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

A composite modification, lithium-sulfur battery technology, used in lithium batteries, battery pack parts, non-aqueous electrolyte batteries, etc., can solve the problems of single function, damage, loss of active materials, etc. performance, solve the shuttle effect, and promote the effect of efficient conversion

Pending Publication Date: 2020-11-20
HEFEI UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

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

Method used

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

Examples

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Embodiment 1

[0037] This embodiment provides a composite modified diaphragm for lithium-sulfur batteries, the modified diaphragm includes two parts: a diaphragm base and a modified layer laid on one side of the diaphragm base. The separator substrate is a common commercial battery separator substrate, and the modified layer includes 2 to 4 layers of CNTs and 1 to 3 layers of CeO 2-x / C / rGO layer (CeO 2-x / C / rGO layer is one layer less than CNTs layer), CNTs layer and CeO 2-x / C / rGO layers are laid alternately on one side of the membrane matrix and the CNTs layer is in contact with the membrane matrix.

[0038] The diaphragm substrate has a planar structure and a large number of through holes, which can be polypropylene (PP) porous membrane, polyethylene (PE) porous membrane, polyethylene / polypropylene composite porous membrane, polyimide diaphragm, polyethylene terephthalate One of the diester-based non-woven separators. In this example, the separator substrate was a commercially availa...

Embodiment 2

[0061] The preparation method of this embodiment is the same as that of Example 1, except that step (1) is not carried out, and other implementation conditions remain unchanged.

[0062]Compared with Example 1, the electrochemical properties of the lithium-sulfur battery assembled with the modified separator prepared in this example, such as capacity, rate and cycle stability, are all lower compared with Example 1: initial discharge capacity at 0.5C After 200 cycles of charge and discharge, the specific capacity drops to 726mAh / g, and the capacity retention rate is 68.9%. The discharge capacity of the first cycle of 1C cycle charge and discharge is 1055mAh / g, and the discharge capacity of the battery after 500 cycles of long cycle is 563mAh / g, the capacity retention rate is 53.4%; in addition, the rate performance is also reduced.

Embodiment 3

[0064] The preparation method of this embodiment is the same as that of Example 1, except that in step (4), the CNTs layer and CeO are alternately suction-filtered on the surface of the commercial battery PP separator (Celgard2500) substrate. 2-x The layers of / C / rGO layers are 4 layers and 3 layers respectively, CNTs and CeO 2-x The mass ratio of / C / rGO was 2:1, the vacuum drying temperature was 50 °C, and other implementation conditions were kept unchanged.

[0065] Compared with Example 1, the area loading of the surface modification layer of the modified diaphragm prepared in this example is 0.25 mg / cm 2 , with a thickness of 9 μm. Compared with Example 1, the electrochemical properties of the lithium-sulfur battery assembled with the modified diaphragm prepared in this example, such as capacity, rate and cycle stability, are reduced: the initial discharge capacity at 0.5C is 1051mAh / g, 200 cycles After charging and discharging, the specific capacity drops to 738mAh / g, a...

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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...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16H01M2/14H01M10/052
CPCH01M10/052Y02E60/10
Inventor 刘家琴吴玉程吴迪张琪闫健
Owner HEFEI UNIV OF TECH
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