, ion gel-based electrochromic devices (ECDs) were successfully fabricated. While conventional dispensing printing provides irregularly printed electrochromic (EC) gels, we improved the adhesion between the printed gel and the substrate by applying an external voltage. This is called electrostatic-force-assisted dispensing printing. As a result, we obtained well-defined, printed, EC gels on substrates such as indium tin oxide-coated glass. We fabricated a gel-based ECD by simply sandwiching the printed EC gel between two transparent electrodes. The resulting ECD, which required a low coloration voltage (∼0.6 V), exhibited a high coloration efficiency (η) of 161 cm²/C and a large transmittance contrast (∼82%) between the bleached and colored states at -0.7 V. In addition, electrostatic-force-assisted dispensing printing was utilized to fabricate directly patterned ECDs.