Diaphragm of lithium-sulfur battery

Abstract

The invention belongs to the technical field of lithium-sulfur batteries and in particular relates to a composite membrane of a lithium-sulfur battery. The composite membrane is a negative ion type composite multi-stage porous diaphragm and comprises a mixture of a negative charge ionization polymer and a lithium ion conduction polymer, wherein the composite multi-stage porous diaphragm has a macropore channel structure of 50 nanometers to 2 microns; micropores of 1-50 nanometers are formed in the side walls of macropore channels; the porosity is 50%-80%; macro pores account for 40%-70% of all pores and the rest pores are micropores. The composite multi-stage porous diaphragm provided by the invention has the characteristics and the beneficial effects that the macro pores of the composite membrane are good in electrolyte solution absorption and storage capacity, and the micropores are connected with the macro pores, so that the conduction of lithium ions can be facilitated; polysulfide negative ions can be excluded under the charge effect of the composite membrane material to a certain extent, so that the shuttle effect is inhibited, the loss of active substances is reduced, and the battery efficiency and stability are improved.

Description

technical field [0001] The invention belongs to the technical field of lithium-sulfur batteries, and in particular relates to a composite membrane for lithium-sulfur batteries. Background technique [0002] With the continuous development of economy and society, energy and environmental problems are becoming more and more serious. Energy conservation and emission reduction, development and utilization of new energy and renewable energy, and development of efficient and clean energy conversion and storage technologies are important issues and challenges for today's society, science and technology, and industry. In recent years, lithium batteries with metallic lithium as the negative electrode, including lithium-air batteries and lithium-sulfur batteries, have received great attention because metallic lithium has the lowest density, the most negative electrode potential, the best electronic conductivity and The highest electrochemical equivalent, its electrochemical capacity ...

AI Technical Summary

Problems solved by technology

[0004] Despite the above advantages, lithium-sulfur batteries are still far from being practical. The current main problems include: (1) The lithium metal in the negative electrode reacts with the sulfur dissolved in the electrolyte, and the elemental sulfur gradually shrinks in the positive electrode area and forms Polysulfide, polysulfide strips from the positive electrode and enters the electrolyte, and then reacts with metal lithium, the positive electrode active material is lost and eroded, and finally causes the positive electrode area to collapse; (2) During the discharge process of the lithium-sulfur battery, the formed polysulfide After the sulfides enter the electrolyte, the highly enriched polysulfides cause the viscosity of the electrolyte to increase, resulting in a decrease in the conductivity of the electrolyte and a significant drop in battery performance; (3) The operating temperature of the lithium-sulfur battery system is as high as 300-400 °C, which Requires more expensive high-temperature-resistant materials and complex preparation processes to prevent battery burnout

Since the electrolyte solution is "encapsulated" in the polymer network, the dissolution of polysulfides is inhibited, which may solve the problem of sulfur active material loss to a certain extent; however, the conductivity and strength of the gel electrolyte diaphragm are low

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