Composite membrane for lithium ion batteries and preparation method thereof

Abstract

The invention discloses a composite membrane for lithium ion batteries and a preparation method thereof, including a ceramic coating modification method and a ceramic lithium battery membrane. The ceramic protective layer is mainly prepared from a ceramic-adhesive mixture subjected to graft modification by a sodium-sulfonate / sodium-carboxylate-group-containing anionic surfactant. The grafting is completed by using a grafting-to process under the action of a dehydrating agent; the grafting ratio of the ceramic is higher; the high-temperature-resistant large-surface-area nano ceramic is introduced to the conventional PP (polypropylene) membrane surface, the insulativity and electrolyte wettability of the modified ceramic membrane are greatly enhanced; and the membrane has excellent high-temperature heat stability especially at the high temperature of 130 DEG C, 150 DEG C and 180 DEG C. The lithium battery composite membrane avoids the thermal shrinkage of the convention membrane, thereby avoids the thermorunaway in the battery due to thermal shrinkage, and further enhancing the safe reliability of the lithium ion battery.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion batteries, and in particular relates to a composite separator for lithium-ion batteries and a preparation method thereof. More specifically, the invention relates to the inclusion of anionic surfactants and the modification and coating of ceramics by grafting, thereby improving A method of dispersion and adhesion of ceramics. Background technique [0002] Lithium-ion batteries have been widely used as power sources for various mobile devices since their commercialization due to their high energy density, high operating voltage, no memory effect, and long cycle life. And it is very likely to become the most important power supply system in the field of energy storage and electric vehicles. However, with the large-scale application of lithium-ion batteries, battery safety issues have become increasingly prominent. [0003] One of the key factors affecting the safety of lithium-ion power batteri...

AI Technical Summary

Problems solved by technology

However, there are still two shortcomings in the ceramic grafting modification method: one is that the selected monomer has a large steric hindrance and the grafting rate is low; the other is that the process operation is complicated, which is not conducive to industrial production. Ion exchange was also carried out after the neutralization, and the product loss would be caused during the ion exchange process, further reducing the yield

The steric hindrance of the monomer is specifically reflected in the steric hindrance of the benzene ring in sodium benzenesulfonate (also known as the stereo effect: mainly refers to the steric hindrance caused by certain atoms or groups in the molecule being close to each other and the deviation from the normal bond angle. The tension in the molecule) is relatively large, that is, the sodium benzenesulfonate derivatives all contain rigid benzene rings with high tension. When such reagents attack Al as a nucleophile 2 o 3 When the surface hydroxyl group, due to the influence of the larger steric hindrance of the benzene ring connected by the sulfonic acid group, the reaction rate of the two reactants is greatly reduced, thus reducing the Al 2 o 3 The number of reactions between hydroxyl groups and sodium sulfonate derivatives on the surface of ceramics, thereby reducing the grafting rate of ceramics

Al on ceramic surface 2 o 3 Only some of the hydroxyl groups in the ceramics are successfully grafted and covered, and most of the free hydroxyl groups fail to react with the surface active monomers to be grafted and covered. When the ceramics are dispersed, there will still be intramolecular hydrogen bonds of the free hydroxyl groups. resulting in a large amount of ceramic agglomeration

The result must be that the problem of difficult dispersion of ceramics has not been solved fundamentally. On the other hand, due to the low grafting rate, the degree of improvement of the hydrophilic and lipophilic properties of the hydroxyl groups on the ceramic surface is not obvious.

In the later stage of bonding with polyolefin base film, problems such as poor adhesion and easy peeling off of the ceramic coating will occur

Images