CR2430 battery

Production process of CR2430 battery separator

Production process of CR2430 battery separator, principle of lithium battery separator production process. As one of the four core materials of lithium battery, separator is an important part that determines the performance, safety and cost of lithium battery. The production process of lithium battery separator is divided into two categories: dry production process and wet production process. The dry production process is further divided into unidirectional stretching process and bidirectional stretching process. Production process of CR2430 battery separator The production process of CR2430 battery separator is mainly divided into dry stretching and wet stretching. The many characteristics that lithium battery separator needs to have put forward special requirements for its production process, and the production process includes raw material formula and rapid formula adjustment, micropore preparation technology, and complete set of equipment independent design. The dry unidirectional stretching process is to prepare a low-crystallinity, highly oriented polypropylene or polyethylene film by producing hard elastic fibers, and obtain a high-crystallinity film during high-temperature annealing. This film is first stretched at low temperature to form micro defects, and then the defects are pulled apart at high temperature to form micropores. At present, more than one-third of China's production capacity uses dry double-stretching process, and the products occupy a large proportion in the low- and medium-end markets. The wet process, also known as phase separation or thermal phase separation, is a process in which liquid hydrocarbons or some small molecules are mixed with polyolefin resins, heated and melted to form a uniform mixture, then cooled for phase separation, pressed to obtain a membrane, and then heated to a temperature close to the melting point, biaxially stretched to orient the molecular chains, and finally kept warm for a certain period of time, and the residual solvent is washed away with volatile substances to prepare microporous membrane materials that are interconnected. The wet process can not only prepare microporous membrane materials that are interconnected, but also produce lithium battery separators with high longitudinal and transverse strength. At present, the wet process is mainly used to produce single-layer lithium battery separators. Principle of lithium battery separator production process 1. Dry process - first melt, extrude and blow the polyolefin resin to form a crystalline polymer film, then perform crystallization heat treatment and annealing operations to obtain a highly oriented film structure, then stretch it at high temperature, test the crystal cross-section separation, and form a porous structure battery separator. The dry process can also be divided into uniaxial stretching and biaxial stretching. 2. Wet process - Traditional wet process preparation is mainly based on phase inversion method, and in recent years, TIPS thermal phase separation method has been the main method. The principle is to mix crystalline polymers, thermoplastic polymers and small molecule chemical diluents with high boiling points (such as paraffin oil) to form a homogeneous solution at high temperature, and then reduce the solution temperature to make the mixture undergo solid-liquid phase separation or liquid-liquid separation. After the small molecule chemical diluent is extracted and removed, a porous diaphragm of thermoplastic and crystalline polymers is formed. The main characteristics of the wet process of lithium battery diaphragms are high cost, large investment, high equipment requirements, long construction and production cycle, and high energy consumption during the production process, and the use of organic solvents. However, the wet process can better control the pore size, distribution and porosity, so it is generally used to manufacture high-end films. The raw material of the dry process is generally PP, while the raw material of the wet process is generally PE. Generally speaking, the melting temperature of PP is around 170°C, and the melting temperature of PE is around 140°C. Therefore, although the diaphragm produced by the wet process is thinner, the lower melting temperature makes the diaphragm easy to shrink at high temperature, causing battery short circuit and battery safety cannot be guaranteed. Coating a layer of inorganic nanoparticles or high-temperature resistant organic chemicals on the surface of the diaphragm can improve the high-temperature safety performance of the diaphragm, which can well make up for this defect of the wet process. Dry single-drawing process flow of lithium battery diaphragm Feeding: PE or PP and additives and other raw materials are pre-treated according to the formula and transported to the extrusion system. Casting: The pre-treated raw materials are melted and plasticized in the extrusion system and then extruded from the die head. The melt is cast to form a base film with a specific crystal structure. Heat treatment: The base film is heat-treated to obtain a hard elastic film. Stretching: The hard elastic film is cold-stretched and hot-stretched to form a nanoporous membrane. Slitting: The nanoporous membrane is cut into finished films according to customer specifications. Wet asynchronous stretching process Feeding: PE, pore-forming agent and other raw materials are pre-treated according to the formula and transported to the extrusion system. Casting: The pretreated raw materials are melted and plasticized in a twin-screw extruder system and then extruded from the die head to form a cast thick sheet containing a pore-forming agent. Longitudinal stretching: The cast thick sheet is stretched longitudinally. Transverse stretching: The cast thick sheet after longitudinal stretching is stretched transversely to obtain a base film containing a pore-forming agent. Extraction: The base film is extracted with a solvent to form a base film without a pore-forming agent. Shaping: The base film without a pore-forming agent is dried and shaped to obtain a nanoporous membrane. Cutting: The nanoporous membrane is cut into finished membranes according to the customer's specifications. The performance of the diaphragm product is affected by the base material and the manufacturing process. The stability, consistency and safety of the diaphragm have a decisive influence on the discharge rate, energy density, cycle life and safety of the lithium battery. . From the perspective of product strength, the comprehensive performance of the wet-process diaphragm is stronger than that of the dry-process diaphragm.

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