A lithium battery insulating packaging film and preparation process and a fast-charging lithium battery

Abstract

The present invention discloses an insulating packaging film for a lithium battery, a preparation process, and a fast-charging lithium battery. The insulating packaging film is used between multiple stacked battery cells within the fast-charging lithium battery to provide insulation and bonding. The film comprises a heat-sealing layer, an adhesive layer, an insulating layer, an adhesive layer, and a heat-sealing layer, which are sequentially laminated from the inside out. The insulating layer is made of one of polyimide, polyethylene terephthalate, and polyethylene naphthalate, with a thickness of 5-30 μm. The heat-sealing layer is made of polypropylene or a combination of polypropylene and polyethylene, with a thickness of 10-40 μm. The adhesive layer is made of a modified polyolefin resin. The insulating packaging film of the present invention has a simple structure, is easy to manufacture, and is much thinner than aluminum film, significantly reducing the space occupied by the battery and increasing the battery's unit volume energy density by 4.75-10%, thereby improving the fast-charging speed of the lithium battery. The heat-sealing layer increases fluidity by adding polyethylene to the polypropylene, thereby improving the packaging efficiency of the battery cells.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery preparation, and in particular to a lithium battery insulating packaging film and a preparation process thereof, and a fast-charging lithium battery. Background Art

[0002] The current energy density of lithium batteries is difficult to increase significantly without the emergence of new breakthrough materials, resulting in the battery being unable to keep up with the speed of iteration of mobile phones and new energy vehicles, thus leading to fast charging.

[0003] Currently, the most effective method for fast charging is to increase the voltage. The voltage of a single battery is determined by the materials of its positive and negative electrodes. Therefore, by connecting multiple cells in parallel, the overall voltage is increased to achieve fast charging. However, existing soft-pack batteries are made by stacking multiple cells wrapped in aluminum-plastic film. This results in a thick multi-layer film between each cell. The thickness of a single layer of aluminum-plastic film is approximately 80μm, which reduces the energy density per unit volume of the battery compared to a single cell. Summary of the Invention

[0004] In order to solve the problem in the above-mentioned background technology that the space between multiple cells in the existing soft-pack battery is occupied by multiple layers of thick aluminum-plastic film, resulting in a relatively low energy density per unit volume, the present invention provides a lithium battery insulating packaging film, the thickness of which is much lower than that of the aluminum-plastic film, and is used between every two adjacent battery cells to improve the energy density per unit volume of the battery.

[0005] To achieve the above-mentioned purpose, the present invention provides a lithium battery insulating packaging film, characterized in that: the insulating packaging film is used between multiple stacked battery cells inside a fast-charging lithium battery to play an insulating and bonding role, including a heat-sealing layer, an adhesive layer, an insulating layer, an adhesive layer and a heat-sealing layer compounded in sequence from the inside to the outside, the insulating layer adopts one of polyimide, polyethylene terephthalate, and polyethylene naphthalate, and the thickness is set to 5-30μm, the heat-sealing layer adopts polypropylene or a combination of polypropylene and polyethylene, and the thickness is set to 10-40μm, and the adhesive layer adopts modified polyolefin resin.

[0006] As a further improvement of the present technology, the heat sealing layer is configured as a single layer or multi-layer structure.

[0007] As a further improvement of the present technology, the thickness of the heat sealing layer is set to 20-40 μm.

[0008] As a further improvement of the present technology, the melting point of the heat sealing layer material is set to 130-160° C., and the melt index is set to 6-7.8.

[0009] As a further improvement of the present technology, the thickness of the insulating layer is set to 6-20 μm.

[0010] The present invention also provides a process for preparing the above-mentioned lithium battery insulating packaging film, which is characterized by comprising the following steps:

[0011] 1) The insulating layer substrate is rolled into the first substrate position on the dry laminating machine, and the insulating layer substrate is sent to the first coating area, and the adhesive layer material is coated on one side of the insulating layer substrate, and the adhesive layer is dried;

[0012] 2) The heat-sealing layer substrate roll is loaded into the second substrate position of the dry laminating machine and thermally bonded to the adhesive layer dried in step 1 to obtain an insulating layer / adhesive layer / heat-sealing layer semi-finished product 1;

[0013] 3) sending the semi-finished product obtained in step 2) to a second coating area, coating the other side of the insulating layer substrate with an adhesive layer material, and drying the adhesive layer;

[0014] 4) Loading another heat-sealing layer substrate roll into the third substrate position on the dry laminating machine and thermally laminating it to the adhesive layer dried in step 3 to obtain a heat-sealing layer / adhesive layer / insulating layer / adhesive layer / heat-sealing layer semi-finished product II;

[0015] 5) The semi-finished product obtained in step 4) is placed in an oven for curing, taken out, and cut into finished insulating packaging films.

[0016] As a further improvement of this process, in step 5), the aging temperature is set to 60° C. and the aging time is set to 4 days.

[0017] As a further improvement of this process, the insulating layer substrate roll is a polyimide film with a thickness of 6-20 μm.

[0018] As a further improvement of this process, the heat-sealing layer substrate roll is a 90% polypropylene and 10% polyethylene blend film with a thickness of 20-40 μm and a melting point of 148°C.

[0019] The present invention also provides a fast-charging lithium battery, characterized in that: a plurality of battery cells are stacked in the fast-charging lithium battery, and the plurality of battery cells are insulated and bonded with the insulating packaging film prepared by the above process.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The insulating packaging film of the present invention has a simple structure, is easy to manufacture, and is much thinner than aluminum plastic film, which greatly reduces the space occupied by the battery and increases the battery's energy density per unit volume by 4.75-10%, thereby increasing the fast charging speed of the lithium battery;

[0022] 2. The insulating layer is made of polyimide, which has good bonding performance with the heat sealing layer and requires a temperature above 195°C to sol;

[0023] 3. The heat-sealing layer increases the fluidity by adding polyethylene to polypropylene. While ensuring the packaging tension, the packaging temperature is reduced, which can improve the packaging efficiency of downstream battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1 is a schematic diagram of the structure of the insulating packaging film according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of a fast-charging lithium battery having two stacked cells in Examples 1 to 3 of the present invention;

[0026] Figure 3 This is a schematic diagram of the structure of a fast-charging lithium battery with two stacked cells in the prior art;

[0027] Figure 4 This is a schematic diagram of the structure of a fast-charging lithium battery having four stacked cells in Examples 4 to 7 of the present invention;

[0028] Figure 5 This is a schematic diagram of the structure of a fast-charging lithium battery with four stacked cells in the existing technology.

[0029] In the figure: 1. electrode, 2. aluminum-plastic film, 3. battery cell, 4. insulating packaging film, 401. insulating layer, 402. adhesive layer, 403. heat sealing layer. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0031] like Figure 1 As shown, the preparation process of the lithium battery insulating packaging film embodiment of the present invention includes the following steps:

[0032] 1) The insulating layer 401 substrate is rolled into the first substrate position on the dry laminating machine, and the insulating layer 401 substrate is sent to the first coating area, and the adhesive layer 402 material is coated on one side of the insulating layer 401 substrate, and the adhesive layer 402 is dried;

[0033] 2) The heat-sealing layer 403 substrate is rolled into the second substrate position on the dry laminating machine and thermally bonded to the adhesive layer 402 dried in step 1 to obtain a semi-finished product of the insulating layer 401 / adhesive layer 402 / heat-sealing layer 403;

[0034] 3) The semi-finished product obtained in step 2) is sent to the second coating area, where the adhesive layer 402 material is coated on the other side of the insulating layer 401 substrate, and the adhesive layer 402 is dried;

[0035] 4) Another heat-sealing layer 403 substrate roll is loaded into the third substrate position of the dry laminating machine and thermally bonded to the adhesive layer 402 dried in step 3 to obtain a heat-sealing layer 403 / adhesive layer 402 / insulating layer 401 / adhesive layer 402 / heat-sealing layer 403 semi-finished product II;

[0036] 5) The semi-finished product obtained in step 4) is placed in an oven for curing at 60° C. for 4 days, taken out, and cut into finished insulating packaging films.

[0037] Example 1:

[0038] A lithium battery insulation packaging film: the insulation layer 401 is a polyimide film with a thickness of 12μm; the adhesive layer 402 is a modified polyolefin resin with a thickness of 4-5μm; the heat sealing layer 403 is a three-layer polypropylene film with a melting point of 160℃ and a thickness of 25μm.

[0039] like Figure 1 、 2 As shown, the fast-charge lithium battery assembled in this embodiment 1 has two cells 3 stacked together, and the thickness of the insulating packaging film is 42 μm, which is consistent with the current technology (such as Figure 3 ), the thickness of the fast-charging lithium battery in Example 1 is reduced by 118 μm, and the energy density per unit volume of the lithium battery is increased by 5.9%.

[0040] Example 2:

[0041] A lithium battery insulation packaging film: the insulation layer 401 is a polyethylene terephthalate film with a thickness of 12μm; the adhesive layer 402 is a modified polyolefin resin with a thickness of 4-5μm; the heat sealing layer 403 is a three-layer polypropylene film with a thickness of 25μm and a melting point of 160℃.

[0042] like Figure 1 、 2 As shown, the fast-charge lithium battery assembled in this embodiment 2 has two cells 3 stacked together, and the thickness of the insulating packaging film is 42 μm, which is consistent with the current technology (such as Figure 3 ), the thickness of the fast-charging lithium battery in Example 2 is reduced by 118 μm, and the energy density per unit volume of the lithium battery is increased by 5.9%.

[0043] Example 3:

[0044] A lithium battery insulation packaging film: the insulation layer 401 is a polyethylene naphthalate film with a thickness of 12μm; the adhesive layer 402 is a modified polyolefin resin with a thickness of 4-5μm; the heat sealing layer 403 is a three-layer polypropylene film with a melting point of 160°C and a thickness of 25μm.

[0045] like Figure 1 、 2As shown, the fast-charge lithium battery assembled in this embodiment 3 has two cells 3 stacked together, and the thickness of the insulating packaging film is 42 μm, which is consistent with the current technology (such as Figure 3 ), the thickness of the fast-charging lithium battery in Example 3 is reduced by 118 μm, and the energy density per unit volume of the lithium battery is increased by 5.9%.

[0046] Performance testing: Testing the bonding performance of three different insulating layer 401 materials.

[0047] Table 1 Effects of different materials of insulation layer 401 on interlayer bonding and packaging temperature

[0048]

[0049] Table 1 shows that at the same melting temperature, the polyimide material of the insulating layer 401 used in Example 1 has the best and most optimal bonding performance with the heat sealing layer.

[0050] Example 4:

[0051] A lithium battery insulation packaging film: the insulation layer 401 is a polyimide film with a thickness of 6μm; the adhesive layer 402 is a modified polyolefin resin with a thickness of 4-5μm; the heat sealing layer 403 is a three-layer polypropylene film with a melting point of 130°C and a thickness of 20μm.

[0052] like Figure 1 、 4 As shown, the fast-charge lithium battery assembled in this embodiment 4 has four cells 3 stacked together, and the thickness of the insulating packaging film is 31 μm, which is consistent with the current technology (such as Figure 5 ), the thickness between two adjacent battery cells 3 is reduced by 129μm, the thickness of the fast-charging lithium battery is reduced by 387μm, and the energy density per unit volume of the lithium battery is increased by 6.45%.

[0053] Example 5:

[0054] A lithium battery insulation packaging film: the insulation layer 401 is a polyimide film with a thickness of 6μm; the adhesive layer 402 is a modified polyolefin resin with a thickness of 4-5μm; the heat sealing layer 403 is a three-layer polypropylene film with a melting point of 148°C and a thickness of 20μm.

[0055] like Figure 1 、 4 As shown, the fast-charge lithium battery assembled in this embodiment 5 has four cells 3 stacked together, and the thickness of the insulating packaging film is 31 μm, which is consistent with the current technology (such as Figure 5 ), the thickness between two adjacent battery cells is reduced by 129μm, the thickness of the fast-charging lithium battery is reduced by 387μm, and the energy density per unit volume of the lithium battery is increased by 6.45%.

[0056] Example 6:

[0057] A lithium battery insulation packaging film: the insulation layer 401 is a polyimide film with a thickness of 6μm; the adhesive layer 402 is a modified polyolefin resin with a thickness of 4-5μm; the heat sealing layer 403 is a three-layer polypropylene film with a melting point of 160°C and a thickness of 20μm.

[0058] like Figure 1 、 4 As shown, the fast-charge lithium battery assembled in this embodiment 6 has four cells 3 stacked together, and the thickness of the insulating packaging film is 31 μm, which is consistent with the current technology (such as Figure 5 ), the thickness between two adjacent battery cells is reduced by 129μm, the thickness of the fast-charging lithium battery is reduced by 387μm, and the energy density per unit volume of the lithium battery is increased by 6.45%.

[0059] Performance testing: Testing the bonding performance of three heat seal layer 403 materials with different melting points.

[0060] Table 2 Different melting point sols and peeling force of heat seal layer 403

[0061] Serial number project Example 1 Example 4 Example 5 Example 6 1 Heat sealing sol temperature with aluminum plastic film ℃ (0.3MPa-3S) 195 180 186 192 2 Heat seal peeling force with aluminum-plastic film N / 15mm 65.235 56.484 62.512 62.990

[0062] Table 2 shows that when selecting heat-sealing layer materials with different melting points, the peeling force of the material with a melting point of 130°C is relatively low, while the others are all above 60. According to the downstream packaging temperature, Example 5 is the best.

[0063] Example 7:

[0064] A lithium battery insulation packaging film: the insulation layer 401 is a polyimide film with a thickness of 20 μm; the adhesive layer 402 is a modified polyolefin resin with a thickness of 4-5 μm; the heat sealing layer 403 is a single-layer 90% polypropylene and 10% polyethylene blend film with a melting point of 148°C and a thickness of 40 μm.

[0065] like Figure 1 、 4 As shown, the fast-charge lithium battery assembled in this embodiment 7 has four cells 3 stacked together, and the thickness of the insulating packaging film is 65 μm, which is consistent with the current technology (such as Figure 5 ), the thickness between two adjacent battery cells is reduced by 95μm, the thickness of the fast-charging lithium battery is reduced by 387μm, and the energy density per unit volume of the lithium battery is increased by 4.75%.

[0066] Performance testing: Testing the bonding performance of different melt finger heat seal layer 403 materials.

[0067] Table 3 Effect of melt index of heat seal layer 403 on packaging temperature

[0068] Serial number project Example 5 Example 7 1 Heat seal layer melt index 230℃-2.16kg 6 7.8 1 Heat sealing sol temperature with aluminum plastic film ℃ (0.3MPa-3S) 186 181 2 Heat seal peeling force with aluminum-plastic film N / 15mm 65.235 64.862

[0069] As shown in Table 3, the heat-sealing layer 403 of Example 7 increases fluidity by adding 10% polyethylene to polypropylene. While ensuring the packaging tension, the packaging temperature is reduced, which can improve the packaging efficiency of the downstream battery cells.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A fast-charging lithium battery, characterized in that: The fast-charging lithium battery is provided with multiple stacked battery cells, the outer sides of the multiple battery cells are packaged with aluminum-plastic film, and a layer of insulating packaging film is used to insulate and bond the multiple battery cells. The insulating packaging film includes a heat-sealing layer, an adhesive layer, an insulating layer, an adhesive layer and a heat-sealing layer compounded in sequence from the inside to the outside. The insulating layer is made of one of polyimide, polyethylene terephthalate and polyethylene naphthalate, and the thickness is set to 5-30 μm. The heat-sealing layer is made of polypropylene or a combination of polypropylene and polyethylene, and the thickness is set to 10-40 μm. The adhesive layer is made of modified polyolefin resin. The inner and outer heat-sealing layers at both ends of the insulating packaging film are heat-sealed with the aluminum-plastic film packaged on the outside of the upper battery cell and the lower battery cell respectively. The melting point of the heat sealing layer material is set to 130-160°C, and the melt index is set to 6-7.8; The insulating packaging film preparation process comprises the following steps: 1) The insulating layer substrate is rolled into the first substrate position on the dry laminating machine, and the insulating layer substrate is sent to the first coating area, and the adhesive layer material is coated on one side of the insulating layer substrate, and the adhesive layer is dried; 2) The heat-sealing layer substrate roll is loaded into the second substrate position of the dry laminating machine and thermally bonded to the adhesive layer dried in step 1) to obtain an insulating layer / adhesive layer / heat-sealing layer semi-finished product 1; 3) sending the semi-finished product obtained in step 2) to the second coating area, coating the other side of the insulating layer substrate with an adhesive layer material, and drying the adhesive layer; 4) Loading another heat-sealing layer substrate roll into the third substrate position on the dry laminating machine and thermally laminating it with the adhesive layer dried in step 3) to obtain a heat-sealing layer / adhesive layer / insulating layer / adhesive layer / heat-sealing layer semi-finished product II; 5) The semi-finished product obtained in step 4) is placed in an oven for curing, taken out, and cut into finished insulating packaging films.

2. A fast-charging lithium battery according to claim 1, characterized in that: The heat sealing layer is configured as a single layer or a multi-layer structure.

3. A fast-charging lithium battery according to claim 2, characterized in that: The thickness of the heat sealing layer is set to 20-40 μm.

4. The fast-charging lithium battery according to claim 1, characterized in that: The thickness of the insulating layer is set to 6-20 μm.

5. The fast-charging lithium battery according to claim 1, characterized in that: In step 5), the aging temperature is set to 60° C. and the aging time is set to 4 days.

6. The fast-charging lithium battery according to claim 1, characterized in that: The insulating layer substrate roll is a polyimide film with a thickness of 6-20 μm.

7. The fast-charging lithium battery according to claim 1, characterized in that: The heat-sealing layer substrate roll is a 90% polypropylene and 10% polyethylene blended film with a thickness of 20-40 μm and a melting point of 148° C.

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