Production method of boron nitride coated diaphragm of lithium-sulfur battery

Abstract

The invention relates to a production method of a boron nitride coated diaphragm of a lithium-sulfur battery. The diaphragm is produced from a commercial polypropylene diaphragm, two sides of the diaphragm are uniformly covered with hexagonal boron nitride, and the characteristics of hexagonal boron nitride 'white graphite' are used, so lithium ions are allowed to pass, shuttle of polysulfide anions is obstructed, a reaction of a lithium negative electrode with the polysulfide anions is inhibited, formation of lithium dendrites, lithium sulfide precipitate and fixed lithium is prevented, the capacity, the coulombic efficiency and the cycle stability of the lithium-sulfur battery are improved, the growth of the negative electrode metal dendrite in the cycle process is effectively inhibited, and the safety of the battery is improved. The method has the advantages of simple process route and clear purpose, and the produced diaphragm has multiple functions, and can greatly overcome disadvantages of present technologies.

Description

technical field [0001] The invention relates to the field of lithium-ion batteries, in particular to a multifunctional boron nitride-coated separator for lithium-sulfur batteries and a preparation method thereof. Background technique [0002] Since the Italian Alessandro Volta invented the world's first battery in 1799, after more than 200 years of development, the types and output of chemical power sources have been continuously updated and expanded, and the occasions and application ranges are also increasing. It is one of the essential sources of energy and power in production activities. With the rapid development of space technology, mobile communications, missiles, aerospace and other fields, as well as the increasing concern of modern people on energy crisis and environmental protection issues, the research and development of lithium secondary batteries with high energy density has aroused widespread interest. The main reason for the low energy density of existing se...

AI Technical Summary

Problems solved by technology

First of all, a large amount of polysulfide anions will dissolve and diffuse in the electrolyte, which will lead to the loss of the active material of the positive electrode. At the same time, it will shuttle the diaphragm many times to react with the discharge product of the negative electrode, causing the "shuttle effect" and causing the battery to overcharge. The coulombic efficiency and cycle life of the battery; secondly, the discharge product lithium sulfide will precipitate from the organic electrolyte and cover the surface of the sulfur positive electrode to form an insulating lithium sulfide film, thereby hindering the discharge between the electrolyte and the electrode active material reaction

[0006] (2) The chemical properties of metal lithium are very active, and it is easy to react with the electrolyte solution, and an SEI film is formed on the surface of the electrode material, resulting in an increase in the polarization resistance of the electrode; the dissolved high-polymer polysulfide will diffuse to the lithium surface and form a self-reaction with lithium. The discharge corrosion reaction leads to irreversible capacity loss of the active material; at the same time, the reduction product of some oligomerization states diffuses back to the positive electrode under the action of the concentration gradient for re-oxidation, resulting in the shuttle effect and reducing the electric Coulombic efficiency

However, it is worth noting that the copper foil-lithium-boron nitride "sandwich structure" proposed in this article uses copper as a current collector to improve the lithium negative electrode, and does not investigate the dendrites and deposition when metal lithium is used as the negative electrode. At the same time, the chemical vapor deposition and electrochemical deposition methods used in the article are relatively cumbersome, and the experimental conditions are relatively harsh. Such a complicated preparation method is not conducive to popularization and universalization, and still needs further improvement

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