A separator, its preparation method and an electrochemical device comprising the separator

Abstract

The present application relates to the field of energy storage materials, and specifically relates to an isolation film, its preparation method and an electrochemical device including the isolation film. An isolation film includes a base material and an inorganic layer provided on at least one side of the base material. The base material is a porous base material. The inorganic layer is a dielectric layer that does not contain a binder. The thickness of the inorganic layer is 20nm ~ 2000nm, the ratio M1 / M2 of the mass M1 of the inorganic layer to the mass M2 of the substrate satisfies 0.05≤M1 / M2≤7.5, and the interface peeling force between the inorganic layer and the substrate is not less than 30N / m. The isolation film of this application effectively improves the interfacial wettability and thermal shrinkage resistance of the isolation film by arranging an ultra-thin inorganic layer without binder on the surface of the porous substrate, and ensures that it has a certain mechanical strength and avoids the problem of The problem of reduced mechanical strength and clogging of the pores of the substrate caused by falling off improves the safety and cycle life of the battery. By controlling the range of M1 / M2 and interface peeling force, the energy density is also higher.

Description

technical field [0001] The present application relates to the field of energy storage, in particular, to an isolation membrane, a preparation method thereof, and an electrochemical device including the isolation membrane. Background technique [0002] In the internal structure of the battery, the separator is a key component, usually a porous polymer film, which has the characteristics of electronic isolation and ion conduction, and is used to ensure the normal transmission of ions between the positive electrode and the negative electrode without short circuit. In recent years, in order to improve the problems of high thermal shrinkage and poor wettability with electrolyte of a single polymer separator, a composite separator coated with a ceramic coating on the surface of a polymer substrate has gradually become a key technology for improving battery safety performance. . However, there are still some problems in this composite separator, which needs further development and...

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Problems solved by technology

However, there are still some problems in this composite separator, which needs further development and research

[0003] The above problems can be effectively improved by modifying the surface of polymer substrates by mixing inorganic particles and binders to form organic / inorganic composite coatings. However, due to process limitations and technical effect requirements, the coating thickness is difficult to achieve nanoscale. In addition, the bonding between the inorganic particles and the polymer substrate is mainly by the binder, and the bonding force of different regions is significantly affected by the distribution of the binder, and it is easy to cause ceramic layer damage during the coating process, long-term cycle or battery abuse. Surface cracks and aging, changes in porosity, shedding of ceramic particles, etc., resulting in poor ion-conducting performance, and even easy to cause safety problems in severe cases

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