Ionic conductivity enhancement in gel polymer electrolyte membrane with N-methyl-N-butyl-piperidine-bis(trifluoromethylsulfonyl) imide ionic liquid for lithium ion battery

Stable Operation Induced by Plastic Crystal Electrolyte Used in Ni-Rich NMC811 Cathodes for Li-Ion Batteries

The LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode material has been of significant consideration owing to its high energy density for Li-ion batteries. However, the poor cycling stability in a carbonate electrolyte limits its further development. In this work, we report the excellent electrochemical performance of the NMC811 cathode using a rational electrolyte based on organic ionic plastic crystal N-ethyl-N-methyl pyrrolidinium bis(fluorosulfonyl)imide C2mpyr[FSI], with the addition of (1:1 mol) LiFSI salt. This plastic crystal electrolyte (PC) is a thick viscous liquid with an ionic conductivity of 2.3 × 10-3 S cm-1 and a high Li+ transference number of 0.4 at ambient temperature. The NMC811@PC cathode delivers a discharge capacity of 188 mA h g-1 at a rate of 0.2 C with a capacity retention of 94.5% after 200 cycles, much higher than that of using a carbonate electrolyte (54.3%). Moreover, the NMC811@PC cathode also exhibits a superior high-rate capability with a discharge capacity of 111.0 mA h g-1 at the 10 C rate. The significantly improved cycle performance of the NMC811@PC cathode can be attributed to the high Li+ conductivity of the PC electrolyte, the stable Li+ conductive CEI film, and the maintaining of particle integrity during long-term cycling. The admirable electrochemical performance of the NMC811|C2mpyr[FSI]:[LiFSI] system exhibits a promising application of the plastic crystal electrolyte for high voltage layered oxide cathode materials in advanced lithium-ion batteries.

Dual In Situ Polymerization Strategy Endowing Rapid Ion Transfer Capability of Polymer Electrolyte toward Ni-Rich-Based Lithium Metal Batteries

Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) is one of the most promising candidate electrolyte matrices for high energy batteries. However, the spherical skeleton structure obtained through the conventional method fails to build continuous Li ion transmission channels due to the slow volatilization of high boiling solvent, leading to inferior cycling performance, especially in a Ni-rich system. Herein, a novel strategy is presented to enrich the Li ion transfer paths and improve the Li ion migration kinetics. The tactic is to prepare cross-linked segments through the PVDF-HFP matrix by adopting free radical polymerization and Li salt induced ring-opening polymerization. Most significantly, the visualization of the structure of as-prepared electrolyte is innovatively realized with the combination of polarization microscopy, transmission electron microscopy, scanning electron microscope-energy dispersive spectroscopy, PVDF-HFP, and cross-linked network form interconnected microstructures. Therefore, poly(glycidyl methacrylate and acrylonitrile)@poly(vinylidene fluoride-hexafluoropropylene) electrolyte presents a high ionic conductivity (1.04 mS cm^-1 at 30 °C) and a stable voltage profile for a Li/Li cell after 1200 h. After assembly with a LiNi_0.8 Co_0.15 Al_0.05 O₂ cathode, a high discharge specific capacity of 190.3 mAh g^-1 is delivered, and the capacity retention reaches 88.2% after 100 cycles. This work provides a promising method for designing high-performance polymer electrolytes for lithium metal batteries.

Ionic Liquid-Based Gels for Applications in Electrochemical Energy Storage and Conversion Devices: A Review of Recent Progress and Future Prospects

Ionic liquids (ILs) are molten salts that are entirely composed of ions and have melting temperatures below 100 °C. When immobilized in polymeric matrices by sol-gel or chemical polymerization, they generate gels known as ion gels, ionogels, ionic gels, and so on, which may be used for a variety of electrochemical applications. One of the most significant research domains for IL-based gels is the energy industry, notably for energy storage and conversion devices, due to rising demand for clean, sustainable, and greener energy. Due to characteristics such as nonvolatility, high thermal stability, and strong ionic conductivity, IL-based gels appear to meet the stringent demands/criteria of these diverse application domains. This article focuses on the synthesis pathways of IL-based gel polymer electrolytes/organic gel electrolytes and their applications in batteries (Li-ion and beyond), fuel cells, and supercapacitors. Furthermore, the limitations and future possibilities of IL-based gels in the aforementioned application domains are discussed to support the speedy evolution of these materials in the appropriate applicable sectors.

Hierarchically Engineered Nanocarbon Florets as Bifunctional Electrode Materials for Adsorptive and Intercalative Energy Storage

Three-dimensional dendritic nanostructured carbon florets (NCFs) with tailored porosity are demonstrated as electrochemically versatile electrodes for both adsorptive and intercalative energy storage pathways. Achieved through a single-step template-driven approach, the NCFs exhibit turbostratic graphitic lamellae in a floral assembly leading to high specific surface area and multi-modal pore distribution (920 m²/g). The synergism in structural and chemical frameworks, along with open-ended morphology, enables bifunctionality of hard carbon NCFs as symmetric adsorptive electrodes for supercapacitors (SCs) and intercalation anodes for hybrid potassium-ion capacitors (KICs). Flexible, all-solid-state SCs through facile integration of NCF with the ionic-liquid-imbibed porous polymeric matrix achieve high-energy density (20 W h/kg) and power density (32.7 kW/kg) without compromising on mechanical flexibility and cyclability (94% after 20k cycles). Furthermore, NCF as an anode in a full-cell hybrid KIC (activated carbon as cathode) delivers excellent electrochemical performance with maximum energy and power densities of 57 W h/kg and 12.5 kW/kg, respectively, when cycled in a potential window of 1.0-4.0 V. The exceptional bifunctional performance of NCF highlights the possibility of utilizing such engineered nanocarbons for high-performance energy storage devices.

Structural and Ionic Transport Properties of Protonic Conducting Solid Biopolymer Electrolytes Based on Carboxymethyl Cellulose Doped with Ammonium Fluoride

Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and transference number measurement (TNM) techniques were applied to investigate the complexation, structural, and ionic transport properties of and the dominant charge-carrier species in a solid biopolymer electrolyte (SBE) system based on carboxymethyl cellulose (CMC) doped with ammonium fluoride (NH₄F), which was prepared via a solution casting technique. The SBEs were partially opaque in appearance, with no phase separation. The presence of interactions between the host polymer (CMC) and the ionic dopant (NH₄F) was proven by FT-IR analysis at the C-O band. XRD spectra analyzed using Origin 8 software disclose that the degree of crystallinity (χ_c%) of the SBEs decreased with the addition of NH₄F, indicating an increase in the amorphous nature of the SBEs. Analysis of the ionic transport properties reveals that the ionic conductivity of the SBEs is dependent on the ionic mobility (μ) and diffusion of ions (D). TNM analysis confirms that the SBEs are proton conductors.