Composite diaphragm for semi-solid lithium battery and preparation method of composite diaphragm

Abstract

The invention discloses a composite diaphragm for a semi-solid lithium battery and a preparation method of the composite diaphragm. The composite diaphragm is prepared by the following steps of: dispersing and modifying a ceramic nano material by using polyvinyl alcohol with different polymerization degrees and alcoholysis degrees, and performing heat treatment in a vacuum reaction kettle to obtain polyvinyl alcohol coated ceramic nanowire slurry; pMMA and PVDF are uniformly dissolved in a mixed solvent through heat treatment in a vacuum reaction kettle to prepare a membrane casting solution, and a substrate or a polyolefin membrane substrate is directly coated with the membrane casting solution to form a membrane; and finally, coating the polyvinyl alcohol coated ceramic nanowire slurry on a polymer base membrane to obtain the composite diaphragm for the semi-solid lithium battery. The composite diaphragm has high liquid retention property, high ionic conductivity, high flexibility and high mechanical strength. The preparation method disclosed by the invention is simple to operate, easy to control and good in universality, and a series of complicated operations such as subsequent addition of a pore-forming agent or solvent phase separation are not needed.

Description

technical field [0001] The invention belongs to the technical field of battery diaphragms, and in particular relates to a composite diaphragm for a semi-solid lithium battery and a preparation method thereof. Background technique [0002] At present, lithium batteries usually add liquid electrolyte to improve the conductivity of the electrolyte. If the liquid electrolyte content is too high, the liquid electrolyte will leak from the electrode mixture layer, which will corrode electronic appliances, and in severe cases, it may cause lithium-ion batteries to burn. Or explosion, there is a greater potential safety hazard. However, all-solid-state lithium batteries have defects such as low room temperature conductivity, which are far from meeting the needs of practical applications. In contrast, semi-solid lithium batteries can fully solve the problems of poor ion conduction and easy leakage, and the polymer gel framework can bind the liquid electrolyte in it, reducing free sol...

AI Technical Summary

Problems solved by technology

[0003] At present, there have been researches applied to separators of semi-solid lithium batteries, but the existing semi-solid battery separators still have relatively high viscosity and low dielectric constant, and the crystallinity of the finished film is still high, allowing lithium ions to freely The proportion of mobile amorphous regions is small, making it difficult for the ionic conductivity of polymer electrolytes to meet practical needs at room temperature

For example, PVDF or PVDF-HFP can be used as a semi-solid battery separator due to its excellent film-forming properties, but because of the high crystallinity of a single PVDF or the side-reaction of PVDF-HFP framework with lithium metal to generate LiF, its ionic conductivity is not good. people are satisfied

PMMA has the advantages of excellent liquid absorption rate and good interfacial compatibility with the negative electrode, but its self-supporting property is poor, which cannot meet the needs of physical barrier between positive and negative electrodes.

[0004] In addition, there are also existing ceramic diaphragms modified as semi-solid battery diaphragms, but their flexibility, poor processability, and poor compatibility with battery electrodes are far from meeting the requirements for the use of semi-solid lithium battery composite diaphragms.

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