Novel cellulose/polyurethane composite gel polymer electrolyte for high performance lithium batteries

Polyurethane-Based Gel Electrolyte for Application in Flexible Electrochromic Devices

For the application in flexible electrochromic devices (ECDs) on plastic substrates, a new polyurethane-based gel electrolyte was manufactured. In this context, the curing behavior and the influence of the proportion of solvent and salt on the ion conductivity as well as the optical and mechanical properties were investigated. Furthermore, the stoichiometric ratio of the polyurethane matrix was varied to influence the ion conductivity. As an isocyanate component, the aliphatic difunctional polyisocyanate prepolymer, synthesized by Hexamethylen-1,6-diisocyanat (HDI), was chosen since the resulting polyurethane is considered to be particularly lightfast, color-stable and temperature-resistant and therefore frequently used for paints and coatings. As polyol a trifunctional polyetherpolyol was selected to form a wide-meshed crosslinked matrix to achieve a mechanically stable but flexible electrolyte, that enables the processing and bending of film-based ECDs. The additives amount and the matrix stoichiometric ratio affected the curing behavior and curability. The salt content had almost no influence on the measured properties in the chosen experimental space. Solvent content had a great influence on ion conductivity and mechanical properties. An understoichiometric ratio of the polyurethane matrix (0.85) increases the ion conductivity and the mechanical flexibility, but also the optical properties in a negative manner. The best specific ion conductivity with 10−5 S/cm was reached with an understoichiometric ratio of 0.85 and a high solvent content (30 wt%). Concluding, due to its high flexibility and transmittance, color neutrality and sufficient ion conductivity, the application of the researched electroyte in ECDs might be suitable. A demonstrator ECD was successfully manufactured and conducted.

Observation of ionic conductivity on PUA-TBAI-I2 gel polymer electrolyte

Jatropha oil-based polyurethane acylate gel polymer electrolyte was mixed with different concentrations of tetrabutylammonium iodide salt (TBAI). The temperature dependences of ionic conductivity, dielectric modulus and relaxation time were studied in the range of 298 to 393 K. The highest ionic conductivity of (1.88 ± 0.020) × 10^–4 Scm⁻¹ at 298 K was achieved when the gel contained 30 wt% of TBAI and 2.06 wt% of I₂. Furthermore, the study found that conductivity-temperature dependence followed the Vogel-Tammann Fulcher equation. From that, it could be clearly observed that 30 wt% TBAI indicated the lowest activation energy of 6.947 kJ mol⁻¹. By using the fitting method on the Nyquist plot, the number density, mobility and diffusion coefficient of the charge carrier were determined. The charge properties were analysed using the dielectric permittivity, modulus and dissipation factor. Apart from this, the stoke drag and capacitance were determined.

Polysaccharides for sustainable energy storage - A review

The increasing amount of electric vehicles on our streets as well as the need to store surplus energy from renewable sources such as wind, solar and tidal parks, has brought small and large scale batteries into the focus of academic and industrial research. While there has been huge progress in performance and cost reduction in the past years, batteries and their components still face several environmental issues including safety, toxicity, recycling and sustainability. In this review, we address these challenges by showcasing the potential of polysaccharide-based compounds and materials used in batteries. This particularly involves their use as electrode binders, separators and gel/solid polymer electrolytes. The review contains a historical section on the different battery technologies, considerations about safety on batteries and requirements of polysaccharide components to be used in different types of battery technologies. The last sections cover opportunities for polysaccharides as well as obstacles that prevent their wider use in battery industry.

Cellulosic materials-enhanced sandwich structure-like separator via electrospinning towards safer lithium-ion battery

The latent security issue has become the foremost anxiety for lithium-ion batteries (LIBs) wide-ranging of commercialized applications. Hence, the performance of a separator such as chemical durability, electrical insulator, and thermal stability must be superior. Herein, we exhibit a sandwich-structured composite membrane with enhanced thermal resistance and electrolyte affinity, which was prepared by layer-by-layer electrospinning deposition. After 50 cycles, the battery with a 3 wt.% halloysite nanotube electrospinning separator retained 91.80% of its initial discharge capacity, that was a drastic improvement over the commercial polypropylene separator with the numeric of 79.98%. This predominant composite membrane was prepared via an eco-friendly technics and can be thought of an assuring, expectant separator towards high performance lithium-ion batteries.

In Situ Cross-Linked Gel Polymer Electrolyte Membranes with Excellent Thermal Stability for Lithium Ion Batteries

Novel gel polymer electrolyte membranes with excellent thermal stability are fabricated via a combination of physical blending and chemical cross-linking procedures. Precursor porous membranes made of poly(vinylidene fluoride) (PVDF) and polystyrene-poly(ethylene oxide)-polystyrene (PS-PEO-PS) triblock copolymer composites are prepared by a phase-inversion technique, and the gel polymer electrolyte membranes are finished by in situ hypercrosslinking of the PS segments in precursor membranes. The latter cross-linking procedure could consolidate pore configuration and thus greatly enhance the thermal stability of the obtained cross-linked composite membranes. The membranes with optimal PS/PEO ratios can retain reasonable porosity with little dimensional shrinkage at high temperatures up to 260 °C. Gel polymer electrolytes with these cross-linked membranes as matrices exhibit much higher ionic conductivities (up to 1.38 × 10^-3 S cm^-1 at room temperature) than those based on pure PVDF membranes. Li/LiFePO₄ half cells assembled with these gel polymer electrolytes exhibit good cycling performance and rate capability. These results indicate that the Friedel-Crafts reaction based hypercrosslinking is an efficient method to construct highly heat-resistant polymer electrolytes for lithium ion batteries, particularly advantageous in applications that require high-temperature usage.

A Parallel Bicomponent TPU/PI Membrane with Mechanical Strength Enhanced Isotropic Interfaces Used as Polymer Electrolyte for Lithium-Ion Battery

In this work, a side-by-side bicomponent thermoplastic polyurethane/polyimide (TPU/PI) polymer electrolyte prepared with side-by-side electrospinning method is reported for the first time. Symmetrical TPU and PI co-occur on one fiber, and are connected by an interface transition layer formed by the interdiffusion of two solutions. This structure of the as-prepared TPU/PI polymer electrolyte can integrate the advantages of high thermal stable PI and good mechanical strength TPU, and mechanical strength is further increased by those isotropic interface transition layers. Moreover, benefiting from micro-nano pores and the high porosity of the structure, TPU/PI polymer electrolyte presents high electrolyte uptake (665%) and excellent ionic conductivity (5.06 mS·cm-1) at room temperature. Compared with PE separator, TPU/PI polymer electrolyte exhibited better electrochemical stability, and using it as the electrolyte and separator, the assembled Li/LiMn₂O₄ cell exhibits low inner resistance, stable cyclic and notably high rate performance. Our study indicates that the TPU/PI membrane is a promising polymer electrolyte for high safety lithium-ion batteries.

Facile Synthesis of Unique Cellulose Triacetate Based Flexible and High Performance Gel Polymer Electrolyte for Lithium Ion Batteries

Lithium ion batteries (LIBs) with polymer based electrolytes have attracted enormous attention due to the possibility of fabricating intrinsically safer and flexible devices. However, economical and eco-friendly sustainable technology is an oncoming challenge to fulfill the ever increasing demand. To circumvent this issue, we have developed a gel polymer electrolyte (GPE) based on renewable polymers like cellulose triacetate and poly(polyethylene glycol methacrylate) p(PEGMA) using a photo polymerization technique. Cellulose triacetate offers good mechanical strength with improved ionic conductivity, owing to its ether and carbonyl functional groups. It is observed that the presence of an open network has a critical impact on lithium ion transport. At room temperature, GPE PC exhibits an optimal ionic conductivity of 1.8 × 10^-3 S cm^-1 and transference number of 0.7. Interestingly, it affords an excellent electrochemical stability window up to 5.0 V vs Li/Li⁺. GPE PC shows a discharge capacity of 164 mAhg^-1 after the first cycle when evaluated in a Li/GPE/LiFePO₄ cell at 0.5 C-rate. Interfacial compatibility of GPE PC with lithium metal improves the overall cycling performance. This system provides a guiding principle toward a future renewable and flexible electrolyte design for flexible LIBs (FLIBs).