Among the most commonly used agents as electrode materials and binders, Polyvinylidene Fluoride (PVDF) is known as a highly inert and non-reactive thermoplastic fluoropolymer which is synthesized as the result of vinylidene polymerization and is regarded as plastic material employed where a high level of purity and resistance towards hydrocarbons, acids and solvents is required.
PVDF has found applications such as fabricating sheets, tubing, wiring insulators, plates, films and piping products in areas comprising defense industries, medical devices and semiconductors and more specifically, in lithium-ion (Li-ion) batteries as an electrode binder. Technically, a binder agent in Li-ion batteries serves as a significant factor and a capable agent to facilitate the dispersion in order to increase the exposure electrode species and process their adhesion to the current collector. As Nanografi, we are offering types of li-ion battery binders including PVDF binder to enhance a range of battery projects, productions, and technologies.
Properties of Polyvinylidene Fluoride
Polyvinylidene fluoride which is also known as polyvinylidene difluoride (PVDF) is an extremely inert and non-reactive thermoplastic fluoropolymer synthesized as a result of the polymerization process of vinylidene difluoride. PVDF is a material behaving like plastic and has applications based on its resistance to solvents, acids and hydrocarbons as well as the highest purity required when compared to other fluoropolymers such as polytetrafluoroethylene. PVDF possesses low-density and is usually in the form of a plate and in insulators for premium wiring, tubing, piping products and sheet and can be injected, welded, or molded with applications in medical devices, semiconductors, chemicals and defense industries and more specifically, in fabricating electric material in Lithium-ion batteries. PVDF is also used as a crosslinking closed-cell foam with growing interest. Due to its inert nature, PVDF is used in contact with food products approved by the Food and Drug Administration (FDA) and is categorized as a non-toxic material. PVDF is a fine powder it is used as an ingredient in high-end paints for metals. The pains out of PVDF Show excellent gloss and color retention and have applications on many prominent buildings including Petronas Towers in Malaysia and Taipei 101 in Taiwan. Commercial and residential metal roofing also take advantage of this material. PVDF is also employed in designing membranes to be used in western blotting for proteins in mobilization based on its non-specific affinity for amino acids. PVDF is extensively used as a binder component in lithium-ion batteries for carbon electrodes in supercapacitors and many electrochemical applications.
Physically, PVDF shows strong piezoelectricity whose piezoelectric coefficient of poled thin films ranges from 6 to 7 PC/N when placed under a strong electric field to cause a net dipole moment. Its piezoelectric coefficient is 10 times the value in the case of other polymers. Polyvinylidene difluoride possesses a glass transition temperature of about -35°C and is nearly 60% crystalline in nature. PVDF could be stretched mechanically to orient the molecular chains and then subsequently be pulled under tension in order to give the materials in action their piezoelectric properties. This material occurs in several forms as alpha, beta and gamma phases based on the conformations of the chain as transport couch linkages. When PVDF is poled, it shows the behavior of a ferroelectric polymer with efficient pyroelectric and piezoelectric properties making it a promising agent for battery and sensor applications. PVDF inclusion in thin films has also applications in sensors of thermal cameras.
Binders and Li-Ion Batteries
Lithium batteries are deemed to be the main source of power or backup power source for portable communication devices as well as mobile electronic devices. Lithium batteries have been calling increasing attention in the industrial and scientific sectors because of their remarkable electromotive force and high energy density. Recently, there has been a huge amount of research in order to design novel structures of electrode materials and develop never-before-seen battery binders so that the demand for higher energy density is mitigated and cycle properties of batteries are met. In effect, aqueous binders have been shown to possess more advantages properties and merits including lower cost, battery safety and friendly ecosystem in combination with water as a dispersant to make them emerge as the ideal binders for environmentally friendly lithium-ion batteries and safety (1).
Revealing the PVDF Binder Performance for Li-ion Batteries
There is a fact that the conventional polyvinylidene fluoride binder functions perfectly with the graphite anode. Nevertheless, when it is combined with silicon in composites in order to enhance the density of energy of lithium-ion batteries, it runs into considerable capacity failure. It has been revealed by scanning electron microscopy and energy-dispersive x-ray spectroscopy analyses that this failure originates from the connectivity loss between the graphite, silicon and PVDF binder as a result of the mechanical stresses undergone in the course of the battery recycling. Particularly, it has turned out for the first time that the PVDF binder bears a chemical decomposition during the battery cycling stemming from the composite, the silicon-only, and even graphite-only electrodes, despite the excellent battery performance. Based on x-ray photoelectron emission electron microscopy and x-ray photoelectron spectroscopy techniques, lithium fluoride (LiF) is recognized as a predominant decomposition agent with distribution in the electrodes in an account of the differences and the possible interactions between PVDF graphite and silicone which in turn correlates with the battery performance. It has been shown that the most appropriate binder for the composite electrode comes up when a chemically interactive polymer functions with both graphite and silicon as a whole (2).
To discover more, you can read Polytetrafluoroethlyene as excellent binfor for li-ion battery.
Effect of Different Binders on the Electrochemical Performance of Metal Oxide Anode for Lithium-Ion Batteries
In the case of testing the electrochemical performance of metal oxides anode for lithium-ion batteries, a qualified binder serves a considerable role in the electrochemical performance however, an appropriate binder to prepare the anode of metal oxides of lithium-ion batteries has not been studied so systematically. On the way to solve this problem, five distinct binders including PVDF HSV 900, PVDF 301f, PVDF Solvay 5130, sodium carboxymethyl cellulose, and styrene-butadiene rubber have been investigated to fabricate electrodes for Li-ion batteries. Electrochemical experiments confirm that carboxymethyl cellulose binder could profoundly mitigate the bonding capacity, rate performance of battery on a note, cycle stability and, in effect, much better than PVDF (3).
PVDF has been used as a capable binder for the cathode in Li-ion batteries due to its profound thermal stability and proper adhesion properties and excellent electrochemical behavior. As a result of the adhesion between electrode films and the current collectors achieved by PVDF binders for lithium-ion battery electrodes, it is possible to obtain higher energy density and longer life cycle actor lowest amount of PVDF binder inclusion. Furthermore, the functional groups in PVDF binder which are polar in nature lead to lower internal energy. In addition to this, it is possible to ensure the long-term stability of PVDF desirable chemical resistance in the aggressive environment of lithium-ion batteries which contain organic carbonate and lithium salts.
1.Online, V. A. batteries †. 24859–24862 (2014) doi:10.1039/c4ra01351d.
2.Zhao, X. et al. Revealing the Role of Poly ( vinylidene fluoride ) Binder in Si / Graphite Composite Anode for Li-Ion Batteries. (2018) doi:10.1021/acsomega.8b01388.
3.Wang, R. et al. Effect of Different Binders on the Electrochemical Performance of Metal Oxide Anode for Lithium-Ion Batteries. (2017) doi:10.1186/s11671-017-2348-6.