High-conductivity coating diaphragm for lithium-sulfur battery as well as preparation method and application of high-conductivity coating diaphragm

Abstract

The invention discloses a high-conductivity coating diaphragm for a lithium-sulfur battery as well as a preparation method and application of the high-conductivity coating diaphragm. The preparation method comprises the following steps: immersing a polyolefin film into the first slurry; coating the positive electrode side of the polyolefin film with second slurry so as to obtain the high-conductivity coating diaphragm for the lithium-sulfur battery; wherein the preparation method of the first slurry comprises the following steps: uniformly dispersing a polymer in deionized water to obtain thefirst slurry, and the preparation method of the second slurry comprises the following steps: adding a dispersing agent into a solvent, uniformly stirring to obtain a mixed solution, uniformly mixing tannic acid and a carbon conductor, adding the mixture into the mixed solution, uniformly stirring, and sanding to obtain the second slurry. By introducing the functional layer to the surface of the polyolefin diaphragm, on one hand, generation of polysulfide is prevented, and the shuttle effect is avoided; on the other hand, the introduction of the functional layer can improve the polarity of thesurface of the diaphragm, so that the electrolyte wettability of the diaphragm is improved, uniform transmission of lithium ions in the diaphragm is facilitated, and the ionic conductivity and the lithium ion transference number of the battery are improved.

Description

technical field [0001] The invention belongs to the technical field of battery separators, and in particular relates to a high-conductivity coating separator for lithium-sulfur batteries and a preparation method and application thereof. Background technique [0002] Due to its high energy density, long service life, and no self-discharge, lithium-ion batteries are the secondary energy with the best comprehensive performance at present, and are widely used in portable electronic devices such as notebooks and mobile phones. With the application of lithium-ion batteries in electric vehicles, energy storage systems and other fields, higher requirements are put forward for the performance of lithium-ion batteries. Lithium-sulfur batteries, that is, the positive electrode (cathode cathode) is sulfur, and the negative electrode (anode anode) is a battery composed of metal lithium. Because of its high specific energy, it has become an important development direction of lithium-ion b...

AI Technical Summary

Problems solved by technology

Polyolefin separators have the characteristics of good chemical stability, high mechanical strength, low price, and high-temperature closed cells, which occupy a dominant position in commercial lithium-ion batteries, but the characteristics of the material itself, such as low surface energy and low melting point, limit the performance of the separator.

[0004] During the cycle of lithium-ion batteries, on the one hand, the electrolyte participates in the electrochemical reaction or decomposes itself, resulting in the consumption of the electrolyte; on the other hand, as time increases, the battery sealing material ages and falls off, making the battery's tightness worse , will cause the electrolyte to volatilize and leak, so that the total amount of electrolyte will continue to decrease, resulting in the attenuation of battery capacity and the reduction of service life.

Polyolefin separator has low surface energy, poor compatibility with electrolyte containing polar components, low liquid absorption rate, and poor electrolyte retention rate; coupled with continuous consumption of electrolyte, it will lead to insufficient electrolyte in the battery

Uneven distribution, electrolyte-depleted areas appear on the interface between the electrode and the diaphragm, resulting in increased interface impedance, severe polarization, and uneven current distribution. Reflected on the battery, the internal resistance of the battery increases, causing a sharp decline in battery performance