A constitution method of a lithium ion battery diaphragm surface supermolecule membrane

Abstract

The invention relates to a constitution method of a lithium ion battery diaphragm surface supermolecule membrane. Organic and inorganic constitution units with high thermal stability, high mechanical strength and hydrophilic polar functional groups are adopted. An organic-inorganic composite supermolecule membrane is alternatively assembled onto the polyolefin diaphragm surface and the pore inner surface by a layer-by-layer self-assembly method based on molecule interfaces. By fine regulation and control of the thickness, the constitution, the structure and surface characteristics of the supermolecule membrane at the molecule level, the thermal stability, mechanical strength and the ionic conductivity of the diaphragm are improved, thus enhancing the safety and electrochemical properties of the lithium ion battery.

Description

technical field [0001] The invention relates to a layer-by-layer self-assembly method and a supramolecular film on the surface of a lithium ion battery diaphragm prepared by the method. The supramolecular film used on the surface of the lithium battery diaphragm can improve the thermal stability, mechanical properties and liquid holding rate of the diaphragm. Background technique [0002] As one of the key inner components of lithium-ion batteries, the diaphragm can isolate the positive and negative electrodes to prevent short circuit, while allowing the conduction of lithium ions; when overcharging or temperature rises, the diaphragm blocks current conduction by closing the pores to prevent explosion. The performance of the separator determines the retention of the electrolyte, the size of the internal resistance of the battery, and the composition of the battery interface structure, which directly affects the safety performance and key characteristics of the l...

AI Technical Summary

Problems solved by technology

However, the coating applied on the surface of the diaphragm by the coating method is often relatively thick, and the diaphragm forms a similar "sandwich" structure. In addition, the use of too thick a coating and an adhesive can easily cause the pores of the diaphragm to be blocked, although the follow-up usually adopts the same method. The transfer method forms a microporous structure in the surface coating of the separator, but the pore permeability of the separator decreases, which easily increases the resistance of lithium ion migration and negatively affects the electrochemical performance of the battery.

For example, Lee et al. (Journal of Power Sources, 2011, 196: 6716-6722.) used the coating method to coat SiO on the surface of the PE separator. 2 / PVDF-HFP coating improves the thermal stability and liquid holding rate of the separator, but because the thickness of the separator (30 μm) after the coating is greatly increased compared with the original PE film (20 μm), the ionic conductivity decreases instead , resulting in a decrease in the rate discharge performance of the battery

[0005] It can be seen that the thickness and pore structure of the separator have a direct impact on the performance of the battery. How to adopt effective methods to better design and control the structure of the functional coating on the surface of the separator (thickness, pore structure, surface characteristics, etc.) It is still a challenge to effectively maintain the original uniform pore structure and pore penetration of polyolefin separators while maintaining excellent mechanical properties, thermal stability, and liquid holdup.

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