WO2023197159A1

WO2023197159A1 - Electrochemical device and electronic device

Info

Publication number: WO2023197159A1
Application number: PCT/CN2022/086386
Authority: WO
Inventors: 宋小芳; 郭培培
Original assignee: 宁德新能源科技有限公司
Priority date: 2022-04-12
Filing date: 2022-04-12
Publication date: 2023-10-19
Also published as: CN116802914A

Abstract

Disclosed in the present application are an electrochemical device and an electronic device. The electrochemical device comprises a first housing provided with a first sealing surface, a second housing provided with a second sealing surface, and a first isolation member, wherein the first isolation member is arranged between the first housing and the second housing, and a first cavity containing a first electrode assembly and a second cavity containing a second electrode assembly are formed. The first isolation member comprises a base material layer, a first packaging layer arranged on a first surface of the base material layer, and a second packaging layer arranged on a second surface of the base material layer. The first isolation member further comprises a first sealing portion located in a sealing region, wherein the first surface comprises a first region located in the first sealing portion, and the second surface comprises a second region located in the first sealing portion; and in the thickness direction of the sealing region, the distance D₁ between the first sealing surface and the first region is less than the distance D₂ between the second sealing surface and the second region, and the melting point T₁ of the first packaging layer is greater than the melting point T₂ of the second packaging layer. Therefore, the sealing effect of the sealing region can be improved.

Description

An electrochemical device and electronic equipment

Technical field

The present application relates to the field of battery technology, and in particular to an electrochemical device and electronic equipment.

Background technique

Currently, batteries are widely used in electronic products such as drones, mobile phones, tablets, and laptops. Since in some application scenarios, a single battery cell cannot achieve the desired output power; therefore, multiple battery cells are usually connected in series, parallel, or mixed, so that the multiple battery cells work together to achieve Desired power output. However, although connecting multiple battery cells in series, parallel or mixed connection can increase the output power, the energy density of the entire battery pack is low. Therefore, the design of series/parallel batteries in the same bag is proposed. The series/parallel battery in the same bag includes a casing and multiple electrode assemblies arranged in the same casing. The series-connected electrode assemblies need to be separated by separators to avoid high voltage. The electrolyte decomposes under voltage. Parallel electrode assemblies are separated by separators to avoid mutual interference. The tabs of multiple electrode assemblies extend from the side of the casing for connection outside the casing.

Contents of the invention

The inventor of this application found through research that when series/parallel batteries in the same bag are heat-sealed and packaged, the temperatures on both sides of the separator are different due to the influence of different thickness positions, and there is a risk of poor sealing on the side with a lower temperature.

In view of the above technical problems, this application provides an electrochemical device and electronic equipment to improve the safety of the electrochemical device.

In order to solve the above technical problems, the first aspect of this application: provides 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 is provided with a first cavity between the first housing and the first isolation member, and the electrochemical device is provided between the second housing and the first isolation member. There is a second cavity between the parts. The first electrode assembly is received in the first cavity; the second electrode assembly is received in the second cavity. The first isolator includes a first base material layer, a first encapsulation layer and a second encapsulation layer. The first encapsulation layer is provided on the first surface of the first base material layer, and the second encapsulation layer Disposed on the second surface of the first base material layer, the first surface is opposite to the second surface. The electrochemical device includes a sealing area, the first housing, the first isolator and the second housing are connected in the sealing area, and the first housing includes a seal located in the sealing area away from the The first sealing surface of the first isolator, the second housing includes a second sealing surface located in the sealing area and facing away from the first isolating member, the first isolating component includes a third sealing surface located in the sealing area. A sealing part, the first surface includes a first area located in the first sealing part, the second surface includes a second area located in the first sealing part; along the thickness direction of the sealing area, the 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 D _{1 , and the distance from the second area to the second sealing surface is D 1} . The distance between the surfaces is D ₂ , D ₁ <D ₂ ; wherein, the melting point of the first encapsulation layer is T ₁ , the melting point of the second encapsulation layer is T ₂ , and T ₁ >T ₂ is satisfied.

In this way, when the sealing area is sealed, since the melting point of the second encapsulation layer is lower than the melting point of the first encapsulation layer, even when the temperature inside the sealing area away from the sealing head is low, the second encapsulation layer can still melt well. , reducing the occurrence of the phenomenon that the first encapsulation layer is fully melted but the second encapsulation layer is not melted or is insufficiently melted, which is conducive to improving the sealing effect on the lower temperature side of the first isolator, thereby improving the safety of the electrochemical device. Further, T ₁ -T ₂ ≥7°C is satisfied. Further, T ₁ -T ₂ ≤40°C is satisfied.

Optionally, the electrochemical device further includes a second isolator located between the first isolator and the second housing, the second isolator including a second base material layer, A third encapsulation layer and a fourth encapsulation layer, the third encapsulation layer is provided on the third surface of the second base material layer, and the fourth encapsulation layer is provided on the fourth surface of the second base material layer, The third surface is opposite to the fourth surface; the second isolator includes a second sealing portion located in the sealing area, and the third surface includes a third area located in the second sealing portion, so The fourth surface includes a fourth area located 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, and the The distance from the third area to the first sealing surface is D ₃ , and the distance from the fourth area to the second sealing surface is D ₄ ; wherein, the melting point of the third encapsulation layer is T ₃ , and the distance from the fourth area to the second sealing surface is D 4 . The melting point of the fourth encapsulation layer is T ₄ , which satisfies any of the following conditions: (1) D ₄ <D ₃ ; T ₄ >T ₃ ; (2) D ₃ <D ₄ ; T ₃ >T ₄ .

When the above conditions are met, both the third packaging layer and the fourth packaging layer can be well heat-melted during the packaging process, reducing the risk that only one of the third packaging layer and the fourth packaging layer is in a fully heat-melted state. The risk of the other being in an unheated or insufficiently hot-melted state is conducive to improving the sealing effect of the sealing area and further improving the safety of the electrochemical device. Further, T ₄ -T ₃ ≥7°C or T ₃ -T ₄ ≥7°C is satisfied. Further, T ₄ -T ₃ ≤40°C or T ₃ -T ₄ ≤40°C is satisfied.

Optionally, the electrochemical device further includes a third isolator located between the first shell and the second shell, the third isolator including a third base material layer, a fifth encapsulation layer and a sixth encapsulation layer, the fifth encapsulation layer is provided on the fifth surface of the third base material layer, and the sixth encapsulation layer is provided on the sixth surface of the third base material layer, The fifth surface is opposite to the sixth surface; the third isolator includes a third sealing portion located in the sealing area, and the fifth surface includes a fifth area located in the third sealing portion, so 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, and the The distance from the fifth area to the first sealing surface is D ₅ , and the distance from the sixth area to the second sealing surface is D ₆ , D ₅ =D ₆ ; wherein, the melting point of the fifth encapsulation layer is T ₅ , and the melting point of the sixth encapsulation layer is T ₆ , which satisfies T ₅ -T ₆ ≤5°C. Since D ₅ =D ₆ , the third isolator is located in the middle. During sealing, the fifth packaging layer and the sixth packaging layer receive approximately the same heat, which satisfies T ₅ -T ₆ ≤5°C, so that the fifth and sixth packages are The layers can be well thermally melted and can be well integrated with other parts during packaging, which is beneficial to improving the reliability of the packaging.

Optionally, the thickness of the first encapsulation layer is t ₁ and the thickness of the second encapsulation layer is t ₂ , satisfying: 1.5t ₂ ≤ _{t 1} ≤ 2t ₂ . In this way, the thickness t ₁ of the first encapsulation layer will be greater than the thickness t ₂ of the second encapsulation layer, thereby reducing the risk of excessive melting and extrusion of the first encapsulation layer due to high temperature, which is beneficial to improving the sealing effect of the sealing area. , thereby improving the packaging reliability of electrochemical devices.

Optional, 15μm≤t ₁ ≤200μm. Optional, _{10μm≤t2≤100μm} .

Optionally, the final melting temperature of the second encapsulation layer is Th ₂ , which satisfies: Th ₂ >T ₁ . Therefore, when the second encapsulation is completely melted, the first encapsulation layer has already begun to melt, thereby reducing the risk of the second encapsulation layer being excessively melted and causing the seal to become unreliable, thereby improving the packaging reliability of the electrochemical device.

Optional, Th ₂ -T ₂ ≥25℃. In this way, the second encapsulation layer has a wider melting range, which reduces the risk of excessive melting and extrusion of the second encapsulation layer.

Optionally, the final melting temperature of the third encapsulation layer is Th ₃ and the final melting temperature of the fourth encapsulation layer is Th ₄ , any one of the conditions is met: (f) D ₄ <D ₃ ; T ₄ -T ₃ ≥7℃; Th ₃ >T ₄ ; (g)D ₃ <D ₄ ; T ₃ -T ₄ ≥7℃; Th ₄ >T ₃ . In this way, during the encapsulation process, it can be ensured that when one of the third encapsulation layer and the fourth encapsulation layer is completely melted, the other has begun to melt, so that the third encapsulation layer and the fourth encapsulation layer can be thermally melted at the same time. , reducing the risk of excessive melting of one of them, resulting in an unstable seal, thereby improving the packaging reliability of electrochemical devices.

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

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

The beneficial effects of this application are: for the electrochemical device provided by this application, in the thickness direction of the sealing area, the distance between the first area of the first encapsulation layer and the first sealing surface is D ₁ , and the distance between the first area of the first encapsulation layer and the first sealing surface is D 1 . The distance between the second area and the second sealing surface is D ₂ . When D ₁ <D ₂ , there is a difference in the melting points between the first encapsulation layer and the second encapsulation layer, and the melting point T ₁ of the first encapsulation layer is greater than the melting point T ₂ of the second encapsulation layer, so that when the sealing area is sealed, even if the temperature inside the sealing area away from the sealing head is low, since the melting point of the second encapsulation layer is lower than the melting point of the first encapsulation layer, the second encapsulation layer The second encapsulation layer can still be melted well, which reduces the occurrence of the phenomenon that the first encapsulation layer is fully melted but the second encapsulation layer is not melted or is insufficiently melted, which is conducive to improving the sealing effect of the sealing area and improving the safety of the electrochemical device.

Description of the drawings

In order to explain the technical solutions of the embodiments of the present application more clearly, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. Those of ordinary skill in the art can also obtain other drawings based on the drawings.

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

Figure 2 is a schematic diagram cut along line MM in Figure 1;

Figure 3 is an enlarged view of part A in Figure 2;

Figure 4 is a schematic diagram of the pole piece assembly in a wound structure;

Figure 5 is a schematic diagram when the pole piece assembly is a laminated structure;

Figure 6 is a cross-sectional view of a partial structure of the electrochemical device of the present application;

Figure 7 is a schematic diagram of Figure 6 after removing the pole lug;

FIG. 8 is an enlarged view of part B in FIG. 7 .

Detailed ways

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

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by a person skilled in the technical field belonging to this application. The terms used in the description of this application are only for the purpose of describing specific embodiments and are not used to limit this application. As used in this specification, the term "and/or" includes any and all combinations of one or more of the associated listed items.

As shown in Figures 1-2, an electrochemical device 100 provided by one embodiment of the present application includes a housing 10, an electrode assembly 20 and at least one isolator. The number of electrode assemblies 20 is at least two. The housing 10 is used to limit a closed space for accommodating the electrode assembly, and the partition is used to separate the internal space of the housing 10 , thereby increasing the number of independent cavities inside the housing 10 . More than one electrode assembly 20 can be disposed in each independent cavity, and the number of electrode assemblies 20 is set as needed. The electrochemical device 100 includes a sealing area 100a. The sealing area 100a is the area where the housing 10 and the separator used for sealing are located.

In some embodiments, please refer to FIGS. 2-4 , the housing 10 includes a first housing 12 and a second housing 14 , and an isolation member is located between the first housing 12 and the second housing 14 to separate the housings. The enclosed space of 10 limits a plurality of independent cavities, and electrode assemblies are correspondingly arranged in each independent cavity. For example, when there is a separator, the enclosed space in the housing 10 is divided into two independent spaces, namely the first cavity 101 and the second cavity 102. The two cavities have corresponding electrode assemblies. They are the first electrode assembly 20a and the second electrode assembly 20b respectively. When there are two isolators, the housing 10 has a third cavity 103 in addition to the first cavity 101 and the second cavity 102. The electrode assembly 20 provided in the third cavity 103 corresponds to the third electrode assembly. 20c. When there are three isolators, the space within the housing 10 also has a fourth cavity 104, and a fourth electrode assembly 20d is correspondingly provided in the fourth cavity 104.

The first housing 12 is provided with a first sealing portion 122 located in the sealing area 100a. The first sealing portion 122 is provided with a first sealing surface 1222 facing away from the isolator. The first sealing portion 122 is used for fixing with a surface of the isolator. Connection (which may be hot melt connection or bonding) means that the first housing 12 is fixedly connected to the isolator through the first packaging part 122 at the sealing area 100a. The second housing 14 is provided with a second sealing portion 142 located in the sealing area 100a. The second sealing portion 142 is provided with a second sealing surface 1422 facing away from the isolator. The second sealing portion 142 is used to be fixed to a surface of the isolator. Connection (which may be hot melt connection or bonding), that is, the second housing 14 is fixedly connected to the isolator through the second packaging part 142 at the sealing area 100a. Therefore, the first housing 12, the isolation member and the second housing 14 are fixedly connected at the sealing area 100a.

In order to facilitate understanding of possible situations of the housing 10, the shape of the housing 10 shown in FIG. 1 is taken as an example. In one case, the first housing 12 and the second housing 14 are two independent parts. The surfaces of both the first housing 12 and the second housing 14 that are used for sealing with the isolation member are sealed with the isolation member. In another case, the first housing 12 and the second housing 14 are two parts integrally connected, that is, the surfaces of the first housing 12 and the second housing 14 used for sealing with the isolation member have one side. The edges are integrally connected, that is, the housing 10 can be formed by processing a groove into a whole plate and then folding it in half to form the first housing 12 and the second housing 14 . In this embodiment, the housing 10 is composed of a first housing 12 and a second housing 14 that are independent of each other.

In some embodiments, please refer to FIG. 4 or FIG. 5 , the electrode assembly 20 includes a pole piece assembly 21 and a pole tab 22 connected to the pole piece assembly 21 . The number of pole tabs 22 is at least two. At least two pole tabs 22 The polarity is different between them. In some embodiments, the pole piece assembly 21 includes a first pole piece 211, a second pole piece 212, and an isolation film 213. The isolation film 213 is disposed between the first pole piece 211 and the second pole piece 212. The first pole piece The polarity of 211 is opposite to that of the second pole piece 212, and the isolation film 213 is used to reduce the risk of short circuit between the first pole piece 211 and the second pole piece 212.

In some embodiments, the plurality of tabs 22 of the electrode assembly 20 may all protrude from the first side end of the housing 10 . It may also extend from different side ends of the housing 10 , that is, 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 10 . Reach out. 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 opposite ends. The second side ends are two adjacent ends.

In some embodiments, as shown in FIG. 4 , the pole piece assembly 21 may be a rolled structure, that is, the first pole piece 211 , the second pole piece 212 and the isolation film 213 are stacked and rolled. In some embodiments, as shown in FIG. 5 , the pole piece assembly 21 may have a laminated structure. In this case, the number of the first pole piece 211 , the second pole piece 212 and the isolation film 213 is multiple. The isolation film 213 is located at Between an adjacent first pole piece 211 and a second pole piece 212, the first pole piece 211, the isolation film 213 and the second pole piece 212 are stacked along one direction, which direction is the first pole piece 211, the isolation film 213 and the second pole piece 212. The thickness direction of the isolation film 213 or the second pole piece 212.

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 all have a winding structure or a laminated structure, which is selected according to needs.

In some embodiments, the electrochemical device 100 further includes tab glue 23. The tab glue 23 is provided on two opposite surfaces of the tab. The tab glue 23 can be in a hot melt state during the packaging process. The tab glue 23 can be in a hot-melt state during the packaging process. 23 can be better integrated with adjacent components (such as casings or separators) to promote the encapsulation effect between the tabs and separators or casings, improve the sealing of the protruding locations of the tabs, and thereby improve electrochemical Package reliability of device 100.

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 the first electrode assembly 20a and the second electrode assembly 20b, the electrochemical device 100 has a separator, and the separator separates two independent cavities. , that is, the above-mentioned first cavity 101 and the second cavity 102, the first electrode assembly 20a is disposed in the first cavity 101, and the second electrode assembly 20b is disposed in the above-mentioned second cavity 102.

In some embodiments, the electrochemical device 100 may include one isolator or may include multiple isolators. When the electrochemical device 100 includes one isolator, one isolator may separate the internal space of the housing 10 into two independent cavity. When the electrochemical device 100 includes multiple isolators, the multiple isolators may separate the internal space of the housing 10 into multiple independent cavities. For example, when the electrochemical device 100 specifically includes two isolators, two isolators The components can separate the internal space of the housing 10 into three independent cavities; when the electrochemical device 100 includes three isolation components, the three isolation components separate the internal space of the housing 10 into four independent cavities.

The separator includes a sealing portion. 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 isolator 20 is fixedly connected to other components at the sealing portion (which may be hot-melt connection or bonding). When the electrochemical device 100 has only one isolator, both side walls of the sealing portion of the separator are connected to the housing 10 . When the electrochemical device 100 has two separators, one side wall surface of the sealing portion of one separator is connected to the other separator, and the other side wall surface is connected to the housing 10 . When the number of spacers is three or more, both side walls of the sealing portion of the middle spacer are connected to other spacers located on both sides of the spacer.

In some embodiments, the isolator includes a base material layer and an encapsulation layer disposed on the surface of the base material layer. The material composition of the base material layer and the encapsulation layer is as follows:

The material of the base material layer includes at least one of metal, carbon material or 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, In, Zn, At least one of stainless steel and its composition or alloy; 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 Polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyimide, polyamide, polyethylene glycol, polyamide amide Imine, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylenenaphthalene, polyvinylidene fluoride, polypropylene carbonate, poly(ylidene fluoride) Ethylene-hexafluoropropylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymer, polyvinyl chloride, At least one of polystyrene, polyethernitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer or derivatives of the above substances.

The material of the encapsulation layer includes the second polymer. The second polymer includes: polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymer, polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyamide, polyester, amorphous alpha-olefin At least one of the copolymers or derivatives of the above substances.

The inventor of the present application found that when the series/parallel batteries in the same bag are heat-sealed and packaged, the temperatures on both sides of the separator are different due to the influence of different thickness positions, and there is a risk of poor sealing on the side with a lower temperature. The inventor of the present application has discovered through research that when the melting point of the encapsulation layer located on the inner surface of the sealing part is lower, the encapsulation layers on both surfaces of the base material layer can be well melted during encapsulation, and at the same time, The risk of excessive melting and extrusion of the encapsulation layer of the base material layer located on the outer surface of the sealing part is reduced, thereby improving the encapsulation reliability of the electrochemical device 100 . In order to facilitate a detailed understanding of the technical solution of the present application, please refer to FIG. 5 . The following is an introduction to the structure of the separator in the electrochemical device 100 when the electrochemical device 100 includes different numbers of separators.

In some embodiments, please refer to FIGS. 6-8 , the electrochemical device 100 includes a first isolation member 30 , and the first isolation member 30 includes a first base material layer 301 , a first encapsulation layer 302 and a second encapsulation layer 303 . An encapsulation layer 302 is provided on the first surface 301a of the first base material layer 301, and a second encapsulation layer 303 is provided on the second surface 301b of the first base material layer 301. The first surface 301a and the second surface 301b are disposed opposite to each other. . The melting point of the first encapsulation layer 302 is T ₁ and the melting point of the second encapsulation layer 303 is T ₂ . The first isolator 30 includes a first sealing portion 304 located in the sealing area 100a, the first surface 301a includes a first area 301a1 located in the first sealing portion 304, and the second surface 301b includes a second sealing portion 304 located in the first sealing portion 304. Area 301b1. Along the thickness direction Z of the seal area 100a, the first area 301a1 is adjacent to the first sealing surface 1222 relative to the second area 301b1. The distance between the first area 301a1 and the first sealing surface 1222 is D ₁ , and the second area 301b1 to The distance between the second sealing surface 1422 is D ₂ , D ₁ <D ₂ , and T ₁ >T ₂ is satisfied. The melting point refers to the temperature at which a meltable component first melts from a solid state into a liquid state when tested by a microscopic melting point tester.

In this way, in the thickness direction Z of the sealing area 100a, when the heat sealing head is used for packaging, the melting point of the first packaging layer 302 that is closer to the heat sealing head is relatively higher than the second packaging layer 303 that is farther from the heat sealing head. The melting point of the second encapsulation layer 303 is still very good even when the temperature inside the sealing area far away from the thermal sealing head is low, which reduces the possibility that the first encapsulation layer 302 has been fully melted but the second encapsulation layer 303 has not melted The occurrence of insufficient melting is beneficial to improving the sealing effect on the lower temperature side of the first isolator 30 , thereby improving the packaging reliability of the electrochemical device 100 . In some embodiments, T ₁ -T ₂ ≥7°C is satisfied. In some embodiments, T ₁ -T ₂ ≤ 40°C is satisfied.

In some embodiments, the thickness of the first encapsulation layer 302 is t ₁ and the thickness of the second encapsulation layer 303 is t ₂ , satisfying: 1.5t ₂ ≤ t ₁ ≤ 2t ₂ .

When the above conditions are met, the thickness t ₁ of the first encapsulation layer 302 will be greater than the thickness t ₂ 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, and thus The packaging reliability of the electrochemical device 100 is improved.

In some embodiments, 15 μm ≤ t ₁ ≤ 200 μm. In some embodiments, 10 μm ≤ t ₂ ≤ 100 μm.

In some embodiments, the final melting temperature of the second encapsulation layer is Th ₂ , which satisfies: Th ₂ >T ₁ . The final melting temperature refers to the temperature at which the meltable component just completely melts from the solid state to the liquid state when tested by a microscopic melting point tester. Therefore, when the second encapsulation layer 303 is completely melted, the first encapsulation layer 302 has begun to melt, thereby reducing the risk of the second encapsulation layer 303 being excessively melted and causing the seal to become unstable, thereby improving the packaging reliability of the electrochemical device 100 .

In some embodiments, Th ₂ -T ₂ ≥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 extruded.

In some embodiments, please refer to FIGS. 6-8 again. In addition to the first isolator 30 mentioned above, the electrochemical device 100 also includes a second isolator 40 . The second isolator 40 is disposed on the first isolator. between the component 30 and the second housing 14. The second isolator 40 includes a second base material layer 401, a third encapsulation layer 402 and a fourth encapsulation layer 403. The third encapsulation layer 402 is provided on the third surface 401a of the second base material layer 401. The fourth encapsulation layer 403 is provided on the fourth surface 401b of the second base material layer 401, and the third surface 401a is opposite to the fourth surface 401b. The melting point of the third encapsulation layer 402 is T ₃ and the melting point of the fourth encapsulation layer 403 is T ₄ . Wherein, 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 located in the second sealing portion 404. Area 401b1. Along the thickness direction Z of the seal 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 D ₃ . The fourth area 401b1 to The distance between the first sealing surface 1222 is D ₄ , D ₃ <D ₄ , and T ₃ >T ₄ is satisfied.

In this way, when the thermal sealing head is used for packaging, the melting point of the third packaging layer 402 that is closer to the packaging head is relatively higher than the melting point of the fourth packaging layer 403 that is farther from the packaging head. The third packaging layer 402 and the fourth packaging layer The layer 403 can be fully heat-melted during heat sealing, so that it can be better integrated with other parts, further improving the sealing effect of the sealing area 100a, and improving the packaging reliability of the electrochemical device 100. In some embodiments, T ₃ -T ₄ ≥7°C is satisfied. In some embodiments, T ₃ -T ₄ ≤ 40°C is satisfied.

In some embodiments, the final melting temperature of the third encapsulation layer 402 is Th ₃ , the final melting temperature of the fourth encapsulation layer 403 is Th ₄ , and any one of the following conditions is met:

(1)D ₄ <D ₃ ; T ₄ -T ₃ ≥7℃; Th ₃ >T ₄ . When the above conditions are met, it can be ensured that before the third encapsulation layer 402 is completely melted, the fourth encapsulation layer has begun to melt, so that both of them can be in a hot-melt state at the same time, reducing the risk of excessive melting of one of them resulting in an unstable seal. It is beneficial to improve the packaging reliability of the sealing area 100a.

(2)D ₃ <D ₄ ; T ₃ -T ₄ ≥7℃; Th ₄ >T ₃ . When the above conditions are met, it can be ensured that before the fourth encapsulation layer 403 is completely melted, the third encapsulation layer has begun to melt, so that both can be in a hot-melt state at the same time, reducing the risk of excessive melting of one of them, resulting in an unstable seal. It is beneficial to improve the packaging reliability of the sealing area 100a.

In some embodiments, the thickness of the third encapsulation layer 402 is t ₃ and the thickness of the fourth encapsulation layer 403 is t ₄ , satisfying: 1.5t ₄ ≤ _{t 3} ≤ 2t ₄ . When the above conditions are met, the thickness t ₃ of the third encapsulation layer 402 will be greater than the thickness t ₄ of the fourth encapsulation layer 403 , thereby reducing the risk of the third encapsulation layer 402 being excessively melted and extruded due to high temperature, and thus The packaging reliability of the electrochemical device 100 is improved.

In some embodiments, 15 μm ≤ t ₃ ≤ 200 μm. In some embodiments, 10 μm ≤ t ₄ ≤ 100 μm.

In some embodiments, as shown in FIGS. 6-8 , in addition to the first isolator 30 and the second isolator 40 described above, the electrochemical device 100 also includes a third isolator 50 . The third isolator 50 is located at between the first housing 12 and the second housing 14 . In this embodiment, the third isolation member 50 is located between the first isolation member 30 and the second isolation member 40 . The third isolator 50 includes a third base material layer 501, a fifth encapsulation layer 502 and a sixth encapsulation layer 503. The fifth encapsulation layer 502 is provided on the fifth surface 501a of the third base material layer 501. The sixth encapsulation layer 503 is provided on the sixth surface 501b of the third base material layer 501, and the fifth surface 501a and the sixth surface 501b are arranged opposite to each other. The melting point of the fifth encapsulation layer 502 is T ₅ and the melting point of the sixth encapsulation layer 503 is T ₆ . The third isolator 50 includes a third sealing portion 504 located in the sealing area 100a, a fifth surface 501a includes a fifth area 501a1 located in the third sealing portion 504, and a sixth surface 501b includes a sixth sealing portion 504 located in the third sealing portion 504. Area 501b1; along the thickness direction Z of the sealing area 100a, the fifth area 501a1 is adjacent to the first sealing surface 1222 relative to the sixth area 501b1. The distance from the fifth area 501a1 to the first sealing surface 1222 is D ₅ . The sixth area The distance from 501b1 to the second sealing surface 1422 is D ₆ , and D ₅ =D ₆ . Satisfy T ₅ -T ₆ ≤5℃.

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

It can be understood that the above describes the cases where the number of isolators is one, two and three respectively, and this rule is also applicable to a larger number of isolators. For example, when the number of spacers 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, the two spacers closer to the first sealing surface 1222, The encapsulation layer in each isolator close to the first sealing surface 1222 is an encapsulation layer with a high melting point, and the encapsulation layer in each isolator away from the first sealing surface 1222 is an encapsulation layer with a low melting point. 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 an encapsulation layer with a high melting point, and the encapsulation layer away from the second sealing surface 1422 in each isolator is It is an encapsulation layer with a low melting point. When the number of spacers is an odd number and is greater than or equal to 5, the packaging layer distribution of the spacers is the same as when the number of spacers is three. The middle spacer adopts the distribution of the third spacer 50, along the seal In the thickness direction of the portion 100a, the spacers on one side of the most middle spacer adopt the above-mentioned distribution of the first spacers, and the spacers on the other side of the most middle spacer adopt the above-mentioned distribution of the second spacers.

Example 1

Preparation of lithium-ion batteries

(1) Preparation of negative electrode sheets: Mix the negative 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 the solid content into a 70wt% slurry 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 piece 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 piece is cut into 41mm×61mm specifications for use.

(2) Preparation of positive electrode sheet: Mix the positive active materials lithium cobalt oxide (LiCoO ₂ ), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.0:1.5, and add N - Methylpyrrolidone (NMP), prepared into 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 piece is cut into 38mm×58mm specifications for use.

(3) Preparation of electrolyte: In a dry argon atmosphere, first combine the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of EC:EMC:DEC= Mix at 30:50:20, then add lithium salt lithium hexafluorophosphate (LiPF ₆ ) to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a LiPF ₆ concentration of 12.5% based on the mass of the electrolyte.

(4) Preparation of the first electrode assembly and the second electrode assembly: stack the separator, negative electrode piece, separator, and positive electrode piece in sequence to form a laminated structure, and then fix the four corners of the entire laminated structure to obtain the electrode piece components. Each electrode assembly contains 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 made of polyethylene (PE) with a thickness of 15 μm. )membrane.

(5) Preparation of the separator: uniformly disperse the first encapsulation layer material polypropylene (PP, melting point: 147°C) into the dispersant N-methylpyrrolidone (NMP) to prepare a first encapsulation layer PP suspension; Evenly disperse the second encapsulation layer material polypropylene (PP, melting point: 140°C) into the dispersant N-methylpyrrolidone (NMP) to prepare a second encapsulation layer PP suspension; use a glue applicator to coat the material with a thickness of Both sides of the 50 μm aluminum layer are coated with the first encapsulation layer PP suspension and the second encapsulation layer PP suspension respectively; then dried at 130°C, where the thickness t ₁ of the first encapsulation layer is 150 μm, and the thickness t of the second encapsulation layer is 150 μm. The thickness _t2 of the encapsulation layer is 100 μm.

(6) Electrode assembly assembly: Place the first aluminum plastic film (thickness 150 μm) punched and formed into the assembly jig with the pit surface facing up. Place the first electrode assembly in the pit and place it on the pole of the first electrode assembly. The ear surface is provided with tab glue, and then the first separator is placed on the first electrode assembly, wherein the first encapsulation layer in the first separator is adjacent to the first aluminum plastic film, and the second encapsulation layer is away from the first aluminum Plastic film to align the edges and apply external force to compress to obtain the assembled semi-finished product 1. Place the assembled semi-finished product 1 in the assembly fixture, with the second packaging layer of the first separator facing up, place the second electrode assembly on the first separator so that the edges are aligned, apply external force to compress, and place the second electrode assembly on the second electrode assembly The tab surface is provided with tab glue, and then the second separator is placed on the second electrode assembly, wherein the second encapsulation layer in the second separator is adjacent to the first aluminum plastic film, and the first encapsulation layer is away from the second electrode assembly. An aluminum-plastic film is used to align the edges, and external force is applied to compress the film to obtain the assembled semi-finished product 2. Place the assembled semi-finished product 2 in the assembly fixture, with the first packaging layer of the second separator facing upward, and place the third electrode assembly on the second separator; then place the other punched and formed second aluminum plastic film pit surface Cover the third electrode component downward, and set tab glue on the tab surface of the third electrode component. The positive and negative electrode tabs of the first electrode assembly, the second electrode assembly and the third electrode assembly are all pulled out of the aluminum plastic film, and are top sealed and side sealed by hot pressing to obtain the assembled electrode assembly.

(7) Liquid injection packaging: Inject electrolyte into each cavity separately, and seal after hot pressing, forming, and degassing.

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

Examples 2-6 and Comparative Examples

The difference from Embodiment 1 is that the first encapsulation layer and the second encapsulation layer respectively select polypropylene with corresponding melting point and other characteristics in Table 1 and the thickness.

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

The method used for the test results obtained in Examples 1-6 and Comparative Examples in Table 1 is as follows: using a multi-functional peeling device, first clamp the first isolator and the second isolator on one side of the packaging area with the clamp, and then pull. Separate the packaging areas of the first isolator and the second isolator, and observe the bonding position of the separator after separation. If the color of the bonding position after separation is milky white, it indicates that the separator is well integrated; if there is a partial milky white defect If it is obvious, it indicates that the spacer is poorly integrated. From the comparison between Examples 1-6 and Comparative Examples in Table 1, it can be seen that when T ₁ -T ₂ ≥7°C, the sealing area 100a of the electrochemical device 100 is well fused, indicating that the melting point of the first encapsulation layer 302 is greater than that of the second encapsulation When the melting point of the layer 303 is reached, the second encapsulating layer 303 can be melted well, thereby improving the packaging reliability and safety of the electrochemical device 100 .

This application also provides an electronic device, which includes the electrochemical device provided by this application. The electronic device of the present application is not particularly limited and may be any electronic device known in the art. For example, electronic devices include, but are not limited to, notebook computers, pen computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headsets, video recorders, LCD televisions, portable Cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting equipment, toys, game consoles , watches, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

It should be noted that the preferred embodiments of the present application are given in the description 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 used as additional limitations on the content of the present application, and are provided for the purpose of making the disclosure of the present application more thorough and comprehensive. Moreover, the above technical features can be continuously combined with each other to form various embodiments not listed above, which are all deemed to be within the scope of the description of this application; further, for those of ordinary skill in the art, they can be improved or transformed according to the above description. , and all these improvements and transformations should fall within the protection scope of the claims appended to this application.

Claims

An electrochemical device, characterized by including:

a first housing and a second housing;

A first isolation member is located between the first housing and the second housing, and the electrochemical device is provided with a first cavity between the first housing and the first isolation member, The electrochemical device is provided with a second cavity between the second housing and the first isolator; the first isolator includes a first base material layer, a first encapsulation layer and a second encapsulation layer. , the first encapsulation layer is provided on the first surface of the first base material layer, the second encapsulation layer is provided on the second surface of the first base material layer, the first surface and the third Two surfaces face 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, the first housing, the first isolator and the second housing are connected in the sealing area, and the first housing includes a separation located in the sealing area. The first sealing surface of the first isolation member, the second housing includes a second sealing surface located in the sealing area away from the first isolation member, the first isolation member includes a second sealing surface located in the sealing area the first sealing portion, the first surface includes a first area located in the first sealing portion, 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 D 1 , and the distance from the second area to the first sealing surface is D 1 . The distance between the two sealing surfaces is D 2 , D 1 <D 2 ; wherein, the melting point of the first encapsulation layer is T 1 , and the melting point of the second encapsulation layer is T 2 , satisfying T 1 >T 2 .
The electrochemical device according to claim 1, characterized in that T 1 -T 2 ≥ 7°C, and/or T 1 -T 2 ≤ 40°C.
The electrochemical device according to claim 1, further comprising a second isolator located between the first isolator and the second housing, the second isolator The component includes a second base material layer, a third encapsulation layer and a fourth encapsulation layer, the third encapsulation layer is provided on the third surface of the second base material layer, and the fourth encapsulation layer is provided on the second The fourth surface of the base material layer, the third surface is opposite to the fourth surface;

The second isolator includes a second sealing portion located in the sealing area, the third surface includes a third area located in the second sealing portion, and the fourth surface includes a second sealing portion located in the second sealing portion. The fourth area; along the thickness direction of the seal area, the fourth area is adjacent to the second sealing surface relative to the third area, and the distance from the third area to the first sealing surface is D 3 , the distance from the fourth area to the second sealing surface is D 4 ; wherein, the melting point of the third encapsulation layer is T 3 , the melting point of the fourth encapsulation layer is T 4 , and the following conditions are met: Any of:

(1)D 4 <D 3 ; T 4 -T 3 ≥7℃;

(2)D 3 <D 4 ; T 3 -T 4 ≥7℃.
The electrochemical device according to claim 3, characterized in that T 4 -T 3 ≤ 40°C or T 3 -T 4 ≤ 40°C.
The electrochemical device according to claim 3, further comprising a third isolation member,

The third isolator is located between the first shell and the second shell. The third isolator includes a third base material layer, a fifth encapsulation layer and a sixth encapsulation layer. The fifth The encapsulation layer is provided on the fifth surface of the third base material layer, the sixth encapsulation layer is provided on the sixth surface of the third base material layer, and the fifth surface is opposite to the sixth surface;

The third isolator 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 third sealing portion located in the third sealing portion. The sixth area; along the thickness direction of the seal area, the fifth area is adjacent to the first sealing surface relative to the sixth area, and the distance from the fifth area to the first sealing surface is D 5 , the distance from the sixth area to the second sealing surface is D 6 , D 5 =D 6 ; wherein, the melting point of the fifth encapsulation layer is T 5 , and the melting point of the sixth encapsulation layer is T 6 , satisfying T 5 -T 6 ≤5℃.
The electrochemical device according to claim 1, wherein the thickness of the first encapsulation layer is t 1 , the thickness of the second encapsulation layer is t 2 , and at least one of the following conditions is met:

(a)1.5t 2 ≤t 1 ≤2t 2 ;

(b)15μm≤t 1 ≤200μm;

(c) 10μm≤t2≤100μm .
The electrochemical device according to claim 1, wherein the final melting temperature of the second encapsulation layer is Th 2 and satisfies at least one of the following conditions:

(d) Th 2 >T 1 ;

(e) Th 2 -T 2 ≥25°C.
The electrochemical device according to claim 3, wherein 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: By:

(f)D 4 <D 3 ; T 4 -T 3 ≥7℃; Th 3 >T 4 ;

(g)D 3 <D 4 ; T 3 -T 4 ≥7℃; Th 4 >T 3 .
The electrochemical device according to claim 7, wherein the first electrode assembly and the second electrode assembly are connected in series.
An electronic device, characterized by comprising the electrochemical device according to any one of claims 1-9.