PVDF new material project for photovoltaic and lithium batteries.

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The polyvinylidene fluoride (PVDF) project is one of the key projects that the National Development and Reform Commission has explicitly designated for support. Difluorochloroethane (R142b) is the main raw material for the production of polyvinylidene fluoride. R152a is a high-performance refrigerant, aerosol propellant, and foam agent; it is an environmentally friendly green product that has emerged in recent years to protect the ozone layer. At the same time, R152a is also a major raw material for producing difluorochloroethane (R142b). PVDF boasts excellent chemical resistance, processability, as well as fatigue and creep resistance. It can be used as a corrosion-resistant material for manufacturing various mechanical products such as pumps, valves, their diaphragms, impeller blades, pipes, and gaskets, or as a corrosion-resistant lining and coating for these items. Furthermore, due to its good transparency, it can be used as corrosion-resistant sight glasses and flow meters in chemical plants. Polyvinylidene fluoride (PVDF) resin mainly refers to the homopolymer of vinylidene fluoride or a copolymer of vinylidene fluoride with a small amount of other fluorinated vinyl monomers. PVDF resin possesses the characteristics of both fluororesins and general-purpose resins. In addition to its excellent resistance to chemical corrosion, high temperatures, oxidation, weathering, and radiation, it also has special properties such as piezoelectricity, dielectricity, and thermoelectricity. It is currently the second-most-produced fluoropolymer. The applications of PVDF resin are mainly concentrated in traditional fields such as petrochemicals, construction, and machinery, as well as in emerging fields such as specialty applications, new energy, and environmental protection. Based on the polymerization method, PVDF resins can be divided into emulsion-grade resins and suspension-grade resins. Lithium battery-grade PVDF resins that require high molecular weights, as well as PVDF resins used for water treatment membranes, are primarily produced using the suspension method. The remaining resins intended for coatings, various products, and membrane coating applications, including some lithium battery-grade and water membrane-grade resins, are manufactured using the emulsion method. Lithium battery-grade PVDF resin: mainly used in the fields of new energy and consumer electronics. The rapid development in the field of lithium batteries is in line with the general trend of fuel-powered vehicles being replaced; the European Union has required its member states to ban the sale of fuel-powered vehicles by 2040. In lithium batteries, the binder is a polymer compound used to attach the electrode active material to the current collector. Its main functions are to bind and hold the active material, stabilize the structure of the electrode sheet, and also provide some buffering effect during charging and discharging. Due to its sufficient adhesion strength, moderately balanced solvent resistance, and electrochemical stability, PVDF, among various polymers, stands out as one of the preferred materials for adhesives thanks to its excellent stability and reliability. In addition to being used as an electrode binder, PVDF can also be used as a membrane coating material in lithium batteries. The function of a lithium battery separator is to separate the positive and negative electrodes and prevent electrons from passing through freely, while allowing ions in the electrolyte to move freely between them. A lithium-ion battery separator coated with PVDF is one that, based on a traditional separator, has its surface coated with PVDF material through a special processing technique. The PVDF coating layer can combine with the electrolyte in lithium-ion batteries to form a stable gel-like conductive polymer, which can significantly improve the performance of lithium-ion batteries.