Molecular-level insights into structure and dynamics in ionic liquids and polymer gel electrolytes

Dynamics of ionic liquid-polymer gel membranes-Insight from NMR relaxometry for [BMIM][BF4]-PVDF-HFP systems

1H spin-lattice relaxation experiments have been performed for ionic liquid-polymer gel membranes, including 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) with different proportions. The experiments have been performed in a broad range of resonance frequencies (from about 5 Hz to 40 MHz) vs temperature and complemented with analogous studies for [BMIM][BF4] in bulk as a reference. A model of the relaxation processes in the membranes has been proposed. The model includes two relaxation contributions. One of them corresponds to the concept of restricted, two-dimensional translation diffusion with a residence lifetime, while the second one has the form characteristic of polymers (mathematically similar to the limiting behavior of two-dimensional translation diffusion with a very long residence lifetime). The extensive dataset has been consistently interpreted in terms of the model, revealing two dynamical processes on the time scales of 10-7 s (for the second relaxation contribution) and 10-9 s (for the first one). The relationship of these relaxation contributions to the motion of the polymer or ionic liquid-polymer complexes and to the translation diffusion of BMIM cations in the matrix has been discussed.

Optimized Ribociclib nanostructured lipid carrier for the amelioration of skin cancer: Inferences from ex-vivo skin permeation and dermatokinetic studies

Current research focuses on explicitly developing and evaluating nanostructured lipidic carriers (NLCs) for the chemotherapeutic drug Ribociclib (RCB) via the topical route to surmount the inherent bioavailability shortcomings. The absolute oral bioavailability has not been determined, but using a physiologically based pharmacokinetic model it was predicted that 65.8 % of the standard dose of RCB (600 mg) would be absorbed mainly in the small intestine. RCB-NLCs were produced using the solvent evaporation method, and Box-Behnken Design (BBD) was employed to optimize composition. The prepared NLCs had an average PS of 79.29 ± 3.53 nm, PDI of 0.242 ± 0.021, and a %EE of 86.07 ± 3.14. The TEM analysis disclosed the spherical form and non-aggregative nature of the NLCs. The outcomes of an in-vitro release investigation presented cumulative drug release of 84.97 ± 3.37 % in 24 h, significantly higher than that from the RCB suspension (RCB-SUS). Ex-vivo skin permeation investigations on rodent (Swiss albino mice) revealed that RCB-NLCs have 1.91 times increases in skin permeability comparable to RCB-SUS. Compared to RCB-SUS, RCB-NLCs were able to penetrate deeper into the epidermis membrane than RCB-SUS as per the findings of confocal microscopy. In dermatokinetic study, higher amount of RCB was maintained in both the layers of mice's skin when treated with RCB-NLCs gel comparable to the RCB-SUS gel preparation. The in-vitro, ex-vivo, CLSM, and dermatokinetics data demonstrated a significant possibility for this novel RCB formulation to be effective against skin cancer.

Nuclear Magnetic Resonance Relaxation Pathways in Electrolytes for Energy Storage

Nuclear Magnetic Resonance (NMR) spin relaxation times have been an instrumental tool in deciphering the local environment of ionic species, the various interactions they engender and the effect of these interactions on their dynamics in conducting media. Of particular importance has been their application in studying the wide range of electrolytes for energy storage, on which this review is based. Here we highlight some of the research carried out on electrolytes in recent years using NMR relaxometry techniques. Specifically, we highlight studies on liquid electrolytes, such as ionic liquids and organic solvents; on semi-solid-state electrolytes, such as ionogels and polymer gels; and on solid electrolytes such as glasses, glass ceramics and polymers. Although this review focuses on a small selection of materials, we believe they demonstrate the breadth of application and the invaluable nature of NMR relaxometry.

Molecular Insight into the Ionic Conduction of Quaternary Ammonium and Phosphonium Cation-Based Ionic Liquids Using Dielectric and Spectroscopy Analyses

We analyzed the primary properties of ionic liquids (ILs) comprising quaternary phosphonium cations and bis(trifluoromethylsulfonyl) amide anions and compared them with those of corresponding quaternary-ammonium-cation-based ILs. Broadband dielectric spectroscopy was used to confirm the coupling between the translational and orientational motions of ions, and our results demonstrated that the high ionic conductivity of the phosphonium-based ILs was attributed to their fast rotational dynamics. The differences between ILs with different cations were further evaluated using vibrational (Raman and terahertz) spectroscopy. The Raman spectroscopy data revealed that the cation structure affected the conformation and flexibility (conformational change) of the anion. Furthermore, terahertz spectroscopy allowed us to evaluate the relationship between ion transport and intermolecular interactions between the cation and anion of ILs.

Ion and Molecular Transport in Solid Electrolytes Studied by NMR

NMR is the method of choice for molecular and ionic structures and dynamics investigations. The present review is devoted to solvation and mobilities in solid electrolytes, such as ion-exchange membranes and composite materials, based on cesium acid sulfates and phosphates. The applications of high-resolution NMR, solid-state NMR, NMR relaxation, and pulsed field gradient ¹H, ⁷Li, ¹³C, ¹⁹F, ²³Na, ³¹P, and ¹³³Cs NMR techniques are discussed. The main attention is paid to the transport channel morphology, ionic hydration, charge group and mobile ion interaction, and translation ions and solvent mobilities in different spatial scales. Self-diffusion coefficients of protons and Li⁺, Na⁺, and Cs⁺ cations are compared with the ionic conductivity data. The microscopic ionic transfer mechanism is discussed.

Polymer Electrolytes for Lithium-Ion Batteries Studied by NMR Techniques

This review is devoted to different types of novel polymer electrolytes for lithium power sources developed during the last decade. In the first part, the compositions and conductivity of various polymer electrolytes are considered. The second part contains NMR applications to the ion transport mechanism. Polymer electrolytes prevail over liquid electrolytes because of their exploitation safety and wider working temperature ranges. The gel electrolytes are mainly attractive. The systems based on polyethylene oxide, poly(vinylidene fluoride-co-hexafluoropropylene), poly(ethylene glycol) diacrylate, etc., modified by nanoparticle (TiO₂, SiO₂, etc.) additives and ionic liquids are considered in detail. NMR techniques such as high-resolution NMR, solid-state NMR, magic angle spinning (MAS) NMR, NMR relaxation, and pulsed-field gradient NMR applications are discussed. ¹H, ⁷Li, and ¹⁹F NMR methods applied to polymer electrolytes are considered. Primary attention is given to the revelation of the ion transport mechanism. A nanochannel structure, compositions of ion complexes, and mobilities of cations and anions studied by NMR, quantum-chemical, and ionic conductivity methods are discussed.

Lithium Nafion-Modified Li6.05Ga0.25La3Zr2O11.8F0.2 Trilayer Hybrid Solid Electrolyte for High-Voltage Cathodes in All-Solid-State Lithium-Metal Batteries

All-solid-state batteries containing ceramic-polymer solid electrolytes are possible alternatives to lithium-metal batteries containing liquid electrolytes in terms of their safety, energy storage, and stability at elevated temperatures. In this study we prepared a garnet-type Li_6.05Ga_0.25La₃Zr₂O_11.8F_0.2 (LGLZOF) solid electrolyte modified with lithium Nafion (LiNf) and incorporated it into poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrixes. We used a solution-casting method to obtain bilayer (Bi-HSE) and trilayer (Tri-HSE) hybrid solid electrolytes. A layer of functionalized multiwalled carbon nanotubes (f-MWCNTs) coated with LiNf (LiNf@f-MWCNT) in the Tri-HSE led to good compatibility with the polymer slurry and adhered well to the Li anode, thereby improving the interfacial contact at the electrode-solid electrolyte interface and suppressing dendrite growth. The Tri-HSE membrane displayed high ionic conductivity (5.6 × 10^-4 S cm^-1 at 30 °C), a superior Li⁺ transference number (0.87), and a wide electrochemical window (0-5.0 V vs Li/Li⁺). In addition, Li symmetrical cells incorporating this hybrid electrolyte possessed excellent interfacial stability over 600 h at 0.1 mA cm^-2 and a high critical current density (1.5 mA cm^-2). Solid-state lithium batteries having the structure LiNf@LiNi_0.8Co_0.1Mn_0.1O₂/Tri-HSE/Li delivered excellent room-temperature stable cycling performance at 0.5C, with a capacity retention of 85.1% after 450 cycles.