Electrochemical devices and electronic devices

Abstract

An electrochemical device includes a housing and an electrode assembly and an electrolyte disposed within the housing. The electrode assembly includes electrodes and a separator membrane disposed between adjacent electrodes. The separator membrane includes a porous substrate and a first adhesive layer disposed on the surface of the porous substrate. The first adhesive layer includes a plurality of spaced-apart first adhesive regions. The thickness direction of the electrode assembly is defined as a first direction. In this first direction, the circumscribed rectangle of the projection of the electrode assembly has a diagonal and a first side, the angle between the diagonal and the first side is θ1, and the angle between the projection of the first adhesive region and the first side is θ2, where θ1 / 2 ≤ θ2 ≤ (θ1 / 2 + 45°). This application also provides an electronic device having the above-described electrochemical device. The electrochemical device of this application can balance interfacial adhesion and electrolyte transport capacity, and has improved resistance to deformation and cycle performance.

Description

Technical Field

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

[0002] Electrochemical devices (such as batteries) are widely used in electronic devices such as electronic mobile devices, power tools and electric vehicles. With the development of such electronic devices, people have increasingly stringent requirements on the cycle performance of electrochemical devices. Summary of the invention

[0003] In order to solve the deficiencies of the prior art, it is necessary to provide an electrochemical device.

[0004] In addition, it is also necessary to provide an electronic device having the above electrochemical device.

[0005] The present application provides an electrochemical device, including a shell and an electrode assembly and an electrolyte arranged in the shell. The electrode assembly includes a pole piece and a separator arranged between adjacent pole pieces. The separator includes a porous substrate and a first bonding layer arranged on the surface of the porous substrate. The first bonding layer includes a plurality of first bonding areas arranged at intervals. The thickness direction of the electrode assembly is defined as a first direction. In the first direction, the circumscribed rectangle of the projection of the electrode assembly has a diagonal and a first side, the angle between the diagonal and the first side is θ1, the angle between the projection of the first bonding area and the first side is θ2, and θ1 / 2≤θ2≤(θ1 / 2+45°).

[0006] The first bonding layer of the isolation membrane provided in the present application includes a plurality of first bonding areas arranged at intervals, which improves the interfacial bonding force between the isolation membrane and the electrode sheet, and at the same time, the gap between two adjacent first bonding areas reserves space for electrolyte transmission, so that the requirements of interfacial bonding force and electrolyte transmission can be taken into account at the same time. Furthermore, the present application sets θ1 / 2≤θ2≤(θ1 / 2+45°), so that the first bonding area is inclined relative to the first side of the circumscribed rectangle of the projection of the electrode assembly in the thickness direction, so that the bonding force of the first bonding layer is continuously distributed in the direction of the first side, thereby improving the anti-deformation ability of the electrochemical device; at the same time, by setting the relationship between θ2 and θ1, the inclination angle of the first bonding area is within a certain deviation range compared to the inclination angle of the diagonal of the circumscribed rectangle, so that each first bonding area can form a relatively stable triangular fixed relationship with the end and side of the electrode assembly, further improving the anti-deformation ability of the electrochemical device and improving the cycle performance.

[0007] In some possible implementations, the separator membrane further includes a second adhesive layer, and the porous substrate is located between the first adhesive layer and the second adhesive layer. The second adhesive layer includes a plurality of second adhesive regions arranged at intervals. Therefore, the gap between two adjacent second adhesive regions can also serve as a channel for electrolyte transmission, further improving the electrolyte transmission performance. In the first direction, the included angle between the projection of the second adhesive region and the projection of the first adhesive region is θ3, where 0 < θ3 < 180°. Therefore, the second adhesive region is also inclined, so that the adhesive force of the second adhesive layer is continuously distributed in the direction of the first side, further improving the anti-deformation ability of the electrochemical device.

[0008] In some possible implementations, θ3 = 180° - 2θ2. By further defining the relationship between θ3 and θ2, the anti-deformation ability of the electrode assembly can be further improved.

[0009] In some possible implementations, θ2 = θ1. By further defining θ2 to be equal to θ1, the most stable triangular fixing relationship is formed between each first adhesive region and the second end portion and the side portion of the electrode assembly, thereby further improving the anti-deformation ability of the electrode assembly.

[0010] In some possible implementations, the direction from one first adhesive region to another adjacent first adhesive region is defined as the second direction. In the second direction, the width of the first adhesive region is d1 mm, and the distance between adjacent first adhesive regions is d2 mm, and d1 and d2 satisfy: 0.1 < d1 < 10, 0.1 < d2 < 10. Among them, when d1 is too small, the adhesive force between the first adhesive layer and the pole piece decreases, and the anti-deformation ability also decreases accordingly; when d1 is too large, d2 correspondingly decreases, so that the space available for electrolyte transmission decreases and the electrolyte infiltration is poor. When d2 is too small, the space available for electrolyte transmission also decreases and the electrolyte infiltration is poor; when d2 is too large, d1 correspondingly decreases, and the adhesive force between the first adhesive layer and the pole piece also decreases, and the anti-deformation ability also decreases accordingly.

[0011] In some possible implementations, the direction from one first adhesive region to another adjacent first adhesive region is defined as the second direction. In the second direction, the width of the first adhesive region is d1 mm, and the distance between adjacent first adhesive regions is d2 mm, and d1 and d2 satisfy: 0.1 < d1 / d2 < 5. Among them, when d1 / d2 is too small, the area ratio of the first adhesive region decreases, and the adhesive force between the first adhesive layer and the pole piece also decreases, and the anti-deformation ability also decreases accordingly; when d1 / d2 is too large, the area ratio of the first adhesive region increases, and the space available for electrolyte transmission also decreases and the electrolyte infiltration is poor.

[0012] In some possible implementation manners, in the first direction, the thickness of the first adhesive layer is t1 μm, and 0.15 < t1d1 / (d1 + d2) < 2. Wherein, when t1d1 / (d1 + d2) is too small, the proportion of the diffusion area of the first adhesive layer after being heated and softened decreases, which will also cause the adhesive force between the first adhesive layer and the electrode tab to decrease, and the anti-deformation ability will also decrease accordingly; when t1d1 / (d1 + d2) is too large, the proportion of the diffusion area of the first adhesive layer after being heated and softened increases, which also makes the space available for electrolyte transmission decrease, resulting in poor electrolyte infiltration.

[0013] In some possible implementation manners, in the first direction, the thickness of the first adhesive layer is t1 μm, and 0.1 ≤ t1 ≤ 6. Wherein, when t1 is too small, the adhesive force between the first adhesive layer and the electrode tab decreases; when t1 is too large, the air permeability of the entire separator will be reduced, resulting in poor electrolyte transmission.

[0014] In some possible implementation manners, multiple first adhesive regions are parallel to each other. Wherein, when multiple first adhesive regions are parallel to each other, there may be a certain included angle between two adjacent first adhesive regions, and the included angle is from -5° to +5°.

[0015] In some possible implementation manners, each first adhesive region is continuously or discontinuously arranged. Wherein, the gap in each discontinuously arranged first adhesive region can also serve as a channel for electrolyte transmission, further improving the electrolyte transmission performance.

[0016] In some possible implementation manners, in the first direction, the projection of the electrode assembly includes a rectangle, an arc, or an L shape. Therefore, the electrochemical device can be arranged according to the internal space shape of the electronic device, so as to make full use of the space inside the electronic device and improve the capacity of the electrochemical device.

[0017] In some possible implementation manners, the electrode assembly further includes an electrode tab electrically connected to the electrode tab. In the first direction, the projection of the electrode tab extends from the opposite side of the first side, which is convenient for the electrode tab to be electrically connected to an external component.

[0018] In some possible implementation manners, the electrode assembly includes a winding structure or a stacking structure.

[0019] In some possible implementation manners, the porous substrate includes any one of the following polymers or a polymer film, a multilayer polymer film, or a non-woven fabric formed by a mixture of two or more of the following: polyolefin, polyvinylidene fluoride, polyethylene terephthalate, cellulose, polyimide, polyamide, spandex, or poly(p-phenylene terephthalamide). These polymers have high thermal stability, and it is easy to coat the first adhesive layer on the porous substrate. In addition, these polymers have good toughness and are easy to bend.

[0020] In some possible implementations, the first bonding layer includes a bonding material, and the bonding material includes at least one of a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and trichloroethylene, polymethyl methacrylate, polyacrylic acid, polyacrylic acid salt, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, a copolymer of ethylene-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, a copolymer of acrylonitrile-styrene-butadiene, polyvinyl alcohol, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene, a copolymer of styrene-butadiene, or polyvinylidene fluoride. These polymers can produce a strong bonding effect to bond the isolation membrane and the pole piece together.

[0021] The present application also provides an electronic device, comprising the above electrochemical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the overall structure of an electrochemical device provided in one embodiment of the present application.

[0023] Figure 2 for Figure 1 An electrode assembly of an electrochemical device is shown as a front view in some embodiments.

[0024] Figure 3 for Figure 1 The electrode assembly of the electrochemical device shown is a front view of some other embodiments.

[0025] Figure 4 for Figure 1 The electrode assembly of the electrochemical device shown is a front view in some other embodiments.

[0026] Figure 5 for Figure 2 A top view of an electrode assembly in some embodiments is shown.

[0027] Figure 6 for Figure 2 Top views of electrode assemblies in other embodiments are shown.

[0028] Figure 7 for Figure 5 The electrode assembly is shown in a cross-sectional view along V-II-VII.

[0029] Figure 8 for Figure 2 A separator of an electrode assembly is shown as a front view in some embodiments.

[0030] Fig. 9 for Figure 2 The separator of the electrode assembly is shown as a front view in some other embodiments.

[0031] Fig.10 for Figure 2 A back view of the separator of the electrode assembly is shown.

[0032] Fig.11 A schematic diagram of the structure of an electronic device provided in one embodiment of the present application.

[0033] Main component symbols

[0034] Electronic device 1

[0035] Housing 10

[0036] Main body 11

[0037] Packaging unit 12

[0038] Electrode assembly 20

[0039] The first pole piece 21

[0040] The second pole piece 22

[0041] Isolation film 23

[0042] First tab 30

[0043] Second pole ear 40

[0044] Electrochemical device 100

[0045] Top 111

[0046] Bottom 112

[0047] Upper surface 113

[0048] First side 114

[0049] Second side 115

[0050] Projection 200

[0051] First side 201

[0052] Second side 202

[0053] Diagonal 203

[0054] First current collector 211

[0055] First active material layer 212

[0056] Second fluid collector 221

[0057] Second active material layer 222

[0058] Porous substrate 230

[0059] First bonding layer 231

[0060] Second adhesive layer 232

[0061] First bonding area 2311

[0062] Second bonding area 2321

[0063] Circumscribed rectangle R

[0064] Gap G1, G2, G3

[0065] First direction D1

[0066] Second direction D2

[0067] Third direction D3

[0068] Fourth direction D4

[0069] Width d1

[0070] Distance d2

[0071] Thickness t1

[0072] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0073] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0074] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0075] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0076] Electrochemical devices usually include pole pieces and separators disposed between adjacent pole pieces. Separators with high bonding properties are generally used to tightly bond adjacent pole pieces to the separators, thereby ensuring the interfacial bonding between the separators and the pole pieces and reducing expansion deformation during gas production inside the electrochemical device. However, the provision of a separator with high bonding properties will result in a smaller gap between the separator and the pole piece, making it more difficult for the electrolyte to fully infiltrate the pole piece. Especially for wound batteries, the corner area of ​​the electrode assembly is more prone to uneven electrolyte distribution, resulting in purple spots of lithium precipitation during the cycle, affecting the cycle performance of the electrochemical device.

[0077] See also Figure 1 In one embodiment of the present application, an electrochemical device 100 is provided, comprising a housing 10, an electrode assembly 20 (in Figure 5 and Figure 6 ) and an electrolyte, a first electrode tab 30 and a second electrode tab 40. Figure 5 and Figure 6 The electrochemical device 100 is shown to include one electrode assembly 20 , but it is understood that in order to achieve high voltage output, the electrochemical device 100 may also include a plurality of electrode assemblies 20 connected in series, and the present application is not limited thereto.

[0078] like Figure 5 and Figure 6 As shown, the electrode assembly 20 includes a pole piece and a separator 23 disposed between adjacent pole pieces. Among them, the pole piece includes a first pole piece 21 and a second pole piece 22, and the separator 23 is disposed between the first pole piece 21 and the second pole piece 22. The separator 23 is used to prevent the first pole piece 21 and the second pole piece 22 from directly contacting and short-circuiting. In some embodiments, the electrode assembly 20 is obtained by winding the first pole piece 21, the separator and the second pole piece 22, that is, the electrode assembly 20 is a winding structure. In other embodiments, the electrode assembly 20 can also be obtained by stacking the first pole piece 21, the separator and the second pole piece 22, that is, the electrode assembly 20 is a stacked structure.

[0079] The first pole tab 30 and the second pole tab 40 are electrically connected to the electrode assembly 20, respectively, and extend from the housing 10 to connect to external elements (not shown). Specifically, the first pole sheet 21 includes a first current collector 211 and a first active material layer 212 disposed on the surface of the first current collector 211, and the first pole tab 30 is electrically connected to the first current collector 211. The second pole sheet 22 includes a second current collector 221 and a second active material layer 222 disposed on the surface of the second current collector 221, and the second pole tab 40 is electrically connected to the second current collector 221. In some embodiments, the first pole sheet 21 is a positive pole sheet, and the second pole sheet 22 is a negative pole sheet.

[0080] like Figure 1As shown, the shell 10 can be a packaging bag obtained by packaging with a packaging film. That is, the electrochemical device 100 can be a soft-pack battery. At this time, the shell 10 includes a main body 11 and a packaging part 12. The main body 11 is used to accommodate the electrode assembly 20 and the electrolyte. The packaging part 12 is connected to the main body 11, and the first pole ear 30 and the second pole ear 40 extend out of the packaging part 12. Among them, the main body 11 includes a top surface 111, a bottom surface 112, an upper surface 113, a lower surface (not shown), a first side surface 114 and a second side surface 115. The top surface 111 and the bottom surface 112 are opposite. The upper surface 113 and the lower surface are opposite, and are connected between the top surface 111 and the bottom surface 112. The first side surface 114 and the second side surface 115 are opposite, and are connected between the top surface 111 and the bottom surface 112. The packaging part 12 is connected to the top surface 111. In other embodiments, the electrochemical device 100 is not limited to a soft-pack battery, but may also be a steel shell battery or an aluminum shell battery, etc., which is not limited in the present application.

[0081] See also Figure 7 The isolation film 23 includes a porous substrate 230 and a first bonding layer 231 disposed on the surface of the porous substrate 230 , and the first bonding layer 231 bonds the first electrode piece 21 . In another embodiment, the first bonding layer 231 may also bond the second electrode piece 22 .

[0082] Please refer to Figure 8 , the first bonding layer 231 includes a plurality of first bonding areas 2311 arranged at intervals. That is, there is a gap G1 between two adjacent first bonding areas 2311. In some embodiments, the plurality of first bonding areas 2311 are arranged in parallel. It can be understood that when two elements are arranged in parallel, there may be a certain angle between the two elements, the angle being -5° to +5°, so it is not limited that the two elements must be strictly parallel.

[0083] The thickness direction (i.e., the direction from the upper surface 113 to the lower surface), the length direction (i.e., the direction from the bottom surface 112 to the top surface 111), and the width direction (i.e., the direction from the first side surface 114 to the second side surface 115) of the electrode assembly 20 are defined as the first direction D1, the third direction D3, and the fourth direction D4, respectively. The third direction D3 is the direction in which the first electrode tab 30 and the second electrode tab 40 extend. Please refer to Figure 2 In some embodiments, in the first direction D1, the projection 200 of the electrode assembly 20 is a rectangle having a first side 201, a second side 202, and a diagonal line 203 connecting the first side 201 and the second side 202.

[0084] Among them, Figure 2As shown, the electrode assembly 20 has a first end 20a, a second end 20b, and a side portion 20c connected between the first end 20a and the second end 20b. The first end 20a is the head of the electrode assembly 20 provided with the first pole tab 30 and the second pole tab 40, and the second end 20b is the tail of the electrode assembly 20 opposite to the head. The projection of the second end 20b in the first direction D1 forms a first side 201, and the projection of the side portion 20c in the first direction D1 forms a second side 202. In this case, in the first direction D1, the projections of the first pole tab 30 and the second pole tab 40 extend from the opposite side of the first side 201, so that the first pole tab 30 and the second pole tab 40 are convenient for electrically connecting the external components.

[0085] Please also read Figure 2 and Figure 8 , the angle between the diagonal line 203 and the first side 201 is defined as θ1, because the diagonal line 203 of the circumscribed rectangle R is inclined to the first side 201, that is, 0°<θ1<90°. The angle between the projection of the first bonding area 2311 and the first side 201 is θ2, and θ1 and θ2 satisfy the following relationship: θ1 / 2≤θ2≤(θ1 / 2+45°).

[0086] like Figure 8 As shown, in some embodiments, each first bonding area 2311 can be arranged in a strip shape on the surface of the porous substrate 230. That is, each first bonding area 2311 is arranged continuously. In this case, the projection of each first bonding area 2311 is also in a strip shape, and the angle θ2 between the projection of the first bonding area 2311 and the first edge 201 is the angle between the strip projection and the first edge 201. Fig. 9 As shown, in another embodiment, each first bonding area 2311 may also be intermittently arranged, such as being arranged in a plurality of blocks or islands on the surface of the porous substrate 230. In this case, the projection of each first bonding area 2311 is also in a plurality of blocks or islands, and the angle θ2 between the projection of the first bonding area 2311 and the first side 201 is the angle between the connecting line of the block or island projection and the first side 201.

[0087] Therein, each of the intermittently arranged first bonding areas 2311 is also provided with a gap G2, which can serve as a channel for electrolyte transmission, thereby further improving the electrolyte transmission performance.

[0088] The first bonding layer 231 of the isolation film provided in the present application includes a plurality of first bonding areas 2311 arranged at intervals. The first bonding area 2311 can bond the first pole piece 21 or the second pole piece 22, improve the interfacial bonding force between the isolation film 23 and the pole piece, reduce the expansion deformation when the electrochemical device 100 produces gas, that is, improve the anti-deformation ability of the electrochemical device 100, reduce the risk of deformation and structural damage of the electrode assembly, and keep the entire conductive network in the electrode assembly 20 unobstructed, thereby improving the cycle performance of the electrochemical device 100. At the same time, there is a gap G1 between two adjacent first bonding areas 2311, thereby reserving space for electrolyte transmission. After injection, the electrolyte can flow through the above gap G1 and fully infiltrate the pole piece, which also helps to improve the cycle performance of the electrochemical device 100. The electrochemical device 100 of the present application can take into account the requirements of interfacial bonding force and electrolyte transmission at the same time.

[0089] Furthermore, the present application sets θ1 / 2≤θ2≤(θ1 / 2+45°). Since 0°<θ1<90°, 0°<θ2<90° makes the projection of the first bonding area 2311 also tiltedly set on the first side 201. Therefore, the bonding force of the first bonding layer 231 is continuously distributed in the direction of the first side 201, that is, the bonding force between the isolation film 23 and the pole piece is continuously distributed in the direction of the first side 201, thereby improving the anti-deformation ability of the electrochemical device 100, thereby improving the cycle performance. At the same time, by setting the relationship between θ2 and θ1, the inclination angle of the first bonding area 2311 is also within a certain deviation range compared to the inclination angle of the diagonal 203 of the circumscribed rectangle R. Therefore, each first bonding area 2311 can form a relatively stable triangular fixed relationship with the second end 20b and the side 20c of the electrode assembly 20, which can further improve the anti-deformation ability of the electrochemical device 100, thereby improving the cycle performance.

[0090] It is understandable that in order to improve the competitiveness of electronic devices, some consumer electronic devices are turning to special shapes, and electrochemical devices with special shapes can make full use of the irregular space in such electronic devices, thereby increasing the capacity of the entire electrochemical device. Therefore, in the present application, in the first direction D1, the projection 200 of the electrode assembly 20 is not limited to a rectangle, but can also be other special shapes. Figure 3 and Figure 4 As shown, in another embodiment, when the electrode assembly 20 is a laminated structure, in the first direction D1, the projection 200 of the electrode assembly 20 is arc-shaped or L-shaped. At this time, the circumscribed rectangle R of the projection 200 of the electrode assembly 20 also has a first side 201, a second side 202, and a diagonal line 203 connecting the first side 201 and the second side 202. It can be understood that, as Figure 2 As shown, when the projection 200 of the electrode assembly 20 is a rectangle, the circumscribed rectangle R of the projection 200 is the projection 200 itself.

[0091] In some embodiments, the porous substrate 230 includes a polymer film, a multilayer polymer film, or a non-woven fabric formed by any one of the following polymers or a mixture of two or more thereof: polyolefin, polyvinylidene fluoride, polyethylene terephthalate, cellulose, polyimide, polyamide, spandex, and polyphenylene phthalamide. Such polymers have high thermal stability and are easy to surface treat, so that the first bonding layer 231 is easy to coat on the porous substrate 230. In addition, such polymers have good toughness and are easy to bend.

[0092] The first bonding layer 231 includes a bonding material, which includes at least one of the following polymers: a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and trichloroethylene, polymethyl methacrylate, polyacrylic acid, polyacrylic acid salt, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, a copolymer of ethylene-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, a copolymer of acrylonitrile-styrene-butadiene, polyvinyl alcohol, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene, a copolymer of styrene-butadiene or polyvinylidene fluoride. These polymers can produce a strong bonding effect to bond the isolation membrane 23 and the first pole piece 21 or the second pole piece 22 together.

[0093] like Figure 7 As shown, in some embodiments, the isolation film 23 further includes a second bonding layer 232, and the porous substrate 230 is located between the first bonding layer 231 and the second bonding layer 232. When the first bonding layer 231 bonds the first electrode 21, the second bonding layer 232 bonds the second electrode 22. Fig.10 , the second bonding layer 232 includes a plurality of second bonding areas 2321 arranged at intervals. That is, there is also a gap G3 between two adjacent second bonding areas 2321, which serves as a channel for electrolyte transmission. Therefore, the arrangement of the second bonding area 2321 further improves the infiltration effect of the electrolyte. In some embodiments, the plurality of second bonding areas 2321 are arranged in parallel.

[0094] In the first direction D1, the angle between the projection 200 of the second bonding area 2321 and the projection 200 of the first bonding area 2311 is θ3, and 0°<θ3<180°. That is, the second bonding area 2321 is also inclined to the first side 201. Therefore, the bonding force of the second bonding layer 232 is also continuously distributed in the direction of the first side 201, further improving the anti-deformation ability of the electrochemical device 100.

[0095] Further, θ2 and θ3 may also satisfy the following relationship: θ3 = 180° - 2θ2. By further defining the relationship between θ3 and θ2, the anti-deformation ability of the electrode assembly 20 can be further improved.

[0096] In some embodiments, θ2 = θ1. By further defining that θ2 is equal to θ1, the most stable triangular fixing relationship is formed between each first bonding area 2311 and the second end portion 20b and the side portion 20c of the electrode assembly 20, thereby further improving the anti-deformation ability of the electrode assembly 20.

[0097] As Figure 8 shown, in some embodiments, the direction from one first bonding area 2311 to another adjacent first bonding area 2311 is defined as the second direction D2. In the second direction D2, the width of the first bonding area 2311 is d1 mm, and the distance between adjacent first bonding areas 2311 is d2 mm. d1 and d2 satisfy: 0.1 < d1 < 10, 0.1 < d2 < 10. Among them, when d1 is too small, the bonding force between the first bonding layer 231 and the electrode sheet decreases, and the anti-deformation ability also decreases accordingly; when d1 is too large, d2 correspondingly decreases when the area of the electrode sheet is certain, so that the space available for electrolyte transmission decreases and the electrolyte infiltration is poor. When d2 is too small, the space available for electrolyte transmission also decreases and the electrolyte infiltration is poor; when d2 is too large, d1 correspondingly decreases when the area of the electrode sheet is certain, and the bonding force between the first bonding layer 231 and the electrode sheet also decreases, and the anti-deformation ability also decreases accordingly.

[0098] In some embodiments, d1 and d2 satisfy: 0.1 < d1 / d2 < 5. Among them, when d1 / d2 is too small, the area ratio of the first bonding area 2311 decreases, and the bonding force between the first bonding layer 231 and the electrode sheet also decreases, and the anti-deformation ability also decreases accordingly; when d1 / d2 is too large, the area ratio of the first bonding area 2311 increases, and the space available for electrolyte transmission also decreases and the electrolyte infiltration is poor.

[0099] In some embodiments, in the first direction D1, the thickness of the first bonding layer 231 is t1 μm, and 0.15 < t1d1 / (d1 + d2) < 2. Among them, when t1d1 / (d1 + d2) is too small, the area ratio of the diffusion area of the first bonding layer 231 after being heated and softened decreases, and the bonding force between the first bonding layer 231 and the electrode sheet also decreases, and the anti-deformation ability also decreases accordingly; when t1d1 / (d1 + d2) is too large, the area ratio of the diffusion area of the first bonding layer 231 after being heated and softened increases, and the space available for electrolyte transmission also decreases and the electrolyte infiltration is poor.

[0100] Please refer to Figure 7 and Figure 8, in some embodiments, 0.1≤t1≤6. When t1 is too small, the bonding force between the first bonding layer 231 and the electrode is reduced; when t1 is too large, the overall air permeability of the isolation film 23 is reduced, resulting in poor electrolyte transmission.

[0101] The electrochemical device 100 of the present application may be any type of primary battery, secondary battery, fuel cell, solar cell and capacitor (such as supercapacitor). In particular, the secondary battery may be a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery and a lithium ion polymer secondary battery.

[0102] See also Fig.11 In one embodiment of the present application, an electronic device 1 is provided, and the electronic device 1 includes the electrochemical device 100 as described above. The electronic device 1 of the present application can be, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic 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 electronic source, a motor, a car, a motorcycle, a power 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.

[0103] The present application is described in detail below through specific embodiments and comparative examples. Among them, the present application is described by taking the electrochemical device as a soft-pack battery as an example and combining the specific preparation process and testing method. Those skilled in the art should understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.

[0104] Comparative Example 1

[0105] The isolation film is coated on both sides and has a first adhesive layer and a second adhesive layer. The electrode assembly is obtained by stacking and winding the first pole piece, the second pole piece and the isolation film in sequence. In the first direction, the projection of the electrode assembly is a rectangle, and the angle θ1 between the diagonal of the projection and the first side is 45°; the angle θ2 between the projection of the first adhesive area of ​​the first adhesive layer and the first side is 90°; the angle θ3 between the projection of the second adhesive area of ​​the second adhesive layer and the projection of the first adhesive area is 23°. The width d1 of the first adhesive area is 0.21 mm, the distance d2 between adjacent first adhesive areas is 0.04 mm, and the thickness t1 of the first adhesive area is 2 μm.

[0106] The electrode assembly and the electrolyte are packaged in an aluminum-plastic film to obtain an electrochemical device.

[0107] Comparative Examples 2-5 and Examples 1-12

[0108] The difference from Comparative Example 1 is that: the values ​​of θ1, θ2 or θ3 are different; the second bonding layer is omitted from the isolation film; or, the first bonding layer and the second bonding layer are uniformly coated (that is, the bonding layer is uniformly coated on the entire surface of the porous substrate).

[0109] The electrochemical devices of each embodiment and comparative example were subjected to a capacity retention test and a three-point bending test, and the corresponding test results were recorded in Table 1. The steps of the capacity retention test include: in a high-temperature furnace at 45 degrees Celsius, the electrochemical device is charged to 4.43 V at a constant current of 1 C, then charged to 0.05 C at a constant voltage, then left to stand for 5 minutes, and then discharged to 3.0 V at 0.7 C. This discharge capacity is the first discharge capacity of the battery, which is calculated as 100%. The above charge and discharge steps are cycled 400 times in sequence, and the ratio of the discharge capacity of the electrochemical device after the cycle to the first capacity multiplied by 100% is the capacity retention rate.

[0110] The steps of the three-point bending test include: in a dry environment, fix the electrochemical device on two supporting points with a certain distance, and use a pressure head to apply pressure to the electrochemical device at the midpoint of the two supporting points. Then, record the displacement of the pressure head and the pressure on the electrochemical device corresponding to the displacement. When the recorded pressure value jumps (decreases abruptly), it indicates that the electrochemical device has a fracture inside. At this time, the pressure value can be used to characterize the hardness of the electrochemical device.

[0111]

[0112] From the data in Table 1, it can be seen that compared with Comparative Examples 1-4, since Examples 1-4 satisfy θ1 / 2≤θ2≤(θ1 / 2+45°), the electrochemical devices of Examples 1-4 have higher hardness (i.e., deformation resistance) and improved capacity retention. Among them, since Example 4 further satisfies θ2=θ1, it has higher deformation resistance and capacity retention. Comparative Example 5 has the lowest cycle performance because the bonding layer of the isolation membrane is uniformly coated.

[0113] Further, by comparing Examples 1-6, it can be seen that when θ1 / 2≤θ2≤(θ1 / 2+45°) is satisfied, as θ3 increases, the anti-deformation ability and capacity retention rate of the electrochemical device show a trend of first increasing and then decreasing, and when θ3=180°-2θ2, the electrochemical device has higher anti-deformation ability and capacity retention rate. Therefore, the electrochemical device of Example 4 has higher anti-deformation ability and capacity retention rate.

[0114] Furthermore, by comparing Examples 4, 7-10, it can be seen that when θ3=180°-2θ2 is satisfied, as θ2 increases, the anti-deformation ability and capacity retention rate of the electrochemical device show a trend of first increasing and then decreasing, and when θ2=θ1, the electrochemical device has a higher anti-deformation ability and capacity retention rate. Therefore, the electrochemical device of Example 4 has a higher anti-deformation ability and capacity retention rate.

[0115] Moreover, when θ2=θ1 is satisfied, the specific value of θ1 can also be adjusted. Compared with Example 10, it can be seen that since Examples 11-12 satisfy θ2=θ1, the electrochemical device has higher anti-deformation ability and capacity retention rate.

[0116] Examples 13-26

[0117] The difference from Example 1 is that the values ​​of t1, d1 and d2 are further set, and the values ​​of t1, d1 or d2 in Examples 13-26 are different.

[0118] The electrochemical devices of each embodiment and comparative example were subjected to a capacity retention test and a three-point bending test, and the corresponding test results are recorded in Table 2.

[0119]

[0120] Among them, under the condition of satisfying θ1 / 2≤θ2≤(θ1 / 2+45°), the value of d2 will also affect the capacity retention rate of the electrochemical device. It can be seen from the data in Table 2 that compared with Examples 13-17, since d2>10mm in Example 18, the bonding force between the separator and the pole piece is relatively reduced, thereby relatively reducing the hardness (i.e., deformation resistance) of the electrochemical device, and the capacity retention rate is also relatively reduced.

[0121] Secondly, the value of d1 will also affect the capacity retention rate of the electrochemical device. Compared with Examples 16 and 19-21, since d1>10 mm in Example 22, the space available for electrolyte transmission is reduced, and the capacity retention rate is relatively reduced.

[0122] Again, the value of d1 / d2 will also affect the capacity retention rate of the electrochemical device. Comparing Examples 19, 20 and 22, since d1 / d2>5 in Example 21, the capacity retention rate of the electrochemical device is relatively reduced.

[0123] Finally, the value of t1d1 / (d1+d2) will also affect the capacity retention rate of the electrochemical device. Compared with Examples 19, 23-24, since t1d1 / (d1+d2)>2 in Examples 25-26, the capacity retention rate of the electrochemical device is relatively reduced.

[0124] The above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, a person skilled in the art should understand that the technical solution of the present application may be modified or replaced by equivalents.

Claims

1. An electrochemical device, comprising a housing, an electrode assembly and an electrolyte disposed in the housing, the electrode assembly comprising pole pieces and a separator disposed between adjacent pole pieces, wherein: The isolation film comprises a porous substrate and a first bonding layer disposed on the surface of the porous substrate, wherein the first bonding layer comprises a plurality of first bonding areas disposed at intervals. The thickness direction of the electrode assembly is defined as a first direction. In the first direction, a circumscribed rectangle of a projection of the electrode assembly has a diagonal line and a first side. The electrode assembly further comprises a pole ear electrically connected to the pole piece. In the first direction, a projection of the pole ear extends from an opposite side of the first side. An angle between the diagonal line and the first side is θ1. An angle between the projection of the first bonding area and the first side is θ2. θ1 / 2≤θ2≤(θ1 / 2+45°). The isolation film further comprises a second bonding layer, the porous substrate is located between the first bonding layer and the second bonding layer, and the second bonding layer comprises a plurality of second bonding areas arranged at intervals. In the first direction, an angle between a projection of the second bonding area and a projection of the first bonding area is θ3, 0°<θ3<180°; θ3=180°-2θ2.

2. The electrochemical device according to claim 1, wherein θ2=θ1.

3. The electrochemical device according to claim 1, wherein A direction from the first bonding area to another adjacent first bonding area is defined as a second direction. In the second direction, the width of the first bonding area is d1 mm, and the distance between adjacent first bonding areas is d2 mm. d1 and d2 satisfy at least one of the following conditions: 0.1 <d1<10,0.1<d2<10; 0.1 <d1 / d2<5。 4. The electrochemical device according to claim 3, wherein: In the first direction, the thickness of the first bonding layer is t1 μm, 0.15 <t1d1 / (d1+d2)<2。 5. The electrochemical device according to claim 1, wherein In the first direction, the thickness of the first adhesive layer is t1 μm, and 0.1≤t1≤6.

6. The electrochemical device according to claim 1, wherein The plurality of first bonding areas are parallel to each other.

7. The electrochemical device according to claim 1, wherein: Each of the first bonding areas is arranged continuously or discontinuously.

8. The electrochemical device according to claim 1, wherein In the first direction, the projection of the electrode assembly includes a rectangle, an arc or an L shape.

9. The electrochemical device according to claim 1, wherein: The electrode assembly includes a winding structure or a stacked structure.

10. The electrochemical device according to claim 1, wherein The porous substrate comprises a polymer film, a multilayer polymer film, or a nonwoven fabric formed by any one of the following polymers or a mixture of two or more thereof: at least one of polyolefin, polyvinylidene fluoride, polyethylene terephthalate, cellulose, polyimide, polyamide, spandex, or polyphenylene phthalamide.

11. The electrochemical device according to claim 1, wherein: The first bonding layer includes a bonding material, and the bonding material includes at least one of a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and trichloroethylene, polymethyl methacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, a copolymer of ethylene-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, a copolymer of acrylonitrile-styrene-butadiene, polyvinyl alcohol, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene, a copolymer of styrene-butadiene or polyvinylidene fluoride.

12. An electronic device comprising the electrochemical device according to any one of claims 1 to 11.

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