Coated diaphragm for ternary lithium ion battery, and preparation method thereof

Abstract

The invention discloses a coated diaphragm for a ternary lithium ion battery, and a preparation method thereof. The coated diaphragm comprises a diaphragm substrate, a ceramic / graphene composite coating and a PVDF coating, two sides of the diaphragm substrate are respectively coated with the ceramic / graphene composite coating and the PVDF coating, the ceramic / graphene composite coating correspondsto a battery positive electrode, and the PVDF coating corresponds to a battery negative electrode. The positive electrode side is the ceramic / graphene composite coating, so no shrinkage of the coateddiaphragm at a high temperature is ensured, and short circuit, explosion and other safety hazards of the coated diaphragm are avoided; the negative electrode side is the PVDF coating, so the internalheat conduction performance of the battery is enhanced to a certain degree, the high-temperature storage performance of the battery is improved, the wettability and the liquid retention property of the coated diaphragm are increased, and the coated diaphragm and an electrode sheet are bonded to inhibit structural collapse of the negative electrode in the charging and discharging process; and thesuperposition of the two coatings greatly improves the safety, the cycle performance and the rate performance of the ternary lithium ion battery material are greatly improved, and the large-scale application of the coated diaphragm on a power battery is promoted.

Description

technical field [0001] The invention relates to the technical field of preparation of lithium-ion battery separators, in particular to a coated separator of a ternary lithium-ion battery and a preparation method thereof. Background technique [0002] With my country's continuous emphasis on the development of new energy vehicles, how to effectively increase the energy density of power batteries is imminent. At present, the improvement of the energy density of power lithium-ion batteries is mainly solved by using a ternary positive electrode (NCM / NCA) with a silicon-carbon negative electrode system. Although this system has a high energy density, due to the poor thermal stability of the ternary material, in Thermal decomposition will occur at around 200°C to generate oxygen, which will react with electrolyte or carbon materials to cause combustion and explosion. In addition, due to the characteristics of ternary lithium-ion batteries that are easy to decompose at high tempera...

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Problems solved by technology

[0003] In order to solve this problem, people's main work in recent years is divided into the following two aspects: one is to add various additives to the electrolyte to improve the interfacial stability of the material and inhibit its decomposition, but the inhibitory effect of the electrolyte is limited; the other The separator is coated with ceramics to enhance the mechanical strength and heat resistance of the separator, prevent its shrinkage from causing short circuits, effectively improve the thermal safety and stability of the battery, and improve the performance of the ternary lithium-ion battery to a certain extent. The thermal effect improves its thermal stability, but due to the low thermal conductivity of ceramic materials, the temperature in a local area is not easy to spread, and it is easy to generate heat accumulation, resulting in insufficient safety performance and cycle performance of the battery

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