Reactive-polymer-carrying porous film and process for producing the same

A reactive polymer, porous membrane technology, applied in the field of porous membranes, can solve the problems of difficult to adjust product quality, insufficient adhesion of electrodes and separators, reduce thermal shrinkage, etc., to achieve improved ion permeability, excellent battery characteristics, the effect of maintaining battery characteristics

Inactive Publication Date: 2007-09-05
NITTO DENKO CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] When using the battery thus obtained, there is a problem that when the battery is placed in an abnormally high-temperature environment or overcharged, or when a short circuit occurs between electrodes inside or outside the battery, the battery is heated abnormally, making the inside of the battery The electrolyte sprays out from the battery, sometimes causing damage
However, this method has problems such as complicated process steps, difficulty in adjusting product quality, and insufficient adhesion between electrodes and separators (for example, see Patent Document 3)
However, according to this method, since the porous membrane is not stretched, it is difficult to obtain sufficient strength
As mentioned above, conventional methods cannot simultaneously improve heat resistance and reduce heat shrinkage to achieve the purpose of preventing separators from melting and breaking in high-temperature environments
[0007] In addition, in the case where the rechargeable lithium battery is used in a laptop personal computer (hereinafter referred to as a laptop PC), used in a high-temperature environment such as inside a car in summer, or left in a high-temperature environment for a long time in a charged state , it is difficult for rechargeable lithium batteries using conventional polyethylene porous membranes as separators to maintain their initial performance
For example, when a rechargeable lithium battery is used in a high-temperature environment of 50°C to 90°C, which is the possible temperature inside a laptop PC and a car, etc., or when it is left in a charged state for a long time, due to the electrode / separator element Due to internal tension or pressure, the porous membrane gradually deforms or oxidizes and deteriorates, so that the air permeability of the porous membrane decreases (that is, the Gurley value increases), and the battery life decreases.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0106] (Production of Porous Membrane A)

[0107] The norbornene ring-opened polymer powder (Norsorex NB; product of Zeon Corporation, weight average molecular weight: more than 2,000,000) by 8 wt%, thermoplastic elastomer (TPE824; Sumitomo Chemical Co., Ltd. product) of 12 wt% and 80 wt% of 16 parts by weight of a polyethylene resin composition made of ultra-high molecular weight polyethylene with an average molecular weight of 3,500,000 and 84 parts by weight of liquid paraffin were mixed to form a slurry, and the mixture was melted and kneaded at a temperature of 160° C. for about 1 hour. Then, the obtained kneaded product was sandwiched between metal plates cooled to 0° C., rapidly cooled, and rolled into a sheet. Then, the sheet was hot-pressed at a temperature of 115° C. until the thickness of the sheet was 0.5 mm, and then biaxially stretched simultaneously at the same temperature in the longitudinal and transverse directions at a stretch ratio of 4.5, Heptane was used...

Embodiment 2

[0132] (Preparation of crosslinkable polymer B)

[0133] 40.0 g of methyl methacrylate, 20.0 g of 3-ethyl-3-oxetanyl methyl methacrylate, and 0.8 g of 2-hydroxyethyl methacrylate were placed in a 500 mL three-necked flask equipped with a reflux cooling tube. g, 19.2 g of butyl acrylate, 158 g of ethyl acetate, and 0.2 g of N,N'-azobisisobutyronitrile were stirred and mixed for 30 minutes under nitrogen gas, and then heated to 70° C. for 8 hours of radical polymerization. Thereafter, the resulting reaction mixture was cooled to 40°C. To this reaction mixture was added 0.2 g of N,N'-azobisisobutyronitrile, heated to 70°C again, and radical polymerization was performed for another 8 hours. Thereafter, the mixture was cooled to 40° C., 295 g of ethyl acetate was added, and then stirred until the mixture became uniform, thereby obtaining a polymer-forming ethyl acetate solution (concentration: 15 wt %).

[0134] Then, 100 g of the polymer solution was poured into 600 mL of methan...

Embodiment 3

[0139] (Production of porous membrane B)

[0140] 15 parts by weight of polyethylene resin formed from 20 wt% of EPDM (Espren 512F; product of Sumitomo Chemical Co., Ltd.; ethylidene norbornene content: 4 wt%) and 80 wt% of ultra-high molecular weight polyethylene with a weight average molecular weight of 1,500,000 The composition and 85 parts by weight of liquid paraffin were mixed into a slurry form, and the mixture was melted and kneaded at a temperature of 160° C. for about 1 hour using a small mixer. Then, the obtained kneaded product was sandwiched between metal plates cooled to 0° C., rapidly cooled, and rolled into a sheet. Then, the sheet was hot-pressed at a temperature of 115° C. until the thickness of the sheet was 0.4 mm, and then biaxially stretched at a stretch ratio of 4.0 in the longitudinal direction and the transverse direction at 123° C. at the same time. Heptane was desolvated. The porous membrane thus obtained was heated in air at 85° C. for 6 hours and...

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Abstract

It is intended to provide a reactive polymer-supported porous film that is capable of achieving sufficient adhesion between the electrode and the separator; reduced in internal resistance; and excellent in high rate characteristics, the porous film being useful as a battery separator which, after production of the battery, is not melted or broken under a high temperature and functions as a separator having a small heat shrinkage ratio as well as to provide a process for producing batteries using the reactive polymer-supported porous film. According to this invention, there is provided a reactive polymer-supported porous film for a battery separator, characterized in that the reactive polymer-supported porous film has: a substrate porous film of a porous film, the porous film has a temperature, at which a thickness of the porous film is reduced to 1/2 of a thickness when a prove is placed on the porous film in the case that the thickness of the porous film is measured by placing the probe having a diameter of 1 mm on the porous film under a load of 70 g and heating the porous film from a room temperature at a temperature-increase rate of 2 DEG C/minute, of 200 DEG C or more; and a reactive polymer supported on the substrate porous film, the reactive polymer is obtainable by reacting: a crosslinkable polymer obtainable by copolymerizing: a crosslinkable monomer having in a molecule at least one reactive group selected from a 3-oxetanyl group and an epoxy group; and a crosslinkable monomer having a reactive group capable of reacting with an isocyanate group; and a polyfunctional isocyanate to be partially crosslinked.

Description

technical field [0001] The present invention relates to a reactive polymer-loaded porous membrane useful in the manufacture of batteries and capable of contributing to the safe use of such batteries, and to a method of manufacturing batteries using the reactive polymer-loaded porous membrane. The invention also relates to batteries having separators obtainable from such reactive polymer loaded porous membranes. Background technique [0002] As a method of manufacturing a battery, there are known methods (for example, see Patent Documents 1 and 2) in which a positive electrode and a negative electrode are laminated with a separator to prevent a short circuit of the electrodes sandwiched therebetween, or a positive (negative) electrode is sequentially laminated. An electrode, a separator, a negative (positive) electrode, and a separator; an electrode / separator laminate is obtained by winding; the electrode / separator laminate is inserted into a battery; an electrolytic solution...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16B32B27/30H01M10/40H01M50/403H01M50/411H01M50/449H01M50/46H01M50/463
CPCY02E60/122Y02E60/10
Inventor 市川智昭山本一成植谷庆裕喜井敬介
Owner NITTO DENKO CORP
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