Safety diaphragm used for secondary cells, and preparation method thereof

Abstract

The invention provides a safety diaphragm used for secondary cells, and a preparation method thereof. The safety diaphragm used for secondary cells possesses heat sealing performance and excellent permeability, and no bonding agent is used in the preparation method. the preparation method comprises following steps: preparation of a spinning solution, wherein at room temperature, a certain amount of a heat sensitive material is dissolved in a spinning solution as a spinning solute, and an obtained mixture is stirred to be uniform so as to obtain an electrostatic spinning solution; electrostatic spinning, wherein a high temperature resistant non-woven fabric diaphragm is taken as a base film, and electrostatic spinning of the electrostatic spinning solution onto the base film is carried out, wherein the temperature is room temperature, positive high voltage is controlled to be +5KV to +20KV, negative high voltage is controlled to be -1KV to -10KV, the left-right horizontal movement speed of a syringe is controlled to be 10 to 60mm*min<-1>, the rolling speed of a collector is controlled to be 10 to 60mm*min<-1>, the injection speed of the electrostatic spinning solution is controlled to be 0.02 to 0.5mm*min<-1>, and the collecting time is controlled to be 10 to 1200min, so that the safety diaphragm used for secondary cells is obtained via drying. The safety diaphragm used for secondary cells comprises the base film, and a spinning layer directly attached onto the base film.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a safety separator for secondary batteries and a preparation method thereof. [0002] technical background [0003] Due to the advantages of high specific energy, long cycle life and environmental friendliness, lithium-ion batteries are widely used in portable electronic products, electric vehicles and other fields. The development of a new generation of portable electronic products and electric vehicles has put forward higher requirements for the safety and energy density of lithium-ion batteries. The separator is one of the important components of the lithium-ion battery. Its function is to prevent the physical contact between the positive and negative electrodes and provide ion conductivity by absorbing the electrolyte. Although the separator does not directly participate in the battery reaction, its structure and properties determine the performance ...

AI Technical Summary

Problems solved by technology

For example, the patent CN106299219A uses polyethylene microspheres as a safety diaphragm prepared as a thermal protection layer, but due to the close packing of microspheres and the use of adhesives, it will affect the air permeability of the diaphragm, thereby affecting the ion conductivity of the diaphragm

Moreover, the use of the adhesive will also cause adverse effects such as equipment blockage during the preparation process.

[0005] In addition, due to the high thermal closure temperature of polyethylene (130°C), due to the existence of thermal inertia, the internal temperature of the battery will greatly exceed 130°C when the diaphragm is closed, causing side reactions between the positive and negative electrodes and the electrolyte.

Images