Composite aluminum plastic film and lithium ion battery

Abstract

The utility model belongs to the technical field of battery production and manufacturing, and particularly relates to a composite aluminum plastic film and a lithium ion battery, which comprise an inner layer, a middle layer and an outer layer which are sequentially stacked, the inner layer and the outer layer are respectively adhered to two surfaces of the middle layer in the thickness direction; a plurality of honeycomb-shaped groove positions are formed in the surface of the middle layer, and exhaust holes are formed in the bottoms of the groove positions. According to the utility model, by optimizing the aluminum plastic film structure, gas generated by temperature rise can be exhausted, and the problem of internal short circuit ignition caused by difficult exhaust of gas in the battery cell is solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of battery production and manufacturing, and particularly relates to a composite aluminum-plastic film and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries have the advantages of high specific energy, high specific power, high voltage platform, low self-discharge, long cycle life, low environmental pollution and no memory effect. They have been widely used in related fields such as mobile phones, computers, electric vehicles, military, and space technology. However, while bringing benefits to mankind, lithium-ion batteries also pose some safety hazards. For example, under abusive conditions such as overcharging, over-discharging, short-circuiting, squeezing, puncturing, and high temperature, lithium-ion batteries may catch fire or explode. The existing aluminum-plastic film is composed of a resin layer, an aluminum layer and a protective layer, and the layers are bonded together by an adhesive. When the external temperature of the battery is relatively high, the electrolyte inside the battery cell will decompose, generating gases such as ethylene, carbon dioxide, and oxygen. As time goes by, the amount of generated gas increases, and the internal pressure of the battery also increases.

[0003] In the process of implementing the present utility model, the inventor found that there are at least the following problems in the prior art

[0004] When the battery overheats and releases too much heat in a short time, the existing aluminum-plastic film structure cannot discharge the heat, which may cause the battery cell to catch fire and pose a battery safety problem. Summary of the Utility Model

[0005] One of the purposes of the present utility model is to provide a composite aluminum-plastic film to solve the problem of difficult gas discharge inside the battery cell and internal short-circuit fire caused by the optimization of the aluminum-plastic film structure, which can discharge the gas generated due to temperature rise.

[0006] In order to achieve the above purpose, the present utility model adopts the following technical solutions:

[0007] A composite aluminum-plastic film includes an inner layer, an intermediate layer and an outer layer which are sequentially stacked; the inner layer and the outer layer are respectively bonded to two sides of the intermediate layer in the thickness direction; a plurality of honeycomb-shaped slots are arranged on the surface of the intermediate layer, and exhaust holes are arranged at the bottoms of the slots.

[0008] Preferably, a plurality of the slots are arranged at equal intervals in sequence to form a plurality of nest groups, and two adjacent nest groups are arranged at equal intervals.

[0009] Preferably, the depth of the slot is H, the diameter of the circumscribed circle of the slot is R, the cross-sectional area is S1, and the area of the exhaust hole is S2, satisfying the relationship: H≤2μm, 1.74×10 9 S2<S1<1.44×10 10S2, 0.01π nm 2 0.01π nm < S2 < 0.36π nm 2 。

[0010] Preferably, the depth of the slot is H, the diameter of the circumscribed circle of the slot is R, the cross-sectional area is S1, and the area of the exhaust hole is S2, satisfying the relationship: 2 < H ≤ 4 μm, 4×10 8 S2 < S1 < 6.25×10 8 S2, 0.01π nm 2 0.01π nm < S2 < 0.36π nm 2 。

[0011] Preferably, the horizontal spacing between two adjacent slots is d, the vertical spacing between two adjacent slots is d, and the spacing between two adjacent nest groups is D, satisfying the relationship: D = 5d1, d1 > d2.

[0012] Preferably, a first adhesive layer is provided between the inner layer and the intermediate layer, and a second adhesive layer is provided between the intermediate layer and the outer layer.

[0013] Preferably, a protective layer is provided between the intermediate layer and the second adhesive layer.

[0014] Preferably, the shape of the slot is hexagonal prism or conical, the intermediate layer is an aluminum layer, and the outer layer is a nylon layer.

[0015] Preferably, the bottom of the slot has an inclined surface, the inclined surface is arranged around the exhaust hole, and the included angle between the inclined surface and the exhaust hole is 10 - 25°.

[0016] The second object of the present invention is to provide a lithium-ion battery including the above-mentioned composite aluminum-plastic film.

[0017] One of the above technical solutions has the following beneficial effects

[0018] By optimizing the structure of the aluminum-plastic film, the present invention designs slots on the surface of the intermediate layer, and exhaust holes are provided at the bottom of the slots. When the temperature inside the battery cell rises, the electrolyte and the like generate gas due to the temperature rise. The high-temperature gas can pass through the opening of the slot and pass through the exhaust hole, and is discharged from the exhaust hole, avoiding the situation of fire and combustion due to excessive temperature of the battery cell, and solving the problem of internal short circuit and fire caused by difficult discharge of gas inside the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The features, advantages and technical effects of the exemplary embodiments of the present invention will be described below with reference to the drawings.

[0020] Figure 1 It is a schematic structural diagram of the present invention.

[0021] Figure 2 Schematic diagram of the arrangement of the slots of the present utility model.

[0022] Figure 3 Cross-sectional view of the slot of the present utility model.

[0023] Figure 4 Schematic diagram of the lithium-ion battery of the present utility model.

[0024] Among them, the reference numerals are explained as follows:

[0025] 1 - Inner layer;

[0026] 2 - Middle layer; 20 - Nest group; 21 - Slot; 211 - Exhaust hole;

[0027] 3 - Outer layer;

[0028] 4 - First adhesive layer;

[0029] 5 - Second adhesive layer;

[0030] H - Depth of the slot; R - Outer circumferential diameter of the slot.

[0031] d1 - Horizontal distance between two adjacent slots; d2 - Vertical distance between two adjacent slots; D - Distance between two adjacent nest groups. Detailed implementation manners

[0032] As certain terms are used in the specification and claims to refer to particular components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use the difference in names as a way to distinguish components, but use the difference in functions of components as the criterion for distinction. As the term "comprising" mentioned throughout the specification and claims is an open-ended term, it should be interpreted as "including but not limited to". "Substantially" means within an acceptable error range, and those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0033] In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0034] In a utility model, unless otherwise clearly defined and limited, terms such as "installation", "connection", "linkage", "fixation" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the utility model can be understood according to specific circumstances.

[0035] The following further describes the present utility model in detail with reference to the accompanying drawings, but does not limit the present utility model.

[0036] Embodiment 1

[0037] When the battery overheats and releases too much heat in a short time, the existing aluminum-plastic film structure cannot discharge the heat, which may cause the battery core to catch fire and pose a battery safety problem.

[0038] The composite aluminum-plastic film of the present utility model includes an inner layer 1, an intermediate layer 2, and an outer layer 3 that are sequentially stacked; the inner layer 1 and the outer layer 3 are respectively bonded to both sides of the intermediate layer 2 in the thickness direction; a plurality of honeycomb-shaped slots 21 are provided on the surface of the intermediate layer 2, and exhaust holes 211 are provided at the bottom of the slots 21. By optimizing the structure of the aluminum-plastic film, the present utility model designs slots 21 on the surface of the intermediate layer 2, and exhaust holes 211 are provided at the bottom of the slots 21. When the temperature inside the battery core rises, the electrolyte and the like generate gas due to the temperature rise. The high-temperature gas can pass through the opening of the slot 21 and pass through the exhaust hole 211, and is discharged from the exhaust hole 211, avoiding the situation of the battery core catching fire and burning due to excessive temperature, and solving the problem of internal short circuit and fire caused by the difficulty of discharging the gas inside the battery core.

[0039] It should be noted that: The slot 21 is a hollow structure with an opening at the top and an exhaust hole 211 at the bottom. The diameter of the circumscribed circle of the opening is R, which is slightly larger than the exhaust hole 211. The opening of the slot 21 faces the inner layer 1, and the exhaust hole 211 faces the outer layer 3. It has a certain accommodation space and can dilute the space for the expansion of the battery cell to a certain extent. When the external temperature of the battery cell is relatively high, such as above 100 °C, the electrolyte inside the battery cell will decompose, generating gases such as ethylene, carbon dioxide, and oxygen. As time goes by, the generated gases increase, and the internal pressure of the battery becomes larger, which can prompt the gases to slowly discharge from the exhaust hole 211, helping to reduce the internal pressure of the battery cell. At the same time, the high-temperature gases will also discharge from the exhaust hole 211, which can release the heat inside the battery and prevent the situation of safety accidents caused by the combustion of the battery cell due to excessive internal temperature. In addition, the slot 21 is in a honeycomb shape, and the shape of the slot 21 is a hexagonal prism or a cone, preferably a hexagonal prism. The middle layer 2 is a metal layer, preferably an aluminum layer. The aluminum layer can be an aluminum sheet or an aluminum plate. The outer layer 3 is a nylon layer, and the inner layer 1 is polypropylene, which plays the role of heat-sealing the aluminum-plastic film and can also be other materials, which are not limited here.

[0040] In the composite aluminum-plastic film according to the present invention, a plurality of honeycomb-shaped slots 21 are arranged at equal intervals in sequence to form a plurality of nest groups 20, and two adjacent nest groups 20 are arranged at equal intervals. In this embodiment, 16 slots 21 are divided into two columns, and the two columns of slots 21 are arranged in sequence. The horizontal distance between two adjacent slots 21 is the same, and the vertical distance between two adjacent slots 21 is the same, forming one of the nest groups 20. The slots 21 of the other nest groups 20 also adopt this arrangement structure, and the distance between two adjacent nest groups 20 is the same, ensuring that a plurality of honeycomb-shaped slots 21 are evenly distributed on the surface of the middle layer 2, which helps to improve the gas discharge effect of the middle layer 2.

[0041] In the composite aluminum-plastic film according to the present invention, the depth of the slot 21 is H, the diameter of the circumscribed circle of the slot 21 is R, the cross-sectional area is S1, and the area of the exhaust hole 211 is S2, satisfying the relationship: H ≤ 2 μm, 1.74×10 9 S2 < S1 < 1.44×10 10 S2, 0.01πnm 2 < S2 < 0.36πnm 2 . For example, the depth H of the slot 21 is 2 μm, 1.9 μm, 1.8 μm, 1.7 μm, 1.6 μm, 1.5 μm, 1.4 μm, 1.3 μm, 1.2 μm, 1.1 μm, 1 μm, etc. Limiting the depth of the slot 21 can prevent the depth of the slot 21 from being too large and affecting the overall mechanical strength of the middle layer 2. Limiting the diameter of the circumscribed circle of the slot 21 can prevent the diameter of the circumscribed circle of the slot 21 from being too large and affecting the overall mechanical strength of the middle layer 2; Limiting the area of the exhaust hole 211 can prevent the area of the exhaust hole 211 from being too small and affecting the discharge of high-temperature gases inside the battery.

[0042] In the composite aluminum-plastic film according to the present utility model, the horizontal distance between two adjacent slot positions 21 is d1, the vertical distance between two adjacent slot positions 21 is d2, and the distance between two adjacent nest groups 20 is D, satisfying the relationship: D = 5d1, d1 > d2. In this embodiment, by controlling the horizontal distance and the vertical distance between two adjacent slot positions 21, it is ensured that two adjacent slot positions 21 do not overlap, and sufficient distance is guaranteed between two adjacent slot positions 21. In addition, by controlling the distance between two adjacent nest groups 20, it is prevented that the distance between two adjacent nest groups 20 is too large, which affects the heat release effect of the composite aluminum-plastic film.

[0043] In the composite aluminum-plastic film according to the present utility model, a first adhesive layer 4 is provided between the inner layer 1 and the intermediate layer 2, and a second adhesive layer 5 is provided between the intermediate layer 2 and the outer layer 3. In this embodiment, the first adhesive layer 4 is formed by extrusion bonding to bond the inner layer 1 and the intermediate layer 2, and the first adhesive layer 4 is formed under the state of slowly rising temperature and pressure. The second adhesive layer 5 is formed by extrusion bonding to bond the intermediate layer 2 and the outer layer 3. The first adhesive layer 4 and the second adhesive layer 5 are adhesives, and the adhesive is preferably a polypropylene porous foaming material. In addition, in some embodiments, a protective layer is provided between the intermediate layer 2 and the second adhesive layer 5 to protect the intermediate layer 2. In addition, when bonding the inner layer 1 and the intermediate layer 2, a part of the first adhesive layer 4 will fill into the slot position 21. When the temperature inside the battery cell rises to a preset temperature, the gas can break through this part of the first adhesive layer 4, which can be understood as the slot position 21 automatically opening holes, and the heat inside the battery cell is dissipated to the outside of the battery cell.

[0044] In the composite aluminum-plastic film according to the present utility model, the bottom of the slot position 21 has an inclined surface, the inclined surface is arranged around the exhaust hole 211, and the included angle between the inclined surface and the exhaust hole 211 is 10 - 25°. In this embodiment, the bottom of the slot position 21 is conical, and the inclined surface can be understood as the side wall of the cone. By limiting the included angle between the inclined surface and the exhaust hole 211, it is helpful for the gas to be discharged along the inclined surface, thereby improving the exhaust efficiency of the slot position 21.

[0045] The working principle of the present utility model is:

[0046] The present utility model optimizes the structure of the aluminum-plastic film, designs the slot position 21 on the surface of the intermediate layer 2, and the bottom of the slot position 21 is provided with an exhaust hole 211. When the temperature inside the battery cell rises, the electrolyte and the like generate gas due to the temperature rise. The high-temperature gas can pass through the slot position 21 and pass through the exhaust hole 211 and be discharged from the exhaust hole 211, avoiding the situation that the battery cell catches fire and burns due to excessive temperature, and solving the problem of internal short circuit and fire caused by the difficulty of discharging the gas inside the battery cell.

[0047] It should be noted that: The distribution position of the slot 21 of the composite aluminum-plastic film can be in non-welding areas such as the main body of the battery cell, the corners, and the bottom, which helps to reduce the risk of false soldering or liquid leakage in the battery cell.

[0048] In addition, the preparation method of the composite aluminum-plastic film in this embodiment includes the following steps:

[0049] Step 1: Perform surface treatment on one side of the aluminum layer;

[0050] Step 2: Use a mold to form a honeycomb-shaped slot 21 on the surface of the aluminum layer, and form an exhaust hole 211 at the bottom of the slot 21. The exhaust hole 211 is a micropore or a prefabricated hole groove;

[0051] Step 3: Bond the aluminum layer and the inner layer 1 with an adhesive;

[0052] Step 4: Perform surface treatment on the other side of the aluminum layer;

[0053] Step 5: Under the state of slowly increasing the temperature and pressure, bond the aluminum layer and the outer layer 3 with an adhesive, and finally complete the preparation of the composite aluminum-plastic film.

[0054] Example 2

[0055] Different from Example 1: In this embodiment, the depth of the slot 21 is H, the diameter of the circumscribed circle of the slot 21 is R, the cross-sectional area is S1, and the area of the exhaust hole 211 is S2, satisfying the relational expression: 2 < H ≤ 4 μm, 4×10 8 S2 < S1 < 6.25×10 8 S2, 0.01πnm 2 <S2<0.36πnm 2 For example, the depth H of the slot 21 is 2 μm, 1.9 μm, 1.8 μm, 1.7 μm, 1.6 μm, 1.5 μm, 1.4 μm, 1.3 μm, 1.2 μm, 1.1 μm, 1 μm, etc. Limiting the depth of the slot 21 can prevent the depth of the slot 21 from being too large and affecting the overall mechanical strength of the intermediate layer 2; limiting the diameter of the circumscribed circle R of the slot 21 can prevent the circumscribed circle of the slot 21 from being too large and affecting the overall mechanical strength of the intermediate layer 2; limiting the area of the exhaust hole 211 can prevent the area of the exhaust hole 211 from being too small and affecting the discharge of high-temperature gas in the battery, ensuring that each slot 21 of the composite aluminum-plastic film can achieve the exhaust function.

[0056] Other structures are the same as those in Example 1 and will not be elaborated here.

[0057] Comparative Example 1

[0058] This embodiment adopts a conventional aluminum-plastic film structure, and the aluminum-plastic film is composed of a resin layer, an aluminum layer, and a protective layer.

[0059] The battery cells made of the aluminum-plastic films of Example 1, Example 2 and Comparative Example 1 were subjected to a hot box performance test. The temperature was increased to a preset temperature (such as 130 °C, 135 °C, 140 °C, etc.) at a preset rate, and the surface temperature of the battery cell was monitored in real time. If the battery cell did not catch fire, it passed the test.

[0060] Table 1. Comparison table of the hot box performance test results of the battery cells of Example 1, Example 2 and Comparative Example 1

[0061]

[0062] As can be seen from Table 1, the hot box performance test results of the battery cells of Example 1 and Example 2 are both better than those of the battery cell of Comparative Example 1. Among them, the depth of slot 21 in Example 1 is smaller, and the cross-sectional area of slot 21 is larger, resulting in a better improvement effect on the hot box performance; the depth of slot 21 in Example 2 is larger, and the cross-sectional area of slot 21 is smaller, so the improvement effect on the hot box is slightly worse than that of Example 1; Comparative Example 1 uses a common aluminum-plastic film, and the hot box performance result is poor. It shows that the present invention optimizes the structure of the aluminum-plastic film, designs slot 21 on the surface of the intermediate layer 2, and an exhaust hole 211 is provided at the bottom of slot 21. When the internal temperature of the battery cell rises, gases such as electrolyte are generated due to the temperature rise. The high-temperature gases can pass through slot 21 and pass through exhaust hole 211 and be discharged from exhaust hole 211, avoiding the situation of the battery cell catching fire and burning due to excessive temperature, and solving the problem of internal short circuit and fire caused by the difficulty of discharging the internal gas of the battery cell. In addition, when bonding the inner layer 1 and the intermediate layer 2, part of the first adhesive layer 4 will fill into slot 21. Since the depth of slot 21 in the composite aluminum-plastic film of Example 1 is smaller and the cross-sectional area of slot 21 is larger, the adhesive layer filled in slot 21 is thinner and less in quantity. When the internal air pressure of the battery cell increases, the gas can easily pass through the exhaust hole 211 of the composite aluminum-plastic film, quickly reducing the temperature of the battery cell and avoiding the battery cell catching fire and burning. In contrast, the depth of slot 21 in Example 2 is larger and the cross-sectional area of slot 21 is smaller, making the adhesive layer filled in slot 21 thicker and tighter. Only when the internal air pressure of the battery cell increases to a certain extent can the gas pass through the exhaust hole 211 of the composite aluminum-plastic film to take out the heat and reduce the safety risk. Therefore, the hot box performance result of the battery cell of Example 1 is better than that of the battery cell of Example 2.

[0063] In addition, a lithium-ion battery includes a battery cell, and the preparation method of the battery cell includes:

[0064] (1) Preparation of the positive electrode plate

[0065] The positive electrode material lithium cobaltate, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were fully stirred and mixed evenly in an N-methylpyrrolidone solvent system at a mass ratio of 98:1.2:0.8, and then coated on aluminum foil. After drying, rolling, and slitting, the positive electrode plate was obtained.

[0066] (2) Preparation of the negative electrode sheet

[0067] The negative electrode material, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are mixed in a mass ratio of 98.1:0.5:0.7:0.7 and stirred evenly in a deionized water solvent system, and then coated on a copper foil. After drying, rolling, and slitting, the negative electrode sheet is obtained.

[0068] (3) Preparation of the separator

[0069] A polyethylene (PE) porous polymer film is used as the separator.

[0070] (4) Preparation of the electrolyte

[0071] A solution prepared by mixing lithium salt LiPF6 with non-aqueous organic solvents (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): vinylene carbonate (VC)) = 25:25:15:31:4 (mass ratio)) in a mass ratio of 8:92 is used as the electrolyte of the lithium-ion battery.

[0072] (5) Preparation of the lithium-ion secondary battery

[0073] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play a role in safety isolation, and then wound to obtain an electrode core. Then, the electrode core is placed in the composite aluminum-plastic film of the present invention, the electrolyte is injected and sealed to obtain the lithium-ion battery of the present invention.

[0074] According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments, and any obvious improvements, substitutions, or variations made by those skilled in the art based on the present invention fall within the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A composite aluminum-plastic film, characterized in that, It includes an inner layer (1), a middle layer (2) and an outer layer (3) which are stacked in sequence; The inner layer (1) and the outer layer (3) are respectively adhered to both sides in the thickness direction of the middle layer (2); A plurality of honeycomb-shaped slots (21) are provided on the surface of the middle layer (2), and exhaust holes (211) are provided at the bottoms of the slots (21).

2. The composite aluminum-plastic film according to claim 1, wherein: A plurality of the slots (21) are arranged at equal intervals in sequence to form a plurality of nest groups (20), and two adjacent nest groups (20) are arranged at equal intervals.

3. The composite aluminum-plastic film according to claim 1 or 2, characterized in that: The depth of the slot (21) is H, the diameter of the circumscribed circle of the slot (21) is R, the cross-sectional area is S1, and the area of the exhaust hole (211) is S2, satisfying the relational expression: H ≤ 2 μm, 1.74×10 9 S2 < S1 < 1.44×10 10 S2, 0.01π nm 2 <S2<0.36π nm 2 .

4. A composite aluminum-plastic film according to claim 1 or 2, characterized in that: The depth of the slot (21) is H, the diameter of the circumscribed circle of the slot (21) is R, the cross-sectional area is S1, and the area of the exhaust hole (211) is S2, satisfying the relationship: 2 < H ≤ 4 μm, 4×10 8 S2 < S1 < 6.25×10 8 S2, 0.01π nm 2 <S2<0.36π nm 2 .

5. The composite aluminum-plastic film according to claim 2, wherein: The horizontal distance between two adjacent slots (21) is d1, the vertical distance between two adjacent slots (21) is d2, and the distance between two adjacent nest groups (20) is D, satisfying the relational expression: D = 5d1, d1 > d2.

6. A composite aluminum-plastic film according to claim 1 or 2, characterized in that: A first adhesive layer (4) is provided between the inner layer (1) and the middle layer (2), and a second adhesive layer (5) is provided between the middle layer (2) and the outer layer (3).

7. The composite aluminum-plastic film according to claim 6, characterized in that: A protective layer is provided between the middle layer (2) and the second adhesive layer (5).

8. A composite aluminum-plastic film according to claim 1 or 2, characterized in that: The shape of the slot (21) is hexagonal prism or conical, the middle layer (2) is an aluminum layer, and the outer layer (3) is a nylon layer.

9. A composite aluminum-plastic film according to claim 1 or 2, characterized in that: The bottom of the slot (21) has an inclined surface, the inclined surface is arranged around the exhaust hole (211), and the included angle between the inclined surface and the exhaust hole (211) is 10 - 25°.

10. A lithium-ion battery, characterized in that: It includes the composite aluminum-plastic film according to any one of claims 1 - 9.

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