Gel polymer electrolyte combined lignocellulose with sodium alginate in lithium-ion battery

The adoption of gel polymer electrolyte (GPE) is a solution to efficiently solve the serious security risk of lithium-ion batteries (LIBs). GPE based on lignocellulose (LC) and sodium alginate (SA) was prepared. When the proportion of SA reaches up to 20 wt.%, the obtained composite membrane has a liquid electrolyte uptake of 337 wt.% and a porosity of 58%, and its mechanical strength is over four times than that of pure LC-based membrane. In addition, the corresponding GPE with 20 wt.% SA (GLCSA-20) presents high lithium-ion transference number of 0.76, distinguished ion conductivity of 2.70 × 10[Formula: see text] S cm[Formula: see text], excellent discharge specific capacity (124 mAh cm[Formula: see text] at 1 C when 200th cycle of Li∥GLCSA-20∥LiFePO[Formula: see text] and outstanding cyclic stability. These virtues support that the GLCSA-20 has great potential for applications in safe LIBs.

Design of a Single-Ion Conducting Polymer Electrolyte for Sodium-Ion Batteries

A sodium bis(fluoroallyl)malonato borate salt (NaBFMB) was synthesized. NaBFMB can be photo-crosslinked to create a single-ion conducting electrolyte (NaSIE), with anions immobilized through the 3-D crosslinked network. The NaSIE can be prepared either as a free-standing film or through a drop-cast method followed by a photo crosslinking method for an in-situ formation on top of the electrodes. The free-standing film of NaSIE has a high ionic conductivity of 2×10-3 S/cm at 30 oC, and a high transference number (tNa+) of 0.91 . The electrochemical stability of NaSIE polymer electrolyte was demonstrated be stable up to 5 V vs Na/Na+. When tested inside a symmetrical Na//Na cell, the NaSIE shows a critical current density (CCD) of 0.4 mA/cm2. The stability of NaSIE was further demonstrated via a long cycling of the stripping/plating test with a current density of 0.1 mA/cm2 at five-minute intervals for over 10,000 minutes. Using the in-situ method, NaSIE was used as the electrolyte for a sodium metal battery using P2cathode of Na0.67Ni0.33Mn0.67O2 (NNMO) and was cycled between the cut-off voltages of 2.0 – 4.0 V. A high initial specific capacity (85.7 mAh/g) with a capacity retention of 86.79% after 150 cycles was obtained.

Electrical, electrochemical and structural studies of a chlorine-derived ionic liquid-based polymer gel electrolyte

In the present article, an ionic liquid-based polymer gel electrolyte was synthesized by using poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) as a host polymer. The electrolyte films were synthesized by using the solution casting technique. The as-prepared films were free-standing and transparent with good dimensional stability. Optimized electrolyte films exhibit a maximum room-temperature ionic conductivity of σ = 8.9 × 10−3 S·cm−1. The temperature dependence of the prepared polymer gel electrolytes follows the thermally activated behavior of the Vogel–Tammann–Fulcher equation. The total ionic transference number was ≈0.91 with a wider electrochemical potential window of 4.0 V for the prepared electrolyte film which contains 30 wt % of the ionic liquid. The optimized films have good potential to be used as electrolyte materials for energy storage applications.

Insights into Ionic Liquid Electrolyte Transport and Structure via Operando Raman Microspectroscopy

Ionic liquid electrolytes (ILEs) have become popular in various advanced Li-ion battery chemistries because of their high electrochemical and thermal stability, and low volatility. However, due to their relatively high viscosity and poor Li+ diffusion, it is thought large concentration gradients form, reducing their rate capability. Here, we utilised operando Raman microspectroscopy to visualise ILE concentration gradients for the first time. Specifically, using lithium bis(fluorosulfonyl)imide (LiFSI) in N-propyl- N-methylpyrrolidinium FSI, its "apparent" diffusion coefficient, lithium transference number, thermodynamic factor, ionic conductivity and resistance of charge-transfer against lithium metal, were isolated. Furthermore, the analysis of these concentration gradients led to insights into the bulk structure of ILEs, which we propose is composed of large, ordered aggregates.

Measurement of Transport Number of Lithium in Glycerol Assisted by Fourier Transform Spectroscopy Analysis: Progress towards Elaboration of Optimal Electrolyte of Friendly Environmental Battery

Up to now, a great deal of research investigations on lithium ion conductors has been carried out, because they are potentially utilized in the solid electrolytes of the batteries and the electrochemical devices. However, in order to elaborate new ecological batteries of lithium, it becomes primordial to study and understand the properties of transport of the lithium electrolytes using eco-friendly solvents, with view perhaps to find out the best electrolyte for such devices. In fact, the electromotive forces (EMFs) of lithium chloride electrolyte in the hydrogen-bonded solvents glycerol, were measured using the concentration cells (CCs) 0.005/0.05 and 0.05/0.5. Then the transport numbers of the lithium-ion were deduced by means of the Nernst equation in combination with the Debye-Huckel limiting law. Whilst the activation energy values were calculated from the parameters of the fitting of the transference number data to the empirical power law, yielding a regression coefficient of 95.9% for the most concentrated concentration cell. The structure and interactions in the lithium electrolyte solution were studied by vibrational Infra-Red spectroscopy. The experimental data were discussed and compared to those obtained previously, using impedance spectroscopy of glass-forming glycerolate lithium electrolytes for the same purpose. Despite the enormous difference between their viscosities; glycerol shows similar activation energy (i.e. 31.40 kJ.mol–1) with water (i.e. 31.73 kJ.mol–1), in particular at very low concentration, confirming both solvents being hydrogen-bonded. Besides, this study suggests the utilization of the glycerol-lithium ion electrolyte for future conception of ecological lithium-ion battery, rather than those using ion electrolyte polymer currently on the market. Similarly to relaxation and conductivity, the transport number data suggests that the diffusion of conformational states is also monitoring the overall lithium ion transport mechanism.

Rational Design of Cellulose Nanofibrils Separator for Sodium-Ion Batteries

Cellulose nanofibrils (CNF) with high thermal stability and excellent electrolyte wettability attracted tremendous attention as a promising separator for the emerging sodium-ion batteries. The pore structure of the separator plays a vital role in electrochemical performance. CNF separators are assembled using the bottom-up approach in this study, and the pore structure is carefully controlled through film-forming techniques. The acid-treated separators prepared from the solvent exchange and freeze-drying demonstrated an optimal pore structure with a high electrolyte uptake rate (978.8%) and Na+ transference number (0.88). Consequently, the obtained separator showed a reversible specific capacity of 320 mAh/g and enhanced cycling performance at high rates compared to the commercial glass fiber separator (290 mAh/g). The results highlight that CNF separators with an optimized pore structure are advisable for sodium-ion batteries.