Electrochemical device and electronic equipment

Abstract

An electrochemical device (100) and an electronic device, the electrochemical device (100) comprising a first housing (12) provided with a first sealing surface (1222), a second housing (14) provided with a second sealing surface (1422), a first electrode assembly (30) comprising a first tab assembly (32) and a first tab (34), a second electrode assembly (40) comprising a second tab assembly (42) and a second tab (44), a first tab adhesive (50), a second tab adhesive (60), and a separator (20) arranged between the first housing (12) and the second housing (14) and forming a first cavity (101) for accommodating the first tab assembly (32) and a second cavity (102) for accommodating the second tab assembly (42). The first tab (34) comprises a first sealing portion (342) provided with the first tab adhesive (50) and the second tab adhesive (60) on two surfaces respectively, a distance D1 between a first surface (3421) of the first sealing portion (342) and the first sealing surface (1222) is less than a distance D2 between a second surface (3422) of the first sealing portion (342) and the second sealing surface (1422), a melting point of the first tab adhesive (50) arranged on the first surface (3421) is T1, a melting point of the second tab adhesive (60) arranged on the second surface (3422) is T2, and T1>T2 is satisfied. In this way, the packaging reliability of the sealing area (100a) can be improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrochemical device and electronic device. Background Technology

[0002] Currently, batteries are widely used in electronic products such as drones, mobile phones, tablets, and laptops. In some applications, a single battery cell cannot achieve the desired output power; therefore, multiple battery cells are typically connected in series, parallel, or a combination thereof to work together to achieve the desired power output. However, while connecting multiple battery cells in series, parallel, or a combination thereof can increase output power, the energy density of the entire battery pack is relatively low. Therefore, the design of series / parallel batteries within the same bag has been proposed. These batteries include a casing and multiple electrode assemblies housed within the same casing. Series-connected electrode assemblies are separated by separators to prevent electrolyte decomposition under high voltage, while parallel-connected electrode assemblies are separated by separators to prevent mutual interference. The tabs of the multiple electrode assemblies extend from the sides of the casing for connection outside the casing. Summary of the Invention

[0003] The inventors of this application discovered through research that, due to the presence of separators between the electrode components in series / parallel batteries within the same bag, uneven melting of the tab adhesive on the two opposing surfaces of the tabs can easily occur during heat sealing due to the different distances between the tab adhesive and the heat sealing head, posing a risk of poor sealing.

[0004] In view of the above-mentioned technical problems, this application provides an electrochemical device and an electronic device to improve the safety of the electrochemical device.

[0005] To solve the above technical problems, in a first aspect of the present application, an electrochemical device is provided, comprising a first housing, a second housing, a separator, a first electrode assembly, a second electrode assembly, a first tab adhesive and a second tab adhesive. The separator is located between the first housing and the second housing. The electrochemical device is provided with a first cavity between the first housing and the separator, and a second cavity between the second housing and the separator. The first electrode assembly comprises a first tab and a first pole piece assembly received in the first cavity. The second electrode assembly comprises a second tab and a second pole piece assembly received in the second cavity. The electrochemical device comprises a sealing region. The first housing comprises a first sealing surface located in the sealing region and facing away from the separator. The second housing comprises a second sealing surface located in the sealing region and facing away from the separator. The first tab comprises a first sealing portion located in the sealing region. The first sealing portion comprises a first surface and a second surface opposite to each other. Along the thickness direction of the sealing region, the first surface is adjacent to the first sealing surface relative to the second surface, the second surface is adjacent to the second sealing surface relative to the first surface, the distance from the first surface to the first sealing surface is D1, the distance from the second surface to the second sealing surface is D2, and D1<D2. The first tab adhesive is arranged on the first surface, and the second tab adhesive is arranged on the second surface. The melting point of the first tab adhesive is T1, and the melting point of the second tab adhesive is T2, which satisfies T1>T2. In this way, when the sealing region is sealed, even if the temperature inside the sealing region far away from the sealing head is low, since the melting point of the second tab adhesive is lower than that of the first tab adhesive, the second tab adhesive can still be well melted, reducing the occurrence of the phenomenon that the first tab adhesive has been fully melted while the second tab adhesive is not melted or not sufficiently melted, which is beneficial to improving the sealing effect of the sealing region and enhancing the safety of the electrochemical device. Further, T1-T2≥7°C is satisfied. Further, T1-T2≤40°C is satisfied.

[0006] Optionally, the electrochemical device further includes a third tab adhesive and a fourth tab adhesive; the second tab includes a second sealing portion located in the sealing area, the second sealing portion including a third surface and a fourth surface opposite each other; along the thickness direction of the sealing area, the third surface is adjacent to the first sealing surface relative to the fourth surface, the fourth surface is adjacent to the second sealing surface relative to the third surface, the distance from the third surface to the first sealing surface is D3, and the distance from the fourth surface to the second sealing surface is D4; the third tab adhesive is disposed on the third surface, and the fourth tab adhesive is disposed on the fourth surface; wherein, the melting point of the third tab adhesive is T3, the melting point of the fourth tab adhesive is T4, and any one of the following conditions is satisfied: (1) D4<D3;T4> T3;(2)D3<D4;T3> T4. Thus, during the encapsulation process, both the third and fourth electrode tab adhesives can be effectively heat-melted, reducing the risk that only one of them will be in a heat-melted state. This improves the sealing effect of the second electrode tab in the sealing area and further enhances the safety of the electrochemical device. Furthermore, it satisfies T4-T3≥7℃ or T3-T4≥7℃. Furthermore, it satisfies T4-T3≤40℃ or T3-T4≤40℃.

[0007] Optionally, the thickness of the first tab adhesive is t1, and the thickness of the second tab adhesive is t2, satisfying: 1.5t2≤t1≤2t2. This ensures that, in the thickness direction of the sealing area, the thickness t1 of the first tab adhesive is greater than the thickness t2 of the second tab adhesive, thereby reducing the risk of the first tab adhesive being excessively melted and extruded due to the higher temperature, which is beneficial for improving the sealing effect of the sealing area.

[0008] Optional, 0.075mm≤t1≤0.6mm. Optional, 0.05μm≤t2≤0.3mm.

[0009] Optionally, the final melting temperature of the second tab adhesive is Th2, satisfying Th2>T1. When this relationship is satisfied, it can be ensured that the first tab adhesive has begun to melt before the second tab adhesive has completely melted, thus ensuring a good seal between the first and second tab adhesives in the sealing area.

[0010] Optionally, the final melting temperature of the third electrode adhesive is Th3, and the final melting temperature of the fourth electrode adhesive is Th4, satisfying either of the following conditions: (d)D4<D3;T4-T3≥7℃;Th3> T4;(e)D3<D4;T3-T4≥7℃;Th4> T3. In this way, during the encapsulation process, it can be ensured that when one of the third and fourth electrode adhesives is completely melted, the other has already begun to melt. This allows the third and fourth electrode adhesives to melt simultaneously, reducing the risk that only one of them is in a melted state. This results in good fusion of the third and fourth electrode adhesives in the sealing area, which is beneficial to improving the sealing effect of the second electrode in the sealing area.

[0011] Optionally, Th2-T2 ≥ 25℃. This gives the second tab adhesive a wider melting range, reducing the risk of the second tab adhesive being over-melted and extruded.

[0012] Optionally, the separator includes a substrate layer and an encapsulation layer located on the surface of the substrate layer.

[0013] Optionally, the first electrode assembly and the second electrode assembly are connected in series.

[0014] In a second aspect, this application also provides an electronic device including the electrochemical device described above.

[0015] The beneficial effects of this application are as follows: In the electrochemical device provided by this application, the distance between the first electrode adhesive and the first sealing surface is D1 in the thickness direction of the sealing area, and the distance between the second electrode adhesive and the second sealing surface is D2. When D1 < D2, by making the melting points of the first electrode adhesive and the second electrode adhesive different, and the melting point T1 of the first electrode adhesive is greater than the melting point T2 of the second electrode adhesive, the second electrode adhesive can still melt well when the sealing area is sealed, even when the temperature inside the sealing area far from the end cap is low. This is because the melting point of the second electrode adhesive is lower than that of the first electrode adhesive, thus reducing the occurrence of the phenomenon that the first electrode adhesive has fully melted while the second electrode adhesive has not melted or has not melted sufficiently. This is beneficial to improving the sealing effect of the sealing area and improving the safety of the electrochemical device. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings.

[0017] Figure 1 This is a schematic diagram of the structure of an electrochemical device according to one embodiment of this application;

[0018] Figure 2 yes Figure 1 A structural decomposition diagram from one perspective;

[0019] Figure 3 yes Figure 1 Another perspective on the structural decomposition diagram;

[0020] Figure 4 yes Figure 1 A schematic diagram showing the cross-section along line MM;

[0021] Figure 5 This is a schematic diagram of an embodiment where the electrode assembly is a wound structure;

[0022] Figure 6 This is a schematic diagram of an electrode assembly in another embodiment, where the electrode assembly is a stacked structure.

[0023] Figure 7 This is a schematic diagram of removing the tab adhesive from the sealing area;

[0024] Figure 8 yes Figure 4 Enlarged view of part A;

[0025] Figure 9 yes Figure 1 The right view. Detailed Implementation

[0026] To facilitate understanding of this application, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "connected" to another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this specification are for illustrative purposes only.

[0027] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0028] like Figure 1-4 As shown, one embodiment of the present application provides an electrochemical device 100, including a housing 10, a separator 20, and an electrode assembly. The housing 10 is used to define an enclosed space for accommodating the electrode assembly, and the separator 20 is used to separate the internal space of the housing 10, thereby increasing the number of independent cavities inside the housing 10.

[0029] The electrochemical device 100 may include one or more isolators 20. When the electrochemical device 100 includes one isolator 20, the isolator 20 can divide the internal space of the housing 10 into two independent cavities, referred to as the first cavity 101 and the second cavity 102. When the electrochemical device 100 includes multiple isolators 20, the multiple isolators 20 can divide the internal space of the housing 10 into multiple independent cavities. For example, when the electrochemical device 100 specifically includes two isolators 20, the two isolators 20 can divide the internal space of the housing 10 into three independent cavities; when the electrochemical device 100 includes three isolators 20, the three isolators 20 can divide the internal space of the housing 10 into four independent cavities.

[0030] In some embodiments, please combine Figure 2-4 As shown, the housing 10 includes a first housing 12 and a second housing 14. The electrochemical device has a first cavity 101 between the first housing 12 and the spacer 20, and a second cavity 102 between the second housing 14 and the spacer 20. The spacer 20 is located between the first housing 12 and the second housing 14. The first housing 12 has a first encapsulation portion 122, which is used to fix a connection (either by heat fusion or bonding) to a surface of the spacer 20. The first encapsulation portion 122 has a first sealing surface 1222 facing away from the spacer 20, which can contact the sealing head during encapsulation. The second housing 14 has a second encapsulation portion 142, which is used to fix a connection (either by heat fusion or bonding) to a surface of the spacer 20. The second encapsulation portion 142 has a second sealing surface 1422 facing away from the spacer 20, which can contact the sealing head during encapsulation.

[0031] To facilitate understanding of the possible conditions of the housing 10, Figure 1 Taking the shape of the housing 10 shown as an example, in one case, the first housing 12 and the second housing 14 are two independent parts, and the four edges of the surfaces of the first housing 12 and the second housing 14 used for sealing with the spacer 20 are sealed with the spacer. In another case, the first housing 12 and the second housing 14 are two integrally connected parts, that is, the surfaces of the first housing 12 and the second housing 14 used for sealing with the spacer 20 have one edge that is integrally connected. That is, the housing 10 can be formed by processing a first cavity 101 and a second cavity 102 from a single piece of plate and then folding it in half, thereby forming the first housing 12 and the second housing 14.

[0032] The isolator 20 includes an encapsulation area 21. When the electrochemical device 100 is encapsulated, the portion of the isolator 20 located in the encapsulation area 21 is sealed to other components. That is, the portion of the isolator 20 in the encapsulation area 21 is fixedly connected to other components (either by heat fusion or bonding). When the electrochemical device 100 has only one isolator 20, both sides of the encapsulation area 21 of the isolator 20 are connected to the housing 10. When the electrochemical device 100 has two isolators 20, one side of the encapsulation area 21 of one isolator 20 is connected to the other isolator 20, and the other side is connected to the housing 10. When there are three or more isolators 20, both sides of the encapsulation area 21 of the middle isolator 20 are connected to the other isolators 20 located on either side of it. For ease of description, the following detailed description assumes that the electrochemical device includes only one isolator 20.

[0033] In some embodiments, the encapsulation area 21 may be U-shaped and may extend to the outer edge of the separator 20. The encapsulation area 21 may also be spaced a certain distance from the outer edge of the separator 20. The encapsulation area 21 is fixedly connected to the first encapsulation portion 122 and the second encapsulation portion 142, thereby forming the sealing area 100a of the electrochemical device 100. In other embodiments, the encapsulation area 21 may be U-shaped, in which case the first housing 12 and the second housing 14 are two integrally connected parts. In this embodiment, the thickness direction Z of the sealing area 100a refers to the direction in which the first encapsulation portion 122, the encapsulation area 21, and the second encapsulation portion 142 are stacked, and the thickness direction Z of the sealing area 100a is the same as the thickness direction of the separator 20.

[0034] The electrochemical device 100 may include two electrode assemblies or more than three electrode assemblies. For ease of description, the following embodiments illustrate that the electrochemical device 100 includes two electrode assemblies. Figure 4 As shown, the two electrode assemblies are a first electrode assembly 30 and a second electrode assembly 40. When the electrochemical device 100 has a separator 20 that separates two independent cavities, the first electrode assembly 30 is disposed in the first cavity 101, and the second electrode assembly 40 is disposed in the second cavity 102. The first electrode assembly 30, the separator 20, and the second electrode assembly 40 are distributed along a first direction, which is the same as the thickness direction Z of the separator 20.

[0035] In some embodiments, the first electrode assembly 30 includes a first electrode assembly 32 and a first tab 34 connected to the first electrode assembly 32, wherein there are at least two first tabs 34, and the polarities of the at least two first tabs 34 are opposite. The second electrode assembly 40 includes a second electrode assembly 42 and a second tab 44 connected to the second electrode assembly 42, wherein there are at least two second tabs 44, and the polarities of the at least two second tabs 44 are opposite.

[0036] Understandably, on the one hand, multiple first electrodes 34 and multiple second electrodes 44 can all extend out of the housing 10 from the same side edge, and at least one first electrode 34 is connected to one second electrode 44, so that the first electrode assembly 30 and the second electrode assembly 40 are connected. If the connected first electrodes 34 and second electrodes 44 have the same polarity, then the first electrode assembly 30 and the second electrode assembly 40 are connected in parallel. If the connected first electrodes 34 and second electrodes 44 have different polarities, then the first electrode assembly 30 and the second electrode assembly 40 are connected in series. On the other hand, multiple first electrodes 34 and multiple second electrodes 44 can extend out of the housing 10 from different side edges, and at least one first electrode 34 is connected to one second electrode 44.

[0037] To facilitate understanding of the structure of the first electrode assembly 32 and the second electrode assembly 42, the following explanation uses the first electrode assembly 32 as an example:

[0038] Please combine Figure 5 and Figure 6 The first electrode assembly 32 includes a first electrode 322, a second electrode 324, and a separator 326. The separator 326 is disposed between the first electrode 322 and the second electrode 324. The first electrode 322 and the second electrode 324 have opposite polarities. The separator 326 is used to reduce the risk of short circuit caused by contact between the first electrode 322 and the second electrode 324.

[0039] In some embodiments, such as Figure 5 As shown, the first electrode assembly 32 has a wound structure, that is, the first electrode 322, the separator 326, and the second electrode 324 are stacked along the first thickness direction and then wound along the first long side direction. Here, the first thickness direction refers to the thickness direction of any one of the three components: the first electrode 322, the separator 326, and the second electrode 324. The first long side direction refers to the long side direction of any one of the three components. In this embodiment, the first thickness direction is the same as the thickness direction Z of the separator 20. In other embodiments, such as... Figure 6As shown, the first electrode assembly 32 has a stacked structure, meaning that the first electrode 322, the separator 326, and the second electrode 324 are stacked along the first thickness direction. There are multiple first electrode 322s, separators 326, and second electrode 324s. Along the first thickness direction, a separator 326 is disposed between each first electrode 322 and each second electrode 324. The first thickness direction refers to the thickness direction of any one of the three components: the first electrode 322, the second electrode 324, and the separator 326. This first thickness direction is the same as the thickness direction Z of the separator 20.

[0040] Understandably, the structure of the first electrode assembly 32 can be applied to the second electrode assembly 42, that is, it can be the winding structure or the stacked structure described above, which can be selected according to actual needs. The structures used by the first electrode assembly 32 and the second electrode assembly 42 can be the same or different. For example, if the first electrode assembly 32 adopts a winding structure, then the second electrode assembly 42 can adopt a winding structure or a stacked structure.

[0041] Please see Figure 7 The first electrode tab 34 includes a first connecting portion 341, a first sealing portion 342, and a first protruding portion 343 connected in sequence. The first connecting portion 341 is used to connect with the first electrode assembly 32. The first sealing portion 342 is located in the sealing area 100a, and the first protruding portion 343 is located outside the housing 10. The first sealing portion 342 includes a first surface 3421 and a second surface 3422 disposed opposite to each other.

[0042] The second electrode tab 44 includes a second connecting portion 441, a second sealing portion 442, and a second protruding portion 443 connected in sequence. The second connecting portion 441 is used to connect with the second electrode assembly 42. The second sealing portion 442 is located in the sealing area 100a, and the second protruding portion 443 is located outside the housing 10. The second sealing portion 442 includes a third surface 4421 and a fourth surface 4422 disposed opposite to each other.

[0043] The inventors of this application have discovered that when encapsulating the separator and the housing, due to the need for multi-layer encapsulation, the encapsulation temperature is high in the area near the heat seal head and low in the area away from the heat seal head. In the area with the low encapsulation temperature, the tab adhesive is prone to poor fusion, while in the area with the high encapsulation temperature, the tab adhesive is prone to over-melting and extrusion. To ensure good fusion of both inner and outer tab adhesives, this application applies a high-melting-point tab adhesive to the side of the same tab closest to the heat seal head and a low-melting-point tab adhesive to the side away from the heat seal head. This allows the tab adhesive on both opposite surfaces of the tab to fused well with the separator and the housing 10 during the sealing process. Thus, as... Figure 8 and Figure 9As shown, the electrochemical device 100 of the present application further includes a first tab glue 50 and a second tab glue 60, where the melting point of the first tab glue 50 is T1, and the melting point of the second tab glue 60 is T2. The melting point refers to the temperature at which a meltable element starts to melt from a solid state into a liquid state when tested by a microscopic melting point apparatus.

[0044] To facilitate understanding of the arrangement manner of the first tab glue 50 and the second tab glue 60 in the thickness direction of the sealing area 100a in the present application, the distribution of the first tab glue 50 and the second tab glue 60 on the first sealing portion 342 of one of the first tabs 34 is described below as an example.

[0045] Please refer to again Figure 7 , along the thickness direction Z of the sealing area 100a, the first surface 3421 is adjacent to the first sealing surface 1222 relative to the second surface 3422, the second surface 3422 is adjacent to the second sealing surface 1422 relative to the first surface 3421, the distance from the first surface 3421 to the first sealing surface 1222 is D1, and the distance from the second surface 3422 to the second sealing surface 1422 is D2, which satisfies: D1<D2. The first tab glue 50 is disposed on the first surface 3421, and the second tab glue 60 is disposed on the second surface 3422, then T1>T2. In this way, both the first tab glue 50 and the second tab glue 60 can be sufficiently hot-melted during the heat sealing process, so that the sealing area 100a is well sealed, and thus no liquid leakage occurs in the electrochemical device 100. Further, T1-T2≥7°C.

[0046] In some embodiments, D1<D2, T1>T2, and the final melting temperature of the second tab glue 60 is Th2, which satisfies Th2>T1. The final melting temperature refers to the temperature at which a meltable element is just completely melted from a solid state into a liquid state when tested by a microscopic melting point apparatus. When Th2>T1 is satisfied, the first tab glue 50 has started to melt before the second tab glue 60 is completely melted, which reduces the risk that the second tab glue 60 on the second surface 3422 is excessively melted to affect the sealing effect. In some embodiments, the difference between the final melting temperature Th2 of the second tab glue 60 and the melting point T2 of the second tab glue 60 is not less than 25°C, that is, Th2-T2≥25°C. In this way, the second tab glue 60 has a wide melting range, which reduces the risk of the second tab glue 60 being excessively melted and squeezed out.

[0047] Similarly, the distribution of the tab glue on the surface of the second sealing portion 442 is the same as that of the above-mentioned first sealing portion 342. In order to distinguish from the tab glue disposed on the surface of the first sealing portion 342, the tab glue disposed on the surface of the second sealing portion 442 is defined as a third tab glue 70 and a fourth tab glue 80 respectively, and the melting point of the third tab glue 70 is T3, and the melting point of the fourth tab glue 80 is T4.

[0048] Along the thickness direction Z of the sealing area 100a, the third surface 4421 is adjacent to the first sealing surface 1222 relative to the fourth surface 4422, and the fourth surface 4422 is adjacent to the second sealing surface 1422 relative to the third surface 4421. The distance from the third surface 4421 to the first sealing surface 1222 is D3, and the distance from the fourth surface 4422 to the second sealing surface 1422 is D4. Since D3 > D4, then T4 > T3. Thus, both the third electrode adhesive 70 and the fourth electrode adhesive 80 can be fully melted during the heat sealing process, ensuring a good seal in the sealing area 100a and preventing leakage from the electrochemical device 100. Furthermore, T4 - T3 ≥ 7℃.

[0049] In some embodiments, D3 > D4, T4 > T3, and the final melting temperature of the third electrode adhesive 70 is Th3, satisfying Th3 > T4. When Th3 > T4, the fourth electrode adhesive 80 begins to melt before the third electrode adhesive 70 completely melts, reducing the risk of excessive melting of the third electrode adhesive 70 on the third surface 4421, which could affect the sealing effect. In some embodiments, the difference between the final melting temperature Th3 of the third electrode adhesive 70 and the melting point T3 of the third electrode adhesive 70 is not less than 25°C, i.e., Th3 - T3 ≥ 25°C.

[0050] To facilitate understanding of the distribution of tab adhesive on the surfaces of the first tab 34 of the first electrode assembly 30 and the second tab 44 of the second electrode assembly 40, the melting point T1 of the first tab adhesive 50 is set to be greater than the melting point T2 of the second tab adhesive 60, and the melting point T3 of the third tab adhesive 70 is set to be less than the melting point of the fourth tab adhesive 80. Figure 9 Taking the electrode assembly distribution shown as an example, along the thickness direction Z of the sealing area 100a, the second electrode assembly 40 is located below the first electrode assembly 30. The first electrode tab 34, used to connect with the second electrode tab 44, should have a second surface 3422 for connection to the separator 20 during sealing, due to the thickness of the separator 20 to which it is connected. This means a second electrode tab adhesive 60 with a lower melting point should be provided. The surface of the first electrode tab 34 facing away from the second electrode tab 44 should be a first surface 3421, meaning a first electrode tab adhesive 50 with a higher melting point should be provided. Similarly, the surface of the second electrode tab 44 for connection to the separator 20 should be a third surface 4421, meaning a third electrode tab adhesive 70 with a lower melting point should be provided. The surface of the second electrode tab 44 facing away from the separator 20 should be a fourth surface 4422, and a fourth electrode tab adhesive 80 with a higher melting point should be provided on the fourth surface 4422.

[0051] Similarly, when the electrochemical device 100 includes three or more electrode assemblies, along the direction of the sealing area 100a, the side closest to the housing sealing surface should be provided with a high melting point tab adhesive, while the other side should be provided with a low melting point tab adhesive.

[0052] In some embodiments, such as Figure 8 As shown, the thickness of the first tab adhesive 50 is t1, and the thickness of the second tab adhesive 60 is t2, satisfying: 1.5t2≤t1≤2t2; thus, the risk of the first tab adhesive 50 being over-melted and extruded due to the high temperature can be reduced, which is beneficial to improving the sealing effect of the sealing area.

[0053] In some embodiments, 0.075mm ≤ t1 ≤ 0.6mm. In some embodiments, 0.05mm ≤ t2 ≤ 0.3mm.

[0054] In some embodiments, the separator 20 includes a substrate layer and an encapsulation layer disposed on the substrate layer.

[0055] The substrate layer is made of at least one of a metal, a carbon material, or a first polymer. Metals include Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, and I. At least one of n, Zn, stainless steel and their compositions or alloys; carbon materials include at least one of carbon felt, carbon film, carbon black, acetylene black, fullerene, conductive graphite film or graphene film; the first polymer includes at least one of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamide-imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polypropylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-trifluorochloroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer or derivatives thereof.

[0056] The encapsulation layer is made of a second polymer. The second polymer includes at least one of the following: polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous α-olefin copolymer, or derivatives thereof.

[0057] Example 1

[0058] Preparation of lithium-ion batteries

[0059] (1) Preparation of the negative electrode sheet: The negative electrode active materials, artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR), were mixed in a weight ratio of 96:1.5:2.5. Deionized water was added to prepare a slurry with a solid content of 70wt%, and the mixture was stirred evenly. The slurry was uniformly coated on one surface of the negative electrode current collector copper foil and dried to obtain a negative electrode sheet with a single-sided coating of negative electrode active material. The above steps were repeated on the other surface of the negative electrode current collector copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode active material. After cold pressing, the negative electrode sheet was cut into 41mm×61mm sizes for later use.

[0060] (2) Preparation of the positive electrode sheet: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) was added to prepare a slurry with a solid content of 75 wt%, and the mixture was stirred evenly. The slurry was uniformly coated on one surface of the positive current collector aluminum foil and dried to obtain a positive electrode sheet with a single-sided coating of positive active material. The above steps were repeated on the other surface of the positive current collector aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive active material. After cold pressing, the positive electrode sheet was cut into 38 mm × 58 mm dimensions for later use.

[0061] (3) Preparation of electrolyte: In a dry argon atmosphere, the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a LiPF6 concentration of 12.5% ​​based on the mass of the electrolyte.

[0062] (4) Preparation of the first and second electrode assemblies: The separator, negative electrode, separator, and positive electrode are stacked sequentially to form a stacked structure. Then, the four corners of the entire stacked structure are fixed to obtain the electrode assembly. Each electrode assembly includes a positive electrode tab and a negative electrode tab. The positive electrode tab is made of aluminum (Al), and the negative electrode tab is made of nickel (Ni). The two tabs are arranged side by side. The separator is a polyethylene (PE) film with a thickness of 15 μm.

[0063] (5) Preparation of the separator: Polypropylene (PP, melting point 140℃) encapsulation layer material is uniformly dispersed in dispersant N-methylpyrrolidone (NMP) to prepare PP suspension; PP suspension is coated on both sides of aluminum layer with a thickness of 50μm using a coating machine; then it is dried at 130℃, wherein the thickness of PP encapsulation layer on one side of aluminum layer is 25μm, and the total thickness of the separator is 100μm.

[0064] (6) Electrode assembly assembly: Place the first aluminum-plastic film (150μm thick) with the dented surface facing upwards in the assembly fixture. Place the first electrode assembly in the dent, and apply a first tab adhesive to the surface of the first electrode assembly near the first aluminum-plastic film and a second tab adhesive to the surface away from the first aluminum-plastic film (see Table 1 for specific melting point and other parameters). Then place the spacer on the first electrode assembly, aligning the edges, and apply external force to press it to obtain the assembled semi-finished product. Place the assembled semi-finished product in the assembly fixture, with the spacer facing upwards. Place the second electrode assembly on the spacer, aligning the edges, and apply external force to press it to tighten it. Then cover the second electrode assembly with another second aluminum-plastic film with the dented surface facing downwards, and apply a first tab adhesive to the surface of the second electrode assembly near the second aluminum-plastic film and a second tab adhesive to the surface away from the second aluminum-plastic film (see Table 1 for specific melting point and other parameters). Lead the positive and negative tabs of both the first and second electrode assemblies out of the aluminum-plastic film, and use hot pressing to seal the top and sides to obtain the assembled electrode assembly.

[0065] (7) Liquid injection and sealing: Each cavity is injected with electrolyte, and then sealed after hot pressing, formation and degassing.

[0066] (8) Series connection: The negative electrode tab of the first electrode assembly and the positive electrode tab of the second electrode assembly are welded together by laser welding to achieve series connection, and the lithium-ion battery assembly is completed.

[0067] Examples 2-5 and Comparative Examples

[0068] The only difference from Example 1 is the selection of the first and second tab adhesives, as detailed in Table 1.

[0069] Table 1. Electrochemical device encapsulation test results for first and second electrode adhesives of different thicknesses and melting points.

[0070]

[0071] The test results obtained in Examples 1-6 and the comparative examples in Table 1 were obtained using the following method: A multi-functional peeling device was used to first clamp the housing and spacer on one side of the encapsulation area, and then pull them apart to separate the first or second encapsulation part of the housing from the encapsulation of the spacer. The adhesion of the tab adhesive after separation was observed. If the color of the adhesive after separation was milky white, it indicated that the tab adhesive was well fused; if there were local areas where the milky white color was not obvious, it indicated that the tab adhesive was poorly fused. A comparison of Examples 1-6 and the comparative examples in Table 1 shows that when T1-T2 ≥ 7℃, the sealing area 100a of the electrochemical device 100 fused well, indicating that when the melting point of the first tab adhesive was greater than that of the second tab adhesive, the second tab adhesive 60 could melt well, thereby improving the encapsulation reliability and safety of the electrochemical device.

[0072] This application also provides an electronic device comprising the electrochemical device provided in this application. The electronic device in this application is not particularly limited and can be any electronic device known in the prior art. For example, electronic devices include, but are not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0073] It should be noted that while the preferred embodiments of the present invention are given in the specification and accompanying drawings, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of the present invention; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of the present invention. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of the present invention specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An electrochemical device, characterized in that, comprising: a first housing and a second housing; a separator, disposed between the first housing and the second housing, the electrochemical device being provided with a first cavity between the first housing and the separator, and the electrochemical device being provided with a second cavity between the second housing and the separator; a first electrode assembly and a second electrode assembly, wherein the first electrode assembly comprises a first pole piece assembly and a first tab, the first pole piece assembly being accommodated in the first cavity; the second electrode assembly comprises a second pole piece assembly and a second tab, the second pole piece assembly being accommodated in the second cavity; a first tab adhesive and a second tab adhesive; the electrochemical device comprises a sealing region, the first housing comprises a first sealing surface located in the sealing region and facing away from the separator, the second housing comprises a second sealing surface located in the sealing region and facing away from the separator, the first tab comprises a first sealing portion located in the sealing region, and the first sealing portion comprises a first surface and a second surface opposite to each other; along the thickness direction of the sealing region, the first surface is adjacent to the first sealing surface relative to the second surface, the second surface is adjacent to the second sealing surface relative to the first surface, the distance from the first surface to the first sealing surface is D1, the distance from the second surface to the second sealing surface is D2, and D1<D2; the first tab adhesive is disposed on the first surface, and the second tab adhesive is disposed on the second surface; wherein the melting point of the first tab adhesive is T1, the melting point of the second tab adhesive is T2, and 7°C≤T1-T2≤40°C is satisfied.

2. The electrochemical device according to claim 1, characterized in that, the electrochemical device further comprises a third tab adhesive and a fourth tab adhesive; the second tab comprises a second sealing portion located in the sealing region, and the second sealing portion comprises a third surface and a fourth surface opposite to each other; along the thickness direction of the sealing region, the third surface is adjacent to the first sealing surface relative to the fourth surface, the fourth surface is adjacent to the second sealing surface relative to the third surface, the distance from the third surface to the first sealing surface is D3, and the distance from the fourth surface to the second sealing surface is D4; the third tab adhesive is disposed on the third surface, and the fourth tab adhesive is disposed on the fourth surface; wherein the melting point of the third tab adhesive is T3, the melting point of the fourth tab adhesive is T4, and any one of the following conditions is satisfied: (1) D4<D3; T4-T3≥7°C; (2) D3<D4; T3-T4≥7°C.

3. The electrochemical device according to claim 2, characterized in that, |T4-T3|≤40°C.

4. The electrochemical device according to claim 1, characterized in that, the thickness of the first tab adhesive is t1, and the thickness of the second tab adhesive is t2, satisfying at least one of the following conditions: (a) 1.5t2≤t1≤2t2; (b) 0.075mm≤t1≤0.6mm; (c) 0.05mm≤t2≤0.3mm.

5. The electrochemical device according to claim 1, characterized in that, the final melting temperature of the second tab adhesive is Th2, which satisfies: Th2>T1.

6. The electrochemical device according to claim 2, characterized in that, the final melting temperature of the third tab adhesive is Th3, and the final melting temperature of the fourth tab adhesive is Th4, satisfying any one of the following conditions: (d) D4<D3; T4-T3≥7°C; Th3>T4; (e)D3<D4;T3-T4≥7℃;Th4> T3.

7. The electrochemical device according to claim 5, characterized in that, At least one of the following conditions must be met: (i) Th2-T2≥25℃; (ii) The isolation element includes a substrate layer and an encapsulation layer located on the surface of the substrate layer.

8. The electrochemical device according to claim 1, characterized in that, The first electrode assembly and the second electrode assembly are connected in series.

9. An electronic device, characterized in that, Includes the electrochemical device as described in any one of claims 1-8.

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