Porous MOF/CNFs composite material for lithium cathode protection

A composite material and metal lithium technology, applied in the field of lithium-ion batteries, can solve the problems of increased process complexity, low strength, and difficult production, to improve cycle stability and safety, reduce current density, and good chemical stability sexual effect

Inactive Publication Date: 2018-03-16
BEIJING INSTITUTE OF TECHNOLOGYGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, lithium metal has the following problems in actual use: (1) Lithium metal is highly active and will react with the electrolyte, forming a layer of SEI film (solid electrolyte interface film) with low strength on the lithium surface; (2) ) During the lithium deposition process, due to the volume change of the electrode, the SEI film is easily destroyed, and the exposed fresh lithium will continue to react with the electrolyte, eventually causing the irreversible loss of metal lithium and the depletion of the electrolyte; (3) due to the negative electrode surface lithium Due to the uneven distribution of ions, lithium dendrites are easy to form on the surface of lithium metal, which will not only damage the SEI film, but also pierce the battery separator, causing a short circuit in the battery and causing safety hazards
For example, the method of Li et al. requires the generation of Li 3 PO 4 The artificial SEI layer needs to be completed under an atmosphere of anhydrous, oxygen-free, and argon protection, the conditions are relatively harsh, and the production is difficult; the cost of graphene used in the method of Shin et al. NSG further increases the complexity of the process and increases the production cost; while the polyacrylonitrile (PAN) nanofiber layer of the 3D network structure in the method of Liang et al. is generated by electrospinning technology, which has a high porosity, The large pore size reduces the dispersion effect of lithium ions

Method used

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  • Porous MOF/CNFs composite material for lithium cathode protection
  • Porous MOF/CNFs composite material for lithium cathode protection
  • Porous MOF/CNFs composite material for lithium cathode protection

Examples

Experimental program
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Effect test

Embodiment 1

[0038] 1) First, the bacterial cellulose (BC) hydrogel was cut into suitable small pieces, washed with deionized water and soaked for 24 hours, and then freeze-dried to obtain BC airgel. Afterwards, the BC airgel was carbonized (2 h) at 900 °C under an argon atmosphere to obtain carbonized bacterial cellulose, namely carbon nanofibers (CNFs).

[0039] 2) Dissolve 3 mmol of zinc nitrate hexahydrate in 30 mL of methanol, then add 100 mg of carbon nanofibers, and sonicate for 20 min in an ice bath to fully disperse the carbon nanofibers. Afterwards, 12 mmol of dimethylimidazole was dissolved in 10 mL of methanol, and then added to the first solution, stirred gently to ensure that the two solutions were fully mixed, and left to stand for 24 hours. Finally, centrifugal washing (cleaning with methanol) was performed to remove impurities, and the precipitate was dried to obtain a composite material of ZIF-8 and CNFs. In this process, the ratio of dimethylimidazole to zinc nitrate he...

Embodiment 2

[0044] The porous ZIF-8 / CNFs composite material of the present invention and the binder are mixed into a uniform slurry at a weight ratio of 9:1, and coated on the surface of the lithium-ion battery separator to form a modified coating with a certain thickness. The performance of the coating can be further adjusted by adjusting the ratio of the porous ZIF-8 / CNFs composite material to the binder and the thickness of the coating. For example, the thickness of the coating can be controlled at 10-50 μm.

[0045] Then, the lithium-ion battery separator with porous ZIF-8 / CNFs composite coating was applied in the lithium-ion battery, the structure of the battery is as follows Figure 5 shown. The positive and negative electrodes of the lithium-ion battery contain electrode reactive substances. The electrolyte provides a channel for the ion transmission of the battery reaction. The Celgard2400 separator separates the positive and negative electrodes of the battery to prevent the batte...

Embodiment 3

[0054] The commercial product lithium cobaltate pole piece is used as the positive electrode, the lithium sheet is used as the negative electrode, and the diaphragm adopts the ZIF-8 / CNFs composite material coating modified diaphragm of the present invention, and the battery is composed of charging and discharging tests at a rate of 0.5C. The results are as follows: Figure 8 shown. It can be seen that the Li / LiCoO 2 The battery showed good cycle stability, and after 100 cycles at 0.5C, the specific capacity remained at 110mAh g -1 Above, the average Coulombic efficiency exceeds 98%. This test result further proves that the MOF / CNFs composite material of the present invention can improve the cycle stability of the metal lithium negative electrode.

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Abstract

The invention relates to a composite material for lithium cathode protection. The composite material is composed of porous metal-organic frameworks (MOF) and carbon nano fibers (CNFs), is used for lithium cathode protection, can effectively solve the problem that lithium dendritic crystals grow on the surface of a lithium cathode, improves the cycle stability of lithium cathode, and enhances the properties and safety of a secondary battery that is prepared from a lithium material.

Description

technical field [0001] The invention relates to a composite material composed of a porous metal-organic framework material (MOF) and a carbon nanofiber (CNFs) material, which is used for metal lithium negative electrode protection and belongs to the field of lithium ion batteries. Background technique [0002] With the development of the economy, portable electronic devices such as mobile phones, tablets, and laptops have become necessary items in people's lives, and new tools such as drones, electric balance vehicles, and electric vehicles have gradually entered the market, leading the industry trend , These popular industries urgently need rechargeable batteries with higher energy density, higher power density, longer life, and safer. [0003] Due to the heavy dependence of the current economic development on fossil energy and the lagging behind of environmental protection work, the problem of environmental pollution in China has become increasingly serious. The large-sca...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16H01M10/0525H01M10/42D01F9/16H01M50/44
CPCH01M10/0525H01M10/4235D01F9/16H01M50/431H01M50/44H01M50/449H01M50/411Y02E60/10
Inventor 王振华孙克宁王晓东
Owner BEIJING INSTITUTE OF TECHNOLOGYGY
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