Composite diaphragm comprising PVDF coating with lamellar structure and preparation method thereof, and application of composite diaphragm comprising PVDF coating with lamellar structure

A technology of composite diaphragm and sheet structure, which is applied in the direction of structural parts, electrical components, electrochemical generators, etc., can solve the problems of affecting the air permeability of composite diaphragms, affecting the transmission performance of lithium ions, and increasing the internal resistance of lithium-ion batteries. Facilitating transfer, ease of implementation, improved cycling and rate performance effects

Active Publication Date: 2019-08-16
BEIJING NORMAL UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

The good air permeability of the composite separator is the prerequisite for the free transmission of ions during the charging and discharging process of the lithium-ion battery. However, if the content of the binder is too high, it is easy to block the pores of the base layer separator and affect the air permeability of the composite separator, thereby affecting the transmission of lithium ions. Performance, resulting in increased internal resistance of lithium-ion batteries, poor rate performance and other deficiencies

Method used

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  • Composite diaphragm comprising PVDF coating with lamellar structure and preparation method thereof, and application of composite diaphragm comprising PVDF coating with lamellar structure
  • Composite diaphragm comprising PVDF coating with lamellar structure and preparation method thereof, and application of composite diaphragm comprising PVDF coating with lamellar structure
  • Composite diaphragm comprising PVDF coating with lamellar structure and preparation method thereof, and application of composite diaphragm comprising PVDF coating with lamellar structure

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preparation example Construction

[0058] [Preparation Method of Composite Separator]

[0059] As mentioned above, the present invention also provides a preparation method of the above-mentioned composite diaphragm, said method comprising the steps of:

[0060] 1) Disperse and swell PVDF powder and / or emulsion (a1) in a mixed aqueous solution of a dispersant and a plasticizer to prepare an aqueous dispersion containing PVDF powder and / or emulsion swollen by a plasticizer;

[0061] 2) The aqueous dispersion of step 1) is coated on one or both sides of the porous base film containing holes, and the PVDF powder and / or emulsion swelled by the plasticizer are softened under the action of gravity on the porous base due to plasticization and softening. The surface of the membrane becomes a sheet structure; a PVDF coating containing a sheet structure is formed during the drying process, that is, the composite diaphragm is prepared.

[0062] In a solution of the present invention, said step 1) includes the following st...

Embodiment 1

[0084]1) Preparation of aqueous dispersion containing PVDF powder and / or emulsion swollen by plasticizer: stir and disperse the dispersant sodium polymethacrylate and plasticizer N-methylpyrrolidone with water, then add PVDF powder and / or the emulsion (a1) to disperse and fully swell, and then add a binder to prepare an aqueous dispersion containing PVDF powder and / or emulsion swollen by a plasticizer. Wherein, the mass percentage of water is 83wt%; the mass percentage of dispersant is 0.5wt%; the mass percentage of plasticizer is 1.5wt%; the mass percentage of PVDF powder and / or emulsion (a1) is 10wt%; the mass percentage of the binder is 5wt%.

[0085] 2) Preparation of composite diaphragm: The above-mentioned aqueous dispersion is coated on the surface of a 20 μm dry-process biaxially stretched polypropylene diaphragm by means of micro-gravure transfer to obtain a polypropylene composite film containing PVDF with a lamellar structure. Diaphragm (see figure 1 ), where the ...

Embodiment 2

[0087] 1) Preparation of aqueous dispersion containing PVDF powder and / or emulsion swollen by plasticizer and PVDF powder and / or emulsion without plasticizer swelling: water dispersant polyoxyethylene ether and plasticizer After tetrahydrofuran is stirred and dispersed evenly, PVDF powder and / or emulsion (a1) is added to disperse and fully swell, then PVDF powder and / or emulsion (a2) is added to continue to disperse, and finally a binder is added to prepare plasticized Aqueous dispersion of PVDF powder and / or emulsion swollen with plasticizer and PVDF powder and / or emulsion without plasticizer swelling. Wherein, the mass percentage of water is 83wt%; the mass percentage of dispersant is 0.5wt%; the mass percentage of plasticizer is 1.5wt%; the mass percentage of PVDF powder and / or emulsion (a1) The component content is 5wt%; the mass percent of PVDF powder and / or emulsion (a2) is 5wt%; the mass percent of binder is 5wt%.

[0088] 2) Preparation of composite diaphragm: The abo...

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Abstract

The invention discloses a composite diaphragm comprising PVDF coating with a lamellar structure and a preparation method thereof, and application of a composite diaphragm comprising PVDF coating witha lamellar structure. The composite diaphragm comprises a porous basal membrane containing holes and coating at the surfaces of one side or two sides of the porous basal membrane; the coating comprises a PVDF with a lamellar structure. The addition of the PVDF with the lamellar structure in the coating effectively increases the contact area of the PVDF and the porous base membrane, the effect of well bonding with the membrane base layer is achieved while the content of the binder in the coating is reduced; the PVDF coating with the lamellar structure is employed to obviously reduce the contentof the binder in the coating, the air permeability of the composite diaphragm is less influenced by the coating, the prepared composite diaphragm has better air permeability, and a battery adopting the composite diaphragm has good circulation and rate capability; the PVDF with the lamellar structure can form a loose stacking structure, the porosity of the coating is improved, and the transmissionof lithium ions is facilitated. The preparation method is simple and easy to implement and is suitable for large-scale industrial production.

Description

technical field [0001] The invention belongs to the technical field of battery diaphragms, and in particular relates to a composite diaphragm comprising a PVDF coating of a sheet structure, a preparation method and an application thereof. Background technique [0002] Lithium-ion batteries have the advantages of high voltage, high energy density, good cycle performance, small self-discharge, no memory effect, and wide operating temperature range. In order to reduce the weight of lithium-ion batteries or increase the energy density of lithium-ion batteries, soft-pack batteries packaged in aluminum-plastic films are more and more widely used. The aluminum-plastic film flexible packaging is different from the commonly used steel or aluminum shell packaging. Since the flexible packaging has no rigid shell, the battery cell and the aluminum-plastic film are easily displaced, and at the same time, the pole piece and the diaphragm in the battery cell are also easily misaligned, res...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/14H01M2/16H01M10/0525
CPCH01M10/0525H01M50/403H01M50/411H01M50/449Y02E60/10
Inventor 周建军胡志宇方芳李林
Owner BEIJING NORMAL UNIVERSITY
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