Unveiling the environment-dependent mechanical properties of porous polypropylene separators

Electric field simulation, structure and properties of nanofiber- coated yarn prepared by multi-needle water bath electrospinning

To address the issue of low yield in the preparation of nanofiber materials using single-needle electrospinning technology, multi-needle electrospinning technology has emerged as a crucial solution for mass production. However, the mutual interference of multiple electric fields between the needles can cause significant randomness in the morphology of the produced nanofibers. To better predict the influence of electric field distribution on nanofiber morphology, simulation analysis of the multi-needle arrangement was conducted using finite element analysis (FEA) software. Nanofiber-coated yarn was produced continuously with the core yarn rotating. The water bath was utilized as the receiver of nanofibers on self-made water bath electrospinning equipment. The electric field distribution and mutual interference under seven different needle arrangements was simulated and analyzed by FEA software ANSYS Maxwell. The results indicated that when the needles were arranged diagonally in a staggered pattern and directly above the core yarn, the simulated electric field distribution was relatively uniform, with less mutual interference. The produced nanofibers exhibited a finer diameter and the diameter distribution was more concentrated. In addition, the nanofiber coating showed higher crystallinity and better mechanical properties.

Mass transport to generate the channels in cellulose polymers by vacuum-assisted process

This study developed a pore-connected PP-CA membrane by coating cellulose acetate onto a polypropylene filter. A new method was proposed to attach a CA/glycerin coating layer to a porous PP support without a separate binder. The pores of CA and PP were interconnected using a vacuum filtration device. By adding glycerin to the CA chains, the membrane region became more flexible due to glycerin plasticization. Water passed through the membrane under pressure differences, resulting in the formation of interconnected pores between cellulose acetate and polypropylene. The pore size and quantity could be adjusted by varying the molar ratio of glycerin. Fourier transform infrared spectroscopy revealed the interaction between CA and glycerin, while thermogravimetric analysis showed that the membrane's thermal stability increased by approximately 20 °C after vacuum filtration. This simple and cost-effective manufacturing process holds potential for mass-producing separators in the lithium-ion battery industry.

Porous polyvinyl alcohol/graphene oxide composite film for strain sensing and energy-storage applications

In this study, a flexible porous polyvinyl alcohol (PVA)/graphene oxide (GO) composite film was developed and tested for flexible strain sensing and energy-storage applications. Morphology and mechanical properties were studied; tensile strength and Young's modulus increased by 225% and 86.88%, respectively, at 0.5 wt% GO. The PVA/GO film possesses exceptional sensing ability to various mechanical strains, such as tension, compression, bending, and torsion. For example, the gauge factor of the PVA/GO film as a tensile-strain sensor was measured as 2.46 (246%). Under compression loads, the PVA/GO composite film showed piezoresistive and capacitive strain-sensing characteristics. Under 5 kPa of compression load, the relative resistance increased by 81% with a 100 msec response time; the relative capacitance increased by 160% with a 120 msec response time. The PVA/GO strain sensor exhibited high durability and reliability over 20 × 10³cycles of tensile strain and bending at 3.33 Hz. Moreover, the PVA/GO composite film showed good electrochemical properties due to its porous structure; the maximum capacitance was 124.7 F g^-1at 0.5 wt% GO. After 20 × 10³charging-discharging cycles, the capacitance retention rate was 94.45%, representing high stable capacitance performance. The results show that electrically conductive porous PVA nanocomposite films are promising candidates for strain sensing and energy-storage devices.

A Comparative Review of Lead-Acid, Lithium-Ion and Ultra-Capacitor Technologies and Their Degradation Mechanisms

As renewable energy sources, such as solar systems, are becoming more popular, the focus is moving into more effective utilization of these energy sources and harvesting more energy for intermittency reduction in this renewable source. This is opening up a market for methods of energy storage and increasing interest in batteries, as they are, as it stands, the foremost energy storage device available to suit a wide range of requirements. This interest has brought to light the downfalls of batteries and resultantly made room for the investigation of ultra-capacitors as a solution to these downfalls. One of these downfalls is related to the decrease in capacity, and temperamentality thereof, of a battery when not used precisely as stated by the supplier. The usable capacity is reliant on the complete discharge/charge cycles the battery can undergo before a 20% degradation in its specified capacity is observed. This article aims to investigate what causes this degradation, what aggravates it and how the degradation affects the usage of the battery. This investigation will lead to the identification of a gap in which this degradation can be decreased, prolonging the usage and increasing the feasibility of the energy storage devices.

A Review on Lithium-Ion Battery Separators towards Enhanced Safety Performances and Modelling Approaches

In recent years, the applications of lithium-ion batteries have emerged promptly owing to its widespread use in portable electronics and electric vehicles. Nevertheless, the safety of the battery systems has always been a global concern for the end-users. The separator is an indispensable part of lithium-ion batteries since it functions as a physical barrier for the electrode as well as an electrolyte reservoir for ionic transport. The properties of separators have direct influences on the performance of lithium-ion batteries, therefore the separators play an important role in the battery safety issue. With the rapid developments of applied materials, there have been extensive efforts to utilize these new materials as battery separators with enhanced electrical, fire, and explosion prevention performances. In this review, we aim to deliver an overview of recent advancements in numerical models on battery separators. Moreover, we summarize the physical properties of separators and benchmark selective key performance indicators. A broad picture of recent simulation studies on separators is given and a brief outlook for the future directions is also proposed.

Lithium-Ion Battery Separators for Ionic-Liquid Electrolytes: A Review

Ionic liquids (ILs) are widely studied as a safer alternative electrolyte for lithium-ion batteries. The properties of IL electrolytes compared to conventional electrolytes make them more thermally stable, but they also have poor wetting with commercial separators. In a lithium-ion battery, the electrolyte should completely wet out the separator and electrodes to reduce the cell internal resistance. Investigations of cell materials with IL electrolytes have shown that the wetting issues in IL-electrolyte cells are most likely due to poor separator compatibility, not electrode compatibility. A compatible separator must be developed before IL electrolytes can be used in commercial lithium-ion batteries. Herein, separators for IL electrolytes, including commercial and novel separators, are reviewed. Separators with different processing methods, polymers, additives, and different IL electrolytes are considered. Collated, the separator studies show a strong correlation between ionic conductivity and membrane porosity, even more than the electrolyte type. The challenge of a suitable separator for IL electrolytes is not solved yet. Herein, it is revealed that a separator for IL electrolytes will most likely require a combination of high thermal and mechanical stability polymer, ceramic additives, and an optimized manufacturing process.

Graphdiyne-Modified Polyimide Separator: A Polysulfide-Immobilizing Net Hinders the Shuttling of Polysulfides in Lithium-Sulfur Battery

Graphdiyne (GDY), a new type of carbon material with an electron-rich conjugated structure, has been investigated as a separator coating layer to enhance the electrochemical performance of lithium-sulfur (Li-S) battery. Acetylenic bond (-C≡C-C≡C-) and benzene ring in the GDY coating layer are experimentally verified to reversibly attract the soluble lithium polysulfides by chemical adsorption during cycling. Meanwhile, the shuttle effect of soluble polysulfides is further physically restricted by the GDY coating layer due to the evenly distributed pores (5.42 Å) and a consistent interlayer spacing (3.65 Å) of GDY. Moreover, GDY is a conducting carbon skeleton with high Li⁺ mobility that can improve the rate performance. Hence, Li-S battery with an as-prepared GDY coating layer shows excellent electrochemical performances including superior specific capacity, excellent rate performance, and low capacity attenuation rate. The high initial discharge capacity of 1648.5 mA h g^-1 at 0.1C and 819.5 mA h g^-1 even at a high rate of 2C is achieved by this novel separator. The initial capacity of 1112.9 mA h g^-1 at 0.5C is retained to 816.7 mA h g^-1 after 200 cycles with a low attenuation rate of 0.13% per cycle. Compared with other coated separators, these results show that the GDY coating layer endows the separator with superior electrochemical performances for Li-S battery.

Molecular engineering of organic electroactive materials for redox flow batteries

With high scalability and independent control over energy and power, redox flow batteries (RFBs) stand out as an important large-scale energy storage system.