Composite coating lithium-ion battery separator and preparation method thereof

Abstract

The invention relates to a composite coating lithium-ion battery separator. The composite coating lithium-ion battery separator is composed of a base film, an aramid fiber coating coated on one side of the base film and a PVDF coating coated on the other side of the base film; the aramid fiber coating is obtained by an aramid fiber sizing agent after coating, soaking and drying, and the thickness of the coating is 0.5-4 microns; the PVDF coating is obtained by a water-based PVDF sizing agent after coating and drying, and the thickness of the coating is 0.1-2 microns. The invention also provides a preparation method of the separator. According to the composite coating lithium-ion battery separator and the preparation method thereof, the separator has the characteristics that the aramid fiber coating is good in thermal performance and mechanical performance and the PVDF coating has good wettability and liquid retention property for electrolytes, can effectively adhere batteries and pole pieces and is little in environmental pollution, and is beneficial for preparing lithium-ion batteries with longer cycle life and higher safety. Tests indicate that the separator has good air permeability, liquid absorption rate, thermal contraction and tensile strength, so that the cycle life of the batteries can be obviously prolonged by using the lithium-ion batteries prepared by the separator.

Description

technical field [0001] The invention relates to a lithium ion battery technology, in particular to an aramid fiber and PVDF composite coating lithium ion battery diaphragm and a preparation method thereof, belonging to the field of battery technology. Background technique [0002] The composition of lithium-ion batteries includes positive electrodes, negative electrodes, separators and electrolytes. As one of the four major materials of lithium-ion batteries, the separator is a key inner layer component in lithium batteries, although it does not participate in the electrochemical reactions in the battery. Key properties such as battery capacity, cycle performance, and charge-discharge current density are directly related to the separator, and the safety of the separator is an important factor affecting the safety of lithium-ion batteries. At present, the large-scale commercial lithium-ion battery diaphragm is mainly made of polyolefin. As the performance requirements of lith...

AI Technical Summary

Problems solved by technology

The existing coating technology for PVDF separators of lithium-ion batteries generally adopts an oily coating process, and acetone is mostly used as a solvent in the oily coating process. Acetone is flammable, explosive, and has great harm to the human body. Unsafe factors; at the same time, acetone is the raw material for making methamphetamine, and its use is strictly controlled by relevant departments

In addition, for coatings made of oily solvents such as acetone, after surface coating of the diaphragm, due to the good compatibility between the oily slurry and the material of the diaphragm, the slurry will penetrate into the micropores of the base film, resulting in a large loss of air permeability. It is easy to cause the diaphragm to block holes, affect the performance of the battery, reduce the effective use space of the positive and negative materials in the battery, and limit the capacity and performance of the battery

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