One of The Four Major Materials of Lithium Batteries – Separator

Lithium-ion battery is the representative of modern high-performance battery. It consists of four main parts: cathode material, anode material, separator, and electrolyte. Among them, the separator is a thin film with a microporous structure, which is the key inner layer composed of the most technical barrier in the lithium-ion battery industry chain. Although it does not participate in the electrochemical reaction in the battery, the key properties such as capacity, cycle performance and charge and discharge current density of the battery are directly related to the separator.

The separator is an important component of lithium-ion batteries and is an important component for supporting lithium-ion batteries to complete the electrochemical process of charge and discharge. It is located between the positive and negative electrodes inside the battery, ensuring the passage of lithium ions while blocking electron transport. The performance of the separator determines the interface structure and internal resistance of the battery, which directly affects the capacity, cycle and safety performance of the battery. The separator with excellent performance plays an important role in improving the overall performance of the battery.

In a lithium battery, after the separator absorbs the electrolyte, the positive and negative electrodes can be isolated to prevent short circuits, but at the same time, lithium-ion conduction is allowed. In the case of overcharging or temperature rising, the separator also has high-temperature self-closing performance to block current conduction and prevent the explosion. Not only that, but lithium battery separators also have high strength, fire resistance, chemical resistance, acid and alkali corrosion resistance, good biocompatibility, non-toxic and so on.

The micropore manufacturing technology is the core of the lithium battery separator process. According to the difference of micropore pore formation mechanism, the membrane process can be divided into dry method and wet method.

The performance of the separator product is influenced by both the matrix material and the manufacturing process. The stability, consistency, and safety of the separator have a decisive influence on the discharge rate, energy density, cycle life and safety of the lithium battery. Compared with the dry method, the wet method is more in terms of thickness uniformity, mechanical properties (tensile strength, puncture strength), gas permeability, physical and chemical properties (wettability, chemical stability, safety). It is excellent, beneficial to the liquid absorption and liquid retention of the electrolyte and improves the charge, discharge and circulation ability of the battery, and is suitable for high-capacity batteries. From the perspective of product force, wet method composite performance is stronger than the dry method.

Ceramic coated separator 

The ceramic particle coated separator is based on a base film, and is coated with a layer of Al2O3, SiO2, Mg(OH)2 or other inorganic ceramic particles having excellent heat resistance, and is closely bonded to the substrate after being treated by a special process. The combination of the flexibility of the organic substance and the thermal stability of the inorganic substance improves the high-temperature resistance, heat shrinkage resistance and puncture strength of the separator, thereby improving the safety performance of the battery. It is understood that the ceramic composite layer can solve the thermal runaway caused by the heat shrinkage of PP and PE separator, thereby causing the safety of burning and explosion of the battery; on the other hand, the ceramic composite separator has good infiltration and absorption of the electrolyte and the positive and negative materials. The ability to protect the liquid greatly improves the service life of the battery. In addition, the ceramic-coated separator neutralizes a small amount of hydrofluoric acid in the electrolyte to prevent battery swelling.