Composite modified diaphragm for lithium-sulfur battery and preparation method of composite modified diaphragm

Abstract

The invention belongs to the technical field of new energy materials and devices, and particularly relates to a composite modified diaphragm for a lithium-sulfur battery and a preparation method of the composite modified diaphragm. The CNTs layers and the CeO2-x / C / rGO layers are alternately laid on the surface of one side of the commercial battery diaphragm matrix, and the CNTs layers are in contact with the diaphragm matrix. The preparation method comprises the following steps: preparing a cerium-based metal organic framework Ce-MOF and GO compound by taking trimesic acid, graphene oxide andcerous nitrate as raw materials; calcining to obtain a CeO2-x / C / rGO composite material rich in oxygen vacancies, and then alternately carrying out suction filtration on the activated CNTs and the CeO2-x / C / rGO material on the surface of one side of the commercial battery diaphragm matrix layer by layer to obtain the composite modified diaphragm for the lithium-sulfur battery. The modified diaphragmcan effectively inhibit the shuttle effect of the lithium-sulfur battery, greatly improves the capacity and rate capability of the battery, prolongs the cycle life of the battery, and is simple in manufacturing method, low in cost and suitable for large-scale production.

Description

technical field [0001] The invention belongs to the technical field of new energy materials and devices, and in particular relates to a composite modified diaphragm for lithium-sulfur batteries and a preparation method thereof. Background technique [0002] Lithium-sulfur batteries (LSBs) are a new type of secondary battery that uses sulfur as the positive electrode active material and metal lithium as the negative electrode. Benefiting from the multi-electron reaction of sulfur phase change, lithium-sulfur batteries have up to 1675mAh g -1 and 2600Wh kg -1 The theoretical specific capacity and specific energy are several times that of commercial lithium-ion batteries. In addition, sulfur is abundant, cheap, and environmentally friendly. Therefore, lithium-sulfur batteries are considered to be the most promising next-generation high-performance energy storage systems. [0003] Compared with traditional lithium-ion batteries, the multi-electron reaction characteristic of s...

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Problems solved by technology

[0003] Compared with traditional lithium-ion batteries, the multi-electron reaction characteristic of sulfur phase change not only endows lithium-sulfur batteries with advantages such as high specific energy and specific capacity, but also leads to several problems in lithium-sulfur battery systems: 1) active sulfur and discharge end The electronic and ionic insulation of the product leads to high internal resistance of the battery system, severe polarization, and low utilization of active materials; 2) Intermediate production of charge and discharge—dissolution of soluble polysulfides in the electrolyte and shuttle between positive and negative electrodes, Causes the loss of active material and self-discharge phenomenon, which greatly reduces the coulombic efficiency and cycle life of the lithium-sulfur battery; 3) The volume expansion / shrinkage of the electrode during the charging and discharging process leads to the powdering and falling off of the active material and the destruction of the electrode structure, which seriously threatens the battery life. Cycle stability and energy density; 4) A non-uniform solid electrolyte interface (SEI) is formed between the metal lithium anode and the electrolyte interface, leading to the growth of dendrites in the lithium anode, which seriously affects the safety of the battery

[0006] However, most of the currently developed composite separators are based on the principle of physical and / or chemical adsorption to limit the dissolution and shuttling of polysulfides in the liquid electrolyte during charge and discharge, and the singleness of the material will also cause incomplete functions. For The improvement of the overall performance of the battery is limited

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