Electrochemical device and electronic equipment

Abstract

The present application discloses an electrochemical device and an electronic device. The electrochemical device includes a first shell provided with a first sealing surface, a second shell provided with a second sealing surface, and a first separator. The first separator is provided between the first shell and the second shell, and forms a first cavity for accommodating a first electrode assembly and a second cavity for accommodating a second electrode assembly. The first separator includes a substrate layer, a first packaging layer provided on the first surface of the substrate layer, and a second packaging layer provided on the second surface of the substrate layer. The first separator includes a first sealing portion located in a sealing area, the first surface includes a first area located in the first sealing portion, and the second surface includes a second area located in the first sealing portion. Along the thickness direction of the sealing area, the distance D1 between the first sealing surface and the first area is smaller than the distance D2 between the second sealing surface and the second area, and the melting point T1 of the first packaging layer is greater than the melting point T2 of the second packaging layer. In this way, the sealing effect of the sealing area can be improved.

Description

Technical Field

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

[0002] At present, batteries are widely used in electronic products such as drones, mobile phones, tablets, and laptops. Since a single battery cell cannot achieve the desired output power in some application scenarios, multiple battery cells are usually connected in series, in parallel, or in mixed connection so that the multiple battery cells work together to achieve the desired power output. However, although connecting multiple battery cells in series, in parallel, or in mixed connection can increase the output power, the energy density of the entire battery pack is low. Therefore, the design of same-bag series / parallel batteries is proposed. The same-bag series / parallel batteries include a shell and a plurality of electrode assemblies arranged in the same shell. The electrode assemblies in series need to be separated by an isolator to avoid decomposition of the electrolyte under high voltage. The electrode assemblies in parallel are separated by an isolator to avoid interference with each other. The tabs of the multiple electrode assemblies extend from the side of the shell to be connected outside the shell. Summary of the Invention

[0003] The inventors of this application have discovered through research that when heat-sealing batteries in series / parallel in the same bag, there is a temperature difference on both sides of the isolation piece due to the influence of different thickness positions, and there is a risk of poor sealing on the side with lower temperature.

[0004] In view of the above technical problems, the present 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 the first aspect of the present application, there is provided an electrochemical device, including a first housing, a second housing, a first separator, a first electrode assembly, and a second electrode assembly. The first separator is located between the first housing and the second housing. The electrochemical device has a first cavity between the first housing and the first separator, and a second cavity between the second housing and the first separator. The first electrode assembly is accommodated in the first cavity; the second electrode assembly is accommodated in the second cavity. The first separator includes a first base layer, a first encapsulation layer, and a second encapsulation layer. The first encapsulation layer is provided on the first surface of the first base layer, and the second encapsulation layer is provided on the second surface of the first base layer. The first surface and the second surface are opposite to each other. The electrochemical device includes a sealing area, where the first housing, the first separator, and the second housing are connected in the sealing area. The first housing includes a first sealing surface located in the sealing area and facing away from the first separator. The second housing includes a second sealing surface located in the sealing area and facing away from the first separator. The first separator includes a first sealing portion located in the sealing area. The first surface includes a first area located in the first sealing portion, and the second surface includes a second area located in the first sealing portion. Along the thickness direction of the sealing area, the first area is adjacent to the first sealing surface relative to the second area. The distance from the first area to the first sealing surface is D1, and the distance from the second area to the second sealing surface is D2, where D1 < D2. Among them, the melting point of the first encapsulation layer is T1, and the melting point of the second encapsulation layer is T2, satisfying T1 > T2.

[0006] In this way, when sealing the sealing area, since the melting point of the second encapsulation layer is less than that of the first encapsulation layer, even when the temperature inside the sealing area far from the head is relatively low, the second encapsulation layer can still be well melted, reducing the occurrence of the phenomenon that the first encapsulation layer has been fully melted while the second encapsulation layer has not melted or is not fully melted, which is beneficial to improving the sealing effect on the lower temperature side of the first separator, and further improving the safety of the electrochemical device. Further, T1 - T2 ≥ 7°C is satisfied. Further, T1 - T2 ≤ 40°C is satisfied.

[0007] Optionally, the electrochemical device further comprises a second isolating member, the second isolating member being located between the first isolating member and the second shell, the second isolating member comprising a second substrate layer, a third packaging layer and a fourth packaging layer, the third packaging layer being located on the third surface of the second substrate layer, the fourth packaging layer being located on the fourth surface of the second substrate layer, the third surface being opposite to the fourth surface; the second isolating member comprising a second sealing portion located in the sealing area, the third surface comprising a third region located in the second sealing portion, the fourth surface comprising a fourth region located in the second sealing portion; along the thickness direction of the sealing area, the fourth region is adjacent to the second sealing surface relative to the third region, the distance from the third region to the first sealing surface is D3, and the distance from the fourth region to the second sealing surface is D4; wherein the melting point of the third packaging layer is T3, the melting point of the fourth packaging layer is T4, and any one of the following conditions is satisfied: (1) D4<D3;T4> T3; (2) D3<D4;T3> T4.

[0008] When the above conditions are met, during the packaging process, both the third packaging layer and the fourth packaging layer can be well heat-fused, reducing the risk of only one of the third packaging layer and the fourth packaging layer being fully heat-fused while the other is not heat-fused or not fully heat-fused, which is beneficial to improving the sealing effect of the sealing area and further improving the safety of the electrochemical device. Furthermore, T4-T3 ≥ 7°C or T3-T4 ≥ 7°C is met. Furthermore, T4-T3 ≤ 40°C or T3-T4 ≤ 40°C is met.

[0009] Optionally, the electrochemical device also includes a third insulating member, which is located between the first shell and the second shell, and the third insulating member includes a third substrate layer, a fifth packaging layer and a sixth packaging layer, the fifth packaging layer is arranged on the fifth surface of the third substrate layer, and the sixth packaging layer is arranged on the sixth surface of the third substrate layer, and the fifth surface is opposite to the sixth surface; the third insulating member includes a third sealing portion located in the sealing area, the fifth surface includes a fifth area located in the third sealing portion, and the sixth surface includes a sixth area located in the third sealing portion; along the thickness direction of the sealing area, the fifth area is adjacent to the first sealing surface relative to the sixth area, the distance from the fifth area to the first sealing surface is D5, and the distance from the sixth area to the second sealing surface is D6, D5=D6; wherein, the melting point of the fifth packaging layer is T5, and the melting point of the sixth packaging layer is T6, satisfying T5-T6≤5°C. Since D5=D6, the third isolation piece is located in the middle position. When sealing, the fifth packaging layer and the sixth packaging layer are subjected to approximately the same amount of heat, satisfying T5-T6≤5°C. This allows the fifth and sixth packaging layers to be well melted and well integrated with other parts during packaging, which is beneficial to improving the reliability of the packaging.

[0010] Optionally, the thickness of the first encapsulation layer is t1, and the thickness of the second encapsulation layer is t2, satisfying the following relationship: 1.5t2≤t1≤2t2. Thus, the thickness t1 of the first encapsulation layer is greater than the thickness t2 of the second encapsulation layer, thereby reducing the risk of excessive melting and extrusion of the first encapsulation layer due to the high temperature, thereby improving the sealing effect of the sealing area and further enhancing the packaging reliability of the electrochemical device.

[0011] Optionally, 15 μm ≤ t1 ≤ 200 μm. Optionally, 10 μm ≤ t2 ≤ 100 μm.

[0012] Optionally, the final melting temperature of the second encapsulation layer is Th2, satisfying the following: Th2 > T1. Thus, when the second encapsulation layer is completely melted, the first encapsulation layer has already begun to melt, thereby reducing the risk of excessive melting of the second encapsulation layer and resulting in a weak seal, thereby improving the encapsulation reliability of the electrochemical device.

[0013] Optionally, Th2-T2≥25° C. In this way, the second encapsulation layer has a wider melting range, reducing the risk of the second encapsulation layer being over-melted and extruded.

[0014] Optionally, the final melting temperature of the third encapsulation layer is Th3, the final melting temperature of the fourth encapsulation layer is Th4, and any one of the following conditions is met: (f) D4<D3;T4-T3≥7℃;Th3> T4;(g)D3<D4;T3-T4≥7℃;Th4> T3. In this way, during the packaging process, it is ensured that when one of the third and fourth packaging layers is completely melted, the other has already begun to melt. This allows the third and fourth packaging layers to be melted simultaneously, reducing the risk of excessive melting of one layer and resulting in a weak seal, thereby improving the packaging reliability of the electrochemical device.

[0015] Optionally, the first electrode assembly and the second electrode assembly are connected in series.

[0016] In a second aspect, the present application further provides an electronic device comprising the above-mentioned electrochemical device.

[0017] The beneficial effect of the present application is: in the electrochemical device provided by the present application, in the thickness direction of the sealing area, the distance between the first area of the first packaging layer and the first sealing surface is D1, and the distance between the second area of the second packaging layer and the second sealing surface is D2. When D1 is less than D2, by making the melting points of the first packaging layer and the second packaging layer different, and the melting point T1 of the first packaging layer is greater than the melting point T2 of the second packaging layer, when the sealing area is sealed, even if the temperature inside the sealing area away from the head is low, since the melting point of the second packaging layer is lower than the melting point of the first packaging layer, the second packaging layer can still be well melted, thereby reducing the occurrence of the phenomenon that the first packaging layer has been fully melted while the second packaging layer has not melted or has not melted sufficiently, which is beneficial to improving the sealing effect of the sealing area and improving the safety of the electrochemical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on the drawings.

[0019] Figure 1 is a schematic structural diagram of an electrochemical device according to one embodiment of the present application;

[0020] Figure 2 yes Figure 1 Schematic diagram after sectioning along line MM;

[0021] Figure 3 yes Figure 2 Enlarged view of part A in the middle;

[0022] Figure 4 It is a schematic diagram of the pole piece assembly having a wound structure;

[0023] Figure 5 It is a schematic diagram when the pole piece assembly is a laminated structure;

[0024] Figure 6 is a cross-sectional view of a portion of the structure of the electrochemical device of the present application;

[0025] Figure 7 yes Figure 6 Schematic diagram after removing the terminal ear;

[0026] Figure 8 yes Figure 7 Enlarged view of part B in the middle. DETAILED DESCRIPTION

[0027] In order to facilitate understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on the other element, or there can be one or more centered elements therebetween. When an element is described as "connected to" another element, it can be directly connected to the other element, or there can be one or more centered elements therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this specification are for illustrative purposes only.

[0028] Unless otherwise defined, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which this application belongs. The terms used in this specification and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" as used in this specification includes any and all combinations of one or more of the relevant listed items.

[0029] like Figure 1-2 As shown, an electrochemical device 100 provided in one embodiment of the present application includes a shell 10, an electrode assembly 20 and at least one separator. There are at least two electrode assemblies 20. The shell 10 is used to limit a closed space for accommodating the electrode assembly, and the separator is used to separate the internal space of the shell 10, thereby increasing the number of independent cavities inside the shell 10. More than one electrode assembly 20 can be arranged in each independent cavity, and the number of electrode assemblies 20 is set as needed. Among them, the electrochemical device 100 includes a sealing area 100a, which is the area where the shell 10 and the separator are used for sealing.

[0030] In some embodiments, please combine Figure 2-4The housing 10 includes a first housing 12 and a second housing 14. An isolating member is located between the first housing 12 and the second housing 14 to limit the enclosed space of the housing 10 into a plurality of independent cavities, each of which has an electrode assembly disposed therein. For example, when there is one isolating member, the enclosed space within the housing 10 is divided into two independent spaces, namely a first cavity 101 and a second cavity 102. The electrode assemblies disposed therein are the first electrode assembly 20a and the second electrode assembly 20b, respectively. When there are two isolating members, in addition to the first cavity 101 and the second cavity 102, the housing 10 also has a third cavity 103. The electrode assembly 20 disposed therein is the third electrode assembly 20c. When there are three isolating members, the space within the housing 10 also has a fourth cavity 104, and the fourth cavity 104 has a fourth electrode assembly 20d disposed therein.

[0031] The first shell 12 is provided with a first packaging portion 122 located in the sealing area 100a, and the first packaging portion 122 is provided with a first sealing surface 1222 facing away from the isolation member, and the first packaging portion 122 is used to be fixedly connected to a surface of the isolation member (which can be a hot melt connection or bonding), that is, the first shell 12 is fixedly connected to the isolation member at the sealing area 100a through the first packaging portion 122. The second shell 14 is provided with a second packaging portion 142 located in the sealing area 100a, and the second packaging portion 142 is provided with a second sealing surface 1422 facing away from the isolation member, and the second packaging portion 142 is used to be fixedly connected to a surface of the isolation member (which can be a hot melt connection or bonding), that is, the second shell 14 is fixedly connected to the isolation member at the sealing area 100a through the second packaging portion 142. Therefore, the first shell 12, the isolation member and the second shell 14 are fixedly connected at the sealing area 100a.

[0032] In order to facilitate understanding of the possible situations of the housing 10, Figure 1 Taking the shape of the shell 10 shown in the figure as an example, in one case, the first shell 12 and the second shell 14 are two independent parts, and the four edges of the surfaces of the first shell 12 and the second shell 14 used for sealing with the isolation member are sealed with the isolation member. In another case, the first shell 12 and the second shell 14 are two parts connected as one body, that is, the surfaces of the first shell 12 and the second shell 14 used for sealing with the isolation member have one side edge that is connected as one body, that is, the shell 10 can be formed by machining a groove into a whole plate and then folding it in half to form the first shell 12 and the second shell 14. In this embodiment, the shell 10 is composed of the first shell 12 and the second shell 14 that are independent of each other.

[0033] In some embodiments, please combine Figure 4 or Figure 5The electrode assembly 20 includes a pole piece assembly 21 and a pole lug 22 connected to the pole piece assembly 21. There are at least two pole lugs 22, and the polarities of the at least two pole lugs 22 are different. In some embodiments, the pole piece assembly 21 includes a first pole piece 211, a second pole piece 212, and a separator 213. The separator 213 is disposed between the first pole piece 211 and the second pole piece 212. The first pole piece 211 and the second pole piece 212 have opposite polarities. The separator 213 is used to reduce the risk of short circuit between the first pole piece 211 and the second pole piece 212.

[0034] In some embodiments, the multiple tabs 22 of the electrode assembly 20 may all extend from the first side end of the housing 10. Alternatively, they may extend from different side ends of the housing 10, i.e., at least two tabs 22 of the electrode assembly 20 extend from the first side end of the housing 10, and at least two tabs 22 extend from the second end of the housing. In some embodiments, the first side end of the housing 10 and the second side end of the housing 10 are opposite ends. In other embodiments, the first side end of the housing 10 and the second side end of the housing 10 are adjacent ends.

[0035] In some embodiments, as Figure 4 As shown, the pole piece assembly 21 may be a wound structure, that is, the first pole piece 211, the second pole piece 212 and the isolation film 213 are stacked and wound. Figure 5 As shown, the pole piece assembly 21 can be a laminated structure, in which case the number of the first pole piece 211, the second pole piece 212 and the isolation membrane 213 are all multiple, and the isolation membrane 213 is located between an adjacent first pole piece 211 and a second pole piece 212, and the first pole piece 211, the isolation membrane 213 and the second pole piece 212 are stacked along a direction, which is the thickness direction of the first pole piece 211, the isolation membrane 213 or the second pole piece 212.

[0036] It can be understood that the structures of the pole piece assemblies in mutually independent cavities can be the same, that is, the pole piece assemblies in different cavities can be of a winding structure or a laminated structure, which can be selected according to specific needs.

[0037] In some embodiments, the electrochemical device 100 further includes a tab glue 23, which is provided on two opposite surfaces of the tab. The tab glue 23 can be in a hot melt state during the packaging process, and the tab glue 23 can be better integrated with adjacent components (such as a shell or an insulator) to promote the packaging effect between the tab and the insulator or shell, improve the sealing of the tab extending position, and thereby improve the packaging reliability of the electrochemical device 100.

[0038] The electrochemical device 100 may include two electrode assemblies 20 or may include three or more electrode assemblies 20. When the electrochemical device 100 includes two electrode assemblies 20, namely a first electrode assembly 20a and a second electrode assembly 20b, the electrochemical device 100 has a separator, and the separator separates two independent cavities, namely the first cavity 101 and the second cavity 102 described above, the first electrode assembly 20a is disposed in the first cavity 101, and the second electrode assembly 20b is disposed in the second cavity 102 described above.

[0039] In some embodiments, the electrochemical device 100 may include one separator or multiple separators. When the electrochemical device 100 includes one separator, the one separator may separate the internal space of the housing 10 into two independent cavities. When the electrochemical device 100 includes multiple separators, the multiple separators may separate the internal space of the housing 10 into multiple independent cavities. For example, when the electrochemical device 100 specifically includes two separators, the two separators may separate the internal space of the housing 10 into three independent cavities; when the electrochemical device 100 includes three separators, the three separators separate the internal space of the housing 10 into four independent cavities.

[0040] The separator includes a sealing portion, and when the electrochemical device 100 is packaged, the portion of the separator located in the sealing portion is sealed with other components. That is, the portion of the separator in the sealing portion is fixedly connected to other components (which may be a hot-melt connection or bonding). When the electrochemical device 100 has only one separator, both side walls of the sealing portion of the separator are connected to the shell 10. When the electrochemical device 100 has two separators, one side wall of the sealing portion of one separator is connected to the other separator, and the other side wall is connected to the shell 10. When the number of separators is three or more, both side walls of the sealing portion of the separator located in the middle are connected to the other separators located on both sides of the separator.

[0041] In some embodiments, the isolation member includes a substrate layer and an encapsulation layer disposed on the surface of the substrate layer. The material compositions of the substrate layer and the encapsulation layer are as follows:

[0042] The material of the substrate layer includes at least one of metal, carbon material or a first polymer.

[0043] Metals include Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, I n, Zn, stainless steel and their combinations or alloys; the carbon material includes 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, polyamideimide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polypropylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), 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 of the above substances.

[0044] The material of the encapsulation layer includes a second polymer, which includes at least one of polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous α-olefin copolymer, or derivatives thereof.

[0045] The inventors of this application have discovered that when heat-sealing batteries connected in series or in parallel in the same bag, there is a difference in temperature between the two sides of the separator due to the influence of different thickness positions, and there is a risk of poor sealing on the side with lower temperature. After research, the inventors of this application have discovered that when the melting point of the packaging layer on the inner surface of the substrate layer is lowered, the packaging layers on both surfaces of the substrate layer can be well melted during packaging, and at the same time, the risk of excessive melting and extrusion of the packaging layer on the outer surface of the substrate layer can be reduced, thereby improving the packaging reliability of the electrochemical device 100. In order to facilitate a detailed understanding of the technical solution of this application, please refer to Figure 5 The following describes the structure of the separator in the electrochemical device 100 when the electrochemical device 100 includes different numbers of separators.

[0046] In some embodiments, please combine Figure 6-8The electrochemical device 100 includes a first isolation member 30, which includes a first substrate layer 301, a first encapsulation layer 302, and a second encapsulation layer 303. The first encapsulation layer 302 is provided on the first surface 301a of the first substrate layer 301, and the second encapsulation layer 303 is provided on the second surface 301b of the first substrate layer 301. The first surface 301a and the second surface 301b are arranged opposite to each other. The melting point of the first encapsulation layer 302 is T1, and the melting point of the second encapsulation layer 303 is T2. The first isolation member 30 includes a first sealing portion 304 located in the sealing area 100a, the first surface 301a includes a first region 301a1 located in the first sealing portion 304, and the second surface 301b includes a second region 301b1 located in the first sealing portion 304. Along the thickness direction Z of the sealed area 100a, the first region 301a1 is adjacent to the first sealing surface 1222 relative to the second region 301b1. The distance between the first region 301a1 and the first sealing surface 1222 is D1, and the distance between the second region 301b1 and the second sealing surface 1422 is D2. D1 < D2, satisfying T1 > T2. The melting point refers to the temperature at which a meltable component begins to melt from a solid state to a liquid state when tested using a microscopic melting point meter.

[0047] Thus, in the thickness direction Z of the sealing area 100a, when encapsulated by the heat seal head, the melting point of the first encapsulation layer 302 closer to the heat seal head is relatively higher than the melting point of the second encapsulation layer 303 farther from the heat seal head. Even when the temperature inside the sealing area farther from the heat seal head is lower, the second encapsulation layer 303 can still be melted well, reducing the occurrence of the first encapsulation layer 302 being fully melted while the second encapsulation layer 303 is not melted or is not fully melted. This helps improve the sealing effect on the lower temperature side of the first separator 30, thereby improving the packaging reliability of the electrochemical device 100. In some embodiments, T1-T2 ≥ 7°C. In some embodiments, T1-T2 ≤ 40°C.

[0048] In some embodiments, the thickness of the first encapsulation layer 302 is t1, and the thickness of the second encapsulation layer 303 is t2, satisfying: 1.5t2≤t1≤2t2.

[0049] When the above conditions are met, the thickness t1 of the first encapsulation layer 302 will be greater than the thickness t2 of the second encapsulation layer 303 , thereby reducing the risk of the first encapsulation layer 302 being excessively melted and extruded due to high temperature, thereby improving the packaging reliability of the electrochemical device 100 .

[0050] In some embodiments, 15 μm ≤ t1 ≤ 200 μm. In some embodiments, 10 μm ≤ t2 ≤ 100 μm.

[0051] In some embodiments, the final melting temperature of the second encapsulation layer is Th2, satisfying the following: Th2 > T1. The final melting temperature refers to the temperature at which a meltable component completely melts from a solid state to a liquid state when tested using a micro melting point meter. As a result, when the second encapsulation layer 303 is completely melted, the first encapsulation layer 302 has already begun to melt, reducing the risk of excessive melting of the second encapsulation layer 303 and resulting in a weak seal, thereby improving the packaging reliability of the electrochemical device 100.

[0052] In some embodiments, Th2-T2≥25° C. In this way, the second encapsulation layer 303 has a wider melting range, which reduces the risk of the second encapsulation layer 303 being excessively melted and squeezed out.

[0053] In some embodiments, please combine again Figure 6-Figure 8 In addition to the above-mentioned first isolation member 30, the electrochemical device 100 also includes a second isolation member 40, which is arranged between the first isolation member 30 and the second shell 14. The second isolation member 40 includes a second substrate layer 401, a third packaging layer 402 and a fourth packaging layer 403. The third packaging layer 402 is arranged on the third surface 401a of the second substrate layer 401, and the fourth packaging layer 403 is arranged on the fourth surface 401b of the second substrate layer 401. The third surface 401a and the fourth surface 401b are arranged opposite to each other. The melting point of the third packaging layer 402 is T3, and the melting point of the fourth packaging layer 403 is T4. Among them, the second isolation member 40 includes a second sealing portion 404 located in the sealing area 100a, the third surface 401a includes a third area 401a1 located in the second sealing portion 404, and the fourth surface 401b includes a fourth area 401b1 located in the second sealing portion 404. Along the thickness direction Z of the sealing area 100a, the third area 401a1 is adjacent to the second sealing surface 1422 relative to the fourth area 401b1, the distance between the third area 401a1 and the second sealing surface 1422 is D3, and the distance from the fourth area 401b1 to the first sealing surface 1222 is D4, D3<D4, satisfying T3>T4.

[0054] Thus, during encapsulation using a heat seal head, the melting point of the third encapsulation layer 402, which is closer to the encapsulation head, is relatively higher than the melting point of the fourth encapsulation layer 403, which is farther from the encapsulation head. Both the third encapsulation layer 402 and the fourth encapsulation layer 403 can be fully melted during heat sealing, thereby better integrating with other parts, further improving the sealing effect of the sealing area 100a and enhancing the packaging reliability of the electrochemical device 100. In some embodiments, T3-T4 ≥ 7°C is satisfied. In some embodiments, T3-T4 ≤ 40°C is satisfied.

[0055] In some embodiments, the final melting temperature of the third encapsulation layer 402 is Th3, and the final melting temperature of the fourth encapsulation layer 403 is Th4, satisfying any one of the following conditions:

[0056] (1)D4<D3;T4-T3≥7℃;Th3> When the above conditions are met, the fourth packaging layer begins to melt before the third packaging layer 402 is completely melted, so that both are in a hot melt state at the same time, reducing the risk of one of them being over-melted and causing a loose seal, which is beneficial to improving the packaging reliability of the sealing area 100a.

[0057] (2)D3<D4;T3-T4≥7℃;Th4> When the above conditions are met, the third packaging layer begins to melt before the fourth packaging layer 403 is completely melted, so that both are in a hot melt state at the same time, reducing the risk of one of them being over-melted and causing an unreliable seal, which is beneficial to improving the packaging reliability of the sealing area 100a.

[0058] In some embodiments, the thickness of the third encapsulation layer 402 is t3, and the thickness of the fourth encapsulation layer 403 is t4, satisfying the following relationship: 1.5t4≤t3≤2t4. When these conditions are met, the thickness t3 of the third encapsulation layer 402 is greater than the thickness t4 of the fourth encapsulation layer 403, thereby reducing the risk of excessive melting and extrusion of the third encapsulation layer 402 due to high temperatures, thereby improving the packaging reliability of the electrochemical device 100.

[0059] In some embodiments, 15 μm ≤ t3 ≤ 200 μm. In some embodiments, 10 μm ≤ t4 ≤ 100 μm.

[0060] In some embodiments, please combine Figure 6-8As shown, in addition to the first and second separators 30 and 40 described above, the electrochemical device 100 also includes a third separator 50, which is located between the first housing 12 and the second housing 14. In this embodiment, the third separator 50 is located between the first and second separators 30 and 40. The third separator 50 includes a third substrate layer 501, a fifth encapsulation layer 502, and a sixth encapsulation layer 503. The fifth encapsulation layer 502 is disposed on the fifth surface 501a of the third substrate layer 501, and the sixth encapsulation layer 503 is disposed on the sixth surface 501b of the third substrate layer 501. The fifth and sixth surfaces 501a and 501b are disposed opposite each other. The melting point of the fifth encapsulation layer 502 is T5, and the melting point of the sixth encapsulation layer 503 is T6. The third spacer 50 includes a third sealing portion 504 located in the sealing area 100a. The fifth surface 501a includes a fifth region 501a1 located in the third sealing portion 504. The sixth surface 501b includes a sixth region 501b1 located in the third sealing portion 504. Along the thickness direction Z of the sealing area 100a, the fifth region 501a1 is adjacent to the first sealing surface 1222 relative to the sixth region 501b1. The distance between the fifth region 501a1 and the first sealing surface 1222 is D5, and the distance between the sixth region 501b1 and the second sealing surface 1422 is D6, where D5 = D6. T5 - T6 ≤ 5°C is satisfied.

[0061] Similarly, in the thickness direction Z of the sealing area 100a, the distance from the fifth region 501a1 to the first sealing surface 1222 is the same as the distance from the sixth region 501b1 to the second sealing surface 1422. At this time, the third isolation member 50 is in the middle position of the sealing area 100a, and the temperature environment of the fifth packaging layer 502 and the sixth packaging layer 503 during packaging is the same or approximately the same.

[0062] It can be understood that the above respectively introduces the cases where the number of isolators is one, two, and three, and the same rule applies to a larger number of isolators. For example, when the number of isolators is n, n is an even number, and n ≥ 2, taking n = 4 as an example, along the thickness direction Z of the sealing area 100a, for the two isolators that are closer to the first sealing surface 1222, the encapsulation layer close to the first sealing surface 1222 in each isolator is a high melting point encapsulation layer, and the encapsulation layer away from the first sealing surface 1222 in each isolator is a low melting point encapsulation layer. For the two isolators that are closer to the second sealing surface 1422, the encapsulation layer close to the second sealing surface 1422 in each isolator is a high melting point encapsulation layer, and the encapsulation layer away from the second sealing surface 1422 in each isolator is a low melting point encapsulation layer. When the number of isolators is an odd number and is greater than or equal to 5, the distribution of the encapsulation layer of the isolators is the same as when the number of isolators is three. The middle isolator adopts the distribution of the third isolator 50. Along the thickness direction of the sealing area 100a, the isolator on one side of the middle isolator adopts the distribution of the above-mentioned first isolator, and the isolator on the other side of the middle isolator adopts the distribution of the above-mentioned second isolator.

[0063] Example 1

[0064] Preparation of lithium-ion batteries

[0065] (1) Preparation of negative electrode sheet: Mix the negative electrode active materials artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) in a weight ratio of 96:1.5:2.5, add deionized water, and prepare a slurry with a solid content of 70wt%, and stir evenly. The slurry is evenly coated on one surface of the negative electrode current collector copper foil and dried to obtain a negative electrode sheet coated with a negative electrode active material layer on one side. Repeat the above steps on the other surface of the negative electrode current collector copper foil to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. After cold pressing, the negative electrode sheet is cut into a size of 41mm×61mm for use.

[0066] (2) Preparation of positive electrode sheet: The positive electrode active material lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added to prepare a slurry with a solid content of 75wt%, and stirred evenly. The slurry is evenly coated on one surface of the positive electrode current collector aluminum foil and dried to obtain a positive electrode sheet coated with a positive electrode active material layer on one side. Repeat the above steps on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. After cold pressing, the positive electrode sheet is cut into a size of 38mm×58mm for use.

[0067] (3) Preparation of electrolyte: In a dry argon atmosphere, organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed in a mass ratio of EC:EMC:DEC = 30:50:20, and then lithium salt lithium hexafluorophosphate (LiPF6) was 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.

[0068] (4) Preparation of the first electrode assembly and the second electrode assembly: The separator, negative electrode sheet, separator, and positive electrode sheet are stacked in sequence to form a laminate structure, and the four corners of the entire laminate structure are fixed to form a plate assembly. Each electrode assembly includes a positive electrode tab and a negative electrode tab. The positive electrode tab is aluminum (Al) and the negative electrode tab is nickel (Ni). The two tabs are arranged side by side. The separator is a polyethylene (PE) film with a thickness of 15 μm.

[0069] (5) Preparation of the isolation member: The first encapsulation layer material polypropylene (PP, melting point 147°C) is uniformly dispersed in the dispersant N-methylpyrrolidone (NMP) to prepare a first encapsulation layer PP suspension; the second encapsulation layer material polypropylene (PP, melting point 140°C) is uniformly dispersed in the dispersant N-methylpyrrolidone (NMP) to prepare a second encapsulation layer PP suspension; using a coating machine, the first encapsulation layer PP suspension and the second encapsulation layer PP suspension are coated on both sides of the aluminum layer with a thickness of 50 μm respectively; then the aluminum layer is dried at 130°C, wherein the thickness t1 of the first encapsulation layer is 150 μm, and the thickness t2 of the second encapsulation layer is 100 μm.

[0070] (6) Assembly of the electrode assembly: Place the first aluminum-plastic film (thickness of 150 μm) formed by punching a pit in an assembly fixture with the pit facing upward, place the first electrode assembly in the pit, and set the tab glue on the tab surface of the first electrode assembly, then place the first separator on the first electrode assembly, wherein the first packaging layer in the first separator is adjacent to the first aluminum-plastic film and the second packaging layer is away from the first aluminum-plastic film, so that the edges are aligned, and apply external force to press to obtain an assembled semi-finished product 1. Place the assembled semi-finished product 1 in an assembly fixture with the second packaging layer of the first separator facing upward, place the second electrode assembly on the first separator, so that the edges are aligned, apply external force to press, and set the tab glue on the tab surface of the second electrode assembly, then place the second separator on the second electrode assembly, wherein the second packaging layer in the second separator is adjacent to the first aluminum-plastic film and the first packaging layer is away from the first aluminum-plastic film, so that the edges are aligned, and apply external force to press to obtain an assembled semi-finished product 2. Place the semi-finished assembly 2 in an assembly fixture with the first packaging layer of the second separator facing upward. Place the third electrode assembly on the second separator. Then, place another punched and formed second aluminum-plastic film with the pitted surface facing downward over the third electrode assembly. Apply lug glue to the lug surfaces of the third electrode assembly. Lead the positive and negative lugs of the first, second, and third electrode assemblies out of the aluminum-plastic film and perform top and side sealing using hot pressing to complete the assembled electrode assembly.

[0071] (7) Liquid injection packaging: Electrolyte is injected into each cavity separately, and then sealed after hot pressing, formation, and degassing.

[0072] (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, and the negative electrode tab of the second electrode assembly and the positive electrode tab of the third electrode assembly are welded together by laser welding to achieve series connection, and the lithium-ion battery assembly is completed.

[0073] Examples 2-6 and Comparative Examples

[0074] The difference from Example 1 is that the first encapsulation layer and the second encapsulation layer are respectively made of polypropylene having the corresponding melting point and other characteristics and thickness in Table 1.

[0075] Table 1 Test table of the impact of melting point and thickness of different packaging layers on packaging effect

[0076]

[0077]

[0078] The test results obtained in Examples 1-6 and the comparative example in Table 1 were obtained by the following method: using a multifunctional peeling device, first clamping the first and second separators on one side of the packaging area, and then pulling them apart to separate the packaging areas of the first and second separators, and observing the bonding positions of the separators after separation. If the color of the bonding positions after separation is milky white, it indicates that the separators are well fused; if there is a local milky white color that is not obvious, it indicates that the separators are poorly fused. From the comparison of Examples 1-6 and the comparative example in Table 1, it can be seen that when T1-T2 ≥ 7°C, the sealing area 100a of the electrochemical device 100 is well fused, indicating that when the melting point of the first packaging layer 302 is greater than the melting point of the second packaging layer 303, the second packaging layer 303 can be well melted, thereby improving the packaging reliability and safety of the electrochemical device 100.

[0079] The present application also provides an electronic device, which includes the electrochemical device provided in the present application. The electronic device of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, the electronic device includes but is not limited to a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery and a lithium ion capacitor, etc.

[0080] It should be noted that the preferred embodiments of the present application are given in the specification and drawings of this application. However, the present application can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not intended to be additional limitations on the content of this application. The purpose of providing these embodiments is to make the understanding of the disclosure of this application more thorough and comprehensive. In addition, the above-mentioned technical features can be combined with each other to form various embodiments not listed above, which are all considered to be within the scope of the description of this application; further, it is obvious to those skilled in the art that improvements or changes can be made based on the above description, and all such improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. An electrochemical device, characterized in that Comprising: A first housing and a second housing; A first separator located between the first housing and the second housing. An electrochemical device has a first cavity between the first housing and the first separator, and a second cavity between the second housing and the first separator. The first separator includes a first base layer, a first encapsulation layer, and a second encapsulation layer. The first encapsulation layer is provided on a first surface of the first base layer, the second encapsulation layer is provided on a second surface of the first base layer, and the first surface and the second surface are opposite to each other; A first electrode assembly and a second electrode assembly. The first electrode assembly is received in the first cavity; the second electrode assembly is received in the second cavity; The electrochemical device includes a sealing area where the first housing, the first separator, and the second housing are connected. The first housing includes a first sealing surface in the sealing area facing away from the first separator, the second housing includes a second sealing surface in the sealing area facing away from the first separator, the first separator includes a first sealing portion in the sealing area, the first surface includes a first area in the first sealing portion, and the second surface includes a second area in the first sealing portion; along the thickness direction of the sealing area, the first area is adjacent to the first sealing surface relative to the second area, the distance from the first area to the first sealing surface is D1, the distance from the second area to the second sealing surface is D2, and D1 < D2; wherein, the melting point of the first encapsulation layer is T1, the melting point of the second encapsulation layer is T2, satisfying T1 > T2 and T1 - T2 ≥ 7°C.

2. The electrochemical device according to claim 1, wherein Satisfying T1 - T2 ≤ 40°C.

3. The electrochemical device according to claim 1, wherein Further comprising a second separator located between the first separator and the second housing. The second separator includes a second base layer, a third encapsulation layer, and a fourth encapsulation layer. The third encapsulation layer is provided on a third surface of the second base layer, the fourth encapsulation layer is provided on a fourth surface of the second base layer, and the third surface and the fourth surface are opposite to each other; The second separator includes a second sealing portion in the sealing area, the third surface includes a third area in the second sealing portion, and the fourth surface includes a fourth area in the second sealing portion; along the thickness direction of the sealing area, the fourth area is adjacent to the second sealing surface relative to the third area, the distance from the third area to the first sealing surface is D3, the distance from the fourth area to the second sealing surface is D4; wherein, the melting point of the third encapsulation layer is T3, the melting point of the fourth encapsulation layer is T4, satisfying any one of the following conditions: (1) D4 < D3; T4 - T3 ≥ 7°C; (2) D3 < D4; T3 - T4 ≥ 7°C.

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

5. The electrochemical device according to claim 3, characterized in that Further comprising a third separator The third isolation member is located between the first shell and the second shell, and includes a third substrate layer, a fifth packaging layer, and a sixth packaging layer. The fifth packaging layer is provided on the fifth surface of the third substrate layer, and the sixth packaging layer is provided on the sixth surface of the third substrate layer. The fifth surface is opposite to the sixth surface. The third isolation member includes a third sealing portion located in the sealing area, the fifth surface includes a fifth area located in the third sealing portion, and the sixth surface includes a sixth area located in the third sealing portion; along the thickness direction of the sealing area, the fifth area is adjacent to the first sealing surface relative to the sixth area, the distance from the fifth area to the first sealing surface is D5, and the distance from the sixth area to the second sealing surface is D6, D5=D6; wherein, the melting point of the fifth encapsulation layer is T5, and the melting point of the sixth encapsulation layer is T6, satisfying T5-T6≤5°C.

6. The electrochemical device according to claim 1, wherein The thickness of the first encapsulation layer is t1, the thickness of the second encapsulation layer is t2, and at least one of the following conditions is satisfied: (a) 1.5t2≤t1≤2t2; (b) 15 μm ≤ t1 ≤ 200 μm; (c)10μm≤t2≤100μm.

7. The electrochemical device according to claim 1, wherein The final melting temperature of the second encapsulation layer is Th2, which satisfies at least one of the following conditions: (d) Th2>T1; (e)Th2-T2≥25℃.

8. The electrochemical device according to claim 3, characterized in that The final melting temperature of the third encapsulation layer is Th3, and the final melting temperature of the fourth encapsulation layer is Th4, satisfying any one of the following conditions: (f)D4<D3;T4-T3≥7℃;Th3> T4; (g)D3<D4;T3-T4≥7℃;Th4> T3.

9. The electrochemical device according to claim 7, characterized in that The first electrode assembly and the second electrode assembly are connected in series.

10. An electronic device, characterized in that: The electrochemical device comprises the electrochemical device according to any one of claims 1 to 9.

Images