The production process of high-performance lithium 18650 li ion battery separators is complex

　　The production process of high-performance lithium 18650 li ion battery separators is complex. In our lives, high-performance lithium-ion batteries are often used. The performance of separator products is affected by the base material and manufacturing process. The stability, consistency, and safety of the separator have a decisive impact on the discharge rate, energy density, cycle life, and safety of lithium-ion batteries.

　　The production process of high-performance lithium 18650 li ion battery separators is complex

　　Lithium-ion batteries are representatives of modern high-performance batteries and are composed of four main parts: positive electrode material, negative electrode material, separator, and electrolyte. Among them, the separator is a thin film with a microporous structure. It is the key inner component with the most technical barriers in the lithium 18650 li ion battery industry chain. It plays the following two main roles in lithium batteries: separating the positive and negative electrodes of lithium batteries. , to prevent the positive and negative electrodes from contacting and forming a short circuit; the micropores in the film can allow lithium ions to pass through, forming a charge and discharge circuit.

　　High-performance lithium batteries require separators with uniform thickness and excellent mechanical properties (including tensile strength and puncture resistance), breathability, and physical and chemical properties (including wettability, chemical stability, thermal stability, and safety). It is understood that the excellence of the separator directly affects the capacity, cycle capacity, safety performance and other characteristics of lithium batteries. Excellent separators play an important role in improving the overall performance of the battery.

　　The many characteristics of lithium battery separators and the difficulty in balancing their performance indicators determine that the technical barriers to its production process are high and its research and development is difficult. The separator production process includes raw material formula and rapid formula adjustment, micropore preparation technology, independent design of complete sets of equipment, and many other processes. Among them, micropore preparation technology is the core of the lithium battery separator preparation process. According to the difference in micropore formation mechanism, the separator process can be divided into two types: dry method and wet method.

　　Production process principle of lithium 18650 li ion battery separator

　　The production process of lithium 18650 li ion battery separators is mainly divided into dry process and wet process. The main steps and principles of dry and wet processes are:

　　1. Dry method - first melt, extrusion and blowing the polyolefin resin to form a crystalline polymer film, then perform crystallization heat treatment and annealing operations to obtain a highly oriented film structure, and then stretch it at high temperature , test the crystallization cross-section separation to form a porous structure battery separator. The dry process can also be divided into uniaxial stretching and biaxial stretching.

　　2. Wet method - traditional wet method preparation is mainly based on phase inversion method, and in recent years, TIPS thermally induced phase separation method is mainly used. 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 lower the solution temperature to cause solid-liquid phase separation of the mixture. Or liquid-liquid separation, extracting and removing small molecule chemical diluents to form a porous membrane of thermoplastic and crystalline polymers.

　　The main characteristics of the wet process are high cost, large investment, high equipment requirements, long construction and production cycle, large 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.

　　Lithium-ion batteries are considered to be one of the most promising energy storage methods due to their high energy density. They have been commercially applied in the field of electric vehicles. Continuing to improve the energy density of lithium-ion batteries is still the unremitting pursuit of researchers. At present, the capacity of lithium-ion batteries is mainly determined by the capacity of the cathode material. Finding cathode materials with high discharge capacity and stability is the key to improving the energy density of lithium-ion batteries.

　　In the structure of lithium batteries, the battery separator is one of the key inner components and a high value-added material with high technical barriers, accounting for approximately 20%-30% of the cost of lithium batteries. The quality of the separator determines the interface structure, internal resistance, etc. of the battery, which directly affects the battery capacity, cycle, safety performance and other characteristics. Excellent separators play an important role in improving the overall performance of the battery.

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