Composite packaging film

Abstract

The utility model provides a composite packaging film, the composite packaging film is used for a battery cell, along a first direction, the composite packaging film is sequentially provided with a heat sealing layer, an adsorption layer and a blocking layer, the heat sealing layer is attached to an unpackaged battery cell and is provided with a to-be-punched pit area, the to-be-punched pit area is opposite to the surface of the unpackaged battery cell, and the heat sealing layer can be melted when the upper limit of the set use temperature of the battery cell is exceeded; the adsorption layer can adsorb liquid and is located in at least one of the to-be-scoured pit areas; and the blocking layer is used for blocking the unpackaged battery cell. The composite packaging film disclosed by the utility model reduces the risk of side reaction between electrolyte and the positive and negative electrodes when the battery cell is in thermal runaway, simultaneously inhibits the expansion problem when the battery cell is in thermal runaway, and greatly improves the safety of the battery.

Description

Technical Field

[0001] The utility model relates to the technical field of battery core packaging, in particular to a composite packaging film. Background Art

[0002] Lithium-ion batteries are prone to thermal runaway under the influence of high temperature environment. The large amount of heat and harmful gases emitted by thermal runaway can cause the battery to catch fire and explode. With the increasing demand for lithium-ion batteries, the thermal runaway phenomenon of the battery cell has greatly hindered its development process. When the battery cell thermal runaway occurs, the negative electrode SEI film decomposes first, the diaphragm melts and decomposes, the negative electrode reacts with the electrolyte, and then the positive electrode and the electrolyte decompose, which triggers a large-scale internal short circuit, causing the electrolyte to burn, and then spread to other batteries, causing serious thermal runaway, causing the entire battery to spontaneously combust. Therefore, suppressing the thermal runaway of the battery cell is particularly important for the development of lithium-ion batteries. In recent years, according to the location where the safety mechanism reaction occurs, the way to suppress thermal runaway is divided into two dimensions of improvement: outside the battery cell and inside the battery cell. The improvement inside the battery cell can mainly be achieved by increasing the diaphragm rupture temperature, using electrolyte additives, modifying the surface of the positive and negative electrodes to change the electrochemical reaction morphology, etc. The improvements on the outside of the battery cells mainly use various simulation platforms to provide early warning of thermal runaway and improve monitoring of battery cell safety; as well as externally place foam between battery cells to suppress expansion problems caused by thermal runaway.

[0003] Many improvements have been made in the prior art to suppress thermal runaway in battery cells. However, improvements on the outside of the battery cell, such as thermal runaway warnings through simulation platforms, have a certain timeliness, and cannot accurately judge the warning before thermal runaway occurs like physical reactions, and the feedback time will also have a certain delay. Therefore, the prior art mainly suppresses thermal runaway through improvements inside the battery cell, such as changing the form of its electrochemical reaction and optimizing the mechanism of the electrochemical reaction process, which causes a certain degree of reduction in the battery's electrical performance. At the same time, the modification of the positive and negative electrode materials will also increase the raw material cost of the battery cell and the complexity of the manufacturing process. Utility Model Content

[0004] The utility model provides a composite packaging film to solve the above problems.

[0005] The utility model provides a composite packaging film for a battery core, which is provided with a heat sealing layer, an adsorption layer and a barrier layer in sequence along a first direction, wherein:

[0006] The heat sealing layer is attached to the unpackaged battery cell and has a pit area to be punched, the pit area to be punched is opposite to the surface of the unpackaged battery cell, and the heat sealing layer can melt when the upper limit of the set use temperature of the battery cell is exceeded;

[0007] An adsorption layer, capable of absorbing liquid, is located in at least one of the pit areas to be flushed;

[0008] The barrier layer is used to form a barrier for unpackaged battery cells.

[0009] Compared with other methods for improving the internal structure of the battery cell to suppress thermal runaway of the battery cell, the above technical solution does not need to change the electrode material and electrolyte inside the battery cell, has a simple structure, is not easily corroded by the electrolyte, and does not affect the electrical performance of the battery cell. In the high temperature environment when the battery cell is in thermal runaway, the adsorption layer can absorb the electrolyte promptly and quickly, reducing the risk of side reactions between the electrolyte and the positive and negative electrodes, while suppressing the expansion problem when the battery cell is in thermal runaway, greatly improving the safety of the battery.

[0010] Optionally, the adsorption layer is located in one of the pit-punching areas, and the heat-sealing layer covered by the adsorption layer is 20-30 μm thinner than the heat-sealing layer not covered by the adsorption layer.

[0011] Optionally, the thickness of the heat-sealing layer covered by the adsorption layer is 30-50 μm, and the thickness of the heat-sealing layer not covered by the adsorption layer is 50-80 μm.

[0012] Optionally, the heat sealing layer is a dry process heat sealing layer.

[0013] Optionally, the dry process heat sealing layer is coated on the adsorption layer and the barrier layer, and an adhesive layer exists between the adsorption layer or the dry process heat sealing layer and the barrier layer, and the thickness of the adhesive layer is 5 to 20 μm.

[0014] Optionally, the adhesive layer material is one of epoxy resin, polyurethane, and thermoplastic polyolefin.

[0015] Optionally, the heat sealing layer material is polypropylene.

[0016] Optionally, the adsorption layer material is wood pulp sponge.

[0017] Optionally, the adsorption layer has a thickness of 40 to 60 μm.

[0018] Optionally, the barrier layer includes a barrier layer and an outer barrier layer, the barrier layer is made of aluminum alloy, and the outer barrier layer is made of nylon. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The specific implementation methods of the utility model will be described in detail below in conjunction with the accompanying drawings.

[0020] Figure 1 It is a cross-sectional schematic diagram of a composite packaging film according to an embodiment of the utility model;

[0021] Figure 2 It is a cross-sectional schematic diagram of a composite packaging film according to another embodiment of the utility model;

[0022] Figure 3 This is a schematic diagram of the composite packaging film of the embodiment of the utility model used for packaging unpackaged battery cells;

[0023] Figure 4-A The working state of the composite packaging film of the utility model embodiment to suppress thermal runaway of the battery cell is shown in FIG. Figure 1 ;

[0024] Figure 4-B The working state of the composite packaging film of the utility model embodiment to suppress thermal runaway of the battery cell is shown in FIG. Figure 2 ;

[0025] Figure 4-C The working state of the composite packaging film of the utility model embodiment to suppress thermal runaway of the battery cell is shown in FIG. Figure 3 .

[0026] (Explanation of symbols)

[0027] 0 Composite packaging film

[0028] 01 Waiting area

[0029] 1 Heat seal layer

[0030] 2 Barrier layer

[0031] 3. External resistance layer

[0032] 4 Adsorption layer

[0033] 5 Adhesive layer

[0034] 6 Unpackaged cells

[0035] X first direction DETAILED DESCRIPTION

[0036] The following specific embodiments illustrate the implementation of the utility model. Those skilled in the art can easily understand other advantages and functions of the utility model from the contents disclosed in this specification. Although the description of the utility model will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this utility model are limited to this implementation. On the contrary, the purpose of introducing the utility model in conjunction with the implementation is to cover other options or modifications that may be extended based on the claims of the utility model. In order to provide an in-depth understanding of the utility model, the following description will include many specific details. The utility model can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the utility model, some specific details will be omitted in the description.

[0037] In addition, the terms “upper”, “lower”, “bottom” and directions used in the following description should not be construed as limiting the present invention.

[0038] The utility model provides a composite packaging film for a battery core. Figure 1The composite packaging film 0 of the present invention includes a cross-sectional schematic diagram. Figure 1 , Figure 2 , Figure 4-A , Figure 4-B and Figure 4-C In the X direction, specifically in the direction from the inside to the outside relative to the battery core, there are sequentially provided: a heat sealing layer 1, an adsorption layer 4 and a barrier layer, wherein:

[0039] The heat-sealing layer 1 is attached to the unpackaged battery cell 6 and has a pit-to-be-punched area, which is opposite to the surface of the unpackaged battery cell 6. The heat-sealing layer 1 can melt when the upper limit of the set use temperature of the battery cell is exceeded;

[0040] An adsorption layer 4, capable of absorbing liquid, is located in at least one of the pit areas 01 to be flushed;

[0041] The barrier layer is used to form a barrier for the unpackaged battery cells 6 .

[0042] The unpackaged battery cell in this embodiment is a bare battery cell. When the battery cell temperature exceeds the set use temperature of the battery cell, the heat sealing layer 1 begins to melt and decompose, exposing the adsorption layer 4 and directly contacting the unpackaged battery cell 6. The adsorption layer 4 can absorb the electrolyte in a timely and rapid manner, reducing the risk of side reactions between the electrolyte and the positive and negative electrodes, while suppressing the expansion problem of the battery cell during thermal runaway, greatly improving the safety of the battery.

[0043] In this embodiment, if Figure 3 As shown, the adsorption layer 4 (as Figure 1 and Figure 2 ) is located in one of the pit areas 01 to be flushed. For another example, when there are two pit areas 01 to be flushed, the adsorption layer 4 (as shown Figure 1 and Figure 2 As shown) can be respectively arranged in two pit areas 01 to be flushed, the adsorption layer 4 (as shown Figure 1 and Figure 2As shown) it can also be arranged to be located only in one of the two pit areas 01 to be punched. The heat sealing layer 1 covered by the adsorption layer 4 is 20 to 30 μm thinner than the heat sealing layer 1 not covered by the adsorption layer 4. Further, the thickness of the heat sealing layer 1 covered by the adsorption layer 4 is 30 to 50 μm, preferably, the thickness is 30 to 40 μm; the thickness of the heat sealing layer 1 not covered by the adsorption layer 4 is 50 to 80 μm, preferably, the thickness is 60 to 70 μm. The numerical range that the heat sealing layer 1 covered by the adsorption layer 4 is thinner than the heat sealing layer 1 not covered by the adsorption layer 4 is conducive to ensuring the performance of the composite packaging film 0. At the same time, ensuring that the thickness of the composite packaging film 0 is thinner is conducive to the occurrence of electrochemical reactions. The thickness of the heat sealing layer 1 not covered by the adsorption layer 4 is thicker, which can help prevent the leakage of the electrolyte. In addition, the heat sealing layer 1 is not completely covered by the adsorption layer 4, which avoids affecting the welding process in the packaging process, and is conducive to ensuring the battery cell packaging process.

[0044] Furthermore, the heat-sealing layer 1 is a dry process heat-sealing layer, and the dry process is conducive to punching and forming. Figure 2 As shown, the heat sealing layer 1 is coated on the adsorption layer 4 and the barrier layer, an adhesive layer 5 exists between the adsorption layer 4 and the barrier layer, and an adhesive layer 5 exists between the dry process heat sealing layer and the barrier layer. The thickness of the adhesive layer 5 is 5 to 20 μm, preferably 5 to 10 μm. The above adhesive thickness range is conducive to the processing of the composite packaging film 0 and ensures the stability of its structure.

[0045] In the above embodiment, the material of the adhesive layer 5 is one of epoxy resin, polyurethane, and thermoplastic polyolefin. The above material will not chemically react with the electrolyte, and is resistant to electrolyte, heat, aging, and has good adhesion.

[0046] In the present utility model, preferably, the heat sealing layer material is polypropylene. The normal working temperature of the battery core does not exceed 70°C at most. When it exceeds 70°C, the polypropylene material of the heat sealing layer 1 begins to dissolve, exposing the adsorption layer 4, and adsorbing the electrolyte to prevent the battery core from having a more severe thermal runaway phenomenon. Among them, further, the material of the adsorption layer 4 is wood pulp sponge. Wood pulp sponge has strong adsorption capacity, strong antifreeze and heat resistance, can insulate for several hours at a temperature of 200°C, has a strong heat insulation effect, will not be corroded by the electrolyte, and has good resilience, which can absorb and suppress the expansion problem caused by thermal runaway of the battery core. After the heat sealing layer melts at high temperature, the wood pulp sponge will quickly absorb a large amount of electrolyte, reducing the risk of side reactions between the electrolyte and the positive and negative electrodes. Furthermore, the thickness of the adsorption layer 4 is 40 to 60μm, preferably, the thickness of the adsorption layer 4 is 50μm, which can ensure that the electrolyte is fully adsorbed when the battery core has thermal runaway, thereby improving the safety of the battery core.

[0047] Continue to refer Figure 1 and Figure 2In the above embodiments, the barrier layer includes a barrier layer 2 and an outer resistance layer 3. The barrier layer 2 is made of aluminum alloy, and the outer resistance layer 3 is made of nylon. The barrier layer 2 is made of aluminum alloy, which has good pinhole resistance and double-sided composite properties, and can be stably formed after processing. Metal aluminum reacts with air at room temperature to form an oxide film, thereby preventing water vapor from penetrating and protecting the internal battery core. This layer is also the main structure of the composite packaging film for deep punching and deformation. The material of the outer resistance layer 3 is nylon, which has the properties of impact resistance, puncture resistance, friction resistance, heat resistance and insulation, and is used to protect the aluminum alloy from being scratched. The outer resistance layer 3 must also prevent air penetration while ensuring that the aluminum alloy has good deformation ability.

[0048] The working state of the above embodiment of the utility model is as follows Figure 4-A As shown, initially, the composite packaging film 0 and the unpackaged battery cell 6 are in a normal working state; then, when the battery cell temperature exceeds the set battery cell use temperature, as shown in FIG. Figure 4-B As shown, the heat seal layer 1 begins to melt and decompose, exposing the adsorption layer 4, which is in direct contact with the unpackaged battery cell 6. The adsorption layer 4 absorbs the electrolyte promptly and rapidly, and the adsorption layer 4 expands due to the absorption of the electrolyte. Figure 4-C shown.

[0049] When the above embodiment of the utility model is used to package the unpackaged battery cell 6, it includes:

[0050] The surface of the S1 barrier layer is coated with an adhesive having a thickness of 5 to 10 μm;

[0051] S2 designs the size of the unpackaged battery cell 6, places the adsorption layer 4 in the pit area 01 to be punched, and bonds it to the barrier layer through an adhesive, and applies the heat sealing layer 1 to the adsorption layer 4 and the barrier layer, and presses them into a roll by dry method, and the length of both sides of the heat sealing layer 1 exceeding the adsorption layer 4 is at least 5mm;

[0052] S3: cutting the aluminum-plastic film to a fixed size and punching it to form a hole, the depth of which is equal to the thickness of the unpackaged battery cell 6;

[0053] S4 packaging does not encapsulate 6 cells.

[0054] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed in the present invention shall still be covered by the claims of the present invention.

Claims

1. A composite packaging film for a battery cell, characterized in that: Along the first direction, there are arranged in sequence: a heat sealing layer, an adsorption layer and a barrier layer, wherein: The heat sealing layer is attached to the unpackaged battery cell and has a pit area to be punched, the pit area to be punched is opposite to the surface of the unpackaged battery cell, and the heat sealing layer can melt when the upper limit of the use temperature of the battery cell is exceeded; An adsorption layer capable of absorbing liquid, located in at least one of the pit areas to be flushed; The barrier layer is used to form a barrier for the unpackaged battery cell.

2. The composite packaging film according to claim 1, characterized in that: The adsorption layer is located in one of the pit areas to be flushed, and the heat sealing layer covered by the adsorption layer is 20-30 μm thinner than the heat sealing layer not covered by the adsorption layer.

3. The composite packaging film according to claim 2, characterized in that: The thickness of the heat-sealing layer covered by the absorption layer is 30-50 μm, and the thickness of the heat-sealing layer not covered by the absorption layer is 50-80 μm.

4. The composite packaging film according to claim 1, characterized in that: The heat sealing layer is a dry process heat sealing layer.

5. The composite packaging film according to claim 4, characterized in that: The dry process heat sealing layer is coated on the adsorption layer and the barrier layer. An adhesive layer is present between the adsorption layer or the dry process heat sealing layer and the barrier layer. The thickness of the adhesive layer is 5 to 20 μm.

6. The composite packaging film according to claim 5, characterized in that: The adhesive layer material is one of epoxy resin, polyurethane and thermoplastic polyolefin.

7. The composite packaging film according to claim 1, characterized in that: The heat sealing layer material is polypropylene.

8. The composite packaging film according to claim 1, characterized in that: The adsorption layer material is wood pulp sponge.

9. The composite packaging film according to claim 1, characterized in that: The adsorption layer has a thickness of 40 to 60 μm.

10. The composite packaging film according to claim 1, characterized in that: The barrier layer comprises a barrier layer and an outer barrier layer. The barrier layer is made of aluminum alloy, and the outer barrier layer is made of nylon.

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