Electrochemical device and electronic equipment

Abstract

The embodiment of the present application discloses an electrochemical device and an electronic device, including a housing, a first electrode assembly, a second electrode assembly, and an isolating member, wherein the isolating member is disposed between the first electrode assembly and the second electrode assembly, and the first electrode assembly, the isolating member, and the second electrode assembly are disposed sequentially along a first direction. The housing is provided with a first cavity and a second cavity; the first electrode assembly includes a first pole piece assembly received in the first cavity; the second electrode assembly includes a second pole piece assembly received in the second cavity. Along the first direction, the area of ​​the first projection of the first pole piece assembly on the isolating member is S 1 , the area of ​​the second projection of the second pole piece assembly on the isolation member is S 2 , the area of ​​the overlap between the first projection and the second projection is S 3 , satisfying S 3 / S 1 ≥0.9, S 3 / S 2 ≥0.9. At this time, it is beneficial to improve the safety of the electrochemical device.

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. Because in some application scenarios, a single battery cell cannot achieve the desired output power; therefore, 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, and the electrode assemblies in parallel are separated by an isolator to avoid interference with each other. Summary of the invention

[0003] The inventors of the present application have discovered through research that in batteries connected in series / parallel in the same bag, since there are multiple electrode assemblies in the shell, uneven formation is likely to occur during the hot pressing process, leading to safety hazards such as lithium deposition during the cycle process.

[0004] In view of the above technical problems, the present application provides an electrochemical device and an electronic device to improve the safety of batteries connected in series or in parallel in the same bag.

[0005] In order to solve the above technical problems, the first aspect of the present application is to provide an electrochemical device, including a shell, a first electrode assembly, a second electrode assembly and an isolating member, wherein the isolating member is arranged between the first electrode assembly and the second electrode assembly, and the first electrode assembly, the isolating member and the second electrode assembly are arranged in sequence along a first direction. The shell is provided with a first cavity and a second cavity; the first electrode assembly includes a first pole piece assembly accommodated in the first cavity; the second electrode assembly includes a second pole piece assembly accommodated in the second cavity. Along the first direction, the area of ​​the first projection of the first pole piece assembly on the isolating member is S1, the area of ​​the second projection of the second pole piece assembly on the isolating member is S2, and the area of ​​the overlapping portion of the first projection and the second projection is S3, satisfying S3 / S1≥0.9, S3 / S2≥0.9. At this time, the first pole piece assembly and the second pole piece assembly have a larger overlapping area in the first direction, so that the first pole piece assembly and the second pole piece assembly can be evenly compressed with a larger overlapping area during the hot pressing process, so as to promote the uniform formation of the solid electrolyte interface film (SIE film) and reduce the risk of lithium deposition in the non-overlapping parts of the first electrode assembly and the second electrode assembly, thereby improving the safety and reliability of the electrochemical device.

[0006] Optionally, the electrochemical device satisfies S3 / S1≥0.95 and S3 / S2≥0.95. In this way, the first pole piece assembly and the second pole piece assembly can be more evenly pressed during the hot pressing process, further promoting the uniform formation of the SE I film, which is beneficial to improving the safety of the electrochemical device.

[0007] Optionally, the first electrode sheet assembly includes a first positive electrode sheet, the first positive electrode sheet includes a first positive current collector and a first positive active material layer located on the surface of the first positive current collector, and along the width direction of the first positive active material layer, the first positive active material layer includes a first edge and a second edge that are opposite. The second electrode sheet assembly includes a second positive electrode sheet, the second positive electrode sheet includes a second positive current collector and a second positive active material layer located on the surface of the second positive current collector, and along the width direction of the second positive active material layer, the second positive active material layer includes a third edge and a fourth edge that are opposite. When viewed along the first direction, the first edge is adjacent to the third edge, the second edge is adjacent to the fourth edge, the distance between the first edge and the third edge is d1, and the distance between the second edge and the fourth edge is d2, satisfying: d1≤4mm, d2≤4mm.

[0008] In this way, the misalignment of the positive electrode active area that effectively participates in lithium ion extraction and insertion in the first pole piece assembly and the second pole piece assembly can be reduced, promoting the uniform formation of the negative electrode SE I film on the opposite side, thereby reducing the risk of lithium analysis in the non-overlapping active parts of the first pole piece assembly and the second pole piece assembly.

[0009] Optionally, the first electrode sheet assembly further includes a first negative electrode sheet, the first negative electrode sheet includes a first negative electrode current collector and a first negative electrode active material layer located on the surface of the first negative electrode current collector, and along the width direction of the first positive electrode active material layer, the first negative electrode active material layer includes a first extension area that exceeds the first positive electrode active material layer; the second electrode sheet assembly further includes a second negative electrode sheet, the second negative electrode sheet includes a second negative electrode current collector and a second negative electrode active material layer located on the surface of the second negative electrode current collector, and along the width direction of the second positive electrode active material layer, the second negative electrode active material layer includes a second extension area that exceeds the second positive electrode active material layer. In this way, the risk of lithium plating in the first electrode sheet assembly and the second electrode sheet assembly can be reduced.

[0010] Optionally, the first positive electrode plate also includes a first insulating layer located on the surface of the first positive electrode current collector, and when viewed along the first direction, the first insulating layer at least partially overlaps with the first extension area; and / or, the second positive electrode plate also includes a second insulating layer located on the surface of the second positive electrode current collector, and when viewed along the first direction, the second insulating layer at least partially overlaps with the second extension area. In this way, the first insulating layer supports the first extension area in the first direction, so as to promote the formation of a uniform SE I film on the surface of the active material in the first extension area during the hot pressing process. Similarly, the second insulating layer supports the second extension area in the first direction, so as to promote the formation of a uniform SE I film on the surface of the active material in the second extension area during the hot pressing process. Thereby reducing the risk of lithium deposition at the edge of the negative electrode plate of the first electrode assembly and / or the second electrode assembly.

[0011] Optionally, the first pole piece assembly and the second pole piece assembly are laminated structures; along the length direction of the first positive electrode active material layer, the first positive electrode active material layer includes a relative fifth edge and a sixth edge; along the length direction of the second positive electrode active material layer, the second positive electrode active material layer includes a relative seventh edge and an eighth edge; observed along the first direction, the fifth edge is adjacent to the seventh edge, the sixth edge is adjacent to the eighth edge, the distance between the fifth edge and the seventh edge is d3, and the distance between the sixth edge and the eighth edge is d4, satisfying: d3≤4mm, d4≤4mm. In this way, the positive active area that effectively participates in lithium ion deintercalation in the first pole piece assembly and the second pole piece assembly can be less misaligned, promoting the uniform formation of the negative electrode SE I film on the opposite side, thereby reducing the risk of lithium analysis in the non-overlapping active parts of the first pole piece assembly and the second pole piece assembly.

[0012] Optionally, when viewed along the first direction, the first edge coincides with the third edge; and / or, when viewed along the first direction, the second edge coincides with the fourth edge.

[0013] Optionally, when viewed along the first direction, the fifth edge coincides with the seventh edge; and / or, when viewed along the first direction, the sixth edge coincides with the eighth edge.

[0014] Optionally, the electrochemical device satisfies at least one of the following conditions: (a) the isolation member includes a first packaging layer, a second packaging layer and an intermediate layer, wherein the intermediate layer is located between the first packaging layer and the second packaging layer; (b) the first electrode assembly also includes a first electrode tab, and the second electrode assembly includes a second electrode tab, and the first electrode tab and the second electrode tab both extend from the same side of the shell; (c) the first electrode assembly and the second electrode assembly are connected in series.

[0015] The second aspect of the present application provides an electronic device comprising the above-mentioned electrochemical device.

[0016] The beneficial effect of the present application is that the present application satisfies S3 / S1≥0.9 and S3 / S2≥0.9. At this time, the first pole piece assembly and the second pole piece assembly have a larger overlapping area in the first direction, and the first pole piece assembly and the second pole piece assembly can be uniformly compressed with a larger overlapping area during the hot pressing process to promote the uniform formation of the solid electrolyte interface film (SEI film), reduce the risk of lithium deposition in the non-overlapping parts of the first electrode assembly and the second electrode assembly, and help improve the safety and reliability of the electrochemical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use 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. For ordinary technicians in this field, other drawings can also be obtained based on the drawings.

[0018] Figure 1 is a schematic structural diagram of an electrochemical device in one embodiment of the present application;

[0019] Figure 2 yes Figure 1 Schematic diagram of the partial structure after cutting along the XY plane;

[0020] Figure 3 yes Figure 1 Schematic diagram after cutting along the straight line MM';

[0021] Figure 4 is a schematic diagram of a first electrode assembly, a separator, and a second electrode assembly after being cut away;

[0022] Figure 5 is a schematic diagram of a first pole piece assembly having a winding structure;

[0023] Figure 6 is a schematic diagram of a first pole piece assembly having a laminated structure;

[0024] Figure 7 is a schematic diagram of the overlap between the first pole piece assembly and the second pole piece assembly when viewed along the Z direction;

[0025] Figure 8 Schematic diagram of the overlap between the first positive electrode active material layer and the second positive electrode active material layer when viewed along the Z direction. DETAILED DESCRIPTION

[0026] In order to facilitate the 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.

[0027] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning 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" used in this specification includes any and all combinations of one or more of the related listed items.

[0028] 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 and an isolation member 20. The shell 10 is used to limit a closed space for accommodating the electrode assembly, and the isolation member 20 is used to separate the internal space of the shell 10, thereby increasing the number of independent cavities inside the shell 10.

[0029] The housing 10 includes a first sealing portion 103, which is used to seal with the isolation member 20, that is, the first sealing portion 103 is used to be fixedly connected (can be hot-melt connected or bonded) with the isolation member 20. The first sealing portion 103 includes a first sealing edge 1031, which is an edge of the first sealing portion 103 away from the cavity space of the housing 10.

[0030] The electrochemical device 100 may include one separator 20 or multiple separators 20. When the electrochemical device 100 includes one separator 20, one separator 20 may separate the internal space of the housing 10 into two independent cavities. When the electrochemical device 100 includes multiple separators 20, multiple separators 20 may separate the internal space of the housing 10 into multiple independent cavities. For example, when the electrochemical device 100 specifically includes two separators 20, the two separators 20 may separate the internal space of the housing 10 into three independent cavities; when the electrochemical device 100 includes three separators 20, the three separators 20 separate the internal space of the housing 10 into four independent cavities.

[0031] In some embodiments, the separator 20 includes a first sealing area 21, and when the electrochemical device 100 is packaged, the portion of the separator 20 located in the first sealing area 21 is sealed with other components. That is, the portion of the separator 20 in the first sealing area 21 is fixedly connected to other components (it can be hot-melt connection or bonding). When the electrochemical device 100 has only one separator 20, both side walls of the first sealing area 21 of the separator 20 are connected to the shell 10. When the electrochemical device 100 has two separators 20, one side wall of the first sealing area 21 of one separator 20 is connected to the other separator 20, and the other side wall is connected to the shell 10. When the number of separators 20 is three or more, both side walls of the first sealing area 21 of the separator 20 located in the middle are connected to the other separators 20 located on both sides of the separator 20.

[0032] The first sealing area 21 may be in a “U” shape, and the first sealing area 21 may extend to the outer edge of the isolation member 20 , or the first sealing area 21 may be spaced a certain distance from the outer edge of the isolation member 20 .

[0033] For ease of description, the following embodiments are described by taking the electrochemical device 100 as including a separator 20. The separator 20 divides the internal space of the housing 100 into two independent chambers, which are respectively referred to as a first chamber 101 and a second chamber 102.

[0034] The electrochemical device 100 may include two electrode assemblies, or may include more than three electrode assemblies. For ease of description, the following embodiments are illustrated by taking the electrochemical device 100 as including two electrode assemblies. Figure 3 As shown, the two electrode assemblies are respectively a first electrode assembly 30 and a second electrode assembly 40. When the electrochemical device 100 has a separator 20, and the separator 20 separates two independent cavities, the first electrode assembly 30 is disposed in the aforementioned first cavity 101, and the second electrode assembly 40 is disposed in the aforementioned second cavity 102. The first electrode assembly 30, the separator 20, and the second electrode assembly 40 are distributed along a first direction (Z direction), and the first direction is the same as the thickness direction of the separator 20.

[0035] In some embodiments, Figure 4 As shown, Figure 4: is a cross-sectional view of the first electrode assembly 30, the separator 20 and the second electrode assembly 40. The first electrode assembly 30 includes a first electrode plate assembly 32 and a first pole ear 34, and the first pole ear 34 is connected to the first electrode plate assembly 32. In this embodiment, the first electrode plate assembly 32 includes a first positive electrode plate 321, a first negative electrode plate 322 and a first isolation film 323, and the first isolation film 323 is located between the first positive electrode plate 321 and the first negative electrode plate 322. The first isolation film 323 is used to reduce the risk of short circuit between the first positive electrode plate 321 and the first negative electrode plate 322. There are at least two first pole ears 34, and the first pole ear 34 used to connect with the first positive electrode plate 321 is a positive pole ear, and the first pole ear 34 used to connect with the first negative electrode plate 322 is a negative pole ear.

[0036] The first positive electrode sheet 321 includes a first positive current collector 3211 and a first positive active material layer 3212 located on the surface of the first positive current collector 3211. The first positive active material layer 3212 is disposed on both opposite surfaces of the first positive current collector 3211, and the first positive active material layer 3212 may be disposed on a partial area or on the entire area.

[0037] The first negative electrode sheet 322 includes a first negative current collector 3221 and a first negative active material layer 3222 located on the surface of the first negative current collector 3221. The first negative active material layer 3222 is disposed on both opposite surfaces of the first negative current collector 3221, and the first negative active material layer 3222 may be disposed on a partial area or on the entire area.

[0038] In order to facilitate understanding of the structure of the pole piece assembly, the structure of the first pole piece assembly is taken as an example for explanation below. The structure of the first pole piece assembly 32 is applicable to the second pole piece assembly 42 .

[0039] In some embodiments, Figure 5 As shown, the first electrode assembly 32 is a winding structure, that is, the first positive electrode sheet 321, the first separator 323 and the first negative electrode sheet 322 are stacked along the first thickness direction and then wound along the first long side direction. The first thickness direction refers to the thickness direction of any one of the first positive electrode sheet 321, the first separator 323 and the first negative electrode sheet 322, and the first long side direction refers to the long side direction of any one of the first positive electrode sheet 321, the first separator 323 and the first negative electrode sheet 322. In this embodiment, the first thickness direction is the same as the first direction (Z direction).

[0040] In other embodiments, Figure 6As shown, the first pole piece assembly 32 is a laminated structure, that is, the first positive pole piece 321, the first separator 323 and the first negative pole piece 322 are stacked along the first thickness direction. At this time, there are multiple first positive pole pieces 321, first separators 323 and first negative pole pieces 322. Along the first thickness direction, a first separator 323 is arranged between each first positive pole piece 321 and each first negative pole piece 322. Among them, the first thickness direction refers to the thickness direction of any one of the first positive pole piece 321, the first negative pole piece 322 and the first separator 323. The first thickness direction is the same as the first direction (Z direction).

[0041] It is understandable that the first pole piece assembly 32 may be the above-mentioned winding structure or the above-mentioned stacked structure, and the specific structure may be selected according to actual needs.

[0042] Likewise, the structure of the second electrode assembly 40 is similar to that of the first electrode assembly 30 .

[0043] The details are as follows:

[0044] Please refer again Figure 4 , the second electrode assembly 40 includes a second electrode assembly 42 and a second pole ear 44, and the second pole ear 44 is connected to the second electrode assembly 42. In this embodiment, the second electrode assembly 42 includes a second positive electrode sheet 421, a second negative electrode sheet 422, and a second isolation film 423, and the second isolation film 423 is located between the second positive electrode sheet 421 and the second negative electrode sheet 422, and the second isolation film 423 is used to reduce the risk of short circuit between the second positive electrode sheet 421 and the second negative electrode sheet 422. There are at least two second pole ears 44, and the second pole ear 44 used to connect with the second positive electrode sheet 421 is a positive pole ear, and the second pole ear 44 used to connect with the second negative electrode sheet 422 is a negative pole ear.

[0045] The second positive electrode sheet 421 includes a second positive current collector 4211 and a second positive active material layer 4212 located on the surface of the second positive current collector 4211. The second positive active material layer 4212 is disposed on both opposite surfaces of the second positive current collector 4211, and the second positive active material layer 4212 may be disposed on a partial area or on the entire area.

[0046] The second negative electrode sheet 422 includes a second negative current collector 4221 and a second negative active material layer 4222 located on the surface of the second negative current collector 4221. The second negative active material layer 4222 is disposed on both opposite surfaces of the second negative current collector 4221, and the second negative active material layer 4222 may be disposed on a partial area or on the entire area.

[0047] In some embodiments, Figure 7 As shown, Figure 7 The middle separator 20 is not shown. Along the first direction Z, the area of ​​the first projection of the first pole piece assembly 32 on the separator 20 is S1, the area of ​​the second projection of the second pole piece assembly 42 on the separator 20 is S2, and the area of ​​the overlapping part of the first projection and the second projection is S3, satisfying S3 / S1≥0.9, S3 / S2≥0.9. It should be understood that, when observed from the first direction Z, ignoring the first isolation film 323, the projection area of ​​the first positive pole piece 321 and the first negative pole piece 322 in the first pole piece assembly 32 on the separator 20 is the first projection area S1 of the first pole piece assembly 32 on the separator 20; ignoring the second isolation film 423, the projection area of ​​the second positive pole piece 421 and the second negative pole piece 422 in the second pole piece assembly 42 on the separator 20 is the second projection area S2 of the second pole piece assembly 42 on the separator 20. In particular, if observed from the first direction Z, the first negative electrode plate 322 covers the first positive electrode plate 321, and the second negative electrode plate 422 covers the second positive electrode plate 421. At this time, when observed along the first direction Z, the overlapping area S3 between the first electrode assembly 32 and the second electrode assembly 42 is actually the overlapping area between the first negative electrode plate 322 and the second negative electrode plate 422.

[0048] The inventors of the present application have discovered through research that when multiple electrode assemblies are stacked inside an electrochemical device 100, if the stacking misalignment of the multiple electrode assemblies is not controlled and restricted, it will lead to a large misalignment between the multiple electrode assemblies. During the hot pressing process, it is easy to cause uneven formation of the misaligned parts, thereby affecting the uniformity of the SEI film, and further causing the electrochemical device to be prone to safety hazards such as lithium deposition during subsequent charging and discharging processes.

[0049] The inventor of the present application has found through research that when the misalignment of multiple electrode assemblies stacked inside an electrochemical device is controlled to meet certain conditions, the uniformity of SEI film formation in each electrode assembly can be improved. Taking the electrochemical device including two electrode assemblies as an example, when the first electrode assembly 32 and the second electrode assembly 42 are along the first direction Z and meet S3 / S1≥0.9 and S3 / S2≥0.9, the misalignment of the first electrode assembly 32 and the second electrode assembly 42 is small, and the pressure on the first electrode assembly 32 and the second electrode assembly 42 can be uniform during the hot pressing process, promoting the uniform formation of the SEI film, thereby improving the safety of the electrochemical device 100.

[0050] In some embodiments, the area S1 of the first projection and the area S2 of the second projection satisfy S3 / S1≥0.95, S3 / S2≥0.95. In this way, the misalignment between the first electrode assembly 30 and the second electrode assembly 40 can be reduced, and during the hot pressing process, the pressure on the first pole piece assembly 32 and the second pole piece assembly 42 is more uniform, further promoting the uniform formation of the SEI film, thereby improving the safety of the electrochemical device 100.

[0051] In some embodiments, the plurality of first pole tabs 34 and the plurality of second pole tabs 44 extend out of the shell 10 from the first sealing edge 1031 of the shell 10. In some embodiments, the plurality of first pole tabs 34 and the plurality of second pole tabs 44 extend out from different sides of the shell 10, and at least one first pole tab 34 is connected to one second pole tab 44 on the same side of the shell 10, and the polarities of the connected first pole tabs 34 and second pole tabs 44 are different, so that the first electrode assembly 30 and the second electrode assembly 40 are connected in series.

[0052] In some embodiments, see Figure 8 , along the width direction X of the first positive active material layer 3212, such as the first positive active material layer 3212 includes a first edge 32121 and a second edge 32122 that are oppositely disposed. Along the width direction of the second positive active material layer 4212, the second positive active material layer 4212 includes a third edge 42121 and a fourth edge 42122 that are oppositely disposed. In this embodiment, the width direction of the first positive active material layer 3212 is the same as the width direction of the second positive active material layer 4212.

[0053] Observing along the first direction Z, the first edge 32121 is adjacent to the third edge 42121, the second edge 32122 is adjacent to the fourth edge 42122, the distance between the first edge 32121 and the third edge 42121 is d1, and the distance between the second edge 32122 and the fourth edge 42122 is d2, satisfying d1≤4mm, d2≤4mm. At this time, the misalignment between the first positive electrode active material layer 3212 and the second positive electrode active material layer 4212 is small, which can reduce the misalignment degree of the positive electrode active area effectively participating in lithium ion deintercalation between the first electrode assembly 32 and the second electrode assembly 42, thereby promoting the uniform formation of the negative electrode SEI film on the opposite side, reducing the risk of lithium analysis in the non-overlapping active parts of the first pole piece assembly and the second pole piece assembly, thereby improving the safety of the electrochemical device 100.

[0054] In some embodiments, when viewed along the first direction Z, the first edge 32121 coincides with the third edge 32122 , and / or, when viewed along the first direction Z, the second edge 32122 coincides with the fourth edge 42122 .

[0055] In some embodiments, see Figure 4 , along the width direction X of the first positive electrode active material layer 3212, the first negative electrode active material layer 3222 includes a first extended region 3222a that exceeds the first positive electrode active material layer 3212. Along the width direction of the second positive electrode active material layer 4212, the second negative electrode active material layer 4222 includes a second extended region 4222a that exceeds the second positive electrode active material layer 4212. In this way, the risk of lithium deposition in the first negative electrode sheet 322 and the second negative electrode sheet 422 can be reduced.

[0056] In some embodiments, please refer again to Figure 4 , the first positive electrode plate 321 further includes a first insulating layer 3213 located on the surface of the first positive current collector 3211, and when viewed along the first direction Z, the first insulating layer 3213 at least partially overlaps with the first extended area 3222a; and / or, the second positive electrode plate 421 further includes a second insulating layer 4213 located on the surface of the second positive current collector 4211, and when viewed along the first direction Z, the second insulating layer 4213 at least partially overlaps with the second extended area 322a. In this way, the first insulating layer 3213 can support the first extended area 3222a in the first direction Z, which is conducive to compacting the part of the first negative electrode active material layer 3222 located in the first extended area 3222a during the hot pressing process. Similarly, the second insulating layer 3213 can support the second extended area 4222a in the first direction Z, which is conducive to compacting the part of the second negative electrode active material layer 4222 located in the second extended area 4222a during the hot pressing process. This promotes the formation of a uniform SEI film on the surface of the negative electrode active material layer of the first extension area 3222a and the second extension area 4222a, and reduces the risk of lithium deposition at the edge of the negative electrode sheet of the first electrode assembly 32 and / or the second electrode assembly 42.

[0057] In some embodiments, the materials of the first insulating layer 3213 and the second insulating layer 4213 include a binder and inorganic particles, and the insulating layers meet at least one of the following conditions:

[0058] (a) the inorganic particles include at least one of HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, boehmite, magnesium hydroxide, aluminum hydroxide, lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS2 glass, P2S5 glass, Li2O, LiF, LiOH, Li2CO3, LiAlO2, lithium germanium phosphosulfur ceramics or garnet ceramics;

[0059] (b) the binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, nitrile rubber, polyurethane, fluorinated rubber, polyvinyl alcohol or sodium polyacrylate;

[0060] (c) The mass percentage of the binder is 5% to 40% based on the mass of the insulating layer.

[0061] In some embodiments, please refer again to Figure 8 When both the first pole piece assembly 32 and the second pole piece assembly 42 are laminated structures, along the length direction Y of the first positive electrode active material layer 3212, the first positive electrode active material layer 3212 includes a fifth edge 32123 and a sixth edge 32124 that are opposite to each other; along the length direction Y of the second positive electrode active material layer 4212, the second positive electrode active material layer 4212 includes a seventh edge 42123 and an eighth edge 42124 that are opposite to each other. When viewed along the first direction Z, the fifth edge 32123 is adjacent to the seventh edge 42123, the sixth edge 32124 is adjacent to the eighth edge 42124, the distance between the fifth edge 32123 and the seventh edge 42123 is d3, and the distance between the sixth edge 32124 and the eighth edge 42124 is d4, satisfying d3≤4mm, d4≤4mm. In this way, the misalignment degree between the first positive electrode active material layer 3212 and the second positive electrode active material layer 4212 can be further reduced, thereby reducing the misalignment degree of the positive electrode active area effectively participating in lithium ion deintercalation between the first electrode assembly 32 and the second electrode assembly 42, thereby promoting the uniform formation of the negative electrode SEI film on the opposite side, reducing the risk of lithium analysis in the non-overlapping active parts of the first electrode assembly and the second electrode assembly, thereby improving the safety of the electrochemical device 100.

[0062] In some embodiments, when viewed along the first direction Z, the fifth edge 32123 coincides with the seventh edge 42123 ; and / or, when viewed along the first direction Z, the sixth edge 32124 coincides with the eighth edge 42124 .

[0063] In some embodiments, the isolation member 20 includes a first encapsulation layer, a second encapsulation layer, and an intermediate layer, wherein the intermediate layer is located between the first encapsulation layer and the second encapsulation layer.

[0064] The material of the middle layer includes at least one of metal, carbon material or first polymer;

[0065] The metal includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn, stainless steel, and their combinations or alloys.

[0066] The carbon material includes at least one of carbon felt, carbon film, carbon black, acetylene black, fullerene, conductive graphite film or graphene film.

[0067] The first polymer includes 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 at least one of the derivatives of the above substances.

[0068] The material of the encapsulation layer (ie, the first encapsulation layer or the second encapsulation layer) includes a second polymer.

[0069] The second polymer includes: polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous α-olefin copolymer or at least one of the derivatives thereof.

[0070] Example 1

[0071] Preparation of lithium-ion batteries

[0072] (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, prepare a slurry with a solid content of 70wt%, and stir evenly. The slurry is evenly coated on one surface of the negative electrode collector copper foil, dried, and a negative electrode sheet coated with a negative electrode active material layer on one side is obtained. Repeat the above steps on the other surface of the negative electrode 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 standby use.

[0073] (2) Preparation of positive electrode sheet: Mix the positive electrode active materials lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.0:1.5, add N-methylpyrrolidone (NMP), and prepare a slurry with a solid content of 75wt%, and stir evenly. The slurry is evenly coated on one surface of the positive electrode collector aluminum foil, dried, and a positive electrode sheet coated with a positive electrode active material layer on one side is obtained. On the other surface of the positive electrode collector aluminum foil, repeat the above steps 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 specification of 38mm×58mm for standby use.

[0074] (3) Preparation of electrolyte: In a dry argon atmosphere, first mix the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of EC:EMC:DEC=30:50:20, then add lithium salt lithium hexafluorophosphate (LiPF6) 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.

[0075] (4) Preparation of the first electrode assembly and the second electrode assembly: The separator, the negative electrode sheet, the separator, and the positive electrode sheet are stacked in sequence to form a laminate structure, and then the four corners of the entire laminate structure are fixed to obtain a sheet 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.

[0076] (5) Preparation of the isolation member: The packaging layer material polypropylene (PP, melting point 140°C) is uniformly dispersed in the dispersant N-methylpyrrolidone (NMP) to prepare a PP suspension; the PP suspension is coated on both sides of an aluminum layer with a thickness of 50 μm using a glue coating machine; and then the layer is dried at 130°C, wherein the thickness of the PP packaging layer on one side of the aluminum layer is 25 μm, and the total thickness of the isolation member is 100 μm.

[0077] (6) Assembly of electrode assembly: Place the aluminum-plastic film (150 μm thick) formed by punching holes in an assembly fixture with the pit side facing upward, place the first electrode assembly in the pit, and set the ear glue in the area corresponding to the ear of the first electrode assembly at the edge of the aluminum-plastic film, then place the separator on the first electrode assembly so that the edges are aligned, and apply external force to compact to obtain an assembled semi-finished product. Place the assembled semi-finished product in an assembly fixture with the separator side facing upward, place the second electrode assembly on the separator so that the edges are aligned, and apply external force to compact, then cover the second electrode assembly with another aluminum-plastic film formed by punching holes with the pit side facing downward, and set the ear glue in the area corresponding to the ear of the second electrode assembly at the edge of the aluminum-plastic film. Lead the positive and negative pole ears of the first electrode assembly and the second electrode assembly out of the aluminum-plastic film, and perform top and side sealing by hot pressing to obtain an assembled electrode assembly. Among them, the overlapping projection area ratio S3 / S1 of the first pole piece assembly and the second pole piece assembly is 90.2%, the single-side offset distance d1 in the width direction of the positive electrode active material layer is 4 mm, and the single-side offset distance d3 in the length direction of the positive electrode active material layer is 0 mm.

[0078] (7) Liquid injection packaging: The electrolyte is injected into each cavity separately, and then sealed after hot pressing, formation, and degassing.

[0079] (8) Series connection: The negative electrode tab of the first electrode assembly and the positive electrode tab of the second electrode assembly are connected together by laser welding to achieve series connection, and the lithium-ion battery assembly is completed.

[0080] Example 2

[0081] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode sheet assembly and the second electrode sheet assembly is 92.7%, and the single-side offset distance d1 in the width direction of the positive electrode active material layer is 3 mm.

[0082] Example 3

[0083] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode assembly and the second electrode assembly is 95.1%, and the single-side misalignment distance d1 in the width direction of the positive electrode active material layer is 2 mm.

[0084] Example 4

[0085] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode assembly and the second electrode assembly is 97.6%, and the single-side misalignment distance d1 in the width direction of the positive electrode active material layer is 1 mm.

[0086] Example 5

[0087] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode sheet assembly and the second electrode sheet assembly is 100%, and the single-side offset distance d1 in the width direction of the positive electrode active material layer is 0 mm.

[0088] Example 6

[0089] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode sheet assembly and the second electrode sheet assembly is 91.2%, the single-side misalignment distance d1 in the width direction of the positive electrode active material layer is 3 mm, and the single-side misalignment distance d3 in the length direction of the positive electrode active material layer is 1 mm.

[0090] Example 7

[0091] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode sheet assembly and the second electrode sheet assembly is 90.4%, the single-side misalignment distance d1 in the width direction of the positive electrode active material layer is 3 mm, and the single-side misalignment distance d3 in the length direction of the positive electrode active material layer is 1.5 mm.

[0092] Example 8

[0093] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode sheet assembly and the second electrode sheet assembly is 90.4%, the single-side misalignment distance d1 in the width direction of the positive electrode active material layer is 2 mm, and the single-side misalignment distance d3 in the length direction of the positive electrode active material layer is 3 mm.

[0094] Example 9

[0095] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode sheet assembly and the second electrode sheet assembly is 91.2%, the single-side misalignment distance d1 in the width direction of the positive electrode active material layer is 1 mm, and the single-side misalignment distance d3 in the length direction of the positive electrode active material layer is 4 mm.

[0096] Example 10

[0097] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode sheet assembly and the second electrode sheet assembly is 90.4%, the single-side misalignment distance d1 in the width direction of the positive electrode active material layer is 1 mm, and the single-side misalignment distance d3 in the length direction of the positive electrode active material layer is 4.5 mm.

[0098] Comparative Example 1

[0099] The difference from Example 1 is that in the electrode assembly step, the overlapping projection area ratio S3 / S1 of the first electrode sheet assembly and the second electrode sheet assembly is 87.8%, and the single-side offset distance d1 in the width direction of the positive electrode active material layer is 5 mm.

[0100] Test method:

[0101] Safety test: The lithium-ion battery is charged to 8.4V at 1C constant current at 25±3℃, and then charged to a current of 0.05C at a constant voltage of 8.4V to fully charge the lithium-ion battery, and then discharged to 6.0V at 1C current, and the cycle is repeated. After charging to the full charge state for the 200th cycle, the lithium-ion battery is disassembled, and one side edge of the negative electrode sheet of one of the electrode assemblies in the width direction or length direction is observed. If a dark gray metal layer exists for more than 10% of the length of the side edge, it is defined as severe lithium deposition; if a light gray metal layer exists for 5-10% of the length of the side edge, it is defined as slight lithium deposition; if a light gray metal layer exists for less than 5% of the length of the side edge or no light gray metal layer exists, it is defined as no lithium deposition.

[0102] Table 1 Statistics of lithium deposition in electrochemical devices with different overlapping projection areas

[0103]

[0104] It can be seen from the comparative example 1 and the examples 1-10 in the above table 1 that when other test conditions are the same, the overlapping projected areas S3 / S1 and S3 / S1 in the examples 1-10 are ≥90%, which can make the electrode assembly more evenly pressed during the hot pressing process, which is conducive to promoting the uniform formation of the SEI film, thereby reducing the risk of lithium precipitation of the electrode assembly in the lithium-ion battery. At the same time, it can be seen from the comparison between the examples 2-8 and the examples 1, 9-10 that when the misalignment between the positive active material layers of the two electrode assemblies further satisfies d1≤3mm and / or d3≤3mm, the risk of lithium precipitation at the edge of the negative electrode sheet in the electrode assembly can be further reduced. This is because d1≤3mm and / or d3≤3mm can make the positive active area of ​​the first electrode sheet assembly and the second electrode sheet assembly that effectively participates in the deintercalation of lithium ions less misaligned, thereby promoting the uniform formation of the negative electrode SEI film on the opposite side, thereby further reducing the risk of lithium analysis of the non-overlapping active parts of the first electrode sheet assembly and the second electrode sheet assembly.

[0105] The present application also provides an electronic device, which includes the electrochemical device 100 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, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor, etc.

[0106] It should be noted that the preferred embodiments of the present application are given in the specification and drawings of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described in the specification. These embodiments are not used as additional limitations on the content of the present application. The purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive. In addition, the above-mentioned technical features continue to be combined with each other to form various embodiments not listed above, which are all regarded as the scope of the description of the present application; further, for ordinary technicians in this field, they can be improved or transformed according to the above description, and all these improvements and transformations should belong to the scope of protection of the claims attached to the present application.

Claims

1. An electrochemical device, characterized in that: include: A housing having a first cavity and a second cavity; A first electrode assembly, comprising a first pole piece assembly, wherein the first pole piece assembly is accommodated in the first cavity; A second electrode assembly, comprising a second pole piece assembly, wherein the second pole piece assembly is accommodated in the second cavity; A separator, disposed between the first electrode assembly and the second electrode assembly; The first electrode assembly, the separator and the second electrode assembly are sequentially arranged along a first direction. Along the first direction, the area of ​​a first projection of the first electrode assembly on the separator is S1, the area of ​​a second projection of the second electrode assembly on the separator is S2, and the area of ​​an overlapping portion of the first projection and the second projection is S3, satisfying S3 / S1≥0.9 and S3 / S2≥0.9; The first electrode sheet assembly comprises a first positive electrode sheet, the first positive electrode sheet comprises a first positive current collector and a first positive active material layer located on a surface of the first positive current collector, and along a width direction of the first positive active material layer, the first positive active material layer comprises a first edge and a second edge opposite to each other; The second electrode sheet assembly includes a second positive electrode sheet, the second positive electrode sheet includes a second positive current collector and a second positive active material layer located on the surface of the second positive current collector, along the width direction of the second positive active material layer, the second positive active material layer includes a third edge and a fourth edge relative to each other; observed along the first direction, the first edge is adjacent to the third edge, the second edge is adjacent to the fourth edge, the distance between the first edge and the third edge is d1, the distance between the second edge and the fourth edge is d2, satisfying: d1≤3mm, d2≤3mm.

2. The electrochemical device according to claim 1, characterized in that S3 / S1≥0.95, S3 / S2≥0.

95.

3. The electrochemical device according to claim 1, characterized in that The first electrode sheet assembly further includes a first negative electrode sheet, the first negative electrode sheet includes a first negative current collector and a first negative active material layer located on a surface of the first negative current collector, and along a width direction of the first positive active material layer, the first negative active material layer includes a first extension area that exceeds the first positive active material layer; The second electrode sheet assembly also includes a second negative electrode sheet, which includes a second negative electrode collector and a second negative electrode active material layer located on the surface of the second negative electrode collector. Along the width direction of the second positive electrode active material layer, the second negative electrode active material layer includes a second extension area that exceeds the second positive electrode active material layer.

4. The electrochemical device according to claim 3, characterized in that The first positive electrode plate also includes a first insulating layer located on the surface of the first positive electrode collector, and when viewed along the first direction, the first insulating layer at least partially overlaps with the first extension area; and / or, the second positive electrode plate also includes a second insulating layer located on the surface of the second positive electrode collector, and when viewed along the first direction, the second insulating layer at least partially overlaps with the second extension area.

5. The electrochemical device according to claim 1, characterized in that The first pole sheet assembly and the second pole sheet assembly are a stacked structure; along the length direction of the first positive electrode active material layer, the first positive electrode active material layer includes a relative fifth edge and a sixth edge; along the length direction of the second positive electrode active material layer, the second positive electrode active material layer includes a relative seventh edge and an eighth edge; observed along the first direction, the fifth edge is adjacent to the seventh edge, the sixth edge is adjacent to the eighth edge, the distance between the fifth edge and the seventh edge is d3, and the distance between the sixth edge and the eighth edge is d4, satisfying: d3≤4mm, d4≤4mm.

6. The electrochemical device according to claim 1, characterized in that When viewed along the first direction, the first edge coincides with the third edge; and / or, Viewed along the first direction, the second edge coincides with the fourth edge.

7. The electrochemical device according to claim 5, characterized in that When viewed along the first direction, the fifth edge coincides with the seventh edge; and / or, When viewed along the first direction, the sixth edge coincides with the eighth edge.

8. The electrochemical device according to claim 1, characterized in that At least one of the following conditions is met: (a) the isolation member comprises a first encapsulation layer, a second encapsulation layer and an intermediate layer, wherein the intermediate layer is located between the first encapsulation layer and the second encapsulation layer; (b) the first electrode assembly further includes a first electrode tab, the second electrode assembly includes a second electrode tab, and the first electrode tab and the second electrode tab both extend from the same side of the housing; (c) The first electrode assembly and the second electrode assembly are connected in series.

9. An electronic device comprising the electrochemical device according to any one of claims 1 to 8.

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