Battery diaphragm and preparation method thereof

A battery separator and electrolyte technology, applied in battery pack parts, circuits, electrical components, etc., can solve the problems of reducing battery energy density, poor tensile mechanical properties, uneven current density distribution, etc., to improve energy density, The effect of high mechanical strength and small pore size

Inactive Publication Date: 2019-03-26
GUANGDONG UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The disadvantage of the former type of diaphragm is that there is a stretching pore-forming / pore-enlarging process in the process of preparing polyolefin microporous diaphragms by dry method or wet method, and the diaphragm will undergo serious heat loss at higher temperatures (>130°C). Shrinkage (especially in the direction of stretching), which will lead to a short circuit of the positive and negative areas of the battery, which will cause thermal runaway and safety accidents
And the choice of polymer substrates for this type of diaphragm is very narrow. At present, the substrates of commercial diaphragms are mainly polyethylene (PE) and polypropylene (PP).
The disadvantage of the latter type of separator is that whether it is made of paper or electrospinning, the porous membrane is made of random arrangement, interweaving and adhesion of micro / nano fibers. The thermal shrinkage of the film has disadvantages, but it also brings many new problems: On the one hand, the uneven distribution of pores and pore sizes formed by the random accumulation of micro / nano fibers leads to uneven distribution of current density during charge and discharge, which in turn leads to the battery's high current density. Dendrites are generated during charge and discharge, which affects the cycle performance of the battery; on the other hand, the random accumulation of micro / nano fibers into curved channels will affect the direct shuttle of lithium ions between the separators, increasing the internal resistance of the battery; and This type of separator is made of random micro-nano fibers only through simple arrangement and bonding, and its tensile mechanical properties are poor, so it is basically not suitable for use in spun lithium-ion batteries. The winding tension required by the ion battery is also very small, which not only increases the internal resistance of the battery but also reduces the energy density of the battery

Method used

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  • Battery diaphragm and preparation method thereof

Examples

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Effect test

Embodiment 1

[0066] This embodiment provides the first battery separator, and the specific preparation method is as follows:

[0067] 1. Dry polyvinylidene fluoride (PVDF) at 80°C for 10 hours in a vacuum environment, then dissolve PVDF powder in N-methylpyrrolidone (NMP) solution to obtain transparent, uniform and stable PVDF / NMP The battery separator spinning solution, wherein the solid content of the battery separator spinning solution is 21 wt%.

[0068] 2. The prepared PVDF / NMP battery separator spinning solution is made into PVDF battery separator fiber by electrospinning. The injection needle is 12# (the inner diameter of the needle is 1.2mm), the spinning voltage is 13.5KV, the advancing speed of the metering pump is 0.065mm / min, the distance between the syringe needle and the receiving plate is 20cm, the spinning time is 0.5h, and the spinning temperature is 25°C. The air humidity is 45%, the carbon paper is bent and spread on the receiving roller, and the yarn is collected at a...

Embodiment 2

[0071] This embodiment provides the second battery separator, and the specific preparation method is as follows:

[0072] 1. Polyetherimide (PEI) was dried at 80°C for 6 hours in a vacuum environment, and then the PEI particles were dissolved in N-methylpyrrolidone (NMP) solution at 90°C to obtain transparent, uniform and stable PEI battery separator spinning solution, wherein, the solid content of PEI battery separator spinning solution is 25wt%.

[0073] 2. The prepared transparent PEI battery separator spinning solution is prepared into PEI battery separator fiber filaments by an electrospinning method. The injection needle adopts 12# (the inner diameter of the needle is 1.2mm), the spinning voltage is 14KV, the advancing speed of the metering pump is 0.05mm / min, the distance between the syringe needle and the receiving plate is 20cm, the spinning time is 0.5h, and the spinning temperature is 25°C. The air humidity is 45%, the carbon paper is bent and spread on the receiv...

Embodiment 3

[0076] This embodiment provides the third battery separator, the specific preparation method is as follows:

[0077] 1. Dry polypropylene (PP) at 80°C for 6 hours in a vacuum environment, and then dissolve PP particles in N-methylpyrrolidone (NMP) solution at 90°C to obtain a transparent, uniform and stable PP battery Separator spinning solution, wherein the solid content of the PEI battery separator spinning solution is 25wt%.

[0078] 2. The prepared transparent PP battery separator spinning solution is made into PP battery separator fiber by electrospinning. The injection needle adopts 12# (the inner diameter of the needle is 1.2mm), the spinning voltage is 14KV, the advancing speed of the metering pump is 0.055mm / min, the distance between the syringe needle and the receiving plate is 20cm, the spinning time is 0.5h, and the spinning temperature is 25°C. The air humidity is 45%, the carbon paper is bent and spread on the receiving roller, and the yarn is collected at a lo...

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Abstract

The invention belongs to the technical field of lithium ion batteries and particularly relates to a battery diaphragm and a preparation method thereof. The preparation method of the battery diaphragmcomprises the steps of putting battery diaphragm fiber filaments into a textile machine, and weaving by virtue of the textile machine, so as to obtain the battery diaphragm, wherein the battery diaphragm fiber filaments are electronically insulated battery diaphragm fiber filaments which do not react with electrolyte, and the diameters of the battery diaphragm fiber filaments are 5-40 microns. Theinvention aims at providing the battery diaphragm with uniform small pore diameter and high porosity, so that dendritic crystals are produced in the charging and discharging processes of the battery,and the cycle performance of the battery is improved.

Description

technical field [0001] The invention belongs to the technical field of batteries, and in particular relates to a battery diaphragm and a preparation method thereof. Background technique [0002] At present, there are two main types of methods for preparing lithium-ion battery separators: one is polyolefin microporous membranes prepared by melting heat stretching (dry method) or thermally induced phase separation (wet method); the other is using papermaking Or a non-woven separator prepared by an electrospinning process. The disadvantage of the former type of diaphragm is that there is a stretching pore-forming / pore-enlarging process in the process of preparing polyolefin microporous diaphragms by dry method or wet method, and the diaphragm will undergo serious heat loss at higher temperatures (>130°C). Shrinkage (especially in the direction of stretching), which will lead to a short circuit with a large area of ​​the positive and negative sides of the battery, causing th...

Claims

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Application Information

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IPC IPC(8): H01M2/14H01M2/16H01M50/403H01M50/411H01M50/44H01M50/491
CPCH01M50/403H01M50/411H01M50/44Y02E60/10
Inventor 刘全兵李俊豪张圣洁党岱方岩雄
Owner GUANGDONG UNIV OF TECH
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