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Modified separator, preparation method thereof and lithium ion battery

A diaphragm and modification technology, applied in the field of modified diaphragm and its preparation method and lithium ion battery, can solve the problems of producing lithium dendrite, low migration number, battery concentration polarization, etc., to reduce the AC impedance value, improve the Safety performance, the effect of extending the rate performance

Inactive Publication Date: 2019-04-02
蜂巢能源(武汉)有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] The purpose of the present invention is to provide a modified diaphragm and its preparation method and lithium ion battery, so as to improve the conductivity of the diaphragm to lithium ions, thereby solving the problem that the lithium ion battery in the prior art has a low lithium ion migration number and the battery is easy to produce Concentration polarization leads to the technical problem of lithium dendrites on the surface of the negative electrode

Method used

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  • Modified separator, preparation method thereof and lithium ion battery
  • Modified separator, preparation method thereof and lithium ion battery

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preparation example Construction

[0039] The embodiment of the present invention also provides a method for preparing the above-mentioned modified diaphragm, which includes the following steps: coating a polymer whose side chain is substituted with lithium sulfonate on at least one surface of the diaphragm substrate. Preferably, before the coating step, the preparation method of the above-mentioned modified diaphragm further includes the following steps: dissolving in an organic solvent to prepare a solution with a polymer percentage of 3wt.% to 10wt.%. The vinylidene fluoride-hexafluoropropylene copolymer is dissolved in an organic solvent to prepare a polyvinylidene fluoride-hexafluoropropylene copolymer solution with a percentage content of 0wt.% to 50wt.%, and the two solutions are mixed uniformly to obtain a mixed solution. The mixed solution is coated on at least one surface of the separator substrate. Preferably, the polyvinylidene fluoride-hexafluoropropylene copolymer has a number average molecular we...

Embodiment 1

[0049] This embodiment provides a modified diaphragm, which includes a polyethylene diaphragm substrate and a polyphenylene ether coating whose side chains are substituted by sulfonate lithium on both surfaces of the polyethylene diaphragm; wherein, the porosity of the polyethylene diaphragm is 40%, and the thickness is 9 μm; the polyphenylene ether substitution degree of the side chain in the polyphenylene ether coating is 66%, and its mass percentage in the coating is 70%. The thickness of the coating on the surface was 3 μm. Three sets of parallel tests of the above-mentioned modified separator showed that the average lithium ion migration number was 0.44, and the average conductivity was 0.12 mS / cm.

[0050] The preparation method of the modified membrane of the present embodiment comprises the following steps:

[0051] (1) Weigh polyphenylene ether and dissolve it in N-methylpyrrolidone, raise the temperature to 100°C immediately after introducing nitrogen gas, and add l...

Embodiment 2

[0059]This embodiment provides a modified diaphragm, which includes a polypropylene diaphragm substrate and a polyarylether ketone coating whose side chains are substituted by lithium sulfonate on both surfaces of the polypropylene diaphragm; wherein, the pores of the polypropylene diaphragm The ratio is 40%, and the thickness is 9 μm; the substitution degree of polyaryletherketone in the polyaryletherketone coating is 72%, and its mass percentage in the coating is 70%. The thickness of the coating on each surface is 3 μm. Three sets of parallel tests of the above-mentioned modified separator showed that the average lithium ion migration number was 0.55, and the average conductivity was 0.19 mS / cm.

[0060] The preparation method of the modified membrane of the present embodiment comprises the following steps:

[0061] (1) Weigh polyaryletherketone and dissolve it in N-methylpyrrolidone, raise the temperature to 140°C immediately after feeding nitrogen, and drop liquid bromin...

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Abstract

The invention provides a modified separator, a preparation method thereof and a lithium ion battery. The modified separator comprises a separator substrate and a polymer coating layer, wherein the polymer coating layer is arranged on a surface of the separator substrate and comprises a polymer, and a side link of the polymer is substituted by lithium sulfonate. The surface of the separator substrate in the modified separator comprises the polymer coating layer, the polymer coating layer comprises the lithium sulfonate group, the modified separator has a function of conducting lithium ions, themobility number of the lithium ions in an electrolyte can be increased when the modified separator is used in the lithium ion battery, the AC resistance value of the modified separator is reduced, the concentration polarization phenomenon is reduced, so that the growth of lithium dendrites of a battery negative electrode is reduced or prevented, the short-circuit risk of the battery is reduced, the safety and the rate performance of the lithium ion battery are effectively improved, and the cycle service lifetime of the lithium ion battery is prolonged. According to the preparation method of the modified separator, the polymer coating layer of which the side link is substituted by the lithium sulfonate is coated on the surface of the separator substrate, so that the modified separator hasrelatively low substitution degree in a polymer and also has relatively high lithium ion mobility, and the effect of reducing the lithium dendrites is achieved.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a modified diaphragm, a preparation method thereof and a lithium ion battery. Background technique [0002] As one of the key components of lithium-ion batteries, the separator mainly plays the role of preventing short circuit caused by the contact of positive and negative electrodes. In addition, the pore structure inside the separator constitutes the transmission channel of lithium ions, enabling the electrochemical reaction of the battery to occur. The structure and mechanical properties of the separator will affect the charge and discharge capacity, rate performance, cycle performance and safety performance of the battery. The current commercial lithium-ion battery separator is mainly based on polypropylene (PP) or polyethylene (PE), and the surface of the substrate is coated with ceramic and adhesive coating, which can effectively improve the wettability of the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16H01M2/14H01M10/0525H01M50/403H01M50/414H01M50/489
CPCH01M10/0525H01M50/403H01M50/449H01M50/411Y02E60/10
Inventor 陈继钦
Owner 蜂巢能源(武汉)有限公司
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