Insulation paste and battery

Abstract

The invention relates to the technical field of batteries, in particular to insulating glue and a battery comprising the insulating glue. The insulating glue at least comprises three melting areas, the melting peak a1 of the first melting area is 95-115 DEG C, the melting peak a2 of the second melting area is 115-130 DEG C, the melting peak a3 of the third melting area is 140-165 DEG C, and the temperature T3 of the melting peak a3 of the third melting area and the temperature T1 of the melting peak a1 of the first melting area meet the following relational expression: b = T3-T1, the unit of b is DEG C, and the unit of T1 is 0 DEG C; wherein b ranges from 25 DEG C to 70 DEG C. According to the insulation paste disclosed by the invention, the adhesion between the layers is relatively good, the insulation paste cannot be layered under the soaking of electrolyte, and meanwhile, the insulation paste has the performance of high-temperature opening when a battery cell is subjected to thermal runaway; comprising the insulation paste has high safety performance, the sealing performance of a sealing shell is good, and liquid leakage of the sealing shell caused by layering of the insulation paste is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to an insulating adhesive and a battery including the insulating adhesive. Background Art

[0002] Lithium-ion batteries have been widely used in consumer electronic products, electric vehicles, power tools and other products due to their advantages such as high energy density, high voltage, and long cycle life. In recent years, with the continuous improvement of the fast charging and high-rate discharge requirements of battery cells, the electrical performance of battery cells and the safety requirements during use have also been further improved; when the battery cell is fast charged, the current density at the tab is the highest. During the high-rate discharge process, the temperature of the battery cell will rise sharply. At this time, the separator shrinks thermally, causing short circuit between the positive and negative electrodes and decomposition of the SEI film, and the internal temperature of the battery cell rises sharply, resulting in the battery cell catching fire and exploding; therefore, preventing the thermal runaway of the battery cell and improving the safety performance of lithium-ion batteries are crucial. Summary of the Invention

[0003] A battery is composed of a positive electrode assembly, a negative electrode assembly, a separator, a packaging film, and an electrolyte. Among them, since the battery cell housing needs to be electrically connected to the outside, the tab adhesive is heat-sealed with an aluminum-plastic film (packaging film) to form a sealed shell, thereby blocking moisture and air and ensuring the sealing performance of the battery cell. However, under the long-term immersion of the electrolyte, the interfacial bonding force of the tab adhesive layer decreases and delamination occurs, causing the sealed shell to have a leak at the sealing edge, and water vapor inside the battery cell enters, thereby reducing the safety performance of the battery. To solve the above technical problems existing in the prior art, the present invention provides an insulating adhesive and a battery including the insulating adhesive. The bonding between the layers of the insulating adhesive of the present invention is good, and delamination will not occur under the immersion of the electrolyte. At the same time, it can have the performance of high-temperature opening when the battery cell undergoes thermal runaway; the battery including the insulating adhesive has high safety performance while having good sealing performance of the sealed shell, and there will be no leakage of the sealed shell caused by delamination of the insulating adhesive.

[0004] To achieve the above object, in a first aspect of the present invention, there is provided an insulating adhesive, wherein the insulating adhesive includes at least three melting regions. Among them, the melting peak a1 of the first melting region is 95°C - 115°C, the melting peak a2 of the second melting region is 115°C - 130°C, and the melting peak a3 of the third melting region is 140°C - 165°C. The temperature T3 of the melting peak a3 of the third melting region and the temperature T1 of the melting peak a1 of the first melting region satisfy the following relationship: b = T3 - T1, where the unit of b is °C, and b is 25°C - 70°C.

[0005] In an example, b is 40°C - 60°C;

[0006] And / or, the insulating adhesive at least includes a first adhesive layer and a second adhesive layer. The second adhesive layer is located on the surface of one side of the first adhesive layer. The melting point of the first adhesive layer is 95°C - 130°C, and the melting point of the second adhesive layer is 140°C - 170°C.

[0007] In one example, the insulating adhesive includes a third adhesive layer. The third adhesive layer is located on the surface of the second adhesive layer away from the first adhesive layer. The insulating adhesive satisfies: the melting point of the second adhesive layer > the melting point of the third adhesive layer, and / or, the melting point of the second adhesive layer > the melting point of the first adhesive layer;

[0008] And / or, the melting point of the third adhesive layer is 95°C - 130°C;

[0009] And / or, the temperature difference between the melting point of the third adhesive layer and the melting point of the first adhesive layer is -5°C to 25°C.

[0010] In one example, the melting point of the first adhesive layer includes the melting peak a1 of the first melting region and the melting peak a2 of the second melting region;

[0011] And / or, the melting point of the second adhesive layer includes the melting peak a3 of the third melting region;

[0012] And / or, the melting point of the third adhesive layer includes the melting peak a1 of the first melting region and the melting peak a2 of the second melting region.

[0013] The second aspect of the present invention provides a battery, and this battery includes the insulating adhesive described in the first aspect.

[0014] In one example, the battery includes a pole piece assembly and a separator. The pole piece assembly includes a pole piece and a pole piece conductive material. The pole piece includes a current collector and an active material layer located on one or both surfaces of the current collector. The pole piece conductive material is located at one end of the current collector. The first end of the conductive material is a welding end, and the welding end is welded to the current collector. The second end opposite to the first end is a protruding end. A glue application area is formed between the welding end and the protruding end. The insulating adhesive is provided on the glue application area. The insulating adhesive covers the surface of the conductive material. The surface of the first adhesive layer away from the second adhesive layer in the insulating adhesive is adjacent to the conductive material. In the insulating adhesive, the difference b between the temperature T3 of the melting peak a3 of the third melting region and the temperature T1 of the melting peak a1 of the first melting region, in °C, and the adhesion force c between the separator and the pole piece, in N / m, then the battery satisfies the following relational expression: 1.7 ≤ b / c ≤ 50, preferably 3.5 ≤ b / c ≤ 30;

[0015] And / or, b is 25°C - 70°C, preferably 40°C - 60°C;

[0016] And / or, 0.5 N / m ≤ c ≤ 15 N / m, preferably 2 N / m ≤ c ≤ 12 N / m.

[0017] In one example, the separator includes a carrier layer and a polymer layer located on one or both surfaces of the carrier layer. The polymer layer includes polymer clusters. Based on the total area of the carrier layer, the sum of the areas covered by the polymer clusters is 5% - 50% of the carrier layer;

[0018] And / or, the polymer clusters are arranged in a regular or irregular dispersion, forming channels with voids between the polymer clusters. Preferably, the polymer clusters are arranged in a dot matrix;

[0019] And / or, the distance a between the polymer clusters is 50 μm ≤ a ≤ 5000 μm.

[0020] In one example, the battery includes a packaging film. The packaging film is connected to the insulating adhesive to form a sealed shell. The electrode assembly and the separator are located in the enclosed space formed by the sealed shell. The packaging film includes an inner film layer connected to the second or third adhesive layer in the insulating adhesive, a metal layer located on the surface of the inner film layer, and an outer film layer located on the surface of the metal layer. The inner film layer includes a first film layer directly connected to the second or third adhesive layer in the insulating adhesive and a second film layer located on the surface of the first film layer. The melting point of the first film layer is 120°C - 165°C, preferably 130°C - 145°C;

[0021] And / or, the difference between the melting point of the first film layer and the melting point of the second or third adhesive layer is -5°C to 40°C;

[0022] And / or, the first film layer includes modified polypropylene and / or propylene-ethylene copolymer;

[0023] And / or, the modified polypropylene includes one or more of maleic anhydride-modified polypropylene, metallocene modification, ethylene-propylene copolymer, and silane coupling-modified polypropylene.

[0024] In one example, the heat-sealing tensile force between the packaging film and the insulating adhesive is Y ± 0.5, with the unit of N / mm, and the temperature of the battery is T, with the unit of °C. Then the battery satisfies the following relationship: Y = -0.04572 × T + 5.779, where T is 20°C - 125°C.

[0025] Through the above technical solutions, the present invention has at least the following advantages compared with the prior art:

[0026] The insulating glue of the present invention includes at least three melting regions, and the melting peaks of the three melting regions are defined within a specific range. At the same time, by defining the relationship between the melting peak (the lowest temperature region) of the first melting region and the melting peak (the highest temperature region) of the third melting region, the adhesion between the layers in the insulating glue is improved, and at the same time, it has the performance of high-temperature opening. Thus, it can ensure that the battery does not leak liquid when thermal runaway does not occur, and when thermal runaway occurs, the melting of the insulating glue can provide a heat dissipation channel for the battery, improving the safety performance of the battery.

[0027] Other features and advantages of the present invention will be described in detail in the following specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The DSC diagram of the insulating glue of Example 1 in the present invention is shown.

[0029] Figure 2 The structural schematic diagram of the insulating glue including two glue layers in the present invention is shown.

[0030] Figure 3 The structural schematic diagram of the insulating glue including three glue layers in the present invention is shown.

[0031] Figure 4 The structural schematic diagram of the electrode assembly in the present invention is shown.

[0032] Figure 5 The schematic diagram showing the polymer clusters in the separator of the present invention arranged in a dot matrix is shown. DETAILED DESCRIPTION OF THE INVENTION

[0033] The following provides a detailed description of the specific implementation of the present invention. It should be understood that the specific implementation described herein is only used to illustrate and explain the present invention, and is not used to limit the present invention. In this article, without special description, the data range includes both endpoints.

[0034] In the first aspect of the present invention, an insulating glue is provided, wherein the insulating glue includes at least three melting regions. Among them, the melting peak a1 of the first melting region is 95°C - 115°C, the melting peak a2 of the second melting region is 115°C - 130°C, and the melting peak a3 of the third melting region is 140°C - 165°C. The temperature T3 of the melting peak a3 of the third melting region and the temperature T1 of the melting peak a1 of the first melting region satisfy the following relational formula: b = T3 - T1, where the unit of b is °C, and b is 25°C - 70°C.

[0035] Figure 1 For the DSC diagram of the insulating glue of the present invention, it can be seen from Figure 1 that the insulating glue includes at least three melting regions.

[0036] The inventors of the present invention have found through research that the tab glue in the prior art is prone to delamination under the immersion of the electrolyte, resulting in liquid leakage from the sealing edge opening of the sealing shell. This is because there are two melting regions in the tab glue of the prior art, and the temperature difference between the melting peaks of these two melting regions is relatively large, so that the adhesion between the glue layers in the tab glue is low, and delamination is prone to occur under the immersion of the electrolyte.

[0037] In order to improve the adhesion between the layers of the insulating glue and at the same time endow the insulating glue with the performance of high-temperature opening, the insulating glue of the present invention includes at least three melting regions, and the melting peaks of the three melting regions are limited within a specific range. The melting peak a1 of the first melting region is 95°C - 115°C (for example, 95°C, 100°C, 105°C, 110°C, 115°C), the melting peak a2 of the second melting region is 115°C - 130°C (for example, 115°C, 118°C, 120°C, 122°C, 125°C, 128°C, 130°C), and the melting peak a3 of the third melting region is 140°C - 165°C (for example, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C). The temperature T3 of the melting peak a3 of the third melting region and the temperature T1 of the melting peak a1 of the first melting region satisfy the following relationship: b = T3 - T1, where the unit of b is °C, and b is 25°C - 70°C (for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C). In the present invention, the melting peak represents the melting endothermic peak.

[0038] The insulating adhesive of the present invention includes at least three melting regions. When the melting peaks of the three melting regions of the insulating adhesive are defined within the above specific ranges, it can be seen from the temperatures of the melting peaks of the three melting regions that there is a second melting region between the first melting region and the third melting region with a large temperature difference. The temperature difference between the melting peak a2 of the second melting region and the melting peak a1 of the first melting region is small, and the temperature difference between the melting peak a2 of the second melting region and the melting peak a3 of the third melting region is also small. Through the transition of the second melting region, the first melting region with a lower temperature can be connected to the third melting region with a higher temperature, thereby improving the bonding performance between the layers in the insulating adhesive layer and preventing the insulating adhesive from delaminating under the immersion of the electrolyte. At the same time, when the melting peak a1 of the first melting region is defined within the above specific range, the Vicat transition point of the first melting region is low and the heat distortion temperature is low. Compared with the conventional tab adhesive, the first melting region is more likely to undergo heat distortion at the same ambient temperature, so as to ensure that when the battery undergoes thermal runaway (at this time, the temperature of the battery reaches 100 - 120 °C), the insulating adhesive can melt to form a heat dissipation channel, improving the safety performance of the battery. At the same time, when the difference b between the temperature T3 of the melting peak a3 of the third melting region and the temperature T1 of the melting peak a1 of the first melting region is defined within a specific range, the crystallization peaks between the molecules in the adhesive layer of the insulating adhesive can be closer, the crosslinking degree between the molecules increases, and the crystallinity between the materials of the adhesive layer increases, thereby improving the fitting performance between the adhesive layers, making the adhesive layers bond more tightly, avoiding delamination during the electrolyte immersion process, preventing the water vapor passing rate from being too high, and further avoiding the problem of battery swelling and leakage. At the same time, it can also prevent the excessive melting of the insulating adhesive, thereby avoiding the distance between the metal layer in the battery packaging film and the conductive material in the battery from being too close, causing a short circuit.

[0039] In the present invention, by defining the melting regions of the insulating adhesive, as well as the melting peaks and the temperature differences between the melting peaks of the melting regions, the insulating adhesive can already achieve higher bonding performance and high-temperature opening performance than the prior art. To further improve the effect, one or more of the technical features can be further optimized.

[0040] In one example, b is 40 °C - 60 °C. Defining b within the above specific range can further improve the bonding performance of the insulating adhesive and further improve the safety performance of the battery.

[0041] In one example, the insulating adhesive includes at least a first adhesive layer and a second adhesive layer. The second adhesive layer is located on the surface of one side of the first adhesive layer. The melting point of the first adhesive layer is 95 °C - 130 °C (for example, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C). In the present invention, the melting point refers to the temperature corresponding to the peak value of the melting endothermic peak during the heating process.

[0042] In one example, the melting point of the first adhesive layer is 100°C - 110°C.

[0043] In one example, the melting point of the second adhesive layer is 140°C - 170°C (for example, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C). When the melting point of the second adhesive layer is limited within the above specific range, the second adhesive layer can be prevented from excessive melting during the heating of the head, which may cause short circuit due to the contact between the conductive material and the metal layer of the packaging film.

[0044] In one example, the melting point of the second adhesive layer is 155°C - 165°C.

[0045] As Figure 2 shown, the insulating adhesive 4 includes two adhesive layers, a first adhesive layer 41 and a second adhesive layer 42, and the second adhesive layer 42 is located on the surface of one side of the first adhesive layer 41.

[0046] In one example, the melting point of the first adhesive layer includes the melting peak a1 of the first melting region and the melting peak a2 of the second melting region.

[0047] In one example, the melting point of the second adhesive layer includes the melting peak a3 of the third melting region.

[0048] When the insulating adhesive includes two adhesive layers, the insulating adhesive includes three melting regions. The first adhesive layer includes the first melting region and the second melting region, and the second adhesive layer includes the third melting region. At this time, since the first adhesive layer includes the second melting region, the temperature difference between the melting peaks between the first adhesive layer and the second adhesive layer is small. Therefore, for the insulating adhesive including two adhesive layers, the adhesiveness between the adhesive layers is high, and the insulating adhesive will not delaminate under the immersion of the electrolyte.

[0049] The width of the first adhesive layer and the width of the second adhesive layer may be the same or different. In the present invention, as Figure 4 shown, the direction a of the width of the adhesive layer is perpendicular to the direction around which the adhesive layer is wound.

[0050] In one example, the width of the second adhesive layer is smaller than the width of the first adhesive layer.

[0051] In one example, the insulating adhesive includes a third adhesive layer, and the third adhesive layer is located on the surface of the second adhesive layer away from the first adhesive layer. The insulating adhesive satisfies: the melting point of the second adhesive layer > the melting point of the third adhesive layer, and / or, the melting point of the second adhesive layer > the melting point of the first adhesive layer.

[0052] In one example, the insulating adhesive satisfies: the melting point of the second adhesive layer > the melting point of the third adhesive layer, and the melting point of the second adhesive layer > the melting point of the first adhesive layer. When the melting points of the first adhesive layer, the second adhesive layer, and the third adhesive layer in the insulating adhesive satisfy the above specific relationship, compared with the conventional tab adhesive, the first adhesive layer and the third adhesive layer have a lower heat distortion temperature (lower melting point). At the same temperature, the first adhesive layer and the third adhesive layer are more likely to undergo heat distortion. After the third adhesive layer and the inner layer of the packaging film adjacent to the third adhesive layer are melted and then cooled and recrystallized, it can improve the intermolecular crosslinking and enhance the bonding force between the insulating adhesive and the inner layer of the packaging film, thereby avoiding the occurrence of edge opening and liquid leakage during cell dropping and high-frequency vibration. At the same time, the high-temperature layer of the second adhesive layer (with a higher melting point) can prevent excessive melting and avoid the distance between the metal layer of the packaging film and the conductive material being too close, causing a short circuit. When the cell reaches a high temperature of 100 - 120 °C (at this time, the cell undergoes thermal runaway), the first adhesive layer and the conductive material, and the third adhesive layer and the inner layer of the packaging film first melt, and the heat sealing tension suddenly decreases, so that the packaging film at the conductive material and the insulating adhesive covering the surface of the conductive material melt and open to form a heat dissipation channel, improving the safety performance of the battery. That is, when the cell does not undergo thermal runaway, the insulating adhesive is tightly combined with the packaging film and between the insulating adhesive and the conductive material, providing a sealed space for the cell. When the cell undergoes thermal runaway, the first adhesive layer and the third adhesive layer of the insulating adhesive first melt, and the bonding force between the insulating adhesive, the packaging film, and the conductive material at the conductive material is greatly reduced, so that the thermal impulse formed inside the cell due to thermal runaway can open an opening at the sealed position of the conductive material, providing a heat dissipation channel for the cell, thereby preventing the cell from thermal runaway and improving the safety performance of the battery.

[0053] According to a specific embodiment, the melting point of the third adhesive layer is 95 °C - 130 °C (for example, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C). Limiting the melting point of the third adhesive layer within the above specific range can improve the metalophilic property of the third adhesive layer, thereby enhancing the bonding performance between the third adhesive layer and the inner layer film of the packaging film.

[0054] In one example, the melting point of the third adhesive layer is 100 °C - 125 °C.

[0055] In one example, the difference h between the melting point of the third adhesive layer and the melting point temperature of the first adhesive layer is -5°C to 25°C (for example, -5°C, -3°C, 0°C, 3°C, 5°C, 10°C, 15°C, 20°C, 25°C). When the difference between the melting point of the third adhesive layer and the melting point temperature of the first adhesive layer is limited within the above specific range, the heat-induced deformation of the first adhesive layer and the third adhesive layer is basically synchronous. At the same temperature, the packaging film is more likely to undergo melting and cooling crystallization with the third adhesive layer, and their bonding strength is stronger, improving the normal-temperature sealing performance of the battery cell. At the same time, when the battery cell experiences thermal runaway at high temperature, the interface between the first adhesive layer and the conductive material and the fusion interface between the third adhesive layer and the packaging film can melt first, causing the tensile force of the overall sealing interface between the packaging film and the conductive material to decay, making the interface easier to open and providing a heat dissipation channel to prevent the battery from catching fire and burning.

[0056] It can be understood that the melting point of the third adhesive layer can be higher than the melting point temperature of the first adhesive layer, or the melting point of the third adhesive layer can be lower than the melting point temperature of the first adhesive layer. When the difference between the melting point of the third adhesive layer and the melting point temperature of the first adhesive layer is negative, it means that the melting point of the third adhesive layer is lower than the melting point temperature of the first adhesive layer; when the difference between the melting point of the third adhesive layer and the melting point temperature of the first adhesive layer is positive, it means that the melting point of the third adhesive layer is higher than the melting point temperature of the first adhesive layer.

[0057] In one example, the melting point of the third adhesive layer includes the melting peak a1 of the first melting region and the melting peak a2 of the second melting region.

[0058] As Figure 3 shown, the insulating adhesive 4 includes three adhesive layers, and the third adhesive layer 43 is located on the surface of the second adhesive layer 42 away from the first adhesive layer 41.

[0059] When the insulating adhesive includes three adhesive layers, the insulating adhesive includes three melting regions. The first adhesive layer includes the first melting region and the second melting region, the second adhesive layer includes the third melting region, and the third adhesive layer includes the first melting region and the second melting region. At this time, both the first adhesive layer and the third adhesive layer include the second melting region, and the temperature difference between the melting peaks among the first adhesive layer, the third adhesive layer, and the second adhesive layer is small. Therefore, for the insulating adhesive including three adhesive layers, the adhesiveness between the adhesive layers is relatively high, and the insulating adhesive will not delaminate under the immersion of the electrolyte.

[0060] In one example, the first adhesive layer includes a first modified resin.

[0061] In one example, the first modified resin includes one or more of maleic anhydride-modified polypropylene, acrylic acid-modified polypropylene, metallocene-modified polypropylene, propylene-ethylene copolymer, and propylene-butene copolymer.

[0062] In one example, the first modified resin includes a first modified resin A1 and a first modified resin A2. Among them, the melting point d1 of the first modified resin A1 is 95°C ≤ d1 ≤ 115°C, and the melting point d2 of the first modified resin A2 is 115°C < d2 ≤ 130°C. Based on the total weight of the first adhesive layer, the weight content of the first modified resin A1 is ≥ 50 wt% (for example, 50 wt%, 50.5 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 100 wt%), and the weight content of the first modified resin A2 is ≤ 50 wt% (for example, 0 wt%, 0.5 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 49.5 wt%, 50 wt%). When the weight content of the first modified resin A1 in the first adhesive layer is 100 wt%, it means that the first adhesive layer is the first modified resin A1. When the weight content of the first modified resin A2 in the first adhesive layer is 0 wt%, it means that the first modified resin A2 does not exist in the first adhesive layer.

[0063] From the melting points of the first modified resin A1 and the first modified resin A2, it can be seen that the melting point of the first adhesive layer includes the melting peak a1 of the first melting region and the melting peak a2 of the second melting region.

[0064] In one example, the third adhesive layer includes a second modified resin.

[0065] In one example, the second modified resin is selected from one or more of maleic anhydride modified polypropylene, acrylic acid modified polypropylene, metallocene modified polypropylene, propylene-ethylene copolymer, and butene-propylene copolymer.

[0066] In one example, the third adhesive layer includes a second modified resin, and the third adhesive layer includes a second modified resin C1 and a second modified resin C2. Among them, the melting point f1 of the second modified resin C1 is 95°C ≤ f1 ≤ 115°C, and the melting point f2 of the second modified resin C2 is 115°C < f2 ≤ 130°C. Then, based on the total weight of the third adhesive layer, the weight content of the second modified resin C1 ≥ 50 wt% (for example, 50 wt%, 50.5 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 100 wt%), and the weight content of the second modified resin C2 ≤ 50 wt% (for example, 0 wt%, 0.5 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 49.5 wt%, 50 wt%). When the weight content of the second modified resin C1 in the third adhesive layer is 100 wt%, it means that the third adhesive layer is the second modified resin C1. When the weight content of the second modified resin C2 in the third adhesive layer is 0 wt%, it means that the second modified resin C2 does not exist in the third adhesive layer.

[0067] From the melting points of the second modified resin C1 and the second modified resin C2, it can be seen that the melting point of the third adhesive layer includes the melting peak a1 of the first melting region and the melting peak a2 of the second melting region.

[0068] The widths of the first adhesive layer, the second adhesive layer, and the third adhesive layer can be the same or different from each other.

[0069] In one example, the width of the second adhesive layer < the width of the first adhesive layer, and / or the width of the second adhesive layer < the width of the first adhesive layer.

[0070] In one example, the second adhesive layer includes one or more of polypropylene, block polypropylene, and copolymerized polypropylene; among them, the block polypropylene includes alternating propylene-ethylene segments and / or alternating butene-propylene segments, and the copolymerized polypropylene includes ethylene-propylene copolymerization and / or butene-propylene copolymerization.

[0071] The second aspect of the present invention provides a battery, and this battery includes the insulating adhesive described in the first aspect.

[0072] In one example, the battery includes a pole piece assembly and a separator. The pole piece assembly includes a pole piece and a pole piece conductive material. The pole piece includes a current collector and an active material layer located on one or both surfaces of the current collector. The pole piece conductive material is located at one end of the current collector. The first end of the conductive material is a welding end, and the welding end is connected to the current collector by welding. The second end opposite to the first end is a protruding end. A glue application area is formed between the welding end and the protruding end. An insulating glue is provided on the glue application area. The insulating glue covers the surface of the conductive material. The surface of the first glue layer of the insulating glue away from the second glue layer is adjacent to the conductive material. In the insulating glue, the difference b between the temperature T3 of the melting peak a3 of the third melting region and the temperature T1 of the melting peak a1 of the first melting region, in °C, and the adhesion force c between the separator and the pole piece, in N / m, then the battery satisfies the following relationship: 1.7 ≤ b / c ≤ 50 (for example, 1.7, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50).

[0073] Wherein, the adhesion force c between the separator and the pole piece can be the adhesion force between the separator and the positive pole piece or the adhesion force between the separator and the negative pole piece. The value of c is the smaller one of the adhesion force between the separator and the positive pole piece and the adhesion force between the separator and the negative pole piece. When the smaller c value of the two satisfies the above specific relationship, a higher degree of matching between the melting temperature of the insulating glue and the thermal runaway temperature of the battery cell can be ensured.

[0074] Defining the adhesion force between the separator and the pole piece and the difference between the temperature of the melting peak of the third melting region and the temperature of the melting peak of the first melting region to satisfy the above specific relationship can enable a higher degree of matching between the melting temperature of the insulating glue and the thermal runaway temperature of the battery cell. That is, when the battery cell does not undergo thermal runaway, the insulating glue is tightly combined with the packaging film and between the insulating glue and the conductive material, providing a sealed space for the battery cell. When the battery cell undergoes thermal runaway, the first glue layer of the insulating glue first melts, and the bonding force between the insulating glue and the conductive material is greatly reduced, so that the thermal impact force formed inside the battery cell due to thermal runaway can break through and form an opening at the pole ear sealing position, providing a heat dissipation channel for the battery cell, thereby preventing the thermal runaway of the battery cell and improving the safety performance of the battery.

[0075] In one example, the battery satisfies the following relationship: 3.5 ≤ b / c ≤ 30.

[0076] Such as Figure 4As shown, the electrode assembly includes an electrode and an electrode conductive material. The electrode includes a current collector 1 and an active material layer 2 located on one or both surfaces of the current collector 1. The electrode conductive material 3 is located at one end of the current collector 1. The first end of the conductive material 3 is a welding end 311, and the welding end 311 is welded to the current collector 1. The second end opposite to the first end is a protruding end 312. A gluing area is formed between the welding end and the protruding end. An insulating glue 4 is provided on the gluing area. The insulating glue 4 covers the surface of the conductive material 3. The surface of the first glue layer 41 of the insulating glue 4 away from the second glue layer 42 is adjacent to the conductive material 3.

[0077] In one example, the electrode includes a positive electrode and / or a negative electrode.

[0078] In one example, the positive electrode includes a positive current collector and a positive active material layer located on one or both surfaces of the positive current collector.

[0079] In one example, the positive current collector includes aluminum or an aluminum alloy.

[0080] In one example, the negative electrode includes a negative current collector and a negative active material layer located on one or both surfaces of the negative current collector.

[0081] In one example, the negative current collector includes nickel, nickel-plated copper, a nickel alloy, or a copper alloy.

[0082] In one example, the battery includes a packaging film. The packaging film is connected to the insulating glue to form a sealed shell. The electrode assembly and the separator are located in the enclosed space formed by the sealed shell. The packaging film includes an inner film layer connected to the second glue layer or the third glue layer of the insulating glue, a metal layer located on the surface of the inner film layer, and an outer film layer located on the surface of the metal layer. The inner film layer includes a first film layer directly connected to the second glue layer or the third glue layer of the insulating glue and a second film layer located on the surface of the first film layer.

[0083] In one example, the inner film layer includes one or more of polypropylene, ethylene-propylene copolymer, maleic anhydride-modified polypropylene, and butene-propylene copolymer.

[0084] In one example, the metal layer includes aluminum, copper, or stainless steel.

[0085] In one example, the outer film layer is a protective layer. The outer film layer includes one or more of polyamide (PA), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN).

[0086] In one example, the melting point of the first film layer is 120°C - 165°C (for example, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C).

[0087] In one example, the melting point of the first film layer is 130°C - 145°C.

[0088] In one example, the difference between the melting point of the first film layer and the melting point of the third adhesive layer is -5°C to 40°C (for example, -5°C, -3°C, 0°C, 3°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C). When the difference between the melting point of the first film layer and the melting point of the third adhesive layer meets the limitations of the above specific range, at the same heat sealing temperature, the melting points of the first film layer and the third adhesive layer are low and relatively close. After hot melting and recrystallization, the intermolecular crosslinking increases, the bonding force between the two increases, the safety performance of the battery cell is improved, and leakage caused by the opening of the sealing edge during the drop or high-frequency vibration of the battery cell is avoided.

[0089] It can be understood that the melting point of the first film layer can be higher than the melting point temperature of the third adhesive layer, or the melting point of the first film layer can be lower than the melting point temperature of the third adhesive layer. When the difference between the melting point of the first film layer and the melting point temperature of the third adhesive layer is negative, it means that the melting point of the first film layer is lower than the melting point temperature of the third adhesive layer; when the difference between the melting point of the first film layer and the melting point temperature of the third adhesive layer is positive, it means that the melting point of the first film layer is higher than the melting point temperature of the third adhesive layer.

[0090] In one example, the insulating adhesive satisfies: the melting point of the second adhesive layer > the melting point of the third adhesive layer, and the melting point of the second adhesive layer > the melting point of the first adhesive layer, and the difference between the melting point of the third adhesive layer and the melting point temperature of the first adhesive layer is -5°C to 25°C, and the difference between the melting point of the first film layer and the melting point of the third adhesive layer is -5°C to 40°C.

[0091] In one example, the first film layer includes modified polypropylene and / or propylene-ethylene copolymer.

[0092] In one example, the modified polypropylene includes one or more of maleic anhydride modified polypropylene, metallocene modification, ethylene-propylene copolymer, and silane coupling modified polypropylene.

[0093] In one example, the heat-sealing tensile force between the packaging film and the insulating adhesive is Y ± 0.5, with the unit of N / mm, and the temperature of the battery is T, with the unit of °C. Then the battery satisfies the following relationship: Y = -0.04572 × T + 5.779, where T ranges from 20°C to 125°C (for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 125°C). As can be seen from the above relationship, the heat-sealing tensile force Y between the packaging film and the insulating adhesive decreases as the temperature increases. Thus, when the battery core undergoes thermal runaway, the heat-sealing tensile force between the packaging film and the insulating adhesive is already very small (for example, when the temperature T of the battery is 110°C, Y = -0.04572 × 110 + 5.779 = 0.7498 N / mm, and at this time the heat-sealing tensile force is 0.7498 ± 0.5). At this time, the thermal force generated inside the battery core is sufficient to break the connection between the packaging film and the insulating adhesive, thereby providing a channel for the diffusion of heat and further enhancing the safety performance of the battery.

[0094] The heat-sealing tensile force between the packaging film and the insulating adhesive can be Y ± 0.5, with the unit of N / mm. Since there are differences in the measured values according to the sampling positions when testing the heat-sealing tensile force between the packaging film and the insulating adhesive, in order to be consistent with the actual situation, a tolerance of ±0.5 is added to the basis of Y.

[0095] In one example, c ranges from 0.5 N / m to 15 N / m, for example, 0.5 N / m, 1 N / m, 2 N / m, 3 N / m, 4 N / m, 5 N / m, 6 N / m, 7 N / m, 8 N / m, 9 N / m, 10 N / m, 11 N / m, 12 N / m, 13 N / m, 14 N / m, 15 N / m).

[0096] In one example, c ranges from 2 N / m to 12 N / m.

[0097] In one example, the separator includes a carrier layer and polymer layers located on one or both surfaces of the carrier layer, and the polymer layers include polymer clusters.

[0098] In one example, the polymer clusters are arranged in a regular or irregular dispersion, forming channels with voids between the polymer clusters. The channels with voids formed between the polymer clusters can provide a channel for the transfer of ions.

[0099] In one example, the polymer clusters are arranged in a lattice pattern. As Figure 4 shown, when the polymer clusters are arranged in a lattice pattern, the transfer rate of ions can be further increased.

[0100] In one example, the distance a between the polymer clusters is 50 μm ≤ a ≤ 5000 μm (for example, 50 μm, 100 μm, 300 μm, 500 μm, 700 μm, 1000 μm, 1500 μm, 2000 μm, 2500 μm, 3000 μm, 3500 μm, 4000 μm, 4500 μm, 5000 μm). When the distance a between the polymer clusters is defined within the above specific range, heat dissipation channels in different directions can be formed when the positive electrode sheet, the separator, and the negative electrode sheet are in close contact, providing heat dissipation channels when heat accumulates inside the battery cell.

[0101] In one example, based on the total area of the carrier layer, the area covered by the polymer clusters on the carrier layer is 5% - 50% (for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%). When the area covered by the polymer clusters on the carrier layer is defined within the above specific range, the positive and negative electrode sheets and the separator can be in close contact. The separator serves as a transmission channel for lithium ions inside the battery cell. When the positive electrode sheet, the separator, and the negative electrode sheet are in close contact, rapid conduction of lithium ions can be achieved, reducing the impedance of the battery cell and improving the cycle performance of the battery cell.

[0102] In one example, based on the total area of the carrier layer, the area covered by the polymer clusters on the carrier layer is 8% - 20%.

[0103] In one example, the polymer clusters are secondary particles formed by polymer polymerization, and the polymer includes one or more of acrylic acid, acrylate, methacrylic acid, methacrylate, vinylidene fluoride, acrylonitrile, styrene, vinyl chloride, perfluoropropylene, chlorotrifluoroethylene, tetrafluoroethylene, vinylidene chloride, and tetrachloroethylene.

[0104] In one example, the carrier layer includes a substrate layer and a heat-resistant layer located on one or both sides of the substrate layer.

[0105] In one example, the substrate layer includes one or more of polyethylene, polypropylene, polyethylene and polypropylene composites, polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and aramid.

[0106] In one example, the heat-resistant layer includes one or more of alumina, boehmite, magnesia, boron nitride, and magnesium hydroxide.

[0107] It should be noted that in the present invention, the numerical representation methods such as "first", "second", "third", etc. are only used to distinguish different substances or usage methods, and do not represent the difference in order.

[0108] The present invention will be described in detail below through embodiments. The embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts belong to the scope of protection of the present invention.

[0109] Example Group I is used to illustrate the insulating adhesive of the present invention.

[0110] Example 1-1

[0111] Composition of the first adhesive layer: 80 parts by weight of the first modified resin A1 (maleic anhydride modified polypropylene, melting point d1 is 105.4 °C), 20 parts by weight of the first modified resin A2 (propylene copolymer, melting point d2 is 120.8 °C);

[0112] Composition of the second adhesive layer: 100 parts by weight of copolymerized polypropylene (melting point is 161.5 °C).

[0113] The structure of the insulating adhesive is a two-layer structure. The melting point of the first adhesive layer is 105.4 °C & 120.8 °C (that is, the first adhesive layer includes a first melting region and a second melting region, where the temperature T1 of the melting peak of the first melting region is 105.4 °C, and the temperature T2 of the melting peak of the second melting region is 120.8 °C);

[0114] The melting point of the second adhesive layer is 161.5 °C (that is, the second adhesive layer includes a third melting region, and the temperature T3 of the melting peak of the third melting region is 161.5 °C).

[0115] Example Group I-2

[0116] This group of examples is used to illustrate the effects produced when b is changed by changing the proportional relationship of the monomers of maleic anhydride modified polypropylene in the first adhesive layer to change T1 and / or by changing the proportional relationship of the monomers of copolymerized polypropylene in the second adhesive layer to change T3.

[0117] This group of examples is carried out with reference to Example I-1. The difference is that the change of b is caused by changing T1 and / or T3. See Table I-1 for details.

[0118] Example Group I-3

[0119] Example I-3a

[0120] Composition of the first adhesive layer: Refer to the first adhesive layer in Example I-1;

[0121] Composition of the second adhesive layer: Refer to the second adhesive layer in Example I-1;

[0122] Composition of the third adhesive layer: 80 parts by weight of the second modified resin C1 (maleic anhydride modified polypropylene, melting point f1 is 105.4 °C), 20 parts by weight of the second modified resin C2 (propylene-ethylene copolymer, melting point f2 is 120.8 °C).

[0123] The structure of the insulating adhesive is a three-layer structure. The first adhesive layer is carried out with reference to the first adhesive layer in Example I-1;

[0124] The second adhesive layer is carried out with reference to the second adhesive layer in Example I-1;

[0125] The melting point of the third adhesive layer is 105.4 °C & 120.8 °C (that is, the third adhesive layer includes a first melting region and a second melting region, where the temperature T1 of the melting peak of the first melting region is 105.4 °C, and the temperature T2 of the melting peak of the second melting region is 120.8 °C). See Table I-1 for details.

[0126] Example I-3b

[0127] Carried out with reference to Example I-3a, the difference is that by changing the proportional relationship of the monomers of maleic anhydride modified polypropylene in the first adhesive layer to change T1 and the proportional relationship of the monomers of propylene-ethylene copolymer to change T2. See Table I-1 for details.

[0128] Example I-3c

[0129] Carried out with reference to Example I-3a, the difference is that the weight content of maleic anhydride modification with a melting point d1 of 105.4 °C in the first adhesive layer is adjusted to 100%, and the weight content of propylene-ethylene copolymer with a melting point f2 of 120.8 °C in the third adhesive layer is adjusted to 100%. See Table I-1 for details.

[0130] Example I-3d

[0131] Carried out with reference to Example I-3b, the difference is that the weight content of maleic anhydride modification with a melting point d1 of 95.2 °C in the first adhesive layer is adjusted to 100%, and the weight content of propylene-ethylene copolymer with a melting point f2 of 130.5 °C in the third adhesive layer is adjusted to 100%. See Table I-1 for details.

[0132] Example I-3e

[0133] Carried out with reference to Example I-3d, the difference is that by changing the proportional relationship of the monomers of maleic anhydride modified polypropylene in the first adhesive layer to change d1, and by changing the proportional relationship of the monomers of maleic anhydride modified polypropylene in the third adhesive layer to change f1. See Table I-1 for details.

[0134] Comparative Example I-1

[0135] It is carried out with reference to Example I-3c, except that the insulating glue does not include the third glue layer. See Table I-1 for details.

[0136] Table I-1a

[0137]

[0138] Table I-1b

[0139]

[0140]

[0141] - indicates non-existence;

[0142] h represents the difference in melting point between the third glue layer and the first glue layer.

[0143] Preparation Example I-1

[0144] (1) Positive electrode sheet assembly

[0145] The positive electrode active material (97.6 parts by weight of lithium cobaltate), the conductive agent (1.35 parts by weight of conductive carbon black), the binder (1.05 parts by weight of PVDF), and the solvent (NMP) are stirred and uniformly mixed, and then coated on both surfaces of the positive electrode current collector (10-μm-thick aluminum foil) to form a positive electrode active material layer; it is dried and rolled to obtain a positive electrode sheet, and the area of the positive electrode sheet where the positive electrode active material layer is not coated can be welded with a positive electrode conductive material.

[0146] The positive electrode conductive material is aluminum. The first end of the positive electrode conductive material is a welding end, which is welded to the positive electrode current collector. The second end opposite to the first end is a protruding end. A glue-applying area is formed between the welding end and the protruding end. An insulating glue is provided on the glue-applying area, and the insulating glue covers the surface of the positive electrode conductive material. The surface of the first glue layer of the insulating glue away from the second glue layer is adjacent to the positive electrode conductive material. The length of the positive electrode conductive material at the welding end of the positive electrode current collector is 30 mm. The insulating glue of Group I of Example I and Comparative Example I-1 is used respectively, and its specifications are 0.1 mm thick, 6 mm wide, and 2.5 mm unilateral glue width.

[0147] (2) Negative electrode sheet assembly: The negative electrode active material (97 parts by weight of graphite), the conductive agent (1.5 parts by weight of conductive carbon black), the binder (1.5 parts by weight of styrene-butadiene rubber), and the solvent (deionized water) are stirred and uniformly mixed, and then coated on both surfaces of the negative electrode base fluid (10-μm-thick copper foil); it is dried and rolled to obtain a negative electrode sheet, and the area of the negative electrode sheet where the negative electrode active material layer is not coated can be welded with a negative electrode conductive material.

[0148] The negative electrode conductive material is nickel-plated copper. The first end of the negative electrode conductive material is the welding end, which is connected to the negative electrode current collector by welding. The second end opposite to the first end is the protruding end. A glue application area is formed between the welding end and the protruding end. An insulating glue is provided on the glue application area, covering the surface of the negative electrode conductive material. The surface of the first glue layer on the side away from the second glue layer in the insulating glue is adjacent to the negative electrode conductive material. The length of the negative electrode conductive material at the welding end of the negative electrode current collector is 30 mm. The insulating glue uses the insulating glues of Example I group and Comparative Example I-1 respectively, with a specification of 0.1 mm thick, 6 mm wide, and 2.5 mm unilateral glue width.

[0149] (3) Separator

[0150] A polyethylene substrate with a thickness of 7 μm.

[0151] (4) Electrolyte

[0152] In a glove box filled with argon (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents are mixed evenly, and then a fully dried lithium salt is quickly added thereto. After dissolution, an additive is added to obtain the required electrolyte. Among them, the lithium salt is 10 parts by weight; the organic solvents (ethylene carbonate (EC) 40 parts by weight, diethyl carbonate (DEC) 40 parts by weight, fluoroethylene carbonate (FEC) 5 parts by weight) are 85 parts by weight, and the additive (PS) is 5 parts by weight.

[0153] (5) Packaging film

[0154] Aluminum-plastic film.

[0155] (6) Preparation of the battery

[0156] After stacking the positive electrode sheet assembly in step (1), the negative electrode sheet assembly in step (2), and the separator in step (3) in the order of the positive electrode sheet assembly, the separator, and the negative electrode sheet assembly, winding is carried out to obtain an electrode core; the electrode core is placed in the packaging film in step (5), and the electrolyte in step (4) is injected into the packaging film. After processes such as vacuum packaging, standing, formation, shaping, and sorting, a lithium-ion battery is obtained.

[0157] Test Example I-1

[0158] 1. Adhesion test between the separator and the electrode sheet assembly

[0159] After removing the battery from the sorting table, place it in an environment of (25±2)°C and let it stand for 2 - 3 hours. Charge the battery at a constant current of 0.7C, with a cut-off current of 0.05C. When the battery terminal voltage reaches the charging limit voltage, switch to constant voltage charging until the charging current ≤ cut-off current, then stop charging and let it stand for 5 minutes. Dissect the fully charged battery, and adopt the national standard GB / T2790-1995, that is, use the 180° peel test standard to test the adhesion between the separator and the positive electrode plate or the negative electrode plate. Cut the separator and the positive electrode plate or the negative electrode plate into small strips of 15mm×54.2mm, and test the adhesion between the separator and the positive electrode plate or the negative electrode plate according to the 180° peel test standard.

[0160] 2. Hot box test

[0161] (1) 130°C hot box test

[0162] Under the environment of 25°C±3°C, discharge at 0.2C to the cut-off voltage of 3.0V and let it stand for 10 minutes; charge at a constant current and constant voltage of 0.5C to the upper limit voltage of 4.2V, with a cut-off current of 0.02C. Test the full charge state voltage, internal resistance, and thickness at 25°C±3°C. Put the fully charged battery cell into the test chamber, and the test chamber heats up at a temperature rise rate of (5±2)°C / min. When the temperature in the chamber reaches 130°C±2°C, keep it constant for 60 minutes; after the test is completed, observe whether the battery cell catches fire. If it catches fire, it fails; if it doesn't catch fire, it passes. Each sample is tested ten times, and the result is expressed as "number of passes / 10", for example, "10 / 10" means all 10 times pass, and "5 / 10" means 5 times pass out of 10 tests.

[0163] (2) 135°C hot box test

[0164] Under the environment of 25°C±3°C, discharge at 0.2C to the cut-off voltage of 3.0V and let it stand for 10 minutes; charge at a constant current and constant voltage of 0.5C to the upper limit voltage of 4.2V, with a cut-off current of 0.02C. Test the full charge state voltage, internal resistance, and thickness at 25°C±3°C. Put the fully charged battery cell into the test chamber, and the test chamber heats up at a temperature rise rate of (5±2)°C / min. When the temperature in the chamber reaches 135°C±2°C, keep it constant for 60 minutes; after the test is completed, observe whether the battery cell catches fire. If it catches fire, it fails; if it doesn't catch fire, it passes. Each sample is tested ten times, and the result is expressed as "number of passes / 10", for example, "10 / 10" means all 10 times pass, and "5 / 10" means 5 times pass out of 10 tests.

[0165] (3) 140°C hot box test

[0166] At 25℃±3℃, discharge at 0.2C to a cut-off voltage of 3.0V, and let stand for 10min; charge at 0.5C constant current and constant voltage to an upper limit voltage of 4.2V, with a cut-off current of 0.02C, and test the voltage, internal resistance, and thickness of the fully charged state at 25℃±3℃. Put the fully charged battery into the test chamber, and heat the chamber at a temperature rise rate of (5±2)℃ / min. When the temperature in the chamber reaches 140℃±2℃, keep the temperature constant for 60min; after the test is completed, observe whether the battery cell catches fire. If it catches fire, it fails, and if it does not catch fire, it passes. Each sample is tested ten times in total, and the results are expressed as "number of passes / 10", for example, "10 / 10" means that all 10 tests passed, and "5 / 10" means that 5 out of 10 tests passed.

[0167] 3. Whole machine drop test

[0168] After the battery is installed, discharge at 0.2C to a cut-off voltage of 3.0V at 25℃±3℃, and let stand for 10min; charge at 0.5C constant current and constant voltage to 50% SOC, and drop the battery on the ear surface of the battery from a height of 1.5m on granite, back and forth 20 times. If the battery opens, it is considered a failure, and if it does not open, it is considered a pass. Each sample is tested ten times in total, and the results are expressed as "number of passes / 10", for example, "10 / 10" means that all 10 tests passed, and "5 / 10" means that 5 out of 10 tests passed.

[0169] 4. Sealing test

[0170] At 25℃±3℃, discharge at 0.2C to the lower voltage limit (3V), let stand for 10min, place the battery in a 25℃ constant temperature box, fully charge at 0.7C constant current (100% SOC), cut-off current 0.02C, after fully charged, store the battery in 60℃&95RH (humidity) environment, test the battery body thickness every 3D, if the expansion rate exceeds 10%, it is considered a failure; if the expansion rate does not exceed 10%, it is considered a pass, and record the pass ratio of the battery within 30D. Each sample is tested ten times in total, and the results are expressed as "pass number / 10", for example, "10 / 10" means that all 10 times passed, and "5 / 10" means that 5 out of 10 tests passed.

[0171] 5. Opening test

[0172] At an environment of 25℃±3℃, discharge at 0.2C until the lower limit voltage of 3V, let it stand for 10 min, place the battery in an incubator at 25℃, charge it fully at a constant current of 0.7C (100% SOC), with a cut-off current of 0.02C. After being fully charged, place the battery in environments of 120℃ and 130℃ respectively, and observe whether the top of the battery opens or whether the electrolyte flows out within 2 min. If it opens or the electrolyte flows out, it is considered passed; if there is no opening or the electrolyte does not flow out, it means it fails. Each sample is tested ten times, and the result is expressed as "number of passes / 10". For example, "10 / 10" means all 10 tests are passed, and "5 / 10" means 5 out of 10 tests are passed.

[0173] The batteries obtained from Example Group I and Comparative Example I-1 were respectively subjected to a sealing test, a whole machine drop test, and a 135℃ hot box test. The results of Example Group I and Comparative Example I-1 are recorded in Table I-2.

[0174] Table I-2

[0175] Sealing test pass situation Integrated machine drop test pass situation 135°C hot box test pass situation Example I-1 8 / 10 5 / 10 8 / 10 Example I-2a 2 / 10 4 / 10 7 / 10 Example I-2b 7 / 10 6 / 10 6 / 10 Example I-2d 4 / 10 4 / 10 6 / 10 Example I-3a 10 / 10 10 / 10 9 / 10 Example I-3b 8 / 10 8 / 10 9 / 10 Example I-3c 3 / 10 6 / 10 6 / 10 Example I-3d 1 / 10 5 / 10 6 / 10 Example I-3e 3 / 10 5 / 10 7 / 10 Comparative example I-1 1 / 10 2 / 10 4 / 10

[0176] It can be seen from Table I-2 that through the comparative examples and examples, it can be seen that for the batteries made of the insulating glue in the examples, the passing situation of the sealing test has been improved, the passing situation of the whole machine drop test has been significantly improved, and the passing situation of the 135℃ hot box test has been significantly improved. This shows that the insulating glue of the present invention, by limiting the melting region of the insulating glue and the difference between the melting peak and the melting peak temperature in the melting region, improves the bonding performance and high-temperature opening performance of the insulating glue.

[0177] Example Group II is used to illustrate the insulating glue and separator of the present invention.

[0178] Example II-1a

[0179] (1) Insulating glue: Use the insulating glue obtained from Example I-3a.

[0180] (2) Positive electrode sheet assembly: Use the positive electrode sheet assembly obtained from Preparation Example I-1.

[0181] (3) Negative electrode sheet assembly: Use the negative electrode sheet assembly obtained from Preparation Example I-1.

[0182] (4) Separator preparation: Add polymethyl methacrylate and an auxiliary adhesive (a copolymer formed by polymerizing styrene, isobutyl acrylate, and acrylonitrile, with a D50 of 0.2μm) to deionized water at a solid content of 8%, and stir at a stirring speed of 1500 rpm for 60 min to obtain a polymer slurry S.

[0183] A layer of alumina layer (composed of 92 wt% alumina, 4 wt% methacrylic acid, and 4 wt% sodium polymethyl cellulose) with a thickness of 2 μm is coated on the first surface of a polyethylene substrate with a thickness of 7 μm by gravure roll coating. On the second surface of the polyethylene substrate opposite to the first surface and the surface of the alumina layer, a polymer layer with a surface density of 0.15 g / m 2 is coated by regular dot matrix. After drying in an oven, the separator as shown in Figure 4 is obtained. Among them, the polymer clusters are arranged in a dot matrix, and the distance a between the polymer clusters is 300 μm.

[0184] The prepared separator is observed by SEM at a magnification of 100 times, the number and area of the polymer clusters are identified, and through area ratio calculation, the coverage ratio of the polymer clusters is obtained as 5%.

[0185] (5) Electrolyte: Use the electrolyte obtained in Preparation Example I-1.

[0186] (6) Packaging film: Use the packaging film obtained in Preparation Example I-1.

[0187] (7) After laminating the positive electrode sheet assembly in step (2), the negative electrode sheet assembly in step (3), and the separator in step (4) in the order of the positive electrode sheet assembly, the separator, and the negative electrode sheet assembly, winding is carried out to obtain an electric core; the electric core is placed in the packaging film in step (6), and the electrolyte in step (5) is injected into the packaging film. After processes such as vacuum packaging, standing, formation, shaping, and sorting, a lithium-ion battery is obtained.

[0188] Examples II-1b to II-1g

[0189] Refer to Example II-1. The difference is that c is changed by adjusting the coverage area of the polymer clusters in the carrier layer. See Table II-1 for details.

[0190] Example II-2

[0191] Refer to Example II-1a. The difference is that the arrangement mode of the polymer is changed. See Table II-1 for details.

[0192] Example Group II-3

[0193] This group of examples is used to illustrate the influence when the specific selection of the polymer changes.

[0194] This group of examples refers to Example II-1a. The difference is that the specific selection of the polymer is changed. See Table II-1 for details.

[0195] Example Group II-4

[0196] This set of embodiments is used to illustrate the effects produced when a changes.

[0197] This set of embodiments is carried out with reference to Embodiment II-1a. The difference is that a is changed. See Table II-1 for details.

[0198] Table II-1

[0199]

[0200]

[0201] The batteries obtained in the Embodiment II group are respectively subjected to an opening test, a whole-machine drop test, and a 135°C hot box test. The results obtained in the Embodiment II group are recorded in Table II-2.

[0202] Table II-2

[0203]

[0204]

[0205] It can be seen from Table II-2 that through the embodiments, it can be seen that for the batteries prepared from the insulating glue and the separator of the present invention, the melting temperature of the insulating glue can achieve a high degree of adaptation to the thermal runaway temperature of the battery. The passing rate of the whole-machine drop test of the battery is relatively high, indicating that the sealing effect of the battery is good. When the battery does not undergo thermal runaway, it can provide a sealed space for the battery. The passing rate of the 135°C hot box test of the battery is relatively high, and the passing rates of the opening tests at 120°C and 130°C are relatively high, indicating that when the battery undergoes thermal runaway, it can open in time to provide heat dissipation for the battery, improving the safety performance of the battery.

[0206] The Embodiment III group is used to illustrate the insulating glue and the packaging film of the present invention.

[0207] Embodiment III-1

[0208] It is carried out with reference to Embodiment I-1. The difference is that the melting point of the first film layer in the selected packaging film is 140.8°C. See Table III-1 for details.

[0209] Embodiment III-2

[0210] It is carried out with reference to Embodiment I-1. The difference is that the melting point of the first film layer in the selected packaging film is 120.3°C. See Table III-1 for details.

[0211] Embodiment III-3

[0212] It is carried out with reference to Embodiment I-1. The difference is that the melting point of the first film layer in the selected packaging film is 165.6°C. See Table III-1 for details.

[0213] The batteries obtained from the third group of Examples were respectively subjected to a sealing test, a whole machine drop test, a 130°C hot box test, and a 140°C hot box test. The results obtained from the third group of Examples were recorded in Table III-1.

[0214] Table III-1

[0215]

[0216] It can be seen from Table III-1 and through the Examples that the passing rate of the sealing test of the batteries made of the insulating glue and packaging film in the Examples is relatively high, and the passing rate of the whole machine drop test is relatively high, indicating that the sealing effect of the batteries is good. When the battery does not undergo thermal runaway, it can provide a sealed space for the battery; the passing rate of the 130°C and 140°C hot box tests is relatively high, indicating that when the battery undergoes thermal runaway, it can open in time to provide heat dissipation for the battery and improve the safety performance of the battery.

[0217] The fourth group of Examples is used to illustrate the insulating glue, separator, and packaging film of the present invention.

[0218] Example IV-1

[0219] It was carried out with reference to Example II-1a, except that the melting point of the first film layer in the selected packaging film was 140.8°C. See Table IV-1 for details.

[0220] Example IV-2

[0221] It was carried out with reference to Example II-1a, except that the melting point of the first film layer in the selected packaging film was 120.3°C. See Table IV-1 for details.

[0222] Example IV-3

[0223] It was carried out with reference to Example II-1a, except that the melting point of the first film layer in the selected packaging film was 165.6°C. See Table IV-1 for details.

[0224] Table IV-1

[0225]

[0226] The batteries obtained from the fourth group of Examples were respectively subjected to a sealing test, a whole machine drop test, a 130°C hot box test, and a 140°C hot box test. The results obtained from the fourth group of Examples were recorded in Table IV-2.

[0227] Table IV-2

[0228]

[0229] As can be seen from Table IV-2 and the examples, for the battery made from the insulating glue, separator and packaging film of the present invention, the passing rate of the seal test is relatively high, and the passing rate of the overall machine drop test is relatively high, indicating that the battery has a good sealing effect. The passing rate of the 130°C hot box test is relatively high, the passing rate of the 120°C open test is relatively high, and the passing rate of the 130°C open test is relatively high, indicating that when the battery undergoes thermal runaway, it can open in time and the battery has high safety performance.

[0230] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An insulating glue, characterized in that, The insulating adhesive includes at least three melting regions. Among them, the melting peak a1 of the first melting region is 95°C - 115°C, the melting peak a2 of the second melting region is 115°C - 130°C, and the melting peak a3 of the third melting region is 140°C - 165°C. The temperature T3 of the melting peak a3 of the third melting region and the temperature T1 of the melting peak a1 of the first melting region satisfy the following relational expression: b = T3 - T1, where the unit of b is °C, and b is 25°C - 70°C.

2. The insulating adhesive according to claim 1, wherein, b is 40°C - 60°C; And / or, the insulating adhesive includes at least a first adhesive layer and a second adhesive layer. The second adhesive layer is located on the surface of one side of the first adhesive layer. The melting point of the first adhesive layer is 95°C - 130°C, and the melting point of the second adhesive layer is 140°C - 170°C.

3. The insulating adhesive according to claim 2, wherein, The insulating adhesive includes a third adhesive layer. The third adhesive layer is located on the surface of the second adhesive layer away from the first adhesive layer. The insulating adhesive satisfies: the melting point of the second adhesive layer > the melting point of the third adhesive layer, and / or, the melting point of the second adhesive layer > the melting point of the first adhesive layer; And / or, the melting point of the third adhesive layer is 95°C - 130°C; And / or, the difference between the melting point of the third adhesive layer and the melting point of the first adhesive layer is -5°C to 25°C.

4. The insulating adhesive according to claim 3, wherein, The melting point of the first adhesive layer includes the melting peak a1 of the first melting region and the melting peak a2 of the second melting region; And / or, the melting point of the second adhesive layer includes the melting peak a3 of the third melting region; And / or, the melting point of the third adhesive layer includes the melting peak a1 of the first melting region and the melting peak a2 of the second melting region.

5. The insulating adhesive according to claim 3 or 4, wherein The first adhesive layer includes a first modified resin. The first modified resin includes a first modified resin A1 and a first modified resin A2. Among them, the melting point d1 of the first modified resin A1 is 95°C ≤ d1 ≤ 115°C, and the melting point d2 of the first modified resin A2 is 115°C < d2 ≤ 130°C. Then, based on the total weight of the first adhesive layer, the weight content of the first modified resin A1 ≥ 50wt%, and the weight content of the first modified resin A2 ≤ 50wt%; And / or, the third adhesive layer includes a second modified resin. The third adhesive layer includes a second modified resin C1 and a second modified resin C2. Among them, the melting point f1 of the second modified resin C1 is 95°C ≤ f1 ≤ 115°C, and the melting point f2 of the second modified resin C2 is 115°C < f2 ≤ 130°C. Then, based on the total weight of the third adhesive layer, the weight content of the second modified resin C1 ≥ 50wt%, and the weight content of the second modified resin C2 ≤ 50wt%.

6. The insulating adhesive according to claim 5, wherein, The first modified resin includes one or more of maleic anhydride modified polypropylene, acrylic acid modified polypropylene, metallocene modified polypropylene, propylene - ethylene copolymer, and butene - propylene copolymer; And / or, the second adhesive layer includes one or more of polypropylene, block polypropylene, and copolymerized polypropylene; among them, the block polypropylene includes alternating propylene - ethylene segments and / or alternating butene - propylene segments, and the copolymerized polypropylene includes ethylene - propylene copolymerization and / or butene - propylene copolymerization; And / or, the second modified resin includes one or more of maleic anhydride modified polypropylene, acrylic acid modified polypropylene, metallocene modified polypropylene, propylene-ethylene copolymer, and butene-propylene copolymer.

7. A battery, characterized in that, The battery includes the insulating adhesive according to any one of claims 1-6.

8. The battery according to claim 7, wherein, The battery includes a pole piece assembly and a separator. The pole piece assembly includes a pole piece and a pole piece conductive material. The pole piece includes a current collector and an active material layer located on one or both surfaces of the current collector. The pole piece conductive material is located at one end of the current collector. The first end of the conductive material is a welding end, and the welding end is welded to the current collector. The second end opposite to the first end is a protruding end. A glue application area is formed between the welding end and the protruding end. An insulating adhesive is provided on the glue application area. The insulating adhesive covers the surface of the conductive material. The surface of the first glue layer away from the second glue layer in the insulating adhesive is adjacent to the conductive material. In the insulating adhesive, the difference b between the temperature T3 of the melting peak a3 of the third melting region and the temperature T1 of the melting peak a1 of the first melting region, in °C, and the adhesion force c between the separator and the pole piece, in N / m, then the battery satisfies the following relationship: 1.7 ≤ b / c ≤ 50, preferably 3.5 ≤ b / c ≤ 30; And / or, b is 25°C - 70°C, preferably 40°C - 60°C; And / or, c is 0.5 N / m ≤ c ≤ 15 N / m, preferably 2 N / m ≤ c ≤ 12 N / m.

9. The battery according to claim 8, wherein, The separator includes a carrier layer and a polymer layer located on one or both surfaces of the carrier layer. The polymer layer includes polymer clusters. Based on the total area of the carrier layer, the area covered by the polymer clusters is 5% - 50%; And / or, the polymer clusters are arranged in a regular or irregular dispersion, forming channels with voids between the polymer clusters. Preferably, the polymer clusters are arranged in a dot matrix; And / or, the distance a between the polymer clusters is 50 μm ≤ a ≤ 5000 μm. And / or, the polymer clusters are secondary particles formed by polymer polymerization. The polymer includes one or more of acrylic acid, acrylate, methacrylic acid, methacrylate, vinylidene fluoride, acrylonitrile, styrene, vinyl chloride, perfluoropropylene, chlorotrifluoroethylene, tetrafluoroethylene, vinylidene chloride, and tetrachloroethylene.

10. The battery according to any one of claims 8 or 9, wherein The battery includes a packaging film. The packaging film is connected to the insulating adhesive to form a sealed shell. The pole piece assembly and the separator are located in the enclosed space formed by the sealed shell. The packaging film includes an inner film layer connected to the second glue layer or the third glue layer in the insulating adhesive, a metal layer located on the surface of the inner film layer, and an outer film layer located on the surface of the metal layer. The inner film layer includes a first film layer directly connected to the second glue layer or the third glue layer in the insulating adhesive and a second film layer located between the first film layer and the metal layer. The melting point of the first film layer is 120°C - 165°C, preferably 130°C - 145°C; And / or, the difference between the melting point of the first film layer and the melting point of the second glue layer or the third glue layer is -5°C to 40°C; And / or, the first film layer comprises modified polypropylene and / or propylene-ethylene copolymer; And / or, the modified polypropylene comprises one or more of maleic anhydride modified polypropylene, metallocene modification, ethylene-propylene copolymer and silane coupling modified polypropylene.

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