Insulating film for secondary battery

Abstract

The utility model provides an insulating film for a secondary battery, which comprises an outer-layer insulating film and an inner-layer insulating film which are sequentially laminated and connected from outside to inside, the outer-layer insulating film and the inner-layer insulating film are connected through a first adhesive, the tensile strength of the outer-layer insulating film is 30-300MPa, and the elongation rate of the outer-layer insulating film is 5-200%; according to the utility model, the first layer of insulating film is high in strength and can play a certain role in resisting needling, and the second layer of insulating film is high in ductility and is mainly used for preventing the layer from being punctured by a puncture, so that the insulating film is always coated on a punctured sharp object; if the third layer of insulating film is made of the same material as the first layer of insulating film, the overall tensile strength of the third layer of insulating film is improved; if the third layer of insulating film is made of a material of which the elongation rate is smaller than that of the middle insulating film, the third layer of insulating film has double insurance of preventing puncture; according to the utility model, the needling ignition time of the battery is prolonged and even the battery is not ignited through a plurality of layers of insulating films with different characteristics.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion batteries, and in particular to an insulating film for secondary batteries. Background Technology

[0002] With the development of new energy sources, the energy density requirements of existing batteries are further increasing. New energy power batteries are usually secondary batteries, which are batteries that can be used again after being discharged by recharging to activate the active materials.

[0003] As a crucial component of electric vehicles, the safety and reliability of secondary batteries are of paramount importance. Before leaving the factory, batteries undergo various rigorous tests and obtain relevant certifications before being shipped. Among these tests, the nail penetration test simulates whether the battery can provide sufficient time for passengers to safely escape after being punctured by a hard object. Currently, the nail penetration test is one of the most challenging tests for batteries to pass.

[0004] Currently, batteries generally use PP as the insulating film for secondary batteries to prevent short circuits caused by bare cells contacting the aluminum casing for various reasons. In the nail penetration test, the needle penetrates the aluminum casing and then inserts into the insulating film for secondary batteries. Due to its good ductility, the insulating film has a certain probability of delaying the rapid heating and ignition of the positive and negative electrode plates due to short circuits during the puncture process. However, when the nail penetration test reaches a certain level, the existing insulating film will still fail during the puncture process. Therefore, there is an urgent need for relevant methods to delay the ignition time of the battery by nail penetration as much as possible or even prevent it from igniting.

[0005] Therefore, we propose a method for using an insulating film in secondary batteries to delay the ignition time of battery needle penetration. Utility Model Content

[0006] The purpose of this utility model is to overcome the shortcomings of the existing technology. To achieve the above objective, this utility model adopts the following technical solution:

[0007] An insulating film for secondary batteries includes an outer insulating film and an inner insulating film stacked sequentially from the outside to the inside. The outer insulating film and the inner insulating film are connected by a first adhesive. The tensile strength of the outer insulating film is 30-300 MPa, and the elongation of the outer insulating film is 5-200%. This invention uses two insulating films with different properties to delay the time of battery ignition by needle penetration or even prevent the battery from igniting.

[0008] More preferably, the inner insulating film is a second insulating film, the tensile strength of the second insulating film is 5-100MPa, and the elongation of the second insulating film is 40-500%.

[0009] More preferably, the inner insulating film consists of a second insulating film and a third insulating film, which are connected by a second adhesive, and the second insulating film is located between the outer insulating film and the third insulating film.

[0010] More preferably, the tensile strength of the third insulating film is 30-300 MPa, and the elongation of the third insulating film is 5-200%.

[0011] More preferably, the tensile strength of the third insulating film is 5-100 MPa, and the elongation of the third insulating film is 40-500%.

[0012] More preferably, the thickness of the outer insulating film, the second insulating film and the third insulating film are all 0.01-1mm, preferably 0.03-0.3mm.

[0013] More preferably, the thickness of both the first adhesive and the second adhesive is 0.001-0.01 mm, more preferably 0.001-0.005 mm.

[0014] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0015] To delay the ignition time of a secondary battery due to puncture, this invention designs the secondary battery with at least two layers of insulating film. The first layer of insulating film has high strength, providing some resistance to needle puncture. The second layer of insulating film has high elongation, primarily to prevent puncture and ensure it remains completely covered by the sharp object. For added safety, a third layer of insulating film can be added. If the third layer uses the same material as the first layer, it enhances the overall tensile strength. If the third layer uses a material with lower elongation than the middle insulating film, it provides double protection against puncture. This invention uses multiple layers of insulating films with different properties to delay the ignition time of the battery due to needle puncture, or even prevent the battery from igniting altogether. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a double-layer insulating film;

[0017] Figure 2 This is a schematic diagram of the structure of the double-layer insulating film and the battery cell;

[0018] Figure 3 This is a schematic diagram of the three-layer insulating film structure;

[0019] Figure 4 This is a schematic diagram of the structure of the three-layer insulating film and the battery cell.

[0020] In the diagram: 1. Outer insulating film; 2. First adhesive; 3. Second insulating film; 4. Second adhesive; 5. Third insulating film; 6. Battery cell. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0022] Reference Figures 1-2 An insulating film for secondary batteries includes an outer insulating film 1 and an inner insulating film stacked sequentially from the outside to the inside. The outer insulating film 1 and the inner insulating film are connected by a first adhesive 2. The tensile strength of the outer insulating film 1 is 30-300 MPa, and the elongation of the outer insulating film 1 is 5-200%. The inner insulating film is a second insulating film 3, the tensile strength of the second insulating film 3 is 5-100 MPa, and the elongation of the second insulating film 3 is 40-500%. The thickness of the outer insulating film 1, the second insulating film 3, and the third insulating film 5 is 0.01-1 mm.

[0023] In this embodiment: the insulating film is designed to be at least double-layered. The outer side of the battery cell 6 is sequentially covered with a second insulating film 3 and an outer insulating film 1. The outermost insulating film 1 is PET with high tensile strength and low elongation, with a thickness of 0.074 mm; the second insulating film 3 is PP with low tensile strength and high elongation, with a thickness of 0.074 mm; the insulating films are all bonded together with a 0.002 mm thick adhesive.

[0024] The first layer of the insulating film of this invention has high strength and can resist needle puncture to a certain extent. The second layer of the insulating film has high elongation, which mainly prevents the puncture from breaking through this layer and keeps it always covering the sharp object that is puncturing. This invention uses two insulating films with different properties to delay the time of battery ignition by needle puncture or even prevent the battery from igniting.

[0025] The inner insulating film consists of a second insulating film 3 and a third insulating film 5, which are connected by a second adhesive 4. The second insulating film 3 is located between the outer insulating film 1 and the third insulating film 5. The tensile strength of the third insulating film 5 is 30-300 MPa, and the elongation of the third insulating film 5 is 5-200%.

[0026] In this embodiment: the insulating film is designed as three layers. The outer side of the battery cell 6 is sequentially covered with a third insulating film 5, a second insulating film 3, and an outer insulating film 1. The outermost insulating film 1 is made of PET with high tensile strength and low elongation, and has a thickness of 0.05 mm. The second insulating film is made of PP with low tensile strength and high elongation, and has a thickness of 0.05 mm. On this basis, a third insulating film with a thickness of 0.05 mm can be designed. The third film is made of PP, and the insulating films are intermittently bonded together with 0.002 mm thick adhesive.

[0027] The tensile strength of the third insulating film 5 is 5-100 MPa, and the elongation of the third insulating film 5 is 40-500%.

[0028] In this embodiment: the insulating film is designed as three layers. The outer side of the battery cell 6 is sequentially covered with a third insulating film 5, a second insulating film 3, and an outer insulating film 1. The outermost insulating film 1 is made of PET with high tensile strength and low elongation, and has a thickness of 0.04 mm. The second insulating film is made of PP with low tensile strength and high elongation, and has a thickness of 0.04 mm. On this basis, a third insulating film with a thickness of 0.04 mm can be designed. The third film can be made of PEEK. The insulating films are intermittently bonded together with a 0.002 mm thick adhesive.

[0029] The thickness of both the first adhesive 2 and the second adhesive 4 is 0.001-0.01 mm.

[0030] In the embodiment: both the first adhesive 2 and the second adhesive 4 are acrylic adhesives, and their models can be SDK178 / SDK57 / SDK121 / SDK76. The insulating films can be fully bonded together or intermittently bonded together by the acrylic adhesive.

[0031] To delay the ignition time of a secondary battery due to puncture, this invention designs the secondary battery with at least two layers of insulating film. The first layer of insulating film has high strength, providing some resistance to needle puncture. The second layer of insulating film has high elongation, primarily to prevent puncture and ensure it remains completely covered by the sharp object. For added safety, a third layer of insulating film can be added. If the third layer uses the same material as the first layer, it enhances the overall tensile strength. If the third layer uses a material with lower elongation than the middle insulating film, it provides double protection against puncture. This invention uses multiple layers of insulating films with different properties to delay the ignition time of the battery due to needle puncture, or even prevent the battery from igniting altogether.

Claims

1. An insulating film for secondary batteries, characterized in that, It includes an outer insulating film and an inner insulating film that are stacked sequentially from the outside to the inside. The outer insulating film and the inner insulating film are connected by a first adhesive. The tensile strength of the outer insulating film is 30-300 MPa, and the elongation of the outer insulating film is 5-200%.

2. The insulating film for secondary batteries according to claim 1, characterized in that, The inner insulating film is a second insulating film, the tensile strength of which is 5-100 MPa and the elongation of which is 40-500%.

3. The insulating film for secondary batteries according to claim 1, characterized in that, The inner insulating film consists of a second insulating film and a third insulating film, which are connected by a second adhesive. The second insulating film is located between the outer insulating film and the third insulating film.

4. The insulating film for a secondary battery according to claim 3, characterized in that, The tensile strength of the third insulating film is 30-300 MPa, and the elongation of the third insulating film is 5-200%.

5. The insulating film for a secondary battery according to claim 3, characterized in that, The tensile strength of the third insulating film is 5-100 MPa, and the elongation of the third insulating film is 40-500%.

6. The insulating film for a secondary battery according to claim 3, characterized in that, The thickness of the outer insulating film, the second insulating film, and the third insulating film is 0.01-1mm.

7. The insulating film for a secondary battery according to claim 3, characterized in that, The thickness of both the first adhesive and the second adhesive is 0.001-0.01 mm.

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