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Battery diaphragm and preparation method thereof, battery and terminal

A battery diaphragm and diaphragm technology, applied in secondary batteries, battery pack components, circuits, etc., can solve problems such as easy puncture of the diaphragm, out-of-control failure of the battery cell, and poor ductility, so as to reduce the risk of puncture, Improve safety and benefit cost control

Active Publication Date: 2020-07-14
HUAWEI TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Due to the poor ductility of the currently commonly used polyolefin diaphragm, the diaphragm is easily punctured when the cell is mechanically abused, and a short circuit point is formed between the positive and negative electrodes at the position where the diaphragm is damaged, which in turn causes the thermal runaway failure of the cell, resulting in Security risks

Method used

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  • Battery diaphragm and preparation method thereof, battery and terminal
  • Battery diaphragm and preparation method thereof, battery and terminal
  • Battery diaphragm and preparation method thereof, battery and terminal

Examples

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preparation example Construction

[0065] Such as image 3 As shown, the embodiment of the present application also provides the preparation method of the above-mentioned battery separator, including:

[0066] S101. Mixing polyolefin resin raw materials and a solvent to obtain a mixed solution, where the polyolefin resin raw materials include polyethylene resin raw materials; the degree of crystallinity measured after mixing the polyethylene resin raw materials is <55%;

[0067] S102, extruding the mixed solution, cooling and casting it into a sheet;

[0068] S103, stretching, extracting, and drying the sheet once to form a porous film;

[0069] S104. The porous film is subjected to secondary stretching and heat setting to obtain a polyolefin porous diaphragm substrate; in the process of preparing the polyolefin resin raw material into a polyolefin porous diaphragm substrate, control the polyethylene resin raw material to the finished diaphragm substrate The increase of the crystallinity of the material is le...

Embodiment 1

[0087] 1. Preparation of battery separator

[0088] The resin raw material adopts a single polyethylene resin with a mass average molecular weight Mw of 600,000 and a crystallinity of 54%. The resin and paraffin oil are melted and mixed in a twin-screw extruder at a temperature of 200°C at a mass ratio of 25:75. 0.3% of antioxidant is added, and the homogeneously kneaded melt is extruded and cast through a slit die. The extrusion speed of the die head melt is 5m / min, the cooling speed of the cast sheet is 80°C / min, and the gel sheet is asynchronously (non-synchronously) biaxially stretched once at 116°C, and the stretching ratio in the MD and TD directions Both are 4.5 times, and the stretching speed is 30% / s. The stretched film was then extracted with dichloromethane to remove paraffin oil components. The film after extraction is subjected to secondary stretching at 125° C., and the secondary stretching is only stretched in the TD direction, and the stretching ratio is 1.1 ...

Embodiment 2

[0095] The resin raw material adopts a single polyethylene resin with a mass average molecular weight Mw of 600,000 and a crystallinity of 54%. The resin and paraffin oil are melted and mixed in a twin-screw extruder at a temperature of 200°C at a mass ratio of 25:75. 0.3% of antioxidant is added, and the homogeneously kneaded melt is extruded and cast through a slit die. The extrusion speed of the die head melt is 5.5m / min, the cooling speed of the cast sheet is 80°C / min, and the gel sheet is asynchronously stretched once at 118°C, and the stretching ratios in both MD and TD directions are 4 times, the stretching speed is 33% / s. The stretched film was then extracted with dichloromethane to remove paraffin oil components. The film after extraction is subjected to secondary stretching at 126° C., and the secondary stretching is only stretched in the TD direction, and the stretching ratio is 1.1 times. Finally, it is made into a polyolefin porous diaphragm base material after ...

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Abstract

The embodiment of the invention provides a battery diaphragm. The diaphragm comprises a polyolefin porous diaphragm base material, wherein the polyolefin porous diaphragm base material comprises polyethylene resin, the elongation of the polyolefin porous diaphragm base material in the MD direction is greater than 120%, the polyolefin porous diaphragm base material has an elongation rate of more than 120% in the TD direction, the polyolefin porous diaphragm base material has a primary heating crystallinity of less than 65% and a secondary heating crystallinity of less than 55%, which are measured by a differential scanning calorimeter, and the difference between the primary heating crystallinity and the secondary heating crystallinity is less than 12%. The battery diaphragm has the characteristics of high elongation and low hole closing temperature, and by implementing the embodiment of the invention, the diaphragm rupture risk can be reduced when a battery cell is mechanically abused,and meanwhile, diaphragm pores are closed in advance when the battery cell is thermally abused, so the safety of the battery cell is improved. The embodiment of the invention further provides a preparation method of the battery diaphragm as well as a battery and a terminal adopting the battery diaphragm.

Description

technical field [0001] The present application relates to the technical field of lithium-ion batteries, in particular to a battery separator, a preparation method thereof, a battery and a terminal. Background technique [0002] Lithium-ion batteries are currently commercialized and widely used secondary power sources. In lithium-ion batteries, the separator is a porous, electrochemically inert medium between the positive and negative electrodes that does not participate in electrochemical reactions but is critical to the safety performance of the cell. Due to the poor ductility of the currently commonly used polyolefin diaphragm, the diaphragm is easily punctured when the cell is mechanically abused, and a short circuit point is formed between the positive and negative electrodes at the position where the diaphragm is damaged, which in turn causes the thermal runaway failure of the cell, resulting in Security risks. Contents of the invention [0003] The embodiment of th...

Claims

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Application Information

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IPC IPC(8): H01M2/14H01M2/16H01M10/0525
CPCH01M10/0525H01M50/406H01M50/417H01M50/457H01M50/494H01M50/489H01M10/4235Y02E60/10H01M50/449H01M50/446H01M50/451H01M50/414H01M50/491H01M50/403H01M50/46H01M50/431H01M10/052H01M50/247H01M2220/30
Inventor 张新枝邓耀明高云雷阳东方徐凡谢封超
Owner HUAWEI TECH CO LTD
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